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 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–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.

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.

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.

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-go distance

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

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.

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.

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 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.

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 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.

Administrator

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

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.

Advection fog

Fog resulting from the movement 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

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 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.

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.

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.

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.

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.

Air carrier

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

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 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

An extensive body of air having fairly uniform properties of temperature and moisture.

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 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 (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 surveillance radar (ARSR)

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

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 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 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.

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 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 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 transportation

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

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 reference landing speed (VREF), if specified, or if VREF is not specified, 1.3 Vso (the stalling speed or minimum steady flight speed in the landing configuration) at the maximum certificated landing weight.

Aircraft approach category

A performance grouping of aircraft based on a speed of 1.3 times the stall speed in the landing configuration at maximum gross landing weight.

Aircraft approach category

A performance grouping of aircraft based on a speed of 1.3 times the stall speed in the landing configuration at maximum gross landing weight.

Aircraft checkouts

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

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.

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)

An FAA-approved document, prepared by the holder of a Type Certificate for an aircraft, that specifies the operating limitations and contains the required markings and placards and other information applicable to the regulations under which the aircraft was certificated.

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 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 diagram

The section of an instrument approach procedure chart that shows a detailed diagram of the airport. This diagram includes surface features and airport configuration information.

Airport diagram

The section of an instrument approach procedure chart that shows a detailed diagram of the airport. This diagram includes surface features and airport configuration information.

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)

Airport surveillance radar (ASR)

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

Airport surveillance radar (ASR)

Approach control radar used to detect and display an aircraft’s 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 surveillance radar approach

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.

Airport/Facility Directory (A/FD)

An FAA publication containing information on all airports, communications, and NAVAIDs. Title changed to Chart Supplement.

Airport/Facility Directory (A/FD)

An FAA publication containing information on all airports, communications, and NAVAIDs. Title changed to Chart Supplement.

Airship

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

Airspeed

Rate of the aircraft’s progress through the air.

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.

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

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.

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.

Alert area

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

Alert Area

An alert area is established to inform pilots of a specific area wherein a high volume of pilot training or an unusual type of aeronautical activity is conducted.

Alert area

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

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

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.

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 airport

An airport at which an aircraft may land if a landing at the intended airport becomes inadvisable.

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

Height expressed in units of distance above a reference plane, usually above mean sea level or above ground.

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 engine

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

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.

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.

Amendment status

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

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.

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.

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.

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 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 lighting system (ALS)

Provides lights that will penetrate the atmosphere far enough from touchdown to give directional, distance, and glide path information for safe transition from instrument to visual flight.

Approach lighting system (ALS)

Provides lights that will penetrate the atmosphere far enough from touchdown to give directional, distance, and glidepath information for safe transition from instrument to visual flight.

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.

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)

A method of navigation that permits aircraft operations on any desired course within the coverage of station referenced navigation signals or within the limits of self contained system capability.

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 that permits aircraft operations on any desired flight path.

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) route

An ATS route based on RNAV that can be used by suitably equipped aircraft.

Area of operation

A phase of the practical test within the PTS.

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.

Arm

Moment arm.

Armed Forces

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

Aspect ratio

Span of a wing divided by its average chord.

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.

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.

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

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 sort of a 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 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

Attitude management

The ability to recognize hazardous attitudes in oneself and the willingness to modify them as necessary through the application of an appropriate antidote thought.

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.

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)/Automated Weather Sens

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

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 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).

Automatic dependent surveillance broadcast (ADS-B)

A device used in aircraft that repeatedly broadcasts a message that includes position (such as latitude, longitude, and altitude), velocity, and possibly other information.

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 device used in aircraft that repeatedly broadcasts a message that includes position (such as latitude, longitude, and altitude), velocity, and possibly other information.

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 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.

Automatic terminal information service (ATIS)

The continuous broadcast of recorded non-control information in selected terminal areas. Its purpose is to improve controller effectiveness and relieve frequency congestion by automating repetitive transmission of essential but routine information.

Automatic terminal information service (ATIS)

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.

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.

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.

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.

Axial flow compressor

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.

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 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.

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

Removable or permanently installed weight in an aircraft used to bring the center of gravity into the allowable range.

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.

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.

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.

Beam resolution

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

Beaufort scale

A scale of wind speeds.

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.

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.

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.

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.

Block altitude

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

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.

Bookmark

A means of saving addresses on the World Wide Web (WWW) for easy future access. Usually done by selecting a button on the web browser screen, it saves the current web address so it does not have to be input again in a lengthy series of characters.

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.

Brake horsepower

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

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.

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.

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.).

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.

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.

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 indicated airspeed of an aircraft, corrected for position and instrument error. Calibrated airspeed is equal to true airspeed in standard atmosphere at sea level.

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.

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

CAMs

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

Canard

The forward wing of a canard configuration and may be a fixed, movable, or variable geometry surface, with or without control surfaces.

