Aeronautical Terms

100-Hour Inspection

An inspection, identical in scope to an annual inspection. Must be conducted every 100 hours of flight on aircraft of under 12,500 pounds that are used for hire.

100-hour inspection

An inspection identical in scope to an annual inspection. Conducted every 100 hours of flight on aircraft of under 12,500 pounds that are used to carry passengers for hire.

14 CFR

Title 14 of the Code of Federal Regulations.

14 CFR part 121

The Federal regulations governing domestic, flag, and supplemental operations.

14 CFR part 135

The Federal regulations governing Commuter and On-Demand Operations.

14 CFR part 43

The Federal regulations governing Maintenance, Preventive Maintenance, Rebuilding, And Alteration

14 CFR Part 61

The Federal regulations governing Pilots, Flight Instructors, And Ground Instructors.

14 CFR Part 91

The Federal regulations governing General Operating And Flight Rules

14 CFR–Title 14 of the Code of Federal Regulations

The federal aviation regulations governing the operation of aircraft, airways, and airmen.

14 CFR–Title 14 of the Code of Federal Regulations

Includes the federal aviation regulations governing the operation of aircraft, airways, and airmen.

180 Degrees Autorotation

Initiated from a downwind heading and is commenced well inside the normal traffic pattern. “Go around” may not be possible during the latter part of this maneuver.

360 Overhead

Overhead Maneuver.

A-RNAV

Advanced Area Navigation

A.C.

Alternating Current.

A.C.

Alternating current.

A/FD

Airport/Facility Directory—obsolete. Changed to Chart Supplement.

A/FD

Airport/Facility Directory—obsolete. Changed to Chart Supplement.

AAI

Arrival Aircraft Interval

AAR

Airport Acceptance Rate or Airport Arrival Rate. The number of arrivals an airport is capable of accepting each hour.

AAS

Airport Advisory Service

AAWU

Alaskan Aviation Weather Unit

Abbreviated IFR Flight Plans

An authorization by ATC requiring pilots to submit only that information needed for the purpose of ATC. It includes only a small portion of the usual IFR flight plan information. In certain instances, this may be only aircraft identification, location, and pilot request. Other information may be requested if needed by ATC for separation/control purposes. It is frequently used by aircraft which are airborne and desire an instrument approach or by aircraft which are on the ground and desire a climb to VFR-on-top.

Abeam

An aircraft is “abeam” a fix, point, or object when that fix, point, or object is approximately 90 degrees to the right or left of the aircraft track. Abeam indicates a general position rather than a precise point.

Abeam Fix

A fix, NAVAID, point, or object positioned approximately 90 degrees to the right or left of the aircraft track along a route of flight. Abeam indicates a general position rather than a precise point.

Abort

To terminate a preplanned aircraft maneuver; e.g., an aborted takeoff.

Absolute accuracy

The ability to determine present position in space independently, and is most often used by pilots.

Absolute accuracy

The ability to determine present position in space independently, and is most often used by pilots.

Absolute Altitude

The vertical distance of an airplane above the terrain, or above ground level (AGL).

Absolute altitude

The actual distance between an aircraft and the terrain over which it is flying.

Absolute altitude

The actual distance between an aircraft and the terrain over which it is flying.

Absolute Ceiling

The altitude at which a climb is no longer possible.

Absolute instability

A state of a layer within the atmosphere in which the vertical distribution of temperature is such that an air parcel, if given an upward or downward push, wiII move away from its initial level without further outside force being applied.

Absolute pressure

Pressure measured from the reference of zero pressure, or a vacuum.

Absolute pressure

Pressure measured from the reference of zero pressure, or a vacuum.

Absolute temperature scale

Kelvin Temperature Scale. A temperature scale with zero degrees equal to the temperature at which all molecular motion ceases, i.e., absolute zero (0° K = -273° C); the Kelvin degree is identical to the Celsius degree; hence at standard sea level pressure, the melting point is 273° K and the boiling point 373° K.

Absolute vorticity

The rotation of the Earth imparts vorticity to the atmosphere; absolute vorticity is the combined vorticity due to this rotation and vorticity due to circulation relative to the Earth (relative vorticity).

Abstractions

Words that are general rather than specific. Aircraft is an abstraction; airplane is less abstract; jet is more specific; and jet airliner is still more specific.

AC

Advisory Circular

AC

Advisory Circular

AC, A/C or ACFT

Aircraft

ACAR

Aircraft Communications Addressing and Reporting System

ACARS

Aircraft Communications Addressing and Reporting System

ACAS

Airborne Collision Avoidance System

Accelerate-Go Distance

The distance required to accelerate to V1 with all engines at takeoff power, experience an engine failure at V1, and continue the takeoff on the remaining engine(s). The runway required includes the distance required to climb to 35 feet by which time V2 speed must be attained.

Accelerate-Stop Distance

The distance required to accelerate to V1 with all engines at takeoff power, experience an engine failure at V1, and abort the takeoff and bring the airplane to a stop using braking action only (use of thrust reversing is not considered).

Accelerate-Stop Distance Available

The runway plus stopway length declared available and suitable for the acceleration and deceleration of an airplane aborting a takeoff.

Accelerate-Stop Distance Available (ASDA)

The runway plus stopway length declared available and suitable for the acceleration and deceleration of an airplane aborting a takeoff.

Accelerate-Stop Distance Available [ICAO]

The length of the take-off run available plus the length of the stopway if provided.

Acceleration

Force involved in overcoming inertia, and which may be defined as a change in velocity per unit of time.

Acceleration

Force involved in overcoming inertia, and which may be defined as a change in velocity per unit of time.

Acceleration error

A magnetic compass error apparent when the aircraft accelerates while flying on an easterly or westerly heading, causing the compass card to rotate toward North.

Acceleration error

A magnetic compass error apparent when the aircraft accelerates while flying on an easterly or westerly heading, causing the compass card to rotate toward North.

Accelerometer

A part of an inertial navigation system (INS) that accurately measures the force of acceleration in one direction.

Accelerometer

A part of an inertial navigation system (INS) that accurately measures the force of acceleration in one direction.

Accessories

Components that are used with an engine, but are not a part of the engine itself. Units such as magnetos, carburetors, generators, and fuel pumps are commonly installed engine accessories.

Acknowledge

Let me know that you have received my message.

ACL

Aircraft List

ACLS

Automatic Carrier Landing System

Acrobatic Flight

An intentional maneuver involving an abrupt change in an aircraft’s attitude, an abnormal attitude, or abnormal acceleration not necessary for normal flight. (Refer to 14 CFR Part 91.

Active Runway

Runway In Use/Active Runway/Duty Runway.

Actual Calculated Landing Time

ACLT is a flight’s frozen calculated landing time. An actual time determined at freeze calculated landing time (FCLT) or meter list display interval (MLDI) for the adapted vertex for each arrival aircraft based upon runway configuration, airport acceptance rate, airport arrival delay period, and other metered arrival aircraft. This time is either the vertex time of arrival (VTA) of the aircraft or the tentative calculated landing time (TCLT)/ACLT of the previous aircraft plus the arrival aircraft interval (AAI), whichever is later. This time will not be updated in response to the aircraft’s progress.

Actual Navigation Performance (ANP)

A measure of the current estimated navigational performance. Also referred to as Estimated Position Error (EPE).

Airworthiness Directive

ADC

Air Data Computer.

ADCUS

Advise Customs

Additional Services

Advisory information provided by ATC which includes but is not limited to the following: a. Traffic advisories. b. Vectors, when requested by the pilot, to assist aircraft receiving traffic advisories to avoid observed traffic. c. Altitude deviation information of 300 feet or more from an assigned altitude as observed on a verified (reading correctly) automatic altitude readout (Mode C). d. Advisories that traffic is no longer a factor. e. Weather and chaff information. f. Weather assistance. g. Bird activity information. h. Holding pattern surveillance. Additional services are provided to the extent possible contingent only upon the controller’s capability to fit them into the performance of higher priority duties and on the basis of limitations of the radar, volume of traffic, frequency congestion, and controller workload. The controller has complete discretion for determining if he/she is able to provide or continue to provide a service in a particular case. The controller’s reason not to provide or continue to provide a service in a particular case is not subject to question by the pilot and need not be made known to him/her.

ADDS

Aviation Digital Data Service

ADF

Automatic Direction Finder.

ADF

Automatic Direction Finder.

ADI

Attitude Director Indicator.

ADI

Attitude Director Indicator.

Adiabatic cooling

A process of cooling the air through expansion. For example, as air moves up slope it expands with the reduction of atmospheric pressure and cools as it expands.

Adiabatic Cooling

A process by which a parcel of air cools. When a parcel of air is lifted, pressure is reduced due to the elevation increase. This reduction in pressure causes the parcel of air to expand in volume and, in turn, the parcel cools to maintain an energy balance because no energy is added to the parcel.

Adiabatic heating

A process of heating dry air through compression. For example, as air moves down a slope it is compressed, which results in an increase in temperature.

Adiabatic process

The process by which fixed relationships are maintained during changes in temperature, volume, and pressure in a body of air without heat being added or removed from the body.

ADIZ

Air Defense Identification Zone

Adjustable Stabilizer

A stabilizer that can be adjusted in flight to trim the airplane, thereby allowing the airplane to fly hands-off at any given airspeed.

Adjustable-pitch propeller

A propeller with blades whose pitch can be adjusted on the ground with the engine not running, but which cannot be adjusted in flight. Also referred to as a ground adjustable propeller. Sometimes also used to refer to constant-speed propellers that are adjustable in flight.

ADM

Aeronautical Decision-Making.

ADM

Aeronautical Decision-Making

Administrator

The Federal Aviation Administrator or any person to whom he has delegated his authority in the matter concerned.

Automatic Dependent Surveillance

ADS-B

Automatic Dependent Surveillance-Broadcast.

ADSB

Automatic Dependent Surveillance Broadcast.

Advection

The horizontal transport of air or atmospheric properties. In meteorology, sometimes referred to as the horizontal component of convection.

Advection fog

Fog resulting from the transport of warm, humid air over a cold surface.

Adverse Loaded CG Check

A weight and balance check to determine that no condition of legal loading of an aircraft can move the CG outside of its allowable limits.

Adverse Yaw

A condition of flight in which the nose of an airplane tends to yaw toward the outside of the turn. This is caused by the higher induced drag on the outside wing, which is also producing more lift. Induced drag is a by-product of the lift associated with the outside wing.

Adverse yaw

A flight condition at the beginning of a turn in which the nose of the aircraft starts to move in the direction opposite the direction the turn is being made, caused by the induced drag produced by the downward-deflected aileron holding back the wing as it begins to rise.

Adverse yaw

Advise Intentions

Tell me what you plan to do.

Advisory

Advice and information provided to assist pilots in the safe conduct of flight and aircraft movement.

Advisory Frequency

The appropriate frequency to be used for Airport Advisory Service.

Advisory Service

Advice and information provided by a facility to assist pilots in the safe conduct of flight and aircraft movement.

ADZY or ADVZY

Advisory

AER

Approach End of Runway

Aerial Refueling

A procedure used by the military to transfer fuel from one aircraft to another during flight.

Aerodrome

A defined area on land or water (including any buildings, installations and equipment) intended to be used either wholly or in part for the arrival, departure, and movement of aircraft.

Aerodrome Beacon [ICAO]

Aeronautical beacon used to indicate the location of an aerodrome from the air.

Aerodrome Control Service [ICAO]

Air traffic control service for aerodrome traffic.

Aerodrome Control Tower [ICAO]

A unit established to provide air traffic control service to aerodrome traffic.

Aerodrome Elevation [ICAO]

The elevation of the highest point of the landing area.

Aerodrome Traffic Circuit [ICAO]

The specified path to be flown by aircraft operating in the vicinity of an aerodrome.

Aerodynamic Ceiling

The point (altitude) at which, as the indicated airspeed decreases with altitude, it progressively merges with the low speed buffet boundary where pre-stall buffet occurs for the airplane at a load factor of 1.0 G.

Aerodynamic coefficients

Non-dimensional coefficients for aerodynamic forces and moments.

Aerodynamics

The science of the action of air on an object, and with the motion of air on other gases. Aerodynamics deals with the production of lift by the aircraft, the relative wind, and the atmosphere.

Aerodynamics

The science of the action of air on an object, and with the motion of air on other gases. Aerodynamics deals with the production of lift by the aircraft, the relative wind, and the atmosphere.

Aeronautical Beacon

A visual NAVAID displaying flashes of white and/or colored light to indicate the location of an airport, a heliport, a landmark, a certain point of a Federal airway in mountainous terrain, or an obstruction.

Aeronautical Chart

A map used in air navigation containing all or part of the following: topographic features, hazards and obstructions, navigation aids, navigation routes, designated airspace, and airports. Commonly used aeronautical charts are: Sectional Aeronautical Charts, VFR Terminal Area Charts, World Aeronautical Charts (WAC), En Route Low Altitude Charts, En Route High Altitude Charts, Instrument Approach Procedures (IAP) Charts, Instrument Departure Procedure (DP) Charts, Standard Terminal Arrival (STAR) Charts.

Aeronautical decision-making (ADM)

A systematic approach to the mental process used by pilots to consistently determine the best course of action in response to a given set of circumstances.

Aeronautical decision-making (ADM)

A systematic approach to the mental process used by aircraft pilots to consistently determine the best course of action in response to a given set of circumstances.

Aeronautical decision-making (ADM)

A systematic approach to the mental process used by pilots to consistently determine the best course of action in response to a given set of circumstances.

AFCS

Automatic Flight Control System

Affective domain

A grouping of levels of learning associated with a person’s attitudes, personal beliefs, and values which range from receiving through responding, valuing, and organization to characterization.

Affirmative

Yes.

AFIS

Automatic Flight Information Service

AFM

Airplane Flight Manual or Aircraft Flight Manual

AFM

Airplane Flight Manual.

AFM

Aircraft Flight Manual

AFP

An AFP is a traffic management (TM) process administered by the ATCSCC. Aircraft are assigned specific airspace arrival slots utilizing flight schedule monitor (FSM) to manage capacity and demand for a specific area of the National Airspace System (NAS). AFPs support the TM mission and mitigate the effects of en route constraints. Please see the AFP Advisory circular for more details.

AFSS

Automated Flight Service Station

AFSS

Automated Flight Service Station

AGL

Above Ground Level

AGL

Above Ground Level

AGL Altitude

Altitude expressed in feet measured above ground level.

Agonic line

An irregular imaginary line across the surface of the Earth along which the magnetic and geographic poles are in alignment, and along which there is no magnetic variation.

Agonic line

An irregular imaginary line across the surface of the Earth along which the magnetic and geographic poles are in alignment, and along which there is no magnetic variation.

AHRS

Attitude Heading Reference System

Ailerons

Primary flight control surfaces mounted on the trailing edge of an airplane wing, near the tip. Ailerons control roll about the longitudinal axis.

Ailerons

Primary flight control surfaces mounted on the trailing edge of an airplane wing, near the tip. Ailerons control roll about the longitudinal axis.

AIM

Aeronautical Information Manual

AIM

Aeronautical Information Manual

AIP

Aeronautical Information Publication

Air carrier

A person who undertakes directly by lease, or other arrangement, to engage in air transportation.

Air Carrier District Office

An FAA field office serving an assigned geographical area, staffed with Flight Standards personnel serving the aviation industry and the general public on matters related to the certification and operation of scheduled air carriers and other large aircraft operations.

Air commerce

Interstate, overseas, or foreign air commerce or the transportation of mail by aircraft or any operation or navigation of aircraft within the limits of any Federal airway or any operation or navigation of aircraft which directly affects, or which may endanger safety in, interstate, overseas, or foreign air commerce.

Air data computer (ADC)

An aircraft computer that receives and processes pitot pressure, static pressure, and temperature to calculate very precise altitude, indicated airspeed, true airspeed, and air temperature.

Air data computer (ADC)

An aircraft computer that receives and processes pitot pressure, static pressure, and temperature to calculate very precise altitude, indicated airspeed, true airspeed, and air temperature.

Air Defense Emergency

A military emergency condition declared by a designated authority. This condition exists when an attack upon the continental U.S., Alaska, Canada, or U.S. installations in Greenland by hostile aircraft or missiles is considered probable, is imminent, or is taking place.

Air Defense Identification Zone (ADIZ)

The area of airspace over land or water, extending upward from the surface, within which the ready identification, the location, and the control of aircraft are required in the interest of national security.

Air density

The mass density of the air in terms of weight per unit volume.

Air mass

In meteorology, an extensive body of air within which the conditions of temperature and moisture in a horizontal plane are essentially uniform.

Air mass classification

A system used to identify and to characterize the different air masses according to a basic scheme. The system most commonly used classifies air masses primarily according to the thermal properties of their source regions: “tropical” (T); “polar” (P); and “Arctic” or “Antarctic” (A). They are further classified according to moisture characteristics as “continental” (c) or “maritime” (m).

Air Navigation Facility

Any facility used in, available for use in, or designed for use in, aid of air navigation, including landing areas, lights, any apparatus or equipment for disseminating weather information, for signaling, for radio-directional finding, or for radio or other electrical communication, and any other structure or mechanism having a similar purpose for guiding or controlling flight in the air or the landing and takeoff of aircraft.

Air parcel

A. small volume of air, small enough to contain uniform distribution of its meteorological properties, and large enough to remain relatively self-contained and respond to all meteorological processes. No specific dimensions have been defined, however, the order of magnitude of 1 cubic foot has been suggested.

Air Route Surveillance Radar

Air route traffic control center (ARTCC) radar used primarily to detect and display an aircraft’s position while en route between terminal areas. The ARSR enables controllers to provide radar air traffic control service when aircraft are within the ARSR coverage. In some instances, ARSR may enable an ARTCC to provide terminal radar services similar to but usually more limited than those provided by a radar approach control.

Air route surveillance radar (ARSR)

Air route traffic control center (ARTCC) radar used primarily to detect and display an aircrafts position while en route between terminal areas.

Air Route Traffic Control Center

A facility established to provide air traffic control service to aircraft operating on IFR flight plans within controlled airspace and principally during the en route phase of flight. When equipment capabilities and controller workload permit, certain advisory/assistance services may be provided to VFR aircraft.

Air Route Traffic Control Center (ARTCC)

A facility established to provide air traffic control service to aircraft operating on IFR flight plans within controlled airspace and principally during the en route phase of flight

Air route traffic control center (ARTCC)

Provides ATC service to aircraft operating on IFR flight plans within controlled airspace and principally during the en route phase of flight.

Air Start

The act or instance of starting an aircraft’s engine while in flight, especially a jet engine after flameout.

Air Taxi

Used to describe a helicopter/VTOL aircraft movement conducted above the surface but normally not above 100 feet AGL. The aircraft may proceed either via hover taxi or flight at speeds more than 20 knots. The pilot is solely responsible for selecting a safe airspeed/altitude for the operation being conducted.

Air Traffic

Aircraft operating in the air or on an airport surface, exclusive of loading ramps and parking areas.

Air Traffic Clearance

An authorization by air traffic control for the purpose of preventing collision between known aircraft, for an aircraft to proceed under specified traffic conditions within controlled airspace. The pilot-in-command of an aircraft may not deviate from the provisions of a visual flight rules (VFR) or instrument flight rules (IFR) air traffic clearance except in an emergency or unless an amended clearance has been obtained. Additionally, the pilot may request a different clearance from that which has been issued by air traffic control (ATC) if information available to the pilot makes another course of action more practicable or if aircraft equipment limitations or company procedures forbid compliance with the clearance issued. Pilots may also request clarification or amendment, as appropriate, any time a clearance is not fully understood, or considered unacceptable because of safety of flight. Controllers should, in such instances and to the extent of operational practicality and safety, honor the pilot’s request. 14 CFR Part 91.3(a) states: “The pilot in command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft.” the pilot is responsible to request an amended clearance, if ATC issues a clearance that would cause a pilot to deviate from a rule or regulation, or in the pilot’s opinion, would place the aircraft in jeopardy.

Air Traffic Control

A service operated by appropriate authority to promote the safe, orderly and expeditious flow of air traffic.

Air traffic control (ATC)

A service provided by the FAA to promote the safe, orderly, and expeditious flow of air traffic.

Air Traffic Control Clearance [ICAO]

Authorization for an aircraft to proceed under conditions specified by an air traffic control unit. Note 1: For convenience, the term air traffic control clearance is frequently abbreviated to clearance when used in appropriate contexts. Note 2: The abbreviated term clearance may be prefixed by the words taxi, takeoff, departure, en route, approach or landing to indicate the particular portion of flight to which the air traffic control clearance relates.

Air traffic control radar beacon system (ATCRBS)

Sometimes called secondary surveillance radar (SSR), which utilizes a transponder in the aircraft. The ground equipment is an interrogating unit, in which the beacon antenna is mounted so it rotates with the surveillance antenna. The interrogating unit transmits a coded pulse sequence that actuates the aircraft transponder. The transponder answers the coded sequence by transmitting a preselected coded sequence back to the ground equipment, providing a strong return signal and positive aircraft identification, as well as other special data.

Air traffic control radar beacon system (ATCRBS).

Air Traffic Control Service [ICAO]

A service provided for the purpose of: a. Preventing collisions: 1. Between aircraft; and 2. On the maneuvering area between aircraft and obstructions. b. Expediting and maintaining an orderly flow of air traffic.

Air Traffic Control Specialist

A person authorized to provide air traffic control service.

Air Traffic Control System Command Center

An Air Traffic Tactical Operations facility responsible for monitoring and managing the flow of air traffic throughout the NAS, producing a safe, orderly, and expeditious flow of traffic while minimizing delays. The following functions are located at the ATCSCC: a. Central Altitude Reservation Function (CARF). Responsible for coordinating, planning, and approving special user requirements under the Altitude Reservation (ALTRV) concept. b. Airport Reservation Office (ARO). Responsible for approving IFR flights at designated high density traffic airports (John F. Kennedy, LaGuardia, and Ronald Reagan Washington National) during specified hours. c. U.S. Notice to Airmen (NOTAM) Office. Responsible for collecting, maintaining, and distributing NOTAMs for the U.S. civilian and military, as well as international aviation communities. d. Weather Unit. Monitor all aspects of weather for the U.S. that might affect aviation including cloud cover, visibility, winds, precipitation, thunderstorms, icing, turbulence, and more. Provide forecasts based on observations and on discussions with meteorologists from various National Weather Service offices, FAA facilities, airlines, and private weather services.

Air Traffic Service

A generic term meaning: a. Flight Information Service. b. Alerting Service. c. Air Traffic Advisory Service. d. Air Traffic Control Service: 1. Area Control Service, 2. Approach Control Service, or 3. Airport Control Service.

Air Traffic Service (ATS)

Air traffic service is an ICAO generic term meaning variously, flight information service, alerting service, air traffic advisory service, air traffic control service (area control service, approach control service, or aerodrome control service).

Air Traffic Service (ATS) route

A specified route designated for channeling the flow of traffic as necessary for the provision of air traffic services. The term “ATS route” refers to a variety of airways, including jet routes, area navigation (RNAV) routes, and arrival and departure routes. An ATS route is defined by route specifications, which may include:
(1) An ATS route designator;
(2) The path to or from significant points;
(3) Distance between significant points;
(4) Reporting requirements; and
(5) The lowest safe altitude determined by the appropriate authority.

Air Traffic Service (ATS) Routes

The term “ATS Route” is a generic term that includes “VOR Federal airways,” “colored Federal airways,” “jet routes,” and “RNAV routes.” The term “ATS route” does not replace these more familiar route names, but serves only as an overall title when listing the types of routes that comprise the United States route structure.

Air Traffic [ICAO]

All aircraft in flight or operating on the maneuvering area of an aerodrome.

Air transportation

Interstate, overseas, or foreign air transportation or the transportation of mail by aircraft.

Airborne

An aircraft is considered airborne when all parts of the aircraft are off the ground.

Airborne Delay

Amount of delay to be encountered in airborne holding.

Aircraft

A device that is used or intended to be used for flight in the air.

Aircraft

A device that is used, or intended to be used, for flight.

Aircraft altitude

The actual height above sea level at which the aircraft is flying.

Aircraft Approach Category

A grouping of aircraft based on a speed of 1.3 times the stall speed in the landing configuration at maximum gross landing weight. An aircraft must fit in only one category. If it is necessary to maneuver at speeds in excess of the upper limit of a speed range for a category, the minimums for the category for that speed must be used. For example, an aircraft which falls in Category A, but is circling to land at a speed in excess of 91 knots, must use the approach Category B minimums when circling to land. The categories are A-E.

Aircraft checkouts

An instructional program designed to familiarize and qualify a pilot to act as pilot in command of a particular aircraft type.

Aircraft Classes

AIRCRAFT CLASSES- For the purposes of Wake Turbulence Separation Minima, ATC classifies aircraft as Super, Heavy, Large, and Small as follows:
a. Super. The Airbus A-380-800 (A388) and the Antonov An-225 (A225) are classified as super.
b. Heavy- Aircraft capable of takeoff weights of 300,000 pounds or more whether or not they are operating at this weight during a particular phase of flight.
c, Large- Aircraft of more than 41,000 pounds, maximum certificated takeoff weight, up to but not including 300,000 pounds.
d. Small- Aircraft of 41,000 pounds or less maximum certificated takeoff weight.

Aircraft Conflict

Predicted conflict, within URET, of two aircraft, or between aircraft and airspace. A Red alert is used for conflicts when the predicted minimum separation is 5 nautical miles or less. A Yellow alert is used when the predicted minimum separation is between 5 and approximately 12 nautical miles. A Blue alert is used for conflicts between an aircraft and predefined airspace.

Aircraft Conflict Alert

A safety alert issued by ATC to aircraft under their control if ATC is aware of an aircraft that is not under their control at an altitude which, in the controller’s judgment, places both aircraft in unsafe proximity to each other. With the alert, ATC will offer the pilot an alternate course of action when feasible; e.g., “Traffic Alert, advise you turn right heading zero niner zero or climb to eight thousand immediately.”

Aircraft engine

An engine that is used or intended to be used for propelling aircraft. It includes turbosuperchargers, appurtenances, and accessories necessary for its functioning, but does not include propellers.

Aircraft Logbooks

Journals containing a record of total operating time, repairs, alterations or inspections performed, and all Airworthiness Directive (AD) notes complied with. A maintenance logbook should be kept for the airframe, each engine, and each propeller.

Aircraft Specifications

Documentation containing the pertinent specifications for aircraft certificated under the CARs.

Airfoil

An airfoil is any surface, such as a wing, propeller, rudder, or even a trim tab, which provides aerodynamic force when it interacts with a moving stream of air.

Airfoil

Any surface, such as a wing, propeller, rudder, or even a trim tab, which provides aerodynamic force when it interacts with a moving stream of air.

Airframe

The fuselage, booms, nacelles, cowlings, fairings, airfoil surfaces (including rotors but excluding propellers and rotating airfoils of engines), and landing gear of an aircraft and their accessories and controls.

Airmanship

A sound acquaintance with the principles of flight, the ability to operate an airplane with competence and precision both on the ground and in the air, and the exercise of sound judgment that results in optimal operational safety and efficiency.

Airmanship Skills

The skills of coordination, timing, control touch, and speed sense in addition to the motor skills required to fly an aircraft.

Airmen’s Meteorological Information

AIRMET.

Airmen’s Meteorological Information (AIRMET)

In-flight weather advisories concerning weather phenomena of operational interest to all pilots and especially to pilots of aircraft not approved for flight in icing conditions. An AIRMET concerns weather of lesser severity than that covered by an advisory of significant meteorological information (SIGMET) or a convective SIGMET. AIRMETs may include advisories of moderate icing.

AIRMET

Inflight weather advisory issued as an amendment to the area forecast, concerning weather phenomena of operational interest to all aircraft and that is potentially hazardous to aircraft with limited capability due to lack of equipment, instrumentation, or pilot qualifications.

AIRMET

Airmen’s Meteorological Information

AIRMET

In-flight weather advisories issued only to amend the area forecast concerning weather phenomena which are of operational interest to all aircraft and potentially hazardous to aircraft having limited capability because of lack of equipment, instrumentation, or pilot qualifications. AIRMETs concern weather of less severity than that covered by SIGMETs or Convective SIGMETs. AIRMETs cover moderate icing, moderate turbulence, sustained winds of 30 knots or more at the surface, widespread areas of ceilings less than 1,000 feet and/or visibility less than 3 miles, and extensive mountain obscurement.

Airplane

An engine-driven fixed-wing aircraft heavier than air, that is supported in flight by the dynamic reaction of the air against its wings.

Airplane

An engine-driven, fixed-wing aircraft heavier than air that is supported in flight by the dynamic reaction of air against its wings.

Airplane Flight Manual (AFM)

A document developed by the airplane manufacturer and approved by the Federal Aviation Administration (FAA). It is specific to a particular make and model airplane by serial number and it contains operating procedures and limitations.

Airplane Flight Manual (AFM)

Airplane Owner/ Information Manual

A document developed by the airplane manufacturer containing general information about the make and model of an airplane. The airplane owner’s manual is not FAA-approved and is not specific to a particular serial numbered airplane. This manual is not kept current, and therefore cannot be substituted for the AFM/POH.

Airplane Owner/Information Manual

A document developed by the airplane manufacturer containing general information about the make and model of an airplane. The airplane owner’s manual is not FAA approved and is not specific to a particular serial numbered airplane. This manual is not kept current, and therefore cannot be substituted for the AFM/POH.

Airport

An area of land or water that is used or intended to be used for the landing and takeoff of aircraft, and includes its buildings and facilities, if any.

Airport Arrival Rate (AAR)

A dynamic input parameter specifying the number of arriving aircraft which an airport or airspace can accept from the ARTCC per hour. The AAR is used to calculate the desired interval between successive arrival aircraft.

Airport Departure Rate (ADR)

A dynamic parameter specifying the number of aircraft which can depart an airport and the airspace can accept per hour.

Airport Diagram

A full-page depiction of the airport that includes the same features of the airport sketch plus additional details such as taxiway identifiers, airport latitude and longitude, and building identification. Airport diagrams are located in the U.S. Terminal Procedures booklet following the instrument approach charts for a particular airport.

Airport Elevation

The highest point of an airport’s usable runways measured in feet from mean sea level.

Airport Lighting

Various lighting aids that may be installed on an airport.

Airport Marking Aids

Markings used on runway and taxiway surfaces to identify a specific runway, a runway threshold, a centerline, a hold line, etc. A runway should be marked in accordance with its present usage such as: a. Visual. b. Nonprecision instrument. c. Precision instrument.

Airport Reference Point (ARP)

The approximate geometric center of all usable runway surfaces.

Airport Reservation Office

Office responsible for monitoring the operation of slot controlled airports. It receives and processes requests for unscheduled operations at slot controlled airports.

Airport Rotating Beacon

A visual NAVAID operated at many airports. At civil airports, alternating white and green flashes indicate the location of the airport. At military airports, the beacons flash alternately white and green, but are differentiated from civil beacons by dualpeaked (two quick) white flashes between the green flashes.

Airport Sketch

Depicts the runways and their length, width, and slope, the touchdown zone elevation, the lighting system installed on the end of the runway, and taxiways. Airport sketches are located on the lower left or right portion of the instrument approach chart.

Airport surface detection equipment (ASDE)

Radar equipment specifically designed to detect all principal features and traffic on the surface of an airport, presenting the entire image on the control tower console; used to augment visual observation by tower personnel of aircraft and/or vehicular movements on runways and taxiways.

Airport Surface Detection Equipment (ASDE)

Surveillance equipment specifically designed to detect aircraft, vehicular traffic, and other objects, on the surface of an airport, and to present the image on a tower display. Used to augment visual observation by tower personnel of aircraft and/or vehicular movements on runways and taxiways. There are three ASDE systems deployed in the NAS: a. ASDE-3 a Surface Movement Radar. b. ASDE-X a system that uses a X-band Surface Movement Radar and multilateration. Data from these two sources are fused and presented on a digital display. c. ASDE-3X an ASDE-X system that uses the ASDE-3 Surface Movement Radar.

Airport Surveillance Radar

Approach control radar used to detect and display an aircraft’s position in the terminal area. ASR provides range and azimuth information but does not provide elevation data. Coverage of the ASR can extend up to 60 miles.

Airport surveillance radar (ASR)

Approach control radar used to detect and display an aircrafts position in the terminal area.

Airport surveillance radar approach

An instrument approach in which ATC issues instructions for pilot compliance based on aircraft position in relation to the final approach course and the distance from the end of the runway as displayed on the controllers radar scope.

Airport Taxi Charts

Aeronautical Chart.

Airport Traffic Control Service

A service provided by a control tower for aircraft operating on the movement area and in the vicinity of an airport.

Airport Traffic Control Tower

Tower.

Airport/Facility Directory

A publication designed primarily as a pilot’s operational manual containing all airports, seaplane bases, and heliports open to the public including communications data, navigational facilities, and certain special notices and procedures. This publication is issued in seven volumes according to geographical area. (Renamed to Chart Supplement)

Airport/Facility Directory (A/FD)

Regional booklets published by the National Aeronautical Charting Office. Title changed to Chart Supplement. (NACO) that provide textual information about all airports, both VFR and IFR. The A/FD includes runway length and width, runway surface, load bearing capacity, runway slope, airport services, and hazards such as birds and reduced visibility.

Airship

An engine-driven lighter-than-air aircraft that can be steered.

Airspace Hierarchy

Within the airspace classes, there is a hierarchy and, in the event of an overlap of airspace: Class A preempts Class B, Class B preempts Class C, Class C preempts Class D, Class D preempts Class E, and Class E preempts Class G.

Airspeed

The speed of an aircraft relative to its surrounding air mass. The unqualified term “airspeed” means one of the following: Indicated Airspeed, True Airspeed.

Airspeed indicator

A differential pressure gauge that measures the dynamic pressure of the air through which the aircraft is flying. Displays the crafts airspeed, typically in knots, to the pilot.

Airspeed indicator

A differential pressure gauge that measures the dynamic pressure of the air through which the aircraft is flying. Displays the craft’s airspeed, typically in knots, to the pilot.

Airstart

The starting of an aircraft engine while the aircraft is airborne, preceded by engine shutdown during training flights or by actual engine failure.

Airway

An airway is based on a centerline that extends from one navigation aid or intersection to another navigation aid (or through several navigation aids or intersections); used to establish a known route for en route procedures between terminal areas.

Airway

Airway Beacon

Used to mark airway segments in remote mountain areas. The light flashes Morse Code to identify the beacon site.

Airworthiness

A condition in which the aircraft conforms to its type certificated design including supplemental type certificates, and field approved alterations. The aircraft must also be in a condition for safe flight as determined by annual, 100 hour, preflight and any other required inspections.

Airworthiness Certificate

A certificate issued by the FAA to all aircraft that have been proven to meet the minimum standards set down by the Code of Federal Regulations.

Airworthiness Certificate

A certificate issued by the FAA to all aircraft that have been proven to meet the minimum standards set down by the Code of Federal Regulations.

Airworthiness Directive

A regulatory notice sent out by the FAA to the registered owner of an aircraft informing the owner of a condition that prevents the aircraft from continuing to meet its conditions for airworthiness. Airworthiness Directives (AD notes) must be complied with within the required time limit, and the fact of compliance, the date of compliance, and the method of compliance must be recorded in the aircraft’s maintenance records.

Airworthiness Directive

A regulatory notice sent out by the FAA to the registered owner of an aircraft informing the owner of a condition that prevents the aircraft from continuing to meet its conditions for airworthiness. Airworthiness Directives (AD notes) are to be complied with within the required time limit, and the fact of compliance, the date of compliance, and the method of compliance are recorded in the aircraft’s maintenance records.

AIS

Airmen’s Information System

ALAR

Approach and Landing Accident Reduction

Albedo

The ratio of the amount of electromagnetic radiation reflected by a body to the amount incident upon it, commonly expressed in percentage; in meteorology, usually used in reference to insolation (solar radiation); i.e., the albedo of wet sand is 9, meaning that about 9% of the incident insolation is reflected; albedoes of other surfaces range upward to 80-85 for fresh snow cover; average albedo for the earth and its atmosphere has been calculated to range from 35 to 43.

ALD

Available Landing Distance

Alert

An actual situation involving two real safety logic tracks (aircraft/aircraft, aircraft/vehicle, or aircraft/other tangible object) that safety logic has predicted will result in an imminent collision, based upon the current set of Safety Logic parameters.

Alert area

An area in which there is a high volume of pilot training or an unusual type of aeronautical activity.

Alert Area

Airspace which may contain a high volume of pilot training activities or an unusual type of aerial activity, neither of which is hazardous to aircraft. Alert Areas are depicted on aeronautical charts for the information of nonparticipating pilots. All activities within an Alert Area are conducted in accordance with Federal Aviation Regulations, and pilots of participating aircraft as well as pilots transiting the area are equally responsible for collision avoidance.

Almanac data

Information the global positioning system (GPS) receiver can obtain from one satellite which describes the approximate orbital positioning of all satellites in the constellation. This information is necessary for the GPS receiver to know what satellites to look for in the sky at a given time.

Almanac data

Along-Track Distance (ATD)

The distance measured from a point-in-space by systems using area navigation reference capabilities that are not subject to slant range errors.

Alpha Mode Of Operation

The operation of a turboprop engine that includes all of the flight operations, from takeoff to landing. Alpha operation is typically between 95 percent to 100 percent of the engine operating speed.

Alphanumeric Display

Letters and numerals used to show identification, altitude, beacon code, and other information concerning a target on a radar display.

ALS

Approach Lighting System.

ALSF-1

Approach Light System With Sequenced Flashing Lights In ILS CAT-I Configuration

ALSF-2

Approach Light System With Sequenced Flashing Lights In ILS Cat-II Configuration. The ALSF-2 May Operate As An SSALR When Weather Conditions Permit

Alternate Aerodrome [ICAO]

An aerodrome to which an aircraft may proceed when it becomes either impossible or inadvisable to proceed to or to land at the aerodrome of intended landing. Note: The aerodrome from which a flight departs may also be an en-route or a destination alternate aerodrome for the flight.

Alternate Air

A device which opens, either automatically or manually, to allow induction airflow to continue should the primary induction air opening become blocked.

Alternate airport

An airport designated in an IFR flight plan, providing a suitable destination if a landing at the intended airport becomes inadvisable.

Alternate Static Source

A manual port that when opened allows the pitot static instruments to sense static pressure from an alternate location should the primary static port become blocked.

Alternate static source valve

A valve in the instrument static air system that supplies reference air pressure to the altimeter, airspeed indicator, and vertical speed indicator if the normal static pickup should become clogged or iced over.

Alternate static source valve

Alternator/Generator

A device that uses engine power to generate electrical power.

Altimeter

A flight instrument that indicates altitude by sensing pressure changes.

Altimeter

An instrument which determines the altitude of an object with respect to a fixed level. A pressure altimeter.

Altimeter

A flight instrument that indicates altitude by sensing pressure changes.

Altimeter setting

Station pressure (the barometric pressure at the location the reading is taken) which has been corrected for the height of the station above sea level.

Altimeter setting

The value to which the scale of a pressure altimeter is set so as to read true altitude at field elevation.

Altimeter setting

Station pressure (the barometric pressure at the location the reading is taken) which has been corrected for the height of the station above sea level.

Altimeter setting indicator

A precision aneroid barometer calibrated to indicate directly the altimeter setting.

Altitude

The height of a level, point, or object measured in feet Above Ground Level (AGL) or from Mean Sea Level (MSL).

Altitude (AGL)

The actual height above ground level (AGL) at which the aircraft is flying.

Altitude (MSL)

The actual height above mean sea level (MSL) at which the aircraft is flying.

Altitude Chamber

A device that simulates high altitude conditions by reducing the interior pressure. The occupants will suffer from the same physiological conditions as flight at high altitude in an unpressurized aircraft.

Altitude Engine

A reciprocating aircraft engine having a rated takeoff power that is producible from sea level to an established higher altitude.

Altitude engine

A reciprocating aircraft engine having a rated takeoff power that is producible from sea level to an established higher altitude.

Altitude Readout

An aircraft’s altitude, transmitted via the Mode C transponder feature, that is visually displayed in 100-foot increments on a radar scope having readout capability.

Altitude Restriction

An altitude or altitudes, stated in the order flown, which are to be maintained until reaching a specific point or time. Altitude restrictions may be issued by ATC due to traffic, terrain, or other airspace considerations.

Altitude Restrictions Are Canceled

Adherence to previously imposed altitude restrictions is no longer required during a climb or descent.

Altocumulus

White or gray layers or patches of cloud, often with a waved appearance; cloud elements appear as rounded masses or rolls; composed mostly of liquid water droplets which may be supercooled; may contain ice crystals at subfreezing temperatures.

Altocumulus castellanus

A species of middle cloud of which at least a fraction of its upper part presents some vertically developed, cumuliform protuberances (some of which are taller than they are wide, as castles) and which give the cloud a crenelated or turreted appearance; especially evident when seen from the side; elements usually have a common base arranged in lines. This cloud indicates instability and turbulence at the altitudes of occurrence.

AMASS

Airport Movement Area Safety System

Amateur rocket

An unmanned rocket that:
(1) Is propelled by a motor or motors having a combined total impulse of 889,600 Newton-seconds (200,000 pound-seconds) or less; and
(2) Cannot reach an altitude greater than 150 kilometers (93.2 statute miles) above the earth’s surface.

Ambient pressure

The pressure in the area immediately surrounding the aircraft.

Ambient temperature

The temperature in the area immediately surrounding the aircraft.

AME

Aviation Medical Examiner.

AME

Aviation Medical Examiner.

Amendment status

The circulation date and revision number of an instrument approach procedure, printed above the procedure identification.

Ammeter

An instrument installed in series with an electrical load used to measure the amount of current flowing through the load.

Ammeter

An instrument installed in series with an electrical load used to measure the amount of current flowing through the load.

AMSL

Above Mean Sea Level

Anemometer

An instrument for measuring wind speed.

Aneroid

The sensitive component in an altimeter or barometer that measures the absolute pressure of the air. It is a sealed, flat capsule made of thin disks of corrugated metal soldered together and evacuated by pumping all of the air out of it.

Aneroid

Aneroid barometer

An instrument that measures the absolute pressure of the atmosphere by balancing the weight of the air above it against the spring action of the aneroid.

Aneroid barometer

A barometer which operates on the principle of having changing atmospheric pressure bend a metallic surface which, in turn, moves a pointer across a scale graduated in units of pressure.

Aneroid barometer

An instrument that measures the absolute pressure of the atmosphere by balancing the weight of the air above it against the spring action of the aneroid.

Angel

In radar meteorology, an echo caused by physical phenomena not discernible to the eye; they have been observed when abnormally strong temperature and/or moisture gradients were known to exist; sometimes attributed to insects or birds flying in the radar beam.

Angle Of Attack

The acute angle between the chord line of the airfoil and the direction of the relative wind.

Angle of attack

The acute angle formed between the chord line of an airfoil and the direction of the air striking the airfoil.

Angle of attack

The acute angle formed between the chord line of an airfoil and the direction of the air striking the airfoil.

Angle Of Incidence

The angle formed by the chord line of the wing and a line parallel to the longitudinal axis of the airplane.

Angle of incidence

The angle formed by the chord line of the wing and a line parallel to the longitudinal axis of the airplane.

Anhedral

A downward slant from root to tip of an aircraft’s wing or horizontal tail surface.

Annual Inspection

A complete inspection of an aircraft and engine, required by the Code of Federal Regulations, to be accomplished every 12 calendar months on all certificated aircraft. Only an A&P technician holding an Inspection Authorization can conduct an annual inspection.

Annual inspection

Anomalous propagation (sometimes called A P )

In radar meteorology, the greater than normal bending of the radar beam such that echoes are received from ground targets at distances greater than normal ground clutter.

ANP

Actual Navigation Performance

ANP

Actual Navigation Performance

ANR

Advanced Navigation Route

Anti-ice

Preventing the accumulation of ice on an aircraft structure via a system designed for that purpose.

Anti-ice

Preventing the accumulation of ice on an aircraft structure via a system designed for that purpose.

Anti-Icing

The prevention of the formation of ice on a surface. Ice may be prevented by using heat or by covering the surface with a chemical that prevents water from reaching the surface. Anti-icing should not be confused with deicing, which is the removal of ice after it has formed on the surface.

Anticyclone

An area of high atmospheric pressure which has a closed circulation that is anticyclonic, i.e., as viewed from above, the circulation is clockwise in the Northern Hemisphere, counterclockwise in the Southern Hemisphere, undefined at the Equator.

Antiservo tab

An adjustable tab attached to the trailing edge of a stabilator that moves in the same direction as the primary control. It is used to make the stabilator less sensitive.

Anvil cloud

Popular name given to the top portion of a cumulonimbus cloud having an anvil-like form.

Anxiety

Mental discomfort that arises from the fear of anything, real or imagined. May have a potent effect on actions and the ability to learn from perceptions.

AOA

Airport Operating Area

AOCC

Airline Operations Control Center

AP

Autopilot System

AP

Autopilot System

APC

Auxiliary Performance Computer

APOB

A sounding made by an aircraft.

Appliance

Any instrument, mechanism, equipment, part, apparatus, appurtenance, or accessory, including communications equipment, that is used or intended to be used in operating or controlling an aircraft in flight, is installed in or attached to the aircraft, and is not part of an airframe, engine, or propeller.

Application

A basic level of learning at which the student puts something to use that has been learned and understood.

Application step

The third step of the teaching process, where the student performs the procedure or demonstrates the knowledge required in the lesson. In the telling-and-doing technique of flight instruction, this step consists of the student doing the procedure while explaining it.

Approach Clearance

Authorization by ATC for a pilot to conduct an instrument approach. The type of instrument approach for which a clearance and other pertinent information is provided in the approach clearance when required.

Approach Control Facility

A terminal ATC facility that provides approach control service in a terminal area.

Approach Control Service

Air traffic control service provided by an approach control facility for arriving and departing VFR/IFR aircraft and, on occasion, en route aircraft. At some airports not served by an approach control facility, the ARTCC provides limited approach control service.

Approach End of Runway (AER)

The first portion of the runway available for landing. If the runway threshold is displaced, use the displaced threshold latitude/longitude as the AER.

Approach Fix

From a database coding standpoint, an approach fix is considered to be an identifiable point in space from the intermediate fix (IF) inbound. A fix located between the initial approach fix (IAF) and the IF is considered to be associated with the approach transition or feeder route.

Approach Gate

An imaginary point used by ATC to vector aircraft to the final approach course. The approach gate is established along the final approach course 1 NM from the final approach fix (FAF) on the side away from the airport and is located no closer than 5 NM from the landing threshold.

Approach Light System (ALS)

An airport lighting facility which provides visual guidance to landing aircraft by radiating light beams in a directional pattern by which the pilot aligns the aircraft with the extended centerline of the runway on his/her final approach for landing. Condenser-Discharge Sequential Flashing Lights/Sequenced Flashing Lights may be installed in conjunction with the ALS at some airports. Types of Approach Light Systems are: ALSF-1, ALSF-2, SSALF, SSALR, MALSF, MALSR, LDIN, RAIL, ODALS.

Approach Sequence

The order in which aircraft are positioned while on approach or awaiting approach clearance.

Approach Speed

The recommended speed contained in aircraft manuals used by pilots when making an approach to landing. This speed will vary for different segments of an approach as well as for aircraft weight and configuration.

Appropriate Authority

A. Regarding flight over the high seas: the relevant authority is the State of Registry.
B. Regarding flight over other than the high seas: the relevant authority is the State having sovereignty over the territory being overflown.

Appropriate Obstacle Clearance Minimum Altitude

Any of the following: Minimum En Route IFR Altitude, Minimum IFR Altitude, Minimum Obstruction Clearance Altitude, Minimum Vectoring Altitude.

Appropriate Terrain Clearance Minimum Altitude

Any of the following: Minimum En Route IFR Altitude, Minimum IFR Altitude, Minimum Obstruction Clearance Altitude, Minimum Vectoring Altitude.

Approved

Unless used with reference to another person, approved by the FAA or any person to whom the FAA has delegated its authority in the matter concerned, or approved under the provisions of a bilateral agreement between the United States and a foreign country or jurisdiction.

Approved Type Certificate

A certificate of approval issued by the FAA for the design of an aircraft, engine, or propeller.

Apron

A defined area on an airport or heliport intended to accommodate aircraft for purposes of loading or unloading passengers or cargo, refueling, parking, or maintenance. With regard to seaplanes, a ramp is used for access to the apron from the water.

APU

Auxiliary Power Unit.

APV

Approach With Vertical Guidance

Arc

The track over the ground of an aircraft flying at a constant distance from a navigational aid by reference to distance measuring equipment (DME).

Arctic air

An air mass with characteristics developed mostly in winter over Arctic surfaces of ice and snow. Arctic air extends to great heights, and the surface temperatures are basically, but not always, lower than those of polar air.

Arctic front

The surface of discontinuity between very cold (Arctic) air flowing directly from the Arctic region and another less cold and, consequently, less dense air mass.

Area chart

Part of the low-altitude en route chart series, this chart furnishes terminal data at a larger scale for congested areas.

Area chart

Part of the low-altitude en route chart series, this chart furnishes terminal data at a larger scale for congested areas.

Area forecast (FA)

A report that gives a picture of clouds, general weather conditions, and visual meteorological conditions (VMC) expected over a large area encompassing several states. (Discontinued, replaced by Graphical Forecasts for Aviation)

Area navigation (RNAV)

Allows a pilot to fly a selected course to a predetermined point without the need to overfly ground-based navigation facilities, by using waypoints.

Area Navigation (RNAV)

A method of navigation which permits aircraft operation on any desired flight path within the coverage of ground or space-based navigation aids or within the limits of the capability of self-contained aids, or a combination of these. Note: Area navigation includes performance-based navigation as well as other operations that do not meet the definition of performance-based navigation.

Area Navigation (RNAV) Approach Configuration

Includes Standard T, Modified T, Standard I, Terminal Arrival Area (TAA).

Area of operation

A phase of the practical test within the PTS.

ARENA

Areas Noted for Attention

ARFF

Aircraft Rescue and Fire Fighting

ARINC

An Acronym For Aeronautical Radio, Inc., A corporation largely owned by a group of airlines. ARINC is licensed by the FCC as an aeronautical station and contracted by the FAA to provide communications support for Air Traffic Control and Meteorological Services in portions of international airspace.

Arm

(GAMA) The horizontal distance from the reference datum to the center of gravity (CG) of an item. The algebraic sign is plus (+) if measured aft of the datum or to the right side of the center line when considering a lateral calculation. The algebraic sign is minus (-) if measured forward of the datum or the left side of the center line when considering a lateral calculation.

Armed Forces

The Army, Navy, Air Force, Marine Corps, and Coast Guard, including their regular and reserve components and members serving without component status.

ARO

Airport Reservations Office

ARPT

Airport

Arresting System

A safety device consisting of two major components, namely, engaging or catching devices and energy absorption devices for the purpose of arresting both tailhook and/or nontailhook-equipped aircraft. It is used to prevent aircraft from overrunning runways when the aircraft cannot be stopped after landing or during aborted takeoff. Arresting systems have various names; e.g., arresting gear, hook device, wire barrier cable.

Arrival Aircraft Interval

An internally generated program in hundredths of minutes based upon the AAR. AAI is the desired optimum interval between successive arrival aircraft over the vertex.

Arrival Center

The ARTCC having jurisdiction for the impacted airport.

Arrival Delay

A parameter which specifies a period of time in which no aircraft will be metered for arrival at the specified airport.

Arrival Time

The time an aircraft touches down on arrival.

ARSA

Airport Radar Service Area

ARSR

Air Route Surveillance Radar.

ARSR

Air Route Surveillance Radar. Air Route Traffic Control Center (ARTCC) radar used primarily to detect and display an aircraft´s position while en route between terminal areas. The ARSR enables controllers to provide radar air traffic control service when aircraft are within the ARSR coverage. In some instances, ARSR may enable an ARTCC to provide terminal radar services similar to but usually more limited than those provided by a radar approach control.

ARTCC

Air Route Traffic Control Center.

ARTCC

Air Route Traffic Control Center. A facility established to provide air traffic control service to aircraft operating on IFR flight plans within controlled airspace and principally during the en route phase of flight. When equipment capabilities and controller workload permit, certain advisory/assistance services may be provided to VFR aircraft. There are 20 ARTCCs in the continental U.S.

ARTS

Automated Radar Terminal System

ARTS

Automated Radar Terminal System

ARTS IIIA

The Radar Tracking and Beacon Tracking Level (RT&BTL) of the modular, programmable automated radar terminal system. ARTS IIIA detects, tracks, and predicts primary as well as secondary radar-derived aircraft targets. This more sophisticated computer-driven system upgrades the existing ARTS III system by providing improved tracking, continuous data recording, and fail-soft capabilities.

ASDA

Accelerate-Stop Distance Available

ASDAR

Aircraft To Satellite Data Relay

ASDE

Airport Surface Detection Equipment.

ASDE

Airport Surface Detection Equipment.

ASDE-3

Airport Surface Detection Equipment-3

ASDE-X

Airport Surface Detection Equipment-X

ASDE-X

Airport Surface Detection Equipment - Model X

ASOS

Automated Surface Observing Station.

ASOS

Automated Surface Observing System

ASOS

Automated Surface Observing System.

Aspect ratio

Span of a wing divided by its average chord.

ASR

Airport Surveillance Radar.

ASR

Airport Surveillance Radar. Approach control radar used to detect and display an aircraft´s position in the terminal area. ASR provides range and azimuth information but does not provide elevation data. Coverage of the ASR can extend up to 60 miles.

ASR APPROACH

Surveillance Approach

ASRS

Aviation Safety Reporting System

Astronomical twilight

The period of time before sunrise and after sunset when the sun is not more than 18° below the horizon.

Asymmetric thrust

Also known as P-factor. A tendency for an aircraft to yaw to the left due to the descending propeller blade on the right producing more thrust than the ascending blade on the left. This occurs when the aircraft’s longitudinal axis is in a climbing attitude in relation to the relative wind.The P-factor would be to the right if the aircraft had a counterclockwise rotating propeller.

ATC

Air Traffic Control.

ATC

Air Traffic Control. A service operated by appropriate authority to promote the safe, orderly and expeditious flow of air traffic.

ATC Advises

Used to prefix a message of noncontrol information when it is relayed to an aircraft by other than an air traffic controller.

ATC Assigned Airspace

Airspace of defined vertical/lateral limits, assigned by ATC, for the purpose of providing air traffic segregation between the specified activities being conducted within the assigned airspace and other IFR air traffic.

ATC Clearance

Air Traffic Clearance.

ATC Clears

Used to prefix an ATC clearance when it is relayed to an aircraft by other than an air traffic controller.

ATC Instructions

Directives issued by air traffic control for the purpose of requiring a pilot to take specific actions; e.g., “Turn left heading two five zero,” “Go around,” “Clear the runway.”

ATC Preferred Route Notification

URET notification to the appropriate controller of the need to determine if an ATC preferred route needs to be applied, based on destination airport.

ATC Requests

Used to prefix an ATC request when it is relayed to an aircraft by other than an air traffic controller.

ATC-TFM

Air Traffic Control Traffic Flow Management

ATCRBS

Air Traffic Control Radar Beacon System.

ATCRBS

Air Traffic Control Radar Beacon System

ATCSCC

Air Traffic Control System Command Center

ATCSCC

Air Traffic Control System Command Center

ATCT

Airport Traffic Control Tower

ATCT

Airport Traffic Control Tower. A terminal facility that uses air/ground communications, visual signaling, and other devices to provide ATC services to aircraft operating in the vicinity of an airport or on the movement area. Authorizes aircraft to land or takeoff at the airport controlled by the tower or to transit the Class D airspace area regardless of flight plan or weather conditions (IFR or VFR). A tower may also provide approach control services (radar or nonradar).

ATD

Along-Track Distance

ATD

Along-Track Distance

ATIS

Automatic Terminal Information Service.

ATIS

Automatic Terminal Information Service

ATIS

Automatic Terminal Information Service.

ATM

Air Traffic Management

Atmosphere

The mass of air surrounding the Earth.

Atmospheric pressure (also called barometric pressure)

The pressure exerted by the atmosphere as a consequence of gravitational attraction exerted upon the “column” of air lying directly above the point in question.

Atmospheric propagation delay

A bending of the electromagnetic (EM) wave from the satellite that creates an error in the GPS system.

Atmospheric propagation delay

A bending of the electromagnetic (EM) wave from the satellite that creates an error in the GPS system.

Atmospherics

Disturbing effects produced in radio receiving apparatus by atmospheric electrical phenomena such as an electrical storm. Static.

ATS

Air Traffic Service

ATS

Air Traffic Service.

ATT

Attitude Retention System

Attenuation

In radar meteorology, any process which reduces power density in radar signals.

Attitude

The position of an aircraft as determined by the relationship of its axes and a reference, usually the earth’s horizon.

Attitude

A personal motivational predisposition to respond to persons, situations, or events in a given manner that can, nevertheless, be changed or modified through training as a sort of mental shortcut to decision-making.

Attitude and heading reference system (AHRS)

A system composed of three-axis sensors that provide heading, attitude, and yaw information for aircraft. AHRS are designed to replace traditional mechanical gyroscopic flight instruments and provide superior reliability and accuracy.

Attitude and heading reference systems (AHRS)

System composed of three-axis sensors that provide heading, attitude, and yaw information for aircraft. AHRS are designed to replace traditional mechanical gyroscopic flight instruments and provide superior reliability and accuracy.

Attitude director indicator (ADI)

An aircraft attitude indicator that incorporates flight command bars to provide pitch and roll commands.

Attitude director indicator (ADI)

An aircraft attitude indicator that incorporates flight command bars to provide pitch and roll commands.

Attitude Indicator

An instrument which uses an artificial horizon and miniature airplane to depict the position of the airplane in relation to the true horizon. The attitude indicator senses roll pitch, which is the up and down as well as movement of the airplane’s nose.

Attitude indicator

The foundation for all instrument flight, this instrument reflects the airplanes attitude in relation to the horizon.

Attitude indicator

The foundation for all instrument flight, this instrument reflects the airplane’s attitude in relation to the horizon.

Attitude instrument flying

Controlling the aircraft by reference to the instruments rather than by outside visual cues.

Attitude management

The ability to recognize one’s own hazardous attitudes and the willingness to modify them as

Aurora

A luminous, radiant emission over middle and high latitudes confined to the thin air of high altitudes and centered over the earth’s magnetic poles. Called “aurora borealis” (northern lights) or “aurora australis” according to its occurrence in the Northern or Southern Hemisphere, respectively.

Authentic assessment

An assessment in which the student is asked to perform real-world tasks, and demonstrate a meaningful application of skills and competencies.

Autokinesis

This is caused by staring at a single point of light against a dark background for more than a few seconds. After a few moments, the light appears to move on its own.

Autokinesis

Nighttime visual illusion that a stationary light is moving, which becomes apparent after several seconds of staring at the light.

Autokinesis

Nighttime visual illusion that a stationary light is moving, which becomes apparent after several seconds of staring at the light.

Autoland Approach

An autoland approach is a precision instrument approach to touchdown and, in some cases, through the landing rollout. An autoland approach is performed by the aircraft autopilot which is receiving position information and/or steering commands from onboard navigation equipment. Note: Autoland and coupled approaches are flown in VFR and IFR. It is common for carriers to require their crews to fly coupled approaches and autoland approaches (if certified) when the weather conditions are less than approximately 4,000 RVR.

Automated Radar Terminal Systems (ARTS)

A generic term for several tracking systems included in the Terminal Automation Systems (TAS). ARTS plus a suffix roman numeral denotes a major modification to that system.

Automated Surface Observing Station (ASOS)

Weather reporting system which provides surface observations every minute via digitized voice broadcasts and printed reports.

Automated Surface Observing System (ASOS)

A weather observing system that provides minute-by-minute weather observations such as temperature, dew point, wind, altimeter setting, visibility, sky condition, and precipitation. Some ASOS stations include a precipitation discriminator which can differentiate between liquid and frozen precipitation.

Automated Surface Observing System (ASOS)

Weather reporting system which provides surface observations every minute via digitized voice broadcasts and printed reports.

Automated Surface Observing System (ASOS)

A suite of sensors that measure, collect, and disseminate weather data to help meteorologists, pilots, and flight dispatchers prepare and monitor weather forecasts, plan flight routes, and provide necessary information for correct takeoffs and landings. There are many differences between an ASOS and an All Weather Operations Specialist (AWOS) (see subparagraph 1-3d). It is important for pilots to understand the strengths and limitations of the various configurations. The ASOS is comprised of a standardized suite of weather sensors and is a product of a National Weather Service (NWS), Department of Defense (DOD), and FAA joint venture. One of ASOS’s most important features is its ability to detect precipitation, including intensity of rain, snow, and freezing rain. One current ASOS limitation is its inability to simultaneously detect and report freezing drizzle, ice pellets, or any other freezing precipitation without human augmentation when other forms of precipitation are present. A detailed description of ASOS’s capabilities can be found at the NWS ASOS homepage: http://www.nws.noaa.gov/asos/index.html.

Automated Surface Observing System (ASOS)/Automated Weather Sens

The ASOS/AWSS is the primary surface weather observing system of the U.S.

Automated Unicom

Provides completely automated weather, radio check capability and airport advisory information on an Automated UNICOM system. These systems offer a variety of features, typically selectable by microphone clicks, on the UNICOM frequency. Availability will be published in the Airport/Facility Directory and approach charts.

Automated Weather Observation System (AWOS)

A suite of weather sensors that are procured by the FAA or purchased by individuals, groups, airports, etc. It is important to note that the absence of reported precipitation does not mean that such conditions do not exist. The AWOS may not be configured to report this information or have precipitation reporting capability. A detailed description of AWOS’s capabilities can be found in the AIM.

Automated Weather Observing System (AWOS)

A suite of sensors which measure, collect, and disseminate weather data. AWOS stations provide a minute-by minute update of weather parameters such as wind speed and direction, temperature and dew point, visibility, cloud heights and types, precipitation, and barometric pressure. A variety of AWOS system types are available (from AWOS 1 to AWOS 3), each of which includes a different sensor array.

Automated Weather Observing System (AWOS)

Automated weather reporting system consisting of various sensors, a processor, a computer-generated voice subsystem, and a transmitter to broadcast weather data.

Automated Weather Sensor System (AWSS)

The AWSS is part of the Aviation Surface Weather Observation Network suite of programs and provides pilots and other users with weather information through the Automated Surface Observing System. The AWSS sensor suite automatically collects, measures, processes, and broadcasts surface weather data.

Automated Weather System

Any of the automated weather sensor platforms that collect weather data at airports and disseminate the weather information via radio and/or landline. The systems currently consist of the Automated Surface Observing System (ASOS), Automated Weather Sensor System (AWSS) and Automated Weather Observation System (AWOS).

Automated Weather System

Automatic Altitude Reporting

That function of a transponder which responds to Mode C interrogations by transmitting the aircraft’s altitude in 100-foot increments.

Automatic Dependent Surveillance-Broadcast (ADS-B)

A surveillance system that continuously broadcasts GPS position information, aircraft identification, altitude, velocity vector, and direction to all other aircraft and air traffic control facilities within a specific area. Automatic dependent surveillance-broadcast (ADS-B) information will be displayed in the cockpit via a cockpit display of traffic information (CDTI) unit, providing the pilot with greater situational awareness. ADS-B transmissions will also provide controllers with a more complete picture of traffic and will update that information more frequently than other surveillance equipment.

Automatic Dependent Surveillance-Broadcast (ADS-B)

A surveillance system in which an aircraft or vehicle to be detected is fitted with cooperative equipment in the form of a data link transmitter. The aircraft or vehicle periodically broadcasts its GPS-derived position and other information such as velocity over the data link, which is received by a ground-based transmitter/receiver (transceiver) for processing and display at an air traffic control facility.

Automatic Direction Finder

An aircraft radio navigation system which senses and indicates the direction to a L/MF nondirectional radio beacon (NDB) ground transmitter. Direction is indicated to the pilot as a magnetic bearing or as a relative bearing to the longitudinal axis of the aircraft depending on the type of indicator installed in the aircraft. In certain applications, such as military, ADF operations may be based on airborne and ground transmitters in the VHF/UHF frequency spectrum.

Automatic direction finder (ADF)

Electronic navigation equipment that operates in the low- and medium-frequency bands. Used in conjunction with the ground-based nondirectional beacon (NDB), the instrument displays the number of degrees clockwise from the nose of the aircraft to the station being received.

Automatic direction finder (ADF)

Automatic Flight Information Service (AFIS)

Alaska FSSs Only The continuous broadcast of recorded non-control information at airports in Alaska where a FSS provides local airport advisory service. The AFIS broadcast automates the repetitive transmission of essential but routine information such as weather, wind, altimeter, favored runway, breaking action, airport NOTAMs, and other applicable information. The information is continuously broadcast over a discrete VHF radio frequency (usually the ASOS/AWSS/AWOS frequency.

Automatic Terminal Information Service

The continuous broadcast of recorded noncontrol information in selected terminal areas. Its purpose is to improve controller effectiveness and to relieve frequency congestion by automating the repetitive transmission of essential but routine information; e.g., “Los Angeles information Alfa. One three zero zero Coordinated Universal Time. Weather, measured ceiling two thousand overcast, visibility three, haze, smoke, temperature seven one, dew point five seven, wind two five zero at five, altimeter two niner niner six. I-L-S Runway Two Five Left approach in use, Runway Two Five Right closed, advise you have Alfa.”

Automatic Terminal Information Service (ATIS)

A recorded broadcast available at most airports with an operating control tower that includes crucial information about runways and instrument approaches in use, specific outages, and current weather conditions, including visibility.