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 wing is substantially less than that of the main wing.

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.

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.

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 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 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.

Ceiling

The height above the earth’s surface of the lowest layer of clouds or obscuring phenomena that is reported as “broken”, “overcast”, or “obscuration”, and not classified as “thin” or “partial”.

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.

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 (CG)

The point at which an airplane would balance if it were possible to suspend it at that point. It is the mass center of the airplane, or the theoretical point at which the entire weight of the airplane is assumed to be concentrated. It may be expressed in inches from the reference datum, or in percentage of mean aerodynamic chord (MAC). The location depends on the distribution of weight in the airplane.

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 Gravity(CG)

The point at which an airplane would balance if it were possible to suspend it at that point. It is the mass center of the airplane, or the theoretical point at which the entire weight of the airplane is assumed to be concentrated. It may be expressed in inches from the reference datum, or in percent of mean aerodynamic chord (MAC). The location depends on the distribution of weight in the airplane.

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 Radar ARTS Presentation/Processing (CENRAP)

CENRAP was developed to provide an alternative to a non-radar environment at terminal facilities should an ASR fail or malfunction. CENRAP sends aircraft radar beacon target information to the ASR terminal facility equipped with ARTS.

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.

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.

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 flow compressor

An impeller-shaped device that receives air at its center and slings the 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.

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.

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.

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.

Changeover point (COP)

A point along the route or airway segment between two adjacent navigation facilities or waypoints where changeover in navigation guidance should occur.

Changeover point (COP)

A point along the route or airway segment between two adjacent navigation facilities or waypoints where changeover in navigation guidance should occur.

Charted Visual Flight Procedure (CVFP)

A CVFP may be established at some towered airports for environmental or noise considerations, as well as when necessary for the safety and efficiency of air traffic operations. Designed primarily for turbojet aircraft, CVFPs depict prominent landmarks, courses, and recommended altitudes to specific runways.

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.

Chord line

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

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 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.

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 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 E airspace

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

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 not associated with any visible moisture.

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 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 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.

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 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 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 on request

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

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.

Clearance void time

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.

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.

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.

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.

Coefficient of lift

The ratio between lift pressure and dynamic pressure.

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

The boundary between two air masses where cold air is replacing warm 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 Traffic Advisory Frequency

The common frequency used by airport traffic to announce position reports in the vicinity of the airport.

Compact disk (CD)

A small plastic optical disk which contains recorded music or computer data. Also, a popular format for storing information digitally. The major advantage of a CD is its capability to store enormous amounts of information.

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 ILS.

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 ILS.

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 small circle graduated in 360° increments, to show direction expressed in degrees.

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.

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 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 rpm. Compressor stall will be indicated by a rise in exhaust temperature or rpm 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.

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.

Computer-based training (CBT)

The use of the computer as a training device. CBT is sometimes called computer-based instruction (CBI); the terms and acronyms are synonymous and may be used interchangeably.

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.

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

A change of state of water from a gas (water vapor) to a liquid.

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 nuclei

Small particles of solid matter in the air on which water vapor condenses.

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.

Configuration

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

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.

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.

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 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.

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.

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 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 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 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.

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

An airspace of defined dimensions within which air traffic control service is provided to IFR flights and to VFR flights in accordance with the airspace classification.
Note: Controlled airspace is a generic term that covers 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.

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.

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 weather

Unstable, rising air found in cumuliform clouds.

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.

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.

Coordination

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

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.

Correlation

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

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.

Course

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

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.

Cowl flaps

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

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.

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 altitude

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

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 whose failure would most adversely affect the performance or handling qualities of an aircraft.

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.

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 Component

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

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 clearance

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 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 induction

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

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.

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.

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-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.

Dark adaptation

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

Dark adaptation

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

Database Columns

The spaces for data entry on each record. One column can accommodate one character.

Database Field

The collection of characters needed to define one item of information.

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.

Database Record

A single line of computer data made up of the fields necessary to define fully a single useful piece of data.

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.

Datum (Reference Datum)

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

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 (DA)

A specified altitude in the precision approach, charted in feet MSL, at which a missed approach must be initiated if the required visual reference to continue the approach has not been established.

Decision altitude (DA)

A specified altitude 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 altitude is expressed in feet above mean sea level.

Decision altitude (DA)

A specified altitude in the precision approach, charted in feet MSL, at which a missed approach must be initiated if the required visual reference to continue the approach has not been established.

Decision Height (DH)

See Decision Altitude

Decision height (DH)

A specified altitude in the precision approach, charted in height above threshold elevation, at which a decision must be made either to continue the approach or to execute a missed approach.

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.

Decision height (DH)

A specified altitude in the precision approach, charted in height above threshold elevation, at which a decision must be made either to continue the approach or to execute a missed approach.

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.

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.

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

Pressure altitude corrected for nonstandard temperature. Density altitude is used in computing the performance of an aircraft and its engines.