Autopilot

An automatic flight control system which keeps an aircraft in level flight or on a set course. Automatic pilots can be directed by the pilot, or they may be coupled to a radio navigation signal.

Autopilot

An automatic flight control system which keeps an aircraft in level flight or on a set course. Automatic pilots can be directed by the pilot, or they may be coupled to a radio navigation signal.

Autorotation

A rotorcraft flight condition in which the lifting rotor is driven entirely by action of the air when the rotorcraft is in motion.

Autorotative Landing/Touchdown Autorotation

Used by a pilot to indicate that the landing will be made without applying power to the rotor.

Auxiliary rotor

A rotor that serves either to counteract the effect of the main rotor torque on a rotorcraft or to maneuver the rotorcraft about one or more of its three principal axes.

Available Landing Distance (ALD)

The portion of a runway available for landing and roll-out for aircraft cleared for LAHSO. This distance is measured from the landing threshold to the hold-short point.

Aviation medical examiner (AME)

A physician with training in aviation medicine designated by the Civil Aerospace Medical Institute (CAMI).

Aviation medical examiner (AME)

A physician with training in aviation medicine designated by the Civil Aerospace Medical Institute (CAMI).

Aviation Routine Weather Report (METAR)

Observation of current surface weather reported in a standard international format.

Aviation Weather Service

A service provided by the National Weather Service (NWS) and FAA which collects and disseminates pertinent weather information for pilots, aircraft operators, and ATC. Available aviation weather reports and forecasts are displayed at each NWS office and FAA FSS.

Aviation Weather Service Program

Aviation weather service provided by the NWS and the FAA that collects and disseminates pertinent weather information for pilots, aircraft operators, and air traffic control (ATC).

AVN

Office of Aviation System Standards

AWC

Aviation Weather Center

AWOS

Automated Weather Observing System.

AWOS

Automated Weather Observing System

AWOS

Automated Weather Observing System.

AWSS

Automated Weather Sensor System

AWSS

Automated Weather Sensor System

AWTT

Aviation Weather Technology Transfer

AWW

Severe Weather Forecast Alert

Axes Of An Aircraft

Three imaginary lines that pass through an aircraft’s center of gravity. The axes can be considered as imaginary axles around which the aircraft turns. The three axes pass through the center of gravity at 90°angles to each other. The axis from nose to tail is the longitudinal axis, the axis that passes from wingtip to wingtip is the lateral axis, and the axis that passes vertically through the center of gravity is the vertical axis.

Axes of an aircraft

Three imaginary lines that pass through an aircraft’s center of gravity. The axes can be considered as imaginary axles around which the aircraft rotates. The three axes pass through the center of gravity at 90° angles to each other. The axis from nose to tail is the longitudinal axis (pitch), the axis that passes from wingtip to wingtip is the lateral axis (roll), and the axis that passes vertically through the center of gravity is the vertical axis (yaw).

Axial Flow Compressor

A type of compressor used in a turbine engine in which the airflow through the compressor is essentially linear. An axial-flow compressor is made up of several stages of alternate rotors and stators. The compressor ratio is determined by the decrease in area of the succeeding stages.

Azimuth card

A card that may be set, gyroscopically controlled, or driven by a remote compass.

Azimuth card

A card that may be set, gyroscopically controlled, or driven by a remote compass.

B-RNAV

European Basic Rnav

Back course (BC)

The reciprocal of the localizer course for an ILS. When flying a back-course approach, an aircraft approaches the instrument runway from the end at which the localizer antennas are installed.

Back Side Of The Power Curve

Flight regime in which flight at a higher airspeed requires a lower power setting and a lower airspeed requires a higher power setting in order to maintain altitude.

Back-Taxi

A term used by air traffic controllers to taxi an aircraft on the runway opposite to the traffic flow. The aircraft may be instructed to back-taxi to the beginning of the runway or at some point before reaching the runway end for the purpose of departure or to exit the runway.

Backing

Shifting of the wind in a counterclockwise direction with respect to either space or time; opposite of veering. Commonly used by meteorologists to refer to a cyclonic shift (counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere).

Backscatter

Pertaining to radar, the energy reflected or scattered by a target; an echo.

Balance tab

An auxiliary control mounted on a primary control surface, which automatically moves in the direction opposite the primary control to provide an aerodynamic assist in the movement of the control. Sometimes referred to as a servo tab.

Balanced Laterally

Balanced in such a way that the wings tend to remain level.

Balked Landing

A go-around.

Ballast

A weight installed or carried in an aircraft to move the center of gravity to a location within its allowable limits.

Balloon

The result of a too aggressive flare during landing causing the aircraft to climb.

Balloon

A lighter-than-air aircraft that is not engine driven, and that sustains flight through the use of either gas buoyancy or an airborne heater.

Banner cloud (also called cloud banner)

A banner-like cloud streaming off from a mountain peak.

Baro-aiding

A method of augmenting the GPS integrity solution by using a non-satellite input source. To ensure that baro-aiding is available, the current altimeter setting must be entered as described in the operating manual.

Baro-aiding

A method of augmenting the GPS integrity solution by using a nonsatellite input source. To ensure that baro-aiding is available, the current altimeter setting must be entered as described in the operating manual.

Baro-VNAV

Barometric Vertical Navigation

Barograph

A continuous-recording barometer.

Barometer

An instrument for measuring the pressure of the atmosphere; the two principle types are mercurial and aneroid.

Barometric altimeter

Also called a pressure altimeter. An aneroid barometer with a scale graduated in altitude instead of pressure using standard atmospheric pressure-height relationships; shows indicated altitude (not necessarily true altitude); may be set to measure altitude (indicated) from any arbitrarily chosen level.

Barometric pressure

Same as atmospheric pressure—the pressure exerted by the atmosphere as a consequence of gravitational attraction exerted upon the “column” of air lying directly above the point in question.

Barometric scale

A scale on the dial of an altimeter to which the pilot sets the barometric pressure level from which the altitude shown by the pointers is measured.

Barometric scale

A scale on the dial of an altimeter to which the pilot sets the barometric pressure level from which the altitude shown by the pointers is measured.

Barometric tendency

The change of barometric pressure within a specified period of time. In aviation weather observation, routinely determined periodically, usually for a 3-hour period.

Base Leg

A flight path at right angles to the landing runway off its approach end. The base leg normally extends from the downwind leg to the intersection of the extended runway centerline.

Basic Empty Weight

(GAMA) Standard empty weight plus optional equipment.

Basic Empty Weight (GAMA)

Basic empty weight includes the standard empty weight plus optional and special equipment that has been installed.

Basic empty weight (GAMA)

Basic empty weight includes the standard empty weight plus optional and special equipment that has been installed.

Basic need

A perception factor that describes a person’s ability to maintain and enhance the organized self.

Basic Operating Index

The moment of the airplane at its basic operating weight divided by the appropriate reduction factor.

Basic Operating Weight (BOW)

The empty weight of the aircraft plus the weight of the required crew, their baggage and other standard item such as meals and potable water.

Basic Radar Service

These services are provided for VFR aircraft by all commissioned terminal radar facilities. Basic radar service includes safety alerts, traffic advisories, limited radar vectoring when requested by the pilot, and sequencing at locations where procedures have been established for this purpose and/or when covered by a letter of agreement. The purpose of this service is to adjust the flow of arriving IFR and VFR aircraft into the traffic pattern in a safe and orderly manner and to provide traffic advisories to departing VFR aircraft.

BC

Back Course.

Beacon

Aeronautical Beacon.

Beam resolution

The ability of radar to distinguish between targets at approximately the same range but at different azimuths.

Bearing

The horizontal direction to or from any point, usually measured clockwise from true north, magnetic north, or some other reference point through 360 degrees.

Beaufort scale

A scale of wind speeds.

BECMG

Becoming group

Behaviorism

Theory of learning that stresses the importance of having a particular form of behavior reinforced by someone other than the student to shape or control what is learned.

Below Minimums

Weather conditions below the minimums prescribed by regulation for the particular action involved; e.g., landing minimums, takeoff minimums.

Bernoulli’s Principle

A principle that explains how the pressure of a moving fluid varies with its speed of motion. An increase in the speed of movement causes a decrease in the fluid’s pressure.

Best Angle Of Climb (Vx)

The speed at which the aircraft will produce the most gain in altitude in a given distance.

Best Glide

The airspeed in which the aircraft glides the furthest for the least altitude lost when in non-powered flight.

Best Rate Of Climb (Vy)

The speed at which the aircraft will produce the most gain in altitude in the least amount of time.

Bilge Area

The lowest part of an aircraft structure in which water and contaminants collect.

Biplanes

Airplanes with two sets of wings.

Black blizzard

Same as dust storm—an unusual, frequently severe weather condition characterized by strong winds and dust-filled air over an extensive area.

Blade Face

The flat portion of a propeller blade, resembling the bottom portion of an airfoil.

Blast Fence

A barrier that is used to divert or dissipate jet or propeller blast.

Blast Pad

A surface adjacent to the ends of a runway provided to reduce the erosive effect of jet blast and propeller wash.

Bleed Air

Compressed air tapped from the compressor stages of a turbine engine by use of ducts and tubing. Bleed air can be used for deice, anti-ice, cabin pressurization, heating, and cooling systems.

Bleed Valve

In a turbine engine, a flapper valve, a popoff valve, or a bleed band designed to bleed off a portion of the compressor air to the atmosphere. Used to maintain blade angle of attack and provide stall-free engine acceleration and deceleration.

Blind Spot

An area from which radio transmissions and/or radar echoes cannot be received. The term is also used to describe portions of the airport not visible from the control tower.

Blind Transmission

A transmission from one station to other stations in circumstances where two-way communication cannot be established, but where it is believed that the called stations may be able to receive the transmission.

Blind Zone

Blind Spot. An area from which radio transmissions and/or radar echoes cannot be received. The term is also used to describe portions of the airport not visible from the control tower.

Blizzard

A severe weather condition characterized by low temperatures and strong winds bearing a great amount of snow, either falling or picked up from the ground.

Block altitude

A block of altitudes assigned by ATC to allow altitude deviations; for example, Maintain block altitude 9 to 11 thousand.

Blocked

Phraseology used to indicate that a radio transmission has been distorted or interrupted due to multiple simultaneous radio transmissions.

Blowing dust

A type of lithometeor composed of dust particles picked up locally from the surface and blown about in clouds or sheets.

Blowing sand

A type of lithometeor composed of sand picked up locally from the surface and blown about in clouds or sheets.

Blowing snow

A type of hydrometeor composed of snow picked up from the surface by the wind and carried to a height of 6 feet or more.

Blowing spray

A type of hydrometeor composed of water particles picked up by the wind from the surface of a large body of water.

Boost Pump

An electrically driven fuel pump, usually of the centrifugal type, located in one of the fuel tanks. It is used to provide fuel to the engine for starting and providing fuel pressure in the event of failure of the engine driven pump. It also pressurizes the fuel lines to prevent vapor lock.

Boundary Lights

Lights defining the perimeter of an airport or landing area.

Brake horsepower

The power delivered at the propeller shaft (main drive or main output) of an aircraft engine.

Braking Action (Good, Fair, Poor, Or Nil)

A report of conditions on the airport movement area providing a pilot with a degree/quality of braking that he/she might expect. Braking action is reported in terms of good, fair, poor, or nil.

Braking Action Advisories

When tower controllers have received runway braking action reports which include the terms “fair,” “poor,” or “nil,” or whenever weather conditions are conducive to deteriorating or rapidly changing runway braking conditions, the tower will include on the ATIS broadcast the statement, “Braking action advisories are in effect” on the ATIS broadcast. During the time braking action advisories are in effect, ATC will issue the latest braking action report for the runway in use to each arriving and departing aircraft. Pilots should be prepared for deteriorating braking conditions and should request current runway condition information if not volunteered by controllers. Pilots should also be prepared to provide a descriptive runway condition report to controllers after landing.

Branching

A programming technique which allows users of interactive video, multimedia courseware, or online training to choose from several courses of action in moving from one sequence to another.

Breakout

A technique to direct aircraft out of the approach stream. In the context of close parallel operations, a breakout is used to direct threatened aircraft away from a deviating aircraft.

Briefing

An oral presentation where the speaker presents a concise array of facts without inclusion of extensive supporting material.

Bright band

In radar meteorology, a narrow, intense echo on the range-height indicator scope resulting from water-covered ice particles of high reflectivity at the melting level.

BRITE

Bright Radar Indicator Tower Equipment

Broadcast

Transmission of information for which an acknowledgement is not expected.

Buffeting

The beating of an aerodynamic structure or surface by unsteady flow, gusts, etc.; the irregular shaking or oscillation of a vehicle component owing to turbulent air or separated flow.

Building block concept

Concept of learning that new knowledge and skills are best based on a solid foundation of previous experience and/or old learning. As knowledge and skills increase, the base expands, supporting further learning.

Bus Bar

An electrical power distribution point to which several circuits may be connected. It is often a solid metal strip having a number of terminals installed on it.

Bus Tie

A switch that connects two or more bus bars. It is usually used when one generator fails and power is lost to its bus. By closing the switch, the operating generator powers both busses.

Butt (or buttock) Line Zero

A line through the symmetrical center of an aircraft from nose to tail. It serves as the datum for measuring the arms used to determine the lateral CG. Lateral moments that cause the aircraft to rotate clockwise are positive (+) , and those that cause it to rotate counterclockwise are negative (-).

Buys Ballot’s law

If an observer in the Northern Hemisphere stands with his back to the wind, lower pressure is to his left.

Bypass Air

The part of a turbofan’s induction air that bypasses the engine core.

Bypass Ratio

The ratio of the mass airflow in pounds per second through the fan section of a turbofan engine to the mass airflow that passes through the gas generator portion of the engine. Or, the ratio between fan mass airflow (lb/sec.) and core engine mass airflow (lb/sec.).

C/A

Coarse Acquisition

CAA

Civil Aeronautics Administration

CAASD

Center For Advanced Aviation Systems Development

Cabin altitude

Cabin pressure in terms of equivalent altitude above sea level.

Cabin Pressurization

A condition where pressurized air is forced into the cabin simulating pressure conditions at a much lower altitude and increasing the aircraft occupants comfort.

Cage

The black markings on the ball instrument indicating its neutral position.

Cage

The black markings on the ball instrument indicating its neutral position.

Calculated Landing Time

A term that may be used in place of tentative or actual calculated landing time, whichever applies.

Calendar Month

A time period used by the FAA for certification and currency purposes. A calendar month extends from a given day until midnight of the last day of that month.

Calibrated

The instrument indication compared with a standard value to determine the accuracy of the instrument.

Calibrated

The instrument indication compared with a standard value to determine the accuracy of the instrument.

Calibrated airspeed

The speed at which the aircraft is moving through the air, found by correcting IAS for instrument and position errors.

Calibrated airspeed

The speed at which the aircraft is moving through the air, found by correcting IAS for instrument and position errors.

Calibrated Airspeed (CAS)

Indicated airspeed corrected for installation error and instrument error. Although manufacturers attempt to keep airspeed errors to a minimum, it is not possible to eliminate all errors throughout the airspeed operating range. At certain airspeeds and with certain flap settings, the installation and instrument errors may total several knots. This error is generally greatest at low airspeeds. In the cruising and higher airspeed ranges, indicated airspeed and calibrated airspeed are approximately the same. Refer to the airspeed calibration chart to correct for possible airspeed errors.

Calibrated orifice

A hole of specific diameter used to delay the pressure change in the case of a vertical speed indicator.

Calibrated orifice

A hole of specific diameter used to delay the pressure change in the case of a vertical speed indicator.

Call For Release

Wherein the overlying ARTCC requires a terminal facility to initiate verbal coordination to secure ARTCC approval for release of a departure into the en route environment.

Calm

The absence of wind or of apparent motion of the air.

Camber

The camber of an airfoil is the characteristic curve of its upper and lower surfaces. The upper camber is more pronounced, while the lower camber is comparatively flat. This causes the velocity of the airflow immediately above the wing to be much higher than that below the wing.

Cambered

CAMP

Continuous Airworthiness Maintenance Program.

CAMs

The manuals containing the certification rules under the Civil Air Regulations.

Canard

A horizontal surface mounted ahead of the main wing to provide longitudinal stability and control. It may be a fixed, movable, or variable geometry surface, with or without control surfaces.

Canard configuration

A configuration in which the span of the forward wings is substantially less than that of the main wing.

Cantilever

A wing designed to carry loads without external struts.

Cap cloud

Also called cloud cap. A standing or stationary cap-like cloud crowning a mountain summit.

Carburetor

1. Pressure: A hydromechanical device employing a closed feed system from the fuel pump to the discharge nozzle. It meters fuel through fixed jets according to the mass airflow through the throttle body and discharges it under a positive pressure. Pressure carburetors are distinctly different from float-type carburetors, as they do not incorporate a vented float chamber or suction pickup from a discharge nozzle located in the venturi tube. 2. Float-type: Consists essentially of a main air passage through which the engine draws its supply of air, a mechanism to control the quantity of fuel discharged in relation to the flow of air, and a means of regulating the quantity of fuel/air mixture delivered to the engine cylinders.

Carburetor Ice

Ice that forms inside the carburetor due to the temperature drop caused by the vaporization of the fuel. Induction system icing is an operational hazard because it can cut off the flow of the fuel/air charge or vary the fuel/air ratio.

Cardinal Altitudes

“Odd” or “Even” thousand-foot altitudes or flight levels; e.g., 5,000, 6,000, 7,000, FL 250, FL 260, FL 270.

Cardinal Flight Levels

Cardinal Altitudes. “Odd” or “Even” thousand-foot altitudes or flight levels; e.g., 5,000, 6,000, 7,000, FL 250, FL 260, FL 270.

CARF

Central Altitude Reservation Function

CARTS

Common Automated Radar Terminal System (ARTS) (to include ARTS IIIE and ARTS IIE)

CAS

Calibrated Airspeed.

CAS

Calibrated Airspeed.

Cascade Reverser

A thrust reverser normally found on turbofan engines in which a blocker door and a series of cascade vanes are used to redirect exhaust gases in a forward direction.

CAT

Clear Air Turbulence

CAT II

Category II.

Catch Point

A fix/waypoint that serves as a transition point from the high altitude waypoint navigation structure to an arrival procedure (STAR) or the low altitude ground-based navigation structure.

Category A

With respect to transport category rotorcraft, multiengine rotorcraft designed with engine and system isolation features specified in Part 29 and utilizing scheduled takeoff and landing operations under a critical engine failure concept which assures adequate designated surface area and adequate performance capability for continued safe flight in the event of engine failure.

Category A

An Aircraft Approach Category. Speed less than 91 knots.

Category B

With respect to transport category rotorcraft, single-engine or multiengine rotorcraft which do not fully meet all Category A standards. Category B rotorcraft have no guaranteed stay-up ability in the event of engine failure and unscheduled landing is assumed.

Category B

An Aircraft Approach Category. Speed 91 knots or more but less than 121 knots.

Category C

An Aircraft Approach Category. Speed 121 knots or more but less than 141 knots.

Category D

An Aircraft Approach Category. Speed 141 knots or more but less than 166 knots.

Category E

An Aircraft Approach Category. Speed 166 knots or more.

Category II operations

With respect to the operation of aircraft, a straight-in ILS approach to the runway of an airport under a Category II ILS instrument approach procedure issued by the Administrator or other appropriate authority.

Category III operations

With respect to the operation of aircraft, an ILS approach to, and landing on, the runway of an airport using a Category III ILS instrument approach procedure issued by the Administrator or other appropriate authority.

Category IIIa operations

An ILS approach and landing with no decision height (DH), or a DH below 100 feet (30 meters), and controlling runway visual range not less than 700 feet (200 meters).

Category IIIb operations

An ILS approach and landing with no DH, or with a DH below 50 feet (15 meters), and controlling runway visual range less than 700 feet (200 meters), but not less than 150 feet (50 meters).

Category IIIc operations

An ILS approach and landing with no DH and no runway visual range limitation.

CDI

Course Deviation Indicator.

CDI

Course Deviation Indicator

CDM

Collaborative Decision Making

CDM

Collaborative Decision Making. Cooperative effort between the various components of aviation transportation, both government and industry, to exchange information for better decision making.

CDR

Coded Departure Routes. Predefined routes used to route air traffic around areas of severe weather.

CDTI

Cockpit Display of Traffic Information

CDU

Control Display Unit

Ceiling

In meteorology in the U.S., (1) the height above the surface of the base of the lowest layer of clouds or obscuring phenomena aloft that hides more than half of the sky, or (2) the vertical visibility into an obscuration.

Ceiling

The height above the earth’s surface of the lowest layer of clouds, which is reported as broken or overcast, or the vertical visibility into an obscuration.

Ceiling balloon

A small balloon used to determine the height of a cloud base or the extent of vertical visibility.

Ceiling light

An instrument which projects a vertical light beam onto the base of a cloud or into surface-based obscuring phenomena; used at night in conjunction with a clinometer to determine the height of the cloud base or as an aid in estimating the vertical visibility.

Ceilometer

A cloud-height measuring system. It projects light on the cloud, detects the reflection by a photo-electric cell, and determines height by triangulation.

Celsius temperature scale (abbreviated C)

A temperature scale with zero degrees as the melting point of pure ice and 100 degrees as the boiling point of pure water at standard sea level atmospheric pressure.

CENRAP

Center Radar Arts Processing

Center

Air Route Traffic Control Center.

Center of Gravity (CG)

(GAMA) The point at which an airplane would balance if suspended. Its distance from the reference datum is determined by dividing the total moment by the total weight of the airplane. It is the mass center of the aircraft, or the theoretical point at which the entire weight of the aircraft is assumed to be concentrated. It may be expressed in percent of MAC (mean aerodynamic cord) or in inches from the reference Center of Lift. The location along the chord line of an airfoil at which all the lift forces produced by the airfoil are considered to be concentrated.

Center of gravity limits

The specified forward and aft points within which the CG must be located during flight. These limits are indicated on pertinent airplane specifications.

Center of gravity range

The distance between the forward and aft CG limits indicated on pertinent airplane specifications.

Center of pressure

A point along the wing chord line where lift is considered to be concentrated. For this reason, the center of pressure is commonly referred to as the center of lift.

Center Weather Advisory

An unscheduled weather advisory issued by Center Weather Service Unit meteorologists for ATC use to alert pilots of existing or anticipated adverse weather conditions within the next 2 hours. A CWA may modify or redefine a SIGMET.

Center Weather Advisory (CWA)

An unscheduled weather advisory issued by NWS meteorologists for use by ATC in alerting pilots to existing or anticipated adverse weather conditions within the next 2 hours. A CWA may modify a SIGMET.

Center-Of-Gravity Limits

The specified forward and aft points within which the CG must be located during flight. These limits are indicated on pertinent airplane specifications.

Center-Of-Gravity Range

The distance between the forward and aft CG limits indicated on pertinent airplane specifications.

Center’s Area

The specified airspace within which an air route traffic control center (ARTCC) provides air traffic control and advisory service.

Centigrade temperature scale

Same as Celsius temperature scale—a temperature scale with zero degrees as the melting point of pure ice and 100 degrees as the boiling point of pure water at standard sea level atmospheric pressure.

Central East Pacific

An organized route system between the U.S. West Coast and Hawaii.

Centrifugal Flow Compressor

An impeller-shaped device that receives air at its center and slings air outward at high velocity into a diffuser for increased pressure. Also referred to as a radial outflow compressor.

Centrifugal force

An outward force, that opposes centripetal force, resulting from the effect of inertia during a turn.

Centripetal force

A center-seeking force directed inward toward the center of rotation created by the horizontal component of lift in turning flight.

Centroid

The distance in inches aft of the datum of the center of a compartment or a fuel tank for weight and balance purposes.

CFA

Controlled Firing Area

CFIT

Controlled Flight Into Terrain

CFIT

Controlled Flight into Terrain

CFR

Code of Federal Regulations

CFR

Code of Federal Regulations

CFR

Call For Release

CG

Center Of Gravity.

CG Arm

(GAMA) The arm obtained by adding the airplane’s individual moments and dividing the sum by the total weight.

CG Limits

(GAMA) The extreme center of gravity locations within which the aircraft must be operated at a given weight. These limits are indicated on pertinent FAA aircraft type certificate data sheets, specifications, or weight and balance records.

CG Limits Envelope

An enclosed area on a graph of the airplane loaded weight and the CG location. If lines drawn from the weight and CG cross within this envelope, the airplane is properly loaded.

CG Moment Envelope

An enclosed area on a graph of the airplane loaded weight and loaded moment. If lines drawn from the weight and loaded moment cross within this envelope, the airplane is properly loaded.

CGD

Combined Graphic Display

Chaff

Pertaining to radar, (1) short, fine strips of metallic foil dropped from aircraft, usually by military forces, specifically for the purpose of jamming radar; (2) applied loosely to echoes resulting from chaff.

Chaff

Thin, narrow metallic reflectors of various lengths and frequency responses, used to reflect radar energy. These reflectors when dropped from aircraft and allowed to drift downward result in large targets on the radar display.

Change of state

In meteorology, the transformation of water from one form, i.e., solid (ice), liquid, or gaseous (water vapor), to any other form. There are six possible transformations designated by the five terms following: condensation, evaporation, freezing, melting, or sublimation.

Changeover Point (COP)

A COP indicates the point where a frequency change is necessary between navigation aids when other than the midpoint on an airway, to receive course guidance from the facility ahead of the aircraft instead of the one behind. These COPs divide an airway or route segment and ensure continuous reception of navigational signals at the prescribed minimum en route IFR altitude.

Charted VFR Flyways

Charted VFR Flyways are flight paths recommended for use to bypass areas heavily traversed by large turbine-powered aircraft. Pilot compliance with recommended flyways and associated altitudes is strictly voluntary. VFR Flyway Planning charts are published on the back of existing VFR Terminal Area charts.

Charted Visual Flight Procedure Approach

An approach conducted while operating on an instrument flight rules (IFR) flight plan which authorizes the pilot of an aircraft to proceed visually and clear of clouds to the airport via visual landmarks and other information depicted on a charted visual flight procedure. This approach must be authorized and under the control of the appropriate air traffic control facility. Weather minimums required are depicted on the chart.

Chase Aircraft

An aircraft flown in proximity to another aircraft normally to observe its performance during training or testing.

CHDO

An FAA Flight Standards Certificate Holding District Office.

Checklist

A tool that is used as a human factors aid in aviation safety. It is a systematic and sequential list of all operations that must be performed to properly accomplish a task.

Chinook

A warm, dry foehn wind blowing down the eastern slopes of the Rocky Mountains over the adjacent plains in the U.S. and Canada.

Chord

A straight-line distance across a wing from leading edge to trailing edge.

Chord Line

An imaginary straight line drawn through an airfoil from the leading edge to the trailing edge.

CIGS

Ceilings. The height above the ground of the base of the lowest layer of clouds when over half of the sky is obscured.

Circle To Runway (Runway Number)

Used by ATC to inform the pilot that he/she must circle to land because the runway in use is other than the runway aligned with the instrument approach procedure. When the direction of the circling maneuver in relation to the airport/runway is required, the controller will state the direction (eight cardinal compass points) and specify a left or right downwind or base leg as appropriate; e.g., “Cleared VOR Runway Three Six Approach circle to Runway Two Two,” or “Circle northwest of the airport for a right downwind to Runway Two Two.”

Circle-To-Land Maneuver

A maneuver initiated by the pilot to align the aircraft with a runway for landing when a straight-in landing from an instrument approach is not possible or is not desirable. At tower controlled airports, this maneuver is made only after ATC authorization has been obtained and the pilot has established required visual reference to the airport.

Circling approach

A maneuver initiated by the pilot to align the aircraft with a runway for landing when a straight- in landing from an instrument approach is not possible or is not desirable.

Circling Minima

Landing Minimums [for a circling approach].

Circuit Breaker

A circuit-protecting device that opens the circuit in case of excess current flow. A circuit breakers differs from a fuse in that it can be reset without having to be replaced.

Cirriform

All species and varieties of cirrus, cirrocumulus, and cirrostratus clouds; descriptive of clouds composed mostly or entirely of small ice crystals, usually transparent and white; often producing halo phenomena not observed with other cloud forms. Average height ranges upward from 20,000 feet in middle latitudes.

Cirrocumulus

A cirriform cloud appearing as a thin sheet of small white puffs resembling flakes or patches of cotton without shadows; sometimes confused with altocumulus.

Cirrostratus

A cirriform cloud appearing as a whitish veil, usually fibrous, sometimes smooth; often produces halo phenomena; may totally cover the sky.

Cirrus

A cirriform cloud in the form of thin, white feather-like clouds in patches or narrow bands; have a fibrous and/or silky sheen; large ice crystals often trail downward a considerable vertical distance in fibrous, slanted, or irregularly curved wisps called mares’ tails.

Civil Air Regulation (CAR)

Predecessor to the Federal Aviation Regulations.

Civil aircraft

Aircraft other than public aircraft.

Civil twilight

The period of time before sunrise and after sunset when the sun is not more than 6° below the horizon.

Class

(1) As used with respect to the certification, ratings, privileges, and limitations of airmen, a classification of aircraft within a category having similar operating characteristics. Examples include: single engine; multiengine; land; water; gyroplane; helicopter; airship; and free balloon; and
(2) As used with respect to the certification of aircraft, a broad grouping of aircraft having similar characteristics of propulsion, flight, or landing. Examples include: airplane; rotorcraft; glider; balloon; landplane; and seaplane.

Class A airspace

Airspace from 18,000 feet MSL up to and including FL 600, including the airspace overlying the waters within 12 NM of the coast of the 48 contiguous states and Alaska; and designated international airspace beyond 12 NM of the coast of the 48 contiguous states and Alaska within areas of domestic radio navigational signal or ATC radar coverage, and within which domestic procedures are applied.

Class A airspace

Class B airspace

Airspace from the surface to 10,000 feet MSL surrounding the nations busiest airports in terms of IFR operations or passenger numbers. The configuration of each Class B airspace is individually tailored and consists of a surface area and two or more layers, and is designed to contain all published instrument procedures once an aircraft enters the airspace. For all aircraft, an ATC clearance is required to operate in the area, and aircraft so cleared receive separation services within the airspace.

Class B airspace

Airspace from the surface to 10,000 feet MSL surrounding the nation’s busiest airports in terms of IFR operations or passenger numbers. The configuration of each Class B airspace is individually tailored and consists of a surface area and two or more layers, and is designed to contain all published instrument procedures once an aircraft enters the airspace. For all aircraft, an ATC clearance is required to operate in the area, and aircraft so cleared receive separation services within the airspace.

Class C airspace

Airspace from the surface to 4,000 feet above the airport elevation (charted in MSL) surrounding those airports having an operational control tower, serviced by radar approach control, and having a certain number of IFR operations or passenger numbers. Although the configuration of each Class C airspace area is individually tailored, the airspace usually consists of a 5 NM radius core surface area that extends from the surface up to 4,000 feet above the airport elevation, and a 10 NM radius shelf area that extends from 1,200 feet to 4,000 feet above the airport elevation.

Class C airspace

Class C Service

This service provides, in addition to basic radar service, approved separation between IFR and VFR aircraft, and sequencing of VFR aircraft, and sequencing of VFR arrivals to the primary airport.

Class D airspace

Airspace from the surface to 2,500 feet above the airport elevation (charted in MSL) surrounding those airports that have an operational control tower. The configuration of each Class D airspace area is individually tailored, and when instrument procedures are published, the airspace is normally designed to contain the procedures.

Class D airspace

Class D Airspace

Controlled Airspace.

Class E

Generally, if the airspace is not Class A, Class B, Class C, or Class D, and it is controlled airspace, it is Class E airspace. Class E airspace extends upward from either the surface or a designated altitude to the overlying or adjacent controlled airspace. When designated as a surface area, the airspace will be configured to contain all instrument procedures. Also in this class are Federal airways, airspace beginning at either 700 or 1,200 feet AGL used to transition to/from the terminal or en route environment, en route domestic, and offshore airspace areas designated below 18,000 feet MSL. Unless designated at a lower altitude, Class E airspace begins at 14,500 MSL over the United States, including that airspace overlying the waters within 12 nautical miles of the coast of the 48 contiguous States and Alaska, up to, but not including 18,000 feet MSL, and the airspace above FL 600.

Class E airspace

Airspace that is not Class A, Class B, Class C, or Class D, and is controlled airspace.

Class G airspace

Airspace that is uncontrolled, except when associated with a temporary control tower, and has not been designated as Class A, Class B, Class C, Class D, or Class E airspace.

Class G airspace

Airspace that is uncontrolled, except when associated with a temporary control tower, and has not been designated as Class A, Class B, Class C, Class D, or Class E airspace.

Clean configuration

A configuration in which all flight control surfaces have been placed to create minimum drag. In most aircraft this means flaps and gear retracted.

Clean configuration

A configuration in which all flight control surfaces have been placed to create minimum drag. In most aircraft this means flaps and gear retracted.

Clear air turbulence

Turbulence encountered in air where no clouds are present; more popularly applied to high level turbulence associated with wind shear. (abbreviated CAT)

Clear Air Turbulence (CAT)

Turbulence encountered in air where no clouds are present. This term is commonly applied to high-level turbulence associated with wind shear. CAT is often encountered in the vicinity of the jet stream.

Clear ice

Glossy, clear, or translucent ice formed by the relatively slow freezing of large, supercooled water droplets.

Clear ice

Glossy, clear, or translucent ice formed by the relatively slow freezing of large, supercooled water droplets.

Clear Ice

A glossy, clear, or translucent ice formed by the relatively slow freezing or large supercooled water droplets.

Clear Ice

A glossy, clear, or translucent ice formed by the relatively slow freezing of supercooled water drops. The terms “clear” and “glaze” have been used for essentially the same type of ice accretion, although some reserve “clear” for thinner accretions, which lack horns and conform to the airfoil. If the freezing becomes more rapid, clear ice will turn cloudy as small bubbles of air become trapped in the ice. If the conditions persist, the ice would be classified as mixed.

Clear icing (or clear ice)

Generally, the formation of a layer or mass of ice which is relatively transparent because of its homogeneous structure and small number and size of air spaces; used commonly as synonymous with glaze, particularly with respect to aircraft icing. Compare with rime icing. Factors which favor clear icing are large drop size, such as those found in cumuliform clouds, rapid accretion of supercooled water, and slow dissipation of latent heat of fusion.

Clear Of The Runway

A. Taxiing aircraft, which is approaching a runway, is clear of the runway when all parts of the aircraft are held short of the applicable runway holding position marking.
B. A pilot or controller may consider an aircraft, which is exiting or crossing a runway, to be clear of the runway when all parts of the aircraft are beyond the runway edge and there are no restrictions to its continued movement beyond the applicable runway holding position marking.
C. Pilots and controllers shall exercise good judgement to ensure that adequate separation exists between all aircraft on runways and taxiways at airports with inadequate runway edge lines or holding position markings.

Clearance

ATC permission for an aircraft to proceed under specified traffic conditions within controlled airspace, for the purpose of providing separation between known aircraft.

Clearance

ATC permission for an aircraft to proceed under specified traffic conditions within controlled airspace, for the purpose of providing separation between known aircraft.

Clearance delivery

Control tower position responsible for transmitting departure clearances to IFR flights.

Clearance limit

The fix, point, or location to which an aircraft is cleared when issued an air traffic clearance.

Clearance on request

An IFR clearance not yet received after filing a flight plan.

Clearance Void If Not Off By (Time)

Used by ATC to advise an aircraft that the departure clearance is automatically canceled if takeoff is not made prior to a specified time. The pilot must obtain a new clearance or cancel his/her IFR flight plan if not off by the specified time.

Clearance void time

Used by ATC, the time at which the departure clearance is automatically canceled if takeoff has not been made. The pilot must obtain a new clearance or cancel the IFR flight plan if not off by the specified time.

Cleared (Type Of) Approach

ATC authorization for an aircraft to execute a specific instrument approach procedure to an airport; e.g., “Cleared ILS Runway Three Six Approach.”

Cleared Approach

ATC authorization for an aircraft to execute any standard or special instrument approach procedure for that airport. Normally, an aircraft will be cleared for a specific instrument approach procedure.

Cleared As Filed

Means the aircraft is cleared to proceed in accordance with the route of flight filed in the flight plan. This clearance does not include the altitude, DP, or DP Transition.

Cleared For Takeoff

ATC authorization for an aircraft to depart. It is predicated on known traffic and known physical airport conditions.

Cleared For The Option

ATC authorization for an aircraft to make a touch-and-go, low approach, missed approach, stop and go, or full stop landing at the discretion of the pilot. It is normally used in training so that an instructor can evaluate a student’s performance under changing situations.

Cleared Through

ATC authorization for an aircraft to make intermediate stops at specified airports without refiling a flight plan while en route to the clearance limit.

Cleared To Land

ATC authorization for an aircraft to land. It is predicated on known traffic and known physical airport conditions.

Clearway

(1) For turbine engine powered airplanes certificated after August 29, 1959, an area beyond the runway, not less than 500 feet wide, centrally located about the extended centerline of the runway, and under the control of the airport authorities. The clearway is expressed in terms of a clearway plane, extending from the end of the runway with an upward slope not exceeding 1.25 percent, above which no object nor any terrain protrudes. However, threshold lights may protrude above the plane if their height above the end of the runway is 26 inches or less and if they are located to each side of the runway.
(2) For turbine engine powered airplanes certificated after September 30, 1958, but before August 30, 1959, an area beyond the takeoff runway extending no less than 300 feet on either side of the extended centerline of the runway, at an elevation no higher than the elevation of the end of the runway, clear of all fixed obstacles, and under the control of the airport authorities.

Climate

The statistical collective of the weather conditions of a point or area during a specified interval of time (usually several decades); may be expressed in a variety of ways.

Climatology

The study of climate.

Climb Gradient

The ratio between distance traveled and altitude gained.

Climb To VFR

ATC authorization for an aircraft to climb to VFR conditions within Class B, C, D, and E surface areas when the only weather limitation is restricted visibility. The aircraft must remain clear of clouds while climbing to VFR.

Climbout

That portion of flight operation between takeoff and the initial cruising altitude.

Climbout speed

With respect to rotorcraft, a referenced airspeed which results in a flight path clear of the height-velocity envelope during initial climbout.

Clinometer

An instrument used in weather observing for measuring angles of inclination; it is used in conjunction with a ceiling light to determine cloud height at night.

Close Parallel Runways

Two parallel runways whose extended centerlines are separated by less than 4,300 feet, having a Precision Runway Monitoring (PRM) system that permits simultaneous independent ILS approaches.

Closed Runway

A runway that is unusable for aircraft operations. Only the airport management/military operations office can close a runway.

Closed Traffic

Successive operations involving takeoffs and landings or low approaches where the aircraft does not exit the traffic pattern.

Cloud

A cloud is a visible accumulation of minute water droplets and/or ice particles in the atmosphere above the Earth’s surface. Cloud differs from ground fog, fog, or ice fog only in that the latter are, by definition, in contact with the Earth’s surface.

Cloud bank

Generally, a fairly well-defined mass of cloud observed at a distance; it covers an appreciable portion of the horizon sky, but does not extend overhead.

Cloud cap

Also called a cap cloud. A standing or stationary cap-like cloud crowning a mountain summit.

Cloud detection radar

A vertically directed radar to detect cloud bases and tops.

Cloudburst

In popular terminology, any sudden and heavy fall of rain, almost always of the shower type.

CLSD

Closed

CLT

Calculated Landing Time

Clutter

In radar operations, clutter refers to the reception and visual display of radar returns caused by precipitation, chaff, terrain, numerous aircraft targets, or other phenomena. Such returns may limit or preclude ATC from providing services based on radar.

CNF

Computer Navigation Fix

CNS

Communication,Navigation, and Surveillance

COA

Certificate of Waiver or Authorization

Coastal Air Defense Identification Zone

An ADIZ over the coastal waters of the United States.

Cockpit display of traffic information (CDTI)

The display and user interface for information about air traffic within approximately 80 miles. It will typically combine and show traffic data from TCAS, TIS-B, and ADS-B. Depending on features, the display may also show terrain, weather, and navigation information.

Cockpit Resource Management

Techniques designed to reduce pilot errors and manage errors that do occur utilizing cockpit human resources. The assumption is that errors are going to happen in a complex system with error-prone humans.

Coefficient Of Lift

See Lift Coefficient.

Coffin Corner

The flight regime where any increase in airspeed will induce high speed mach buffet and any decrease in airspeed will induce low speed mach buffet.

Cognitive domain

A grouping of levels of learning associated with mental activity. In order of increasing complexity, the domains are knowledge, comprehension, application, analysis, synthesis, and evaluation.

Cold front

Any non-occluded front which moves in such a way that colder air replaces warmer air.

Cold Front

Any nonoccluded front that moves in such a way that colder air replaces warmer air.

Collision Hazard

A condition, event, or circumstance that could induce an occurrence of a collision or surface accident or incident.

Columns

See Database Columns

Combustion Chamber

The section of the engine into which fuel is injected and burned.

Commercial operator

A person who, for compensation or hire, engages in the carriage by aircraft in air commerce of persons or property, other than as an air carrier or foreign air carrier or under the authority of Part 375 of this title. Where it is doubtful that an operation is for “compensation or hire”, the test applied is whether the carriage by air is merely incidental to the person’s other business or is, in itself, a major enterprise for profit.

Common ARTS

Includes ARTS IIE, ARTS IIIE; and ARTS IIIE with ACD (see DTAS) which combines functionalities of the previous ARTS systems.

Common Point

A significant point over which two or more aircraft will report passing or have reported passing before proceeding on the same or diverging tracks. To establish/maintain longitudinal separation, a controller may determine a common point not originally in the aircraft’s flight plan and then clear the aircraft to fly over the point.

Common Route

Typically the portion of a RNAV STAR between the en route transition end point and the runway transition start point; however, the common route may only consist of a single point that joins the en route and runway transitions.

Common Traffic Advisory Frequency (CTAF)

A frequency designed for the purpose of carrying out airport advisory practices while operating to or from an airport without an operating control tower. The CTAF may be a UNICOM, Multicom, FSS, or tower frequency and is identified in appropriate aeronautical publications.

Compass course

A true course corrected for variation and deviation errors.

Compass course

A true course corrected for variation and deviation errors.

Compass Locator

A low power, low or medium frequency (L/MF) radio beacon installed at the site of the outer or middle marker of an instrument landing system (ILS). It can be used for navigation at distances of approximately 15 miles or as authorized in the approach procedure.

Compass rose

A small circle graduated in 360 increments, printed on navigational charts to show the amount of compass variation at different locations, or on instruments to indicate direction.

Compass Rose

A circle, graduated in degrees, printed on some charts or marked on the ground at an airport. It is used as a reference to either true or magnetic direction.

Complex Aircraft

An aircraft with retractable landing gear, flaps, and a controllable-pitch propeller, or is turbine powered.

Complex aircraft

An aircraft with retractable landing gear, flaps, and a controllable pitch propeller.

Comply With Restrictions

An ATC instruction that requires an aircraft being vectored back onto an arrival or departure procedure to comply with all altitude and/or speed restrictions depicted on the procedure. This term may be used in lieu of repeating each remaining restriction that appears on the procedure.

Composite Flight Plan

A flight plan which specifies VFR operation for one portion of flight and IFR for another portion. It is used primarily in military operations.

Comprehensiveness

The degree to which a test measures the overall objective.

Compression Ratio

1. In a reciprocating engine, the ratio of the volume of an engine cylinder with the piston at the bottom center to the volume with the piston at top center. 2. In a turbine engine, the ratio of the pressure of the air at the discharge to the pressure of air at the inlet.

Compressor Bleed Air

See Bleed Air.

Compressor Bleed Valves

See Bleed Valve.

Compressor pressure ratio

The ratio of compressor discharge pressure to compressor inlet pressure.

Compressor Section

The section of a turbine engine that increases the pressure and density of the air flowing through the engine.

Compressor Stall

In gas turbine engines, a condition in an axial-flow compressor in which one or more stages of rotor blades fail to pass air smoothly to the succeeding stages. A stall condition is caused by a pressure ratio that is incompatible with the engine r.p.m. Compressor stall will be indicated by a rise in exhaust temperature or r.p.m. fluctuation, and if allowed to continue, may result in flameout and physical damage to the engine.

Compressor Surge

A severe compressor stall across the entire compressor that can result in severe damage if not quickly corrected. This condition occurs with a complete stoppage of airflow or a reversal of airflow.

Compulsory Reporting Points

Reporting points which must be reported to ATC. They are designated on aeronautical charts by solid triangles or filed in a flight plan as fixes selected to define direct routes. These points are geographical locations which are defined by navigation aids/fixes. Pilots should discontinue position reporting over compulsory reporting points when informed by ATC that their aircraft is in “radar contact.”

Computer navigation fix

A point used to define a navigation track for an airborne computer system such as GPS or FMS.

Computer navigation fix

A point used to define a navigation track for an airborne computer system such as GPS or FMS.

Computer-assisted instruction

Instruction in which the instructor is responsible for the class and uses the computer to assist in the instruction.

Concentric rings

Dashed-line circles depicted in the plan view of IAP charts, outside of the reference circle, that show en route and feeder facilities.

Condensation

The change of water vapor to liquid water.

Condensation level

The height at which a rising parcel or layer of air would become saturated if lifted adiabatically.

Condensation nuclei

Small particles in the air on which water vapor condenses or sublimates.

Condensation trail (or contrail) (also called vapor trail)

A cloud-like streamer frequently observed to form behind aircraft flying in clear, cold, humid air.

Condition

The second part of a performance-based objective which describes the framework under which the skill or behavior will be demonstrated.

Condition Lever

In a turbine engine, a powerplant control that controls the flow of fuel to the engine. The condition lever sets the desired engine r.p.m. within a narrow range between that appropriate for ground and flight operations.

Conditionally unstable air

Unsaturated air that will become unstable on the condition it becomes saturated.

Conduction

The transfer of heat by molecular action through a substance or from one substance in contact with another; transfer is always from warmer to colder temperature.

Cone of confusion

A cone-shaped volume of airspace directly above a VOR station where no signal is received, causing the CDI to fluctuate.

Cone of confusion

A cone-shaped volume of airspace directly above a VOR station where no signal is received, causing the CDI to fluctuate.

Confidence Maneuver

A confidence maneuver consists of one or more turns, a climb or descent, or other maneuver to determine if the pilot in command (PIC) is able to receive and comply with ATC instructions.

Configuration

This is a general term, which normally refers to the position of the landing gear and flaps.

Configuration, Maintenance, and Procedures (CMP) document

A document approved by the FAA that contains minimum configuration, operating, and maintenance requirements, hardware life-limits, and Master Minimum Equipment List (MMEL) constraints necessary for an airplane-engine combination to meet ETOPS type design approval requirements.

Conflict Alert

A function of certain air traffic control automated systems designed to alert radar controllers to existing or pending situations between tracked targets (known IFR or VFR aircraft) that require his/her immediate attention/action.

Conflict Resolution

The resolution of potential conflictions between aircraft that are radar identified and in communication with ATC by ensuring that radar targets do not touch. Pertinent traffic advisories shall be issued when this procedure is applied. Note: This procedure shall not be provided utilizing mosaic radar systems.

Confusion between the symbol and the symbolized object.

Results when a word is confused with what it is meant to represent. Words and symbols create confusion when they mean different things to different people.

Consensus standard

For the purpose of certificating light-sport aircraft, an industry-developed consensus standard that applies to aircraft design, production, and airworthiness. It includes, but is not limited to, standards for aircraft design and performance, required equipment, manufacturer quality assurance systems, production acceptance test procedures, operating instructions, maintenance and inspection procedures, identification and recording of major repairs and major alterations, and continued airworthiness.

CONSOL or CONSOLAN

A kind of low or medium frequency long range navigational aid.

Consolan

A low frequency, long-distance NAVAID used principally for transoceanic navigations.

Constant pressure chart

A chart of a constant pressure surface; may contain analyses of height, wind, temperature, humidity, and/or other elements.

Constant Speed Propeller

A controllable pitch propeller whose pitch is automatically varied in flight by a governor to maintain a constant r.p.m. in spite of varying air loads.

Constant-speed propeller

A controllable-pitch propeller whose pitch is automatically varied in flight by a governor to maintain a constant rpm in spite of varying air loads.

Contact

A. Establish communication with (followed by the name of the facility and, if appropriate, the frequency to be used).
B. A flight condition wherein the pilot ascertains the attitude of his/her aircraft and navigates by visual reference to the surface.

Contact Approach

An approach where an aircraft on an IFR flight plan, having an air traffic control authorization, operating clear of clouds with at least one mile flight visibility, and a reasonable expectation of continuing to the destination airport in those conditions, may deviate from the instrument approach procedure and proceed to the destination airport by visual reference to the surface. This approach will only be authorized when requested by the pilot and the reported ground visibility at the destination airport is at least one statute mile.

Contaminated Runway

A runway is considered contaminated whenever standing water, ice, snow, slush, frost in any form, heavy rubber, or other substances are present. A runway is contaminated with respect to rubber deposits or other friction-degrading substances when the average friction value for any 500-foot segment of the runway within the ALD fails below the recommended minimum friction level and the average friction value in the adjacent 500-foot segments falls below the maintenance planning friction level.

Conterminous U.S.

The 48 adjoining States and the District of Columbia.

Continental polar air

Also called polar air. An air mass with characteristics developed over high latitudes, especially within the subpolar highs. Continental polar air (cP) has cold surface temperatures, low moisture content, and, especially in its source regions, has great stability in the lower layers. It is shallow in comparison with Arctic air.

Continental tropical air

Also called tropical air. An air mass with characteristics developed over low latitudes. Continental tropical (cT) is produced over subtropical arid regions and is hot and very dry.

Continental United States

The 49 States located on the continent of North America and the District of Columbia.

Continue

When used as a control instruction should be followed by another word or words clarifying what is expected of the pilot. Example: “continue taxi,” “continue descent,” “continue inbound,” etc.

Continuous flow oxygen system

System that supplies a constant supply of pure oxygen to a rebreather bag that dilutes the pure oxygen with exhaled gases and thus supplies a healthy mix of oxygen and ambient air to the mask. Primarily used in passenger cabins of commercial airliners.

Contour

In meteorology, (1) a line of equal height on a constant pressure chart; analogous to contours on a relief map; (2) in radar meteorology, a line on a radar scope of equal echo intensity.

Contouring circuit

On weather radar, a circuit which displays multiple contours of echo intensity simultaneously on the plan position indicator or range-height indicator scope. A line on a radar scope of equal echo intensity.

Contrail

Contraction for condensation trail.

Control and performance

A method of attitude instrument flying in which one instrument is used for making attitude changes, and the other instruments are used to monitor the progress of the change.

Control Area [ICAO]

A controlled airspace extending upwards from a specified limit above the earth.

Control display unit

A display interfaced with the master computer, providing the pilot with a single control point for all navigations systems, thereby reducing the number of required flight deck panels.

Control display unit

A display interfaced with the master computer, providing the pilot with a single control point for all navigations systems, thereby reducing the number of required flight deck panels.

Control pressures

The amount of physical exertion on the control column necessary to achieve the desired attitude.

Control pressures

The amount of physical exertion on the control column necessary to achieve the desired attitude.

Control Sector

An airspace area of defined horizontal and vertical dimensions for which a controller or group of controllers has air traffic control responsibility, normally within an air route traffic control center or an approach control facility. Sectors are established based on predominant traffic flows, altitude strata, and controller workload. Pilot-communications during operations within a sector are normally maintained on discrete frequencies assigned to the sector.

Control Touch

The ability to sense the action of the airplane and its probable actions in the immediate future, with regard to attitude and speed variations, by sensing and evaluation of varying pressures and resistance of the control surfaces transmitted through the cockpit flight controls.

Controllability

A measure of the response of an aircraft relative to the pilot’s flight control inputs.

Controllable Pitch Propeller

A propeller in which the blade angle can be changed during flight by a control in the cockpit.

Controlled airspace

An airspace of defined dimensions within which ATC service is provided to IFR and VFR flights in accordance with the airspace classification. It includes Class A, Class B, Class C, Class D, and Class E airspace.

Controlled airspace

Controlled Firing Area

A controlled firing area is established to contain activities, which if not conducted in a controlled environment, would be hazardous to nonparticipating aircraft.

Controlled Flight Into Terrain (CFIT)

A situation where a mechanically normally functioning airplane is inadvertently flown into the ground, water, or an obstacle. There are two basic causes of CFIT accidents; both involve flight crew situational awareness. One definition of situational awareness is an accurate perception by pilots of the factors and conditions currently affecting the safe operation of the aircraft and the crew. The causes of CFIT are the flight crews lack of vertical position awareness or their lack of horizontal position awareness in relation to terrain and obstacles.

Controlled Time Of Arrival

Arrival time assigned during a Traffic Management Program. This time may be modified due to adjustments or user options.

Controller

Air Traffic Control Specialist.

Convection

(l) In general, mass motions within a fluid resulting in transport and mixing of the properties of that fluid. (2) In meteorology, atmospheric motions that are predominantly vertical, resulting in vertical transport and mixing of atmospheric properties; distinguished from advection.

Convection

An atmospheric motion resulting in the transport and mixing of atmospheric properties.

Convective cloud

Cumuliform. A term descriptive of all convective clouds exhibiting vertical development in contrast to the horizontally extended stratiform types.

Convective condensation level (abbreviated CCL)

The lowest level at which condensation will occur as a result of convection due to surface heating. When condensation occurs at this level, the layer between the surface and the CCL will be thoroughly mixed, temperature lapse rate will be dry adiabatic, and mixing ratio will be constant.

Convective instability

The state of an unsaturated layer of air whose lapse rates of temperature and moisture are such that when lifted adiabatically until the layer becomes saturated, convection is spontaneous.

Convective SIGMET

Weather advisory concerning convective weather significant to the safety of all aircraft, including thunderstorms, hail, and tornadoes.

Convective SIGMET

Weather advisory concerning convective weather significant to the safety of all aircraft, including thunderstorms, hail, and tornadoes.

Convective SIGMET

A weather advisory concerning convective weather significant to the safety of all aircraft. Convective SIGMETs are issued for tornadoes, lines of thunderstorms, embedded thunderstorms of any intensity level, areas of thunderstorms greater than or equal to VIP level 4 with an area coverage of 4/10 (40%) or more, and hail 3/4 inch or greater.

Convective weather

Unstable, rising air found in cumuliform clouds.

Conventional Landing Gear

Landing gear employing a third rear-mounted wheel. These airplanes are also sometimes referred to as tailwheel airplanes.

Convergence

The condition that exists when the distribution of winds within a given area is such that there is a net horizontal inflow of air into the area. In convergence at lower levels, the removal of the resulting excess is accomplished by an upward movement of air; consequently, areas of low-level convergent winds are regions favorable to the occurrence of clouds and precipitation. Compare with divergence.

Cooperative or group learning

An instructional strategy which organizes students into small groups so that they can work together to maximize their own and each other’s learning.

Coordinated Flight

Application of all appropriate flight and power controls to prevent slipping or skidding in any flight condition.

Coordinated flight

Flight with a minimum disturbance of the forces maintaining equilibrium, established via effective control use.

Coordinated flight

Flight with a minimum disturbance of the forces maintaining equilibrium, established via effective control use.

Coordinates

The intersection of lines of reference, usually expressed in degrees/minutes/seconds of latitude and longitude, used to determine position or location.

Coordination

The ability to use the hands and feet together subconsciously and in the proper relationship to produce desired results in the airplane.

COP

Changeover Point.

Copter

Helicopter.

Core Airflow

Air drawn into the engine for the gas generator.

Coriolis force

A deflective force resulting from earth’s rotation; it acts to the right of wind direction in the Northern Hemisphere and to the left in the Southern Hemisphere.

Coriolis illusion

The illusion of rotation or movement in an entirely different axis, caused by an abrupt head movement, while in a prolonged constant rate turn that has ceased stimulating the brains motion sensing system.

Coriolis illusion

The illusion of rotation or movement in an entirely different axis, caused by an abrupt head movement, while in a prolonged constant-rate turn that has ceased to stimulate the brain’s motion sensing system.

Corona

A prismatically colored circle or arcs of a circle with the sun or moon at its center; coloration is from blue inside to red outside (opposite that of a halo); varies in size (much smaller) as opposed to the fixed diameter of the halo; characteristic of clouds composed of water droplets and valuable in differentiating between middle and cirriform clouds.

Corposant

St. Elmo’s Fire. A luminous brush discharge of electricity from protruding objects, such as masts and yardarms of ships, aircraft, lightning rods, steeples, etc., occurring in stormy weather. Also called corposant.

Corrected altitude

Indicated altitude of an aircraft altimeter corrected for the temperature of the column of air below the aircraft, the correction being based on the estimated departure of existing temperature from standard atmospheric temperature; an approximation of true altitude.

Correction

An error has been made in the transmission and the correct version follows.

Correlation

A basic level of learning where the student can associate what has been learned, understood, and applied with previous or subsequent learning.

COTS

Commercial Off The Shelf

Coupled ailerons and rudder

Rudder and ailerons are connected with interconnected springs in order to counteract adverse yaw. Can be overridden if it becomes necessary to slip the aircraft.

Coupled Approach

A coupled approach is an instrument approach performed by the aircraft autopilot which is receiving position information and/or steering commands from onboard navigation equipment. In general, coupled nonprecision approaches must be discontinued and flown manually at altitudes lower than 50 feet below the minimum descent altitude, and coupled precision approaches must be flown manually below 50 feet AGL. Note: Coupled and autoland approaches are flown in VFR and IFR. It is common for carriers to require their crews to fly coupled approaches and autoland approaches (if certified) when the weather conditions are less than approximately 4,000 RVR.

Course

The intended direction of flight in the horizontal plane measured in degrees from north.

Course Controlled Airspace

A. The intended direction of flight in the horizontal plane measured in degrees from north. B. The ILS localizer signal pattern usually specified as the front course or the back course. C. The intended track along a straight, curved, or segmented MLS path.

Course of training

A complete series of studies leading to attainment of a specific goal, such as a certificate of completion, graduation, or an academic degree.

Cowl Flaps

Devices arranged around certain air-cooled engine cowlings which may be opened or closed to regulate the flow of air around the engine.

CPDLC

Controller Pilot Data Link Communications

CPDLC

Controller Pilot Data Link Communications

Crab

A flight condition in which the nose of the airplane is pointed into the wind a sufficient amount to counteract a crosswind and maintain a desired track over the ground.

Crazing

Small fractures in aircraft windshields and windows caused from being exposed to the ultraviolet rays of the sun and temperature extremes.

CRC

Cyclic Redundancy Check

CRCT

Collaborative Routing Coordination Tool

Crew resource management (CRM)

The effective use of all available resources human, hardware, and information.

Crew resource management (CRM)

The application of team management concepts in the flight deck environment. It was initially known as cockpit resource management, but as CRM programs evolved to include cabin crews, maintenance personnel and others, the phrase “crew resource management” has been adopted. This includes single pilots, as in most general aviation aircraft. Pilots of small aircraft, as well as crews of larger aircraft, must make effective use of all available resources; human resources, hardware, and information. A current definition includes all groups routinely working with the cockpit crew who are involved in decisions required to operate a flight safely. These groups include, but are not limited to: pilots, dispatchers, cabin crewmembers, maintenance personnel, and air traffic controllers. CRM is one way of addressing the challenge of optimizing the human/machine interface and accompanying interpersonal activities.

Crew resource management (CRM)

The application of team management concepts in the flight deck environment. It was initially known as cockpit resource management, but as CRM programs evolved to include cabin crews, maintenance personnel, and others, the phrase “crew resource management” was adopted. This includes single pilots, as in most general aviation aircraft. Pilots of small aircraft, as well as crews of larger aircraft, must make effective use of all available resources; human resources, hardware, and information. A current definition includes all groups routinely working with the flight crew who are involved in decisions required to operate a flight safely. These groups include, but are not limited to pilots, dispatchers, cabin crewmembers, maintenance personnel, and air traffic controllers. CRM is one way of addressing the challenge of optimizing the human/machine interface and accompanying interpersonal activities.

Crewmember

A person assigned to perform duty in an aircraft during flight time.

Criteria

The third part of a performance-based objective, descriptions of standards that will be used to measure the accomplishment of the objective.

Criterion-referenced testing

System of testing where students are graded against a carefully written, measurable standard or criterion rather than against each other.

Critical Altitude

The maximum altitude under standard atmospheric conditions at which a turbocharged engine can produce its rated horsepower.

Critical altitude

The maximum altitude at which, in standard atmosphere, it is possible to maintain, at a specified rotational speed, a specified power or a specified manifold pressure. Unless otherwise stated, the critical altitude is the maximum altitude at which it is possible to maintain, at the maximum continuous rotational speed, one of the following:
(1) The maximum continuous power, in the case of engines for which this power rating is the same at sea level and at the rated altitude.
(2) The maximum continuous rated manifold pressure, in the case of engines, the maximum continuous power of which is governed by a constant manifold pressure.

Critical Angle Of Attack

The angle of attack at which a wing stalls regardless of airspeed, flight attitude, or weight.

Critical angle of attack

The angle of attack at which a wing stalls regardless of airspeed, flight attitude, or weight.

Critical areas

Areas where disturbances to the ILS localizer and glide slope courses may occur when surface vehicles or aircraft operate near the localizer or glide slope antennas.

Critical areas

Areas where disturbances to the ILS localizer and glideslope courses may occur when surface vehicles or aircraft operate near the localizer or glideslope antennas.

Critical Engine

The engine whose failure has the most adverse effect on directional control.

Critical Engine

The engine which, upon failure, would most adversely affect the performance or handling qualities of an aircraft.

CRM

Crew Resource Management.

CRM

Crew Resource Management.

CRM

Crew Resource Management.

Cross (Fix) At (Altitude)

Used by ATC when a specific altitude restriction at a specified fix is required.

Cross (Fix) At Or Above (Altitude)

Used by ATC when an altitude restriction at a specified fix is required. It does not prohibit the aircraft from crossing the fix at a higher altitude than specified; however, the higher altitude may not be one that will violate a succeeding altitude restriction or altitude assignment.

Cross (Fix) At Or Below (Altitude)

Used by ATC when a maximum crossing altitude at a specific fix is required. It does not prohibit the aircraft from crossing the fix at a lower altitude; however, it must be at or above the minimum IFR altitude.

Cross Controlled

A condition where aileron deflection is in the opposite direction of rudder deflection.

Cross-check

The first fundamental skill of instrument flight, also known as scan, the continuous and logical observation of instruments for attitude and performance information.

Crossfeed

A system that allows either engine on a twin-engine airplane to draw fuel from any fuel tank.

Crosswind

A. When used concerning the traffic pattern, the word means “crosswind leg.” B. When used concerning wind conditions, the word means a wind not parallel to the runway or the path of an aircraft.

Crosswind Component

The wind component, measured in knots, at 90° to the longitudinal axis of the runway.

Crosswind Leg

A flight path at right angles to the landing runway off its upwind end.

Cruise

Used in an ATC clearance to authorize a pilot to conduct flight at any altitude from the minimum IFR altitude up to and including the altitude specified in the clearance. The pilot may level off at any intermediate altitude within this block of airspace. Climb/descent within the block is to be made at the discretion of the pilot. However, once the pilot starts descent and verbally reports leaving an altitude in the block, he/she may not return to that altitude without additional ATC clearance. Further, it is approval for the pilot to proceed to and make an approach at destination airport and can be used in conjunction with: a. An airport clearance limit at locations with a standard/special instrument approach procedure. The CFRs require that if an instrument letdown to an airport is necessary, the pilot shall make the letdown in accordance with a standard/special instrument approach procedure for that airport, or b. An airport clearance limit at locations that are within/below/outside controlled airspace and without a standard/special instrument approach procedure. Such a clearance is NOT AUTHORIZATION for the pilot to descend under IFR conditions below the applicable minimum IFR altitude nor does it imply that ATC is exercising control over aircraft in Class G airspace; however, it provides a means for the aircraft to proceed to destination airport, descend, and land in accordance with applicable CFRs governing VFR flight operations. Also, this provides search and rescue protection until such time as the IFR flight plan is closed.

Cruise clearance

An ATC clearance issued to allow a pilot to conduct flight at any altitude from the minimum IFR altitude up to and including the altitude specified in the clearance. Also authorizes a pilot to proceed to and make an approach at the destination airport.

Cruise Climb

A climb technique employed by aircraft, usually at a constant power setting, resulting in an increase of altitude as the aircraft weight decreases.

Cruising Altitude

An altitude or flight level maintained during en route level flight. This is a constant altitude and should not be confused with a cruise clearance.

Cruising Level

Cruising Altitude. An altitude or flight level maintained during en route level flight. This is a constant altitude and should not be confused with a cruise clearance.

CTAF

Common Traffic Advisory Frequency

CTAF

Common Traffic Advisory Frequency

CTD

Controlled Time of Departure

Cumuliform

A term descriptive of all convective clouds exhibiting vertical development in contrast to the horizontally extended stratiform types.

Cumulonimbus

A cumuliform cloud·type; it is heavy and dense, with considerable vertical extent in the form of massive towers; often with tops in the shape of an anvil or massive plume; under the base of cumulonimbus, which often is very dark, there frequently exists virga, precipitation and low ragged clouds (scud), either merged with it or not; frequently accompanied by lightning, thunder, and sometimes hail; occasionally produces a tornado or a waterspout; the ultimate manifestation of the growth of a cumulus cloud, occasionally extending well into the stratosphere.

Cumulonimbus mamma

A cumulonimbus cloud having hanging protuberances, like pouches, festoons, or udders, on the under side of the cloud; usually indicative of severe turbulence.