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.

Density altitude

Pressure altitude corrected for nonstandard temperature. Density altitude is used in computing the performance of an aircraft and its engines.

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 procedure (DP)

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

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.

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.

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.

Detonation

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.

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

Moisture that has condensed from water vapor. Usually found on cooler objects near the ground, such as grass, as the near-surface layer of air cools faster than the layers of air above it.

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.

Dewpoint

The temperature at which air can hold no more water.

Dewpoint

The temperature at which air reaches a state where it can hold no more water.

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 ailerons

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.

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 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)

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.

Directional stability

Discontinuity

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

Discrimination

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

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 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.

Distractors

Incorrect responses to a multiple-choice test item.

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.

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.

DME arc

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

DME arc

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

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 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.

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.

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.

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

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

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.

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.

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.

Dutch roll

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.

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.

Early ETOPS

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

Echo

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

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.

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.

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.).

Electronic learning (e-learning)

Any type of education that involves an electronic component such as the Internet, a network, a stand-alone computer, CD/DVDs, video conferencing, websites, or e-mail in its delivery.

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.

EM wave

Electromagnetic wave.

Emergency

A distress or urgent condition.

Emergency

A distress or urgent condition.

Emergency Locator Transmitter

A small, self-contained radio transmitter that will automatically, upon the impact of a crash, transmit an emergency signal on 121.5, 243.0, or 406.0 MHz.

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.

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 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 (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

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

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 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.

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.

Engine pressure ratio (EPR)

The ratio of turbine discharge pressure divided by compressor inlet pressure, which 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.

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).

Equilibrium

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

The calibrated airspeed of an aircraft corrected for adiabatic compressible flow for the particular altitude. Equivalent airspeed is equal to calibrated airspeed in standard atmosphere at sea level.

Equivalent airspeed

Equivalent Shaft Horsepower (ESHP)

A measurement of the total horsepower of a turboprop engine, including that provided by jet thrust.

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.

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.

Evaporation

The transformation of a liquid to a gaseous state, such as the change of water to water vapor.

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 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-further-clearance (EFC)

The time a pilot can expect to receive clearance beyond a clearance limit.

Expect-further-clearance (EFC)

The time a pilot can expect to receive clearance beyond a clearance limit.

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.

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.

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 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.

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 facilities

Used by ATC to direct aircraft to intervening fixes between the en route structure and the initial approach fix.

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.

Field

See Database Field

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 approach

Part of an instrument approach procedure in which alignment and descent for landing are accomplished.

Final approach

Part of an instrument approach procedure in which alignment and descent for landing are accomplished.

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 fix (FAF)

The fix from which the IFR final approach to an airport is executed, and which identifies the beginning of the final approach segment. An FAF is designated on government charts by a Maltese cross symbol for nonprecision approaches, and a lightning bolt symbol for precision approaches.

Final approach fix (FAF)

Defines the beginning of the final approach segment and the point where final segment descent may begin.

Final approach fix (FAF)

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.

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.

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.

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.

Fixed-pitch propellers

Propellers with fixed blade angles. Fixed-pitch propellers are designed as climb propellers, cruise propellers, or standard propellers.

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 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 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 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 250 represents a barometric altimeter indication of 25,000 feet; flight level 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 level (FL)

A measure of altitude (in hundreds of feet) used by aircraft flying above 18,000 feet with the altimeter set at 29.92" Hg.

Flight level (FL)

A measure of altitude (in hundreds of feet) used by aircraft flying above 18,000 feet with the altimeter set at 29.92 "Hg.

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 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 air traffic control.

Flight review

A 14 CFR 61.56 requirement designed to assess and update a pilot’s knowledge and skills.

Flight simulation training device (FSTD)

A flight simulator or a flight training device.

Flight strips

Paper strips containing instrument flight information, used by ATC when processing flight plans.

Flight strips

Paper strips containing instrument flight information, used by ATC when processing flight plans.

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 training devices (FTDs)

A full-size replica of the instruments, equipment, panels, and controls of an aircraft, or set of aircraft, in an open flight deck area or in an enclosed cockpit. A force (motion) cueing system or visual system is not required.

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.

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-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.

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.

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)

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.

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.

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.

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 level

A level in the atmosphere at which the temperature is 0° C (32° F).

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.

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 different air masses.

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.

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 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 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.

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.

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.

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.

Gateway Fix

A navigational aid or fix where an aircraft transitions between the domestic route structure and the oceanic route airspace.

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).

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 of an intermediate approach segment prescribed for a precision approach that ensures obstacle clearance.

Global landing system (GLS)

An instrument approach with lateral and vertical guidance with integrity limits (similar to barometric vertical navigation (BRO VNAV).

Global landing system (GLS)

An instrument approach with lateral and vertical guidance with integrity limits (similar to barometric vertical navigation (BARO 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 navigation satellite systems (GNSS)

Satellite navigation systems that provide autonomous geo-spatial 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 Position System (GPS)

A satellite-based radio positioning, navigation, and time-transfer system.

Global positioning system (GPS)

Navigation system that uses satellite rather than ground-based transmitters for location information.

Global positioning system (GPS)

Navigation system that uses satellite rather than ground-based transmitters for location information.

Go-Around

Terminating a landing approach.

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 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.

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.

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.

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 adjustable trim tab

Non-movable metal trim tab on a control surface. 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 Communication Outlet (GCO)

An unstaffed, remotely controlled ground/ground communications facility. Pilots at uncontrolled airports may contact ATC and AFSS via Very High Frequency (VHF) radio to a telephone connection. This lets pilots obtain an instrument clearance or close a VFR/IFR flight plan.

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 effect

The condition of slightly increased air pressure below an airplane wing or helicopter rotor system that increases the amount of lift produced. It exists within approximately one wing span or one rotor diameter from the ground. It results from a reduction in upwash, downwash, and wingtip vortices, and provides a corresponding decrease in induced drag.

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 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.

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 (GS)

The actual speed of the airplane over the ground. It is true airspeed adjusted for wind. Groundspeed decreases with a headwind, and increases with a tailwind.

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.

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.

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.

Hail

A form of precipitation composed of balls or irregular lumps of ice, always produced by convective clouds which are nearly always cumulonimbus.

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.

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 (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.

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.

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 display (HUD)

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.

Height above airport (HAA)

The height of the MDA above the published airport elevation.

Height above airport (HAA)

The height of the MDA above the published airport elevation.

Height above landing (HAL)

The height above a designated helicopter landing area used for helicopter instrument approach procedures.

Height above landing (HAL)

The height above a designated helicopter landing area used for helicopter instrument approach procedures.

Height Above Touchdown (HAT)

The height of the DA above touchdown zone elevation (TDZE).

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).

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.

Heliport

An area of land, water, or structure used or intended to be used for the landing and takeoff of helicopters.

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 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.

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.

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.

Holding

A predetermined maneuver that keeps aircraft within a specified airspace while awaiting further clearance from ATC.

Holding

A predetermined maneuver that keeps aircraft within a specified airspace while awaiting further clearance from ATC.

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.

Holding pattern

Homing

Flying the aircraft on any heading required to keep the needle pointing to the 0 relative bearing position.

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.

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.

Hot start

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.

Hung start

In gas turbine engines, a condition of normal light off but with rpm remaining at some low value rather than increasing to the normal idle rpm. 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.

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.

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 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.

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.

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 conditions

Weather conditions below the minimum for flight under visual flight rules.

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”.

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 categories

Categories of instrument approach procedures allowed at airports equipped with the following types of instrument landing systems: 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 categories

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.

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.

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

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

The speed of an aircraft as shown on its pitot static airspeed indicator calibrated to reflect standard atmosphere adiabatic compressible flow at sea level uncorrected for airspeed system errors.

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 airspeed (IAS)

Shown on the dial of the instrument airspeed indicator on an aircraft. Indicated airspeed (IAS) is the airspeed indicator reading uncorrected for instrument, position, and other errors. Indicated airspeed means the speed of an aircraft as shown on its pitot static airspeed indicator calibrated to reflect standard atmosphere adiabatic compressible flow at sea level uncorrected for airspeed system errors. Calibrated airspeed (CAS) is IAS corrected for instrument errors, position error (due to incorrect pressure at the static port) and installation errors.

Indicated Altitude

The altitude read directly from the altimeter (uncorrected) when it is set to the current altimeter setting.

Indicated altitude

The altitude above mean sea level indicated on a pressure altimeter set at current local altimeter setting.

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.

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 (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)

Initial approach fix (IAF)

The fix depicted on IAP charts where the instrument approach procedure (IAP) begins unless otherwise authorized by ATC.

Initial approach fix (IAF)

The fix depicted on IAP charts where the instrument approach procedure (IAP) begins unless otherwise authorized by ATC.

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.

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.

Inoperative components

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 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)

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 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 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 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 takeoff

Using the instruments rather than outside visual cues to maintain runway heading and execute a safe takeoff.

Instrument takeoff

Using the instruments rather than outside visual cues to maintain runway heading and execute a safe takeoff.

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.

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.

Interactive video

Software that responds quickly to certain choices and commands by the user. A typical system consists of a compact disk, computer, and video technology.

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.

Intercooler

A device used to reduce the temperatures 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.

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 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)

The United Nations agency for developing the principles and techniques of international air navigation, and fostering planning and development of international civil air transport.

International Civil Aviation Organization (ICAO)

The United Nations agency for developing the principles and techniques of international air navigation, and fostering planning and development of international civil air transport.

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.

Internet

An electronic network that connects computers around the world.

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.