Cumulus

A cloud in the form of individual detached domes or towers which are usually dense and well defined; develops vertically in the form of rising mounds of which the bulging upper part often resembles a cauliflower; the sunlit parts of these clouds are mostly brilliant white; their bases are relatively dark and nearly horizontal.

Cumulus Clouds

Clouds in the form of detached domes or towers that are usually well defined. Cumulus clouds develop vertically in the form of rising mounds of which the bulging upper part often resembles a cauliflower; the sunlit parts of these clouds are mostly brilliant white. Their bases may be relatively dark and nearly horizontal.

Cumulus fractus

Cumulus clouds ( Clouds in the form of individual detached domes or towers which are usually dense and well defined) in the form of irregular shreds, appearing as if torn; have a clearly ragged appearance; applies only to stratus and cumulus, i.e., cumulus fractus and stratus fractus.

Current Flight Plan [ICAO]

The flight plan, including changes, if any, brought about by subsequent clearances.

Current Icing Product (CIP)

A graphical planning product that combines sensor and numerical model data to provide a three-dimensional diagnosis of the probability and severity of icing, plus the potential for the presence of supercooled large drops (SLD). This product is automatically produced with no human modification. More information can be found on the Aviation Weather Center (AWC) Aviation Digital Data Service (ADDS) Web site.

Current induction

An electrical current being induced into, or generated in, any conductor that is crossed by lines of flux from any magnet.

Current Limiter

A device that limits the generator output to a level within that rated by the generator manufacturer.

Current Plan

The ATC clearance the aircraft has received and is expected to fly.

Curriculum

A set of courses in an area of specialization offered by an educational institution. A curriculum for a pilot school usually includes courses for the various pilot certificates and ratings.

Curtailment

An operator created and FAA-approved operational loading envelope that is more restrictive than the manufacturer’s CG envelope. It ensures that the aircraft will be operated within limits during all phases of flight. Curtailment typically accounts for, but is not limited to, in-flight movement of passengers and crew, service equipment, cargo variation, seating variation, etc.

Cut-away

Model of an object that is built in sections so it can be taken apart to reveal the inner structure.

CVFP

Charted Visual Flight Procedure

CVFP

Charted Visual Flight Procedure

CVRS

Computerized Voice Reservation System

CWA

Center Weather Advisory

CWSU

Center Weather Service Unit

Cyclogenesis

Any development or strengthening of cyclonic circulation in the atmosphere.

Cyclone

(l) An area of low atmospheric pressure,. which has a closed circulation that is cyclonic, i.e., as viewed from above, the circulation is counterclockwise in the Northern Hemisphere, clockwise in the Southern Hemisphere, undefined at the Equator. Because cyclonic circulation and relatively low atmospheric pressure usually co-exist, in common practice the terms cyclone and low are used interchangeably. Also, because cyclones often are accompanied by inclement (sometimes destructive) weather, they are frequently referred to simply as storms. (2) Frequently misused to denote a tornado. (3) In the Indian Ocean, a tropical cyclone of hurricane or typhoon force.

D-ATIS

Digital Automatic Terminal Information Service

D-ATIS

Digital-Automatic Terminal Information Service

D-value

Departure of true altitude from pressure altitude; obtained by algebraically subtracting true altitude from pressure altitude; thus it may be plus or minus. On a constant pressure chart, the difference between actual height and standard atmospheric height of a constant pressure surface.

D.C.

Direct Current.

D.C.

Direct Current.

DA

Decision Altitude.

DACS

Digital Aeronautical Chart Supplement

Dark adaptation

Physical and chemical adjustments of the eye that make vision possible in relative darkness.

Database Identifier

A specific geographic point in space identified on an aeronautical chart and in an aviation database, officially designated by the controlling state authority or derived by Jeppesen. It has no ATC function and should not be used in filing flight plans nor used when communicating with ATC.

Datum (Reference Datum)

An imaginary vertical plane or line from which all measurements of moment arm are taken. The datum is established by the manufacturer. Once the datum has been selected, all moment arms the location of CG range are measured from this point.

DBRITE

Digital Bright Radar Indicator Tower Equipment

DCA

Ronald Reagan Washington National Airport

DCP

Data Collection Package

Dead reckoning

Navigation of an airplane solely by means of computations based on airspeed, course, heading, wind direction and speed, groundspeed, and elapsed time.

Deceleration error

A magnetic compass error that occurs when the aircraft decelerates while flying on an easterly or westerly heading, causing the compass card to rotate toward South.

Deceleration error

A magnetic compass error that occurs when the aircraft decelerates while flying on an easterly or westerly heading, causing the compass card to rotate toward South.

Decision Altitude (DA)

A specified altitude in the precision approach at which a missed approach must be initiated if the required visual reference to continue the approach has not been established. The term Decision Altitude (DA) is referenced to mean sea level and the term Decision Height (DH)is referenced to the threshold elevation. Even though DH is charted as an altitude above MSL, the U.S. has adopted the term DAas a step toward harmonization of the United States and international terminology. At some point, DA will be published for all future instrument approach procedures with vertical guidance.

Decision Altitude/Decision Height [ICAO]

A specified altitude or height (A/H) in the precision approach at which a missed approach must be initiated if the required visual reference to continue the approach has not been established. Note 1: Decision altitude [DA] is referenced to mean sea level [MSL] and decision height [DH] is referenced to the threshold elevation. Note 2: The required visual reference means that section of the visual aids or of the approach area which should have been in view for sufficient time for the pilot to have made an assessment of the aircraft position and rate of change of position, in relation to the desired flight path.

Decision height (DH)

A specified height above the ground in an instrument approach procedure at which the pilot must decide whether to initiate an immediate missed approach if the pilot does not see the required visual reference, or to continue the approach. Decision height is expressed in feet above ground level.

Decompression Sickness

A condition where the low pressure at high altitudes allows bubbles of nitrogen to form in the blood and joints causing severe pain. Also known as the bends.

Deepening

A decrease in the central pressure of a pressure system; usually applied to a low rather than to a high, although technically, it is acceptable in either sense.

Defense mechanisms

Subconscious ego-protecting reactions to unpleasant situations.

Defense Visual Flight Rules

Rules applicable to flights within an ADIZ conducted under the visual flight rules in 14 CFR Part 91.

Deice

The act of removing ice accumulation from an aircraft structure.

Deice

The act of removing ice accumulation from an aircraft structure.

Deicer Boots

Inflatable rubber boots attached to the leading edge of an airfoil. They can be sequentially inflated and deflated to break away ice that has formed over their surface.

Deicing

Removing ice after it has formed.

Delamination

The separation of layers.

Delay Indefinite (Reason If Known) Expect Further Clearance

Used by ATC to inform a pilot when an accurate estimate of the delay time and the reason for the delay cannot immediately be determined; e.g., a disabled aircraft on the runway, terminal or center area saturation, weather below landing minimums, etc.

Delay Time

The amount of time that the arrival must lose to cross the meter fix at the assigned meter fix time. This is the difference between ACLT and VTA.

Delta

A Greek letter expressed by the symbol ∆ to indicate a change of values. As an example, ∆CG indicates a change (or movement) of the CG.

Delta ∆

This symbol, ∆, means a change in something. ∆CG means a change in the center of gravity location.

Demonstration-performance method

An educational presentation where an instructor first shows the student the correct way to perform an activity and then has the student attempt the same activity.

Density

(l) The ratio of the mass of any substance to the volume it occupies—weight per unit volume. (2) The ratio of any quantity to the volume or area it occupies, i.e., population per unit area, power density.

Density Altitude

This altitude is pressure altitude corrected for variations from standard temperature. When conditions are standard, pressure altitude and density altitude are the same. If the temperature is above standard, the density altitude is higher than pressure altitude. If the temperature is below standard, the density altitude is lower than pressure altitude. This is an important altitude because it is directly related to the airplane’s performance.

Density altitude

The altitude in the standard atmosphere at which the air has the same density as the air at the point in question. An aircraft will have the same performance characteristics as it would have in a standard atmosphere at this altitude.

Departure Center

The ARTCC having jurisdiction for the airspace that generates a flight to the impacted airport.

Departure Control

A function of an approach control facility providing air traffic control service for departing IFR and, under certain conditions, VFR aircraft.

Departure End of Runway (DER)

The end of runway available for the ground run of an aircraft departure. The end of the runway that is opposite the landing threshold, sometimes referred to as the stop end of the runway.

Departure procedure (DP)

Preplanned IFR ATC departure, published for pilot use, in textual and graphic format.

Departure Sequencing Program

A program designed to assist in achieving a specified interval over a common point for departures.

Departure Time

The time an aircraft becomes airborne.

Deposition

The direct transformation of a gas to a solid state, in which the liquid state is bypassed. Some sources use sublimation to describe this process instead of deposition.

Depression

In meteorology, an area of low pressure; a low or trough. This is usually applied to a certain stage in the development of a tropical cyclone, to migratory lows and troughs, and to upper-level lows and troughs that are only weakly developed.

DER

Departure End of The Runway

DER

Departure End of Runway

Descend Via

A descend via clearance instructs you to follow the altitudes published on a STAR. You are not authorized to leave your last assigned altitude unless specifically cleared to do so. If ATC amends the altitude or route to one that is different from the published procedure, the rest of the charted descent procedure is canceled. ATC will assign you any further route, altitude, or airspeed clearances, as necessary.

Description of the skill or behavior

The first part of a performance-based objective which explains the desired outcome of instruction in concrete terms that can be measured.

Designated Pilot Examiner (DPE)

An individual designated by the FAA to administer practical tests to pilot applicants.

Desired Course

Either True Course or Magnetic Course.

Desired Track

The planned or intended track between two waypoints. It is measured in degrees from either magnetic or true north. The instantaneous angle may change from point to point along the great circle track between waypoints.

Determiners

In test items, words which give a clue to the answer. Words such as “always” and “never” are determiners in true-false questions. Since absolutes are rare, such words usually make the statement false.

Detonation

The sudden release of heat energy from fuel in an aircraft engine caused by the fuel-air mixture reaching its critical pressure and temperature. Detonation occurs as a violent explosion rather than a smooth burning process.

Deviation

A magnetic compass error caused by local magnetic fields within the aircraft. Deviation error is different on each heading.

Deviation

A magnetic compass error caused by local magnetic fields within the aircraft. Deviation error is different on each heading.

Deviations

A. A departure from a current clearance, such as an off course maneuver to avoid weather or turbulence.
B. Where specifically authorized in the CFRs and requested by the pilot, ATC may permit pilots to deviate from certain regulations.

Dew

Water condensed onto grass and other objects near the ground, the temperatures of which have fallen below the initial dew point temperature of the surface air, but is still above freezing. Compare with frost.

Dew point (or dew-point temperature)

The temperature to which a sample of air must be cooled, while the mixing ratio and barometric pressure remain constant, in order to attain saturation with respect to water.

DF

Direction Finder

DF Approach Procedure

Used under emergency conditions where another instrument approach procedure cannot be executed. DF (Direction Finding) guidance for an instrument approach is given by ATC facilities with DF capability.

DF Fix

The geographical location of an aircraft obtained by one or more direction finders.

DF Guidance

Headings provided to aircraft by facilities equipped with direction finding equipment. These headings, if followed, will lead the aircraft to a predetermined point such as the DF station or an airport. DF guidance is given to aircraft in distress or to other aircraft which request the service. Practice DF guidance is provided when workload permits.

DF Steer

DF (Direction Finding) Guidance. Headings provided to aircraft by facilities equipped with direction finding equipment. These headings, if followed, will lead the aircraft to a predetermined point such as the DF station or an airport. DF guidance is given to aircraft in distress or to other aircraft which request the service. Practice DF guidance is provided when workload permits.

DGPS

Differential Global Positioning System.

DGPS

Differential Global Positioning System.

DH

Decision Height

Differential Ailerons

Control surface rigged such that the aileron moving up moves a greater distance than the aileron moving down. The up aileron produces extra parasite drag to compensate for the additional induced drag caused by the down aileron. This balancing of the drag forces helps minimize adverse yaw.

Differential Global Positioning System (DGPS)

A system that improves the accuracy of Global Navigation Satellite Systems (GNSS) by measuring changes in variables to provide satellite positioning corrections.

Differential Global Positioning System (DGPS)

A system that improves the accuracy of Global Navigation Satellite Systems (GNSS) by measuring changes in variables to provide satellite positioning corrections.

Differential pressure

A difference between two pressures. The measurement of airspeed is an example of the use of differential pressure.

Diffusion

Reducing the velocity of air causing the pressure to increase.

Digital ATIS (D-ATIS)

An alternative method of receiving ATIS reports by aircraft equipped with datalink services capable of receiving information in the cockpit over their Aircraft Communications Addressing and Reporting System (ACARS) unit.

Digital-Automatic Terminal Information Service (D-ATIS)

The service provides text messages to aircraft, airlines, and other users outside the standard reception range of conventional ATIS via landline and data link communications to the cockpit. Also, the service provides a computer-synthesized voice message that can be transmitted to all aircraft within range of existing transmitters. The Terminal Data Link System (TDLS) D-ATIS application uses weather inputs from local automated weather sources or manually entered meteorological data together with preprogrammed menus to provide standard information to users. Airports with D-ATIS capability are listed in the Airport/Facility Directory.

Dihedral

The positive acute angle between the lateral axis of an airplane and a line through the center of a wing or horizontal stabilizer. Dihedral contributes to the lateral stability of an airplane.

Diluter-demand oxygen system

An oxygen system that delivers oxygen mixed or diluted with air in order to maintain a constant oxygen partial pressure as the altitude changes.

Direct

Straight line flight between two navigational aids, fixes, points, or any combination thereof. When used by pilots in describing off-airway routes, points defining direct route segments become compulsory reporting points unless the aircraft is under radar contact.

Direct indication

The true and instantaneous reflection of aircraft pitch-and-bank attitude by the miniature aircraft, relative to the horizon bar of the attitude indicator.

Direct indication

The true and instantaneous reflection of aircraft pitch-and-bank attitude by the miniature aircraft, relative to the horizon bar of the attitude indicator.

Direct question

A question used for follow-up purposes, but directed at a specific individual.

Direct User Access Terminal System (DUATS)

A system that provides current FAA weather and flight plan filing services to certified civil pilots, via personal computer, modem, or telephone access to the system. Pilots can request specific types of weather briefings and other pertinent data for planned flights.

Direct User Access Terminal System (DUATS)

Direction Finder

A radio receiver equipped with a directional sensing antenna used to take bearings on a radio transmitter. Specialized radio direction finders are used in aircraft as air navigation aids. Others are ground-based, primarily to obtain a “fix” on a pilot requesting orientation assistance or to locate downed aircraft. A location “fix” is established by the intersection of two or more bearing lines plotted on a navigational chart using either two separately located Direction Finders to obtain a fix on an aircraft or by a pilot plotting the bearing indications of his/her DF on two separately located ground-based transmitters, both of which can be identified on his/her chart. UDFs receive signals in the ultra high frequency radio broadcast band; VDFs in the very high frequency band; and UVDFs in both bands. ATC provides DF service at those air traffic control towers and flight service stations listed in the Airport/Facility Directory and the DOD FLIP IFR En Route Supplement.

Directional Stability

Stability about the vertical axis of an aircraft, whereby an aircraft tends to return, on its own, to flight aligned with the relative wind when disturbed from that equilibrium state. The vertical tail is the primary contributor to directional stability, causing an airplane in flight to align with the relative wind.

Directly Behind

An aircraft is considered to be operating directly behind when it is following the actual flight path of the lead aircraft over the surface of the earth except when applying wake turbulence separation criteria.

Discontinuity

A zone with comparatively rapid transition of one or more meteorological elements.

Discrete Beacon Code

Discrete Code. [As used in the Air Traffic Control Radar Beacon System (ATCRBS), any one of the 4096 selectable Mode 3/A aircraft transponder codes except those ending in zero zero; e.g., discrete codes: 0010, 1201, 2317, 7777; nondiscrete codes: 0100, 1200, 7700. Nondiscrete codes are normally reserved for radar facilities that are not equipped with discrete decoding capability and for other purposes such as emergencies (7700), VFR aircraft (1200), etc.]

Discrete Code

As used in the Air Traffic Control Radar Beacon System (ATCRBS), any one of the 4096 selectable Mode 3/A aircraft transponder codes except those ending in zero zero; e.g., discrete codes: 0010, 1201, 2317, 7777; nondiscrete codes: 0100, 1200, 7700. Nondiscrete codes are normally reserved for radar facilities that are not equipped with discrete decoding capability and for other purposes such as emergencies (7700), VFR aircraft (1200), etc.

Discrete Frequency

A separate radio frequency for use in direct pilot-controller communications in air traffic control which reduces frequency congestion by controlling the number of aircraft operating on a particular frequency at one time. Discrete frequencies are normally designated for each control sector in en route/terminal ATC facilities. Discrete frequencies are listed in the Airport/Facility Directory and the DOD FLIP IFR En Route Supplement.

Discrimination

The degree to which a test distinguishes the differences between students.

Displaced Threshold

A threshold that is located at a point on the runway other than the designated beginning of the runway.

Distance circle

The circle depicted in the plan view of an IAP chart that typically has a 10 NM radius, within which chart the elements are drawn to scale. (also, reference circle)

Distance measuring equipment (DME)

A pulse-type electronic navigation system that shows the pilot, by an instrument-panel indication, the number of nautical miles between the aircraft and a ground station or waypoint.

Distance measuring equipment (DME)

A pulse-type electronic navigation system that shows the pilot, by an instrument-panel indication, the number of nautical miles between the aircraft and a ground station or waypoint.

Distant Early Warning Identification Zone (DEWIZ)

An ADIZ over the coastal waters of the State of Alaska.

Distractors

Incorrect responses to a multiple-choice test item.

Distress

A condition of being threatened by serious and/or imminent danger and of requiring immediate assistance.

Disturbance

In meteorology, applied rather loosely: (1) any low pressure or cyclone, but usually one that is relatively small in size; (2) an area where weather, wind, pressure, etc., show signs of cyclonic development; (3) any deviation in flow or pressure that is associated with a disturbed state of the weather, i.e., cloudiness and precipitation; and (4) any individual circulatory system within the primary circulation of the atmosphere.

Disuse

A theory of forgetting that suggests a person forgets those things that are not used.

Ditching

Emergency landing in water.

Diurnal

Daily, especially pertaining to a cycle completed within a 24-hour period, and which recurs every 24 hours.

Dive Brakes

Speed Brakes.

Divergence

The condition that exists when the distribution of winds within a given area is such that there is a net horizontal flow of air outward from the region. In divergence at lower levels, the resulting deficit is compensated for by subsidence of air from aloft; consequently the air is heated and the relative humidity lowered making divergence a warming and drying process. Low-level divergent regions are areas unfavorable to the occurrence of clouds and precipitation. The opposite of convergence.

Diverse Vector Area (DVA)

An airport may establish a diverse vector area if it is necessary to vector aircraft below the minimum vectoring altitude to assist in the efficient flow of departing traffic. DVA design requirements are outlined in TERPS and allow for the vectoring of aircraft immediately off the departure end of the runway below the MVA.

Diversion (DVRSN)

Flights that are required to land at other than their original destination for reasons beyond the control of the pilot/company, e.g. periods of significant weather.

DME

Distance Measuring Equipment.

DME

Distance Measuring Equipment

DME arc

A flight track that is a constant distance from the station or waypoint.

DME Fix

A geographical position determined by reference to a navigational aid which provides distance and azimuth information. It is defined by a specific distance in nautical miles and a radial, azimuth, or course (i.e., localizer) in degrees magnetic from that aid.

DME/N

Standard DME

DME/P

Precision DME

Doghouse

A turn-and-slip indicator dial mark in the shape of a doghouse.

Doghouse

A turn-and-slip indicator dial mark in the shape of a doghouse.

Doldrums

The equatorial belt of calm or light and variable winds between the two tradewind belts. Compare intertropical convergence zone.

Domestic Air Defense Identification Zone

An ADIZ within the United States along an international boundary of the United States.

Domestic Airspace

Airspace which overlies the continental land mass of the United States plus Hawaii and U.S. possessions. Domestic airspace extends to 12 miles offshore.

Domestic Reduced Vertical Separation Minimum (DRVSM)

Additional flight levels between FL 290 and FL 410 to provide operational, traffic, and airspace efficiency.

Domestic Reduced Vertical Separation Minimum (DRVSM)

Additional flight levels between FL 290 and FL 410 to provide operational, traffic, and airspace efficiency.

DOT

Department of Transportation

Double gimbal

A type of mount used for the gyro in an attitude instrument. The axes of the two gimbals are at right angles to the spin axis of the gyro, allowing free motion in two planes around the gyro.

Double gimbal

A type of mount used for the gyro in an attitude instrument. The axes of the two gimbals are at right angles to the spin axis of the gyro, allowing free motion in two planes around the gyro.

Downburst

A strong downdraft which induces an outburst of damaging winds on or near the ground. Damaging winds, either straight or curved, are highly divergent. The sizes of downbursts vary from 1/2 mile or less to more than 10 miles. An intense downburst often causes widespread damage. Damaging winds, lasting 5 to 30 minutes, could reach speeds as high as 120 knots.

Downdraft

A relative small scale downward current of air; often observed on the lee side of large objects restricting the smooth flow of the air or in precipitation areas in or near cumuliform clouds.

Downwash

Air deflected perpendicular to the motion of the airfoil.

Downwind Leg

A flight path parallel to the landing runway in the direction opposite to landing. The downwind leg normally extends between the crosswind leg and the base leg.

DP

Departure Procedure.

DPs

Departure Procedures

Drag

An aerodynamic force on a body acting parallel and opposite to the relative wind. The resistance of the atmosphere to the relative motion of an aircraft. Drag opposes thrust and limits the speed of the airplane.

Drag

The net aerodynamic force parallel to the relative wind, usually the sum of two components: induced drag and parasite drag.

Drag Chute

A parachute device installed on certain aircraft which is deployed on landing roll to assist in deceleration of the aircraft.

Drag Curve

A visual representation of the amount of drag of an aircraft at various airspeeds.

Drag curve

The curve created when plotting induced drag and parasite drag.

Drag curve

The curve created when plotting induced drag and parasite drag.

Drift Angle

Angle between heading and track.

Drift angle

Angle between heading and track.

Drifting snow

A type of hydrometeor composed of snow particles picked up from the surface, but carried to a height of less than 6 feet.

Drill and practice method

A time-honored training delivery method based on the learning principle that connections are strengthened with practice.

Drizzle

A form of precipitation. Very small water drops that appear to float with the air currents while falling in an irregular path (unlike rain, which falls in a comparatively straight path, and unlike fog droplets which remain suspended in the air).

Dropsonde

A radiosonde dropped by parachute from an aircraft to obtain soundings (measurements) of the atmosphere below.

DRT

Diversion Recovery Tool

DRVSM

Domestic Reduced Vertical Separation Minimums

DRVSM

Domestic Reduced Vertical Separation Minimum.

Dry adiabatic lapse rate

The rate of decrease of temperature with height when unsaturated air is lifted adiabatically (due to expansion as it is lifted to lower pressure).

Dry bulb

A name given to an ordinary thermometer used to determine temperature of the air; also used as a contraction for dry-bulb temperature. Compare wet bulb.

Dry-bulb temperature

The temperature of the air.

DSR

Display System Replacement

DT

Delay Time

DUATS

Direct User Access Terminal System (shut down May 16, 2018).

DUATS

Direct User Access Terminal System (shut down May 16, 2018).

Ducted-Fan Engine

An engine-propeller combination that has the propeller enclosed in a radial shroud. Enclosing the propeller improves the efficiency of the propeller.

Duplex

Transmitting on one frequency and receiving on a separate frequency.

Duplex

Transmitting on one frequency and receiving on a separate frequency.

Dust

A type of lithometeor composed of small earthen particles suspended in the atmosphere.

Dust devil

A small, vigorous whirlwind, usually of short duration, rendered visible by dust, sand, and debris picked up from the ground.

Dust storm (also called duster, black blizzard)

An unusual, frequently severe weather condition characterized by strong winds and dust-filled air over an extensive area.

Duster

Same as dust storm—an unusual, frequently severe weather condition characterized by strong winds and dust-filled air over an extensive area.

Dutch Roll

A combination of rolling and yawing oscillations that normally occurs when the dihedral effects of an aircraft are more powerful than the directional stability. Usually dynamically stable but objectionable in an airplane because of the oscillatory nature.

Duty Runway

Runway In Use/Active Runway/Duty Runway.

DVA

Diverse Vector Area

DVFR Flight Plan

A flight plan filed for a VFR aircraft which intends to operate in airspace within which the ready identification, location, and control of aircraft are required in the interest of national security.

DVRSN

Diversion

Dynamic

Continuous review, evaluation, and change to meet demands.

Dynamic Hydroplaning

A condition that exists when landing on a surface with standing water deeper than the tread depth of the tires. When the brakes are applied, there is a possibility that the brake will lock up and the tire will ride on the surface of the water, much like a water ski. When the tires are hydroplaning, directional control and braking action are virtually impossible. An effective anti-skid system can minimize the effects of hydroplaning.

Dynamic hydroplaning

Dynamic Load

The actual weight of the aircraft multiplied by the load factor, or the increase in weight caused by acceleration.

Dynamic Magnetic Variation

A field which is simply a computer model calculated value instead of a measured value contained in the record for a waypoint.

Dynamic Stability

The property of an aircraft that causes it, when disturbed from straight-and level flight, to develop forces or moments that restore the original condition of straight and level.

E-MSAW

En Route Minimum Safe Altitude Warning

Early ETOPS

ETOPS type design approval obtained without gaining non-ETOPS service experience on the candidate airplane-engine combination certified for ETOPS.

EAS

Equivalent Airspeed.

Echo

In radar, (1) the energy reflected or scattered by a target; (2) the radar scope presentation of the return from a target.

EDCT

Expect Departure Clearance Time

EDCT

Expect Departure Clearance Time. The time issued to a flight to indicate when it can expect to receive departure clearance. EDCTs are issued as part of Traffic Management Programs, such as a Ground Delay Program (GDP).

Eddy

A local irregularity of wind in a larger scale wind flow. Small scale eddies produce turbulent conditions.

Eddy current damping

The decreased amplitude of oscillations by the interaction of magnetic fields. In the case of a vertical card magnetic compass, flux from the oscillating permanent magnet produces eddy currents in a damping disk or cup. The magnetic flux produced by the eddy currents opposes the flux from the permanent magnet and decreases the oscillations.

Eddy currents

Current induced in a metal cup or disc when it is crossed by lines of flux from a moving magnet.

Eddy currents

Current induced in a metal cup or disc when it is crossed by lines of flux from a moving magnet.

EFAS

En Route Flight Advisory Service.

EFAS

En Route Flight Advisory Service

EFB

Electronic Flight Bag

EFC

Expect-Further-Clearance.

EFD

Electronic Flight Display.

Effect

A principle of learning that learning is strengthened when accompanied by a pleasant or satisfying feeling, and that learning is weakened when associated with an unpleasant feeling.

EFIS

Electronic Flight Information System

EFV

Enhanced Flight Visibility

EFVS

Enhanced Flight Vision System.

EGPWS

Enhanced Ground Proximity Warning Systems

EGT

Exhaust Gas Temperature.

EICAS

Engine Indicating and Crew Alerting System

Electrical Bus

A Bus Bar. An electrical power distribution point to which several circuits may be connected. It is often a solid metal strip having a number of terminals installed on it.

Electrohydraulic

Hydraulic control which is electrically actuated.

Electronic Flight Bag (EFB)

An electronic display system intended primarily for cockpit or cabin use. EFB devices can display a variety of aviation data or perform basic calculations (e.g., performance data, fuel calculations, etc.). In the past, some of these functions were traditionally accomplished using paper references or were based on data provided to the flight crew by an airlines flight dispatch function. The scope of the EFB system functionality may also include various other hosted databases and applications. Physical EFB displays may use various technologies, formats, and forms of communication. These devices are sometimes referred to as auxiliary performance computers (APC) or laptop auxiliary performance computers (LAPC).

Electronic flight display (EFD)

For the purpose of standardization, any flight instrument display that uses LCD or other image-producing system (Cathode Ray Tube [CRT], etc.)

Electronic flight display (EFD)

For the purpose of standardization, any flight instrument display that uses LCD or other image-producing system (cathode ray tube (CRT), etc.).

Element of threat

A perception factor that describes how a person is unlikely to easily comprehend an event if that person is feeling threatened since most of a person’s effort is focused on whatever is threatening them.

Elevator

The horizontal, movable primary control surface in the tail section, or empennage, of an airplane. The elevator is hinged to the trailing edge of the fixed horizontal stabilizer.

Elevator

The horizontal, movable primary control surface in the tail section, or empennage, of an airplane. The elevator is hinged to the trailing edge of the fixed horizontal stabilizer.

Elevator illusion

The sensation of being in a climb or descent, caused by the kind of abrupt vertical accelerations that result from up- or downdrafts.

Elevator illusion

The sensation of being in a climb or descent, caused by the kind of abrupt vertical accelerations that result from up- or downdrafts.

Ellipsoid of Revolution

The surface that results when an ellipse is rotated about one of its axes.

ELT

Emergency Locator Transmitter

EM wave

Electromagnetic wave.

EM wave

Electromagnetic wave.

EMAS

Engineered Materials Arresting System

EMERG

Emergency

A distress or urgent condition.

Emergency

A distress or urgent condition.

Emergency Locator Transmitter

A radio transmitter attached to the aircraft structure which operates from its own power source on 121.5 MHz and 243.0 MHz. It aids in locating downed aircraft by radiating a downward sweeping audio tone, 2-4 times per second. It is designed to function without human action after an accident. [The 121.5 band is no longer monitored by satellite. The newest version uses 406.0MHz]

Emergency Safe Altitudes

Altitudes depicted on approach charts which provide at least 1,000 feet of obstacle clearance in nonmountainous areas and 2,000 feet of obstacle clearance in designated mountainous areas within a 100-mile radius of the navigation facility upon which the procedure is predicated and normally used only in military procedures. These altitudes are identified on published procedures as “Emergency Safe Altitudes.”

Empennage

The section of the airplane that consists of the vertical stabilizer, the horizontal stabilizer, and the associated control surfaces.

Empennage

The section of the airplane that consists of the vertical stabilizer, the horizontal stabilizer, and the associated control surfaces.

Emphasis error

The result of giving too much attention to a particular instrument during the cross-check, instead of relying on a combination of instruments necessary for attitude and performance information.

Emphasis error

The result of giving too much attention to a particular instrument during the cross-check, instead of relying on a combination of instruments necessary for attitude and performance information.

Empty Weight

The weight of the airframe, engines, all permanently installed equipment, and unusable fuel. Depending upon the part of the federal regulations under which the aircraft was certificated, either the undrainable oil or full reservoir of oil is included.

Empty-field myopia

Induced nearsightedness that is associated with flying at night, in instrument meteorological conditions and/or reduced visibility. With nothing to focus on, the eyes automatically focus on a point just slightly ahead of the airplane.

Empty-weight Center of Gravity (EWCG)

This is the center of gravity of the aircraft in the empty condition, containing only the items specified in the aircraft empty weight. This CG is an essential part of the weight and balance record of the aircraft.

Empty-weight Center of Gravity Range

The distance between the allowable forward and aft empty-weight CG limits.

EMS

Emergency Medical Service

En Route Air Traffic Control Services

Air traffic control service provided aircraft on IFR flight plans, generally by centers, when these aircraft are operating between departure and destination terminal areas. When equipment, capabilities, and controller workload permit, certain advisory/assistance services may be provided to VFR aircraft.

En Route Automation System (EAS)

The complex integrated environment consisting of situation display systems, surveillance systems and flight data processing, remote devices, decision support tools, and the related communications equipment that form the heart of the automated IFR air traffic control system. It interfaces with automated terminal systems and is used in the control of en route IFR aircraft.

En Route Charts

Aeronautical Chart.

En Route Descent

Descent from the en route cruising altitude which takes place along the route of flight.

En route facilities ring

Depicted in the plan view of IAP charts, a circle which designates NAVAIDs, fixes, and intersections that are part of the en route low altitude airway structure.

En Route Flight Advisory Service

A service specifically designed to provide, upon pilot request, timely weather information pertinent to his/her type of flight, intended route of flight, and altitude. The FSSs providing this service are listed in the Airport/Facility Directory.

En Route Flight Advisory Service (EFAS)

An en route weather-only AFSS service.

En Route Flight Advisory Service (EFAS)

An en route weather-only AFSS service.

En Route High Altitude Charts

Provide aeronautical information for en route instrument navigation (IFR) in the high altitude stratum. Information includes the portrayal of jet routes, identification and frequencies of radio aids, selected airports, distances, time zones, special use airspace, and related information.

En route high-altitude charts

Aeronautical charts for en route instrument navigation at or above 18,000 feet MSL.

En route high-altitude charts

Aeronautical charts for en route instrument navigation at or above 18,000 feet MSL.

En Route Low Altitude Charts

Provide aeronautical information for en route instrument navigation (IFR) in the low altitude stratum. Information includes the portrayal of airways, limits of controlled airspace, position identification and frequencies of radio aids, selected airports, minimum en route and minimum obstruction clearance altitudes, airway distances, reporting points, restricted areas, and related data. Area charts, which are a part of this series, furnish terminal data at a larger scale in congested areas.

En route low-altitude charts

Aeronautical charts for en route IFR navigation below 18,000 feet MSL.

En route low-altitude charts

Aeronautical charts for en route IFR navigation below 18,000 feet MSL.

En Route Minimum Safe Altitude Warning

A function of the EAS that aids the controller by providing an alert when a tracked aircraft is below or predicted by the computer to go below a predetermined minimum IFR altitude (MIA).

En Route Obstacle Clearance Areas

Obstacle clearance areas for en route planning are identified as primary, secondary, and turning areas, and they are designed to provide obstacle clearance route protection width for airways and routes.

En Route Transition

A. Conventional STARs/SIDs. The portion of a SID/STAR that connects to one or more en route airway/jet route.
B. RNAV STARs/SIDs. The portion of a STAR preceding the common route or point, or for a SID the portion following, that is coded for a specific en route fix, airway or jet route.

Encoding altimeter

A special type of pressure altimeter used to send a signal to the air traffic controller on the ground, showing the pressure altitude the aircraft is flying.

Encoding altimeter

A special type of pressure altimeter used to send a signal to the air traffic controller on the ground, showing the pressure altitude the aircraft is flying.

Engine Pressure Ratio (EPR)

The ratio of turbine discharge pressure divided by compressor inlet pressure that is used as an indication of the amount of thrust being developed by a turbine engine.

Enhanced flight visibility (EFV)

The average forward horizontal distance, from the cockpit of an aircraft in flight, at which prominent topographical objects may be clearly distinguished and identified by day or night by a pilot using an enhanced flight vision system.

Enhanced flight vision system (EFVS)

An electronic means to provide a display of the forward external scene topography (the natural or manmade features of a place or region especially in a way to show their relative positions and elevation) through the use of imaging sensors, such as a forward looking infrared, millimeter wave radiometry, millimeter wave radar, low light level image intensifying.

Environmental Systems

In an aircraft, the systems, including the supplemental oxygen systems, air conditioning systems, heaters, and pressurization systems, which make it possible for an occupant to function at high altitude.

EPE

Estimated Position Error

EPE

Estimate of Position Error

EPR

Engine Pressure Ratio.

Equi-Time Point

A point on the route of flight where the flight time, considering wind, to each of two selected airports is equal.

Equilibrium

A condition that exists within a body when the sum of the moments of all of the forces acting on the body is equal to zero. In aerodynamics, equilibrium is when all opposing forces acting on an aircraft are balanced (steady, unaccelerated flight conditions).

EQUIP

Equipment

Equipment List

A list of items approved by the FAA for installation in a particular aircraft. The list includes the name, part number, weight, and arm of the component. Installation or removal of an item in the equipment list is considered to be a minor alteration.

Equivalent airspeed

Airspeed equivalent to CAS in standard atmosphere at sea level. As the airspeed and pressure altitude increase, the CAS becomes higher than it should be, and a correction for compression must be subtracted from the CAS.

Equivalent airspeed

Equivalent Shaft Horsepower (ESHP)

A measurement of the total horsepower of a turboprop engine, including that provided by jet thrust.

ER-OPS

Extended Range Operations

Established

To be stable or fixed on a route, route segment, altitude, heading, etc.

Estimated ceiling

A ceiling classification applied when the ceiling height has been estimated by the observer or has been determined by some other method; but, because of the specified limits of time, distance, or precipitation conditions, a more descriptive classification cannot be applied.

Estimated Elapsed Time [ICAO]

The estimated time required to proceed from one significant point to another.

Estimated Off-Block Time [ICAO]

The estimated time at which the aircraft will commence movement associated with departure.

Estimated Position Error (EPE)

A measure of the current estimated navigational performance. Also referred to as Actual Navigation Performance (ANP).

Estimated Time En Route

The estimated flying time from departure point to destination (lift-off to touchdown).

Estimated Time Of Arrival

The time the flight is estimated to arrive at the gate (scheduled operators) or the actual runway on times for nonscheduled operators.

ESV

Expanded Service Volume

ETA

Estimated Time of Arrival

ETA

Estimated Time of Arrival

ETD

Estimated Time of Departure

ETE

Estimated Time En Route

ETOPS

Extended Operations.

ETOPS Significant System

An airplane system, including the propulsion system, the failure or malfunctioning of which could adversely affect the safety of an ETOPS flight, or the continued safe flight and landing of an airplane during an ETOPS diversion. Each ETOPS significant system is either an ETOPS group 1 significant system or an ETOPS group 2 significant system.
(1) An ETOPS group 1 Significant System—
(i) Has fail-safe characteristics directly linked to the degree of redundancy provided by the number of engines on the airplane.
(ii) Is a system, the failure or malfunction of which could result in an IFSD, loss of thrust control, or other power loss.
(iii) Contributes significantly to the safety of an ETOPS diversion by providing additional redundancy for any system power source lost as a result of an inoperative engine.
(iv) Is essential for prolonged operation of an airplane at engine inoperative altitudes.
(2) An ETOPS group 2 significant system is an ETOPS significant system that is not an ETOPS group 1 significant system.

Evaporation

The change of liquid water to water vapor.

EWINS

Enhanced Weather Information System

Execute Missed Approach

Instructions issued to a pilot making an instrument approach which means continue inbound to the missed approach point and execute the missed approach procedure as described on the Instrument Approach Procedure Chart or as previously assigned by ATC. The pilot may climb immediately to the altitude specified in the missed approach procedure upon making a missed approach. No turns should be initiated prior to reaching the missed approach point. When conducting an ASR or PAR approach, execute the assigned missed approach procedure immediately upon receiving instructions to “execute missed approach.”

Exercise

A principle of learning emphasizing that those things most often repeated are best remembered.

Exhaust

The rear opening of a turbine engine exhaust duct. The nozzle acts as an orifice, the size of which determines the density and velocity of the gases as they emerge from the engine.

Exhaust Gas Temperature (EGT)

The temperature of the exhaust gases as they leave the cylinders of a reciprocating engine or the turbine section of a turbine engine.

Exhaust Manifold

The part of the engine that collects exhaust gases leaving the cylinders.

Expanded Service Volume

When ATC or a procedures specialist requires the use of a NAVAID beyond the limitations specified for standard service volume, an expanded service volume (ESV) may be established. See standard service volume.

Expect (Altitude) At (Time) Or (Fix)

Used under certain conditions to provide a pilot with an altitude to be used in the event of two-way communications failure. It also provides altitude information to assist the pilot in planning.

Expect Departure Clearance Time (EDCT)

The runway release time assigned to an aircraft in a traffic management program and shown on the flight progress strip as an EDCT.

Expect Further Clearance (Time)

The time a pilot can expect to receive clearance beyond a clearance limit.

Expect Further Clearance Via (Airways, Routes Or Fixes)

Used to inform a pilot of the routing he/she can expect if any part of the route beyond a short range clearance limit differs from that filed.

Expedite

Used by ATC when prompt compliance is required to avoid the development of an imminent situation. Expedite climb/descent normally indicates to a pilot that the approximate best rate of climb/descent should be used without requiring an exceptional change in aircraft handling characteristics.

Explosive decompression

A change in cabin pressure faster than the lungs can decompress. Lung damage is possible.

Extended Operations (ETOPS)

An airplane flight operation, other than an all-cargo operation in an airplane with more than two engines, during which a portion of the flight is conducted beyond a time threshold identified in part 121 or part 135 of this chapter that is determined using an approved one-engine-inoperative cruise speed under standard atmospheric conditions in still air.

Extended over-water operation

(1) With respect to aircraft other than helicopters, an operation over water at a horizontal distance of more than 50 nautical miles from the nearest shoreline; and
(2) With respect to helicopters, an operation over water at a horizontal distance of more than 50 nautical miles from the nearest shoreline and more than 50 nautical miles from an off-shore heliport structure.

External load

A load that is carried, or extends, outside of the aircraft fuselage.

External-load attaching

Means the structural components used to attach an external load to an aircraft, including external-load containers, the backup structure at the attachment points, and any quick-release device used to jettison the external load.

Extratropical low (sometimes called extratropical cyclone, extra

Any cyclone that is not a tropical cyclone, usually referring to the migratory frontal cyclones of middle and high latitudes.

Eye

The roughly circular area of calm or relatively light winds and comparatively fair weather at the center of a well-developed tropical cyclone. A wall cloud marks the outer boundary of the eye.

FA

Area Forecast (Discontinued, replaced by Graphical Forecasts for Aviation)

FA

Area Forecast. (Discontinued, replaced by Graphical Forecasts for Aviation)

FAA

Federal Aviation Administration.

FAASTeam

Federal Aviation Administration Safety Team.

FAASTeam Program Manager

The person who designs, implements, and evaluates the FAASTeam within the FAA flight standards district office (FSDO) area of responsibility.

FAASTeam Representative

A volunteer within the aviation community who shares technical expertise and professional knowledge as a part of the FAASTeam.

FAF

Final Approach Fix.

Fahrenheit temperature scale (abbreviated F)

A temperature scale with 32 degrees as the melting point of pure ice and 212 degrees as the boiling point of pure water at standard sea level atmospheric pressure (29.92 inches or 1013.2 millibars).

Fall wind

A cold wind blowing downslope. Fall wind differs from foehn in that the air is initially cold enough to remain relatively cold despite compressional heating during descent.

False Horizon

An optical illusion where the pilot confuses a row of lights along a road or other straight line as the horizon.

False horizon

Inaccurate visual information for aligning the aircraft, caused by various natural and geometric formations that disorient the pilot from the actual horizon.

False Start

Hung Start. In gas turbine engines, a condition of normal light off but with r.p.m. remaining at some low value rather than increasing to the normal idle r.p.m. This is often the result of insufficient power to the engine from the starter. In the event of a hung start, the engine should be shut down.

FAP

Final Approach Point

FAROS

Final Approach Runway Occupancy Signal

Fast File

A system whereby a pilot files a flight plan via telephone that is tape recorded and then transcribed for transmission to the appropriate air traffic facility. Locations having a fast file capability are contained in the Airport/Facility Directory. (Alaska only.)

FATO

Final Approach and Takeoff Area

FAWP

Final Approach Waypoint

FB

Fly-By

FB

Fly-by

FBWP

Fly-By Waypoint

FCC

Federal Communications Commission

FD

Winds and Temperatures Aloft Forecast

FD

Flight Director

FD

Flight Director System

FDC

Flight Data Center

FDC NOTAM

Flight Data Center Notice To Airmen

FDE

Fault Detection and Exclusion

FDI

Flight Director Indicator.

FDP

Flight Data Processing

FEA/FCA

Flow Evaluation Area (FEA) / Flow Constrained Area (FCA) - FEA/FCAs provide reroutes using the Create Reroute capability and are published through a reroute advisory with an optional flight list attached. Stakeholders can monitor FEA/FCAs through reroute monitor in traffic situation display (TSD), web situation display (WSD) or collaborative constraint situation display (CCSD).

Feathered Propeller

A propeller whose blades have been rotated so that the leading and trailing edges are nearly parallel with the aircraft flight path to stop or minimize drag and engine rotation. Normally used to indicate shutdown of a reciprocating or turboprop engine due to malfunction.

Feathering Propeller (Feathered)

A controllable pitch propeller with a pitch range sufficient to allow the blades to be turned parallel to the line of flight to reduce drag and prevent further damage to an engine that has been shut down after a malfunction.

Federal airways

Class E airspace areas that extend upward from 1,200 feet to, but not including, 18,000 feet MSL, unless otherwise specified.

Federal airways

Class E airspace areas that extend upward from 1,200 feet to, but not including, 18,000 feet MSL, unless otherwise specified.

Federal Aviation Administration Safety Team (FAASTeam)

An organization promoting safety standards and the reduction of aircraft related accidents. Each of the eight FAA Flight Standards regions have a dedicated FAASTeam office.

Feeder facilities

Used by ATC to direct aircraft to intervening fixes between the en route structure and the initial approach fix.

Feeder Fix

The fix depicted on Instrument Approach Procedure Charts which establishes the starting point of the feeder route.

Feeder Route

A feeder route is a route depicted on IAP charts to designate courses for aircraft to proceed from the en route structure to the IAF. Feeder routes, also referred to as approach transitions, technically are not considered approach segments but are an integral part of many IAPs.

Ferry Flight

A flight for the purpose of: a. Returning an aircraft to base. b. Delivering an aircraft from one location to another. c. Moving an aircraft to and from a maintenance base. Ferry flights, under certain conditions, may be conducted under terms of a special flight permit.

FFS

Full Flight Simulator.

Field Elevation

Airport Elevation. The highest point of an airport’s usable runways measured in feet from mean sea level.

Filed

Normally used in conjunction with flight plans, meaning a flight plan has been submitted to ATC.

Filed Flight Plan

The flight plan as filed with an ATS unit by the pilot or his/her designated representative without any subsequent changes or clearances.

Filling

An increase in the central pressure of a pressure system; opposite of deepening; more commonly applied to a low rather than a high.

Final

Commonly used to mean that an aircraft is on the final approach course or is aligned with a landing area.

Final approach

Part of an instrument approach procedure in which alignment and descent for landing are accomplished.

Final Approach

A flight path in the direction of landing along the extended runway centerline. The final approach normally extends from the base leg to the runway. An aircraft making a straight-in approach VFR is also considered to be on final approach.

Final Approach

The segment between the final approach fix or point and the runway, airport, or missed approach point.

Final Approach and Takeoff Area (FATO)

The FATO is a defined heliport area over which the final approach to a hover or a departure is made. The touchdown and lift-off area (TLOF) where the helicopter is permitted to land is normally centered in the FATO. A safety area is provided around the FATO.

Final Approach Course

A bearing/radial/track of an instrument approach leading to a runway or an extended runway centerline all without regard to distance.

Final Approach Fix

The fix from which the final approach (IFR) to an airport is executed and which identifies the beginning of the final approach segment. It is designated on Government charts by the Maltese Cross symbol for nonprecision approaches and the lightning bolt symbol for precision approaches; or when ATC directs a lower-than-published glideslope/path intercept altitude, it is the resultant actual point of the glideslope/path intercept.

Final Approach Point

The point, applicable only to a nonprecision approach with no depicted FAF (such as an on airport VOR), where the aircraft is established inbound on the final approach course from the procedure turn and where the final approach descent may be commenced. The FAP serves as the FAF and identifies the beginning of the final approach segment.

Final Approach Runway Occupancy Signal (FAROS)

The Final Approach Runway Occupancy Signal (FAROS) is an automated safety system designed to notify pilots on approach to land that the runway is occupied or otherwise unsafe for landing. This pilot notification system is an FAA sponsored research and development effort that addresses the high priority safety hazards of runway incursions.

Final Approach Segment

Segments Of An Instrument Approach Procedure.

Final Approach [ICAO]

That part of an instrument approach procedure which commences at the specified final approach fix or point, or where such a fix or point is not specified. a. At the end of the last procedure turn, base turn or inbound turn of a racetrack procedure, if specified; or b. At the point of interception of the last track specified in the approach procedure; and ends at a point in the vicinity of an aerodrome from which: 1. A landing can be made; or 2. A missed approach procedure is initiated.

Final takeoff speed

The speed of the airplane that exists at the end of the takeoff path in the en route configuration with one engine inoperative.

FIR

Flight Information Region

FIR

Flight Information Region

Fire resistant

(1) With respect to sheet or structural members, the capacity to withstand the heat associated with fire at least as well as aluminum alloy in dimensions appropriate for the purpose for which they are used; and
(2) With respect to fluid-carrying lines, fluid system parts, wiring, air ducts, fittings, and powerplant controls, the capacity to perform the intended functions under the heat and other conditions likely to occur when there is a fire at the place concerned.

Fireproof

(1) With respect to materials and parts used to confine fire in a designated fire zone, the capacity to withstand at least as well as steel in dimensions appropriate for the purpose for which they are used, the heat produced when there is a severe fire of extended duration in that zone; and
(2) With respect to other materials and parts, the capacity to withstand the heat associated with fire at least as well as steel in dimensions appropriate for the purpose for which they are used.

First gust

The leading edge of the spreading downdraft, plow wind, from an approaching thunderstorm.

FIS

Flight Information System

FIS

Flight Information Service

FIS-B

Flight Information Service Broadcast

FISDL

Flight Information Services Data Link

FISDL

Flight Information Services Data Link

Fix

A geographical position determined by visual reference to the surface, by reference to one or more radio NAVAIDs, by celestial plotting, or by another navigational device. Note:Fix is a generic name for a geographical position and is referred to as a fix, waypoint, intersection, reporting point, etc.

Fix

A geographical position determined by visual reference to the surface, by reference to one or more radio NAVAIDs, by celestial plotting, or by another navigational device.

Fixating

Staring at a single instrument, thereby interrupting the cross-check process.

Fixating

Staring at a single instrument, thereby interrupting the cross-check process.

Fixation

A psychological condition where the pilot fixes attention on a single source of information and ignores all other sources.

Fixed Shaft Turboprop Engine

A turboprop engine where the gas producer spool is directly connected to the output shaft.

Fixed slot

A fixed, nozzle shaped opening near the leading edge of a wing that ducts air onto the top surface of the wing. Its purpose is to increase lift at higher angles of attack.

Fixed-Pitch Propellers

Propellers with fixed blade angles. Fixed-pitch propellers are designed as climb propellers, cruise propellers, or standard propellers.

FL

Flight Level.

Flag

A warning device incorporated in certain airborne navigation and flight instruments indicating that: a. Instruments are inoperative or otherwise not operating satisfactorily, or b. Signal strength or quality of the received signal falls below acceptable values.

Flame resistant

Not susceptible to combustion to the point of propagating a flame, beyond safe limits, after the ignition source is removed.

Flameout

A condition in the operation of a gas turbine engine in which the fire in the engine goes out due to either too much or too little fuel sprayed into the combustors.

Flammable

With respect to a fluid or gas, susceptible to igniting readily or to exploding.

Flap extended speed

The highest speed permissible with wing flaps in a prescribed extended position.

Flaps

Hinged portion of the trailing edge between the ailerons and fuselage. In some aircraft, ailerons and flaps are interconnected to produce full-span “flaperons.” In either case, flaps change the lift and drag on the wing.

Flaps

Hinged portion of the trailing edge between the ailerons and fuselage. In some aircraft ailerons and flaps are interconnected to produce full-span “flaperons.” In either case, flaps change the lift and drag on the wing.

Flash resistant

Not susceptible to burning violently when ignited.

Flat Pitch

A propeller configuration when the blade chord is aligned with the direction of rotation.

Fleet Weight

An average weight accepted by the FAA for aircraft of identical make and model that have the same equipment installed. When a fleet weight control program is in effect, the fleet weight of the aircraft can be used rather than every individual aircraft having to be weighed.

Flicker Vertigo

A disorientating condition caused from flickering light off the blades of the propeller.

Flight Check

A call-sign prefix used by FAA aircraft engaged in flight inspection/certification of navigational aids and flight procedures. The word “recorded” may be added as a suffix; e.g., “Flight Check 320 recorded” to indicate that an automated flight inspection is in progress in terminal areas.

Flight configurations

Adjusting the aircraft control surfaces (including flaps and landing gear) in a manner that will achieve a specified attitude.

Flight configurations

Adjusting the aircraft control surfaces (including flaps and landing gear) in a manner that will achieve a specified attitude.

Flight Director

An automatic flight control system in which the commands needed to fly the airplane are electronically computed and displayed on a flight instrument. The commands are followed by the human pilot with manual control inputs or, in the case of an autopilot system, sent to servos that move the flight controls.

Flight director indicator (FDI)

One of the major components of a flight director system, it provides steering commands that the pilot (or the autopilot, if coupled) follows.

Flight director indicator(FDI)

One of the major components of a flight director system, it provides steering commands that the pilot (or the autopilot, if coupled) follows.

Flight Following

Traffic Advisories.

Flight Idle

Engine speed, usually in the 70-80 percent range, for minimum flight thrust.

Flight Information Region (FIR)

A FIR is an airspace of defined dimensions within which Flight Information Service and Alerting Service are provided. Flight Information Service (FIS) is a service provided for the purpose of giving advice and information useful for the safe and efficient conduct of flights. Alerting Service is a service provided to notify appropriate organizations regarding aircraft in need of search and rescue aid, and assist such organizations as required.

Flight Information Service

A service provided for the purpose of giving advice and information useful for the safe and efficient conduct of flights.

Flight Information Service-Broadcast (FIS-B)

A ground broadcast service provided through the ADS-B Broadcast Services network over the UAT data link that operates on 978 MHz. The FIS-B system provides pilots and flight crews of properly equipped aircraft with a cockpit display of certain aviation weather and aeronautical information.

Flight Inspection

Inflight investigation and evaluation of a navigational aid to determine whether it meets established tolerances.

Flight Level

A level of constant atmospheric pressure related to a reference datum of 29.92 inches of mercury. Each is stated in three digits that represent hundreds of feet. For example, flight level (FL) 250 represents a barometric altimeter indication of 25,000 feet; FL 255, an indication of 25,500 feet.

Flight Level (FL)

A flight level is a level of constant atmospheric pressure related to a reference datum of 29.92 in.Hg. Each flight level is stated in three digits that represents hundreds of feet. For example, FL 250 represents an altimeter indication of 25,000 feet.

Flight management system (FMS)

Provides pilot and crew with highly accurate and automatic long-range navigation capability, blending available inputs from long- and short- range sensors.

Flight management system (FMS)

Provides pilot and crew with highly accurate and automatic long-range navigation capability, blending available inputs from long- and short- range sensors.

Flight Management System Procedure

An arrival, departure, or approach procedure developed for use by aircraft with a slant (/) E or slant (/) F equipment suffix.

Flight Management Systems

A computer system that uses a large data base to allow routes to be preprogrammed and fed into the system by means of a data loader. The system is constantly updated with respect to position accuracy by reference to conventional navigation aids. The sophisticated program and its associated data base insures that the most appropriate aids are automatically selected during the information update cycle.

Flight path

The line, course, or track along which an aircraft is flying or is intended to be flown.

Flight path

The line, course, or track along which an aircraft is flying or is intended to be flown.

Flight patterns

Basic maneuvers, flown by reference to the instruments rather than outside visual cues, for the purpose of practicing basic attitude flying. The patterns simulate maneuvers encountered on instrument flights such as holding patterns, procedure turns, and approaches.

Flight patterns

Flight Plan

Specified information relating to the intended flight of an aircraft that is filed orally or in writing with an FSS or an ATC facility.

Flight Recorder

A general term applied to any instrument or device that records information about the performance of an aircraft in flight or about conditions encountered in flight. Flight recorders may make records of airspeed, outside air temperature, vertical acceleration, engine RPM, manifold pressure, and other pertinent variables for a given flight.

Flight review

A 14 CFR 61.56 requirement designed to assess and update a pilot’s knowledge and skills.

Flight Service Station (FSS)

An air traffic facility which provides pilot briefings, flight plan processing, en route radio communications, search and rescue services, and assistance to lost aircraft and aircraft in emergency situations. FSSs also relay ATC clearances, process Notices to Airmen, broadcast aviation weather and aeronautical information, and notify Customs and Border Protection of transborder flights. In addition, at selected locations, FSSs provide En Route Flight Advisory Service (Flight Watch) and Airport Advisory Service (AAS). In Alaska, designated FSSs also provide TWEB recordings and take weather observations.

Flight simulation training device (FSTD)

A flight simulator or a flight training device.

Flight Standards District Office

An FAA field office serving an assigned geographical area and staffed with Flight Standards personnel who serve the aviation industry and the general public on matters relating to the certification and operation of air carrier and general aviation aircraft. Activities include general surveillance of operational safety, certification of airmen and aircraft, accident prevention, investigation, enforcement, etc.

Flight strips

Paper strips containing instrument flight information, used by ATC when processing flight plans.

Flight Test

A flight for the purpose of: a. Investigating the operation/flight characteristics of an aircraft or aircraft component. b. Evaluating an applicant for a pilot certificate or rating.

Flight time

(1) Pilot time that commences when an aircraft moves under its own power for the purpose of flight and ends when the aircraft comes to rest after landing; or
(2) For a glider without self-launch capability, pilot time that commences when the glider is towed for the purpose of flight and ends when the glider comes to rest after landing.

Flight training device (FTD)

A replica of aircraft instruments, equipment, panels, and controls in an open flight deck area or an enclosed aircraft cockpit replica. It includes the equipment and computer programs necessary to represent aircraft (or set of aircraft) operations in ground and flight conditions having the full range of capabilities of the systems installed in the device as described in part 60 of this chapter and the qualification performance standard (QPS) for a specific FTD qualification level.

Flight Visibility

The average forward horizontal distance, from the cockpit of an aircraft in flight, at which prominent unlighted objects may be seen and identified by day and prominent lighted objects may be seen and identified by night.

Flight Visibility [ICAO]

The visibility forward from the cockpit of an aircraft in flight.

Flight Watch

A shortened term for use in air-ground contacts to identify the flight service station providing En Route Flight Advisory Service; e.g., “Oakland Flight Watch.”

Flightcrew member

A pilot, flight engineer, or flight navigator assigned to duty in an aircraft during flight time.

Floating

A condition when landing where the airplane does not settle to the runway due to excessive airspeed.

Floating Waypoints

Floating waypoints represent airspace fixes at a point in space not directly associated with a conventional airway. In many cases they may be established for such purposes as ATC metering fixes, holding points, RNAV-direct routing, gateway waypoints, STAR origination points leaving the en route structure, and SID terminating points joining the en route structure.

Floor load limit

The maximum weight the floor can sustain per square inch/foot as provided by the manufacturer.

Flow line

A streamline.

Fly Heading (Degrees)

Informs the pilot of the heading he/she should fly. The pilot may have to turn to, or continue on, a specific compass direction in order to comply with the instructions. The pilot is expected to turn in the shorter direction to the heading unless otherwise instructed by ATC.

Fly Visual To Airport

Published Instrument Approach Procedure Visual Segment.

Fly-By (FB) Waypoint

A waypoint that requires the use of turn anticipation to avoid overshooting the next flight segment.

Fly-Over (FO) Waypoint

A waypoint that precludes any turn until the waypoint is overflown, and is followed by either an intercept maneuver of the next flight segment or direct flight to the next waypoint.

FM

Fan Marker.

FMC

Flight Management Computer

FMS

Flight Management System.

FMS

Flight Management System

FMSP

Flight Management System Procedure

FO

Fly-Over

FOD

Foreign Object Damage.

Foehn

A warm, dry downslope wind; the warmness and dryness being due to adiabatic compression upon descent; characteristic of mountainous regions. Also known as a Chinook in the Rockies and Santa Ana winds in Southern California and Northern Baja.

Fog

A hydrometeor consisting of numerous minute water droplets and based at the surface; droplets are small enough to be suspended in the earth’s atmosphere indefinitely. (Unlike driv:.le, it does not fall to the surface; differs from cloud only in that a cloud is not based at the surface; distinguished from haze by its wetness and gray color.)

Fog

Cloud consisting of numerous minute water droplets and based at the surface; droplets are small enough to be suspended in the earth’s atmosphere indefinitely. (Unlike drizzle, it does not fall to the surface. Fog differs from a cloud only in that a cloud is not based at the surface, and is distinguished from haze by its wetness and gray color.).

Follow-up question

In the guided discussion method, a question used by an instructor to get the discussion back on track or to get the students to explain something more thoroughly.

FOM

Flight Operations Manual

Force (F)

The energy applied to an object that attempts to cause the object to change its direction, speed, or motion. In aerodynamics, it is expressed as F, T (thrust), L (lift), W (weight), or D (drag), usually in pounds.

Force (F)

Forecast Icing Conditions

Environmental conditions expected by an NWS or an FAA-approved weather provider to be conducive to the formation of in-flight icing on aircraft.

Forecast Icing Product (FIP)

The FIP examines numerical weather prediction model output to calculate the probability and severity of icing conditions, plus SLD potential. This product is automatically produced with no human modification. More information can be found on the AWC ADDS Web site.

Foreign air carrier

Any person other than a citizen of the United States, who undertakes directly, by lease or other arrangement, to engage in air transportation.

Foreign air commerce

The carriage by aircraft of persons or property for compensation or hire, or the carriage of mail by aircraft, or the operation or navigation of aircraft in the conduct or furtherance of a business or vocation, in commerce between a place in the United States and any place outside thereof; whether such commerce moves wholly by aircraft or partly by aircraft and partly by other forms of transportation.

Foreign air transportation

The carriage by aircraft of persons or property as a common carrier for compensation or hire, or the carriage of mail by aircraft, in commerce between a place in the United States and any place outside of the United States, whether that commerce moves wholly by aircraft or partly by aircraft and partly by other forms of transportation.

Foreign object damage (FOD)

Damage to a gas turbine engine caused by some object being sucked into the engine while it is running. Debris from runways or taxiways can cause foreign object damage during ground operations, and the ingestion of ice and birds can cause FOD in flight.

Form Drag

The part of parasite drag on a body resulting from the integrated effect of the static pressure acting normal to its surface resolved in the drag direction.

Form drag

The drag created because of the shape of a component or the aircraft.

Formal lecture

An oral presentation where the purpose is to inform, persuade, or entertain with little or no verbal participation by the listeners.

Formation Flight

More than one aircraft which, by prior arrangement between the pilots, operate as a single aircraft with regard to navigation and position reporting. Separation between aircraft within the formation is the responsibility of the flight leader and the pilots of the other aircraft in the flight. This includes transition periods when aircraft within the formation are maneuvering to attain separation from each other to effect individual control and during join-up and breakaway. a. A standard formation is one in which a proximity of no more than 1 mile laterally or longitudinally and within 100 feet vertically from the flight leader is maintained by each wingman. b. Nonstandard formations are those operating under any of the following conditions: 1. When the flight leader has requested and ATC has approved other than standard formation dimensions. 2. When operating within an authorized altitude reservation (ALTRV) or under the provisions of a letter of agreement. 3. When the operations are conducted in airspace specifically designed for a special activity.

Forward Slip

A slip in which the airplane’s direction of motion continues the same as before the slip was begun. In a forward slip, the airplane’s longitudinal axis is at an angle to its flightpath.

Forward wing

A forward lifting surface of a canard configuration or tandem-wing configuration airplane. The surface may be a fixed, movable, or variable geometry surface, with or without control surfaces.

Four Corner Post Configuration

An arrangement of air traffic pathways in a terminal area that brings incoming flights over fixes at four corners of the traffic area, while outbound flights depart between the fixes, thus minimizing conflicts between arriving and departing traffic.

FOWP

Fly-Over Waypoint

FPA

Flight Path Angle

FPM

Feet Per Minute

FPNM

Feet Per Nautical Mile

FPV

Flight Path Vector

Fractus

Clouds in the form of irregular shreds, appearing as if torn; have a clearly ragged appearance; applies only to stratus and cumulus, i.e., cumulus fractus and stratus fractus.

Free Power Turbine Engine

A turboprop engine where the gas producer spool is on a separate shaft from the output shaft. The free power turbine spins independently of the gas producer and drives the output shaft.

Freezing

The change of liquid water to ice.

Freezing Drizzle

Drizzle is precipitation at ground level or aloft in the form of liquid water drops that have diameters less than 0.5 mm and greater than 0.05 mm. Freezing drizzle is water that remains in a liquid form at air temperatures less than 0 °C (supercooled) and can freeze upon contact with objects on the ground or in the air.

Freezing level

A level in the atmosphere at which the temperature is 0° C (32° F).

Freezing Rain

Rain is precipitation at ground level or aloft in the form of liquid water drops which have diameters greater than 0.5 mm. Freezing rain is rain that exists at air temperatures less than 0 °C, remains in liquid form (supercooled), and freezes upon contact with objects on the ground or in the air.

Friction Drag

The part of parasitic drag on a body resulting from viscous shearing stresses over its wetted surface.

Frise-Type Aileron

Aileron having the nose portion projecting ahead of the hinge line. When the trailing edge of the aileron moves up, the nose projects below the wing’s lower surface and produces some parasite drag, decreasing the amount of adverse yaw.

Front

A surface, interface, or transition zone of discontinuity between two adjacent air masses of different densities; more simply the boundary between two different air masses.

Front

The boundary between two air masses. A front can be classified as cold, warm, occluded, or stationary.

Frontal zone

A front or zone with a marked increase of density gradient; used to denote that fronts are not truly a “surface” of discontinuity but rather a “zone” of rapid transition of meteorological elements.

Frontogenesis

The initial formation of a front or frontal zone.

Frontolysis

The dissipation of a front.

Frost

Ice crystal deposits formed by sublimation when temperature and dewpoint are below freezing.