Intersection

Typically, the point at which two VOR radial position lines cross on a route, usually intersecting at a good angle for positive indication of position, resulting in a VOR/VOR fix.

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.

Inverter

A solid-state electronic device that converts D.C.

Inverter

A solid-state electronic device that converts D.C. into A.C. current of the proper voltage and frequency to operate A.C. gyro instruments.

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.

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 designated to serve flight operations from 18,000 feet MSL up to and including FL 450.

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.

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.

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.

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.

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 breeze

A coastal breeze flowing from land to sea caused by temperature differences when the sea surface is warmer than the adjacent land. The land breeze usually occurs at night and alternates with the sea breeze that 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.

Landing Distance Available (LDA)

ICAO defines LDA as the length of runway, which is declared available and suitable for the ground run of an aeroplane landing.

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 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 aircraft

Aircraft of more than 12,500 pounds, maximum certificated takeoff weight.

Large Aircraft

An aircraft of more than 12,500 pounds, maximum certificated takeoff weight. As defined in 14 CFR part 1.

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 Balance

Balance around the roll, or longitudinal, axis.

Lateral Navigation (LNAV)

Azimuth navigation, without positive vertical guidance. This type of navigation is associated with nonprecision approach procedures or en route.

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 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.

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.

Lead radial

The radial at which the turn from the DME arc to the inbound course is started.

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 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.

Leading-edge flap

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.

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.

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-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.

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.

Limit load factor

Amount of stress, or load factor, that an aircraft can withstand before structural damage or failure occurs.

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.

Link

On a website, an external web location that can be accessed by merely clicking on words identifying the new site. They are usually identified by a different color type, underlining, or a button (picture or icon) indicating access to a new site.

Lithometeor

The general term for dry particles suspended in the atmosphere such as dust, haze, smoke, and sand.

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, inertia forces, or ground or water reactions.

Load Factor

The ratio of the maximum load an aircraft can sustain to the total weight of the aircraft. Normal category aircraft must have a load factor of a least 3.8, Utility category aircraft 4.4, and acrobatic category aircraft, 6.0.

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.

Local Area Augmentation System (LAAS)

LAAS further increases the accuracy of GPS and improves signal integrity warnings.

Local area augmentation system (LAAS)

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.

Local area augmentation system (LAAS)

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-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.

Localizer-type directional aid (LDA)

Locator middle marker (LMM)

Nondirectional radio beacon (NDB) compass locator, collocated with a middle marker (MM).

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).

Locator outer marker (LOM)

NDB compass locator, collocated with an outer marker (OM).

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 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.

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.

Low

An area of low barometric pressure, with its attendant system of winds. Also called a barometric depression or cyclone.

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.

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.

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 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 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 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.

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.

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 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.

Mammato cumulus

Obsolete. Now referred to as cumulonimbus mamma.

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 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.

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.

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

Absolute pressure as measured at the appropriate point in the induction system and usually expressed 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.

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.

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.

Marker beacon

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.

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 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 authorized altitude (MAA)

A published altitude representing the maximum usable altitude or flight level for an airspace structure or route segment.

Maximum authorized altitude (MAA)

A published altitude representing the maximum usable altitude or flight level for an airspace structure or route segment.

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 Landing Weight

(GAMA) Maximum weight approved for the landing touchdown.

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 Ramp Weight

(GAMA) Maximum weight approved for ground maneuver. It includes weight of start, taxi, and runup fuel.

Maximum ramp weight

Maximum Takeoff Weight

The maximum allowable weight for takeoff.

Maximum Takeoff Weight

(GAMA) Maximum weight approved for the start of the takeoff run.

Maximum takeoff weight

The maximum allowable weight for takeoff.

Maximum Taxi Weight

Maximum weight approved for ground maneuvers. This is the same as maximum ramp weight.

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 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.

Maximum Zero Fuel Weight (GAMA)

The maximum weight, exclusive of usable fuel.

Maximum zero fuel weight (GAMA)

The maximum weight, exclusive of usable fuel.

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.

Medical certificate

Acceptable evidence of physical fitness on a form prescribed by the Administrator.

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.

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 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.

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.

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.

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.

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.

Military Airspace Management System (MAMS)

A Department of Defense system to collect and disseminate information on the current status of special use airspace. This information is provided to the Special Use Airspace Management System (SAMS). The electronic interface also provides SUA schedules and historical activation and utilization data.

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)

Airspace established for the purpose of separating certain military training activities from IFR traffic.

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.

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 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 crossing altitude (MCA)

The lowest allowed altitude at certain fixes an aircraft must cross when proceeding in the direction of a higher minimum en route altitude (MEA).

Minimum crossing altitude (MCA)

The lowest allowed altitude at certain fixes an aircraft must cross when proceeding in the direction of a higher minimum en route altitude (MEA).

Minimum Descent Altitude (MDA)

The lowest altitude, expressed in feet above mean sea level, to which descent is authorized on final approach or during circle-to-land maneuvering in execution of a standard instrument approach procedure where no electronic glide slope is provided.

Minimum descent altitude (MDA)

The lowest altitude (in feet MSL) to which descent is authorized on final approach, or during circle-to-land maneuvering in execution of a nonprecision approach.

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 descent altitude (MDA)

The lowest altitude (in feet MSL) to which descent is authorized on final approach, or during circle-to-land maneuvering in execution of a nonprecision approach.

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 Drag Speed (L/Dmax)

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 en route altitude (MEA)

The lowest published altitude between radio fixes that ensures acceptable navigational signal coverage and meets obstacle clearance requirements between those fixes.

Minimum en route altitude (MEA)

The lowest published altitude between radio fixes that ensures acceptable navigational signal coverage and meets obstacle clearance requirements between those fixes.

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 IFR Altitude (MIA)

Minimum altitudes for IFR operations are prescribed in Part 91. These MIAs are published on NACO charts and prescribed in Part 95 for airways and routes, and in Part 97 for standard instrument approach procedures.

Minimum Navigation Performance Specifications (MNPS)

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. Under certain conditions, non-MNPS aircraft can operate in MNPS airspace, however, standard oceanic separation minima is provided between the non-MNPS aircraft and other traffic.

Minimum Obstruction Clearance Altitude (MOCA)

The MOCA is the lowest published altitude in effect between radio fixes on VOR airways, off-airway routes, or route segments that meets obstacle clearance requirements for the entire route segment. This altitude also assures acceptable navigational signal coverage only within 22 NM of a VOR.

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 obstruction clearance altitude (MOCA)

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 reception altitude (MRA)

The lowest altitude at which an airway intersection can be determined.

Minimum reception altitude (MRA)

The lowest altitude at which an airway intersection can be determined.

Minimum safe altitude (MSA)

The minimum altitude depicted on approach charts which provides at least 1,000 feet of obstacle clearance for emergency use within a specified distance from the listed navigation facility.

Minimum safe altitude (MSA)

The minimum altitude depicted on approach charts which provides at least 1,000 feet of obstacle clearance for emergency use within a specified distance from the listed navigation facility.

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 Vectoring Altitude (MVA)

Minimum vectoring altitude charts are developed for areas where there are numerous minimum vectoring altitudes due to variable terrain features or man-made obstacles. MVAs are established for use by ATC when radar ATC is exercised.

Minimum vectoring altitude (MVA)

An IFR altitude lower than the minimum en route altitude (MEA) that provides terrain and obstacle clearance.

Minimum vectoring altitude (MVA)

An IFR altitude lower than the minimum en route altitude (MEA) that provides terrain and obstacle clearance.

Minimums section

The area on an IAP chart that displays the lowest altitude and visibility requirements for the approach.

Minimums section

The area on an IAP chart that displays the lowest altitude and visibility requirements for the approach.

Minor alteration

An alteration other than a major alteration.

Minor Alteration

An alteration other than a major alteration. This includes alterations that are listed in the aircraft, aircraft engine, or propeller specifications.

Minor repair

A repair other than a major repair.

Missed approach

A maneuver conducted by a pilot when an instrument approach cannot be completed to a landing.

Missed approach

A maneuver conducted by a pilot when an instrument approach cannot be completed to a landing.

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.

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.

Missed Approach Waypoint (MAWP)

An approach waypoint sequenced during the missed approach procedure that is usually a fly-over waypoint, rather than a fly-by waypoint.

Mist

A popular expression for drizzle or heavy fog.

Mixed ice

A mixture of clear ice and rime ice.

Mixed ice

A mixture of clear ice and rime 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.

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 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.

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

A force that causes or tries to cause an object to rotate. It is indicated by the product of the weight of an item multiplied by its arm.

Moment

(GAMA) The product of the weight of an item multiplied by its arm. (Moment divided by a constant is used to simplify balance calculations by reducing the number of digits; see reduction factor.)

Moment

Moment Arm

The distance from a datum to the applied force.

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 Index (Or Index)

A moment divided by a constant such as 100, 1,000, or 10,000. The purpose of using a moment index is to simplify weight and balance computations of airplanes where heavy items and long arms result in large, unmanageable numbers.

Moment index (or index)

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.

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.

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.

Movable slat

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.

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.

Multimedia

A combination of more than one instructional medium. This format can include audio, text, graphics, animations, and video. Recently, multimedia implies a computer-based presentation.

Multiple-choice-type test item

A test item consisting of a question or statement followed by a list of alternative answers or responses.

Mushing

A flight condition caused by slow speed where the control surfaces are marginally effective.

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.

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.

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 (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 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 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.

Navigable airspace

Airspace at and above the minimum flight altitudes prescribed by or under this chapter, including airspace needed for safe takeoff and landing.