Frost (also hoarfrost)

Ice crystal deposits formed by sublimation when temperature and dew point are below freezing.

FSDO

Flight Standards District Office

FSDO

Flight Standards District Office

FSM

Flight Schedule Monitor. A tool used by Air Traffic Management Specialists to monitor air traffic demand at airports.

FSS

Flight Service Station

FSS

Flight Service Station. Air traffic facilities which provide pilot briefing, en route communications and VFR search and rescue services, assist lost aircraft and aircraft in emergency situations, relay ATC clearances, originate Notices to Airmen, broadcast aviation weather and NAS information, receive and process IFR flight plans, and monitor NAVAIDs. In addition, at selected locations, FSSs provide En Route Flight Advisory Service (Flight Watch), take weather observations, issue airport advisories, and advise Customs and Immigration of transborder flights.

FSTD

Flight Simulation Training Device.

FTD

Flight Training Device.

FTD

Flight Training Device.

FTE

Flight Technical Error

Fuel Control Unit

The fuel-metering device used on a turbine engine that meters the proper quantity of fuel to be fed into the burners of the engine. It integrates the parameters of inlet air temperature, compressor speed, compressor discharge pressure, and exhaust gas temperature with the position of the cockpit power control lever.

Fuel Dumping

Airborne release of usable fuel. This does not include the dropping of fuel tanks.

Fuel Efficiency

Defined as the amount of fuel used to produce a specific thrust or horsepower divided by the total potential power contained in the same amount of fuel.

Fuel Heaters

A radiator-like device which has fuel passing through the core. A heat exchange occurs to keep the fuel temperature above the freezing point of water so that entrained water does not form ice crystals, which could block fuel flow.

Fuel Injection

A fuel metering system used on some aircraft reciprocating engines in which a constant flow of fuel is fed to injection nozzles in the heads of all cylinders just outside of the intake valve. It differs from sequential fuel injection in which a timed charge of high-pressure fuel is sprayed directly into the combustion chamber of the cylinder.

Fuel Jettison System

A fuel subsystem that allows the flight crew to dump fuel in an emergency to lower the weight of an aircraft to the maximum landing weight if a return to landing is required before sufficient fuel is burned off. This system must allow enough fuel to be jettisoned that the aircraft can still meet the climb requirements specified in 14 CFR part 25.

Fuel Load

The expendable part of the load of the airplane. It includes only usable fuel, not fuel required to fill the lines or that which remains trapped in the tank sumps.

Fuel load

The expendable part of the load of the airplane. It includes only usable fuel, not fuel required to fill the lines or that which remains trapped in the tank sumps.

Fuel Remaining

A phrase used by either pilots or controllers when relating to the fuel remaining on board until actual fuel exhaustion. When transmitting such information in response to either a controller question or pilot initiated cautionary advisory to air traffic control, pilots will state the APPROXIMATE NUMBER OF MINUTES the flight can continue with the fuel remaining. All reserve fuel SHOULD BE INCLUDED in the time stated, as should an allowance for established fuel gauge system error.

Fuel Siphoning

Unintentional release of fuel caused by overflow, puncture, loose cap, etc.

Fuel Tank Sump

A sampling port in the lowest part of the fuel tank that the pilot can utilize to check for contaminants in the fuel.

Fuel Venting

Fuel Siphoning.

Fulcrum

The point about which a lever balances.

Full flight simulator (FFS)

A replica of a specific type; or make, model, and series aircraft cockpit. It includes the assemblage of equipment and computer programs necessary to represent aircraft operations in ground and flight conditions, a visual system providing an out-of-the-cockpit view, a system that provides cues at least equivalent to those of a three-degree-of-freedom motion system, and has the full range of capabilities of the systems installed in the device as described in part 60 of this chapter and the qualification performance standards (QPS) for a specific FFS qualification level.

Fundamental skills

Pilot skills of instrument cross-check, instrument interpretation, and aircraft control.

Funnel cloud

A tornado cloud or vortex cloud extending downward from the parent cloud but not reaching the ground.

Fuselage

The section of the airplane that consists of the cabin and/or cockpit, containing seats for the occupants and the controls for the airplane.

Fuselage

The section of the airplane that consists of the cabin and/or cockpit, containing seats for the occupants and the controls for the airplane.

G/S

Glide Slope

GA

General Aviation

GA CDR

General Aviation Coded Departure Routes (GA CDR) - The CDR program provides a rapid means to reroute aircraft when the filed route is constrained by either weather or congestion. Historically, abbreviated CDR clearances have only been issued to airline customers who have signed a Memorandum of Agreement (MOA) with the facilities that issue abbreviated CDR clearances. Recently, general aviation customers have requested the use of this reroute capability. This change permits general aviation customers to communicate to Air Traffic Control (ATC) facilities their ability and willingness to accept CDRs and their capability to accept abbreviated clearances associated with CDRs. Please see the GA CDR Advisory circular for more details.

GAMA

General Aviation Manufacturers Association

GAMA

General Aviation Manufacturers Association.

Gas Generator

The basic power producing portion of a gas turbine engine and excluding such sections as the inlet duct, the fan section, free power turbines, and tailpipe. Each manufacturer designates what is included as the gas generator, but generally consists of the compressor, diffuser, combustor, and turbine.

Gas Turbine Engine

A form of heat engine in which burning fuel adds energy to compressed air and accelerates the air through the remainder of the engine. Some of the energy is extracted to turn the air compressor, and the remainder accelerates the air to produce thrust. Some of this energy can be converted into torque to drive a propeller or a system of rotors for a helicopter.

Gate Hold Procedures

Procedures at selected airports to hold aircraft at the gate or other ground location whenever departure delays exceed or are anticipated to exceed 15 minutes. The sequence for departure will be maintained in accordance with initial call-up unless modified by flow control restrictions. Pilots should monitor the ground control/clearance delivery frequency for engine start/taxi advisories or new proposed start/taxi time if the delay changes.

Gateway Fix

A navigational aid or fix where an aircraft transitions between the domestic route structure and the oceanic route airspace.

GBAS

Ground Based Augmentation System

GBT

Ground-Based Transmitter

GCA

Ground Controlled Approach

GCO

Ground Communication Outlet

GDP

Ground Delay Programs

GDP

Ground Delay Program. Ground Delay Programs are implemented to control air traffic volume to airports where the projected traffic demand is expected to exceed the airport´s acceptance rate for a lengthy period of time. Lengthy periods of demand exceeding acceptance rate are normally a result of the airport´s acceptance rate being reduced for some reason. The most common reason for a reduction in acceptance rate is adverse weather such as low ceilings and visibility.
How it works: Flights that are destined to the affected airport are issued Expect Departure Clearance Times (EDCT) at their point of departure. Flights that have been issued EDCTs are not permitted to depart until their Expect Departure Clearance Time. These ECDTs are calculated in such a way as to meter the rate that traffic arrives at the affected airport; ensuring that demand is equal to acceptance rate. The length of delays that result from the implementation of a Ground Delay Program is a factor of two things; how much greater than the acceptance rate the original demand was, and for what length of time the original demand was expected to exceed the acceptance rate.

GDPE

Ground Delay Program Enhancements

General Aviation

That portion of civil aviation which encompasses all facets of aviation except air carriers holding a certificate of public convenience and necessity from the Civil Aeronautics Board and large aircraft commercial operators.

GEO

Geostationary Satellite

Geodetic Datum

The reference plane from which geodetic calculations are made. Or, according to ICAO Annex 15, the numerical or geometrical quantity or set of such quantities (mathematical model) that serves as a reference for computing other quantities in a specific geographic region such as the latitude and longitude of a point.

Gimbal ring

A type of support that allows an object, such as a gyroscope, to remain in an upright condition when its base is tilted.

Glaze

A coating of ice, generally clear and smooth, formed by freezing of super.cooled water on a surface.

Glide Ratio

The ratio between distance traveled and altitude lost during non-powered flight.

Glide slope (GS)

Part of the ILS that projects a radio beam upward at an angle of approximately 3° from the approach end of an instrument runway. The glide slope provides vertical guidance to aircraft on the final approach course for the aircraft to follow when making an ILS approach along the localizer path.

Glide slope intercept altitude

The minimum altitude of an intermediate approach segment prescribed for a precision approach that ensures obstacle clearance.

Glidepath

The path of an aircraft relative to the ground while approaching a landing.

Glidepath Angle (GPA)

The angular displacement of the vertical guidance path from a horizontal plane that passes through the reference datum point (RDP). This angle is published on approach charts (e.g., 3.00, 3.20, etc.). GPA is sometimes referred to as vertical path angle (VPA).

Glidepath Intercept Altitude

Glideslope Intercept Altitude.

Glider

A heavier-than-air aircraft, that is supported in flight by the dynamic reaction of the air against its lifting surfaces and whose free flight does not depend principally on an engine.

Glideslope (GS)

Part of the ILS that projects a radio beam upward at an angle of approximately 3° from the approach end of an instrument runway. The glideslope provides vertical guidance to aircraft on the final approach course for the aircraft to follow when making an ILS approach along the localizer path.

Glideslope Intercept Altitude

The minimum altitude to intercept the glideslope/path on a precision approach. The intersection of the published intercept altitude with the glideslope/path, designated on Government charts by the lightning bolt symbol, is the precision FAF; however, when the approach chart shows an alternative lower glideslope intercept altitude, and ATC directs a lower altitude, the resultant lower intercept position is then the FAF.

Global landing system (GLS)

An instrument approach with lateral and vertical guidance with integrity limits (similar to barometric vertical navigation (BRO VNAV).

Global Navigation Satellite System (GNSS)

An umbrella term adopted by the International Civil Aviation Organization (ICAO) to encompass any independent satellite navigation system used by a pilot to perform onboard position determinations from the satellite data.

Global navigation satellite system (GNSS)

Satellite navigation system that provides autonomous geospatial positioning with global coverage. It allows small electronic receivers to determine their location (longitude, latitude, and altitude) to within a few meters using time signals transmitted along a line of sight by radio from satellites.

Global positioning system (GPS)

Navigation system that uses satellite rather than ground-based transmitters for location information.

Global Positioning System (GPS)

A space-base radio positioning, navigation, and time-transfer system. The system provides highly accurate position and velocity information, and precise time, on a continuous global basis, to an unlimited number of properly equipped users. The system is unaffected by weather, and provides a worldwide common grid reference system. The GPS concept is predicated upon accurate and continuous knowledge of the spatial position of each satellite in the system with respect to time and distance from a transmitting satellite to the user. The GPS receiver automatically selects appropriate signals from the satellites in view and translates these into three-dimensional position, velocity, and time. System accuracy for civil users is normally 100 meters horizontally.

GLS

Global Navigation Satellite System Landing System

GLS

GNSS Landing System

GLS

Global Landing System.

GNE

Gross Navigation Error

GNSS

Global Navigation Satellite Systems.

GNSS

Global Navigation Satellite System.

GNSSP

Global Navigation Satellite System Panel

Go Ahead

Proceed with your message. Not to be used for any other purpose.

Go Around

Instructions for a pilot to abandon his/her approach to landing. Additional instructions may follow. Unless otherwise advised by ATC, a VFR aircraft or an aircraft conducting visual approach should overfly the runway while climbing to traffic pattern altitude and enter the traffic pattern via the crosswind leg. A pilot on an IFR flight plan making an instrument approach should execute the published missed approach procedure or proceed as instructed by ATC; e.g., “Go around” (additional instructions if required).

Go-around power or thrust setting

The maximum allowable in-flight power or thrust setting identified in the performance data.

Goals and values

A perception factor that describes how a person’s perception of an event depends on beliefs. Motivation toward learning is affected by how much value a person puts on education. Instructors who have some idea of the goals and values of their students will be more successful in teaching them.

Goniometer

As used in radio frequency (RF) antenna systems, a direction-sensing device consisting of two fixed loops of wire oriented 90 from each other, which separately sense received signal strength and send those signals to two rotors (also oriented 90) in the sealed direction-indicating instrument. The rotors are attached to the direction-indicating needle of the instrument and rotated by a small motor until minimum magnetic field is sensed near the rotors.

Goniometer

As used in radio frequency (RF) antenna systems, a direction-sensing device consisting of two fixed loops of wire oriented 90° from each other, which separately sense received signal strength and send those signals to two rotors (also oriented 90°) in the sealed direction-indicating instrument. The rotors are attached to the direction-indicating needle of the instrument and rotated by a small motor until minimum magnetic field is sensed near the rotors.

Governing Range

The range of pitch a propeller governor can control during flight.

Governor

A control which limits the maximum rotational speed of a device.

GPS

Global Positioning System.

GPS

Global Positioning System

GPS Approach Overlay Program

An authorization for pilots to use GPS avionics under IFR for flying designated existing nonprecision instrument approach procedures, with the exception of LOC, LDA, and SDF procedures.

GPWS

Ground Proximity Warning System

GPWS

Ground Proximity Warning System.

Gradient

In meteorology, a horizontal decrease in value per unit distance of a parameter in the direction of maximum decrease; most commonly used with pressure, temperature, and moisture.

Graveyard spiral

The illusion of the cessation of a turn while still in a prolonged, coordinated, constant rate turn, which can lead a disoriented pilot to a loss of control of the aircraft.

Graveyard spiral

The illusion of the cessation of a turn while still in a prolonged, coordinated, constant rate turn, which can lead a disoriented pilot to a loss of control of the aircraft.

Great circle route

The shortest distance across the surface of a sphere (the Earth) between two points on the surface.

Great circle route

The shortest distance across the surface of a sphere (the Earth) between two points on the surface.

GRI

Group Repetition Interval

Gross Navigation Error (GNE)

In the North Atlantic area of operations, a gross navigation error is a lateral separation of more than 25 NM from the centerline of an aircrafts cleared route, which generates an Oceanic Navigation Error Report. This report is also generated by a vertical separation if you are more than 300 feet off your assigned flight level.

Gross Weight

The total weight of a fully loaded aircraft including the fuel, oil, crew, passengers, and cargo.

Ground Adjustable Trim Tab

A metal trim tab on a control surface that is not adjustable in flight. Bent in one direction or another while on the ground to apply trim forces to the control surface.

Ground clutter

Pertaining to radar, a cluster of echoes, generally at short range, reflected from ground targets.

Ground Clutter

A pattern produced on the radar scope by ground returns which may degrade other radar returns in the affected area. The effect of ground clutter is minimized by the use of moving target indicator (MTI) circuits in the radar equipment resulting in a radar presentation which displays only targets which are in motion.

Ground Communication Outlet (GCO)

An unstaffed, remotely controlled, ground/ground communications facility. Pilots at uncontrolled airports may contact ATC and FSS via VHF to a telephone connection to obtain an instrument clearance or close a VFR or IFR flight plan. They may also get an updated weather briefing prior to takeoff. Pilots will use four “key clicks” on the VHF radio to contact the appropriate ATC facility or six “key clicks” to contact the FSS. The GCO system is intended to be used only on the ground.

Ground Controlled Approach

A radar approach system operated from the ground by air traffic control personnel transmitting instructions to the pilot by radio. The approach may be conducted with surveillance radar (ASR) only or with both surveillance and precision approach radar (PAR). Usage of the term “GCA” by pilots is discouraged except when referring to a GCA facility. Pilots should specifically request a “PAR” approach when a precision radar approach is desired or request an “ASR” or “surveillance” approach when a nonprecision radar approach is desired.

Ground Delay Program (GDP)

A traffic management process administered by the ATCSCC; when aircraft are held on the ground. The purpose of the program is to support the TM mission and limit airborne holding. It is a flexible program and may be implemented in various forms depending upon the needs of the AT system. Ground delay programs provide for equitable assignment of delays to all system users.

Ground Effect

A condition of improved performance encountered when an airplane is operating very close to the ground. When an airplane’s wing is under the influence of ground effect, there is a reduction in upwash, downwash, and wingtip vortices. As a result of the reduced wingtip vortices, induced drag is reduced.

Ground fog

In the United States, a fog that conceals less than 0.6 of the sky and is not contiguous with the base of clouds.

Ground Idle

Gas turbine engine speed usually 60-70 percent of the maximum r.p.m. range, used as a minimum thrust setting for ground operations.

Ground Loop

A sharp, uncontrolled change of direction of an airplane on the ground.

Ground Power Unit (GPU)

A type of small gas turbine whose purpose is to provide electrical power, and/or air pressure for starting aircraft engines. A ground unit is connected to the aircraft when needed. Similar to an aircraft-installed auxiliary power unit.

Ground proximity warning system (GPWS)

A system designed to determine an aircrafts clearance above the Earth and provides limited predictability about aircraft position relative to rising terrain.

Ground proximity warning system (GPWS)

A system designed to determine an aircraft’s clearance above the Earth and provides limited predictability about aircraft position relative to rising terrain.

Ground Speed

The speed of an aircraft relative to the surface of the earth.

Ground Stop (GS)

The GS is a process that requires aircraft that meet a specific criteria to remain on the ground. The criteria may be airport specific, airspace specific, or equipment specific; for example, all departures to San Francisco, or all departures entering Yorktown sector, or all Category I and II aircraft going to Charlotte. GSs normally occur with little or no warning.

Ground Track

The aircraft’s path over the ground when in flight.

Ground visibility

Prevailing horizontal visibility near the earth’s surface as reported by the United States National Weather Service or an accredited observer.

Ground Visibility

Prevailing horizontal visibility near the earth’s surface as reported by the United States National Weather Service or an accredited observer.

Ground Visibility [ICAO]

The visibility at an aerodrome as reported by an accredited observer.

Groundspeed

Speed over the ground, either closing speed to the station or waypoint, or speed over the ground in whatever direction the aircraft is going at the moment, depending upon the navigation system used.

Groundspeed

Speed over the ground, either closing speed to the station or waypoint, or speed over the ground in whatever direction the aircraft is going at the moment, depending upon the navigation system used.

Groundspeed Measurement System

A measurement system for determining the groundspeed of an aircraft during final approach and landing, by measuring at the aircraft the Doppler shift of a radio signal, and/or its modulation components, transmitted by a fixed ground station.

GS

Glide Slope.

GS

Groundspeed

GS

Ground Stop. Ground Stops are implemented for a number of reasons. The most common reasons are:
To control air traffic volume to airports when the projected traffic demand is expected to exceed the airport´s acceptance rate for a short period of time.
To temporarily stop traffic allowing for the implementation of a longer-term solution, such as a Ground Delay Program.
The affected airport´s acceptance rate has been reduced to zero.
How it works: Flights that are destined to the affected airport are held at their departure point for the duration of the Ground Stop.

GSD

Geographical Situation Display

Guided discussion method

An educational presentation typically used in the classroom where the topic to be covered by a group is introduced and the instructor participates only as necessary to keep the group focused on the subject.

GUS

Ground Uplink Station

Gust

A sudden brief increase in wind; according to U.S. weather observing practice, gusts are reported when the variation in wind speed between peaks and lulls is at least 10 knots.

Gust Penetration Speed

The speed that gives the greatest margin between the high and low mach speed buffets.

GWPS

Ground Proximity Warning System.

GWPS

Ground Proximity Warning System.

GWS

Graphical Weather Service

Gyrodyne

A rotorcraft whose rotors are normally engine-driven for takeoff, hovering, and landing, and for forward flight through part of its speed range, and whose means of propulsion, consisting usually of conventional propellers, is independent of the rotor system.

Gyroplane

A rotorcraft whose rotors are not engine-driven, except for initial starting, but are made to rotate by action of the air when the rotorcraft is moving; and whose means of propulsion, consisting usually of conventional propellers, is independent of the rotor system.

Gyroscopic Precession

An inherent quality of rotating bodies, which causes an applied force to be manifested 90º in the direction of rotation from the point where the force is applied.

Gyroscopic precession

An inherent quality of rotating bodies, which causes an applied force to be manifested 90° in the direction of rotation from the point where the force is applied.

HAA

Height Above Airport.

Hail

A form of precipitation composed of balls or irregular lumps of ice, always produced by convective clouds which are nearly always cumulonimbus.

HAL

Height Above Landing.

Halo

A prismatically colored or whitish circle or arcs of a circle with the sun or moon at its center; coloration, if not white, is from red inside to blue outside (opposite that of a corona); fixed in size with an angular diameter of 22° (common) or 46° (rare); characteristic of clouds composed of ice crystals; valuable in differentiating between cirriform and forms of lower clouds.

Hand Propping

Starting an engine by rotating the propeller by hand.

Handoff

An action taken to transfer the radar identification of an aircraft from one controller to another if the aircraft will enter the receiving controller’s airspace and radio communications with the aircraft will be transferred.

HAT

Height Above Touchdown Elevation.

Have Numbers

Used by pilots to inform ATC that they have received runway, wind, and altimeter information only.

Hazardous attitudes

Five aeronautical decision-making attitudes that may contribute to poor pilot judgment: antiauthority, impulsivity, invulnerability, machismo, and resignation.

Hazardous attitudes

Five aeronautical decision-making attitudes that may contribute to poor pilot judgment: anti-authority, impulsivity, invulnerability, machismo, and resignation.

Hazardous Inflight Weather Advisory Service

Continuous recorded hazardous inflight weather forecasts broadcasted to airborne pilots over selected VOR outlets defined as an HIWAS Broadcast Area. Discontinued on January 8, 2020.

Hazardous Inflight Weather Advisory Service (HIWAS)

Service providing recorded weather forecasts broadcast to airborne pilots over selected VORs. Discontinued on January 8, 2020.

Hazardous Inflight Weather Advisory Service (HIWAS).

Service providing recorded weather forecasts broadcast to airborne pilots over selected VORs. Discontinued on January 8, 2020.

Hazardous Weather Information

Summary of significant meteorological information (SIGMET/WS), convective significant meteorological information (convective SIGMET/WST), urgent pilot weather reports (urgent PIREP/UUA), center weather advisories (CWA), airmen’s meteorological information (AIRMET/WA) and any other weather such as isolated thunderstorms that are rapidly developing and increasing in intensity, or low ceilings and visibilities that are becoming widespread which is considered significant and are not included in a current hazardous weather advisory.

Hazardous Weather Information

Summary of SIGMETs, Convective SIGMETs, urgent Pilot Weather Reports (PIREP), CWAs, AIRMETs, and any other significant weather provided to pilots that might not be routinely provided in a standard format or report.

Haze

A type of lithometeor composed of fine dust or salt particles dispersed through a portion of the atmosphere; particles are so small they cannot be felt or individually seen with the naked eye (as compared with the larger particles of dust), but diminish the visibility; distinguished from fog by its bluish or yellowish tinge.

HDTA

High Density Traffic Airports

Head-Up Display (HUD)

See Head-Up Guidance System (HGS)

Head-up display (HUD)

A special type of flight viewing screen that allows the pilot to watch the flight instruments and other data while looking through the windshield of the aircraft for other traffic, the approach lights, or the runway.

Head-Up Guidance System (HGS)

A system which projects critical flight data on a display positioned between the pilot and the windscreen. In addition to showing primary flight information, the HUD computes an extremely accurate instrument approach and landing guidance solution, and displays the result as a guidance cue for head-up viewing by the pilot.

Heading

The direction in which the nose of the aircraft is pointing during flight.

Heading

The direction in which the nose of the aircraft is pointing during flight.

Heading Bug

A marker on the heading indicator that can be rotated to a specific heading for reference purposes, or to command an autopilot to fly that heading.

Heading Indicator

An instrument which senses airplane movement and displays heading based on a 360º azimuth, with the final zero omitted. The heading indicator, also called a directional gyro, is fundamentally a mechanical instrument designed to facilitate the use of the magnetic compass. The heading indicator is not affected by the forces that make the magnetic compass difficult to interpret.

Heading indicator

An instrument which senses airplane movement and displays heading based on a 360° azimuth, with the final zero omitted. The heading indicator, also called a directional gyro (DG), is fundamentally a mechanical instrument designed to facilitate the use of the magnetic compass. The heading indicator is not affected by the forces that make the magnetic compass difficult to interpret.

Headwind Component

The component of atmospheric winds that acts opposite to the aircraft’s flightpath.

Headwork

Required to accomplish a conscious, rational thought process when making decisions. Good decision-making involves risk identification and assessment, information processing, and problem solving.

Heavy

An Aircraft Class Wake Turbulence Separation Minima. Aircraft capable of takeoff weights of 300,000 pounds or more whether or not they are operating at this weight during a particular phase of flight.

Height Above Airport

The height of the Minimum Descent Altitude above the published airport elevation. This is published in conjunction with circling minimums.

Height Above Landing

The height above a designated helicopter landing area used for helicopter instrument approach procedures.

Height Above Touchdown

The height of the Decision Height or Minimum Descent Altitude above the highest runway elevation in the touchdown zone (first 3,000 feet of the runway). HAT is published on instrument approach charts in conjunction with all straight-in minimums.

Height above touchdown elevation (HAT)

The DA/DH or MDA above the highest runway elevation in the touchdown zone (first 3,000 feet of the runway).

Helicopter

A rotorcraft that, for its horizontal motion, depends principally on its engine-driven rotors.

Helipad

A small, designated area, usually with a prepared surface, on a heliport, airport, landing/takeoff area, apron/ramp, or movement area used for takeoff, landing, or parking of helicopters.

Heliport

An area of land, water, or structure used or intended to be used for the landing and takeoff of helicopters.

Heliport

An area of land, water, or structure used or intended to be used for the landing and takeoff of helicopters and includes its buildings and facilities if any.

Heliport Reference Point (HRP)

The geographic center of a heliport.

HEMS

Helicopter Emergency Medical Service

HEMS

Helicopter Emergency Medical Services

Hertz

The standard radio equivalent of frequency in cycles per second of an electromagnetic wave. Kilohertz (kHz) is a frequency of one thousand cycles per second. Megahertz (MHz) is a frequency of one million cycles per second.

HF

High Frequency.

HF

High Frequency.

HF Communications

High Frequency Communications.

HFDL

High Frequency Data Link

Hg

Abbreviation for mercury, from the Latin hydrargyrum.

Hg

Abbreviation for mercury, from the Latin hydrargyrum.

Hierarchy of human needs

A listing by Abraham Maslow of needs, from the most basic to the most fulfilling: physiological, security, belonging, esteem, cognitive and aesthetic, and self-actualization.

High

An area of high barometric pressure, with its attendant system of winds; an anticyclone. Also high pressure system.

High Frequency

The frequency band between 3 and 30 MHz.

High Frequency Communications

High radio frequencies (HF) between 3 and 30 MHz used for air-to-ground voice communication in overseas operations.

High Performance Aircraft

An aircraft with an engine of more than 200 horsepower.

High performance aircraft

An aircraft with an engine of more than 200 horsepower.

High Speed Exit

High Speed Taxiway.

High Speed Taxiway

A long radius taxiway designed and provided with lighting or marking to define the path of aircraft, traveling at high speed (up to 60 knots), from the runway center to a point on the center of a taxiway. Also referred to as long radius exit or turn-off taxiway. The high speed taxiway is designed to expedite aircraft turning off the runway after landing, thus reducing runway occupancy time.

High Speed Turnoff

High Speed Taxiway.

Highway in the Sky (HITS)

A graphically intuitive pilot interface system that provides an aircraft operator with all of the attitude and guidance inputs required to safely fly an aircraft in close conformance to air traffic procedures.

HIRL

High-Intensity Runway Light System.

HIRL

High Intensity Runway Lights

Histotoxic hypoxia

The inability of cells to effectively use oxygen. Plenty of oxygen is being transported to the cells that need it, but they are unable to use it.

HITS

Highway In The Sky

HIWAS

Hazardous Inflight Weather Advisory Service. Discontinued on January 8, 2020.

HIWAS

Hazardous Inflight Weather Advisory Service. Discontinued on January 8, 2020.

HIWAS

Hazardous Inflight Weather Advisory Service. Discontinued on January 8, 2020.

HIWAS Broadcast Area

A geographical area of responsibility including one or more HIWAS outlet areas assigned to an AFSS/FSS for hazardous weather advisory broadcasting. Discontinued on January 8, 2020.

HIWAS Outlet Area

An area defined as a 150 NM radius of a HIWAS outlet, expanded as necessary to provide coverage. Discontinued on January 8, 2020.

Hold For Release

Used by ATC to delay an aircraft for traffic management reasons; i.e., weather, traffic volume, etc. Hold for release instructions (including departure delay information) are used to inform a pilot or a controller (either directly or through an authorized relay) that an IFR departure clearance is not valid until a release time or additional instructions have been received.

Hold In Lieu Of Procedure Turn

A hold in lieu of procedure turn shall be established over a final or intermediate fix when an approach can be made from a properly aligned holding pattern. The hold in lieu of procedure turn permits the pilot to align with the final or intermediate segment of the approach and/or descend in the holding pattern to an altitude that will permit a normal descent to the final approach fix altitude. The hold in lieu of procedure turn is a required maneuver (the same as a procedure turn) unless the aircraft is being radar vectored to the final approach course, when “NoPT” is shown on the approach chart, or when the pilot requests or the controller advises the pilot to make a “straight-in” approach.

Hold Procedure

A predetermined maneuver which keeps aircraft within a specified airspace while awaiting further clearance from air traffic control. Also used during ground operations to keep aircraft within a specified area or at a specified point while awaiting further clearance from air traffic control.

Hold-Short Point

A point on the runway beyond which a landing aircraft with a LAHSO clearance is not authorized to proceed. This point may be located prior to an intersecting runway, taxiway, predetermined point, or approach/departure flight path.

Hold-Short Position Lights

Flashing in-pavement white lights located at specified hold-short points.

Hold-Short Position Marking

The painted runway marking located at the hold-short point on all LAHSO runways.

Hold-Short Position Signs

Red and white holding position signs located alongside the hold-short point.

Holding

A predetermined maneuver that keeps aircraft within a specified airspace while awaiting further clearance from ATC.

Holding Fix

A specified fix identifiable to a pilot by NAVAIDs or visual reference to the ground used as a reference point in establishing and maintaining the position of an aircraft while holding.

Holding pattern

A racetrack pattern, involving two turns and two legs, used to keep an aircraft within a prescribed airspace with respect to a geographic fix. A standard pattern uses right turns; nonstandard patterns use left turns.

Homing

Flying the aircraft on any heading required to keep the needle pointing to the 0 relative bearing position.

Horizon

The line of sight boundary between the earth and the sky.

Horizontal situation indicator (HSI)

A flight navigation instrument that combines the heading indicator with a CDI, in order to provide the pilot with better situational awareness of location with respect to the courseline.

Horizontal situation indicator (HSI)

A flight navigation instrument that combines the heading indicator with a CDI, in order to provide the pilot with better situational awareness of location with respect to the courseline.

Horsepower

The term, originated by inventor James Watt, means the amount of work a horse could do in one second. One horsepower equals 550 foot-pounds per second, or 33,000 foot-pounds per minute.

Hot Start

In gas turbine engines, a start which occurs with normal engine rotation, but exhaust temperature exceeds prescribed limits. This is usually caused by an excessively rich mixture in the combustor. The fuel to the engine must be terminated immediately to prevent engine damage.

Hover Check

Used to describe when a helicopter/VTOL aircraft requires a stabilized hover to conduct a performance/power check prior to hover taxi, air taxi, or takeoff. Altitude of the hover will vary based on the purpose of the check.

Hover Taxi

Used to describe a helicopter/VTOL aircraft movement conducted above the surface and in ground effect at airspeeds less than approximately 20 knots. The actual height may vary, and some helicopters may require hover taxi above 25 feet AGL to reduce ground effect turbulence or provide clearance for cargo slingloads.

How Do You Hear Me?

A question relating to the quality of the transmission or to determine how well the transmission is being received.

HRR

Helicopter Rapid Refueling Procedures

HSAC

Helicopter Safety Advisory Council

HSI

Horizontal Situation Indicator.

HSI

Horizontal Situation Indicator.

HUD

Head-Up Display.

HUD

Head-Up Display.

Human factors

A multidisciplinary field encompassing the behavioral and social sciences, engineering, and physiology, to consider the variables that influence individual and crew performance for the purpose of optimizing human performance and reducing errors.

Human factors

A multidisciplinary field devoted to optimizing human performance and reducing human error. It incorporates the methods and principles of the behavioral and social sciences, engineering, and physiology. It may be described as the applied science which studies people working together in concert with machines. Human factors involve variables that influence individual performance, as well as team or crew performance.

Human factors

Human nature

The general psychological characteristics, feelings, and behavioral traits shared by all humans.

Humidity

Water vapor content of the air; may be expressed as specific humidity, relative humidity, or mixing ratio.

Hung Start

In gas turbine engines, a condition of normal light off but with r.p.m. remaining at some low value rather than increasing to the normal idle r.p.m. This is often the result of insufficient power to the engine from the starter. In the event of a hung start, the engine should be shut down.

Hurricane

A tropical cyclone in the Western Hemisphere with winds in excess of 65 knots or 120 km/h.

Hydraulics

The branch of science that deals with the transmission of power by incompressible fluids under pressure.

Hydrometeor

A general term for particles of liquid water or ice such as rain, fog, frost, etc., formed by modification of water vapor in the atmosphere; also water or ice particles lifted from the earth by the wind such as sea spray or blowing snow.

Hydroplaning

Hygrograph

The record produced by a continuous-recording hygrometer.

Hygrometer

An instrument for measuring the water vapor content of the air.

Hypemic hypoxia

A type of hypoxia that is a result of oxygen deficiency in the blood, rather than a lack of inhaled oxygen. It can be caused by a variety of factors. Hypemic means “not enough blood.”.

Hyperventilation

Occurs when an individual is experiencing emotional stress, fright, or pain, and the breathing rate and depth increase, although the carbon dioxide level in the blood is already at a reduced level. The result is an excessive loss of carbon dioxide from the body, which can lead to unconsciousness due to the respiratory system’s overriding mechanism to regain control of breathing.

Hypoxia

A lack of sufficient oxygen reaching the body tissues.

Hypoxia

A state of oxygen deficiency in the body sufficient to impair functions of the brain and other organs.

Hypoxic hypoxia

This type of hypoxia is a result of insufficient oxygen available to the lungs. A decrease of oxygen molecules at sufficient pressure can lead to hypoxic hypoxia.

Hz

Hertz

I Say Again

The message will be repeated.

IAF

Initial Approach Fix.

IAP

Instrument Approach Procedures.

IAS

Indicated Airspeed.

IAS

Indicated Airspeed.

IAWP

Initial Approach Waypoint

ICA

Initial Climb Area

ICAO

International Civil Aviation Organization.

ICAO

International Civil Aviation Organization.

Ice crystals

A type of precipitation composed of unbranched crystals in the form of needles, columns, or plates; usually having a very slight downward motion, may fall from a cloudless sky.

Ice Crystals

Ice crystals, which are often in high concentrations near convective weather systems and lower concentrations in stratus or cirrus clouds, can accrete within turbine engines and cause power loss when in high concentrations. Ice crystals are not typically detected by either conventional ice detectors or airborne radar, and typically do not accrete on external airframe surfaces.

Ice fog

A type of fog composed of minute suspended particles of ice; occurs at very low temperatures and may cause halo phenomena.

Ice needles

A form of ice crystals.

Ice pellets

Small, transparent or translucent, round or irregularly shaped pellets of ice. They may be (1) hard grains that rebound on striking a hard surface or (2) pellets of snow encased in ice.

Icing

In general, any deposit of ice forming on an object. Types include clear icing, rime icing, and glaze.

Icing

The accumulation of airframe ice. Types of icing are: Rime Ice, Clear Ice, Mixed.

Icing Envelopes

Icing envelopes used for the certification of aircraft for flight in icing conditions specify atmospheric icing conditions in terms of altitude, temperature, Liquid Water Content (LWC), and drop size represented by the Median Volume Diameter (MVD). The envelopes use the term mean effective diameter, but this equates to the MVD for the instrumentation and assumptions current at the time the envelopes were established.) There are two classes of icing envelopes: continuous maximum and intermittent maximum. The continuous maximum is for stratus-type clouds, and the intermittent maximum is for cumulus-type clouds.

Icing Intensity

Trace, Light, Moderate, Severe.

ICR

Integrated collaborative rerouting (ICR) is a process that builds on FEA/FCAs. The ICR process requires that a constraint is identified early. Traffic management may issue a planning (PLN) advisory describing the system constraint and providing route guidance. System stakeholders are allowed an opportunity to consider the area of concern, and provide early intent (EI) messages that communicate their decisions in response to the constraint. EI messages update enhanced traffic management system (ETMS) flight trajectories, monitor alert values and routing intentions. At the expiration of the EI window, traffic management can then analyze the customer responses and decide if the actions taken have resolved the issue, or if recommended routes, required routes, airspace flow programs (AFP) and/or other traffic management initiatives (TMIs) will be necessary to further reduce demand. ICR allows system stakeholders flexibility in managing their flights based on an identified NAS constraint, reducing the possibility of more restrictive initiatives. Traffic flow management (TFM) tools benefit from enhanced flight information and collaborative responses to system capacity actions.

Ident

Air Traffic Control request for a pilot to push the button on the transponder to identify return on the controllers scope.

Ident

Air Traffic Control request for a pilot to push the button on the transponder to identify return on the controller’s scope.

Idle thrust

The jet thrust obtained with the engine power control level set at the stop for the least thrust position at which it can be placed.

IF

Intermediate Fix

If No Transmission Received For (Time)

Used by ATC in radar approaches to prefix procedures which should be followed by the pilot in event of lost communications.

IFR

Instrument Flight Rules.

IFR

Instrument Flight Rules. A set of rules governing the conduct of flight under instrument meteorological conditions.

IFR (Instrument Flight Rules)

Rules that govern the procedure for conducting flight in weather conditions below VFR weather minimums. The term “IFR” also is used to define weather conditions and the type of flight plan under which an aircraft is operating.

IFR Aircraft

An aircraft conducting flight in accordance with instrument flight rules.

IFR conditions

Weather conditions below the minimum for flight under visual flight rules.

IFR Conditions

Weather conditions below the minimum for flight under visual flight rules.

IFR Departure Procedure

IFR Takeoff Minimums And Departure Procedures.

IFR Flight

IFR Aircraft.

IFR Landing Minimums

Landing Minimums.

IFR Military Training Routes (IR)

Routes used by the Department of Defense and associated Reserve and Air Guard units for the purpose of conducting low-altitude navigation and tactical training in both IFR and VFR weather conditions below 10,000 feet MSL at airspeeds in excess of 250 knots IAS.

IFR over-the-top

With respect to the operation of aircraft, the operation of an aircraft over-the-top on an IFR flight plan when cleared by air traffic control to maintain “VFR conditions” or “VFR conditions on top”.

IFR Takeoff Minimums And Departure Procedures

Title 14 Code of Federal Regulations Part 91, prescribes standard takeoff rules for certain civil users. At some airports, obstructions or other factors require the establishment of nonstandard takeoff minimums, departure procedures, or both to assist pilots in avoiding obstacles during climb to the minimum en route altitude. Those airports are listed in FAA/DOD Instrument Approach Procedures (IAPs) Charts under a section entitled “IFR Takeoff Minimums and Departure Procedures.” The FAA/DOD IAP chart legend illustrates the symbol used to alert the pilot to nonstandard takeoff minimums and departure procedures. When departing IFR from such airports or from any airports where there are no departure procedures, DPs, or ATC facilities available, pilots should advise ATC of any departure limitations. Controllers may query a pilot to determine acceptable departure directions, turns, or headings after takeoff. Pilots should be familiar with the departure procedures and must assure that their aircraft can meet or exceed any specified climb gradients.

IFSD

In-Flight Shutdown.

Igniter Plugs

The electrical device used to provide the spark for starting combustion in a turbine engine. Some igniters resemble spark plugs, while others, called glow plugs, have a coil of resistance wire that glows red hot when electrical current flows through the coil.

Illustrated talk

An oral presentation where the speaker relies heavily on visual aids to convey ideas to the listeners.

ILS

Instrument Landing System.

ILS

Instrument Landing System. A ground based precision approach system that provides course and vertical guidance to landing aircraft.

ILS Categories

1. Category I. An ILS approach procedure which provides for approach to a height above touchdown of not less than 200 feet and with runway visual range of not less than 1,800 feet. 2. Special Authorization Category I. An ILS approach procedure which provides for approach to a height above touchdown of not less than 150 feet and with runway visual range of not less than 1,400 feet, HUD to DH. 3. Category II. An ILS approach procedure which provides for approach to a height above touchdown of not less than 100 feet and with runway visual range of not less than 1,200 feet (with autoland or HUD to touchdown and noted on authorization, RVR 1,000 feet). 4. Special Authorization Category II with Reduced Lighting. An ILS approach procedure which provides for approach to a height above touchdown of not less than 100 feet and with runway visual range of not less than 1,200 feet with autoland or HUD to touchdown and noted on authorization (no touchdown zone and centerline lighting are required). 5. Category III: a. IIIA.-An ILS approach procedure which provides for approach without a decision height minimum and with runway visual range of not less than 700 feet. b. IIIB.-An ILS approach procedure which provides for approach without a decision height minimum and with runway visual range of not less than 150 feet. c. IIIC.-An ILS approach procedure which provides for approach without a decision height minimum and without runway visual range minimum.

ILS Category I

Provides for approach to a height above touchdown of not less than 200 feet, and with runway visual range of not less than 1,800 feet.

ILS Category II

Provides for approach to a height above touchdown of not less than 100 feet and with runway visual range of not less than 1,200 feet.

ILS Category IIIA

Provides for approach without a decision height minimum and with runway visual range of not less than 700 feet.

ILS Category IIIB

Provides for approach without a decision height minimum and with runway visual range of not less than 150 feet.

ILS Category IIIC

Provides for approach without a decision height minimum and without runway visual range minimum.

ILS PRM Approach

An instrument landing system (ILS) approach conducted to parallel runways whose extended centerlines are separated by less than 4,300 feet and the parallel runways have a Precision Runway Monitoring (PRM) system that permits simultaneous independent ILS approaches.

ILS/PRM

Instrument Landing System/Precision Runway Monitor

IM

ILS Inner Marker.

IMC

Instrument Meteorological Conditions.

IMC

Instrument Meteorological Conditions

Immediately

Used by ATC or pilots when such action compliance is required to avoid an imminent situation.

Impact Ice

Ice that forms on the wings and control surfaces or on the carburetor heat valve, the walls of the air scoop, or the carburetor units during flight. Impact ice collecting on the metering elements of the carburetor may upset fuel metering or stop carburetor fuel flow.

Impingement

The striking and adherence of a water droplet on an aircraft surface. The impingement rate is the rate at which droplets of a given size collect on a particular surface. In general, impingement rates are higher for larger drops and smaller components, such as a very high frequency (VHF) or a Global Positioning System (GPS) antenna.

In-flight shutdown (IFSD)

For ETOPS only, when an engine ceases to function (when the airplane is airborne) and is shutdown, whether self induced, flightcrew initiated or caused by an external influence. The FAA considers IFSD for all causes: for example, flameout, internal failure, flightcrew initiated shutdown, foreign object ingestion, icing, inability to obtain or control desired thrust or power, and cycling of the start control, however briefly, even if the engine operates normally for the remainder of the flight. This definition excludes the airborne cessation of the functioning of an engine when immediately followed by an automatic engine relight and when an engine does not achieve desired thrust or power but is not shutdown.

Inclinometer

An instrument consisting of a curved glass tube, housing a glass ball, and damped with a fluid similar to kerosene. It may be used to indicate inclination, as a level, or, as used in the turn indicators, to show the relationship between gravity and centrifugal force in a turn.

Inclinometer

Increase Speed To (Speed)

Speed Adjustment.

Indefinite ceiling

A ceiling classification denoting vertical visibility into a surface based obscuration.

Index Point

A location specified by the aircraft manufacturer from which arms used in weight and balance computations are measured. Arms measured from the index point are called index arms.

Indicated Airspeed (IAS)

The direct instrument reading obtained from the airspeed indicator, uncorrected for variations in atmospheric density, installation error, or instrument error. Manufacturers use this airspeed as the basis for determining airplane performance. Takeoff, landing, and stall speeds listed in the AFM or POH are indicated airspeeds and do not normally vary with altitude or temperature.

Indicated airspeed (IAS)

Shown on the dial of the instrument airspeed indicator on an aircraft. Directly related to calibrated airspeed (CAS), IAS includes instrument errors and position error.

Indicated Altitude

The altitude read directly from the altimeter (uncorrected) when it is set to the current altimeter setting.

Indirect indication

A reflection of aircraft pitch-and-bank attitude by the instruments other than the attitude indicator.

Indirect indication

A reflection of aircraft pitch-and-bank attitude by instruments other than the attitude indicator.

Induced Drag

That part of total drag which is created by the production of lift. Induced drag increases with a decrease in airspeed.

Induced drag

Drag caused by the same factors that produce lift; its amount varies inversely with airspeed. As airspeed decreases, the angle of attack must increase, in turn increasing induced drag.

Induction icing

A type of ice in the induction system that reduces the amount of air available for combustion. The most commonly found induction icing is carburetor icing.

Induction icing

A type of ice in the induction system that reduces the amount of air available for combustion. The most commonly found induction icing is carburetor icing.

Induction Manifold

The part of the engine that distributes intake air to the cylinders.

Inertia

The opposition which a body offers to a change of motion.

Inertial Navigation System

An RNAV system which is a form of self-contained navigation.

Inertial navigation system (INS)

A computer-based navigation system that tracks the movement of an aircraft via signals produced by onboard accelerometers. The initial location of the aircraft is entered into the computer, and all subsequent movement of the aircraft is sensed and used to keep the position updated. An INS does not require any inputs from outside signals.

Inertial navigation system (INS)

Inflight Refueling

Aerial Refueling.

Inflight Weather Advisory

Weather Advisory.

Initial Approach

The segment between the initial approach fix and the intermediate fix or the point where the aircraft is established on the intermediate course or final approach course.

Initial approach fix (IAF)

The fix depicted on IAP charts where the instrument approach procedure (IAP) begins unless otherwise authorized by ATC.

Initial Approach Segment

Segments Of An Instrument Approach Procedure.

Initial Climb

This stage of the climb begins when the airplane leaves the ground, and a pitch attitude has been established to climb away from the takeoff area.

Initial Climb Area (ICA)

An area beginning at the departure end of runway (DER) to provide unrestricted climb to at least 400 feet above DER elevation.

Inner Marker

A marker beacon used with an ILS (CAT II) precision approach located between the middle marker and the end of the ILS runway, transmitting a radiation pattern keyed at six dots per second and indicating to the pilot, both aurally and visually, that he/she is at the designated decision height (DH), normally 100 feet above the touchdown zone elevation, on the ILS CAT II approach. It also marks progress during a CAT III approach.

Inner Marker Beacon

Inner Marker.

Inner-Approach OFZ

The inner-approach OFZ (Obstacle Free Zone)is a defined volume of airspace centered on the approach area. The inner-approach OFZ applies only to runways with an approach lighting system. The inner-approach OFZ begins 200 feet from the runway threshold at the same elevation as the runway threshold and extends 200 feet beyond the last light unit in the approach lighting system. The width of the inner-approach OFZ is the same as the runway OFZ and rises at a slope of 50 (horizontal) to 1 (vertical) from the beginning.

Inner-Transitional OFZ

The inner transitional surface OFZ (Obstacle Free Zone) is a defined volume of airspace along the sides of the runway and inner-approach OFZ and applies only to precision instrument runways. The inner-transitional surface OFZ slopes 3 (horizontal) to 1 (vertical) out from the edges of the runway OFZ and inner-approach OFZ to a height of 150 feet above the established airport elevation.

Inoperative components

Higher minimums are prescribed when the specified visual aids are not functioning; this information is listed in the Inoperative Components Table found in the United States Terminal Procedures Publications.

INS

Inertial Navigation System.

Insight

The grouping of perceptions into meaningful wholes. Creating insight is one of the instructor’s major responsibilities.

Insolation

Incoming solar radiation falling upon the earth and its atmosphere.

Instability

A general term to indicate various states of the atmosphere in which spontaneous convection will occur when prescribed criteria are met; indicative of turbulence. Types include: absolute instability, conditionally unstable air, convective instability.

Instantaneous vertical speed indicator (IVSI)

Assists in interpretation by instantaneously indicating the rate of climb or descent at a given moment with little or no lag as displayed in a vertical speed indicator (VSI).

Instantaneous vertical speed indicator (IVSI)

Assists in interpretation by instantaneously indicating the rate of climb or descent at a given moment with little or no lag as displayed in a vertical speed indicator (VSI).

Instructional aids

Devices that assist an instructor in the teaching-learning process. They are supplementary training devices, and are not self-supporting.

Instrument

A device using an internal mechanism to show visually or aurally the attitude, altitude, or operation of an aircraft or aircraft part. It includes electronic devices for automatically controlling an aircraft in flight.

Instrument Approach

Instrument Approach Procedure.

Instrument approach procedure (IAP)

A series of predetermined maneuvers by reference to flight instruments with specified protection from obstacles and assurance of navigation signal reception capability. It begins from the initial approach fix, or where applicable, from the beginning of a defined arrival route to a point:
(1) From which a landing can be completed; or
(2) If a landing is not completed, to a position at which holding or en route obstacle clearance criteria apply.

Instrument approach procedures (IAP)

A series of predetermined maneuvers for the orderly transfer of an aircraft under IFR from the beginning of the initial approach to a landing or to a point from which a landing may be made visually.

Instrument Approach Procedures (IAP) Charts

Portray the aeronautical data which is required to execute an instrument approach to an airport. These charts depict the procedures, including all related data, and the airport diagram. Each procedure is designated for use with a specific type of electronic navigation system including NDB, TACAN, VOR, ILS/MLS, and RNAV. These charts are identified by the type of navigational aid(s) which provide final approach guidance.

Instrument Approach Waypoint

Fixes used in defining RNAV IAPs, including the feeder waypoint (FWP), the initial approach waypoint (IAWP), the intermediate waypoint (IWP), the final approach waypoint (FAWP), the RWY WP, and the APT WP, when required.

Instrument Departure Procedure (DP)

A preplanned instrument flight rule (IFR) departure procedure published for pilot use, in graphic or textual format, that provides obstruction clearance from the terminal area to the appropriate en route structure. There are two types of DP, Obstacle Departure Procedure (ODP), printed either textually or graphically, and, Standard Instrument Departure (SID), which is always printed graphically.

Instrument Departure Procedure (DP) Charts

Designed to expedite clearance delivery and to facilitate transition between takeoff and en route operations. Each DP is presented as a separate chart and may serve a single airport or more than one airport in a given geographical location.

Instrument flight rules (IFR)

Rules and regulations established by the Federal Aviation Administration to govern flight under conditions in which flight by outside visual reference is not safe. IFR flight depends upon flying by reference to instruments in the flight deck, and navigation is accomplished by reference to electronic signals.

Instrument flight rules (IFR)

Instrument Landing System (ILS)

A precision instrument approach system that normally consists of the following electronic components and visual aids; localizer, glide slope, outer marker, middle marker, and approach lights.

Instrument landing system (ILS)

An electronic system that provides both horizontal and vertical guidance to a specific runway, used to execute a precision instrument approach procedure.

Instrument meteorological conditions (IMC)

Meteorological conditions expressed in terms of visibility, distance from clouds, and ceiling less than the minimums specified for visual meteorological conditions, requiring operations to be conducted under IFR.

Instrument meteorological conditions (IMC).

Instrument Procedure with Vertical Guidance (IPV)

Satellite or Flight Management System (FMS) lateral navigation (LNAV) with computed positive vertical guidance based on barometric or satellite elevation. This term has been renamed APV.

Instrument proficiency check

An evaluation ride based on the instrument rating practical test standard which is required to regain instrument flying privileges when the privileges have expired due to lack of currency.

Instrument Runway

A runway equipped with electronic and visual navigation aids for which a precision or nonprecision approach procedure having straight-in landing minimums has been approved.

Instrument takeoff

Using the instruments rather than outside visual cues to maintain runway heading and execute a safe takeoff.

INT

Intersection.

Integral Fuel Tank

A portion of the aircraft structure, usually a wing, which is sealed off and used as a fuel tank. When a wing is used as an integral fuel tank, it is called a “wet wing.”

Integrated flight instruction

A technique of flight instruction in which students are taught to perform flight maneuvers by reference to both the flight instruments and to outside visual references from the time the maneuver is first introduced. Handling of the controls is the same regardless of whether flight instruments or outside references are being used.

Integrity

The ability of a system to provide timely warnings to users when the system should not be used for navigation.

Intensity

A principle of learning in which a dramatic or exciting learning experience is likely to be remembered longer than a boring experience. Students experiencing the real thing will learn more than when they are merely told about the real thing.

Intercooler

A device used to reduce the temperature of the compressed air before it enters the fuel metering device. The resulting cooler air has a higher density, which permits the engine to be operated with a higher power setting.

Interference

(1) A theory of forgetting proposing that a person forgets something because a certain experience overshadows it, or the learning of similar things has intervened. (2) Barriers to effective communication that are caused by physiological, environmental, and psychological factors outside the direct control of the instructor. The instructor must take these factors into account in order to communicate effectively.

Interference drag

Drag generated by the collision of airstreams creating eddy currents, turbulence, or restrictions to smooth flow.

Interference drag

Drag generated by the collision of airstreams creating eddy currents, turbulence, or restrictions to smooth flow.

Intermediate Approach

The segment between the intermediate fix or point and the final approach fix.

Intermediate Approach Segment

Segments Of An Instrument Approach Procedure.

Intermediate Fix

The fix that identifies the beginning of the intermediate approach segment of an instrument approach procedure. The fix is not normally identified on the instrument approach chart as an intermediate fix (IF).

Internal Combustion Engines

An engine that produces power as a result of expanding hot gases from the combustion of fuel and air within the engine itself. A steam engine where coal is burned to heat up water inside the engine is an example of an external combustion engine.

International Airport

Relating to international flight, it means: a. An airport of entry which has been designated by the Secretary of Treasury or Commissioner of Customs as an international airport for customs service. b. A landing rights airport at which specific permission to land must be obtained from customs authorities in advance of contemplated use. c. Airports designated under the Convention on International Civil Aviation as an airport for use by international commercial air transport and/or international general aviation.

International Civil Aviation Organization (ICAO)

ICAO is a specialized agency of the United Nations whose objective is to develop standard principles and techniques of international air navigation and to promote development of civil aviation.

International Civil Aviation Organization [ICAO]

A specialized agency of the United Nations whose objective is to develop the principles and techniques of international air navigation and to foster planning and development of international civil air transport. Regions include: 1. African-Indian Ocean Region 2. Caribbean Region 3. European Region 4. Middle East/Asia Region 5. North American Region 6. North Atlantic Region 7. Pacific Region 8. South American Region

International Flight Information Manual

A publication designed primarily as a pilot’s preflight planning guide for flights into foreign airspace and for flights returning to the U.S. from foreign locations.

International standard atmosphere (IAS)

A model of standard variation of pressure and temperature.

International standard atmosphere (IAS)

A model of standard variation of pressure and temperature.

Interpolate

To determine a value in a series between two known values.

Interpolation

The estimation of an intermediate value of a quantity that falls between marked values in a series. Example: In a measurement of length, with a rule that is marked in eighths of an inch, the value falls between 3/8 inch and 1/2 inch. The estimated (interpolated) value might then be said to be 7/16 inch.

Interrogator

The ground-based surveillance radar beacon transmitter-receiver, which normally scans in synchronism with a primary radar, transmitting discrete radio signals which repetitiously request all transponders on the mode being used to reply. The replies received are mixed with the primary radar returns and displayed on the same plan position indicator (radar scope). Also, applied to the airborne element of the TACAN/DME system.

Intersecting Runways

Two or more runways which cross or meet within their lengths.

Intersection

A. A point defined by any combination of courses, radials, or bearings of two or more navigational aids.
B. Used to describe the point where two runways, a runway and a taxiway, or two taxiways cross or meet.

Intersection Departure

A departure from any runway intersection except the end of the runway.

Intersection Takeoff

Intersection Departure.

Interstage Turbine Temperature (ITT)

The temperature of the gases between the high pressure and low pressure turbines.

Interstate air commerce

The carriage by aircraft of persons or property for compensation or hire, or the carriage of mail by aircraft, or the operation or navigation of aircraft in the conduct or furtherance of a business or vocation, in commerce between a place in any State of the United States, or the District of Columbia, and a place in any other State of the United States, or the District of Columbia; or between places in the same State of the United States through the airspace over any place outside thereof; or between places in the same territory or possession of the United States, or the District of Columbia.

Interstate air transportation

The carriage by aircraft of persons or property as a common carrier for compensation or hire, or the carriage of mail by aircraft in commerce:
(1) Between a place in a State or the District of Columbia and another place in another State or the District of Columbia;
(2) Between places in the same State through the airspace over any place outside that State; or
(3) Between places in the same possession of the United States;
Whether that commerce moves wholly by aircraft of partly by aircraft and partly by other forms of transportation.

Intertropical convergence zone

The boundary zone between the trade wind system of the Northern and Southern Hemispheres; it is characterized in maritime climates by showery precipitation with cumulonimbus clouds sometimes extending to great heights.

Into A.C

Current of the proper voltage and frequency to operate A.C. gyro instruments.

Intrastate air transportation

The carriage of persons or property as a common carrier for compensation or hire, by turbojet-powered aircraft capable of carrying thirty or more persons, wholly within the same State of the United States.

Inversion

An increase in temperature with height-a reversal of the normal decrease with height in the troposphere; may also be applied to other meteorological properties.

Inversion

An increase in temperature with altitude.

Inversion illusion

The feeling that the aircraft is tumbling backwards, caused by an abrupt change from climb to straight- and-level flight while in situations lacking visual reference.

Inversion illusion

The feeling that the aircraft is tumbling backwards, caused by an abrupt change from climb to straight-and-level flight while in situations lacking visual reference.

Inverter

An electrical device that changes DC to AC power.

IPV

Instrument Procedure With Vertical Guidance (This term has been renamed APV)

IR

IFR Military Training Route

IRU

Inertial Reference Unit

ISA (International Standard Atmosphere)

Standard atmospheric conditions consisting of a temperature of 59°F (15°C), and a barometric pressure of 29.92 in. Hg. (1013.2 mb) at sea level. ISA values can be calculated for various altitudes using a standard lapse rate of approximately 2°C per 1,000 feet.

Iso echo

In radar circuitry, a circuit that reverses signal strength above a specified intensity level, thus causing a void on the scope in the most intense portion of an echo when maximum intensity is greater than the specified level.

Isobar

A line of equal or constant barometric pressure.

Isobars

Lines which connect points of equal barometric pressure.

Isogonic lines

Lines drawn across aeronautical charts to connect points having the same magnetic variation.

Isogonic lines

Lines drawn across aeronautical charts to connect points having the same magnetic variation.

Isoheight

On a weather chart, a line of equal height; same as contour (1).

Isoline

A line of equal value of a variable quantity, i.e., an isoline of temperature is an isotherm, etc. Isobars (A line of equal or constant barometric pressure.) and isotachs (A line of equal or constant wind speed.) are examples.

Isoshear

A line of equal wind shear.

Isotach

A line of equal or constant wind speed.

Isotherm

A line of equal or constant temperature.

Isothermal

Of equal or constant temperature, with respect to either space or time; more commonly, temperature with height; a zero lapse rate.

IVSI

Instantaneous Vertical Speed Indicator.

IVSI

Instantaneous Vertical Speed Indicator.

Jamming

Electronic or mechanical interference which may disrupt the display of aircraft on radar or the transmission/reception of radio communications/navigation.

Jet Blast

Jet engine exhaust (thrust stream turbulence).

Jet Powered Airplane

An aircraft powered by a turbojet or turbofan engine.

Jet route

A route designated to serve flight operations from 18,000 feet MSL up to and including FL 450.

Jet Route

A route designed to serve aircraft operations from 18,000 feet MSL up to and including flight level 450. The routes are referred to as “J” routes with numbering to identify the designated route; e.g., J105.

Jet stream

A high-velocity narrow stream of winds, usually found near the upper limit of the troposphere, which flows generally from west to east.

Jet stream

A quasi-horizontal stream of winds 50 knots or more concentrated within a narrow band embedded in the westerlies in the high troposphere.

Jet stream

A high-velocity narrow stream of winds, usually found near the upper limit of the troposphere, which flows generally from west to east.

Judgment

The mental process of recognizing and analyzing all pertinent information in a particular situation, a rational evaluation of alternative actions in response to it, and a timely decision on which action to take.

Judgment

Katabatic wind

Any wind blowing downslope. For example: fall wind, foehn.

Kelvin temperature scale (abbreviated K)

A temperature scale with zero degrees equal to the temperature at which all molecular motion ceases, i.e., absolute zero (0° K = -273° C); the Kelvin degree is identical to the Celsius degree; hence at standard sea level pressure, the melting point is 273° K and the boiling point 373° K.

KHz

Kilohertz

KIAS

Knots Indicated Airspeed.

KIAS

Knots Indicated Airspeed

KIAS

Knots Indicated Airspeed.

Kinesthesia

The sensing of movements by feel.

Kite

A framework, covered with paper, cloth, metal, or other material, intended to be flown at the end of a rope or cable, and having as its only support the force of the wind moving past its surfaces.

Knot

A unit of speed equal to one nautical mile per hour.

Knowledge

Information that humans are consciously aware of and can articulate.

Known Traffic

With respect to ATC clearances, means aircraft whose altitude, position, and intentions are known to ATC.

Known, Observed, or Detected Ice Accretion

Actual ice that is observed visually to be on the aircraft by the flightcrew or identified by onboard sensors.

Kollsman window

A barometric scale window of a sensitive altimeter used to adjust the altitude for the altimeter setting.

Kollsman window

A barometric scale window of a sensitive altimeter used to adjust the altitude for the altimeter setting.

L/MF

Low or Medium Frequency.

L/MF

Low or Medium Frequency.

LAA

Local Airport Advisory

LAADR

Low Altitude Arrival/Departure Routing.

LAAS

Local Area Augmentation System.

LAAS

Local Area Augmentation System

Lack of common experience

In communication, a difficulty which arises because words have different meanings for the source and the receiver of information due to their differing backgrounds.

Lag

The delay that occurs before an instrument needle attains a stable indication.

Lag

The delay that occurs before an instrument needle attains a stable indication.

LAHSO

Land and Hold Short Operations

LAHSO

Land and Hold Short Operations. Operations which include simultaneous takeoffs and landings and/or simultaneous landings when a landing aircraft is able and is instructed by the controller to hold short of the intersecting runway/taxiway or designated hold-short point. Pilots are expected to promptly inform the controller if the hold short clearance cannot be accepted.

Land And Hold Short Operations

Operations which include simultaneous takeoffs and landings and/or simultaneous landings when a landing aircraft is able and is instructed by the controller to hold-short of the intersecting runway/taxiway or designated hold-short point. Pilots are expected to promptly inform the controller if the hold short clearance cannot be accepted.

Land as soon as possible

ATC instruction to pilot. Land without delay at the nearest suitable area, such as an open field, at which a safe approach and landing is assured.

Land as soon as possible

Land without delay at the nearest suitable area, such as an open field, at which a safe approach and landing is assured.

Land as soon as practical

ATC instruction to pilot. The landing site and duration of flight are at the discretion of the pilot. Extended flight beyond the nearest approved landing area is not recommended.

Land as soon as practical

The landing site and duration of flight are at the discretion of the pilot. Extended flight beyond the nearest approved landing area is not recommended.

Land breeze

A coastal breeze blowing from land to sea, caused by temperature difference when the sea surface is warmer than the adjacent land. Therefore, it usually blows at night and alternates with a sea breeze, which blows in the opposite direction by day.

Land immediately

ATC instruction to pilot. The urgency of the landing is paramount. The primary consideration is to ensure the survival of the occupants. Landing in trees, water, or other unsafe areas should be considered only as a last resort.

Land immediately

The urgency of the landing is paramount. The primary consideration is to ensure the survival of the occupants. Landing in trees, water, or other unsafe areas should be considered only as a last resort.

Land-Based Air Defense Identification Zone

An ADIZ over U.S. metropolitan areas, which is activated and deactivated as needed, with dimensions, activation dates and other relevant information disseminated via NOTAM. Note: ADIZ locations and operating and flight plan requirements for civil aircraft operations are specified in 14 CFR Part 99.

Landing Area

Any locality either on land, water, or structures, including airports/heliports and intermediate landing fields, which is used, or intended to be used, for the landing and takeoff of aircraft whether or not facilities are provided for the shelter, servicing, or for receiving or discharging passengers or cargo.

Landing Direction Indicator

A device which visually indicates the direction in which landings and takeoffs should be made.

Landing Distance Available (LDA)

The runway length declared available and suitable for a landing airplane.

Landing gear extended speed

The maximum speed at which an aircraft can be safely flown with the landing gear extended.

Landing gear operating speed

The maximum speed at which the landing gear can be safely extended or retracted.

Landing Minimums

The minimum visibility prescribed for landing a civil aircraft while using an instrument approach procedure. The minimum applies with other limitations set forth in 14 CFR Part 91 with respect to the Minimum Descent Altitude (MDA) or Decision Height (DH) prescribed in the instrument approach procedures as follows: a. Straight-in landing minimums. A statement of MDA and visibility, or DH and visibility, required for a straight-in landing on a specified runway, or b. Circling minimums. A statement of MDA and visibility required for the circle-to-land maneuver. Note: Descent below the established MDA or DH is not authorized during an approach unless the aircraft is in a position from which a normal approach to the runway of intended landing can be made and adequate visual reference to required visual cues is maintained.

Landing Roll

The distance from the point of touchdown to the point where the aircraft can be brought to a stop or exit the runway.

Landing Sequence

The order in which aircraft are positioned for landing.

Landing Weight

The takeoff weight of an aircraft less the fuel burned and/or dumped en route.