Navigate

To move between websites on the internet. Navigation is often accomplished by means of links or connections between sites.

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.

Negative Static Stability

The initial tendency of an aircraft to continue away from the original state of equilibrium after being disturbed.

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.

Neutral static stability

The initial tendency of an aircraft to remain in a new condition after its equilibrium has been disturbed.

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.

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.

No procedure turn (NoPT)

Term used with the appropriate course and altitude to denote that the procedure turn is not required.

No procedure turn (NoPT)

Term used with the appropriate course and altitude to denote that the procedure turn is not required.

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.

No-gyro approach

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.

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.

Nondirectional radio beacon (NDB)

A ground-based radio transmitter that transmits radio energy in all directions.

Nondirectional radio beacon (NDB)

A ground-based radio transmitter that transmits radio energy in all directions.

Nonprecision approach

A standard instrument approach procedure in which only horizontal guidance is provided.

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 glide slope is provided.

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 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.

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.

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.

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.

Objectivity

The singleness of scoring of a test; it does not reflect the biases of the person grading the test.

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 Clearance Surface (OCS)

An inclined or level surface associated with a defined area for obstruction evaluation.

Obstacle Departure Procedure (ODP)

A procedure that provides obstacle clearance. ODPs do not include ATC related climb requirements. In fact, the primary emphasis of ODP design is to use the least onerous route of flight to the en route structure while attempting to accommodate typical departure routes.

Obstacle departure procedures (ODP)

Obstacle clearance protection provided to aircraft in instrument meteorological conditions (IMC).

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 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 lights

Lights that can be found both on and off an airport to identify obstructions.

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).

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.

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).

Octane

The rating system of aviation gasoline with regard to its anti-detonating qualities.

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.

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

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.

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.

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.

Orographic

Of, pertaining to, or caused by mountains as in orographic clouds, orographic lift, or orographic precipitation.

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.

Outer marker

A marker beacon at or near the glide slope intercept altitude of an ILS approach. It is normally located four to seven miles from the runway threshold on the extended centerline of the runway.

Outer marker

A marker beacon at or near the glideslope intercept altitude of an ILS approach. It 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.

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.

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-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.

Parachute

A device used or intended to be used to retard the fall of a body or object through the air.

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.

Passenger

Any person on board an aircraft other than a crewmember, FAA personnel, manufacturer personnel required for type certification, or a person receiving or providing flight training, checking, or testing as authorized by this part.

Payload

(GAMA) Weight of occupants, cargo, and baggage.

Payload (GAMA)

The weight of occupants, cargo, and baggage.

Payload (GAMA)

The weight of occupants, cargo, and baggage.

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.

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.

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.

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 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 (PIC)

The pilot responsible for the operation and safety of an aircraft.

Pilot report (PIREP)

Report of meteorological phenomena encountered by aircraft.

Pilot report (PIREP)

Report of meteorological phenomena encountered by aircraft.

Pilot-in-command (PIC)

The pilot responsible for the operation and safety of an aircraft.

Pilotage

Navigation by visual reference to landmarks.

Pilotage

Navigation by visual reference to landmarks.

Pilot’s Operating Handbook (POH)

A document developed by the airplane manufacturer and contains the FAA approved Airplane Flight Manual (AFM) information.

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.

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 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.

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.

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.

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-in-space approach

A type of helicopter instrument approach procedure to a missed approach point more than 2,600 feet from an associated helicopter landing area.

Point-in-space approach

A type of helicopter instrument approach procedure to a missed approach point more than 2,600 feet from an associated helicopter landing area.

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.

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. ADM 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

Control 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

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.

Powerplant

A complete engine and propeller combination with accessories.

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)

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

Any or all forms of water particles (rain, sleet, hail, or snow) that fall from the atmosphere and reach the surface.

Precipitation attenuation

Reduction of power density because of absorption or reflection of energy by precipitation.

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

A standard instrument approach procedure in which both vertical and horizontal guidance is provided.

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)

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 glideslope will see two white lights and two red lights. See VASI.

Precision approach procedure

A standard instrument approach procedure in which an electronic glide slope is provided, such as ILS and PAR.

Precision approach radar (PAR)

A type of radar used at an airport to guide an aircraft through the final stages of landing, providing horizontal and vertical guidance. The radar operator directs the pilot to change heading or adjust the descent rate to keep the aircraft on a path that allows it to touch down at the correct spot on the runway.

Precision approach radar (PAR)

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.

Precision runway monitor (PRM)

System allows simultaneous, independent Instrument Flight Rules (IFR) approaches at airports with closely spaced parallel runways.

Precision runway monitor (PRM)

System allows simultaneous, independent instrument flight rules (IFR) approaches at airports with closely spaced parallel runways.

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.

Preferred IFR Routes

A system of preferred IFR routes guides you in planning your route of flight to minimize route changes during the operational phase of flight, and to aid in the efficient orderly management of air traffic using federal airways.