Lapse rate

The rate of decrease of an atmospheric variable with height; commonly refers to decrease of temperature with height.

Large

An Aircraft Class Wake Turbulence Separation Minima. Aircraft of more than 41,000 pounds, maximum certificated takeoff weight, up to but not including 300,000 pounds.

Large Aircraft

An aircraft of more than 12,500 pounds, maximum certificated takeoff weight. As defined in 14 CFR part 1.

Last Assigned Altitude

The last altitude/flight level assigned by ATC and acknowledged by the pilot.

Latent heat

The amount of heat absorbed (converted to kinetic energy) during the processes of change of liquid water to water vapor, ice to water vapor, or ice to liquid water; or the amount released during the reverse processes. Four basic classifications are: latent heat of condensation, latent heat of fusion, latent heat of sublimation, and latent heat of vaporization.

Latent heat of condensation

Heat released during change of water vapor to water.

Latent heat of fusion

Heat released during change of water to ice or the amount absorbed in change of ice to water.

Latent heat of sublimation

Heat released during change of water vapor to ice or the amount absorbed in the change of ice to water vapor.

Latent heat of vaporization

Heat absorbed in the change of water to water vapor; the negative of latent heat of condensation.

Lateral Axis

An imaginary line passing through the center of gravity of an airplane and extending across the airplane from wingtip to wingtip.

Lateral axis

An imaginary line passing through the center of gravity of an airplane and extending across the airplane from wingtip to wingtip.

Lateral Navigation (LNAV)

A function of area navigation (RNAV) equipment which calculates, displays, and provides lateral guidance to a profile or path.

Lateral Navigation (LNAV)

A function of area navigation (RNAV) equipment which calculates, displays, and provides lateral guidance to a profile or path.

Lateral Offset Moment

The moment, in lb-in, of a force that tends to rotate a helicopter about its longitudinal axis. The lateral offset moment is the product of the weight of the object and its distance from butt line zero. Lateral offset moments that tend to rotate the aircraft clockwise are positive, and those that tend to rotate it counterclockwise are negative.

Lateral Separation

The lateral spacing of aircraft at the same altitude by requiring operation on different routes or in different geographical locations.

Lateral Stability (Rolling)

The stability about the longitudinal axis of an aircraft. Rolling stability or the ability of an airplane to return to level flight due to a disturbance that causes one of the wings to drop.

Latitude

Measurement north or south of the equator in degrees, minutes, and seconds. Lines of latitude are also referred to as parallels.

Layer

In reference to sky cover, clouds or other obscuring phenomena whose bases are approximately at the same level. The layer may be continuous or composed of detached elements. The term “layer” does not imply that a clear space exists between the layers or that the clouds or obscuring phenomena composing them are of the same type.

LDA

Localizer-type Directional Aid.

LDA/PRM

Localizer Type Directional Aid/Precision Runway Monitor

LDIN

Lead-In-Light System. Consists Of One Or More Series Of Flashing Lights Installed At Or Near Ground Level That Provides Positive Visual Guidance Along An Approach Path, Either Curving Or Straight, Where Special Problems Exist With Hazardous Terrain, Obstructions, Or Noise Abatement Procedures

Lead radial

The radial at which the turn from the DME arc to the inbound course is started.

Lead-Acid Battery

A commonly used secondary cell having lead as its negative plate and lead peroxide as its positive plate. Sulfuric acid and water serve as the electrolyte.

Lead-off question

In the guided discussion method, a question used by an instructor to open up an area for discussion and get the discussion started.

Leading Edge

The part of an airfoil that meets the airflow first.

Leading edge

The part of an airfoil that meets the airflow first.

Leading Edge Devices

High lift devices which are found on the leading edge of the airfoil. The most common types are fixed slots, movable slats, and leading edge flaps.

Leading Edge Flap

A portion of the leading edge of an airplane wing that folds downward to increase the camber, lift, and drag of the wing. The leading-edge flaps are extended for takeoffs and landings to increase the amount of aerodynamic lift that is produced at any given airspeed.

Lean of Peak

A mixture setting where the mixture was leaned from the full-rich fuel flow position to lean of peak exhaust gas temperature (EGT).

Leans, the

A physical sensation caused by an abrupt correction of a banked attitude entered too slowly to stimulate the motion sensing system in the inner ear. The abrupt correction can create the illusion of banking in the opposite direction.

Leans, the

Learning

A change in behavior as a result of experience.

Learning plateau

A learning phenomenon where progress appears to cease or slow down for a significant period of time before once again increasing.

Learning style

Preferred way(s) by which people learn. Common learning styles include visual, auditory, and kinesthetic, or tactile (hands on). Learning skills can be loosely grouped into physical and cognitive styles.

Learning theory

A body of principles advocated by psychologists and educators to explain how people acquire skills, knowledge, and attitudes.

Lecture method

An educational presentation usually delivered by an instructor to a group of students with the use of instructional aids and training devices. Lectures are useful for the presentation of new material, summarizing ideas, and showing relationships between theory and practice.

Lee wave

Any stationary wave disturbance caused by a barrier in a fluid flow. In the atmosphere when sufficient moisture is present, this wave will be evidenced by lenticular clouds to the lee of mountain barriers; also called mountain wave or standing wave.

Left Base Area

A type of Terminal Arrival Area. A 30NM arc centered on the right corner IAF (Initial Approach Fix). The area shares a boundary with the straight-in area except that it extends out for 30NM from the IAF and is bounded on the other side by a line extending from the IF through the FAF to the arc.

LEMAC

Leading Edge of the Mean Aerodynamic Chord.

Lenticular cloud (or lenticularis)

A species of cloud whose elements have the form of more or less isolated, generally smooth lenses or almonds. These clouds appear most often in formations of orographic origin, the result of lee waves, in which case they remain nearly stationary with respect to the terrain (standing cloud), but they also occur in regions without marked orography.

Lesson plan

An organized outline for a single instructional period. It is a necessary guide for the instructor in that it tells what to do, in what order to do it, and what procedure to use in teaching the material of a lesson.

Level of free convection (abbreviated LFC)

The level at which a parcel of air lifted dry-adiabatically until saturated and moist-adiabatically thereafter would become warmer than its surroundings in a conditionally unstable atmosphere.

LF

Low Frequency

LFR

Low-Frequency Radio Range.

Licensed Empty Weight

The empty weight that consists of the airframe, engine(s), unusable fuel, and undrainable oil plus standard and optional equipment as specified in the equipment list. Some manufacturers used this term prior to GAMA standardization.

Licensed empty weight

Lift

One of the four main forces acting on an aircraft. On a fixed-wing aircraft, an upward force created by the effect of airflow as it passes over and under the wing.

Lift

A component of the total aerodynamic force on an airfoil and acts perpendicular to the relative wind.

Lift

A component of the total aerodynamic force on an airfoil and acts perpendicular to the relative wind.

Lift Coefficient

A coefficient representing the lift of a given airfoil. Lift coefficient is obtained by dividing the lift by the free-stream dynamic pressure and the representative area under consideration.

Lift-Off

The act of becoming airborne as a result of the wings lifting the airplane off the ground, or the pilot rotating the nose up, increasing the angle of attack to start a climb.

Lift/Drag Ratio

The efficiency of an airfoil section. It is the ratio of the coefficient of lift to the coefficient of drag for any given angle of attack.

Lifting condensation level (abbreviated LCL)

The level at which a parcel of unsaturated air lifted dry-adiabatically would become saturated. Compare level of free convection and convective condensation level.

Light Gun

A handheld directional light signaling device which emits a brilliant narrow beam of white, green, or red light as selected by the tower controller. The color and type of light transmitted can be used to approve or disapprove anticipated pilot actions where radio communication is not available. The light gun is used for controlling traffic operating in the vicinity of the airport and on the airport movement area.

Light Icing

The rate of accumulation may create a problem if flight is prolonged in this environment (over 1 hour). Occasional use of deicing/anti-icing equipment removes/prevents accumulation. It does not present a problem if the deicing/anti-icing equipment is used.

Light Icing

The rate of ice accumulation may create a problem if flight is prolonged in this environment (over 1 hour). Requires occasional cycling of manual deicing systems1 to minimize ice accretions on the airframe. A representative accretion rate for reference purposes is 1⁄4 inch to 1 inch (0.6 to 2.5 cm) per hour on the outer wing.

Light-sport aircraft

An aircraft, other than a helicopter or powered-lift that, since its original certification, has continued to meet the following:
(1) A maximum takeoff weight of not more than—
(i) 1,320 pounds (600 kilograms) for aircraft not intended for operation on water; or
(ii) 1,430 pounds (650 kilograms) for an aircraft intended for operation on water.
(2) A maximum airspeed in level flight with maximum continuous power (Vh) of not more than 120 knots CAS under standard atmospheric conditions at sea level.
(3) A maximum never-exceed speed (Vne) of not more than 120 knots CAS for a glider.
(4) A maximum stalling speed or minimum steady flight speed without the use of lift-enhancing devices (Vs1) of not more than 45 knots CAS at the aircraft’s maximum certificated takeoff weight and most critical center of gravity.
(5) A maximum seating capacity of no more than two persons, including the pilot.
(6) A single, reciprocating engine, if powered.
(7) A fixed or ground-adjustable propeller if a powered aircraft other than a powered glider.
(8) A fixed or feathering propeller system if a powered glider.
(9) A fixed-pitch, semi-rigid, teetering, two-blade rotor system, if a gyroplane.
(10) A non-pressurized cabin, if equipped with a cabin.
(11) Fixed landing gear, except for an aircraft intended for operation on water or a glider.
(12) Fixed or retractable landing gear, or a hull, for an aircraft intended for operation on water.
(13) Fixed or retractable landing gear for a glider.

Lighted Airport

An airport where runway and obstruction lighting is available.

Lighter-than-air aircraft

Aircraft that can rise and remain suspended by using contained gas weighing less than the air that is displaced by the gas.

Lightning

Generally, any and all forms of visible electrical discharge produced by a thunderstorm.

Limit Load Factor

Amount of stress, or load factor, that an aircraft can withstand before structural damage or failure occurs.

Line Up And Wait (LUAW)

Used by ATC to inform a pilot to taxi onto the departure runway to line up and wait. It is not authorization for takeoff. It is used when takeoff clearance cannot immediately be issued because of traffic or other reasons.

Lines of flux

Invisible lines of magnetic force passing between the poles of a magnet.

Lines of flux

Invisible lines of magnetic force passing between the poles of a magnet.

Liquid Water Content (LWC)

The total mass of water in all the liquid cloud drops within a unit volume of cloud. LWC is usually discussed in terms of grams of water per cubic meter of air (g/m3).

LIRL

Low Intensity Runway Lights

Lithometeor

The general term for dry particles suspended in the atmosphere such as dust, haze, smoke, and sand.

LLWAS

Low Level Wind Shear Alert System

LMM

Locator Middle Marker.

LNAV

Lateral Navigation

LO CIGS

Low Ceilings. Low clouds.

LOA

Letter Of Agreement/Letter Of Authorization

Load Cell

A component in an electronic weighing system that is placed between the jack and the jack pad on the aircraft. The load cell contains strain gauges whose resistance changes with the weight on the cell.

Load Factor

The ratio of the load supported by the airplane’s wings to the actual weight of the aircraft and its contents. Also referred to as G-loading.

Load factor

The ratio of a specified load to the total weight of the aircraft. The specified load is expressed in terms of any of the following: aerodynamic forces, inertial forces, or ground or water reactions.

Load factor

The ratio of a specified load to the total weight of the aircraft. The specified load is expressed in terms of any of the following: aerodynamic forces, inertial forces, or ground or water reactions.

Loading Graph

A graph of load weight and load moment indexes. Diagonal lines for each item relate the weight to the moment index without having to use mathematics.

Loading Schedule

A method for calculating and documenting aircraft weight and balance prior to taxiing, to ensure the aircraft will remain within all required weight and balance limitations throughout the flight.

Loadmeter

A type of ammeter installed between the generator output and the main bus in an aircraft electrical system.

Loadmeter

A type of ammeter installed between the generator output and the main bus in an aircraft electrical system.

LOC

Localizer.

LOC

Localizer. The component of an ILS that provides course guidance to the runway.

Local Traffic

Aircraft operating in the traffic pattern or within sight of the tower, or aircraft known to be departing or arriving from flight in local practice areas, or aircraft executing practice instrument approaches at the airport.

Localizer (LOC)

The portion of an ILS that gives left/right guidance information down the centerline of the instrument runway for final approach.

Localizer (LOC)

The portion of an ILS that gives left/right guidance information down the centerline of the instrument runway for final approach.

Localizer Performance with Vertical Guidance (LPV)

LPV is one of the four lines of approach minimums found on an RNAV (GPS) approach chart. Lateral guidance accuracy is equivalent to a localizer. The HAT is published as a DA since it uses an electronic glide path that is not dependent on any ground equipment or barometric aiding and may be as low as 200 feet and 1/2 SM visibility depending on the airport terrain and infrastructure. WAAS avionics approved for LPV is required. Baro-VNAV is not authorized to fly the LPV line of minimums on a RNAV (GPS) procedure since it uses an internally generated descent path that is subject to cold temperature effects and incorrect altimeter settings.

Localizer Usable Distance

The maximum distance from the localizer transmitter at a specified altitude, as verified by flight inspection, at which reliable course information is continuously received.

Localizer-type directional aid (LDA)

A NAVAID used for nonprecision instrument approaches with utility and accuracy comparable to a localizer but which is not a part of a complete ILS and is not aligned with the runway. Some LDAs are equipped with a glide slope.

Locator middle marker (LMM)

Nondirectional radio beacon (NDB) compass locator, collocated with a middle marker (MM).

Locator outer marker (LOM)

NDB compass locator, collocated with an outer marker (OM).

LOM

Locator Outer Marker.

Long Range Navigation

LORAN. [Decommissioned in 2010]

Long range navigation (LORAN)

[Decommissioned in 2010] An electronic navigational system by which hyperbolic lines of position are determined by measuring the difference in the time of reception of synchronized pulse signals from two fixed transmitters. LORAN A operates in the 1750 to 1950 kHz frequency band. LORAN C and D operate in the 100 to 110 kHz frequency band.

Long range navigation (LORAN)

[Decommissioned in 2010] An electronic navigational system by which hyperbolic lines of position are determined by measuring the difference in the time of reception of synchronized pulse signals from two fixed transmitters. LORAN-A operates in the 1750–1950 kHz frequency band. LORAN-C and -D operate in the 100–110 kHz frequency band.

Long-range communication system (LRCS)

A system that uses satellite relay, data link, high frequency, or another approved communication system which extends beyond line of sight.

Long-range navigation system (LRNS)

An electronic navigation unit that is approved for use under instrument flight rules as a primary means of navigation, and has at least one source of navigational input, such as inertial navigation system, global positioning system, Omega/very low frequency, or Loran C.

Long-term memory

The portion of the brain that stores information that has been determined to be of sufficient value to be retained. In order for it to be retained in longterm memory, it must have been processed or coded in the working memory.

Longitude

Measurement east or west of the Prime Meridian in degrees, minutes, and seconds. The Prime Meridian is 0° longitude and runs through Greenwich, England. Lines of longitude are also referred to as meridians.

Longitudinal Axis

An imaginary line through an aircraft from nose to tail, passing through its center of gravity. The longitudinal axis is also called the roll axis of the aircraft. Movement of the ailerons rotates an airplane about its longitudinal axis.

Longitudinal Axis

An imaginary line through an aircraft from nose to tail, passing through its center of gravity.

Longitudinal axis

Longitudinal Balance

Balance around the pitch, or lateral, axis.

Longitudinal Separation

The longitudinal spacing of aircraft at the same altitude by a minimum distance expressed in units of time or miles.

Longitudinal Stability (Pitching)

Stability about the lateral axis. A desirable characteristic of an airplane whereby it tends to return to its trimmed angle of attack after displacement.

Longitudinal stability (pitching)

Stability about the lateral axis. A desirable characteristic of an airplane whereby it tends to return to its trimmed angle of attack after displacement.

LOP

Line-of-position

LOP

Lean of Peak

LORAN

Long Range Navigation. [Decommissioned in 2010]

LORAN

Long Range Navigation System [Decommissioned in 2010]

LORAN-C

[Decommissioned in 2010] A radio navigation system that utilizes master and slave stations transmitting timed pulses. The time difference in reception of pulses from several stations establishes a hyperbolic line of position, which can be identified on a LORAN chart. A fix in position is obtained by utilizing signals from two or more stations.

Loss of Separation

An occurrence or operation that results in less than prescribed separation between aircraft, or between an aircraft and a vehicle, pedestrian, or object.

Lost Communications

Loss of the ability to communicate by radio. Aircraft are sometimes referred to as NORDO (No Radio). Standard pilot procedures are specified in 14 CFR Part 91. Radar controllers issue procedures for pilots to follow in the event of lost communications during a radar approach when weather reports indicate that an aircraft will likely encounter IFR weather conditions during the approach.

Low

An area of low barometric pressure, with its attendant system of winds. Also called a barometric depression or cyclone.

Low Altitude Airway Structure

The network of airways serving aircraft operations up to but not including 18,000 feet MSL.

Low Altitude Alert System

An automated function of the TPX-42 that alerts the controller when a Mode C transponder equipped aircraft on an IFR flight plan is below a predetermined minimum safe altitude. If requested by the pilot, Low Altitude Alert System monitoring is also available to VFR Mode C transponder equipped aircraft.

Low Altitude Alert, Check Your Altitude Immediately

Safety Alert.

Low Approach

An approach over an airport or runway following an instrument approach or a VFR approach including the go-around maneuver where the pilot intentionally does not make contact with the runway.

Low Frequency

The frequency band between 30 and 300 kHz.

Low Level Autorotation

Commences at an altitude well below the traffic pattern, usually below 100 feet AGL and is used primarily for tactical military training.

Low or medium frequency

A frequency range between 190-535 kHz with the medium frequency above 300 kHz. Generally associated with nondirectional beacons transmitting a continuous carrier with either a 400 or 1,020 Hz modulation.

Low or medium frequency

A frequency range between 190 and 535 kHz with the medium frequency above 300 kHz. Generally associated with nondirectional beacons transmitting a continuous carrier with either a 400 or 1,020 Hz modulation.

LP

Localizer Performance

LPV

A Type Of Approach With Vertical Guidance (APV) Based On Waas, Published On RNAV (GPS) Approach Charts. This Procedure Takes Advantage Of The Precise Lateral Guidance Available From Waas. The Minima Is Published As A Decision Altitude (DA)

LTP

Landing Threshold Point

LUAW

Line Up and Wait

LUAW

Line Up And Wait

Lubber line

The reference line used in a magnetic compass or heading indicator.

Lubberline

The reference line used in a magnetic compass or heading indicator.

LZ

Landing Zone

M

Mach Number.

MAA

Maximum Authorized Ifr Altitude.

MAC

Mean Aerodynamic Chord.

Mach

Speed relative to the speed of sound. Mach 1 is the speed of sound.

Mach Buffet

Airflow separation behind a shock-wave pressure barrier caused by airflow over flight surfaces exceeding the speed of sound.

Mach Compensating Device

A device to alert the pilot of inadvertent excursions beyond its certified maximum operating speed.

Mach Critical

The MACH speed at which some portion of the airflow over the wing first equals MACH 1.0. This is also the speed at which a shock wave first appears on the airplane.

Mach meter

The instrument that displays the ratio of the speed of sound to the true airspeed an aircraft is flying.

Mach number

The ratio of the true airspeed of the aircraft to the speed of sound in the same atmospheric conditions, named in honor of Ernst Mach, late 19th century physicist.

Mach number

The ratio of true airspeed to the speed of sound.

Mach number

The ratio of the true airspeed of the aircraft to the speed of sound in the same atmospheric conditions, named in honor of Ernst Mach, late 19th century physicist.

Mach Technique [ICAO]

Describes a control technique used by air traffic control whereby turbojet aircraft operating successively along suitable routes are cleared to maintain appropriate MACH numbers for a relevant portion of the en route phase of flight. The principle objective is to achieve improved utilization of the airspace and to ensure that separation between successive aircraft does not decrease below the established minima.

Mach Tuck

A condition that can occur when operating a swept-wing airplane in the transonic speed range. A shock wave could form in the root portion of the wing and cause the air behind it to separate. This shock-induced separation causes the center of pressure to move aft. This, combined with the increasing amount of nose down force at higher speeds to maintain level flight, causes the nose to “tuck.” If not corrected, the airplane could enter a steep, sometimes unrecoverable dive.

Magnetic bearing (MB)

The direction to or from a radio transmitting station measured relative to magnetic north.

Magnetic bearing (MB)

The direction to or from a radio transmitting station measured relative to magnetic north.

Magnetic Compass

A device for determining direction measured from magnetic north.

Magnetic compass

A device for determining direction measured from magnetic north.

Magnetic Course

A predetermined desired course direction to be followed (measured in degrees from local magnetic north).

Magnetic dip

A vertical attraction between a compass needle and the magnetic poles. The closer the aircraft is to a pole, the more severe the effect.

Magnetic heading (MH)

The direction an aircraft is pointed with respect to magnetic north.

Magnetic heading (MH)

The direction an aircraft is pointed with respect to magnetic north.

Magnetic Variation

The difference in degrees between the measured values of true north and magnetic north at that location.

Magneto

A self-contained, engine-driven unit that supplies electrical current to the spark plugs; completely independent of the airplane’s electrical system. Normally there are two magnetos per engine.

Magnus effect

Lifting force produced when a rotating cylinder produces a pressure differential. This is the same effect that makes a baseball curve or a golf ball slice.

MAHWP

Missed Approach Holding Waypoint

Main Gear

The wheels of an aircraft’s landing gear that supports the major part of the aircraft’s weight.

Main rotor

The rotor that supplies the principal lift to a rotorcraft.

Maintain

A. Concerning altitude/flight level, the term means to remain at the altitude/flight level specified. The phrase “climb and” or “descend and” normally precedes “maintain” and the altitude assignment; e.g., “descend and maintain 5,000.”
B. Concerning other ATC instructions, the term is used in its literal sense; e.g., maintain VFR.

Maintenance

Inspection, overhaul, repair, preservation, and the replacement of parts, but excludes preventive maintenance.

Major alteration

An alteration not listed in the aircraft, aircraft engine, or propeller specifications—
(1) That might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness; or
(2) That is not done according to accepted practices or cannot be done by elementary operations.

Major repair

A repair:
(1) That, if improperly done, might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness; or
(2) That is not done according to accepted practices or cannot be done by elementary operations.

Make Short Approach

Used by ATC to inform a pilot to alter his/her traffic pattern so as to make a short final approach.

MALS

Medium Intensity Approach Light System.

MALSF

Medium Intensity Approach Light System With Sequenced Flashing Lights

MALSR

Medium Intensity Approach Light System with Runway Alignment Indicator Lights.

Mammato cumulus

Obsolete. Now referred to as cumulonimbus mamma.

Man Portable Air Defense Systems (MANPADS)

MANPADS are lightweight, shoulder-launched, missile systems used to bring down aircraft and create mass casualties. The potential for MANPADS use against airborne aircraft is real and requires familiarity with the subject. Terrorists choose MANPADS because the weapons are low cost, highly mobile, require minimal set-up time, and are easy to use and maintain. Although the weapons have limited range, and their accuracy is affected by poor visibility and adverse weather, they can be fired from anywhere on land or from boats where there is unrestricted visibility to the target.

Mandatory altitude

An altitude depicted on an instrument approach chart with the altitude value both underscored and overscored. Aircraft are required to maintain altitude at the depicted value.

Mandatory block altitude

An altitude depicted on an instrument approach chart with two underscored and overscored altitude values between which aircraft are required to maintain altitude.

Maneuverability

Ability of an aircraft to change directions along a flightpath and withstand the stresses imposed upon it.

Maneuvering Speed (Va)

The maximum speed where full, abrupt control movement can be used without overstressing the airframe.

Maneuvering speed (Va)

The maximum speed at which full, abrupt control movement can be used without overstressing the airframe.

Manifold absolute pressure

The absolute pressure of the fuel/air mixture within the intake manifold, usually indicated in inches of mercury.

Manifold Pressure (MP)

The absolute pressure of the fuel/air mixture within the intake manifold, usually indicated in inches of mercury.

MANPADS

Man Portable Air Defense Systems

MAP

Missed Approach Point.

Mare’s tail

Irregularly curved wisps of cirriform clouds.

Margin identification

The top and bottom areas on an instrument approach chart that depict information about the procedure, including airport location and procedure identification.

Maritime polar air (abbreviated mP)

Also called polar air. An air mass with characteristics developed over high latitudes, especially within the subpolar highs. Maritime polar (mP) initially possesses similar properties to those of continental polar air, but in passing over warmer water it becomes unstable with a higher moisture content.

Maritime tropical air (abbreviated mT)

Also called tropical air. An air mass with characteristics developed over low latitudes. Maritime tropical air (mT), the principal type, is produced over the tropical and subtropical seas; very warm and humid.

Marker beacon

A low-powered transmitter that directs its signal upward in a small, fan-shaped pattern. Used along the flight path when approaching an airport for landing, marker beacons indicate both aurally and visually when the aircraft is directly over the facility.

Mass

The amount of matter in a body.

Matching-type test item

A test item in which the student is asked to match alternatives on one list to related alternatives on a second list. The lists may include words, terms, illustrations, phrases, or sentences.

MAWP

Missed Approach Waypoint

Maximum Allowable Takeoff Power

The maximum power an engine is allowed to develop for a limited period of time; usually about one minute.

Maximum altitude

An altitude depicted on an instrument approach chart with overscored altitude value at which or below aircraft are required to maintain altitude.

Maximum Authorized Altitude (MAA)

An MAA is a published altitude representing the maximum usable altitude or flight level for an airspace structure or route segment. It is the highest altitude on a Federal airway, jet route, RNAV low or high route, or other direct route for which an MEA is designated at which adequate reception of navigation signals is assured.

Maximum engine overtorque

As it applies to turbopropeller and turboshaft engines incorporating free power turbines for all ratings except one engine inoperative (OEI) ratings of two minutes or less, the maximum torque of the free power turbine rotor assembly, the inadvertent occurrence of which, for periods of up to 20 seconds, will not require rejection of the engine from service, or any maintenance action other than to correct the cause. Maximum speed for stability characteristics, V FC/MFC means a speed that may not be less than a speed midway between maximum operating limit speed (VMO/MMO) and demonstrated flight diving speed (VDF/MDF), except that, for altitudes where the Mach number is the limiting factor, MFC need not exceed the Mach number at which effective speed warning occurs.

Maximum Landing Weight

The greatest weight that an airplane normally is allowed to have at landing.

Maximum Permissible Hoist Load

The maximum external load that is permitted for a helicopter to carry. This load is specified in the POH.

Maximum Ramp Weight

The total weight of a loaded aircraft, including all fuel. It is greater than the takeoff weight due to the fuel that will be burned during the taxi and runup operations. Ramp weight may also be referred to as taxi weight.

Maximum Takeoff Weight

(GAMA) Maximum weight approved for the start of the takeoff run.

Maximum Weight

The maximum authorized weight of the aircraft and all of its equipment as specified in the Type Certificate Data Sheets (TCDS) for the aircraft.

Maximum weight

The maximum authorized weight of the aircraft and all of its equipment as specified in the Type Certificate Data Sheets (TCDS) for the aircraft.

Maximum wind axis

On a constant pressure chart, a line denoting the axis of maximum wind speeds at that constant pressure surface.

Maximum Zero Fuel Weight

The maximum authorized weight of an aircraft without fuel. This is the total weight for a particular flight less the fuel. It includes the aircraft and everything that will be carried on the flight except the weight of the fuel.

Mayday

The international radiotelephony distress signal. When repeated three times, it indicates imminent and grave danger and that immediate assistance is requested.

MB

Magnetic Bearing.

MB

Magnetic Bearing.

MCA

Minimum Crossing Altitude.

MDA

Minimum Descent Altitude.

MDH

Minimum Descent Height

MEA

Minimum Enroute Altitude.

Mean aerodynamic chord (MAC)

The average distance from the leading edge to the trailing edge of the wing.

Mean sea level

The average height of the surface of the sea at a particular location for all stages of the tide over a 19-year period.

Mean sea level

The average height of the surface of the sea for all stages of tide; used as reference for elevations throughout the U.S.

Mean sea level

The average height of the surface of the sea at a particular location for all stages of the tide over a 19-year period.

Measured ceiling

A ceiling classification applied when the ceiling value has been determined by instruments or the known heights of unobscured portions of objects, other than natural landmarks.

Median Volume Diameter (MVD)

The diameter such that half the liquid water in a region of cloud is contained in drops of a smaller diameter, and half in drops of a larger diameter.

Medical certificate

Acceptable evidence of physical fitness on a form prescribed by the Administrator.

MEL

Minimum Equipment List

MEL

Minimum Equipment List.

MEL

Minimum Equipment List.

Melting

The change of ice to liquid water.

Memory

The ability of people and other organisms to encode (initial perception and registration of information), store (retention of encoded information over time), and retrieve (processes involved in using stored information) information.

Mercurial barometer

A barometer in which pressure is determined by balancing air pressure against the weight of a column of mercury in an evacuated glass tube.

Meridians

Lines of longitude.

Mesophere

A layer of the atmosphere directly above the stratosphere.

METAR

Aviation Routine Weather Report

METAR

Aviation Routine Weather Report

METAR

Aviation Routine Weather Report.

Meteorological visibility

In U.S. observing practice, a main category of visibility which includes the subcategories of prevailing visibility and runway visibility. Meteorological visibility is a measure of horizontal visibility near the earth’s surface, based on sighting of objects in the daytime or unfocused lights of moderate intensity at night. Compare slant visibility, runway visual range, vertical visibility. Examples are surface visibility, tower visibility, and sector visibility.

Meteorology

The science of the atmosphere.

Metering

A method of time-regulating arrival traffic flow into a terminal area so as not to exceed a predetermined terminal acceptance rate.

Metering Fix

A fix along an established route over which aircraft will be metered prior to entering terminal airspace. Normally, this fix should be established at a distance from the airport which will facilitate a profile descent 10,000 feet above airport elevation (AAE) or above.

Metering Fix

A fix along an established route from over which aircraft will be metered prior to entering terminal airspace. Normally, this fix should be established at a distance from the airport which will facilitate a profile descent 10,000 feet above airport elevation (AAE) or above.

METO Horsepower (maximum except takeoff)

The maximum power allowed to be continuously produced by an engine. Takeoff power is usually limited to a given amount of time, such as 1 minute or 5 minutes.

MFD

Multi-Function Display.

MFD

Multi-Function Display.

MH

Magnetic Heading.

MH

Magnetic Heading.

MHA

Minimum Holding Altitude

MHz

Megahertz.

MHz

Megahertz

MIA

Minimum IFR Altitude

Microbarograph

An aneroid barograph designed to record atmospheric pressure changes of very small magnitudes.

Microburst

A strong downdraft which normally occurs over horizontal distances of 1 NM or less and vertical distances of less than 1,000 feet. In spite of its small horizontal scale, an intense microburst could induce windspeeds greater than 100 knots and downdrafts as strong as 6,000 feet per minute.

Microwave landing system (MLS)

A precision instrument approach system operating in the microwave spectrum which normally consists of an azimuth station, elevation station, and precision distance measuring equipment.

Mid-RVR

The RVR readout values obtained from sensors located midfield of the runway.

Middle Compass Locator (LMM)

A compass locator installed at the site of the middle marker of an instrument landing system.

Middle Marker

A marker beacon that defines a point along the glideslope of an ILS normally located at or near the point of decision height (ILS Category I). It is keyed to transmit alternate dots and dashes, with the alternate dots and dashes keyed at the rate of 95 dot/dash combinations per minute on a 1300 Hz tone, which is received aurally and visually by compatible airborne equipment.

Mileage Break

A point on a route where the leg segment mileage ends, and a new leg segment mileage begins, often at a route turning point.

Mileage breakdown

A fix indicating a course change that appears on the chart as an x at a break between two segments of a federal airway.

Mileage breakdown

A fix indicating a course change that appears on the chart as an “x” at a break between two segments of a federal airway.

Miles-In-Trail

A specified distance between aircraft, normally, in the same stratum associated with the same destination or route of flight.

Military Landing Zone

A landing strip used exclusively by the military for training. A military landing zone does not carry a runway designation.

Military operations area

A military operations area (MOA) is airspace established outside Class A airspace to separate or segregate certain nonhazardous military activities from IFR Traffic and to identify for VFR traffic where theses activities are conducted.

Military operations area (MOA)

Airspace established for the purpose of separating certain military training activities from IFR traffic.

Military Operations Area (MOA)

A MOA is airspace established outside of Class A airspace area to separate or segregate certain nonhazardous military activities from IFR traffic and to identify for VFR traffic where these activities are conducted.

Military training route (MTR)

Airspace of defined vertical and lateral dimensions established for the conduct of military training at airspeeds in excess of 250 knots indicated airspeed (KIAS).

Military training route (MTR)

Airspace of defined vertical and lateral dimensions established for the conduct of military training at airspeeds in excess of 250 knots indicated airspeed (KIAS).

Millibar (abbreviated mb.)

An internationally used unit of pressure equal to 1,000 dynes per square centimeter. It is convenient for reporting atmospheric pressure.

Minima

Minimums.

Minimum altitude

An altitude depicted on an instrument approach chart with the altitude value underscored. Aircraft are required to maintain altitude at or above the depicted value.

Minimum Controllable Airspeed

An airspeed at which any further increase in angle of attack, increase in load factor, or reduction in power, would result in an immediate stall.

Minimum Crossing Altitude (MCA)

An MCA is the lowest altitude at certain fixes at which the aircraft must cross when proceeding in the direction of a higher minimum en route IFR altitude. MCAs are established in all cases where obstacles intervene to prevent pilots from maintaining obstacle clearance during a normal climb to a higher MEA after passing a point beyond which the higher MEA applies.

Minimum descent altitude (MDA)

The lowest altitude specified in a [nonprecision] instrument approach procedure, expressed in feet above mean sea level, to which descent is authorized on final approach or during circle-to-land maneuvering until the pilot sees the required visual references for the heliport or runway of intended landing.

Minimum drag

The point on the total drag curve where the lift-to-drag ratio is the greatest. At this speed, total drag is minimized.

Minimum En Route Altitude (MEA)

The MEA is the lowest published altitude between radio fixes that assures acceptable navigational signal coverage and meets obstacle clearance requirements between those fixes. The MEA prescribed for a Federal airway or segment, RNAV low or high route, or other direct route applies to the entire width of the airway, segment, or route between the radio fixes defining the airway, segment, or route.

Minimum equipment list (MEL)

A list developed for larger aircraft that outlines equipment that can be inoperative for various types of flight including IFR and icing conditions. This list is based on the master minimum equipment list (MMEL) developed by the FAA and must be approved by the FAA for use. It is specific to an individual aircraft make and model.

Minimum Fuel

The amount of fuel necessary for one- half hour of operation at the rated maximum-continuous power setting of the engine, which, for weight and balance purposes, is 1/12 gallon per maximum-except-takeoff (METO) horse-power. It is the maximum amount of fuel that could be used in weight and balance computations when low fuel might adversely affect the most critical balance conditions. To determine the weight of the minimum fuel in pounds, divide the METO horsepower by two.

Minimum Fuel

Indicates that an aircraft’s fuel supply has reached a state where, upon reaching the destination, it can accept little or no delay. This is not an emergency situation but merely indicates an emergency situation is possible should any undue delay occur.

Minimum Holding Altitude

The lowest altitude prescribed for a holding pattern which assures navigational signal coverage, communications, and meets obstacle clearance requirements.

Minimum IFR Altitudes (MIA)

Minimum altitudes for IFR operations as prescribed in 14 CFR Part 91. These altitudes are published on aeronautical charts and prescribed in 14 CFR Part 95 for airways and routes, and in 14 CFR Part 97 for standard instrument approach procedures. If no applicable minimum altitude is prescribed in 14 CFR Part 95 or 14 CFR Part 97, the following minimum IFR altitude applies: a. In designated mountainous areas, 2,000 feet above the highest obstacle within a horizontal distance of 4 nautical miles from the course to be flown; or b. Other than mountainous areas, 1,000 feet above the highest obstacle within a horizontal distance of 4 nautical miles from the course to be flown; or c. As otherwise authorized by the Administrator or assigned by ATC.

Minimum Navigation Performance Specification

A set of standards which require aircraft to have a minimum navigation performance capability in order to operate in MNPS designated airspace. In addition, aircraft must be certified by their State of Registry for MNPS operation.

Minimum Navigation Performance Specification Airspace

Designated airspace in which MNPS procedures are applied between MNPS certified and equipped aircraft. Under certain conditions, non-MNPS aircraft can operate in MNPSA. However, standard oceanic separation minima is provided between the non-MNPS aircraft and other traffic. Currently, the only designated MNPSA is described as follows: a. Between FL 285 and FL 420; b. Between latitudes 27°N and the North Pole; c. In the east, the eastern boundaries of the CTAs Santa Maria Oceanic, Shanwick Oceanic, and Reykjavik; d. In the west, the western boundaries of CTAs Reykjavik and Gander Oceanic and New York Oceanic excluding the area west of 60°W and south of 38°30’N.

Minimum obstruction clearance altitude (MOCA)

The lowest published altitude in effect between radio fixes on VOR airways, off-airway routes, or route segments, which meets obstacle clearance requirements for the entire route segment and which ensures acceptable navigational signal coverage only within 25 statute (22 nautical) miles of a VOR.

Minimum Reception Altitude (MRA)

An MRA is determined by FAA flight inspection traversing an entire route of flight to establish the minimum altitude the navigation signal can be received for the route and for off-course NAVAID facilities that determine a fix. When the MRA at the fix is higher than the MEA, an MRA is established for the fix, and is the lowest altitude at which an intersection can be determined.

Minimum Safe Altitude Warning

A function of the ARTS III computer that aids the controller by alerting him/her when a tracked Mode C equipped aircraft is below or is predicted by the computer to go below a predetermined minimum safe altitude.

Minimum Safe Altitudes (MSA)

MSAs are published for emergency use on IAP charts. For conventional navigation systems, the MSA is normally based on the primary omnidirectional facility on which the IAP is predicated. For RNAV approaches, the MSA is based on the runway waypoint (RWY WP) for straight in approaches, or the airport waypoint (APT WP) for circling approaches. For GPS approaches, the MSA center will be the Missed Approach Waypoint (MAWP).

Minimum Sector Altitudes

Altitudes depicted on approach charts which provide at least 1,000 feet of obstacle clearance within a 25-mile radius of the navigation facility upon which the procedure is predicated. Sectors depicted on approach charts must be at least 90 degrees in scope. These altitudes are for emergency use only and do not necessarily assure acceptable navigational signal coverage.

Minimum Vectoring Altitude (MVA)

The lowest MSL altitude at which an IFR aircraft will be vectored by a radar controller, except as otherwise authorized for radar approaches, departures, and missed approaches. The altitude meets IFR obstacle clearance criteria. It may be lower than the published MEA along an airway or J-route segment. It may be utilized for radar vectoring only upon the controller’s determination that an adequate radar return is being received from the aircraft being controlled. Charts depicting minimum vectoring altitudes are normally available only to the controllers and not to pilots.

Minimums

Weather condition requirements established for a particular operation or type of operation; e.g., IFR takeoff or landing, alternate airport for IFR flight plans, VFR flight, etc.

Minimums section

The area on an IAP chart that displays the lowest altitude and visibility requirements for the approach.

MINIT

Minutes in Trail. A specified interval between aircraft expressed in time.

Minor alteration

An alteration other than a major alteration.

Minor repair

A repair other than a major repair.

Minutes-In-Trail

A specified interval between aircraft expressed in time. This method would more likely be utilized regardless of altitude.

MIRL

Medium Intensity Runway Lights

Missed Approach

A. A maneuver conducted by a pilot when an instrument approach cannot be completed to a landing. The route of flight and altitude are shown on instrument approach procedure charts. A pilot executing a missed approach prior to the Missed Approach Point (MAP) must continue along the final approach to the MAP.
B. A term used by the pilot to inform ATC that he/she is executing the missed approach.
C. At locations where ATC radar service is provided, the pilot should conform to radar vectors when provided by ATC in lieu of the published missed approach procedure.

Missed Approach

The segment between the missed approach point or the point of arrival at decision height and the missed approach fix at the prescribed altitude.

Missed Approach Holding Waypoint (MAHWP)

An approach waypoint sequenced during the holding portion of the missed approach procedure that is usually a fly-over waypoint, rather than a fly-by waypoint.

Missed approach point (MAP)

A point prescribed in each instrument approach at which a missed approach procedure shall be executed if the required visual reference has not been established.

Mist

A popular expression for drizzle or heavy fog.

MIT

Miles-In-Trail

Mixed ice

A mixture of clear ice and rime ice.

Mixed Ice.

Simultaneous appearance of rime and clear ice or an ice formation that has the characteristics of both rime and clear ice.

Mixing ratio

The ratio by weight of the amount of water vapor in a volume of air to the amount of dry air; usually expressed as grams per kilogram (g/kg).

Mixture

The ratio of fuel to air entering the engine’s cylinders.

MLS

Microwave Landing System.

MLS Categories

A. MLS Category I. An MLS approach procedure which provides for an approach to a height above touchdown of not less than 200 feet and a runway visual range of not less than 1,800 feet.
B. MLS Category II. Undefined until data gathering/analysis completion.
C. MLS Category III. Undefined until data gathering/analysis completion.

MM

Middle Marker.

MMO

Maximum operating speed expressed in terms of a decimal of mach speed.

MNPS

Minimum Navigation Performance Specifications

MOA

Military Operations Area.

MOA

Military Operations Area

MOCA

Minimum Obstruction Clearance Altitude.

Mock-up

A three-dimensional working model used in which the actual object is either unavailable or too expensive to use. Mock-ups may emphasize some elements while eliminating nonessential elements.

Mode

The letter or number assigned to a specific pulse spacing of radio signals transmitted or received by ground interrogator or airborne transponder components of the Air Traffic Control Radar Beacon System (ATCRBS). Mode A (military Mode 3) and Mode C (altitude reporting) are used in air traffic control.

Mode C

Altitude Reporting Transponder Mode.

Mode C

Altitude reporting transponder mode.

Model

A copy of a real object which can be life-size, smaller, or larger than the original.

Moderate Icing

The rate of accumulation is such that even short encounters become potentially hazardous and use of deicing/anti-icing equipment or flight diversion is necessary.

Moderate Icing

The rate of ice accumulation requires frequent cycling of manual deicing systems1 to minimize ice accretions on the airframe. The rate of accumulation is such that anything more than a short encounter is potentially hazardous. A representative accretion rate for reference purposes is 1 to 3 inches (2.5 to 7.5 cm) per hour4 on the outer wing.5

Modified T

An RNAV approach design for single or multiple runways where terrain or operational constraints do not allow for the standard T. The “T” may be modified by increasing or decreasing the angle from the corner IAF(s) to the IF or by eliminating one or both corner IAFs.

Moist-adiabatic lapse rate

Saturated-adiabatic lapse rate—The rate of decrease of temperature with height as saturated air is lifted with no gain or loss of heat from outside sources; varies with temperature, being greatest at low temperatures.

Moisture

An all-inclusive term denoting water in any or all of its three states.

Moment

The product of the weight of an item multiplied by its arm. Moments are expressed in pound-inches (lb-in). Total moment is the weight of the airplane multiplied by the distance between the datum and the CG.

Moment Arm

The distance from a datum to the applied force.

Moment Index

The moment (weight times arm) divided by a reduction factor such as 100 or 1,000 to make the number smaller and reduce the chance of mathematical errors in computing the center of gravity.

Moment Limits vs Weight Envelope

An enclosed area on a graph of three parameters. The diagonal line representing the moment/100 crosses the horizontal line representing the weight at the vertical line representing the CG location in inches aft of the datum. When the lines cross inside the envelope, the aircraft is loaded within its weight and CG limits.

Monitor

(When used with communication transfer) listen on a specific frequency and stand by for instructions. Under normal circumstances do not establish communications.

Monocoque

A shell-like fuselage design in which the stressed outer skin is used to support the majority of imposed stresses. Monocoque fuselage design may include bulkheads but not stringers.

Monoplanes

Airplanes with a single set of wings.

Monsoon

A wind that in summer blows from sea to a continental interior, bringing copious rain, and in winter blows from the interior to the sea, resulting in sustained dry weather.

MORA

Minimum Off Route Altitude

Motivation

A need or desire that causes a person to act. Motivation can be positive or negative, tangible or intangible, subtle or obvious.

Mountain wave

A standing wave or lee wave to the lee of a mountain barrier.

Movable Slat

A movable auxiliary airfoil on the leading edge of a wing. It is closed in normal flight but extends at high angles of attack. This allows air to continue flowing over the top of the wing and delays airflow separation.

Movement Area

The runways, taxiways, and other areas of an airport/heliport which are utilized for taxiing/hover taxiing, air taxiing, takeoff, and landing of aircraft, exclusive of loading ramps and parking areas. At those airports/heliports with a tower, specific approval for entry onto the movement area must be obtained from ATC.

Moving Target Indicator

A digital moving target indicator (MTI) radar system for rejection of low velocity "clutter" by utilizing techniques to identify those radar echo returns from targets having radial velocities lower than fixed predetermined values.

MRA

Minimum Reception Altitude

MRB

Magnetic Reference Bearing

MSA

Minimum Safe Altitude.

MSL

Mean Sea Level.

MSL

Mean Sea Level.

MSL Altitude

Altitude expressed in feet measured from mean sea level.

MTA

Minimum Turning Altitude

MTI

Moving Target Indicator

MTOS

Mountain Obscuration

MTR

Military Training Route.

MTR

Military Training Route

Multi-function display (MFD)

Small screen (CRT or LCD) in an aircraft that can be used to display information to the pilot in numerous configurable ways. Often an MFD will be used in concert with a Primary Flight Display.

Multicom

A mobile service not open to public correspondence used to provide communications essential to conduct the activities being performed by or directed from private aircraft.

Multiple Runways

The utilization of a dedicated arrival runway(s) for departures and a dedicated departure runway(s) for arrivals when feasible to reduce delays and enhance capacity.

Mushing

A flight condition caused by slow speed where the control surfaces are marginally effective.

MVA

Minimum Vectoring Altitude.

MWA

Mountain Wave Activity

MWO

Meteorological Watch Office

N1

Rotational speed of the low pressure compressor in a turbine engine.

N1,N2,N3

Spool speed expressed in percent rpm. N1 on a turboprop is the gas producer speed. N1 on a turbofan or turbojet engine is the fan speed or low pressure spool speed. N2 is the high pressure spool speed on engine with 2 spools and medium pressure spool on engines with 3 spools with N3 being the high pressure spool.

N2

Rotational speed of the high pressure compressor in a turbine engine.

NA

Not Authorized

Nacelle

A streamlined enclosure on an aircraft in which an engine is mounted. On multiengine propeller-driven airplanes, the nacelle is normally mounted on the leading edge of the wing.

NACG

National Aeronautical Charting Group. (obsolete)

NACG

National Aeronautical Charting Group. (obsolete)

NACO

National Aeronautical Charting Office

NACO

National Aeronautical Charting Office

NAS

National Airspace System.

NAS

National Airspace System. The common network of U.S. airspace; air navigation facilities, equipment and services, airports or landing areas.

NASA

National Aeronautics and Space Administration

NASA

National Aeronautics and Space Administration

NASSI

National Airspace System Status Information

NATCA

National Air Traffic Controllers Association

National Aeronautical Charting Group (NACG)

A Federal agency operating under the FAA, responsible for publishing charts such as the terminal procedures and en route charts. Moved to Aeronautical Information Services AJV-A

National Aeronautical Charting Group (NACG)

A Federal agency operating under the FAA, responsible for publishing charts such as the terminal procedures and en route charts. Moved to Aeronautical Information Services AJV-A

National Airspace System

The common network of U.S. airspace; air navigation facilities, equipment and services, airports or landing areas; aeronautical charts, information and services; rules, regulations and procedures, technical information, and manpower and material. Included are system components shared jointly with the military.

National Airspace System (NAS)

Consists of a complex collection of facilities, systems, equipment, procedures, and airports operated by thousands of people to provide a safe and efficient flying environment.

National Airspace System (NAS)

The common network of United States airspace—air navigation facilities, equipment and services, airports or landing areas; aeronautical charts, information and services; rules, regulations and procedures, technical information; and manpower and material.

National defense airspace

Airspace established by a regulation prescribed, or an order issued under, 49 U.S.C. 40103(b)(3).

National Flight Data Center

A facility in Washington D.C., established by FAA to operate a central aeronautical information service for the collection, validation, and dissemination of aeronautical data in support of the activities of government, industry, and the aviation community. The information is published in the National Flight Data Digest.

National Flight Data Digest

A daily (except weekends and Federal holidays) publication of flight information appropriate to aeronautical charts, aeronautical publications, Notices to Airmen, or other media serving the purpose of providing operational flight data essential to safe and efficient aircraft operations.

National Route Program (NRP)

A set of rules and procedures designed to increase the flexibility of user flight planning within published guidelines.

National Route Program (NRP)

A set of rules and procedures designed to increase the flexibility of user flight planning within published guidelines.

National Security Area (NSA)

Areas consisting of airspace of defined vertical and lateral dimensions established at locations where there is a requirement for increased security and safety of ground facilities. Pilots are requested to voluntarily avoid flying through the depicted NSA. When it is necessary to provide a greater level of security and safety, flight in NSAs may be temporarily prohibited. Regulatory prohibitions are disseminated via NOTAMs.

National Security Area (NSA)

National Transportation Safety Board (NTSB)

A United States Government independent organization responsible for investigations of accidents involving aviation, highways, waterways, pipelines, and railroads in the United States. NTSB is charged by congress to investigate every civil aviation accident in the United States.

National Transportation Safety Board (NTSB)

Nautical twilight

The period of time before sunrise and after sunset when the sun is not more than 12° below the horizon.

NAV/COM

Navigation and Communication Radio.

NAV/COM

Navigation and communication radio.

NAVAID

Navigational Aid.

NAVAID

Navigational Aid. Any visual or electronic device, airborne or on the surface, which provides point-to-point guidance information or position data to aircraft in flight.

Navaid Classes

VOR, VORTAC, and TACAN aids are classed according to their operational use. The three classes of NAVAIDs are: a. T-Terminal. b. L-Low altitude. c. H-High altitude. Note: The normal service range for T, L, and H class aids is found in the AIM. Certain operational requirements make it necessary to use some of these aids at greater service ranges than specified. Extended range is made possible through flight inspection determinations. Some aids also have lesser service range due to location, terrain, frequency protection, etc. Restrictions to service range are listed in Airport/Facility Directory.

Navigable Airspace

Airspace at and above the minimum flight altitudes prescribed in the CFRs including airspace needed for safe takeoff and landing.

Navigation Reference System (NRS)

The NRS is a system of waypoints developed for use within the United States for flight planning and navigation without reference to ground based navigational aids. The NRS waypoints are located in a grid pattern along defined latitude and longitude lines. The initial use of the NRS will be in the high altitude environment in conjunction with the High Altitude Redesign initiative. The NRS waypoints are intended for use by aircraft capable of point-to-point navigation.

Navigational Aid

Any visual or electronic device airborne or on the surface which provides point-to-point guidance information or position data to aircraft in flight.

Navigational Gap

A navigational course guidance gap, referred to as an MEA gap, describes a distance along an airway or route segment where a gap in navigational signal coverage exists. The navigational gap may not exceed a specific distance that varies directly with altitude.

NCWF

National Convective Weather Forecast

NDB

Nondirectional Radio Beacon.

NDB

Nondirectional Radio Beacon

NDB (ADF)

Nondirectional Beacon (Automatic Direction Finder).

Negative

“No,” or “permission not granted,” or “that is not correct.”

Negative Contact

Used by pilots to inform ATC that: a. Previously issued traffic is not in sight. It may be followed by the pilot’s request for the controller to provide assistance in avoiding the traffic. b. They were unable to contact ATC on a particular frequency.

Negative Static Stability

The initial tendency of an aircraft to continue away from the original state of equilibrium after being disturbed.

Negative Torque Sensing (NTS)

A system in a turboprop engine that prevents the engine from being driven by the propeller. The NTS increases the blade angle when the propellers try to drive the engine.

Negative vorticity

Vorticity caused by anticyclonic turning; it is associated with downward motion of the air.

Net Weight

The weight of the aircraft less the weight of any chocks or other devices used to hold the aircraft on the scales.

Neutral Static Stability

The initial tendency of an aircraft to remain in a new condition after its equilibrium has been disturbed.

NEXRAD

Next Generation Weather Radar

NFDC

National Flight Data Center

NFDC

National Flight Data Center

NFPO

National Flight Procedures Office

NGA

National Geospatial Intelligence Agency

NGA

National Geospatial-Intelligence Agency

Nickel-Cadmium Battery (NiCad)

A battery made up of alkaline secondary cells. The positive plates are nickel hydroxide, the negative plates are cadmium hydroxide, and potassium hydroxide is used as the electrolyte.

Night

The time between the end of evening civil twilight and the beginning of morning civil twilight, as published in the American Air Almanac, converted to local time.

NIMA

National Imagery and Mapping Agency

Nimbostratus

A principal cloud type, gray colored, often dark, the appearance of which is rendered diffuse by more or less continuously falling rain or snow, which in most cases reaches the ground. It is thick enough throughout to blot out the sun.

NM

Nautical Mile.

NM

Nautical Mile. International unit equal to 6076.115 feet (1852 meters).

No Gyro Approach

A radar approach/vector provided in case of a malfunctioning gyro-compass or directional gyro. Instead of providing the pilot with headings to be flown, the controller observes the radar track and issues control instructions “turn right/left” or “stop turn” as appropriate.

No Gyro Vector

No Gyro Approach. A radar approach/vector provided in case of a malfunctioning gyro-compass or directional gyro. Instead of providing the pilot with headings to be flown, the controller observes the radar track and issues control instructions “turn right/left” or “stop turn” as appropriate.

No procedure turn (NoPT)

Term used with the appropriate course and altitude to denote that the procedure turn is not required.

No Transgression Zone (NTZ)

The NTZ is a 2,000 foot wide zone, located equidistant between parallel runway final approach courses in which flight is not allowed.

No-gyro approach

A radar approach that may be used in case of a malfunctioning gyro-compass or directional gyro. Instead of providing the pilot with headings to be flown, the controller observes the radar track and issues control instructions turn right/left or stop turn, as appropriate.

NOAA

National Oceanic and Atmospheric Administration.

NOAA

National Oceanic and Atmospheric Administration

Noctilucent clouds

Clouds of unknown composition which occur at great heights, probably around 75 to 90 kilometers. They resemble thin cirrus, but usually with a bluish or silverish color, although sometimes orange to red, standing out against a dark night sky. Rarely observed.

Non-RNAV DP

A DP whose ground track is based on ground-based NAVAIDS and/or dead reckoning navigation.

Nonapproach Control Tower

Authorizes aircraft to land or takeoff at the airport controlled by the tower or to transit the Class D airspace. The primary function of a nonapproach control tower is the sequencing of aircraft in the traffic pattern and on the landing area. Nonapproach control towers also separate aircraft operating under instrument flight rules clearances from approach controls and centers. They provide ground control services to aircraft, vehicles, personnel, and equipment on the airport movement area.

Nondirectional Radio Beacon (NDB)

An L/MF or UHF radio beacon transmitting nondirectional signals whereby the pilot of an aircraft equipped with direction finding equipment can determine bearing to or from the radio beacon and home on or track to or from the station. When the radio beacon is installed in conjunction with the ILS marker, it is normally called a compass locator.

Nonmovement Areas

Taxiways and apron (ramp) areas not under the control of air traffic.

Nonprecision approach

A standard instrument approach procedure in which only horizontal guidance is provided.

Nonprecision Approach Procedure

A standard instrument approach procedure in which no electronic glideslope is provided; e.g., VOR, TACAN, NDB, LOC, ASR, LDA, or SDF approaches.

Nonprecision Approach Runway

An instrument runway served by visual aids and a nonvisual aid providing at least directional guidance adequate for a straight-in approach.

Nonradar Approach

Used to describe instrument approaches for which course guidance on final approach is not provided by ground-based precision or surveillance radar. Radar vectors to the final approach course may or may not be provided by ATC. Examples of nonradar approaches are VOR, NDB, TACAN, and ILS/MLS approaches.

Nonradar Approach Control

An ATC facility providing approach control service without the use of radar.

Nonradar Arrival

An aircraft arriving at an airport without radar service or at an airport served by a radar facility and radar contact has not been established or has been terminated due to a lack of radar service to the airport.

Nonradar Route

A flight path or route over which the pilot is performing his/her own navigation. The pilot may be receiving radar separation, radar monitoring, or other ATC services while on a nonradar route.

Nonradar Separation

The spacing of aircraft in accordance with established minima without the use of radar; e.g., vertical, lateral, or longitudinal separation.

NoPT

No Procedure Turn.

NORDO

(No Radio) Aircraft That Cannot Or Do Not Communicate By Radio When Radio Communication Is Required Are Referred To As “Nordo.

Norm-referenced testing

System of testing in which students are ranked against the performance of other students.

Normal

In meteorology, the value of an element averaged for a given location over a period of years and recognized as a standard.

Normal Category

An airplane that has a seating configuration, excluding pilot seats, of nine or less, a maximum certificated takeoff weight of 12,500 pounds or less, and intended for non-acrobatic operation.

Normal Category

A category of aircraft certificated under 14 CFR part 23 and CAR part 3 that allows the maximum weight and CG range while restricting the maneuvers that are permitted.

Normal Operating Zone (NOZ)

The NOZ is the operating zone within which aircraft flight remains during normal independent simultaneous parallel ILS approaches.

Normal refraction

Refraction of the radar beam under normal atmospheric conditions; normal radius of curvature of the beam is about 4 times the radius of curvature of the Earth.

Normalizing (Turbonormalizing)

A turbocharger that maintains sea level pressure in the induction manifold at altitude.

NOTAM

Notice To Airmen

NOTAM

Notice to Airmen. A notice containing information (not known sufficiently in advance to publicize by other means) concerning the establishment, condition, or change in any component (facility, service, or procedure of, or hazard in the National Airspace System) the timely knowledge of which is essential to personnel concerned with flight operations.

NOTAM D

Distant Notam

NOTAM L

Local Notam

Notice To Airmen

A notice containing information (not known sufficiently in advance to publicize by other means) concerning the establishment, condition, or change in any component (facility, service, or procedure of, or hazard in the National Airspace System) the timely knowledge of which is essential to personnel concerned with flight operations. There are two types: NOTAM(D) and FDC NOTAM.

Notice to Airmen (NOTAM)

A notice filed with an aviation authority to alert aircraft pilots of any hazards en route or at a specific location. The authority in turn provides means of disseminating relevant NOTAMs to pilots.

Notices To Airmen Publication

A publication issued every 28 days, designed primarily for the pilot, which contains current NOTAM information considered essential to the safety of flight as well as supplemental data to other aeronautical publications. The contraction NTAP is used in NOTAM text.

NPA

Nonprecision Approach

NPRM

Notice of Proposed Rulemaking

NRP

National Route Program.

NRP

North American Route Program. The NRP is a set of rules and procedures which are designed to increase the flexibility of user flight planning within published guidelines.

NRR

Non-Restrictive Routing

NSA

National Security Area.

NSA

National Security Area

NSW

No Significant Weather

NTAP

Notice To Airmen Publication

NTAP

Notices to Airmen Publication

NTSB

National Transportation Safety Board.

NTSB

National Transportation Safety Board

NTZ

No Transgression Zone

NTZ

No Transgression Zone

Numerical forecasting

Forecasting by digital computers solving mathematical equations; used extensively in weather services throughout the world.

Numerical weather prediction

Forecasting by digital computers solving mathematical equations; used extensively in weather services throughout the world.

Numerous Targets Vicinity (Location)

A traffic advisory issued by ATC to advise pilots that targets on the radar scope are too numerous to issue individually.

NWS

National Weather Service.

NWS

National Weather Service

NWS

National Weather Service.

OAT

Outside Air Temperature

Objectivity

The singleness of scoring of a test; it does not reflect the biases of the person grading the test.

OBS

Omni-bearing Selector

Obscuration

Denotes sky hidden by surface-based. obscuring phenomena and vertical visibility restricted overhead.

Obscuring phenomena

Any hydrometeor or lithometeor other than clouds; may be surface based or aloft.

Obstacle

An existing object, object of natural growth, or terrain at a fixed geographical location or which may be expected at a fixed location within a prescribed area with reference to which vertical clearance is or must be provided during flight operation.

Obstacle Clearance Surface (OCS)

An inclined or level surface associated with a defined area for obstruction evaluation.

Obstacle departure procedures (ODP)

A preplanned instrument flight rule (IFR) departure procedure printed for pilot use in textual or graphic form to provide obstruction clearance via the least onerous route from the terminal area to the appropriate en route structure. ODPs are recommended for obstruction clearance and may be flown without ATC clearance unless an alternate departure procedure (SID or radar vector) has been specifically assigned by ATC.

Obstacle Free Zone

The OFZ is a three dimensional volume of airspace which protects for the transition of aircraft to and from the runway. The OFZ clearing standard precludes taxiing and parked airplanes and object penetrations, except for frangible NAVAID locations that are fixed by function. Additionally, vehicles, equipment, and personnel may be authorized by air traffic control to enter the area using the provisions of FAAO JO 7110.65, Para 3-1-5, VEHICLES/EQUIPMENT/PERSONNEL ON RUNWAYS. The runway OFZ and when applicable, the inner-approach OFZ, and the inner-transitional OFZ, comprise the OFZ.

Obstacle Identification Surface (OIS)

The design of a departure procedure is based on TERPS, a living document that is updated frequently. Departure design criteria assumes an initial climb of 200 feet per NM after crossing the departure end of the runway (DER) at a height of at least 35 feet above the ground. Assuming a 200 feet per NM climb, the departure is structured to provide at least 48 feet per NM of clearance above objects that do not penetrate the obstacle slope. The slope, known as the obstacle identification slope (OIS), is based on a 40 to 1 ratio, which is the equivalent of a 152-foot per NM slope.

Obstruction

Any object/obstacle exceeding the obstruction standards specified by 14 CFR Part 77, Subpart C.

Obstruction lights

Lights that can be found both on and off an airport to identify obstructions.

Occluded front

A frontal occlusion occurs when a fast-moving cold front catches up with a slow moving warm front. The difference in temperature within each frontal system is a major factor in determining whether a cold or warm front occlusion occurs.

Occluded Front

The front formed by a cold front overtaking a warm front and lifting the warm air above the Earth’s surface. An occlusion (or frontal occlusion) forms when an air mass is trapped between two colder air masses and is forced to higher and higher levels.

Occlusion

Same as occluded front—a composite of two fronts as a cold front overtakes a warm front or quasi-stationary front. (commonly called occlusion or frontal occlusion).

OCS

Obstacle Clearance Surface

Octane

The rating system of aviation gasoline with regard to its anti-detonating qualities.

ODALS

Omnidirectional Approach Lighting System Consists of seven omnidirectional flashing lights located in the approach area of a nonprecision runway. Five lights are located on the runway centerline extended with the first light located 300 feet from the threshold and extending at equal intervals up to 1,500 feet from the threshold. The other two lights are located, one on each side of the runway threshold, at a lateral distance of 40 feet from the runway edge, or 75 feet from the runway edge when installed on a runway equipped with a VASI.

ODP

Obstacle Departure Procedures.

OEI

One Engine Inoperative.

Off Course

A term used to describe a situation where an aircraft has reported a position fix or is observed on radar at a point not on the ATC-approved route of flight.

Off-Airway Routes

The FAA prescribes altitudes governing the operation of aircraft under IFR for off airway routes in a similar manner to those on federal airways, jet routes, area navigation low or high altitude routes, and other direct routes for which an MEA is designated.

Off-Route Obstruction Clearance Altitude (OROCA)

An off-route altitude that provides obstruction clearance with a 1,000 foot buffer in non-mountainous terrain areas and a 2,000 foot buffer in designated mountainous areas within the U.S. This altitude may not provide signal coverage from ground based navigational aids, air traffic control radar, or communications coverage.

Off-Route Vector

A vector by ATC which takes an aircraft off a previously assigned route. Altitudes assigned by ATC during such vectors provide required obstacle clearance.

Offset Parallel Runways

Staggered runways having centerlines which are parallel.

OM

Outer Marker.

Omission error

The failure to anticipate significant instrument indications following attitude changes; for example, concentrating on pitch control while forgetting about heading or roll information, resulting in erratic control of heading and bank.

Omission error

On Course

A. Used to indicate that an aircraft is established on the route centerline.
B. Used by ATC to advise a pilot making a radar approach that his/her aircraft is lined up on the final approach course.

On-Course Indication

An indication on an instrument, which provides the pilot a visual means of determining that the aircraft is located on the centerline of a given navigational track, or an indication on a radar scope that an aircraft is on a given track.

One-Minute Weather

The most recent one minute updated weather broadcast received by a pilot from an uncontrolled airport ASOS/AWSS/AWOS.

One-Minute Weather

The most recent 1-minute update weather broadcast based on ASOS/AWOS measurements and available to a pilot from an uncontrolled airport ASOS/AWOS.

Operate

With respect to aircraft, use, cause to use or authorize to use aircraft, for the purpose (except as provided in §91.13 of this chapter) of air navigation including the piloting of aircraft, with or without the right of legal control (as owner, lessee, or otherwise).

Operational control

With respect to a flight, the exercise of authority over initiating, conducting or terminating a flight.

Operations Specifications (OpsSpecs)

A published document providing the conditions under which an air carrier and operator for compensation or hire must operate in order to retain approval from the FAA.

Opposite Direction Aircraft

Aircraft are operating in opposite directions when: a. They are following the same track in reciprocal directions; or b. Their tracks are parallel and the aircraft are flying in reciprocal directions; or c. Their tracks intersect at an angle of more than 135°.

OpsSpecs

Operations Specifications

Optical illusion

A misleading visual image. For the purpose of this handbook, the term refers to the brains misinterpretation of features on the ground associated with landing, which causes a pilot to misread the spatial relationships between the aircraft and the runway.

Optical illusion

A misleading visual image. For the purpose of this handbook, the term refers to the brain’s misinterpretation of features on the ground associated with landing, which causes a pilot to misread the spatial relationships between the aircraft and the runway.

Option Approach

An approach requested and conducted by a pilot which will result in either a touch-and-go, missed approach, low approach, stop-and-go, or full stop landing.

Orientation

Awareness of the position of the aircraft and of oneself in relation to a specific reference point.

Orientation

Awareness of the position of the aircraft and of oneself in relation to a specific reference point.

OROCA

An off-route altitude which provides obstruction clearance with a 1,000 foot buffer in nonmountainous terrain areas and a 2,000 foot buffer in designated mountainous areas within the United States. This altitude may not provide signal coverage from ground-based navigational aids, air traffic control radar, or communications coverage.

Orographic

Of, pertaining to, or caused by mountains as in orographic clouds, orographic lift, or orographic precipitation.

Orographic Cloud

A cloud that usually results from air flowing upslope from terrain and being cooled adiabatically.

Otolith organ

An inner ear organ that detects linear acceleration and gravity orientation.

Otolith organ

An inner ear organ that detects linear acceleration and gravity orientation.

OTS

Out of service

Out

The conversation is ended and no response is expected.

Outer Area (Associated With Class C Airspace)

Nonregulatory airspace surrounding designated Class C airspace airports wherein ATC provides radar vectoring and sequencing on a full-time basis for all IFR and participating VFR aircraft. The service provided in the outer area is called Class C service which includes: IFR/IFR-standard IFR separation; IFR/VFR-traffic advisories and conflict resolution; and VFR/VFR-traffic advisories and, as appropriate, safety alerts. The normal radius will be 20 nautical miles with some variations based on site-specific requirements. The outer area extends outward from the primary Class C airspace airport and extends from the lower limits of radar/radio coverage up to the ceiling of the approach control’s delegated airspace excluding the Class C charted area and other airspace as appropriate.

Outer Compass Locator (LOM)

A compass locator installed at the site of the outer marker of an instrument landing system.

Outer Fix

A general term used within ATC to describe fixes in the terminal area, other than the final approach fix. Aircraft are normally cleared to these fixes by an Air Route Traffic Control Center or an Approach Control Facility. Aircraft are normally cleared from these fixes to the final approach fix or final approach course.

Outer Marker

A marker beacon at or near the glideslope intercept altitude of an ILS approach. It is keyed to transmit two dashes per second on a 400 Hz tone, which is received aurally and visually by compatible airborne equipment. The OM is normally located four to seven miles from the runway threshold on the extended centerline of the runway.

Outside air temperature (OAT)

The measured or indicated air temperature (IAT) corrected for compression and friction heating. Also referred to as true air temperature.

Outside Air Temperature (OAT)

The measured or indicated air temperature outside the aircraft that is uncorrected.

Over

My transmission is ended; I expect a response.

Over-the-top

Above the layer of clouds or other obscuring phenomena forming the ceiling.

Overboost

A condition in which a reciprocating engine has exceeded the maximum manifold pressure allowed by the manufacturer. Can cause damage to engine components.

Overcontrolling

Using more movement in the control column than is necessary to achieve the desired pitch-and bank condition.

Overcontrolling

Using more movement in the control column than is necessary to achieve the desired pitch-and-bank condition.

Overhead question

In the guided discussion method, a question directed to the entire group in order to stimulate thought and discussion from the entire group. An overhead question may be used by an instructor as the lead-off question.

Overpower

To use more power than required for the purpose of achieving a faster rate of airspeed change.

Overpower

To use more power than required for the purpose of achieving a faster rate of airspeed change.

Overseas air commerce

The carriage by aircraft of persons or property for compensation or hire, or the carriage of mail by aircraft, or the operation or navigation of aircraft in the conduct or furtherance of a business or vocation, in commerce between a place in any State of the United States, or the District of Columbia, and any place in a territory or possession of the United States; or between a place in a territory or possession of the United States, and a place in any other territory or possession of the United States.

Overseas air transportation

The carriage by aircraft of persons or property as a common carrier for compensation or hire, or the carriage of mail by aircraft, in commerce:
(1) Between a place in a State or the District of Columbia and a place in a possession of the United States; or
(2) Between a place in a possession of the United States and a place in another possession of the United States; whether that commerce moves wholly by aircraft or partly by aircraft and partly by other forms of transportation.

Overspeed

A condition in which an engine has produced more r.p.m. than the manufacturer recommends, or a condition in which the actual engine speed is higher than the desired engine speed as set on the propeller control.

Overtemp

A condition in which a device has reached a temperature above that approved by the manufacturer or any exhaust temperature that exceeds the maximum allowable for a given operating condition or time limit. Can cause internal damage to an engine.

Overtorque

A condition in which an engine has produced more torque (power) than the manufacturer recommends, or a condition in a turboprop or turboshaft engine where the engine power has exceeded the maximum allowable for a given operating condition or time limit. Can cause internal damage to an engine.

Ozone

An unstable form of oxygen; heaviest concentrations are in the stratosphere; corrosive to some metals; absorbs most ultraviolet solar radiation.

P Time

Proposed Departure Time.

P-Factor

A tendency for an aircraft to yaw to the left due to the for descending propeller blade on the right producing more thrust than the ascending blade on the left. This occurs when the aircraft’s longitudinal axis is in a climbing attitude in relation to the relative wind. The P-factor would be to the right if the aircraft had a counterclockwise rotating propeller.

P-factor

A tendency for an aircraft to yaw to the left due to the descending propeller blade on the right producing more thrust than the ascending blade on the left. This occurs when the aircraft’s longitudinal axis is in a climbing attitude in relation to the relative wind. The P-factor would be to the right if the aircraft had a counterclockwise rotating propeller.

P-static

Precipitation Static.

P-static

Precipitation Static.

P/CG

Pilot/Controller Glossary

PA

Precision Approach

Pan-Pan

The international radio-telephony urgency signal. When repeated three times, indicates uncertainty or alert followed by the nature of the urgency.

PAPI

Precision Approach Path Indicator.

PAPI

Precision Approach Path Indicator

PAR

Precision Approach Radar.

Parachute

A device used or intended to be used to retard the fall of a body or object through the air.

Parallel ILS Approaches

Approaches to parallel runways by IFR aircraft which, when established inbound toward the airport on the adjacent final approach courses, are radar-separated by at least 2 miles.

Parallel MLS Approaches

Approaches to parallel runways by IFR aircraft which, when established inbound toward the airport on the adjacent final approach courses, are radar-separated by at least 2 miles.

Parallel Offset Route

A parallel track to the left or right of the designated or established airway/route. Normally associated with Area Navigation (RNAV) operations.

Parallel Runways

Two or more runways at the same airport whose centerlines are parallel. In addition to runway number, parallel runways are designated as L (left) and R (right) or, if three parallel runways exist, L (left), C (center), and R (right).

Parallels

Lines of latitude.

Parasite Drag

That part of total drag created by the design or shape of airplane parts. Parasite drag increases with an increase in airspeed.

Parasite drag

Drag caused by the friction of air moving over the aircraft structure; its amount varies directly with the airspeed.

Parasite drag

Drag caused by the friction of air moving over the aircraft structure; its amount varies directly with the airspeed.

Parcel

A small volume of air, small enough to contain uniform distribution of its meteorological properties, and large enough to remain relatively self-contained and respond to all meteorological processes. No specific dimensions have been defined, however, the order of magnitude of 1 cubic foot has been suggested.

Partial obscuration

A designation of sky cover when part of the sky is hidden by surface based obscuring phenomena.

PAX

Passengers.

Payload

(GAMA) Weight of occupants, cargo, and baggage.

Payload (GAMA)

The weight of occupants, cargo, and baggage.

PCG

Positive Course Guidance

PDC

Pre-Departure Clearance

PDR

Preferential Departure Route

Perceptions

The basis of all learning, perceptions result when a person gives meaning to external stimuli or sensations. Meaning derived from perception is influenced by an individual’s experience and many other factors.

Performance-based objectives

A statement of purpose for a lesson or instructional period that includes three elements: a description of the skill or behavior desired of the student, a set of conditions under which the measurement will be taken, and a set of criteria describing the standard used to measure accomplishment of the objective.

Permanent Ballast (fixed ballast)

A weight permanently installed in an aircraft to bring its center of gravity into allowable limits. Permanent ballast is part of the aircraft empty weight.

Permanent Echo

Radar signals reflected from fixed objects on the earth’s surface; e.g., buildings, towers, terrain. Permanent echoes are distinguished from “ground clutter” by being definable locations rather than large areas. Under certain conditions they may be used to check radar alignment.

Person

An individual, firm, partnership, corporation, company, association, joint-stock association, or governmental entity. It includes a trustee, receiver, assignee, or similar representative of any of them.

Personal computer-based aviation training device (PCATD)

A device which uses software which can be displayed on a personal computer to replicate the instrument panel of an airplane. A PCATD must replicate a type of airplane or family of airplanes and meet the virtual control requirements specified in AC 61-126.

Personality

The embodiment of personal traits and characteristics of an individual that are set at a very early age and are extremely resistant to change.

Personality

The embodiment of personal traits and characteristics of an individual that are set at a very early age and extremely resistant to change.

PF

Pilot Flying

PFAST

Passive Final Approach Spacing Tool

PFD

Primary Flight Display.

PFD

Primary Flight Display

PFD

Personal Flotation Device

Phugoid oscillations

Long-period oscillations of an aircraft around its lateral axis. It is a slow change in pitch accompanied by equally slow changes in airspeed. Angle of attack remains constant, and the pilot often corrects for phugoid oscillations without even being aware of them.

Physical organism

A perception factor that describes a person’s ability to sense the world around them.

PIC

Pilot-in-Command.

PIC

Pilot In Command.

Pilot balloon

A small free-lift balloon used to determine the speed and direction of winds in the upper air.

Pilot balloon observation (commonly called PIBAL)

A method of winds-aloft observation by visually tracking a pilot balloon.

Pilot Briefing

A service provided by the FSS to assist pilots in flight planning. Briefing items may include weather information, NOTAMs, military activities, flow control information, and other items as requested.

Pilot Briefing

A service provided by a Flight Service Station (FSS) or other FAA-approved provider that can assist pilots with flight planning. Briefing items may include weather information, Notices to Airmen (NOTAM), military activities, flow control information, and other items, as requested.

Pilot Briefing Information

The current format for charted IAPs issued by NACO. The information is presented in a logical order facilitating pilot briefing of the procedures. Charts include formatted information required for quick pilot or flight crew reference located at the top of the chart.

Pilot error

Pilot action/inaction or decision/indecision causing or contributing to an accident or incident.

Pilot in command

The person who:
(1) Has final authority and responsibility for the operation and safety of the flight;
(2) Has been designated as pilot in command before or during the flight; and
(3) Holds the appropriate category, class, and type rating, if appropriate, for the conduct of the flight.

Pilot In Command

The pilot responsible for the operation and safety of an aircraft during flight time.

Pilot report (PIREP)

Report of meteorological phenomena encountered by aircraft.

Pilot report (PIREP)

Report of meteorological phenomena encountered by aircraft.

Pilot Weather Report (PIREP)

A report from a pilot of meteorological phenomena usually transmitted in a prescribed format. The letters “UA” identify the message as a routine PIREP while the letters “UUA” identify an urgent PIREP.

Pilotage

Navigation by visual reference to landmarks.

Pilot’s Discretion

When used in conjunction with altitude assignments, means that ATC has offered the pilot the option of starting climb or descent whenever he/she wishes and conducting the climb or descent at any rate he/she wishes. He/she may temporarily level off at any intermediate altitude. However, once he/she has vacated an altitude, he/she may not return to that altitude.

Pilot’s Operating Handbook (POH)

An FAA-approved document published by the airframe manufacturer that lists the operating conditions for a particular model of aircraft and its engine(s).

Pilot’s Operating Handbook/Airplane Flight Manual (POH/AFM)

FAA-approved documents published by the airframe manufacturer that list the operating conditions for a particular model of aircraft.

Pilot’s Operating Handbook/Airplane Flight Manual (POH/AFM)

FAA-approved documents published by the airframe manufacturer that list the operating conditions for a particular model of aircraft.

PinS

Point-In-Space

PinS

Point-in-Space

PIREP

Pilot Report.

PIREP

Pilot Weather Report

PIREP

Pilot Report.

Pirep

Pilot Weather Report.

Piston Engine

A reciprocating engine.

Pitch

The rotation of an airplane about its lateral axis, or on a propeller, the blade angle as measured from plane of rotation.

Pitch Point

A fix/waypoint that serves as a transition point from a departure procedure or the low altitude ground-based navigation structure into the high altitude waypoint system.

Pitch setting

The propeller blade setting as determined by the blade angle measured in a manner, and at a radius, specified by the instruction manual for the propeller.

Pitot pressure

Ram air pressure used to measure airspeed.

Pitot pressure

Ram air pressure used to measure airspeed.

Pitot-static head

A combination pickup used to sample pitot pressure and static air pressure.

Pitot-static head

A combination pickup used to sample pitot pressure and static air pressure.

Pivotal Altitude

A specific altitude at which, when an airplane turns at a given groundspeed, a projecting of the sighting reference line to a selected point on the ground will appear to pivot on that point.

Plan position indicator (PPI) scope

A radar indicator scope displaying range and azimuth of targets in polar coordinates.

Plan view

The overhead view of an approach procedure on an instrument approach chart. The plan view depicts the routes that guide the pilot from the en route segments to the IAF.

Planform

The shape or form of a wing as viewed from above. It may be long and tapered, short and rectangular, or various other shapes.

Plow wind

The spreading downdraft of a thunderstorm; a strong, straight-line wind in advance of the storm. Also called first gust.

PM

Pilot Monitoring

PMA

Parts Manufacturer Approval.

Pneumatic

Operation by the use of compressed air.

Pneumatic Systems

The power system in an aircraft used for operating such items as landing gear, brakes, and wing flaps with compressed air as the operating fluid.

POB

Persons on Board

POFZ

Precision Obstacle Free Zone

POH

Pilots Operating Handbook

POH/AFM

Pilots Operating Handbook/Airplane Flight Manual.

POH/AFM

Pilot’s Operating Handbook/Airplane Flight Manual.

Point-in-Space (PinS)Approach

An approach normally developed to heliports that do not meet the IFR heliport design standards but meet the standards for a VFR heliport. A helicopter PinS approach can be developed using conventional NAVAIDs or RNAV systems. These procedures have either a VFR or visual segment between the MAP and the landing area. The procedure will specify a course and distance from the MAP to the heliport(s) and include a note to proceed VFR or visually from the MAP to the heliport, or conduct the missed approach.

Point-To-Point (PTP)

A level of NRR service for aircraft that is based on traditional waypoints in their FMSs or RNAV equipage.

Polar air

An air mass with characteristics developed over high latitudes, especially within the subpolar highs. Continental polar air (cP) has cold surface temperatures, low moisture content, and, especially in its source regions, has great stability in the lower layers. It is shallow in comparison with Arctic air. Maritime polar (mP) initially possesses similar properties to those of continental polar air, but in passing over warmer water it becomes unstable with a higher moisture content. Compare tropical air.

Polar front

The semipermanent, semicontinuous front separating air masses of tropical and polar origins.

Poor judgment chain

A series of mistakes that may lead to an accident or incident. Two basic principles generally associated with the creation of a poor judgment chain are: (1) one bad decision often leads to another; and (2) as a string of bad decisions grows, it reduces the number of subsequent alternatives for continued safe flight. Aeronautical decision- making is intended to break the poor judgment chain before it can cause an accident or incident.

Porpoising

Oscillating around the lateral axis of the aircraft during landing.

Position error

Error in the indication of the altimeter, ASI, and VSI caused by the air at the static system entrance not being absolutely still.

Position error

Error in the indication of the altimeter, ASI, and VSI caused by the air at the static system entrance not being absolutely still.

Position Lights

Lights on an aircraft consisting of a red light on the left wing, a green light on the right wing, and a white light on the tail. CFRs require that these lights be displayed in flight from sunset to sunrise.

Position report

A report over a known location as transmitted by an aircraft to ATC.

Position report

A report over a known location as transmitted by an aircraft to ATC.

Positive Control

The separation of all air traffic within designated airspace by air traffic control.

Positive Course Guidance (PCG)

A continuous display of navigational data that enables an aircraft to be flown along a specific course line, e.g., radar vector, RNAV, ground-based NAVAID.

Positive Static Stability

The initial tendency to return to a state of equilibrium when disturbed from that state.

Positive static stability

The initial tendency to return to a state of equilibrium when disturbed from that state.

Positive vorticity

Vorticity caused by cyclonic turning; it is associated with upward motion of the air.

Potable Water

Water carried in an aircraft for the purpose of drinking.

Power

Implies work rate or units of work per unit of time, and as such, it is a function of the speed at which the force is developed. The term “power required” is generally associated with reciprocating engines.

Power density

In radar meteorology the amount of radiated energy per unit cross sectional area in the radar beam.

Power Distribution Bus

A Bus Bar. An electrical power distribution point to which several circuits may be connected. It is often a solid metal strip having a number of terminals installed on it.

Power Lever

The cockpit lever connected to the fuel control unit scheduling fuel flow to the combustion chambers of a turbine engine.

Powered parachute

A powered aircraft comprised of a flexible or semi-rigid wing connected to a fuselage so that the wing is not in position for flight until the aircraft is in motion. The fuselage of a powered parachute contains the aircraft engine, a seat for each occupant and is attached to the aircraft’s landing gear.

Powered-lift

A heavier-than-air aircraft capable of vertical takeoff, vertical landing, and low speed flight that depends principally on engine-driven lift devices or engine thrust for lift during these flight regimes and on nonrotating airfoil(s) for lift during horizontal flight.

Powerplant

A complete engine and propeller combination with accessories.

PPS

Precise Positioning Service

Practical Slip Limit

The maximum slip an aircraft is capable of performing due to rudder travel limits.

Practical Test Standards (PTS)

An FAA published list of standards which must be met for the issuance of a particular pilot certificate or rating. FAA inspectors and designated pilot examiners use these standards when conducting pilot practical tests and flight instructors should use the PTS while preparing applicants for practical tests. (Obsolete term, replaced by Airman Certification Standards)

Practice Instrument Approach

An instrument approach procedure conducted by a VFR or an IFR aircraft for the purpose of pilot training or proficiency demonstrations.

Pre-Departure Clearance

An application with the Terminal Data Link System (TDLS) that provides clearance information to subscribers, through a service provider, in text to the cockpit or gate printer.

Pre-Flight Pilot Briefing

Pilot Briefing.

Precession

The tilting or turning of a gyro in response to deflective forces causing slow drifting and erroneous indications in gyroscopic instruments.

Precession

The characteristic of a gyroscope that causes an applied force to be felt, not at the point of application, but 90° from that point in the direction of rotation.

Precession

The characteristic of a gyroscope that causes an applied force to be felt, not at the point of application, but 90° from that point in the direction of rotation.

Precipitation

Any or all forms of water particles, whether liquid or solid, that fall from the atmosphere and reach the surface. It is a major class of hydrometeor, distinguished from cloud and virga in that it must reach the surface.

Precipitation attenuation

Reduction of power density because of absorption or reflection of energy by precipitation.

Precipitation Radar Weather Descriptions

Existing radar systems cannot detect turbulence. However, there is a direct correlation between the degree of turbulence and other weather features associated with thunderstorms and the weather radar precipitation intensity. Controllers will issue (where capable) precipitation intensity as observed by radar when using weather and radar processor (WARP) or NAS ground based digital radars with weather capabilities. When precipitation intensity information is not available, the intensity will be described as UNKNOWN. When intensity levels can be determined, they shall be described as: a. LIGHT (< 30 dBZ b. MODERATE (30 to 40 dBZ c. HEAVY (> 40 to 50 dBZ d. EXTREME (> 50 dBZ

Precipitation static (P-static)

A form of radio interference caused by rain, snow, or dust particles hitting the antenna and inducing a small radio-frequency voltage into it.

Precipitation static (P-static)

A form of radio interference caused by rain, snow, or dust particles hitting the antenna and inducing a small radio-frequency voltage into it.

Precision approach

A standard instrument approach procedure in which both vertical and horizontal guidance is provided.

Precision Approach

Precision Approach Procedure.

Precision approach path indicator (PAPI)

A system of lights similar to the VASI, but consisting of one row of lights in two- or four-light systems. A pilot on the correct glide slope will see two white lights and two red lights. See VASI.

Precision Approach Path Indicator (PAPI)

An airport lighting facility, similar to VASI, providing vertical approach slope guidance to aircraft during approach to landing. PAPIs consist of a single row of either two or four lights, normally installed on the left side of the runway, and have an effective visual range of about 5 miles during the day and up to 20 miles at night. PAPIs radiate a directional pattern of high intensity red and white focused light beams which indicate that the pilot is “on path” if the pilot sees an equal number of white lights and red lights, with white to the left of the red; “above path” if the pilot sees more white than red lights; and “below path” if the pilot sees more red than white lights.

Precision Approach Procedure

A standard instrument approach procedure in which an electronic glideslope/glidepath is provided; e.g., ILS, MLS, and PAR.

Precision Approach Radar

Radar equipment in some ATC facilities operated by the FAA and/or the military services at joint-use civil/military locations and separate military installations to detect and display azimuth, elevation, and range of aircraft on the final approach course to a runway. This equipment may be used to monitor certain nonradar approaches, but is primarily used to conduct a precision instrument approach (PAR) wherein the controller issues guidance instructions to the pilot based on the aircraft’s position in relation to the final approach course (azimuth), the glidepath (elevation), and the distance (range) from the touchdown point on the runway as displayed on the radar scope. Note: The abbreviation “PAR” is also used to denote preferential arrival routes in ARTCC computers.

Precision Approach Runway, Category I

An instrument runway served by ILS and visual aids intended for operations down to 60 m (200 feet) decision height and down to an RVR of the order of 800 m.

Precision Approach Runway, Category II

An instrument runway served by ILS and visual aids intended for operations down to 30 m (100 feet) decision height and down to an RVR of the order of 400 m.

Precision Approach Runway, Category III

An instrument runway served by ILS to and along the surface of the runway and: 1. Intended for operations down to an RVR of the order of 200 m (no decision height being applicable) using visual aids during the final phase of landing; 2. Intended for operations down to an RVR of the order of 50 m (no decision height being applicable) using visual aids for taxiing; 3. Intended for operations without reliance on visual reference for landing or taxiing. Note: Visual aids need not necessarily be matched to the scale of nonvisual aids provided. The criterion for the selection of visual aids is the conditions in which operations are intended to be conducted.

Precision Obstacle Free Zone (POFZ)

An 800 foot wide by 200 foot long area centered on the runway centerline adjacent to the threshold designed to protect aircraft flying precision approaches from ground vehicles and other aircraft when ceiling is less than 250 feet or visibility is less than 3/4 statute mile (or runway visual range below 4,000 feet.

Precision Runway Monitor (PRM)

Provides air traffic controllers with high precision secondary surveillance data for aircraft on final approach to parallel runways that have extended centerlines separated by less than 4,300 feet. High resolution color monitoring displays (FMA) are required to present surveillance track data to controllers along with detailed maps depicting approaches and a no transgression zone.

Predictive Wind Shear Alert System (PWS)

A self-contained system used onboard some aircraft to alert the flight crew to the presence of a potential wind shear. PWS systems typically monitor 3 miles ahead and 25 degrees left and right of the aircraft’s heading at or below 1200’ AGL. Departing flights may receive a wind shear alert after they start the takeoff roll and may elect to abort the takeoff. Aircraft on approach receiving an alert may elect to go around or perform a wind shear escape maneuver.

Preferential Arrival Route PAR

A specific arrival route from an appropriate en route point to an airport or terminal area. It may be included in a Standard Terminal Arrival (STAR) or a Preferred IFR Route. The abbreviation “PAR” is used primarily within the ARTCC and should not be confused with the abbreviation for Precision Approach Radar.

Preferential Departure And Arrival Route (PDAR)

A route between two terminals which are within or immediately adjacent to one ARTCC’s area. PDARs are not synonymous with Preferred IFR Routes but may be listed as such as they do accomplish essentially the same purpose.

Preferential Departure Route (PDR)

A specific departure route from an airport or terminal area to an en route point where there is no further need for flow control. It may be included in an Instrument Departure Procedure (DP) or a Preferred IFR Route.

Preferential Routes

Preferential routes (PDRs, PARs, and PDARs) are adapted in ARTCC computers to accomplish inter/intrafacility controller coordination and to assure that flight data is posted at the proper control positions. Locations having a need for these specific inbound and outbound routes normally publish such routes in local facility bulletins, and their use by pilots minimizes flight plan route amendments. When the workload or traffic situation permits, controllers normally provide radar vectors or assign requested routes to minimize circuitous routing. Preferential routes are usually confined to one ARTCC’s area and are referred to by the following names or acronyms: Preferential Departure Route (PDR), Preferential Arrival Route (PAR), and Preferential Departure and Arrival Route (PDAR).

Preferred IFR Routes

Routes established between busier airports to increase system efficiency and capacity. They normally extend through one or more ARTCC areas and are designed to achieve balanced traffic flows among high density terminals. IFR clearances are issued on the basis of these routes except when severe weather avoidance procedures or other factors dictate otherwise. Preferred IFR Routes are listed in the Airport/Facility Directory. If a flight is planned to or from an area having such routes but the departure or arrival point is not listed in the Airport/Facility Directory, pilots may use that part of a Preferred IFR Route which is appropriate for the departure or arrival point that is listed. Preferred IFR Routes are correlated with DPs and STARs and may be defined by airways, jet routes, direct routes between NAVAIDs, Waypoints, NAVAID radials/DME, or any combinations thereof.

Preignition

Ignition occurring in the cylinder before the time of normal ignition. Preignition is often caused by a local hot spot in the combustion chamber igniting the fuel/air mixture.

Preparation

The first step of the teaching process, which consists of determining the scope of the lesson, the objectives, and the goals to be attained. This portion also includes making certain all necessary supplies are on hand. When using the telling-and-doing technique of flight instruction, this step is accomplished prior to the flight lesson.

Presentation

The second step of the teaching process, which consists of delivering information or demonstrating the skills that make up the lesson. The delivery could be by either the lecture method or demonstration-performance method. In the telling-and-doing technique of flight instruction, this is the segment in which the instructor both talks about and performs the procedure.

Pressure altimeter

An aneroid barometer with a scale graduated in altitude instead of pressure using standard atmospheric pressure-height relationships; shows indicated altitude (not necessarily true altitude); may be set to measure altitude (indicated) from any arbitrarily chosen level.

Pressure Altitude

The altitude indicated when the altimeter setting window (barometric scale) is adjusted to 29.92. This is the altitude above the standard datum plane, which is a theoretical plane where air pressure (corrected to 15ºC) equals 29.92 in. Hg. Pressure altitude is used to compute density altitude, true altitude, true airspeed, and other performance data.

Pressure altitude

The altitude in the standard atmosphere at which the pressure is the same as at the point in question. Since an altimeter operates solely on pressure, this is the uncorrected altitude indicated by an altimeter set at standard sea level pressure of 29.92 inches or 1013 millibars.

Pressure demand oxygen system

A demand oxygen system that supplies 100 percent oxygen at sufficient pressure above the altitude where normal breathing is adequate. Also referred to as a pressure breathing system.

Pressure gradient

The rate of decrease of pressure per unit distance at a fixed time.

Pressure jump

A sudden, significant increase in station pressure.

Pressure tendency

Barometric tendency. The change of barometric pressure within a specified period of time. In aviation weather observation, routinely determined periodically, usually for a 3-hour period.

Pretest

A test used to determine whether a student has the necessary qualifications to begin a course of study. Also used to determine the level of knowledge a student has in relation to the material that will be presented in the course.

Prevailing easterlies

The broad current or pattern of persistent easterly winds in the Tropics and in polar regions.

Prevailing visibility

The greatest horizontal visibility equaled or exceeded throughout at least half the horizon circle (which is not necessarily continuous).

Prevailing visibility

In the U.S., the greatest horizontal visibility which is equaled or exceeded throughout half of the horizon circle; it need not be a continuous half.

Prevailing Visibility

The greatest horizontal visibility equaled or exceeded throughout at least half the horizon circle which need not necessarily be continuous.

Prevailing westerlies

The dominant west-to-east motion of the atmosphere, centered over middle latitudes of both hemispheres.

Prevailing wind

Direction from which the wind blows most frequently.

Preventive maintenance

Simple or minor preservative operations and the replacement of small standard parts not involving complex assembly operation as listed in 14 CFR part 43, appendix A. Certificated pilots may perform preventive maintenance on any aircraft that is owned or operated by them provided that the aircraft is not used in air carrier service.

Primacy

A principle of learning in which the first experience of something often creates a strong, almost unshakable impression. The importance to an instructor is that the first time something is demonstrated, it must be shown correctly since that experience is the one most likely to be remembered by the student.

Primary and supporting

A method of attitude instrument flying using the instrument that provides the most direct indication of attitude and performance.

Primary flight display (PFD)

A display that provides increased situational awareness to the pilot by replacing the traditional six instruments used for instrument flight with an easy-to-scan display that provides the horizon, airspeed, altitude, vertical speed, trend, trim, rate of turn among other key relevant indications.

Primary Radar

A radar system in which a minute portion of a radio pulse transmitted from a site is reflected by an object and then received back at that site for processing and display at an air traffic control facility.

Principal Operations Inspector (POI)

Scheduled air carriers and operators for compensation or hire are assigned a principal operations inspector (POI) who works directly with the company and coordinates FAA operating approval.

PRM

ILS PRM Approach and Precision Runway Monitor.

Problem-based learning

Lessons in such a way as to confront students with problems that are encountered in real life which force them to reach real-world solutions.

Procedure Turn

The maneuver prescribed when it is necessary to reverse direction to establish an aircraft on the intermediate approach segment or final approach course. The outbound course, direction of turn, distance within which the turn must be completed, and minimum altitude are specified in the procedure. However, unless otherwise restricted, the point at which the turn may be commenced and the type and rate of turn are left to the discretion of the pilot.

Procedure Turn Inbound

That point of a procedure turn maneuver where course reversal has been completed and an aircraft is established inbound on the intermediate approach segment or final approach course. A report of “procedure turn inbound” is normally used by ATC as a position report for separation purposes.

Profile Descent

An uninterrupted descent (except where level flight is required for speed adjustment; e.g., 250 knots at 10,000 feet MSL) from cruising altitude/level to interception of a glideslope or to a minimum altitude specified for the initial or intermediate approach segment of a nonprecision instrument approach. The profile descent normally terminates at the approach gate or where the glideslope or other appropriate minimum altitude is intercepted.

Profile Drag

The total of the skin friction drag and form drag for a two-dimensional airfoil section.

Profile view

Side view of an IAP chart illustrating the vertical approach path altitudes, headings, distances, and fixes.

Prognostic chart (contracted PROG)

A chart of expected or forecast conditions.

Progress Report

Position Report.

Progressive Taxi

Precise taxi instructions given to a pilot unfamiliar with the airport or issued in stages as the aircraft proceeds along the taxi route.

Prohibited Area

Airspace designated under 14 CFR Part 73 within which no person may operate an aircraft without the permission of the using agency.

Prominent Obstacle

An obstacle that meets one or more of the following conditions: a. An obstacle which stands out beyond the adjacent surface of surrounding terrain and immediately projects a noticeable hazard to aircraft in flight. b. An obstacle, not characterized as low and close in, whose height is no less than 300 feet above the departure end of takeoff runway (DER) elevation, is within 10NM from the DER, and that penetrates that airport/heliport’s diverse departure obstacle clearance surface (OCS). c. An obstacle beyond 10NM from an airport/heliport that requires an obstacle departure procedure (ODP) to ensure obstacle avoidance.

Propeller

A device for propelling an aircraft that, when rotated, produces by its action on the air, a thrust approximately perpendicular to its plane of rotation. It includes the control components normally supplied by its manufacturer.

Propeller

A device for propelling an aircraft that has blades on an engine-driven shaft and that, when rotated, produces by its action on the air, a thrust approximately perpendicular to its plane of rotation. It includes control components normally supplied by its manufacturer, but does not include main and auxiliary rotors or rotating airfoils of engines.

Propeller Blade Angle

The angle between the propeller chord and the propeller plane of rotation.

Propeller Lever

The control on a free power turbine turboprop that controls propeller speed and the selection for propeller feathering.

Propeller Slipstream

The volume of air accelerated behind a propeller producing thrust.

Propeller Synchronization

A condition in which all of the propellers have their pitch automatically adjusted to maintain a constant r.p.m. among all of the engines of a multiengine aircraft.

Propeller/rotor modulation error

Certain propeller RPM settings or helicopter rotor speeds can cause the VOR course deviation indicator (CDI) to fluctuate as much as ±6°. Slight changes to the RPM setting will normally smooth out this roughness.

Proposed Departure Time

The time that the aircraft expects to become airborne.

Pseudo-adiabatic lapse rate

Saturated-adiabatic lapse rate. The rate of decrease of temperature with height as saturated air is lifted with no gain or loss of heat from outside sources; varies with temperature, being greatest at low temperatures.

Psychomotor domain

A grouping of levels of learning associated with physical skill levels which range from perception through set, guided response, mechanism, complex overt response, and adaptation to origination.

Psychrometer

An instrument consisting of a wet-bulb and a dry-bulb thermometer for measuring wet-bulb and dry-bulb temperature; used to determine water vapor content of the air.

PT

Procedure Turn

PT

Procedure Turn

PTP

Point-To-Point

PTRS

Performance Tracking and Reporting System.

PTS

Practical Test Standards. (Obsolete term, replaced by Airman Certification Standards–ACS)

Public aircraft

Any of the following aircraft when not being used for a commercial purpose or to carry an individual other than a crewmember or qualified non-crewmember:
(1) An aircraft used only for the United States Government; an aircraft owned by the Government and operated by any person for purposes related to crew training, equipment development, or demonstration; an aircraft owned and operated by the government of a State, the District of Columbia, or a territory or possession of the United States or a political subdivision of one of these governments; or an aircraft exclusively leased for at least 90 continuous days by the government of a State, the District of Columbia, or a territory or possession of the United States or a political subdivision of one of these governments.
(i) For the sole purpose of determining public aircraft status, commercial purposes means the transportation of persons or property for compensation or hire, but does not include the operation of an aircraft by the armed forces for reimbursement when that reimbursement is required by any Federal statute, regulation, or directive, in effect on November 1, 1999, or by one government on behalf of another government under a cost reimbursement agreement if the government on whose behalf the operation is conducted certifies to the Administrator of the Federal Aviation Administration that the operation is necessary to respond to a significant and imminent threat to life or property (including natural resources) and that no service by a private operator is reasonably available to meet the threat.
(ii) For the sole purpose of determining public aircraft status, governmental function means an activity undertaken by a government, such as national defense, intelligence missions, firefighting, search and rescue, law enforcement (including transport of prisoners, detainees, and illegal aliens), aeronautical research, or biological or geological resource management.
(iii) For the sole purpose of determining public aircraft status, qualified non-crewmember means an individual, other than a member of the crew, aboard an aircraft operated by the armed forces or an intelligence agency of the United States Government, or whose presence is required to perform, or is associated with the performance of, a governmental function.
(2) An aircraft owned or operated by the armed forces or chartered to provide transportation to the armed forces if—
(i) The aircraft is operated in accordance with title 10 of the United States Code;
(ii) The aircraft is operated in the performance of a governmental function under title 14, 31, 32, or 50 of the United States Code and the aircraft is not used for commercial purposes; or
(iii) The aircraft is chartered to provide transportation to the armed forces and the Secretary of Defense (or the Secretary of the department in which the Coast Guard is operating) designates the operation of the aircraft as being required in the national interest.
(3) An aircraft owned or operated by the National Guard of a State, the District of Columbia, or any territory or possession of the United States, and that meets the criteria of paragraph (2) of this definition, qualifies as a public aircraft only to the extent that it is operated under the direct control of the Department of Defense.

Published Instrument Approach Procedure Visual Segment

A segment on an IAP chart annotated as “Fly Visual to Airport” or ”Fly Visual.” A dashed arrow will indicate the visual flight path on the profile and plan view with an associated note on the approximate heading and distance. The visual segment should be flown as a dead reckoning course while maintaining visual conditions.

Published Route

A route for which an IFR altitude has been established and published; e.g., Federal Airways, Jet Routes, Area Navigation Routes, Specified Direct Routes.

Pulse

Pertaining to radar, a brief burst of electromagnetic radiation emitted by the radar; of very short time duration.

Pulse length

Pertaining to radar, the dimension of a radar pulse; may be expressed as the time duration or the length in linear units. Linear dimension is equal to time duration multiplied by the speed of propagation (approximately the speed of light).

Q Route

`Q’ is the designator assigned to published RNAV routes used by the United States.

QFE

Transition Height

QICP

Qualified Internet Communications Provider

QNE

Transition Level

QNH

Transition Altitude

Quadrant

A quarter part of a circle, centered on a NAVAID, oriented clockwise from magnetic north as follows: NE quadrant 000-089, SE quadrant 090-179, SW quadrant 180-269, NW quadrant 270-359.

Quasi-stationary front (commonly called stationary front)

A front which is stationary or nearly so; conventionally, a front which is moving at a speed of less than 5 knots is generally considered to be quasi-stationary.

RA

Resolution Advisory,Radio Altitude

RA

Resolution Advisory

RAA

Remote Advisory Airport

Rabbit, the

High-intensity flasher system installed at many large airports. The flashers consist of a series of brilliant blue-white bursts of light flashing in sequence along the approach lights, giving the effect of a ball of light traveling towards the runway.

Radar

Radio Detection And Ranging.

Radar

A system that uses electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, weather formations, and terrain. The term RADAR was coined in 1941 as an acronym for Radio Detection and Ranging. The term has since entered the English language as a standard word, radar, losing the capitalization in the process.

RADAR (contraction for radio detection and ranging)

An electronic instrument used for the detection and ranging of distant objects of such composition that they scatter or reflect radio energy. Since hydrometeors can scatter radio energy, weather radars, operating on certain frequency bands, can detect the presence of precipitation, clouds, or both.

Radar altitude

The altitude of an aircraft determined by radar-type radio altimeter; thus the actual distance from the nearest terrain or water feature encompassed by the downward directed radar beam. For all practical purposes, it is the“actual” distance above a ground or inland water surface or the true altitude above an ocean surface.

Radar approach

The controller provides vectors while monitoring the progress of the flight with radar, guiding the pilot through the descent to the airport/heliport or to a specific runway.

Radar Approach Control Facility

A terminal ATC facility that uses radar and nonradar capabilities to provide approach control services to aircraft arriving, departing, or transiting airspace controlled by the facility. a. Provides radar ATC services to aircraft operating in the vicinity of one or more civil and/or military airports in a terminal area. The facility may provide services of a ground controlled approach (GCA); i.e., ASR and PAR approaches. A radar approach control facility may be operated by FAA, USAF, US Army, USN, USMC, or jointly by FAA and a military service. Specific facility nomenclatures are used for administrative purposes only and are related to the physical location of the facility and the operating service generally as follows: 1. Army Radar Approach Control (ARAC) (Army). 2. Radar Air Traffic Control Facility (RATCF) (Navy/FAA). 3. Radar Approach Control (RAPCON) (Air Force/FAA). 4. Terminal Radar Approach Control (TRACON) (FAA). 5. Air Traffic Control Tower (ATCT) (FAA). (Only those towers delegated approach control authority.

Radar beam

The focused energy radiated by radar similar to a flashlight or searchlight beam.

Radar Contact

A. Used by ATC to inform an aircraft that it is identified on the radar display and radar flight following will be provided until radar identification is terminated. Radar service may also be provided within the limits of necessity and capability. When a pilot is informed of “radar contact,” he/she automatically discontinues reporting over compulsory reporting points.
B. The term used to inform the controller that the aircraft is identified and approval is granted for the aircraft to enter the receiving controllers airspace.

Radar Contact Lost

Used by ATC to inform a pilot that radar data used to determine the aircraft’s position is no longer being received, or is no longer reliable and radar service is no longer being provided. The loss may be attributed to several factors including the aircraft merging with weather or ground clutter, the aircraft operating below radar line of sight coverage, the aircraft entering an area of poor radar return, failure of the aircraft transponder, or failure of the ground radar equipment.

Radar Environment

An area in which radar service may be provided.

Radar Flight Following

The observation of the progress of radar identified aircraft, whose primary navigation is being provided by the pilot, wherein the controller retains and correlates the aircraft identity with the appropriate target or target symbol displayed on the radar scope.

Radar Identification

The process of ascertaining that an observed radar target is the radar return from a particular aircraft.

Radar Identified Aircraft

An aircraft, the position of which has been correlated with an observed target or symbol on the radar display.

Radar Monitoring

The radar flight-following of aircraft, whose primary navigation is being performed by the pilot, to observe and note deviations from its authorized flight path, airway, or route. When being applied specifically to radar monitoring of instrument approaches; i.e., with precision approach radar (PAR) or radar monitoring of simultaneous ILS/MLS approaches, it includes advice and instructions whenever an aircraft nears or exceeds the prescribed PAR safety limit or simultaneous ILS/MLS no transgression zone.

Radar Required

A term displayed on charts and approach plates and included in FDC NOTAMs to alert pilots that segments of either an instrument approach procedure or a route are not navigable because of either the absence or unusability of a NAVAID. The pilot can expect to be provided radar navigational guidance while transiting segments labeled with this term.

Radar Route

A flight path or route over which an aircraft is vectored. Navigational guidance and altitude assignments are provided by ATC.

Radar Separation

Radar spacing of aircraft in accordance with established minima.

Radar Service

A term which encompasses one or more of the following services based on the use of radar which can be provided by a controller to a pilot of a radar identified aircraft: Radar Monitoring, Radar Navigational Guidance, and Radar Separation.

Radar Service Terminated

Used by ATC to inform a pilot that he/she will no longer be provided any of the services that could be received while in radar contact. Radar service is automatically terminated, and the pilot is not advised in the following cases: a. An aircraft cancels its IFR flight plan, except within Class B airspace, Class C airspace, a TRSA, or where Basic Radar service is provided. b. An aircraft conducting an instrument, visual, or contact approach has landed or has been instructed to change to advisory frequency. c. An arriving VFR aircraft, receiving radar service to a tower-controlled airport within Class B airspace, Class C airspace, a TRSA, or where sequencing service is provided, has landed; or to all other airports, is instructed to change to tower or advisory frequency. d. An aircraft completes a radar approach.

Radar summary chart

A weather product derived from the national radar network that graphically displays a summary of radar weather reports.

Radar Surveillance

The radar observation of a given geographical area for the purpose of performing some radar function.

Radar Traffic Advisories

Advisories issued to alert pilots to known or observed radar traffic which may affect the intended route of flight of their aircraft.

Radar weather report (SD)

A report issued by radar stations at 35 minutes after the hour, and special reports as needed. Provides information on the type, intensity, and location of the echo tops of the precipitation.

Radarsonde observation

A rawinsonde observation in which winds are determined by radar tracking a balloon-borne target.

Radial

A magnetic bearing extending from a VOR/VORTAC/TACAN navigation facility.

Radials

The courses oriented from a station.

Radiation

The emission of energy by a medium and transferred, either through free space or another medium, in the form of electromagnetic waves.

Radiation fog

Fog characteristically resulting when radiational cooling of the earth’s surface lowers the air temperature near the ground to or below its initial dew point on calm, clear nights.

Radio

A device used for communication.

Radio

Used to refer to a flight service station; e.g., “Seattle Radio” is used to call Seattle FSS.

Radio Altimeter

Aircraft equipment which makes use of the reflection of radio waves from the ground to determine the height of the aircraft above the surface.

Radio Beacon

Nondirectional Beacon.

Radio frequency (RF)

A term that refers to alternating current (AC) having characteristics such that, if the current is input to antenna, an electromagnetic (EM) field is generated suitable for wireless broadcasting and/or communications.

Radio frequency (RF)

Radio magnetic indicator (RMI)

An electronic navigation instrument that combines a magnetic compass with an ADF or VOR. The card of the RMI acts as a gyro-stabilized magnetic compass, and shows the magnetic heading the aircraft is flying.

Radio magnetic indicator (RMI)

Radio or radar altimeter

An electronic altimeter that determines the height of an aircraft above the terrain by measuring the time needed for a pulse of radio-frequency energy to travel from the aircraft to the ground and return.

Radio or radar altimeter

Radio wave

An electromagnetic wave (EM wave) with frequency characteristics useful for radio transmission.

Radio wave

An electromagnetic (EM ) wave with frequency characteristics useful for radio transmission.

Radiosonde

A weather instrument that observes and reports meteorological conditions from the upper atmosphere. This instrument is typically carried into the atmosphere by some form of weather balloon.

Radiosonde observation

A sounding made by the instrument.

RAIL

Runway Alignment Indicator Lights Sequenced Flashing Lights Which Are Installed Only In Combination With Other Light Systems

RAIM

Receiver Autonomous Integrity Monitoring.

RAIM

Receiver Autonomous Integrity Monitoring

Rain

A form of precipitation; drops are larger than drizzle and fall in relatively straight, although not necessarily vertical, paths as compared to drizzle which falls in irregular paths.

Rain shower

Precipitation from a cumuliform cloud; characterized by the suddenness of beginning and ending, by the rapid change of intensity, and usually by rapid change in the appearance of the sky; showery precipitation in the form of rain.

RAIS

Remote Airport Information Service

RAM recovery

The increase in thrust as a result of ram air pressures and density on the front of the engine caused by air velocity.

Ramp

Apron. A defined area on an airport or heliport intended to accommodate aircraft for purposes of loading or unloading passengers or cargo, refueling, parking, or maintenance. With regard to seaplanes, a ramp is used for access to the apron from the water.

Ramp Weight

The total weight of the aircraft while on the ramp. It differs from takeoff weight by the weight of the fuel that will be consumed in taxiing to the point of takeoff.

Random RNAV routes

Direct routes, based on area navigation capability, between waypoints defined in terms of latitude/longitude coordinates, degree-distance fixes, or offsets from established routes/airways at a specified distance and direction.

Random RNAV routes

Random Route

Any route not established or charted/published or not otherwise available to all users.

Range attenuation

Reduction of radar power density because of distance from the antenna. It occurs in the outgoing beam at a rate proportional to 1/(range²) The return signal is also attenuated at the same rate.

Range resolution

The ability of radar to distinguish between targets on the same azimuth but at different ranges.

Range-height indicator (RHI) scope

A radar indicator scope displaying a vertical cross section of targets along a selected azimuth.

Ranging signals

Transmitted from the GPS satellite, these allow the aircrafts receiver to determine range (distance) from each satellite.

Ranging signals

Transmitted from the GPS satellite, signals allowing the aircraft’s receiver to determine range (distance) from each satellite.

RAOB

A radiosonde observation.

Rapid decompression

The almost instantaneous loss of cabin pressure in aircraft with a pressurized cockpit or cabin.

Rate Of Turn

The rate in degrees/second of a turn.

Rated 2-minute OEI Power

With respect to rotorcraft turbine engines, the approved brake horsepower developed under static conditions at specified altitudes and temperatures within the operating limitations established for the engine under part 33 of this chapter, for continuation of one flight operation after the failure or shutdown of one engine in multiengine rotorcraft, for up to three periods of use no longer than 2 minutes each in any one flight, and followed by mandatory inspection and prescribed maintenance action.

Rated 21/2-minute OEI power

With respect to rotorcraft turbine engines, the approved brake horsepower developed under static conditions at specified altitudes and temperatures within the operating limitations established for the engine under part 33 of this chapter for periods of use no longer than 21/2minutes each after the failure or shutdown of one engine of a multiengine rotorcraft.

Rated 30-minute OEI power

With respect to rotorcraft turbine engines, the approved brake horsepower developed under static conditions at specified altitudes and temperatures within the operating limitations established for the engine under part 33 of this chapter, and limited in use to one period of use no longer than 30 minutes after the failure or shutdown of one engine of a multiengine rotorcraft.

Rated 30-second OEI Power

With respect to rotorcraft turbine engines, the approved brake horsepower developed under static conditions at specified altitudes and temperatures within the operating limitations established for the engine under part 33 of this chapter, for continuation of one flight operation after the failure or shutdown of one engine in multiengine rotorcraft, for up to three periods of use no longer than 30 seconds each in any one flight, and followed by mandatory inspection and prescribed maintenance action.

Rated continuous OEI power

With respect to rotorcraft turbine engines, the approved brake horsepower developed under static conditions at specified altitudes and temperatures within the operating limitations established for the engine under part 33 of this chapter, and limited in use to the time required to complete the flight after the failure or shutdown of one engine of a multiengine rotorcraft.

Rated maximum continuous augmented thrust

With respect to turbojet engine type certification, the approved jet thrust that is developed statically or in flight, in standard atmosphere at a specified altitude, with fluid injection or with the burning of fuel in a separate combustion chamber, within the engine operating limitations established under Part 33 of this chapter, and approved for unrestricted periods of use.

Rated maximum continuous power

With respect to reciprocating, turbopropeller, and turboshaft engines, the approved brake horsepower that is developed statically or in flight, in standard atmosphere at a specified altitude, within the engine operating limitations established under Part 33, and approved for unrestricted periods of use.

Rated maximum continuous thrust

With respect to turbojet engine type certification, the approved jet thrust that is developed statically or in flight, in standard atmosphere at a specified altitude, without fluid injection and without the burning of fuel in a separate combustion chamber, within the engine operating limitations established under Part 33 of this chapter, and approved for unrestricted periods of use.

Rated takeoff augmented thrust

With respect to turbojet engine type certification, the approved jet thrust that is developed statically under standard sea level conditions, with fluid injection or with the burning of fuel in a separate combustion chamber, within the engine operating limitations established under Part 33 of this chapter, and limited in use to periods of not over 5 minutes for takeoff operation.

Rated takeoff power

With respect to reciprocating, turbopropeller, and turboshaft engine type certification, the approved brake horsepower that is developed statically under standard sea level conditions, within the engine operating limitations established under Part 33, and limited in use to periods of not over 5 minutes for takeoff operation.

Rated takeoff thrust

With respect to turbojet engine type certification, the approved jet thrust that is developed statically under standard sea level conditions, without fluid injection and without the burning of fuel in a separate combustion chamber, within the engine operating limitations established under Part 33 of this chapter, and limited in use to periods of not over 5 minutes for takeoff operation.

Rating

A statement that, as a part of a certificate, sets forth special conditions, privileges, or limitations.

Rawin

A rawinsonde observation.

Rawinsonde observation

A combined winds aloft and radiosonde observation. Winds are determined by tracking the radiosonde by radio direction finder or radar.

RB

Relative Bearing.

RB

Relative Bearing.

RBI

Relative Bearing Indicator.

RBI

Relative Bearing Indicator.

RBN

Radio Beacon.

RCAG

Remote Center Air/Ground

RCC

Rescue Coordination Center

RCLM

Runway Centerline Marking.

RCLS

Runway Centerline Light System.

RCLS

Runway Centerline Lighting System

RCO

Remote Communications Outlet.

RCO

Remote Communications Outlet

RD

Rotor Diameter

RDOF

Radio Failure

Read Back

Repeat my message back to me.

Readiness

A principle of learning where the eagerness and single-mindedness of a person toward learning affect the outcome of the learning experience.

Receiver

In communication, the listener, reader, or student who takes in a message containing information from a source, processes it, reacts with understanding, and changes behavior in accordance with the message.

Receiver autonomous integrity monitoring (RAIM)

A system used to verify the usability of the received GPS signals and warns the pilot of any malfunction in the navigation system. This system is required for IFR-certified GPS units.

Receiver Autonomous Integrity Monitoring (RAIM)

A technique whereby a civil GNSS receiver/processor determines the integrity of the GNSS navigation signals without reference to sensors or non-DoD integrity systems other than the receiver itself. This determination is achieved by a consistency check among redundant pseudorange measurements.

Receiver autonomous integrity monitoring (RAIM).

A system used to verify the usability of the received GPS signals and warns the pilot of any malfunction in the navigation system. This system is required for IFR-certified GPS units.

Receiver-transmitter (RT)

A system that receives and transmits a signal and an indicator.

Receiver-transmitter (RT)

A system that receives and transmits a signal and an indicator.

Recency

Principle of learning stating that things learned recently are remembered better than things learned some time ago. As time passes, less is remembered. Instructors use this principle when summarizing the important points at the end of a lecture in order for students to better remember them.

Reciprocating Engine

An engine that converts the heat energy from burning fuel into the reciprocating movement of the pistons. This movement is converted into a rotary motion by the connecting rods and crankshaft.

Recommended altitude

An altitude depicted on an instrument approach chart with the altitude value neither underscored nor overscored. The depicted value is an advisory value.

Reduce Speed To (Speed)

Speed Adjustment.

Reduced vertical separation minimum (RVSM)

Reduces the vertical separation between flight levels (FL) 290 and 410 from 2,000 feet to 1,000 feet, and makes six additional FLs available for operation. Also see DRVSM.

Reduced Vertical Separation Minimums (RVSM)

RVSM airspace is where air traffic control separates aircraft by a minimum of 1,000 feet vertically between flight level (FL) 290 and FL 410 inclusive. RVSM airspace is special qualification airspace; the operator and the aircraft used by the operator must be approved by the Administrator. Air traffic control notifies operators of RVSM by providing route planing information.

Reduction Factor

A number, usually 100 or 1,000 by which a moment is divided to produce a smaller number that is less likely to cause mathematical errors when computing the center of gravity.

Reduction Gear

The gear arrangement in an aircraft engine that allows the engine to turn at a faster speed than the propeller.

Reference circle (also, distance circle)

The circle depicted in the plan view of an IAP chart that typically has a 10 NM radius, within which chart the elements are drawn to scale.

Reference Datum

(GAMA) An imaginary vertical plane from which all horizontal distances are measured for balance purpose.

Reference landing speed

The speed of the airplane, in a specified landing configuration, at the point where it descends through the 50 foot height in the determination of the landing distance.

Reference Landing Speed (Vref)

The speed of the airplane, in a specified landing configuration, at the point where it descends through the 50-foot height in the determination of the landing distance.

Refraction

In radar, bending of the radar beam by variations in atmospheric density, water vapor content, and temperature.

Region Of Reverse Command

Flight regime in which flight at a higher airspeed requires a lower power setting and a lower airspeed requires a higher power setting in order to maintain altitude.

Region of reverse command

Flight regime in which flight at a higher airspeed requires a lower power setting and a lower airspeed requires a higher power setting in order to maintain altitude.

Regions of command

The regions of normal and reversed command refers to the relationship between speed and the power required to maintain or change that speed in flight.

Regions of command

The “regions of normal and reversed command” refers to the relationship between speed and the power required to maintain or change that speed in flight.

Registration Certificate

A State and Federal certificate that documents aircraft ownership.

REIL

Runway End Identifier Lights.

REIL

Runway End Identifier Lights

Relative bearing (RB)

The angular difference between the aircraft heading and the direction to the station, measured clockwise from the nose of the aircraft.

Relative bearing indicator (RBI)

Also known as the fixed- card ADF, zero is always indicated at the top of the instrument and the needle indicates the relative bearing to the station.

Relative humidity

The ratio of the existing amount of water vapor in the air at a given temperature to the maximum amount that could exist at that temperature; usually expressed in percent.

Relative vorticity

Vorticity of the air relative to the Earth, disregarding the component of vorticity resulting from Earth’s rotation.

Relative Wind

The direction of the airflow with respect to the wing. If a wing moves forward horizontally, the relative wind moves backward horizontally. Relative wind is parallel to and opposite the flightpath of the airplane.

Relative wind

Direction of the airflow produced by an object moving through the air. The relative wind for an airplane in flight flows in a direction parallel with and opposite to the direction of flight; therefore, the actual flight path of the airplane determines the direction of the relative wind.

Relay question

Used in response to a student’s question, the student question is redirected to another student.

Release Time

A departure time restriction issued to a pilot by ATC (either directly or through an authorized relay) when necessary to separate a departing aircraft from other traffic.

Reliability

The degree to which test results are consistent with repeated measurements.

Remote Airport Advisory (RAA)

A remote service which may be provided by facilities, which are not located on the landing airport, but have a discrete ground-to-air communication frequency or tower frequency when the tower is closed, automated weather reporting with voice available to the pilot at the landing airport, and a continuous ASOS/AWSS/AWOS data display, other direct reading instruments, or manual observation is available to the AFSS specialist.

Remote Communications Outlet

An unmanned communications facility remotely controlled by air traffic personnel. RCOs serve FSSs. RTRs serve terminal ATC facilities. An RCO or RTR may be UHF or VHF and will extend the communication range of the air traffic facility. There are several classes of RCOs and RTRs. The class is determined by the number of transmitters or receivers. Classes A through G are used primarily for air/ground purposes. RCO and RTR class O facilities are nonprotected outlets subject to undetected and prolonged outages. RCO (O’s) and RTR (O’s) were established for the express purpose of providing ground-to-ground communications between air traffic control specialists and pilots located at a satellite airport for delivering en route clearances, issuing departure authorizations, and acknowledging instrument flight rules cancellations or departure/landing times. As a secondary function, they may be used for advisory purposes whenever the aircraft is below the coverage of the primary air/ground frequency.

Remote Communications Outlet (RCO)

An unmanned communications facility remotely controlled by air traffic personnel. RCOs serve FSSs and may be UHF or VHF. RCOs extend the communication range of the air traffic facility. RCOs were established to provide ground-to-ground communications between air traffic control specialists and pilots located at a satellite airport for delivering en route clearances, issuing departure authorizations, and acknowledging IFR cancellations or departure/landing times.

Remote scope

In radar meteorology a “slave” scope remoted from weather radar.

Report

Used to instruct pilots to advise ATC of specified information; e.g., “Report passing Hamilton VOR.”

Reporting Point

A geographical location in relation to which the position of an aircraft is reported. (See Compulsory Reporting Points)

Reporting point

A geographical location in relation to which the position of an aircraft is reported.

Repression

Theory of forgetting proposing that a person is more likely to forget information which is unpleasant or produces anxiety.

Request Full Route Clearance

Used by pilots to request that the entire route of flight be read verbatim in an ATC clearance. Such request should be made to preclude receiving an ATC clearance based on the original filed flight plan when a filed IFR flight plan has been revised by the pilot, company, or operations prior to departure.

Required navigation performance (RNP)

A specified level of accuracy defined by a lateral area of confined airspace in which an RNP-certified aircraft operates.

Required Navigation Performance (RNP)

A statement of the navigational performance necessary for operation within a defined airspace. The following terms are commonly associated with RNP: Required Navigation Performance Level or Type (RNP-X), Required Navigation Performance (RNP) Airspace, Actual Navigation Performance (ANP), Estimated Position Error (EPE), Lateral Navigation (LNAV), and Vertical Navigation (VNAV).

Required Navigation Performance (RNP) Airspace

A generic term designating airspace, route (s), leg (s), operation (s), or procedure (s) where minimum required navigational performance (RNP) have been established.

Required Navigation Performance Level Or Type (RNP-X)

A value, in nautical miles (NM), from the intended horizontal position within which an aircraft would be at least 95-percent of the total flying time.

Residual Fuel

Fuel that remains trapped in the system after draining the fuel from the aircraft with the aircraft in level flight attitude. The weight of this residual fuel is counted as part of the empty weight of the aircraft.

Resolution

Pertaining to radar, the ability of radar to show discrete targets separately, i.e., the better the resolution, the closer two targets can be to each other, and still be detected as separate targets.

Resolution Advisory

A display indication given to the pilot by the traffic alert and collision avoidance systems (TCAS II) recommending a maneuver to increase vertical separation relative to an intruding aircraft. Positive, negative, and vertical speed limit (VSL) advisories constitute the resolution advisories. A resolution advisory is also classified as corrective or preventive

Response

Possible answer to a multiple-choice test item. The correct response is often called the keyed response, and incorrect responses are called distractors.

Restricted area

Airspace designated under 14 CFR part 73 within which the flight of aircraft, while not wholly prohibited, is subject to restriction.

Restricted Area

Airspace designated under 14 CFR Part 73, within which the flight of aircraft, while not wholly prohibited, is subject to restriction. Most restricted areas are designated joint use and IFR/VFR operations in the area may be authorized by the controlling ATC facility when it is not being utilized by the using agency. Restricted areas are depicted on en route charts. Where joint use is authorized, the name of the ATC controlling facility is also shown.

Resume Normal Speed

Used by ATC to advise a pilot that previously issued speed control restrictions are deleted. An instruction to “resume normal speed” does not delete speed restrictions that are applicable to published procedures of upcoming segments of flight, unless specifically stated by ATC. This does not relieve the pilot of those speed restrictions which are applicable to 14 CFR Section 91.117.

Resume Own Navigation

Used by ATC to advise a pilot to resume his/her own navigational responsibility. It is issued after completion of a radar vector or when radar contact is lost while the aircraft is being radar vectored.

Reverse question

Used in response to a student’s question. Rather than give a direct answer to the student’s query, the instructor returns the question to the same student to provide the answer.

Reverse sensing

The VOR needle appearing to indicate the reverse of normal operation.

Reverse sensing

The VOR needle appearing to indicate the reverse of normal operation.

Reverse Thrust

A condition where jet thrust is directed forward during landing to increase the rate of deceleration.

Reversing Propeller

A propeller system with a pitch change mechanism that includes full reversing capability. When the pilot moves the throttle controls to reverse, the blade angle changes to a pitch angle and produces a reverse thrust, which slows the airplane down during a landing.

Review and evaluation

The fourth and last step in the teaching process, which consists of a review of all material and an evaluation of the students. In the telling and doing technique of flight instruction, this step consists of the instructor evaluating the student’s performance while the student performs the required procedure.

RF

Radio Frequency.

RF

Radio Frequency.

RFFS

Rescue and Firefighting Services.

RFM

Rotorcraft Flight Manual

Rhetorical question

Generally, a question asked for a purpose other than to obtain the information the question asks. For this handbook’s purpose, a question asked to stimulate group thought. Normally answered by the instructor, it is more commonly used in lecturing rather than in guided discussions.

Rhodopsin

The photosensitive pigments that initiate the visual response in the rods of the eye.

Ridge (also called ridge line)

In meteorology, an elongated area of relatively high atmospheric pressure; usually associated with and most clearly identified as an area of maximum anticyclonic curvature of the wind flow (isobars, contours, or streamlines).

Rigging

The final adjustment and alignment of an aircraft and its flight control system that provides the proper aerodynamic characteristics.

Right Base Area

A type of Terminal Arrival Area. A 30NM arc centered on the left corner IAF (Initial Approach Fix). The area shares a boundary with the straight-in area except that it extends out for 30NM from the IAF and is bounded on the other side by a line extending from the IF through the FAF to the arc.

Rigidity

The characteristic of a gyroscope that prevents its axis of rotation tilting as the Earth rotates.

Rigidity

The characteristic of a gyroscope that prevents its axis of rotation tilting as the Earth rotates.

Rigidity in space

The principle that a wheel with a heavily weighted rim spinning rapidly will remain in a fixed position in the plane in which it is spinning.

RIL

Runway Intersection Lights

Rime ice

Rough, milky, opaque ice formed by the instantaneous freezing of small supercooled water droplets.

Rime ice

Rough, milky, opaque ice formed by the instantaneous freezing of small supercooled water droplets.

Rime Ice

A rough, milky, opaque ice formed by the instantaneous freezing of small, supercooled water drops. It is generally rougher in appearance than clear ice.

Risk

The future impact of a hazard that is not eliminated or controlled.

Risk

The future impact of a hazard that is not eliminated or controlled.

Risk elements

There are four fundamental risk elements in aviation: the pilot, the aircraft, the environment, and the type of operation that comprise any given aviation situation.

Risk management

The part of the decision-making process which relies on situational awareness, problem recognition, and good judgment to reduce risks associated with each flight.

Risk management

The part of the decision-making process which relies on situational awareness, problem recognition, and good judgment to reduce risks associated with each flight.

RJ

Regional Jet

RLIM

Runway Light Intensity Monitor

RLSD

Released

RMI

Radio Magnetic Indicator.

RMI

Radio Magnetic Indicator

RNAV

Area Navigation.

RNAV

Area Navigation

RNAV Approach

An instrument approach procedure which relies on aircraft area navigation equipment for navigational guidance.

RNAV DP

A DP developed for RNAV-equipped aircraft whose ground track is based on satellite or DME/DME navigation systems.

RNP

Required Navigation Performance.

RNP

Required Navigation Performance

ROC

Required Obstacle Clearance

Rocket

An aircraft propelled by ejected expanding gases generated in the engine from self-contained propellants and not dependent on the intake of outside substances. It includes any part which becomes separated during the operation.

Rocketsonde

A type of radiosonde launched by a rocket and making its measurements during a parachute descent; capable of obtaining soundings to a much greater height than possible by balloon or aircraft.

Roger

I have received all of your last transmission. It should not be used to answer a question requiring a yes or a no answer.

Roll

The motion of the aircraft about the longitudinal axis. It is controlled by the ailerons.

Roll cloud

A dense and horizontal roll-shaped accessory cloud located on the lower leading edge of a cumulonimbus or less often, a rapidly developing cumulus; indicative of turbulence. Sometimes improperly called rotor cloud.

Roll-out RVR

The RVR readout values obtained from sensors located nearest the rollout end of the runway.

Rote learning

A basic level of learning in which the student has the ability to repeat back something learned, with no understanding or ability to apply what was learned.

Rotor cloud

A turbulent cloud formation found in the lee of some large mountain barriers, the air in the cloud rotates around an axis parallel to the range; indicative of possible violent turbulence. Sometimes improperly called roll cloud.

Rotorcraft

A heavier-than-air aircraft that depends principally for its support in flight on the lift generated by one or more rotors.

Rotorcraft-load combination

The combination of a rotorcraft and an external-load, including the external-load attaching means. Rotorcraft-load combinations are designated as Class A, Class B, Class C, and Class D, as follows:
(1) Class A rotorcraft-load combination means one in which the external load cannot move freely, cannot be jettisoned, and does not extend below the landing gear.
(2) Class B rotorcraft-load combination means one in which the external load is jettisonable and is lifted free of land or water during the rotorcraft operation.
(3) Class C rotorcraft-load combination means one in which the external load is jettisonable and remains in contact with land or water during the rotorcraft operation.
(4) Class D rotorcraft-load combination means one in which the external-load is other than a Class A, B, or C and has been specifically approved by the Administrator for that operation.

Roundout (Flare)

A pitch-up during landing approach to reduce rate of descent and forward speed prior to touchdown.

Route

A defined path, consisting of one or more courses in a horizontal plane, which aircraft traverse over the surface of the earth.

Route Segment

As used in Air Traffic Control, a part of a route that can be defined by two navigational fixes, two NAVAIDs, or a fix and a NAVAID.

RPAT

RNP Parallel Approach Runway Transitions

RR

Low or Medium Frequency Radio Range Station.

RRTES

Reroutes

RSA

Runway Safety Area

RSP

Runway Safety Program

RT

Receiver-Transmitter.

Rudder

The movable primary control surface mounted on the trailing edge of the vertical fin of an airplane. Movement of the rudder rotates the airplane about its vertical axis.

Rudder

The movable primary control surface mounted on the trailing edge of the vertical fin of an airplane. Movement of the rudder rotates the airplane about its vertical axis.

Ruddervator

A pair of control surfaces on the tail of an aircraft arranged in the form of a V. These surfaces, when moved together by the control wheel, serve as elevators, and when moved differentially by the rudder pedals, serve as a rudder.

Ruddervator

Runback Ice

Ice that forms from the freezing or refreezing of water leaving protected surfaces and running back to unprotected surfaces.

Runway

A defined rectangular area on a land airport prepared for the landing and takeoff run of aircraft along its length. Runways are normally numbered in relation to their magnetic direction rounded off to the nearest 10 degrees; e.g., Runway 1, Runway 25.

Runway Centerline Lighting

Flush centerline lights spaced at 50-foot intervals beginning 75 feet from the landing threshold and extending to within 75 feet of the opposite end of the runway.

Runway Centerline Lights

Runway centerline lights are installed on some precision approach runways to facilitate landing under adverse visibility conditions. They are located along the runway centerline and are spaced at 50-foot intervals. When viewed from the landing threshold, the runway centerline lights are white until the last 3,000 feet of the runway. The white lights begin to alternate with red for the next 2,000 feet, and for the last 1,000 feet of the runway, all centerline lights are red.

Runway Centerline Markings

The runway centerline identifies the center of the runway and provides alignment guidance during takeoff and landings. The centerline consists of a line of uniformly spaced stripes and gaps.

Runway Edge Lights

Runway edge lights are used to outline the edges of runways during periods of darkness or restricted visibility conditions. These light systems are classified according to the intensity or brightness they are capable of producing: they are the High Intensity Runway Lights (HIRL), Medium Intensity Runway Lights (MIRL), and the Low Intensity Runway Lights (LIRL). The HIRL and MIRL systems have variable intensity controls, whereas the LIRLs normally have one intensity setting.

Runway end identifier lights (REIL)

A pair of synchronized flashing lights, located laterally on each side of the runway threshold, providing rapid and positive identification of the approach end of a runway.

Runway end identifier lights (REIL)

A pair of synchronized flashing lights, located laterally on each side of the runway threshold, providing rapid and positive identification of the approach end of a runway.

Runway Gradient

The average slope, measured in percent, between two ends or points on a runway. Runway gradient is depicted on Government aerodrome sketches when total runway gradient exceeds 0.3%.

Runway Heading

The magnetic direction that corresponds with the runway centerline extended, not the painted runway numbers on the runway. Pilots cleared to “fly or maintain runway heading” are expected to fly or maintain the published heading that corresponds with the extended centerline of the departure runway (until otherwise instructed by ATC), and are not to apply drift correction; e.g., RWY 4, actual magnetic heading of the runway centerline 044.22°, fly 044°.

Runway Hotspots

Locations on a particular airport that historically have hazardous intersections. Hot spots alert pilots to the fact that there may be a lack of visibility at certain points or the tower may be unable to see that particular intersection. Whatever the reason, pilots need to be aware that these hazardous intersections exist and they should be increasingly vigilant when approaching and taxiing through these intersections. Pilots are typically notified of these areas by a Letter to Airmen or by accessing the FAA Office of Runway Safety.

Runway In Use/Active Runway/Duty Runway

Any runway or runways currently being used for takeoff or landing. When multiple runways are used, they are all considered active runways. In the metering sense, a selectable adapted item which specifies the landing runway configuration or direction of traffic flow. The adapted optimum flight plan from each transition fix to the vertex is determined by the runway configuration for arrival metering processing purposes.

Runway Incursion

An occurrence at an airport involving an aircraft, vehicle, person, or object on the ground that creates a collision hazard or results in a loss of separation with an aircraft that is taking off, intending to take off, landing, or intending to land.

Runway Incursion

Any occurrence at an airport involving an aircraft, vehicle, person, or object on the ground that creates a collision hazard or results in loss of separation with an aircraft taking off, intending to takeoff, landing, or intending to land.

Runway Lights/Runway Edge Lights

Lights having a prescribed angle of emission used to define the lateral limits of a runway. Runway lights are uniformly spaced at intervals of approximately 200 feet, and the intensity may be controlled or preset.

Runway Markings

Airport Marking Aids. Markings used on runway and taxiway surfaces to identify a specific runway, a runway threshold, a centerline, a hold line, etc. A runway should be marked in accordance with its present usage such as: a. Visual. b. Nonprecision instrument. c. Precision instrument.

Runway OFZ

The runway OFZ (Obstacle Free Zone) is a defined volume of airspace centered above the runway. The runway OFZ is the airspace above a surface whose elevation at any point is the same as the elevation of the nearest point on the runway centerline. The runway OFZ extends 200 feet beyond each end of the runway. The width is as follows: 1. For runways serving large airplanes, the greater of: (a) 400 feet, or (b) 180 feet, plus the wingspan of the most demanding airplane, plus 20 feet per 1,000 feet of airport elevation. 2. For runways serving only small airplanes: (a) 300 feet for precision instrument runways. (b) 250 feet for other runways serving small airplanes with approach speeds of 50 knots, or more. (c) 120 feet for other runways serving small airplanes with approach speeds of less than 50 knots.

Runway Overrun

In military aviation exclusively, a stabilized or paved area beyond the end of a runway, of the same width as the runway plus shoulders, centered on the extended runway centerline.

Runway Profile Descent

An instrument flight rules (IFR) air traffic control arrival procedure to a runway published for pilot use in graphic and/or textual form and may be associated with a STAR. Runway Profile Descents provide routing and may depict crossing altitudes, speed restrictions, and headings to be flown from the en route structure to the point where the pilot will receive clearance for and execute an instrument approach procedure. A Runway Profile Descent may apply to more than one runway if so stated on the chart.

Runway Safety Area

A defined surface surrounding the runway prepared, or suitable, for reducing the risk of damage to airplanes in the event of an undershoot, overshoot, or excursion from the runway. The dimensions of the RSA vary and can be determined by using the criteria contained within AC 150/5300-13, Airport Design, Chapter 3. Figure 3-1 in AC 150/5300-13 depicts the RSA. The design standards dictate that the RSA shall be: a. Cleared, graded, and have no potentially hazardous ruts, humps, depressions, or other surface variations; b. Drained by grading or storm sewers to prevent water accumulation; c. Capable, under dry conditions, of supporting snow removal equipment, aircraft rescue and firefighting equipment, and the occasional passage of aircraft without causing structural damage to the aircraft; and, d. Free of objects, except for objects that need to be located in the runway safety area because of their function. These objects shall be constructed on low impact resistant supports (frangible mounted structures) to the lowest practical height with the frangible point no higher than 3 inches above grade.

Runway Safety Program (RSP)

Designed to create and execute a plan of action that reduces the number of runway incursions at the nations airports.

Runway temperature

The temperature of the air just above a runway, ideally at engine and/or wing height, used in the determination of density altitude; useful at airports when critical values of density altitude prevail.

Runway Threshold Markings

Runway threshold markings come in two configurations. They either consist of eight longitudinal stripes of uniform dimensions disposed symmetrically about the runway centerline, or the number of stripes is related to the runway width. A threshold marking helps identify the beginning of the runway that is available for landing. In some instances, the landing threshold may be displaced.

Runway Transition

A. Conventional STARs/SIDs. The portion of a STAR/SID that serves a particular runway or runways at an airport.
B. RNAV STARs/SIDs. Defines a path(s) from the common route to the final point(s) on a STAR. For a SID, the common route that serves a particular runway or runways at an airport.

Runway Use Program

A noise abatement runway selection plan designed to enhance noise abatement efforts with regard to airport communities for arriving and departing aircraft. These plans are developed into runway use programs and apply to all turbojet aircraft 12,500 pounds or heavier; turbojet aircraft less than 12,500 pounds are included only if the airport proprietor determines that the aircraft creates a noise problem. Runway use programs are coordinated with FAA offices, and safety criteria used in these programs are developed by the Office of Flight Operations. Runway use programs are administered by the Air Traffic Service as “Formal” or “Informal” programs.

Runway visibility

The meteorological visibility along an identified runway determined from a specified point on the runway; may be determined by a transmissometer or by an observer.

Runway Visibility Value (RVV)

The visibility determined for a particular runway by a transmissometer. A meter provides a continuous indication of the visibility (reported in miles or fractions of miles) for the runway. RVV is used in lieu of prevailing visibility in determining minimums for a particular runway.

Runway visibility value (RVV)

The visibility determined for a particular runway by a transmissometer.

Runway visual range

An instrumentally derived horizontal distance a pilot should see down the runway from the approach end; based on either the sighting of high intensity runway lights or on the visual contrast of other objects, whichever yields the greatest visual range.

Runway Visual Range (RVR)

An estimate of the maximum distance at which the runway, or the specified lights or markers delineating it, can be seen from a position above a specific point on the runway centerline. RVR is normally determined by visibility sensors or transmissometers located alongside and higher than the centerline of the runway. RVR is reported in hundreds of feet.

Runway Visual Range (RVR)

An instrumentally derived value, based on standard calibrations, that represents the horizontal distance a pilot will see down the runway from the approach end. It is based on the sighting of either high intensity runway lights or on the visual contrast of other targets whichever yields the greater visual range. RVR, in contrast to prevailing or runway visibility, is based on what a pilot in a moving aircraft should see looking down the runway. RVR is horizontal visual range, not slant visual range. It is based on the measurement of a transmissometer made near the touchdown point of the instrument runway and is reported in hundreds of feet. RVR is used in lieu of RVV and/or prevailing visibility in determining minimums for a particular runway.

Runway [ICAO]

A defined rectangular area on a land aerodrome prepared for the landing and take-off of aircraft.

RVR

Runway Visual Range.

RVR

Runway Visual Range as measured in the Touchdown Zone Area.

RVSM

Reduced Vertical Separation Minimums

RVSM

Reduced Vertical Separation Minimum

RVV

Runway Visibility Value.

RVV

Runway Visibility Value.

RWSL

Runway Status Light

RWY

Runway

RWY

Runway

RWY CONFIG

Runway Configuration

RY

Runway

SA

Selective Availability.

SA

Selective Availability.

SAA

Special Activity Airspace

SAAAR

Special Aircraft and Aircrew Authorization Required

SAAAR

Special Aircraft and Aircrew Authorization Required

Safety (Squat) Switch

An electrical switch mounted on one of the landing gear struts. It is used to sense when the weight of the aircraft is on the wheels.

Safety Alert

A safety alert issued by ATC to aircraft under their control if ATC is aware the aircraft is at an altitude which, in the controller’s judgment, places the aircraft in unsafe proximity to terrain, obstructions, or other aircraft. The controller may discontinue the issuance of further alerts if the pilot advises he/she is taking action to correct the situation or has the other aircraft in sight. Note: The issuance of a safety alert is contingent upon the capability of the controller to have an awareness of an unsafe condition. The course of action provided will be predicated on other traffic under ATC control. Once the alert is issued, it is solely the pilot’s prerogative to determine what course of action, if any, he/she will take.

SALS

Short Approach Light System.

SAM

System Area Monitor

Same Direction Aircraft

Aircraft are operating in the same direction when: a. They are following the same track in the same direction; or b. Their tracks are parallel and the aircraft are flying in the same direction; or c. Their tracks intersect at an angle of less than 45 degrees.

SAMS

Special Use Airspace Management System

Santa Ana

A hot, dry, foehn wind, generally from the northeast or east, occurring west of the Sierra Nevada Mountains especially in the pass and river valley near Santa Ana, California.

SAR

Search and Rescue

SAS

Stability Augmentation System

SATCOM

Satellite Communications.

Satellite ephemeris data

Data broadcast by the GPS satellite containing very accurate orbital data for that satellite, atmospheric propagation data, and satellite clock error data.

Satellite ephemeris data

Data broadcast by the GPS satellite containing very accurate orbital data for that satellite, atmospheric propagation data, and satellite clock error data.

SATNAV

Satellite Navigation

Saturated adiabatic lapse rate

The rate of decrease of temperature with height as saturated air is lifted with no gain or loss of heat from outside sources; varies with temperature, being greatest at low temperatures.

Saturation

The condition of the atmosphere when actual water vapor present is the maximum possible at existing temperature.

Say Again

Used to request a repeat of the last transmission. Usually specifies transmission or portion thereof not understood or received; e.g., “Say again all after ABRAM VOR.”

Say Altitude

Used by ATC to ascertain an aircraft’s specific altitude/flight level. When the aircraft is climbing or descending, the pilot should state the indicated altitude rounded to the nearest 100 feet.

Say Heading

Used by ATC to request an aircraft heading. The pilot should state the actual heading of the aircraft.

SBAS

Satellite-based Augmentation System

Scan

A procedure used by the pilot to visually identify all resources of information in flight.

Scan

The first fundamental skill of instrument flight, also known as cross-check; the continuous and logical observation of instruments for attitude and performance information.

SCAT-1 DGPS

Special Category I Differential GPS

Scenario-based training (SBT)

Training method that uses a highly structured script of real world experiences to address aviation training objectives in an operational environment.

Scheduled Time Of Arrival (STA)

A STA is the desired time that an aircraft should cross a certain point (landing or metering fix). It takes other traffic and airspace configuration into account. A STA time shows the results of the TMA scheduler that has calculated an arrival time according to parameters such as optimized spacing, aircraft performance, and weather.

Scud

Small detached masses of stratus fractus clouds below a layer of higher clouds, usually nimbostratus.

SDF

Simplified Directional Facility.

Sea breeze

A coastal breeze blowing from sea to land caused by the temperature difference when the land surface is warmer than the sea surface. The sea breeze usually occurs during the day and alternates with the land breeze that blows in the opposite direction at night.

Sea fog

A type of advection fog formed when air that has been lying over a warm surface is transported over a colder water surface.

Sea Lane

A designated portion of water outlined by visual surface markers for and intended to be used by aircraft designed to operate on water.

Sea Level

A reference height used to determine standard atmospheric conditions and altitude measurements.

Sea level engine

A reciprocating aircraft engine having a rated takeoff power that is producible only at sea level.

Sea level pressure

The atmospheric pressure at mean sea level, either directly measured by stations at sea level or empirically determined from the station pressure and temperature by stations not at sea level; used as a common reference for analyses of surface pressure patterns.

Sea smoke

Same as steam fog—fog formed when cold air moves over relatively warm water or wet ground.

Search And Rescue

A service which seeks missing aircraft and assists those found to be in need of assistance. It is a cooperative effort using the facilities and services of available Federal, state and local agencies. The U.S. Coast Guard is responsible for coordination of search and rescue for the Maritime Region, and the U.S. Air Force is responsible for search and rescue for the Inland Region. Information pertinent to search and rescue should be passed through any air traffic facility or be transmitted directly to the Rescue Coordination Center by telephone.

Search And Rescue Facility

A facility responsible for maintaining and operating a search and rescue (SAR) service to render aid to persons and property in distress. It is any SAR unit, station, NET, or other operational activity which can be usefully employed during an SAR Mission; e.g., a Civil Air Patrol Wing, or a Coast Guard Station.

SECNOT

Security Notice

Second in command

A pilot who is designated to be second in command of an aircraft during flight time.

Sectional aeronautical charts

Designed for visual navigation of slow- or medium-speed aircraft. Topographic information on these charts features the portrayal of relief, and a judicious selection of visual check points for VFR flight. Aeronautical information includes visual and radio aids to navigation, airports, controlled airspace, restricted areas, obstructions and related data.

Sector visibility

Meteorological visibility within a specified sector of the horizon circle.

See And Avoid

When weather conditions permit, pilots operating IFR or VFR are required to observe and maneuver to avoid other aircraft. Right-of-way rules are contained in 14 CFR Part 91.

Segmented Circle

A visual ground based structure to provide traffic pattern information.

Segments Of An Instrument Approach Procedure

An instrument approach procedure may have as many as four separate segments depending on how the approach procedure is structured. Initial Approach, Intermediate Approach, Final Approach, and Missed Approach.

Selection-type test items

Test items requiring the student to choose from two or more alternatives provided. True-false, matching, and multiple-choice type questions are examples of selection type test items.

Selective availability (SA)

A satellite technology permitting the Department of Defense (DOD) to create, in the interest of national security, a significant clock and ephemeris error in the satellites, resulting in a navigation error.

Selective availability (SA)

Self-concept

A perception factor that ties together how people feel about themselves with how well they receive experiences.

Semicircular canal

An inner ear organ that detects angular acceleration of the body.

Semicircular canal

An inner ear organ that detects angular acceleration of the body.

Semimonocoque

A fuselage design that includes a substructure of bulkheads and/or formers, along with stringers, to support flight loads and stresses imposed on the fuselage.

Sensitive altimeter

A form of multipointer pneumatic altimeter with an adjustable barometric scale that allows the reference pressure to be set to any desired level.

Sensitive altimeter

A form of multipointer pneumatic altimeter with an adjustable barometric scale that allows the reference pressure to be set to any desired level.

Sensitivity time control

A radar circuit designed to correct for range attenuation so that echo intensity on the scope is proportional to reflectivity of the target regardless of range.

Sensory register

That portion of the brain which receives input from the five senses. The individual’s preconceived concept of what is important determines how the register prioritizes the information for passing it on to the rest of the brain for action.

Separation

In air traffic control, the spacing of aircraft to achieve their safe and orderly movement in flight and while landing and taking off.

Separation Minima

The minimum longitudinal, lateral, or vertical distances by which aircraft are spaced through the application of air traffic control procedures.

SER

Start End of Runway

Service

A generic term that designates functions or assistance available from or rendered by air traffic control. For example, Class C service would denote the ATC services provided within a Class C airspace area.

Service Ceiling

The maximum density altitude where the best rate-of-climb airspeed will produce a 100 feet-per-minute climb at maximum weight while in a clean configuration with maximum continuous power.

Service ceiling

The maximum density altitude where the best rate-of-climb airspeed will produce a 100-feet-per-minute climb at maximum weight while in a clean configuration with maximum continuous power.

Servo

A motor or other form of actuator which receives a small signal from the control device and exerts a large force to accomplish the desired work.

Servo Tab

An auxiliary control mounted on a primary control surface, which automatically moves in the direction opposite the primary control to provide an aerodynamic assist in the movement of the control.

Severe Icing

The rate of accumulation is such that deicing/anti-icing equipment fails to reduce or control the hazard. Immediate flight diversion is necessary.

Severe Icing

The rate of ice accumulation is such that ice protection systems fail to remove the accumulation of ice and accumulation occurs in areas not normally prone to icing, such as aft of protected surfaces and other areas identified by the manufacturer. A representative accretion rate for reference purposes is more than 3 inches (7.5 cm) per hour6 on the outer wing. Immediate exit is required by many Airworthiness Directives (AD), flight manuals, and operations under part 91, §§ 91.13(a) and 91.527; part 121, § 121.341; part 125, § 125.221; and part 135, § 135.227.7

Severe Weather Forecast Alerts

Preliminary messages issued in order to alert users that a Severe Weather Watch Bulletin (WW) is being issued. These messages define areas of possible severe thunderstorms or tornado activity. The messages are unscheduled and issued as required by the Storm Prediction Center (SPC) at Norman, Oklahoma.

SFL

Sequenced Flashing Lights

SFR

Special Flight Rules

Shaft Horse Power (SHP)

Turboshaft engines are rated in shaft horsepower and calculated by use of a dynamometer device. Shaft horsepower is exhaust thrust converted to a rotating shaft.

Shear

Wind shear. The rate of change of wind velocity (direction and/or speed) per unit distance; conventionally expressed as vertical or horizontal wind shear.

SHF

Super High Frequency

Shock Waves

A compression wave formed when a body moves through the air at a speed greater than the speed of sound.

Short Range Clearance

A clearance issued to a departing IFR flight which authorizes IFR flight to a specific fix short of the destination while air traffic control facilities are coordinating and obtaining the complete clearance.

Short Takeoff And Landing Aircraft

An aircraft which, at some weight within its approved operating weight, is capable of operating from a runway in compliance with the applicable STOL characteristics, airworthiness, operations, noise, and pollution standards.

Show

Unless the context otherwise requires, to show to the satisfaction of the Administrator.

Shower

SIAP

Standard Instrument Approach Procedure

SID

Standard Instrument Departure

Sideslip

A slip in which the airplane’s longitudinal axis remains parallel to the original flightpath, but the airplane no longer flies straight ahead. Instead, the horizontal component of wing lift forces the airplane to move sideways toward the low wing.

Sidestep Maneuver

A visual maneuver accomplished by a pilot at the completion of an instrument approach to permit a straight-in landing on a parallel runway not more than 1,200 feet to either side of the runway to which the instrument approach was conducted.

SIDS

Standard Instrument Departure Procedures.

SIGMET

The acronym for Significant Meteorological information. A weather advisory issued concerning weather significant to the safety of all aircraft.

SIGMET

A weather advisory issued concerning weather significant to the safety of all aircraft. SIGMET advisories cover severe and extreme turbulence, severe icing, and widespread dust or sandstorms that reduce visibility to less than 3 miles.

Signal-to-noise ratio

An indication of signal strength received compared to background noise, which is a measure of how adequate the received signal is.

Signal-to-noise ratio

An indication of signal strength received compared to background noise, which is a measure of the adequacy of the received signal.

Significant Meteorological Information

SIGMET.

Significant Meteorological Information (SIGMET)

Information about in-flight weather of operational significance to the safety of all aircraft. SIGMETs may include severe icing. (See CWA and AIRMET.)

Significant Point

A point, whether a named intersection, a NAVAID, a fix derived from a NAVAID(s), or geographical coordinate expressed in degrees of latitude and longitude, which is established for the purpose of providing separation, as a reporting point, or to delineate a route of flight.

Significant weather prognostic

Presents four panels showing forecast significant weather.

Simplex

Transmission and reception on the same frequency.

Simplex

Transmission and reception on the same frequency.

Simplified directional facility (SDF)

A NAVAID used for nonprecision instrument approaches. The final approach course is similar to that of an ILS localizer; however, the SDF course may be offset from the runway, generally not more than 3°, and the course may be wider than the localizer, resulting in a lower degree of accuracy.

Simulated Flameout

A practice approach by a jet aircraft (normally military) at idle thrust to a runway. The approach may start at a runway (high key) and may continue on a relatively high and wide downwind leg with a continuous turn to final. It terminates in landing or low approach. The purpose of this approach is to simulate a flameout.

Simultaneous ILS Approaches

An approach system permitting simultaneous ILS/MLS approaches to airports having parallel runways separated by at least 4,300 feet between centerlines. Integral parts of a total system are ILS/MLS, radar, communications, ATC procedures, and appropriate airborne equipment.

Simultaneous MLS Approaches

Single Direction Routes

Preferred IFR Routes which are sometimes depicted on high altitude en route charts and which are normally flown in one direction only.

Single Engine Absolute Ceiling

The altitude that a twin-engine airplane can no longer climb with one engine inoperative.

Single-pilot resource management (SRM)

The ability for crew or pilot to manage all resources effectively to ensure the outcome of the flight is successful.

Single-Pilot Resource Management (SRM)

The art/science of managing all the resources (both onboard the aircraft and from outside sources) available to a single pilot (prior and during flight) to ensure that the successful outcome of the flight is never in doubt.

Single-pilot resource management (SRM)

The ability for a pilot to manage all resources effectively to ensure the outcome of the flight is successful.

Situational awareness

Pilot knowledge of where the aircraft is in regard to location, air traffic control, weather, regulations, aircraft status, and other factors that may affect flight.

Situational awareness

The accurate perception and understanding of all the factors and conditions within the four fundamental risk elements that affect safety before, during, and after the flight.

Situational awareness

Pilot knowledge of where the aircraft is in regard to location, air traffic control, weather, regulations, aircraft status, and other factors that may affect flight.

Skid

A condition where the tail of the airplane follows a path outside the path of the nose during a turn.

Skidding turn

An uncoordinated turn in which the rate of turn is too great for the angle of bank, pulling the aircraft to the outside of the turn.

Skidding turn

An uncoordinated turn in which the rate of turn is too great for the angle of bank, pulling the aircraft to the outside of the turn.

Skill knowledge

Knowledge reflected in motor or manual skills and in cognitive or mental skills that manifests itself in the doing of something.

Skills and procedures

The procedural, psychomotor, and perceptual skills used to control a specific aircraft or its systems. They are the stick and rudder or airmanship abilities that are gained through conventional training, are perfected, and become almost automatic through experience.

Skills and procedures

The procedural, psychomotor, and perceptual skills used to control a specific aircraft or its systems. They are the airmanship abilities that are gained through conventional training, are perfected, and become almost automatic through experience.

Skin friction drag

Drag generated between air molecules and the solid surface of the aircraft.

Skyspotter

A pilot who has received specialized training in observing and reporting inflight weather phenomena.

Slant range

The horizontal distance from the aircraft antenna to the ground station, due to line-of-sight transmission of the DME signal.

Slant range

The horizontal distance from the aircraft antenna to the ground station, due to line-of-sight transmission of the DME signal.

Slant visibility

For an airborne observer, the distance at which he can see and distinguish objects on the ground.

Slaved compass

A system whereby the heading gyro is slaved to, or continuously corrected to bring its direction readings into agreement with a remotely located magnetic direction sensing device (usually this is a flux valve or flux gate compass).

Slaved compass

A system whereby the heading gyro is “slaved to,” or continuously corrected to bring its direction readings into agreement with a remotely located magnetic direction sensing device (usually a flux valve or flux gate compass).

Sleet

Ice pellets mixed with rain or snow.

Slip

An intentional maneuver to decrease airspeed or increase rate of descent, and to compensate for a crosswind on landing. A slip can also be unintentional when the pilot fails to maintain the aircraft in coordinated flight.

Slipping turn

An uncoordinated turn in which the aircraft is banked too much for the rate of turn, so the horizontal lift component is greater than the centrifugal force, pulling the aircraft toward the inside of the turn.

Slipping turn

Slow Taxi

To taxi a float plane at low power or low RPM.

SM

Statute Mile

SM

Statute Mile

SMA

Surface Movement Advisor

Small

An Aircraft Class Wake Turbulence Separation Minima. Aircraft of 41,000 pounds or less maximum certificated takeoff weight.

Small Aircraft

An aircraft weighing 12,500 pounds or less, maximum certificated takeoff weight. As defined in 14 CFR part 1.

Small airplane

An airplane of 12,500 pounds or less maximum certificated takeoff weight.

Smog

A mixture of smoke and fog.

Smoke

A restriction to visibility resulting from combustion.

Snow

Precipitation composed of white or translucent ice crystals, chiefly in complex branched hexagonal form.

Snow flurry

Popular term for snow shower, particularly of a very light and brief nature.

Snow grains

Precipitation of very small, white opaque grains of ice, similar in structure to snow crystals. The grains are fairly flat or elongated, with diameters generally less than 0.04 inch (1 mm.).

Snow pellets

Precipitation consisting of white, opaque approximately round (sometimes conical) ice particles having a snow-like structure, and about 0.08 to 0.2 inch in diameter; crisp and easily crushed, differing in this respect from snow grains; rebound from a hard surface and often break up.

Snow shower

SNR

Signal-to-noise Ratio

SOIA

Simultaneous Offset Instrument Approaches

Solar radiation

The total electromagnetic radiation emitted by the sun.

Somatogravic illusion

The misperception of being in a nose-up or nose-down attitude, caused by a rapid acceleration or deceleration while in flight situations that lack visual reference.

Somatogravic illusion

The misperception of being in a nose-up or nose-down attitude, caused by a rapid acceleration or deceleration while in flight situations that lack visual reference.

SOP

Standard Operating Procedure

SOP

Standard Operating Procedure

Sounding

In meteorology, an upper-air observation; a radiosonde observation.

Source

In communication, the sender, speaker, transmitter, or instructor who composes and transmits a message made up of symbols which are meaningful to listeners and readers.

Source region

An extensive area of the earth’s surface characterized by relatively uniform surface conditions where large masses of air remain long enough to take on characteristic temperature and moisture properties imparted by that surface.

Spatial disorientation

The state of confusion due to misleading information being sent to the brain from various sensory organs, resulting in a lack of awareness of the aircraft position in relation to a specific reference point.

Spatial disorientation

SPC

Storm Prediction Center

Speak Slower

Used in verbal communications as a request to reduce speech rate.

SPECI

Non-Routine (Special) Aviation Weather Report

Special Activity Airspace (SAA)

Any airspace with defined dimensions within the National Airspace System wherein limitations may be imposed upon aircraft operations. This airspace may be restricted areas, prohibited areas, military operations areas, air ATC assigned airspace, and any other designated airspace areas. The dimensions of this airspace are programmed into URET and can be designated as either active or inactive by screen entry. Aircraft trajectories are constantly tested against the dimensions of active areas and alerts issued to the applicable sectors when violations are predicted.

Special Emergency

A condition of air piracy or other hostile act by a person(s) aboard an aircraft which threatens the safety of the aircraft or its passengers.

Special flight permit

A flight permit issued to an aircraft that does not meet airworthiness requirements but is capable of safe flight. A special flight permit can be issued to move an aircraft for the purposes of maintenance or repair, buyer delivery, manufacturer flight tests, evacuation from danger, or customer demonstration. Also referred to as a ferry permit.

Special fuel consumption

The amount of fuel in pounds per hour consumed or required by an engine per brake horsepower or per pound of thrust.

Special Instrument Approach Procedure

A procedure approved by the FAA for individual operators, but not published in FAR 97 for public use.

Special use airspace

Airspace in which flight activities are subject to restrictions that can create limitations on the mixed use of airspace. Consists of prohibited, restricted, warning, military operations, and alert areas.

Special Use Airspace

Airspace of defined dimensions identified by an area on the surface of the earth wherein activities must be confined because of their nature and/or wherein limitations may be imposed upon aircraft operations that are not a part of those activities. Types of special use airspace are: Alert Area, Controlled Firing Area, Military Operations Area (MOA), Prohibited Area, Restricted Area, and Warning Area.

Special VFR Conditions

Meteorological conditions that are less than those required for basic VFR flight in Class B, C, D, or E surface areas and in which some aircraft are permitted flight under visual flight rules.

Special VFR Operations

Aircraft operating in accordance with clearances within Class B, C, D, and E surface areas in weather conditions less than the basic VFR weather minima. Such operations must be requested by the pilot and approved by ATC.

Specific Fuel Consumption

Number of pounds of fuel consumed in 1 hour to produce 1 HP.

Specific humidity

The ratio by weight of water vapor in a sample of air to the combined weight of water vapor and dry air. Compare mixing ratio.

Speed

The distance traveled in a given time.

Speed Adjustment

An ATC procedure used to request pilots to adjust aircraft speed to a specific value for the purpose of providing desired spacing. Pilots are expected to maintain a speed of plus or minus 10 knots or 0.02 Mach number of the specified speed. Examples of speed adjustments are: a. “Increase/reduce speed to Mach point (number.)” b. “Increase/reduce speed to (speed in knots)” or “Increase/reduce speed (number of knots) knots.”

Speed Brakes

A control system that extends from the airplane structure into the airstream to produce drag and slow the airplane.

Speed Instability

A condition in the region of reverse command where a disturbance that causes the airspeed to decrease causes total drag to increase, which in turn, causes the airspeed to decrease further.

Speed Sense

The ability to sense instantly and react to any reasonable variation of airspeed.

Spin

An aggravated stall that results in what is termed an “autorotation” wherein the airplane follows a downward corkscrew path. As the airplane rotates around the vertical axis, the rising wing is less stalled than the descending wing creating a rolling, yawing, and pitching motion.

Spiral Instability

A condition that exists when the static directional stability of the airplane is very strong as compared to the effect of its dihedral in maintaining lateral equilibrium.

Spiral instability

A condition that exists when the static directional stability of the airplane is very strong as compared to the effect of its dihedral in maintaining lateral equilibrium.

Spiraling Slipstream

The slipstream of a propeller-driven airplane rotates around the airplane. This slipstream strikes the left side of the vertical fin, causing the airplane to yaw slightly. Vertical stabilizer offset is sometimes used by aircraft designers to counteract this tendency.

Spiraling slipstream

The slipstream of a propeller-driven airplane rotates around the airplane. This slipstream strikes the left side of the vertical fin, causing the aircraft to yaw slightly. Rudder offset is sometimes used by aircraft designers to counteract this tendency.

Split Shaft Turbine Engine

See Free Power Turbine Engine.

Spoilers

High-drag devices that can be raised into the air flowing over an airfoil, reducing lift and increasing drag. Spoilers are used for roll control on some aircraft. Deploying spoilers on both wings at the same time allows the aircraft to descend without gaining speed. Spoilers are also used to shorten the ground roll after landing.

Spool

A shaft in a turbine engine which drives one or more compressors with the power derived from one or more turbines.

SPS

Standard Positioning Service

SPT

Strategic Planning Team. The Strategic Planning Team acts as a focal point for the development of collaborative Strategic Plans of Operation. Their goal is to provide advanced planning information for system users and air traffic facilities in order to maximize the utilization of the NAS in an organized and equitable manner.

Squall

A sudden increase in wind speed by at least 15 knots to a peak of 20 knots or more and lasting for at least one minute. Essential difference between a gust and a squall is the duration of the peak speed.

Squall line

Any nonfrontal line or narrow band of active thunderstorms (with or without squalls).

Squawk (Mode, Code, Function)

Activate specific modes/codes/functions on the aircraft transponder; e.g., “Squawk three/alpha, two one zero five, low.”

SRM

Single-pilot Resource Management.

SRM

Single-pilot Resource Management.

SSALF

Simplified Short Approach Light System With Sequenced Flashing Lights

SSALR

Simplified Short Approach Light System With Runway Alignment Indicator Lights

SSALS

Simplified Short Approach Light System.

SSALSR

Simplified Short Approach Light System with Runway Alignment Indicator Lights.

SSR

Secondary Surveillance Radar.

SSR

Secondary Surveillance Radar.

SSV

Standard Service Volume.

SSV

Standard Service Volume.

St. Elmo’s Fire

A corona discharge which lights up the aircraft surface areas where maximum static discharge occurs.

St. Elmo’s Fire

A luminous brush discharge of electricity from protruding objects, such as masts and yardarms of ships, aircraft, lightning rods, steeples, etc., occurring in stormy weather. Also called corposant.

Stabilator

A single-piece horizontal tail surface on an airplane that pivots around a central hinge point. A stabilator serves the purposes of both the horizontal stabilizer and the elevator.

Stabilator

A single-piece horizontal tail surface on an airplane that pivots around a central hinge point. A stabilator serves the purposes of both the horizontal stabilizer and the elevators.

Stability

The inherent quality of an airplane to correct for conditions that may disturb its equilibrium, and to return or to continue on the original flightpath. It is primarily an airplane design characteristic.

Stability

A state of the atmosphere in which the vertical distribution of temperature is such that a parcel will resist displacement from its initial level.

Stability

Stabilized Approach

A landing approach in which the pilot establishes and maintains a constant angle glidepath towards a predetermined point on the landing runway. It is based on the pilot’s judgment of certain visual cues, and depends on the maintenance of a constant final descent airspeed and configuration.

Staging/Queuing

The placement, integration, and segregation of departure aircraft in designated movement areas of an airport by departure fix, EDCT, and/or restriction.

Stagnant hypoxia

A type of hypoxia that results when the oxygen-rich blood in the lungs is not moving to the tissues that need it.

Stagnation Point

The point on a surface where the local air velocity is zero. The region of maximum icing collection efficiency is near this point.

Stall

A rapid decrease in lift caused by the separation of airflow from the wing’s surface brought on by exceeding the critical angle of attack. A stall can occur at any pitch attitude or airspeed.

Stall Strips

A spoiler attached to the inboard leading edge of some wings to cause the center section of the wing to stall before the tips. This assures lateral control throughout the stall.

Stand By

Means the controller or pilot must pause for a few seconds, usually to attend to other duties of a higher priority. Also means to wait as in “stand by for clearance.” The caller should reestablish contact if a delay is lengthy. “Stand by” is not an approval or denial.

Standard Atmosphere

At sea level, the standard atmosphere consists of a barometric pressure of 29.92 inches of mercury (in. Hg.) or 1013.2 millibars, and a temperature of 15°C (59°F). Pressure and temperature normally decrease as altitude increases. The standard lapse rate in the lower atmosphere for each 1,000 feet of altitude is approximately 1 in. Hg. and 2°C (3.5°F). For example, the standard pressure and temperature at 3,000 feet mean sea level (MSL) is 26.92 in. Hg. 29.92" Hg – 3" Hg) and 9°C (15°C - 6°C).

Standard atmosphere

A hypothetical atmosphere based on climatological averages comprised of numerous physical constants of which the most important are: (1) A surface temperature of 59° F (15° C) and a surface pressure of 29.92 inches of mercury (1013.2 millibars) at sea level; (2) A lapse rate in the troposphere of 6.5° C per kilometer (approximately 2° C per 1,000 feet); (3) A tropopause of 11 kilometers (approximately 36,000 feet) with a temperature of -56.5° C; and (4) An isothermal lapse rate in the stratosphere to an altitude of 24 kilometers (approximately 80,000 feet).

Standard atmosphere

At sea level, the standard atmosphere consists of a barometric pressure of 29.92 inches of mercury ("Hg) or 1013.2 millibars, and a temperature of 15°C (59°F). Pressure and temperature normally decrease as altitude increases. The standard lapse rate in the lower atmosphere for each 1,000 feet of altitude is approximately 1"Hg and 2°C (3.5°F). For example, the standard pressure and temperature at 3,000 feet mean sea level (MSL) are 26.92"Hg (29.92"Hg – 3"Hg) and 9°C (15°C – 6°C).

Standard Day

See Standard Atmosphere.

Standard Empty Weight (GAMA)

This weight consists of the airframe, engines, and all items of operating equipment that have fixed locations and are permanently installed in the airplane; including fixed ballast, hydraulic fluid, unusable fuel, and full engine oil.

Standard holding pattern

A holding pattern in which all turns are made to the right.

Standard Instrument Approach Procedure (SIAP)

Instrument Approach Procedure.

Standard Instrument Departure (SID)

A preplanned instrument flight rule (IFR) air traffic control (ATC) departure procedure printed for pilot/controller use in graphic form to provide obstacle clearance and a transition from the terminal area to the appropriate en route structure. SIDs are primarily designed for system enhancement to expedite traffic flow and to reduce pilot/controller workload. ATC clearance must always be received prior to flying a SID.

Standard instrument departure procedures (SIDS).

Published procedures to expedite clearance delivery and to facilitate transition between takeoff and en route operations.

Standard rate turn

A turn in which an aircraft changes its direction at a rate of 3° per second (360° in 2 minutes) for low- or medium-speed aircraft. For high-speed aircraft, the standard rate turn is 1 1⁄2° per second (360° in 4 minutes).

Standard rate turn

Standard Service Volume

Most air navigation radio aids which provide positive course guidance have a designated standard service volume (SSV). The SSV defines the reception limits of unrestricted NAVAIDS which are usable for random/unpublished route navigation. Standard service volume limitations do not apply to published IFR routes or procedures. See the AIM for the SSV for specific NAVAID types.

Standard T

An RNAV approach whose design allows direct flight to any one of three initial approach fixes (IAF) and eliminates the need for procedure turns. The standard design is to align the procedure on the extended centerline with the missed approach point (MAP) at the runway threshold, the final approach fix (FAF), and the initial approach/intermediate fix (IAF/IF). The other two IAFs will be established perpendicular to the IF.

Standard Terminal Arrival (STAR)

Provides a common method for departing the en route structure and navigating to your destination. A STAR is a preplanned instrument flight rule ATC arrival procedure published for pilot use in graphic and textual form to simplify clearance delivery procedures. STARs provide you with a transition from the en route structure to an outer fix or an instrument approach fix or arrival waypoint in the terminal area, and they usually terminate with an instrument or visual approach procedure.

Standard Terminal Arrival (STAR) Charts

Designed to expedite air traffic control arrival procedures and to facilitate transition between en route and instrument approach operations. Each STAR procedure is presented as a separate chart and may serve a single airport or more than one airport in a given geographical location. i. Airport Taxi Charts Designed to expedite the efficient and safe flow of ground traffic at an airport. These charts are identified by the official airport name; e.g., Ronald Reagan Washington National Airport.

Standard weights

Weights established for numerous items involved in weight and balance computations. These weights should not be used if actual weights are available.

Standard-Rate Turn

A turn at the rate of 3º per second which enables the airplane to complete a 360º turn in 2 minutes.

Standardized Taxi Routes

Coded taxi routes that follow typical taxiway traffic patterns to move aircraft between gates and runways. ATC issues clearances using these coded routes to reduce radio communication and eliminate taxi instruction misinterpretation.

Standing cloud

A lenticular cloud. (standing lenticular altocumulus) A species of cloud whose elements have the form of more or less isolated, generally smooth lenses or almonds. These clouds appear most often in formations of orographic origin, the result of lee waves, in which case they remain nearly stationary with respect to the terrain (standing cloud), but they also occur in regions without marked orography.

Standing wave

A wave that remains stationary in a moving fluid. In aviation operations it is used most commonly to refer to a lee wave or mountain wave.

STAR

Standard Terminal Arrival Route.

STAR Transition

A published segment used to connect one or more en route airways, jet routes, or RNAV routes to the basic STAR procedure. It is one of several routes that bring traffic from different directions into one STAR. NACO publishes STARs for airports with procedures authorized by the FAA, and these STARs are included at the front of each Terminal Procedures Publication regional booklet.

STARS

Standard Terminal Automation Replacement System

Start End of Runway (SER)

The beginning of the takeoff runway available.

Starter/Generator

A combined unit used on turbine engines. The device acts as a starter for rotating the engine, and after running, internal circuits are shifted to convert the device into a generator.

Static Load

The load imposed on an aircraft structure due to the weight of the aircraft and its contents.

Static longitudinal stability

The aerodynamic pitching moments required to return the aircraft to the equilibrium angle of attack.

Static longitudinal stability

The aerodynamic pitching moments required to return the aircraft to the equilibrium angle of attack.

Static pressure

Pressure of air that is still, or not moving, measured perpendicular to the surface of the aircraft.

Static pressure

Pressure of air that is still or not moving, measured perpendicular to the surface of the aircraft.

Static Stability

The initial tendency an aircraft displays when disturbed from a state of equilibrium.

Static stability

The initial tendency an aircraft displays when disturbed from a state of equilibrium.

Station

A location in the airplane that is identified by a number designating its distance in inches from the datum. The datum is, therefore, identified as station zero. An item located at station +50 would have an arm of 50 inches.

Station

Station Declination

The angular difference between true north and the zero radial of a VOR at the time the VOR was last site checked.

Station pressure

The actual atmospheric pressure at the observing station.

Stationary front

Same as quasi-stationary front—a front which is stationary or nearly so; conventionally, a front which is moving at a speed of less than 5 knots is generally considered to be quasi-stationary.

Stationary Front

A front that has little or no movement because the opposing forces of the two air masses are relatively balanced.

STC

Supplemental Type Certificate

Steam fog

Fog formed when cold air moves over relatively warm water or wet ground.

Steep turns

In instrument flight, any turn greater than standard rate; in visual flight, anything greater than a 45° bank.

Steep turns

In instrument flight, any turn greater than standard rate; in visual flight, anything greater than a 45° bank.

Stem

The part of a multiple choice test item consisting of the question, statement, or problem.

Stepdown Fix

A fix permitting additional descent within a segment of an instrument approach procedure by identifying a point at which a controlling obstacle has been safely overflown.

Stick Puller

A device that applies aft pressure on the control column when the airplane is approaching the maximum operating speed.

Stick Pusher

A device that applies an abrupt and large forward force on the control column when the airplane is nearing an angle of attack where a stall could occur.

Stick Shaker

An artificial stall warning device that vibrates the control column.

STMP

Special Traffic Management Program

STMP

Special Traffic Management Program. Reservation program implemented to regulate arrivals and/or departures at airports that are in areas hosting special events such as the Masters Golf Tournament and Indianapolis 500.

STOL Aircraft

Short Takeoff And Landing Aircraft.

Stop Altitude Squawk

Used by ATC to inform an aircraft to turn-off the automatic altitude reporting feature of its transponder. It is issued when the verbally reported altitude varies 300 feet or more from the automatic altitude report.

Stop And Go

A procedure wherein an aircraft will land, make a complete stop on the runway, and then commence a takeoff from that point.

Stop Squawk (Mode Or Code)

Used by ATC to tell the pilot to turn specified functions of the aircraft transponder off.

Stopway

An area beyond the takeoff runway no less wide than the runway and centered upon the extended centerline of the runway, able to support the airplane during an aborted takeoff, without causing structural damage to the airplane, and designated by the airport authorities for use in decelerating the airplane during an aborted takeoff.

Storm detection radar

A weather radar designed to detect hydrometeors of precipitation size; used primarily to detect storms with large drops or hailstones as opposed to clouds and light precipitation of small drop size.

Straight-In Approach IFR

An instrument approach wherein final approach is begun without first having executed a procedure turn, not necessarily completed with a straight-in landing or made to straight-in landing minimums.

Straight-In Approach VFR

Entry into the traffic pattern by interception of the extended runway centerline (final approach course) without executing any other portion of the traffic pattern.

Straight-In Area

A type of Terminal Arrival Area. A 30NM arc centered on the IF (Intermediate Fix) bounded by a straight line extending through the IF perpendicular to the intermediate course.

Straight-In Landing

A landing made on a runway aligned within 30° of the final approach course following completion of an instrument approach.

Straight-In Minimums

Straight-In Landing Minimums.

Strain Sensor

A device that converts a physical phenomenon into an electrical signal. Strain sensors in a wheel axle sense the amount the axle deflects and create an electrical signal that is proportional to the force that caused the deflection.

Strapdown system

An INS in which the accelerometers and gyros are permanently “strapped down” or aligned with the three axes of the aircraft.

Stratiform

Descriptive of clouds of extensive horizontal development, as contrasted to vertically developed cumuliform clouds; characteristic of stable air and, therefore, composed of small water droplets.

Stratocumulus

A low cloud, predominantly stratiform in gray and/or whitish patches or layers, mayor may not merge; elements are tessellated, rounded, or roll-shaped with relatively flat tops.

Stratoshere

A layer of the atmosphere above the tropopause extending to a height of approximately 160,000 feet.

Stratosphere

The atmospheric layer above the tropopause, average altitude of base and top, 7 and 22 miles respectively; characterized by a slight average increase of temperature from base to top and is very stable; also characterized by low moisture content and absence of clouds.

Stratus

A low, gray cloud layer or sheet with a fairly uniform base; sometimes appears in ragged patches; seldom produces precipitation but may produce drizzle or snow grains. A stratiform cloud.

Stratus Clouds.

Clouds that form layers with a uniform base. Stratus clouds can appear in ragged patches and may produce drizzle, rain, or snow.

Stratus fractus

A stratus layer (low, gray cloud layer or sheet) that has a base in the form of irregular shreds (fractus), appearing as if torn.

Streamline

In meteorology, a line whose tangent is the wind direction at any point along the line. A flowline.

Stress

The body’s response to demands placed upon it.

Stress management

The personal analysis of the kinds of stress experienced while flying, the application of appropriate stress assessment tools, and other coping mechanisms.

Stress Risers

A scratch, groove, rivet hole, forging defect or other structural discontinuity that causes a concentration of stress.

Structural icing

The accumulation of ice on the exterior of the aircraft.

Structural icing

The accumulation of ice on the exterior of the aircraft.

Structural Station

This is a location in the aircraft, such as a bulkhead, which is identified by a number designating its distance in inches or percent MAC from the datum. The datum is, therefore, identified as station zero. The stations and arms are identical. An item located at station +50 would have an arm of 50 inches.

SUA

Special Use Airspace

SUA/ISE

Special Use Airspace/Inflight Service Enhancement

Sublimation

Process by which a solid is changed to a gas without going through the liquid state.

Sublimation

A process in which ice turns directly into water vapor without passing through a liquid state.

Subrefraction

Less than normal bending of the radar beam resulting from abnormal vertical gradients of temperature and/or water vapor.

Subsidence

A descending motion of air in the atmosphere over a rather broad area; usually associated with divergence.

Subsonic

Speed below the speed of sound.

Suction relief valve

A relief valve in an instrument vacuum system required to maintain the correct low pressure inside the instrument case for the proper operation of the gyros.

Suction relief valve

A relief valve in an instrument vacuum system required to maintain the correct low pressure inside the instrument case for the proper operation of the gyros.

Suitable RNAV system

An RNAV system that meets the required performance established for a type of operation, e.g. IFR; and is suitable for operation over the route to be flown in terms of any performance criteria (including accuracy) established by the air navigation service provider for certain routes (e.g. oceanic, ATS routes, and IAPs). An RNAV system’s suitability is dependent upon the availability of ground and/or satellite navigation aids that are needed to meet any route performance criteria that may be prescribed in route specifications to navigate the aircraft along the route to be flown. Information on suitable RNAV systems is published in FAA guidance material.

Summation principle

The principle states that the cover assigned to a layer is equal to the summation of the sky cover of the lowest layer plus the additional coverage at all successively higher layers up to and including the layer in question. Thus, no layer can be assigned a sky cover less than a lower layer, and no sky cover can be greater than 1.0 (10/10).

Sunset And Sunrise

The mean solar times of sunset and sunrise as published in the Nautical Almanac, converted to local standard time for the locality concerned. Within Alaska, the end of evening civil twilight and the beginning of morning civil twilight, as defined for each locality.

Super High Frequency

The frequency band between 3 and 30 gigahertz (GHz). The elevation and azimuth stations of the microwave landing system operate from 5031 MHz to 5091 MHz in this spectrum.

Superadiabatic lapse rate

A lapse rate greater than the dry-adiabatic lapse rate.

Supercharger

An engine or exhaust-driven air compressor used to provide additional pressure to the induction air so the engine can produce additional power.

Supercooled Large Drops (SLD)

Water drops with a diameter greater than 50 micrometers (0.05 mm) that exist in a liquid form at air temperatures below 0 °C. SLD conditions include freezing drizzle drops and freezing raindrops.

Supercooled water

Liquid water at temperatures colder than freezing.

Supercooled water droplets

Water droplets that have been cooled below the freezing point, but are still in a liquid state.

Superrefraction

More than normal bending of the radar beam resulting from abnormal vertical gradients of temperature and/or water vapor. (3)

Supersonic

Speed above the speed of sound.

Supplemental Type Certificate (STC)

A certificate authorizing an alteration to an airframe, engine, or component that has been granted an Approved Type Certificate.

Supply-type test item

Question in which the student supplies answers as opposed to selecting from choices provided. Essay or fill-in-the blank type questions are examples of supply- type test items.

Surface analysis chart

A report that depicts an analysis of the current surface weather. Shows the areas of high and low pressure, fronts, temperatures, dewpoints, wind directions and speeds, local weather, and visual obstructions.

Surface Area

The airspace contained by the lateral boundary of the Class B, C, D, or E airspace designated for an airport that begins at the surface and extends upward.

Surface Incident

An event during which authorized or unauthorized/unapproved movement occurs in the movement area or an occurrence in the movement area associated with the operation of an aircraft that affects or could affect the safety of flight.

Surface inversion

An inversion with its base at the surface, often caused by cooling of the air near the surface as a result of terrestrial radiation, especially at night.

Surface Movement Guidance Control System (SMGCS)

Facilitates the safe movement of aircraft and vehicles at airports where scheduled air carriers are conducting authorized operations. The SMGCS low visibility taxi plan includes the improvement of taxiway and runway signs, markings, and lighting, as well as the creation of SMGCS low visibility taxi route charts.

Surface visibility

Visibility observed from eye-level above the ground.

Surveillance Approach

An instrument approach wherein the air traffic controller issues instructions, for pilot compliance, based on aircraft position in relation to the final approach course (azimuth), and the distance (range) from the end of the runway as displayed on the controller’s radar scope. The controller will provide recommended altitudes on final approach if requested by the pilot.

SVFR

Special Visual Flight Rules

SVRWX

Severe Weather

SWAP

Severe Weather Avoidance Plan

SWAP

Severe Weather Avoidance Plan. An approved plan to minimize the effect of severe weather on traffic flows in impacted terminal and/or ARTCC areas. SWAP is normally implemented to provide the least disruption to the ATC system when flight through portions of airspace is difficult or impossible due to severe weather.

Swept Wing

A wing planform in which the tips of the wing are farther back than the wing root.

SWSL

Supplemental Weather Service Locations

Symbols

In communication, simple oral and visual codes such as words, gestures, and facial expressions which are formed into sentences, paragraphs, lectures, or chapters to compose and transmit a message that means something to the receiver of the information.

Synchro

A device used to transmit indications of angular movement or position from one location to another.

Synchro

A device used to transmit indications of angular movement or position from one location to another.

Synoptic chart

A chart, such as the familiar weather map, which depicts the distribution of meteorological conditions over an area at a given time.

Synthetic Vision

A visual display of terrain, obstructions, runways, and other surface features that creates a virtual view of what the pilot would see out the window. This tool could be used to supplement normal vision in low visibility conditions, as well as to increase situational awareness in IMC.

Synthetic vision

A computer-generated image of the external scene topography from the perspective of the flight deck that is derived from aircraft attitude, high-precision navigation solution, and database of terrain, obstacles and relevant cultural features.

Synthetic vision system

An electronic means to display a synthetic vision image of the external scene topography to the flight crew.

T-Tail

An aircraft with the horizontal stabilizer mounted on the top of the vertical stabilizer, forming a T.

TA

Traffic Advisory

TA

Traffic Advisory

TAA

Terminal arrival area.

TAC

Terminal Area Chart

TACAN

Tactical air navigation.

TACAN

Tactical Air Navigation Aid. An ultra-high frequency electronic rho-theta air navigation aid which provides suitably equipped aircraft with a continuous indication of bearing and distance to the TACAN station.

TAF

Terminal Aerodrome Forecast

TAF

Aerodrome Forecast

Tailwheel Aircraft

See Conventional landing Gear.

Tailwind

Any wind more than 90 degrees to the longitudinal axis of the runway. The magnetic direction of the runway shall be used as the basis for determining the longitudinal axis.

Takeoff Area

Landing Area.

Takeoff decision speed (V1)

Per 14 CFR section 23.51: “the calibrated airspeed on the ground at which, as a result of engine failure or other reasons, the pilot assumed to have made a decision to continue or discontinue the takeoff.”.

Takeoff distance

The distance required to complete an all-engines operative takeoff to the 35-foot height. It must be at least 15 percent less than the distance required for a one-engine inoperative engine takeoff. This distance is not normally a limiting factor as it is usually less than the one-engine inoperative takeoff distance.

Takeoff Distance Available (TODA)

ICAO defines TODA as the length of the takeoff runway available plus the length of the clearway, if provided.

Takeoff power

(1) With respect to reciprocating engines, the brake horsepower that is developed under standard sea level conditions, and under the maximum conditions of crankshaft rotational speed and engine manifold pressure approved for the normal takeoff, and limited in continuous use to the period of time shown in the approved engine specification; and
(2) With respect to turbine engines, the brake horsepower that is developed under static conditions at a specified altitude and atmospheric temperature, and under the maximum conditions of rotor shaft rotational speed and gas temperature approved for the normal takeoff, and limited in continuous use to the period of time shown in the approved engine specification.

Takeoff Roll (Ground Roll)

The total distance required for an aircraft to become airborne.

Takeoff Run Available (TORA)

The runway length declared available and suitable for the ground run of an airplane taking off.

Takeoff safety speed (V2)

Per 14 CFR part 1: “A referenced airspeed obtained after lift-off at which the required one-engine-inoperative climb performance can be achieved.”.

Takeoff thrust

With respect to turbine engines, the jet thrust that is developed under static conditions at a specific altitude and atmospheric temperature under the maximum conditions of rotorshaft rotational speed and gas temperature approved for the normal takeoff, and limited in continuous use to the period of time shown in the approved engine specification.

Takeoff Weight

The weight of an aircraft just before beginning the takeoff roll. It is the ramp weight less the weight of the fuel burned during start and taxi.

Tandem wing configuration

A configuration having two wings of similar span, mounted in tandem.

Tangent Point (TP)

The point on the VOR/DME RNAV route centerline from which a line perpendicular to the route centerline would pass through the reference facility.

Tare Weight

The weight of any chocks or devices that are used to hold an aircraft on the scales when it is weighed. The tare weight must be subtracted from the scale reading to get the net weight of the aircraft.

Target

In radar, any of the many types of objects detected by radar.

Target

The indication shown on an analog display resulting from a primary radar return or a radar beacon reply.

Target Reverser

A thrust reverser in a jet engine in which clamshell doors swivel from the stowed position at the engine tailpipe to block all of the outflow and redirect some component of the thrust forward.

Tarmac Delay

The holding of an aircraft on the ground either before departure or after landing with no opportunity for its passengers to deplane.

TAS

True Air Speed

TAS

True Airspeed.

Task

Knowledge area, flight procedure, or maneuver within an area of operation in a practical test standard.

TAWS

Terrain Awareness and Warning System.

TAWS

Terrain Awareness and Warning System.

Taxi

The movement of an airplane under its own power on the surface of an airport (14 CFR Section 135.100 [Note]). Also, it describes the surface movement of helicopters equipped with wheels.

Taxi Patterns

Patterns established to illustrate the desired flow of ground traffic for the different runways or airport areas available for use.

Taxiway Lights

Omnidirectional lights that outline the edges of the taxiway and are blue in color.

Taxiway lights

Omnidirectional lights that outline the edges of the taxiway and are blue in color.

Taxiway Turnoff Lights

Flush lights which emit a steady green color.

Taxiway turnoff lights

Lights that are flush with the runway which emit a steady green color.

Taxonomy of educational objectives

A systematic classification scheme for sorting learning outcomes into three broad categories (cognitive, affective, and psychomotor) and ranking the desired outcomes in a developmental hierarchy from least complex to most complex.

TCAS

Traffic Alert Collision Avoidance System.

TCAS

A Traffic Alert and Collision Avoidance System.

TCAS I

A TCAS that utilizes interrogations of, and replies from, airborne radar beacon transponders and provides traffic advisories to the pilot.

TCAS II

A TCAS that utilizes interrogations of, and replies from airborne radar beacon transponders and provides traffic advisories and resolution advisories in the vertical plane.

TCAS III

A TCAS that utilizes interrogation of, and replies from, airborne radar beacon transponders and provides traffic advisories and resolution advisories in the vertical and horizontal planes to the pilot.

TCH

Threshold Crossing Height.

TD

Time Difference

TDLS

Terminal Data Link System

TDLS

Tower Data Link System

TDWR

Terminal Doppler Weather Radar

TDZ

Touchdown Zone

TDZE

Touchdown Zone Elevation.

TDZL

Touchdown Zone Lights.

TDZL

Touchdown Zone Lights

Teaching

Instructing, training, or imparting knowledge or skill; the profession of someone who teaches.

Teaching lecture

An oral presentation that is directed toward desired learning outcomes. Some student participation is allowed.

TEC

Tower En Route Control.

Technique

The manner in which procedures are executed.

Technique

The manner in which procedures are executed.

Telephone information briefing service (TIBS)

Telephone recording of area and/or route meteorological briefings, airspace procedures, and special aviation-oriented announcements. Discontinued in the CONUS in September 2018 and in Alaska on Jan 1, 2020.

Telephone Information Briefing Service (TIBS)

A telephone recording of meteorological and/or aeronautical information obtained by calling an FSS. Discontinued in the CONUS in September 2018 and in Alaska on Jan 1, 2020.

Telling-and-doing technique

A technique of flight instruction that consists of the instructor first telling the student about a new procedure and then demonstrating it. This is followed by the student telling and the instructor doing. Third, the student explains the new procedure while doing it. Last, the instructor evaluates while the student performs the procedure.

TEMAC

Trailing Edge of the Mean Aerodynamic Chord.

Temperature

In general, the degree of hotness or coldness as measured on some definite temperature scale by means of any of various types of thermometers.

Temperature inversion

Inversion. An increase in temperature with height-a reversal of the normal decrease with height in the troposphere; may also be applied to other meteorological properties.

Temporary Ballast

Weights that can be carried in a cargo compartment of an aircraft to move the location of CG for a specific flight condition. Temporary ballast must be removed when the aircraft is weighed.

Temporary flight restriction (TFR)

Restriction to flight imposed in order to:
1. Protect persons and property in the air or on the surface from an existing or imminent flight associated hazard;
2. Provide a safe environment for the operation of disaster relief aircraft;
3. Prevent an unsafe congestion of sightseeing aircraft above an incident;
4. Protect the President, Vice President, or other public figures; and,
5. Provide a safe environment for space agency operations.
Pilots are expected to check appropriate NOTAMs during flight planning when conducting flight in an area where a temporary flight restriction is in effect.

Temporary flight restriction (TFR)

Tension

Maintaining an excessively strong grip on the control column, usually resulting in an overcontrolled situation.

Tension

Maintaining an excessively strong grip on the control column, usually resulting in an overcontrolled situation.

Terminal aerodrome forecast (TAF)

A report established for the 5 statute mile radius around an airport. Utilizes the same descriptors and abbreviations as the METAR report.

Terminal Area

A general term used to describe airspace in which approach control service or airport traffic control service is provided.

Terminal Arrival Area (TAA)

The TAA is controlled airspace established in conjunction with the Standard or Modified T and I RNAV approach configurations. In the standard TAA, there are three areas: straight-in, left base, and right base. The arc boundaries of the three areas of the TAA are published portions of the approach and allow aircraft to transition from the en route structure direct to the nearest IAF (Initial Approach Fix). TAAs will also eliminate or reduce feeder routes, departure extensions, and procedure turns or course reversal.

Terminal Data Link System (TDLS)

A system that provides Digital Automatic Terminal Information Service (D-ATIS) both on a specified radio frequency and also, for subscribers, in a text message via data link to the cockpit or to a gate printer. TDLS also provides Pre-departure Clearances (PDC), at selected airports, to subscribers, through a service provider, in text to the cockpit or to a gate printer. In addition, TDLS will emulate the Flight Data Input/Output (FDIO) information within the control tower.

Terminal instrument approach procedure (TERP)

Prescribes standardized methods for use in designing instrument flight procedures.

Terminal Radar Service Area

Airspace surrounding designated airports wherein ATC provides radar vectoring, sequencing, and separation on a full-time basis for all IFR and participating VFR aircraft. The AIM contains an explanation of TRSA. TRSAs are depicted on VFR aeronautical charts. Pilot participation is urged but is not mandatory.

Terminal VFR Radar Service

A national program instituted to extend the terminal radar services provided instrument flight rules (IFR) aircraft to visual flight rules (VFR) aircraft. The program is divided into four types service referred to as basic radar service, terminal radar service area (TRSA) service, Class B service and Class C service. The type of service provided at a particular location is contained in the Airport/Facility Directory.

Terminal-Very High Frequency Omnidirectional Range Station

A very high frequency terminal omnirange station located on or near an airport and used as an approach aid.

TERP

Terminal Instrument Approach Procedure.

TERPS

U.S. Standard For Terminal Instrument Procedures

Terrain Awareness and Warning System (TAWS)

A timed-based system that provides information concerning potential hazards with fixed objects by using GPS positioning and a database of terrain and obstructions to provide true predictability of the upcoming terrain and obstacles.

Terrain awareness and warning system (TAWS)

Terrain/Obstruction Alert

Terrestrial radiation

The total infrared radiation emitted by the Earth and its atmosphere.

Test

A set of questions, problems, or exercises for determining whether a person has a particular knowledge or skill.

Test item

A question, problem, or exercise that measures a single objective and requires a single response.

Tetrahedron

A large, triangular-shaped, kite-like object installed near the runway. Tetrahedrons are mounted on a pivot and are free to swing with the wind to show the pilot the direction of the wind as an aid in takeoffs and landings.

TFC

Traffic

TFM

Traffic Flow Management

TFR

Temporary Flight Restriction.

TFR

Temporary Flight Restriction.

That Is Correct

The understanding you have is right.

Theodolite

An optical instrument which, in meteorology, is used principally to observe the motion of a pilot balloon.

Thermograph

A continuous-recording thermometer.

Thermometer

An instrument for measuring temperature.

Thermosphere

The last layer of the atmosphere that begins above the mesosphere and gradually fades away into space.

THL

Takeoff Hold Lights

Three-Hour Tarmac Rule

Rule that relates to Department of Transportation (DOT) requirements placed on airlines when tarmac delays are anticipated to reach 3 hours.

Threshold

The beginning of the part of the runway usable for landing.

Threshold

The beginning of that portion of the runway usable for landing.

Threshold crossing height (TCH)

The theoretical height above the runway threshold at which the aircrafts glide slope antenna would be if the aircraft maintains the trajectory established by the mean ILS glide slope or MLS glide path.

Threshold Lights

Fixed green lights arranged symmetrically left and right of the runway centerline, identifying the runway threshold.

Throttle

The valve in a carburetor or fuel control unit that determines the amount of fuel-air mixture that is fed to the engine.

Thrust

The force which imparts a change in the velocity of a mass. This force is measured in pounds but has no element of time or rate. The term, thrust required, is generally associated with jet engines. A forward force which propels the airplane through the air.

Thrust (aerodynamic force)

The forward aerodynamic force produced by a propeller, fan, or turbojet engine as it forces a mass of air to the rear, behind the aircraft.

Thrust (aerodynamic force)

The forward aerodynamic force produced by a propeller, fan, or turbojet engine as it forces a mass of air to the rear, behind the aircraft.

Thrust Line

An imaginary line passing through the center of the propeller hub, perpendicular to the plane of the propeller rotation.

Thrust line

An imaginary line passing through the center of the propeller hub, perpendicular to the plane of the propeller rotation.

Thrust Reversers

Devices which redirect the flow of jet exhaust to reverse the direction of thrust.

Thunderstorm

In general, a local storm invariably produced by a cumulonimbus cloud, and always accompanied by lightning and thunder.

TIBS

Telephone Information Briefing Service - Discontinued in the CONUS in September 2018 and in Alaska on Jan 1, 2020.

Time and opportunity

A perception factor in which learning something is dependent on the student having the time to sense and relate current experiences in context with previous events.

Time and speed table

A table depicted on an instrument approach procedure chart that identifies the distance from the FAF to the MAP, and provides the time required to transit that distance based on various groundspeeds.

Time in service

With respect to maintenance time records, the time from the moment an aircraft leaves the surface of the earth until it touches it at the next point of landing.

Timed turn

A turn in which the clock and the turn coordinator are used to change heading a definite number of degrees in a given time.

Timed turn

A turn in which the clock and the turn coordinator are used to change heading a definite number of degrees in a given time.

Timing

The application of muscular coordination at the proper instant to make flight, and all maneuvers incident thereto, a constant smooth process.

Tire Cord

Woven metal wire laminated into the tire to provide extra strength. A tire showing any cord must be replaced prior to any further flight.

TIS

Traffic Information Service.

TIS

Traffic Information Service

TIS-B

Traffic Information Service-Broadcast of Touchdown and Lift-Off Area

TLS

Transponder Landing System

TM

Traffic Management

TMA

Traffic Management Advisor

TOD

Top Of Descent

TODA

Takeoff Distance Available

TOGA

Take-Off/Go Around

Top of Climb (TOC)

An identifiable waypoint representing the point at which cruise altitude is first reached. TOC is calculated based on your current aircraft altitude, climb speed, and cruise altitude. There can only be one TOC waypoint at a time.

Top of Descent (TOD)

Generally utilized in flight management systems, top of descent is an identifiable waypoint representing the point at which descent is first initiated from cruise altitude. TOD is generally calculated using the destination elevation (if available) and the descent speed schedule.

TORA

Takeoff Runway Available

Torching

The burning of fuel at the end of an exhaust pipe or stack of a reciprocating aircraft engine, the result of an excessive richness in the fuel air mixture.

Tornado (sometimes called cyclone, twister)

A violently rotating column of air, pendant from a cumulonimbus cloud, and nearly always observable as “funnel-shaped.” It is the most destructive of all small-scale atmospheric phenomena.

Torque

1. A resistance to turning or twisting.
2. Forces that produce a twisting or rotating motion.
3. In an airplane, the tendency of the aircraft to turn (roll) in the opposite direction of rotation of the engine and propeller.

Torque

(1) A resistance to turning or twisting.
(2) Forces that produce a twisting or rotating motion.
(3) In an airplane, the tendency of the aircraft to turn (roll) in the opposite direction of rotation of the engine and propeller.
(4) In helicopters with a single, main rotor system, the tendency of the helicopter to turn in the opposite direction of the main rotor rotation.

Torque Meter

An indicator used on some large reciprocating engines or on turboprop engines to indicate the amount of torque the engine is producing.

Torque Sensor

See Torque Meter.

Torquemeter

An instrument used with some of the larger reciprocating engines and turboprop or turboshaft engines to measure the reaction between the propeller reduction gears and the engine case.

Total Drag

The sum of the parasite and induced drag.

Total drag

The sum of the parasite drag and induced drag.

Touch-And-Go

An operation by an aircraft that lands and departs on a runway without stopping or exiting the runway.

Touch-And-Go Landing

Touch-And-Go.

Touchdown

A. The point at which an aircraft first makes contact with the landing surface.
B. Concerning a precision radar approach (PAR), it is the point where the glide path intercepts the landing surface.

Touchdown and Lift-Off Area (TLOF)

The TLOF is a load bearing, usually paved area at a heliport where the helicopter is permitted to land. The TLOF can be located at ground or rooftop level, or on an elevated structure. The TLOF is normally centered in the FATO.

Touchdown RVR

The RVR visibility readout values obtained from sensors serving the runway touchdown zone.

Touchdown Zone

The first 3,000 feet of the runway beginning at the threshold. The area is used for determination of Touchdown Zone Elevation in the development of straight-in landing minimums for instrument approaches.

Touchdown Zone Elevation

The highest elevation in the first 3,000 feet of the landing surface. TDZE is indicated on the instrument approach procedure chart when straight-in landing minimums are authorized.

Touchdown Zone Lighting

Two rows of transverse light bars located symmetrically about the runway centerline normally at 100 foot intervals. The basic system extends 3,000 feet along the runway.

Touchdown Zone Lights

Two rows of transverse light bars disposed symmetrically about the runway centerline in the runway touchdown zone.

Tower

A terminal facility that uses air/ground communications, visual signaling, and other devices to provide ATC services to aircraft operating in the vicinity of an airport or on the movement area. Authorizes aircraft to land or takeoff at the airport controlled by the tower or to transit the Class D airspace area regardless of flight plan or weather conditions (IFR or VFR). A tower may also provide approach control services (radar or nonradar).

Tower En Route Control (TEC)

The control of IFR en route traffic within delegated airspace between two or more adjacent approach control facilities. This service is designed to expedite air traffic and reduces air traffic control and pilot communication requirements.

Tower To Tower

Tower En Route Control Service.

Tower visibility

Prevailing VIsibility determined from the control tower.

Towering cumulus

A rapidly growing cumulus in which height exceeds width.

TPP

United States Terminal Procedures Publication.

TRACAB

A new type of air traffic facility that consists of a radar approach control facility located in the tower cab of the primary airport, as opposed to a separate room.

Trace Icing

Ice becomes perceptible. Rate of accumulation is slightly greater than the rate of sublimation. Deicing/anti-icing equipment is not utilized unless encountered for an extended period of time (over 1 hour).

Trace Icing

Ice becomes noticeable. The rate of accumulation is slightly greater than the rate of sublimation. A representative accretion rate for reference purposes is less than 1⁄4 inch (6 mm) per hour on the outer wing. Deicing/anti-icing equipment is not utilized unless encountered for an extended period of time (over 1 hour).

Track

The actual path made over the ground in flight.

Track

The actual path made over the ground in flight.

Tracking

Flying a heading that will maintain the desired track to or from the station regardless of crosswind conditions.

Tracking

Flying a heading that will maintain the desired track to or from the station regardless of crosswind conditions.

TRACON

Terminal Radar Approach Control

TRACON

Terminal Radar Control Facility. A terminal ATC facility that uses radar and nonradar capabilities to provide approach control services to aircraft arriving, departing, or transiting airspace controlled by the facility.

Trade winds

Prevailing, almost continuous winds blowing with an easterly component from the subtropical high pressure belts toward the intertropical convergence cone; northeast in the Northern Hemisphere, southeast in the Southern Hemisphere.

Traditional assessment

Written testing, such as multiple choice, matching, true/false, or fill-in-the-blank.

Traffic

A. A term used by a controller to transfer radar identification of an aircraft to another controller for the purpose of coordinating separation action. Traffic is normally issued:
1. In response to a handoff or point out,
2. In anticipation of a handoff or point out, or
3. In conjunction with a request for control of an aircraft.
B. A term used by ATC to refer to one or more aircraft.

Traffic Advisories

Advisories issued to alert pilots to other known or observed air traffic which may be in such proximity to the position or intended route of flight of their aircraft to warrant their attention. Such advisories may be based on: a. Visual observation. b. Observation of radar identified and nonidentified aircraft targets on an ATC radar display, or c. Verbal reports from pilots or other facilities. Note 1: The word “traffic” followed by additional information, if known, is used to provide such advisories; e.g., “Traffic, 2 o’clock, one zero miles, southbound, eight thousand.” Note 2: Traffic advisory service will be provided to the extent possible depending on higher priority duties of the controller or other limitations; e.g., radar limitations, volume of traffic, frequency congestion, or controller workload. Radar/ nonradar traffic advisories do not relieve the pilot of his/her responsibility to see and avoid other aircraft. Pilots are cautioned that there are many times when the controller is not able to give traffic advisories concerning all traffic in the aircraft’s proximity; in other words, when a pilot requests or is receiving traffic advisories, he/she should not assume that all traffic will be issued.

Traffic Alert

(aircraft call sign), TURN (left/right) IMMEDIATELY, (climb/descend) AND MAINTAIN (altitude).

Traffic Alert And Collision Avoidance System

An airborne collision avoidance system based on radar beacon signals which operates independent of ground-based equipment. TCAS-I generates traffic advisories only. TCAS-II generates traffic advisories, and resolution (collision avoidance) advisories in the vertical plane.

Traffic Alert Collision Avoidance System (TCAS).

An airborne system developed by the FAA that operates independently from the ground-based Air Traffic Control system. Designed to increase flight deck awareness of proximate aircraft and to serve as a last line of defense for the prevention of mid-air collisions.

Traffic In Sight

Used by pilots to inform a controller that previously issued traffic is in sight.

Traffic Information

Traffic Advisories.

Traffic information service (TIS)

A ground-based service providing information to the flight deck via data link using the S-mode transponder and altitude encoder to improve the safety and efficiency of see and avoid flight through an automatic display that informs the pilot of nearby traffic.

Traffic information service (TIS)

A ground-based service providing information to the flight deck via data link using the S-mode transponder and altitude encoder to improve the safety and efficiency of “see and avoid” flight through an automatic display that informs the pilot of nearby traffic.

Traffic Information Service-Broadcast (TIS-B)

The broadcast of ATC derived traffic information to ADS-B equipped (1090ES or UAT) aircraft. The source of this traffic information is derived from ground-based air traffic surveillance sensors, typically from radar targets. TIS-B service will be available throughout the NAS where there are both adequate surveillance coverage (radar) and adequate broadcast coverage from ADS-B ground stations. Loss of TIS-B will occur when an aircraft enters an area not covered by the GBT network. If this occurs in an area with adequate surveillance coverage (radar), nearby aircraft that remain within the adequate broadcast coverage (ADS-B) area will view the first aircraft. TIS-B may continue when an aircraft enters an area with inadequate surveillance coverage (radar); nearby aircraft that remain within the adequate broadcast coverage (ADS-B) area will not view the first aircraft.

Traffic Management Advisor (TMA)

A software suite that helps air traffic controllers to sequence arriving air traffic.

Traffic Management Program Alert

A term used in a Notice to Airmen (NOTAM) issued in conjunction with a special traffic management program to alert pilots to the existence of the program and to refer them to either the Notices to Airmen publication or a special traffic management program advisory message for program details. The contraction TMPA is used in NOTAM text.

Traffic No Factor

Indicates that the traffic described in a previously issued traffic advisory is no factor.

Traffic No Longer Observed

Indicates that the traffic described in a previously issued traffic advisory is no longer depicted on radar, but may still be a factor.

Traffic Pattern

The traffic flow that is prescribed for aircraft landing at, taxiing on, or taking off from an airport. The components of a typical traffic pattern are upwind leg, crosswind leg, downwind leg, base leg, and final approach.

Trailing Edge

The portion of the airfoil where the airflow over the upper surface rejoins the lower surface airflow.

Trailing edge

The portion of the airfoil where the airflow over the upper surface rejoins the lower surface airflow.

Training course outline

Within a curriculum, describes the content of a particular course by statement of objectives, descriptions of teaching aids, definition of evaluation criteria, and indication of desired outcome.

Training media

Any physical means that communicates an instructional message to students.

Training syllabus

A step by- step, building block progression of learning with provisions for regular review and evaluations at prescribed stages of learning. The syllabus defines the unit of training, states by objective what the student is expected to accomplish during the unit of training, shows an organized plan for instruction, and dictates the evaluation process for either the unit or stages of learning.

Transcribed Weather Broadcast (TWEB)

Meteorological and aeronautical data recorded on tapes and broadcast over selected NAVAIDs. Generally, the broadcast contains route-oriented data with specially prepared NWS forecasts, inflight advisories, and winds aloft. It also includes selected current information such as weather reports (METAR/SPECI), NOTAMs, and special notices. Discontinued in the CONUS in September 2018 and in Alaska on Jan 1, 2020.

Transcribed Weather Broadcast (TWEB)

Transfer Of Control

That action whereby the responsibility for the separation of an aircraft is transferred from one controller to another.

Transfer of learning

The ability to apply knowledge or procedures learned in one context to new contexts.

Transition

A published procedure (DP Transition) used to connect the basic DP to one of several en route airways/jet routes, or a published procedure (STAR Transition) used to connect one of several en route airways/jet routes to the basic STAR.

Transition

The general term that describes the change from one phase of flight or flight condition to another; e.g., transition from en route flight to the approach or transition from instrument flight to visual flight.

Transition Altitude (QNH)

The altitude in the vicinity of an airport at or below which the vertical position of an aircraft is controlled by reference to altitudes (MSL).

Transition Height (QFE)

Transition height is the height in the vicinity of an airport at or below which the vertical position of an aircraft is expressed in height above the airport reference datum.

Transition Layer

Transition layer is the airspace between the transition altitude and the transition level. Aircraft descending through the transition layer will set altimeters to local station pressure, while departing aircraft climbing through the transition layer will be using standard altimeter setting (QNE) of 29.92 inches of Mercury, 1013.2 millibars, or 1013.2 hectopascals.

Transition Level (QNE)

The lowest flight level available for use above the transition altitude.

Transition Liner

The portion of the combustor that directs the gases into the turbine plenum.

Transition training

An instructional program designed to familiarize and qualify a pilot to fly types of aircraft not previously flown, such as tail wheel aircraft, high performance aircraft, and aircraft capable of flying at high altitudes.

Transition Waypoint

The waypoint that defines the beginning of a runway or en route transition on an RNAV SID or STAR.

Transmissometer

An instrument system which shows the transmissivity of light through the atmosphere. Transmissivity may be translated either automatically or manually into visibility and/or runway visual range.

Transmitting In The Blind

Transonic

At the speed of sound.

Transponder

The airborne portion of the secondary surveillance radar system. The transponder emits a reply when queried by a radar facility.

Transponder

The airborne portion of the ATC radar beacon system.

Transponder

The airborne radar beacon receiver/transmitter portion of the Air Traffic Control Radar Beacon System (ATCRBS) which automatically receives radio signals from interrogators on the ground, and selectively replies with a specific reply pulse or pulse group only to those interrogations being received on the mode to which it is set to respond.

Transponder code

One of 4,096 four-digit discrete codes ATC assigns to distinguish between aircraft.

Transponder code

One of 4,096 four-digit discrete codes ATC assigns to distinguish between aircraft.

Transponder Observed

Phraseology used to inform a VFR pilot the aircraft’s assigned beacon code and position have been observed. Specifically, this term conveys to a VFR pilot the transponder reply has been observed and its position correlated for transit through the designated area.

Trend

Immediate indication of the direction of aircraft movement, as shown on instruments.

Trend

Immediate indication of the direction of aircraft movement, as shown on instruments.

Tricycle Gear

Landing gear employing a third wheel located on the nose of the aircraft.

Tricycle gear

Landing gear employing a third wheel located on the nose of the aircraft.

Trim

Adjusting the aerodynamic forces on the control surfaces so that the aircraft maintains the set attitude without any control input.

Trim

To adjust the aerodynamic forces on the control surfaces so that the aircraft maintains the set attitude without any control input.

Trim Tab

A small auxiliary hinged portion of a movable control surface that can be adjusted during flight to a position resulting in a balance of control forces.

Trim tab

A small auxiliary hinged portion of a movable control surface that can be adjusted during flight to a position resulting in a balance of control forces.

Triple Spool Engine

Usually a turbofan engine design where the fan is the N1 compressor, followed by the N2 intermediate compressor, and the N3 high pressure compressor, all of which rotate on separate shafts at different speeds.

Tropical air

An air mass with characteristics developed over low latitudes. Maritime tropical air (mT), the principal type, is produced over the tropical and subtropical seas; very warm and humid. Continental tropical (cT) is produced over subtropical arid regions and is hot and very dry. Compare polar air.

Tropical cyclone

A general term for a cyclone that originates over tropical oceans. By international agreement, tropical cyclones have been classified according to their intensity, as follows: (1) tropical depression-winds up to 34 knots (64 km/h); (2) tropical storm-winds of 35 to 64 knots (65 to 119 km/h); (3) hurricane or typhoon-winds of 65 knots or higher (120 km/h).

Tropical depression

A cyclone that originates over tropical oceans. A tropical depression winds up to 34 knots (64 km/h).

Tropical storm

A cyclone that originates over tropical oceans. A tropical storm has winds of 35 to 64 knots (65 to 119 km/h).

Tropopause

The transition zone between the troposphere and stratosphere, usually characterized by an abrupt change of lapse rate.

Troposphere

That portion of the atmosphere from the earth’s surface to the tropopause; that is, the lowest 10 to 20 kilometers of the atmosphere. The troposphere is characterized by decreasing temperature with height. and by appreciable water vapor.

Trough (also called trough line)

In meteorology, an elongated area of relatively low atmospheric pressure; usually associated with and most clearly identified as an area of maximum cyclonic curvature of the wind flow (isobars, contours, or streamlines); compare with ridge.

TRSA

Terminal Radar Service Area

TRSA Service

This service provides, in addition to basic radar service, sequencing of all IFR and participating VFR aircraft to the primary airport and separation between all participating VFR aircraft. The purpose of this service is to provide separation between all participating VFR aircraft and all IFR aircraft operating within the area defined as a TRSA.

True airspeed

Actual airspeed, determined by applying a correction for pressure altitude and temperature to the CAS.

True airspeed

Actual airspeed, determined by applying a correction for pressure altitude and temperature to the CAS.

True Airspeed (TAS)

Calibrated airspeed corrected for altitude and nonstandard temperature. Because air density decreases with an increase in altitude, an airplane has to be flown faster at higher altitudes to cause the same pressure difference between pitot impact pressure and static pressure. Therefore, for a given calibrated airspeed, true airspeed increases as altitude increases; or for a given true airspeed, calibrated airspeed decreases as altitude increases.

True Altitude

The vertical distance of the airplane above sea level—the actual altitude. It is often expressed as feet above mean sea level (MSL). Airport, terrain, and obstacle elevations on aeronautical charts are true altitudes.

True altitude

The exact distance above mean sea level.

True Course

A predetermined desired course direction to be followed (measured in degrees from true north).

True wind direction

The direction, with respect to true north, from which the wind is blowing.

Truss

A fuselage design made up of supporting structural members that resist deformation by applied loads. The truss-type fuselage is constructed of steel or aluminum tubing. Strength and rigidity is achieved by welding the tubing together into a series of triangular shapes, called trusses.

TSA

Transportation Security Administration (TSA) protects the nation’s transportation systems to ensure freedom of movement for people and commerce.

TSD

Traffic Situation Display. A tool used by Traffic Management Specialists to monitor the position of air traffic and to determine the traffic demand on airports and sectors.

TSE

Total Navigation System Error

TSO

Technical Standard Order

TSO

Technical Standard Order.

TSO

Technical Standard Order

TSTMS

Thunderstorms

Turbine Blades

The portion of the turbine assembly that absorbs the energy of the expanding gases and converts it into rotational energy.

Turbine discharge pressure

The total pressure at the discharge of the low-pressure turbine in a dual-turbine axial-flow engine.

Turbine engine

An aircraft engine which consists of an air compressor, a combustion section, and a turbine. Thrust is produced by increasing the velocity of the air flowing through the engine.

Turbine Outlet Temperature (TOT)

The temperature of the gases as they exit the turbine section.

Turbine Plenum

The portion of the combustor where the gases are collected to be evenly distributed to the turbine blades.

Turbine Rotors

The portion of the turbine assembly that mounts to the shaft and holds the turbine blades in place.

Turbine Section

The section of the engine that converts high pressure high temperature gas into rotational energy.

Turbocharger

An air compressor driven by exhaust gases, which increases the pressure of the air going into the engine through the carburetor or fuel injection system.

Turbofan Engine

A turbojet engine in which additional propulsive thrust is gained by extending a portion of the compressor or turbine blades outside the inner engine case. The extended blades propel bypass air along the engine axis but between the inner and outer casing. The air is not combusted but does provide additional thrust.

Turbojet Aircraft

An aircraft having a jet engine in which the energy of the jet operates a turbine which in turn operates the air compressor.

Turbojet Engine

A jet engine incorporating a turbine-driven air compressor to take in and compress air for the combustion of fuel, the gases of combustion being used both to rotate the turbine and create a thrust producing jet.

Turboprop Aircraft

An aircraft having a jet engine in which the energy of the jet operates a turbine which drives the propeller.

Turboprop Engine

A turbine engine that drives a propeller through a reduction gearing arrangement. Most of the energy in the exhaust gases is converted into torque, rather than its acceleration being used to propel the aircraft.

Turboshaft engine

A gas turbine engine that delivers power through a shaft to operate something other than a propeller.

Turbulence

An occurrence in which a flow of fluid is unsteady.

Turbulence

In meteorology, any irregular or disturbed flow in the atmosphere.

Turn Anticipation

The capability of RNAV systems to determine the point along a course, prior to a turn WP, where a turn should be initiated to provide a smooth path to intercept the succeeding course, and to enunciate the information to the pilot.

Turn Anticipation

(maneuver anticipation).

Turn Coordinator

A rate gyro that senses both roll and yaw due to the gimbal being canted. Has largely replaced the turn-and-slip indicator in modern aircraft.

Turn coordinator

A rate gyro that senses both roll and yaw due to the gimbal being canted. Has largely replaced the turn-and-slip indicator in modern aircraft.

Turn WP [Turning Point]

A WP which identifies a change from one course to another.

Turn-And-Slip Indicator

A flight instrument consisting of a rate gyro to indicate the rate of yaw and a curved glass inclinometer to indicate the relationship between gravity and centrifugal force. The turn-and-slip indicator indicates the relationship between angle of bank and rate of yaw. Also called a turn-and-bank indicator.

Turn-and-slip indicator

Turning Error

One of the errors inherent in a magnetic compass caused by the dip compensating weight. It shows up only on turns to or from northerly headings in the Northern Hemisphere and southerly headings in the Southern Hemisphere. Turning error causes the compass to lead turns to the north or south and lag turns away from the north or south.

TVOR

Very High Frequency Terminal Omnirange Station.

TWEB

Transcribed Weather Broadcast - Discontinued in the CONUS in September 2018 and in Alaska on Jan 1, 2020.

TWEB

Transcribed Weather Broadcast - Discontinued in the CONUS in September 2018 and in Alaska on Jan 1, 2020.

TWEB

Transcribed Weather Broadcast - Discontinued in the CONUS in September 2018 and in Alaska on Jan 1, 2020.

TWIB

Terminal Weather Information for Pilots System

Twilight

The intervals of incomplete darkness following sunset and preceding sunrise. The time at which evening twilight ends or morning twilight begins is determined by arbitrary convention, and several kinds of twilight have been defined and used; most commonly civil, nautical, and astronomical twilight.

Twister

In the United States, a colloquial term for tornado.

Two-Way Radio Communications Failure

Lost Communications.

Type

(1) As used with respect to the certification, ratings, privileges, and limitations of airmen, a specific make and basic model of aircraft, including modifications thereto that do not change its handling or flight characteristics. Examples include: DC–7, 1049, and F–27; and
(2) As used with respect to the certification of aircraft, those aircraft which are similar in design. Examples include: DC–7 and DC–7C; 1049G and 1049H; and F–27 and F–27F.
(3) As used with respect to the certification of aircraft engines, those engines which are similar in design. For example, JT8D and JT8D–7 are engines of the same type, and JT9D–3A and JT9D–7 are engines of the same type.

Type Certificate Data Sheets (TCDS)

The official specifications issued by the FAA for an aircraft, engine, or propeller.

Typhoon

A tropical cyclone in the Eastern Hemisphere with winds in excess of 65 knots (120 km/h).

U.S.

United States

UA

Unmanned Aircraft

UAS

Unmanned Aircraft System

UAT

Universal Access Transceiver

UAV

Unmanned Aerial Vehicle

UFO

Unidentified Flying Object

UHF

Ultra-High Frequency.

UHF

Ultrahigh Frequency

Ultimate load factor

In stress analysis, the load that causes physical breakdown in an aircraft or aircraft component during a strength test, or the load that according to computations, should cause such a breakdown.

Ultrahigh Frequency

The frequency band between 300 and 3,000 MHz. The bank of radio frequencies used for military air/ground voice communications. In some instances this may go as low as 225 MHz and still be referred to as UHF.

Ultralight Vehicle

An aeronautical vehicle operated for sport or recreational purposes which does not require FAA registration, an airworthiness certificate, nor pilot certification. They are primarily single occupant vehicles, although some two-place vehicles are authorized for training purposes. Operation of an ultralight vehicle in certain airspace requires authorization from ATC.

Unable

Indicates inability to comply with a specific instruction, request, or clearance.

Uncaging

Unlocking the gimbals of a gyroscopic instrument, making it susceptible to damage by abrupt flight maneuvers or rough handling.

Uncaging

Unlocking the gimbals of a gyroscopic instrument, making it susceptible to damage by abrupt flight maneuvers or rough handling.

Uncontrolled airspace

Class G airspace that has not been designated as Class A, B, C, D, or E. It is airspace in which air traffic control has no authority or responsibility to control air traffic; however, pilots should remember there are VFR minimums which apply to this airspace.

Under The Hood

Indicates that the pilot is using a hood to restrict visibility outside the cockpit while simulating instrument flight. An appropriately rated pilot is required in the other control seat while this operation is being conducted.

Undercast

A cloud layer of ten-tenths (1.0) coverage (to the nearest tenth) as viewed from an observation point above the layer.

Underpower

Using less power than required for the purpose of achieving a faster rate of airspeed change.

Underpower

Using less power than required for the purpose of achieving a faster rate of airspeed change.

Understanding

A basic level of learning at which a student comprehends or grasps the nature or meaning of something.

Undrainable Oil

Oil that does not drain from an engine lubricating system when the aircraft is in the normal ground attitude and the drain valve is left open. The weight of the undrainable oil is part of the empty weight of the aircraft.

Unfeathering Accumulator

Tanks that hold oil under pressure which can be used to unfeather a propeller.

Unicom

A nongovernment communication facility which may provide airport information at certain airports. Locations and frequencies of UNICOMs are shown on aeronautical charts and publications.

United States

In a geographical sense means (1) the States, the District of Columbia, Puerto Rico, and the possessions, including the territorial waters, and (2) the airspace of those areas.

United States air carrier

A citizen of the United States who undertakes directly by lease, or other arrangement, to engage in air transportation.

United States Terminal Procedures Publication (TPP)

Booklets published in regional format by the NACO that include DPs, STARs, IAPs, and other information pertinent to IFR flight.

Unlimited ceiling

A clear sky or a sky cover that does not meet the criteria for a ceiling.

Unpublished Route

A route for which no minimum altitude is published or charted for pilot use. It may include a direct route between NAVAIDs, a radial, a radar vector, or a final approach course beyond the segments of an instrument approach procedure.

Unreliable (GPS/WAAS)

An advisory to pilots indicating the expected level of service of the GPS and/or WAAS may not be available. Pilots must then determine the adequacy of the signal for desired use.

Unstable

Instability. A general term to indicate various states of the atmosphere in which spontaneous convection will occur when prescribed criteria are met; indicative of turbulence.

Unusable Fuel

Fuel that cannot be consumed by the engine. This fuel is considered part of the empty weight of the aircraft.

Unusual attitude

An unintentional, unanticipated, or extreme aircraft attitude.

Unusual attitude

An unintentional, unanticipated, or extreme aircraft attitude.

Updraft

A localized upward current of air.

Upper front

A front aloft not extending to the earth’s surface.

Upslope fog

Fog formed when air flows upward over rising terrain and is, consequently, adiabatically cooled to or below its initial dew point.

Upwind Leg

A flight path parallel to the landing runway in the direction of landing.

URET

User Request Evaluation Tool

Urgency

A condition of being concerned about safety and of requiring timely but not immediate assistance; a potential distress condition.

Usability

The functionality of tests.

Usable Fuel

(GAMA) Fuel available for flight planning.

Useful Load

The weight of the pilot, copilot, passengers, baggage, usable fuel, and drainable oil. It is the basic empty weight subtracted from the maximum allowable gross weight. This term applies to general aviation aircraft only.

Useful load

User Request Evaluation Tool (URET)

The URET helps provide enhanced, automated flight data management. URET is an automated tool provided at each radar position in selected en route facilities. It uses flight and radar data to determine present and future trajectories for all active and proposed aircraft flights. A graphic plan display depicts aircraft, traffic, and notification of predicted conflicts. Graphic routes for current plans and trial plans are displayed upon controller request. URET can generate a predicted conflict of two aircraft, or between aircraft and airspace.

User-defined Waypoint

User-defined waypoints typically are created by pilots for use in their own random RNAV direct navigation. They are newly established, unpublished airspace fixes that are designated geographic locations/positions that help provide positive course guidance for navigation and a means of checking progress on a flight. They may or may not be actually plotted by the pilot on enroute charts, but would normally be communicated to ATC in terms of bearing and distance or latitude/longitude. An example of user defined waypoints typically includes those derived from database-driven area navigation (RNAV) systems whereby latitude/longitude coordinate-based waypoints are generated by various means including keyboard input, and even electronic map mode functions used to establish waypoints with a cursor on the display. Another example is an offset phantom waypoint, which is a point in space formed by a bearing and distance from NAVAIDs such as VORs, VORTACs, and TACANs, using a variety of navigation systems.

User-defined waypoints

Waypoint location and other data which may be input by the user, this is the only GPS database information that may be altered (edited) by the user.

UTC

Coordinated Universal Time (abbreviated as UTC, and therefore often spelled out as Universal Time Coordinated and sometimes as Universal Coordinated Time) is the standard time common to every place in the world. Formerly and still widely called Greenwich Mean Time (GMT) and also World Time, UTC nominally reflects the mean solar time along the Earth´s prime meridian.

UTC

Coordinated Universal Time

Utility Category

An airplane that has a seating configuration, excluding pilot seats, of nine or less, a maximum certificated takeoff weight of 12,500 pounds or less, and intended for limited acrobatic operation.

Utility Category

A category of aircraft certificated under 14 CFR part 23 and CAR part 3 that permits limited acrobatic maneuvers but restricts the weight and the CG range.

UWS

Urgent Weather SIGMET

V-Bars

The flight director displays on the attitude indicator that provide control guidance to the pilot.

V-G Diagram

A chart that relates velocity to load factor. It is valid only for a specific weight, configuration, and altitude and shows the maximum amount of positive or negative lift the airplane is capable of generating at a given speed. Also shows the safe load factor limits and the load factor that the aircraft can sustain at various speeds.

V-Speeds

Designated speeds for a specific flight condition.

V-Tail

A design which utilizes two slanted tail surfaces to perform the same functions as the surfaces of a conventional elevator and rudder configuration. The fixed surfaces act as both horizontal and vertical stabilizers.

V1

The maximum speed in the takeoff at which the pilot must take the first action (e.g., apply brakes, reduce thrust, deploy speed brakes) to stop the airplane within the accelerate-stop distance. Also the minimum speed in the takeoff, following a failure of the critical engine at Vef, at which the pilot can continue the takeoff and achieve the required height above the takeoff surface within the takeoff distance.

V2

Takeoff Safety Speed.

Va

The design maneuvering speed. This is the “rough air” speed and the maximum speed for abrupt maneuvers. If during flight, rough air or severe turbulence is encountered, reduce the airspeed to maneuvering speed or less to minimize stress on the airplane structure. It is important to consider weight when referencing this speed. For example, VA may be 100 knots when an airplane is heavily loaded, but only 90 knots when the load is light.

Va

Design maneuvering speed.

Va

The design maneuvering speed. The maximum speed at which full, abrupt control movement can be used without overstressing the airframe.

Validity

The extent to which a test measures what it is supposed to measure.

Vapor lock

A problem that mostly affects gasoline-fuelled internal combustion engines. It occurs when the liquid fuel changes state from liquid to gas while still in the fuel delivery system. This disrupts the operation of the fuel pump, causing loss of feed pressure to the carburetor or fuel injection system, resulting in transient loss of power or complete stalling. Restarting the engine from this state may be difficult. The fuel can vaporise due to being heated by the engine, by the local climate or due to a lower boiling point at high altitude.

Vapor pressure

In meteorology, the pressure of water vapor in the atmosphere. Vapor pressure is that part of the total atmospheric pressure due to water vapor and is independent of the other atmospheric gases or vapors.

Vapor trail

Same as condensation trail—a cloud-like streamer frequently observed to form behind aircraft flying in clear, cold, humid air.

VAPS

Visual Approaches. An approach conducted under Instrument Flight Rules that authorizes the pilot to proceed visually and clear of clouds to the airport. Usually this will be used in conjunction with Visual Separation. When using Visual Separation, a pilot sees the other aircraft involved, and upon instructions from the controller, provides his own separation by maneuvering his aircraft as necessary to avoid it. Visual Separation requires less spacing between aircraft than radar separation allowing more aircraft to land in a given period of time.

VAR

Volcanic Activity Reporting

Variation

Compass error caused by the difference in the physical locations of the magnetic north pole and the geographic north pole.

Variation

Compass error caused by the difference in the physical locations of the magnetic north pole and the geographic north pole.

VASI

Visual Approach Slope Indicator.

VASI

Visual Approach Slope Indicator

Vb

Design speed for maximum gust intensity.

Vc

Design cruising speed.

VCOA

Visual Climb Over Airport

VCOA

Visual Climb Over the Airport

Vd

Design diving speed.

VDA

Vertical Descent Angle

Vdf / Mdf

Demonstrated flight diving speed.

VDP

Visual Descent Point.

Vector

A force vector is a graphic representation of a force and shows both the magnitude and direction of the force.

Vector

A force vector is a graphic representation of a force and shows both the magnitude and direction of the force.

Vectoring

Navigational guidance by assigning headings.

Vectoring

Navigational guidance by assigning headings.

Veering

Shifting of the wind in a clockwise direction with respect to either space or time; opposite of backing. Commonly used by meteorologists to refer to an anticyclonic shift (clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere).

Vef

The speed at which the critical engine is assumed to fail during takeoff.

Vei

Instrument flight never exceed speed, utilized instead of Vne for compliance with maximum limit speed requirements for instrument flight

Velocity

The speed or rate of movement in a certain direction.

Velocity

The speed or rate of movement in a certain direction.

Venturi tube

A specially shaped tube attached to the outside of an aircraft to produce suction to allow proper operation of gyro instruments.

Venturi tube

A specially shaped tube attached to the outside of an aircraft to produce suction to allow proper operation of gyro instruments.

Verify

Request confirmation of information; e.g., “verify assigned altitude.”

Verify Specific Direction Of Takeoff (Or Turns After Takeoff)

Used by ATC to ascertain an aircraft’s direction of takeoff and/or direction of turn after takeoff. It is normally used for IFR departures from an airport not having a control tower. When direct communication with the pilot is not possible, the request and information may be relayed through an FSS, dispatcher, or by other means.

Vertical Axis

An imaginary line passing vertically through the center of gravity of an aircraft. The vertical axis is called the z-axis or the yaw axis.

Vertical axis

An imaginary line passing vertically through the center of gravity of an aircraft. The vertical axis is called the z-axis or the yaw axis.

Vertical Card Compass

A magnetic compass that consists of an azimuth on a vertical card, resembling a heading indicator with a fixed miniature airplane to accurately present the heading of the aircraft. The design uses eddy current damping to minimize lead and lag during turns.

Vertical card compass

Vertical Navigation (VNAV)

Traditionally, the only way to get glidepath information during an approach was to use a ground-based NAVAID, but modern area navigation systems allow flight crews to display an internally generated descent path that allows a constant rate descent to minimums during approaches that would otherwise include multiple level-offs.

Vertical Separation

Separation established by assignment of different altitudes or flight levels.

Vertical speed indicator (VSI)

A rate-of-pressure change instrument that gives an indication of any deviation from a constant pressure level.

Vertical speed indicator (VSI)

A rate-of-pressure change instrument that gives an indication of any deviation from a constant pressure level.

Vertical Stability

Stability about an aircraft’s vertical axis. Also called yawing or directional stability.

Vertical stability

Stability about an aircraft’s vertical axis. Also called yawing or directional stability.

Vertical Takeoff And Landing Aircraft

Aircraft capable of vertical climbs and/or descents and of using very short runways or small areas for takeoff and landings. These aircraft include, but are not limited to, helicopters.

Vertical visibility

The distance one can see upward into a surface based obscuration; or the maximum height from which a pilot in flight can recognize the ground through a surface based obscuration.

Very High Frequency

The frequency band between 30 and 300 MHz. Portions of this band, 108 to 118 MHz, are used for certain NAVAIDs; 118 to 136 MHz are used for civil air/ground voice communications. Other frequencies in this band are used for purposes not related to air traffic control.

Very Low Frequency

The frequency band between 3 and 30 kHz.

Very-high frequency (VHF)

A band of radio frequencies falling between 30 and 300 MHz.

Very-high frequency (VHF)

A band of radio frequencies falling between 30 and 300 MHz.

Very-high frequency omnidirectional range (VOR)

Electronic navigation equipment in which the flight deck instrument identifies the radial or line from the VOR station, measured in degrees clockwise from magnetic north, along which the aircraft is located.

Very-high frequency omnidirectional range (VOR).

Vestibule

The central cavity of the bony labyrinth of the ear, or the parts of the membranous labyrinth that it contains.

Vf

Design flap speed.

Vfc / Mfc

Maximum Speed For Stability Characteristics.

Vfe

The maximum speed with the flaps extended. The upper limit of the white arc.

Vfo

The maximum speed that the flaps can be extended or retracted.

VFR

Visual Flight Rules.

VFR

Visual Flight Rules. Rules that govern the procedures for conducting flight under visual conditions. The term "VFR" is also used in the United States to indicate weather conditions that are equal to or greater than minimum VFR requirements. In addition, it is used by pilots and controllers to indicate type of flight plan.

VFR Aircraft

An aircraft conducting flight in accordance with visual flight rules.

VFR Conditions

Weather conditions equal to or better than the minimum for flight under visual flight rules. The term may be used as an ATC clearance/instruction only when: a. An IFR aircraft requests a climb/descent in VFR conditions. b. The clearance will result in noise abatement benefits where part of the IFR departure route does not conform to an FAA approved noise abatement route or altitude. c. A pilot has requested a practice instrument approach and is not on an IFR flight plan. Note: All pilots receiving this authorization must comply with the VFR visibility and distance from cloud criteria in 14 CFR Part 91. Use of the term does not relieve controllers of their responsibility to separate aircraft in Class B and Class C airspace or TRSAs as required by FAAO JO 7110.65. When used as an ATC clearance/instruction, the term may be abbreviated “VFR;” e.g., “MAINTAIN VFR,” “CLIMB/DESCEND VFR,” etc.

VFR Flight

VFR Aircraft.

VFR Military Training Routes

Routes used by the Department of Defense and associated Reserve and Air Guard units for the purpose of conducting low-altitude navigation and tactical training under VFR below 10,000 feet MSL at airspeeds in excess of 250 knots IAS.

VFR Not Recommended

An advisory provided by a flight service station to a pilot during a preflight or inflight weather briefing that flight under visual flight rules is not recommended. To be given when the current and/or forecast weather conditions are at or below VFR minimums. It does not abrogate the pilot’s authority to make his/her own decision.

VFR over the top

A VFR operation in which an aircraft operates in VFR conditions on top of an undercast.

VFR over-the-top

A VFR operation in which an aircraft operates in VFR conditions on top of an undercast.

VFR terminal area chart

At a scale of 1:250,000, a chart that depicts Class B airspace, which provides for the control or segregation of all the aircraft within the Class B airspace. The chart depicts topographic information and aeronautical information including visual and radio aids to navigation, airports, controlled airspace, restricted areas, obstructions, and related data.

VFR-On-Top

ATC authorization for an IFR aircraft to operate in VFR conditions at any appropriate VFR altitude (as specified in 14 CFR and as restricted by ATC). A pilot receiving this authorization must comply with the VFR visibility, distance from cloud criteria, and the minimum IFR altitudes specified in 14 CFR Part 91. The use of this term does not relieve controllers of their responsibility to separate aircraft in Class B and Class C airspace or TRSAs as required by FAAO JO 7110.65.

Vfto

Final Takeoff Speed.

VGSI

Visual Glide Slope Indicator

VGSI

Visual Glide Slope Indicator

Vh

Maximum speed in level flight with maximum continuous power.

VHF

Very High Frequency

VHF

Very High Frequency.

VHF Omnidirectional Range/Tactical Air Navigation

VORTAC.

Victor airways

Airways based on a centerline that extends from one VOR or VORTAC navigation aid or intersection, to another navigation aid (or through several navigation aids or intersections); used to establish a known route for en route procedures between terminal areas. Visual approach slope indicator (VASI). A visual aid of lights arranged to provide descent guidance information during the approach to the runway. A pilot on the correct glide slope will see red lights over white lights.

Victor airways

VIP

Video Integrator Processor

Virga

Water or ice particles falling from a cloud, usually in wisps or streaks, and evaporating before reaching the ground.

Virtual Reality (VR)

A form of computer-based technology that creates a sensory experience allowing a participant to believe and barely distinguish a virtual experience from a real one. VR uses graphics with animation systems, sounds, and images to reproduce electronic versions of real-life experience.

Visibility

The greatest distance one can see and identify prominent objects.

Visibility

The ability, as determined by atmospheric conditions and expressed in units of distance, to see and identify prominent unlighted objects by day and prominent lighted objects by night. Visibility is reported as statute miles, hundreds of feet or meters.

Visual Approach

An approach conducted on an instrument flight rules (IFR) flight plan which authorizes the pilot to proceed visually and clear of clouds to the airport. The pilot must, at all times, have either the airport or the preceding aircraft in sight. This approach must be authorized and under the control of the appropriate air traffic control facility. Reported weather at the airport must be ceiling at or above 1,000 feet and visibility of 3 miles or greater.

Visual Approach Slope Indicator (VASI)

The most common visual glidepath system in use. The VASI provides obstruction clearance within 10° of the extended runway centerline, and to 4 nautical miles (NM) from the runway threshold.

Visual approach slope indicator (VASI)

A visual aid of lights arranged to provide descent guidance information during the approach to the runway. A pilot on the correct glideslope will see red lights over white lights.

Visual Climb Over Airport (VCOA)

A departure option for an IFR aircraft, operating in visual meteorological conditions equal to or greater than the specified visibility and ceiling, to visually conduct climbing turns over the airport to the published “climb-to” altitude from which to proceed with the instrument portion of the departure. VCOA procedures are developed to avoid obstacles greater than 3 statute miles from the departure end of the runway as an alternative to complying with climb gradients greater than 200 feet per nautical mile. These procedures are published in the `Take-Off Minimums and (Obstacle) Departure Procedures’ section of the Terminal Procedures Publications.

Visual descent point (VDP)

A defined point on the final approach course of a nonprecision straight-in approach procedure from which normal descent from the MDA to the runway touchdown point may be commenced, provided the runway environment is clearly visible to the pilot.

Visual flight rules (VFR)

Flight rules adopted by the FAA governing aircraft flight using visual references. VFR operations specify the amount of ceiling and the visibility the pilot must have in order to operate according to these rules. When the weather conditions are such that the pilot can not operate according to VFR, he or she must use instrument flight rules (IFR).

Visual flight rules (VFR)

Visual Holding

The holding of aircraft at selected, prominent geographical fixes which can be easily recognized from the air.

Visual meteorological conditions (VMC)

Meteorological conditions expressed in terms of visibility, distance from cloud, and ceiling meeting or exceeding the minimums specified for VFR.

Visual meteorological conditions (VMC)

Meteorological conditions expressed in terms of visibility, distance from cloud, and ceiling meeting or exceeding the minimums specified for VFR.

Visual range

Runway visual range. An instrumentally derived horizontal distance a pilot should see down the runway from the approach end; based on either the sighting of high intensity runway lights or on the visual contrast of other objects, whichever yields the greatest visual range.

Visual Segment

Published Instrument Approach Procedure Visual Segment.

Visual Separation

A means employed by ATC to separate aircraft in terminal areas and en route airspace in the NAS. There are two ways to effect this separation: a. The tower controller sees the aircraft involved and issues instructions, as necessary, to ensure that the aircraft avoid each other. b. A pilot sees the other aircraft involved and upon instructions from the controller provides his/her own separation by maneuvering his/her aircraft as necessary to avoid it. This may involve following another aircraft or keeping it in sight until it is no longer a factor.

Vle

Landing gear extended speed. The maximum speed at which an airplane can be safely flown with the landing gear extended.

Vle

Maximum landing gear extended speed.

VLF

Very Low Frequency

VLJ

Very Light Jet

Vlo

Landing gear operating speed. The maximum speed for extending or retracting the landing gear if using an airplane equipped with retractable landing gear.

Vlo

Maximum landing gear operating speed.

Vlof

Lift-off speed. The speed at which the aircraft departs the runway during takeoff.

Vlof

Lift-off speed.

Vmc

Minimum control airspeed. This is the minimum flight speed at which a twin-engine airplane can be satisfactorily controlled when an engine suddenly becomes inoperative and the remaining engine is at takeoff power.

VMC

Visual Meteorological Conditions.

Vmc

Minimum control speed with the critical engine inoperative.

VMC

Visual Meteorological Conditions

Vmd

Minimum drag speed.

Vmini

Instrument flight minimum speed, utilized in complying with minimum limit speed requirements for instrument flight

Vmo

Maximum operating speed expressed in knots.

Vmo/ Mmo

Maximum operating limit speed.

Vmu

Minimum unstick speed.

VNAV

Vertical Navigation

Vne

Never-exceed speed. Operating above this speed is prohibited since it may result in damage or structural failure. The red line on the airspeed indicator.

Vne

The never-exceed speed. Operating above this speed is prohibited since it may result in damage or structural failure. The red line on the airspeed indicator.

Vnei

Never Exceed Speed-IFR.

Vno

Maximum structural cruising speed. Do not exceed this speed except in smooth air. The upper limit of the green arc.

Vno

Maximum structural cruising speed.

VOL

Volume. Usually used to indicate that the volume of aircraft exceeds the airport´s capacity.

VOR

Very-high Frequency Omnidirectional range.

VOR

Very High Frequency Omni Directional Range. A ground-based electronic navigation aid transmitting very high frequency navigation signals, 360 degrees in azimuth, oriented from magnetic north. Used as the basis for navigation in the National Airspace System. The VOR periodically identifies itself by Morse Code and may have an additional voice identification feature. Voice features may be used by ATC or FSS for transmitting instructions/information to pilots.

VOR test facility (VOT)

A ground facility which emits a test signal to check VOR receiver accuracy. Some VOTs are available to the user while airborne, while others are limited to ground use only.

VOR test facility (VOT)

A ground facility which emits a test signal to check VOR receiver accuracy. Some VOTs are available to the user while airborne, while others are limited to ground use only.

VORTAC

A facility consisting of two components, VOR and TACAN, which provides three individual services: VOR azimuth, TACAN azimuth, and TACAN distance (DME) at one site.

VORTAC

A navigation aid providing VOR azimuth, TACAN azimuth, and TACAN distance measuring equipment (DME) at one site.

Vortex

In meteorology, any rotary flow in the atmosphere.

Vortices

Circular patterns of air created by the movement of an airfoil through the air when generating lift. As an airfoil moves through the atmosphere in sustained flight, an area of area of low pressure is created above it. The air flowing from the high pressure area to the low pressure area around and about the tips of the airfoil tends to roll up into two rapidly rotating vortices, cylindrical in shape. These vortices are the most predominant parts of aircraft wake turbulence and their rotational force is dependent upon the wing loading, gross weight, and speed of the generating aircraft. The vortices from medium to heavy aircraft can be of extremely high velocity and hazardous to smaller aircraft.

Vorticity

Turning of the atmosphere. Vorticity may be imbedded in the total flow and not readily identified by a flow pattern. Types are: absolute, negative, positive, and relative vorticity.

VOT

VOR Test Facility

VOT

A ground facility which emits a test signal to check vor receiver accuracy. Some VOTs are available to the user while airborne, and others are limited to ground use only.

Vp

Minimum dynamic hydroplaning speed. The minimum speed required to start dynamic hydroplaning.

VPA

Vertical Path Angle

Vr

Rotation speed. The speed that the pilot begins rotating the aircraft prior to lift-off.

Vr

Rotation speed.

VR

VFR Military Training Route

Vref

Reference Landing Speed

Vref

Reference Landing Speed.

Vref

The reference landing approach speed, usually about 1.3 times Vso plus 50 percent of the wind gust speed in excess of the mean wind speed.

Vs

The stalling speed or the minimum steady flight speed at which the airplane is controllable.

Vs1

Stalling speed or the minimum steady flight speed obtained in a specified configuration. For most airplanes, this is the power-off stall speed at the maximum takeoff weight in the clean configuration (gear up, if retractable, and flaps up). The lower limit of the green arc.

Vs1

The Stalling Speed or The minimum steady flight speed obtained in a specific configuration.

Vs1

The stalling speed or the minimum steady flight speed obtained in a specified configuration. For most airplanes, this is the power-off stall speed at the maximum takeoff weight in the clean configuration (gear up, if retractable, and flaps up). The lower limit of the green arc.

VSBY

Visibility. The ability, as determined by atmospheric conditions and expressed in units of distance, to see and identify prominent unlighted objects by day and prominent lighted objects by night.

VSI

Vertical Speed Indicator.

VSI

Vertical Speed Indicator.

Vso

Stalling speed or the minimum steady flight speed in the landing configuration. In small airplanes, this is the power-off stall speed at the maximum landing weight in the landing configuration (gear and flaps down). The lower limit of the white arc.

Vso

Stalling Speed or The minimum steady flight speed in the landing configuration

Vso

The Stalling Speed or The minimum steady flight speed in the landing configuration.

Vso

The stalling speed or the minimum steady flight speed in the landing configuration. In small airplanes, this is the power-off stall speed at the maximum landing weight in the landing configuration (gear and flaps down). The lower limit of the white arc.

Vsr

Reference Stall Speed.

Vsr0

Reference Stall Speed In The Landing Configuration.

Vsr1

Reference Stall Speed In A Specific Configuration.

Vsse

Safe, intentional one-engine inoperative speed. The minimum speed to intentionally render the critical engine inoperative.

Vsw

Speed at which onset of natural or artificial stall warning occurs.

VTF

Vector to Final

VTOL Aircraft

Vertical Takeoff And Landing Aircraft.

Vtoss

Takeoff Safety Speed For Category A Rotorcraft.

VV

Vertical Visibility

VVI

Vertical Velocity Indicator

Vx

Best angle-of-climb speed. The airspeed at which an airplane gains the greatest amount of altitude in a given distance. It is used during a short-field takeoff to clear an obstacle.

Vx

Speed For Best Angle Of Climb.

Vx

Best angle-of-climb speed. The airspeed at which an airplane gains the greatest amount of altitude in a given distance. It is used during a short-field takeoff to clear an obstacle.

Vxse

Best angle of climb speed with one engine inoperative. The airspeed at which an airplane gains the greatest amount of altitude in a given distance in a light, twin-engine airplane following an engine failure.

Vy

Best rate-of-climb speed. This airspeed provides the most altitude gain in a given period of time.

Vy

Speed For Best Rate Of Climb.

Vy

Best rate-of-climb speed. This airspeed provides the most altitude gain in a given period of time.

Vyi

Instrument climb speed, utilized instead of Vy for compliance with the climb requirements for instrument flight

Vyse

Best rate-of-climb speed with one engine inoperative. This airspeed provides the most altitude gain in a given period of time in a light, twin-engine airplane following an engine failure.

Vyse

Best rate-of-climb speed with one engine inoperative. This airspeed provides the most altitude gain in a given period of time in a light, twin-engine airplane following an engine failure.

WA

AIRMET

WAAS

Wide Area Augmentation System.

WAAS

Wide Area Augmentation System

WAC

World Aeronautical Chart Discontinued on June 25, 2015

WAC

World Aeronautical Chart Discontinued on June 25, 2015

Wake Turbulence

Wingtip vortices that are created when an airplane generates lift. When an airplane generates lift, air spills over the wingtips from the high pressure areas below the wings to the low pressure areas above them. This flow causes rapidly rotating whirlpools of air called wingtip vortices or wake turbulence.

Wake turbulence

Turbulence found to the rear of a solid body in motion relative to a fluid. In aviation terminology, the turbulence caused by a moving aircraft.

Wall cloud

The well-defined bank of vertically developed clouds having a wall-like appearance which form the outer boundary of the eye of a well-developed tropical cyclone.

Warm front

Any non-occluded front which moves in such a way that warmer air replaces colder air.

Warm Front

Any nonoccluded front that moves in such a way that warmer air replaces colder air.

Warm sector

The area covered by warm air at the surface and bounded by the warm front and cold front of a wave cyclone.

Warning area

An area containing hazards to any aircraft not participating in the activities being conducted in the area. Warning areas may contain intensive military training, gunnery exercises, or special weapons testing.

Warning area

A warning area is airspace of defined dimensions, extending from 3 nautical miles outward from the coast of the United States, that contains activity that may be hazardous to nonparticipating aircraft. The purpose of such warning areas is to warn nonparticipating pilots of the potential danger. A warning area may be located over domestic or international waters or both.

WARP

Weather And Radar Processing.

Waste Gate

A controllable valve in the tailpipe of an aircraft reciprocating engine equipped with a turbocharger. The valve is controlled to vary the amount of exhaust gases forced through the turbocharger turbine.

Water equivalent

The depth of water that would result from the melting of snow or ice.

Water vapor

Water in the invisible gaseous form.

Waterspout

A tornado that forms over water.

Wave cyclone

A cyclone which forms and moves along a front. The circulation about the cyclone center tends to produce a wavelike deformation of the front.

Waypoint

A predetermined geographical position used for route/instrument approach definition, progress reports, published VFR routes, visual reporting points or points for transitioning and/or circumnavigating controlled and/or special use airspace, that is defined relative to a VORTAC station or in terms of latitude/longitude coordinates.

Waypoint (WP)

Waypoints

Area navigation waypoints are specified geographical locations, or fixes, used to define an area navigation route or the flight path of an aircraft employing area navigation. Waypoints may be any of the following types:predefined, published, floating, user-defined, fly-by, or fly-over.

WCA

Wind Correction Angle.

WCA

Wind Correction Angle.

Weather

The state of the atmosphere, mainly with respect to its effects on life and human activities; refers to instantaneous conditions or short term changes as opposed to climate.

Weather Advisory

In aviation weather forecast practice, an expression of hazardous weather conditions not predicted in the area forecast, as they affect the operation of air traffic and as prepared by the NWS.

Weather Advisory

In standard aviation weather forecast terminology, a warning of hazardous weather conditions not predicted in the forecast area that may affect air traffic operations. These reports are prepared by the NWS.

Weather and radar processor (WARP)

A device that provides real-time, accurate, predictive and strategic weather information presented in an integrated manner in the National Airspace System (NAS).

Weather and radar processor (WARP)

A device that provides real-time, accurate, predictive, and strategic weather information presented in an integrated manner in the National Airspace System (NAS).

Weather depiction chart

Details surface conditions as derived from METAR and other surface observations.

Weather radar

Radar specifically designed for observing weather. Some types are cloud detection radar and storm detection radar.

Weather vane

A wind vane.

Weathervane

The tendency of the aircraft to turn into the relative wind.

Wedge

Same as ridge—an elongated area of relatively high atmospheric pressure; usually associated with and most clearly identified as an area of maximum anticyclonic curvature of the wind flow (isobars, contours, or streamlines).

Weight

A measure of the heaviness of an object. The force by which a body is attracted toward the center of the Earth (or another celestial body) by gravity. Weight is equal to the mass of the body times the local value of gravitational acceleration. One of the four main forces acting on an aircraft. Equivalent to the actual weight of the aircraft. It acts downward through the aircraft’s center of gravity toward the center of the Earth. Weight opposes lift.

Weight

The force exerted by an aircraft from the pull of gravity.

Weight

The force exerted by an aircraft from the pull of gravity.

Weight And Balance

The aircraft is said to be in weight and balance when the gross weight of the aircraft is under the max gross weight, and the center of gravity is within limits and will remain in limits for the duration of the flight.

Weight-shift-control aircraft

A powered aircraft with a framed pivoting wing and a fuselage controllable only in pitch and roll by the pilot’s ability to change the aircraft’s center of gravity with respect to the wing. Flight control of the aircraft depends on the wing’s ability to flexibly deform rather than the use of control surfaces.

Wet bulb

Contraction of either wet-bulb temperature or wet-bulb thermometer.

Wet-bulb temperature

The lowest temperature that can be obtained on a wet-bulb thermometer in any given sample of air, by evaporation of water (or ice) from the muslin wick; used in computing dew point and relative humidity.

Wet-bulb thermometer

A thermometer with a muslin-covered bulb used to measure wet-bulb temperature.

WFO

Weather Forecast Office

WGS-84

World Geodetic System of 1984

Wheelbarrowing

A condition caused when forward yoke or stick pressure during takeoff or landing causes the aircraft to ride on the nosewheel alone.

When Able

When used in conjunction with ATC instructions, gives the pilot the latitude to delay compliance until a condition or event has been reconciled. Unlike “pilot discretion,” when instructions are prefaced “when able,” the pilot is expected to seek the first opportunity to comply. Once a maneuver has been initiated, the pilot is expected to continue until the specifications of the instructions have been met. “When able,” should not be used when expeditious compliance is required.

Whirlwind

A small, rotating column of air; may be visible as a dust devil.

Wide area augmentation system (WAAS)

A differential global positioning system (DGPS) that improves the accuracy of the system by determining position error from the GPS satellites, then transmitting the error, or corrective factors, to the airborne GPS receiver.

Wide area augmentation system (WAAS)

Wilco

I have received your message, understand it, and will comply with it.

Willy-willy

A tropical cyclone of hurricane strength near Australia.

Wind

Air in motion relative to the surface of the earth; generally used to denote horizontal movement.

Wind correction angle (WCA)

The angle between the desired track and the heading of the aircraft necessary to keep the aircraft tracking over the desired track.

Wind correction angle (WCA)

The angle between the desired track and the heading of the aircraft necessary to keep the aircraft tracking over the desired track.

Wind direction

The direction from which wind is blowing.

Wind Direction Indicators

Indicators that include a wind sock, wind tee, or tetrahedron. Visual reference will determine wind direction and runway in use.

Wind shear

The rate of change of wind velocity (direction and/or speed) per unit distance; conventionally expressed as vertical or horizontal wind shear.

Wind Shear

A change in wind speed and/or wind direction in a short distance resulting in a tearing or shearing effect. It can exist in a horizontal or vertical direction and occasionally in both.

Wind speed

Rate of wind movement in distance per unit time.

Wind vane

An instrument to indicate wind direction.

Wind velocity

A vector term to include both wind direction and wind speed.

Windmilling

When the air moving through a propeller creates the rotational energy.

Winds and temperature aloft forecast (FD)

A twice daily forecast that provides wind and temperature forecasts for specific locations in the contiguous United States.

Windsock

A truncated cloth cone open at both ends and mounted on a freewheeling pivot that indicates the direction from which the wind is blowing.

Wing

Airfoil attached to each side of the fuselage and are the main lifting surfaces that support the airplane in flight.

Wing Area

The total surface of the wing (square feet), which includes control surfaces and may include wing area covered by the fuselage (main body of the airplane), and engine nacelles.

Wing Chord

A straight-line distance across a wing from leading edge to trailing edge.

Wing Span

The maximum distance from wingtip to wingtip.

Wing Tank Liner

A liner for aircraft fuel tanks which limits the amount of fuel that can be spilled in the event of a crash.

Wing Twist

A design feature incorporated into some wings to improve aileron control effectiveness at high angles of attack during an approach to a stall.

Winglet or tip fin

An out-of-plane surface extending from a lifting surface. The surface may or may not have control surfaces.

Wings

Airfoils attached to each side of the fuselage and are the main lifting surfaces that support the airplane in flight.

Wingtip Vortices

The rapidly rotating air that spills over an airplane’s wings during flight. The intensity of the turbulence depends on the airplane’s weight, speed, and configuration. It is also referred to as wake turbulence. Vortices from heavy aircraft may be extremely hazardous to small aircraft.

Wingtip vortices

The rapidly rotating air that spills over an airplane’s wings during flight. The intensity of the turbulence depends on the airplane’s weight, speed, and configuration. Also referred to as wake turbulence. Vortices from heavy aircraft may be extremely hazardous to small aircraft.

WMO

World Meteorological Organization

WMS

Wide-Area Master Station

WMSC

Weather Message Switching Center

WMSCR

Weather Message Switching Center Replacement

WND

Wind

Words Twice

A. As a request: “Communication is difficult. Please say every phrase twice.”
B. As information: “Since communications are difficult, every phrase in this message will be spoken twice.”

Work

A measurement of force used to produce movement.

Work

A measurement of force used to produce movement.

Working or short-term memory

The portion of the brain that receives information from the sensory register. This portion of the brain can store information in memory for only a short period of time. If the information is determined by an individual to be important enough to remember, it must be coded in some way for transmittal to long-term memory.

World Aeronautical Charts (WAC)

A standard series of aeronautical charts covering land areas of the world at a size and scale convenient for navigation (1:1,000,000) by moderate speed aircraft. Topographic information includes cities and towns, principal roads, railroads, distinctive landmarks, drainage, and relief. Aeronautical information includes visual and radio aids to navigation, airports, airways, restricted areas, obstructions and other pertinent data. Discontinued on June 25, 2015

World Aeronautical Charts (WAC) (1:1,000,000)

Provide a standard series of aeronautical charts covering land areas of the world at a size and scale convenient for navigation by moderate speed aircraft. Topographic information includes cities and towns, principal roads, railroads, distinctive landmarks, drainage, and relief. Aeronautical information includes visual and radio aids to navigation, airports, airways, restricted areas, obstructions, and other pertinent data. Discontinued.

WP

Waypoint

WP

Waypoint

WRS

Wide-Area Ground Reference Station

WS

SIGMET

WST

Convective Significant Meteorological Information

WW

Severe Weather Watch Bulletin

WX

Weather

WX DEV

Weather Deviation

Yaw

Rotation about the vertical axis of an aircraft.

Yaw String

A string on the nose or windshield of an aircraft in view of the pilot that indicates any slipping or skidding of the aircraft.

Z

Zulu Time. Another term used to designate Coordinated Universal Time (UTC), the standard time common to every place in the world. Formerly and still widely called Greenwich Mean Time (GMT) and also World Time, UTC nominally reflects the mean solar time along the Earth´s prime meridian.

Zero Fuel Weight

The weight of the aircraft to include all useful load except fuel.

Zero Sideslip

A maneuver in a twin-engine airplane with one engine inoperative that involves a small amount of bank and slightly uncoordinated flight to align the fuselage with the direction of travel and minimize drag.

Zero Thrust (Simulated Feather)

An engine configuration with a low power setting that simulates a propeller feathered condition.

Zonal wind

A west wind; the westerly component of a wind. Conventionally used to describe large-scale flow that is neither cyclonic nor anticyclonic.

Zone of confusion

Volume of space above the station where a lack of adequate navigation signal directly above the VOR station causes the needle to deviate.Warning area. An area containing hazards to any aircraft not participating in the activities being conducted in the area. Warning areas may contain intensive military training, gunnery exercises, or special weapons testing.

Zone of confusion

Volume of space above the station where a lack of adequate navigation signal directly above the VOR station causes the needle to deviate.

Zulu time

A term used in aviation for coordinated universal time (UTC) which places the entire world on one time standard.

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