Preferred IFR routes

Routes established in the major terminal and en route environments to increase system efficiency and capacity. IFR clearances are issued based on these routes, listed in the A/FD except when severe weather avoidance procedures or other factors dictate otherwise.

Preferred IFR routes

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.

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

Altitude above the standard 29.92" Hg plane.

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 altitude

Altitude above the standard 29.92 "Hg plane.

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 is not necessarily 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 preservation operations and the replacement of small standard parts not involving complex assembly operations.

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 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 flight display (PFD)

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.

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

A maneuver prescribed when it is necessary to reverse direction to establish an aircraft on the intermediate approach segment or final approach course.

Procedure turn

A maneuver prescribed when it is necessary to reverse direction to establish an aircraft on the intermediate approach segment or final approach course.

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.

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.

Prohibited area

Designated airspace within which flight of aircraft is prohibited.

Prohibited area

A prohibited area is airspace designated under part 73 within which no person may operate an aircraft without the permission of the using agency.

Prohibited area

Designated airspace within which flight of aircraft is prohibited.

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

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.

Propeller/rotor modulation error

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.

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.

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).

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.

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.

Rabbit, the

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

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 beam

The focused energy radiated by radar similar to a flashlight or searchlight beam.

Radar services

Radar is a method whereby radio waves are transmitted into the air and are then received when they have been reflected by an object in the path of the beam. Range is determined by measuring the time it takes (at the speed of light) for the radio wave to go out to the object and then return to the receiving antenna. The direction of a detected object from a radar site is determined by the position of the rotating antenna when the reflected portion of the radio wave is received.

Radar summary chart

A weather product derived from the national radar network that graphically displays a summary of radar weather reports.

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.

Radials

The courses oriented from a station.

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 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 balloon-borne instrument for measuring pressure, temperature, and humidity aloft.

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.

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.

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 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.

Ramp Weight

The zero fuel weight plus all of the usable fuel on board.

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

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.

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 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.

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.

Record

See Database Record

Reduced vertical separation minimum (RVSM)

Reduces the vertical separation between flight level (FL) 290-410 from 2,000 feet to 1,000 feet and makes six additional FLs available for operation. Also see DRVSM.

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

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, distance circle)

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.

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 (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 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 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.

Relative wind

Relay question

Used in response to a student’s question, the student question is redirected to another student.

Reliability

The degree to which test results are consistent with repeated measurements.

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 communications outlet (RCO)

An unmanned communications facility that is remotely controlled by air traffic personnel.

Remote communications outlet (RCO)

An unmanned communications facility that is remotely controlled by air traffic personnel.

Remote scope

In radar meteorology a “slave” scope remoted from weather radar.

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.

Required Navigation Performance (RNP)

RNP is a statement of the navigation performance necessary for operation within a defined airspace. On-board monitoring and alerting is required.

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 specified level of accuracy defined by a lateral area of confined airspace in which an RNP-certified aircraft operates.

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.

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

A restricted area is airspace designated under 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.

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.

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.

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.

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.

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 icing (or rime ice)

The formation of a white or milky and opaque granular deposit of ice formed by the rapid freezing of supercooled water droplets as they impinge upon an exposed aircraft.

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 elements in ADM

Take into consideration the four fundamental risk elements: the pilot, the aircraft, the environment, and external pressures.

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.

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.

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 segment

A portion of a route bounded on each end by a fix or navigation aid (NAVAID).

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

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 lights

Runway lighting which consists of flush centerline lights spaced at 50-foot intervals beginning 75 feet from the landing threshold.

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 edge lights

A component of the runway lighting system that is used to outline the edges of runways at night or during low visibility conditions. These lights are classified according to the intensity they are capable of producing.

Runway End Identifier Lights (REIL)

One component of the runway lighting system. These lights are installed at many airfields to provide rapid and positive identification of the approach end of a particular 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 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 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 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 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 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 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)

The instrumentally derived horizontal distance a pilot should be able to see down the runway from the approach end, based on either the sighting of high-intensity runway lights, or the visual contrast of other objects.

Runway visual range (RVR)

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.

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.

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.

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.

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.

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.

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.

Scud

Small detached masses of stratus fractus clouds below a layer of higher clouds, usually nimbostratus.

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. Compare land breeze.

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 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 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.

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.

Segmented Circle

A visual ground based structure to provide traffic pattern information.

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.

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 highest altitude at which an aircraft can still maintain a steady rate of climb of 100 feet per minute.

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.

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.

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.

Shock Waves

A compression wave formed when a body moves through the air at a speed greater than the speed of sound.

Show

Unless the context otherwise requires, to show to the satisfaction of the Administrator.

Shower

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.

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 Point

[ICAO Annex 11] A specified geographical location used in defining an ATS route or the flight path of an aircraft and for other navigation and ATS purposes.

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.

Simplified directional facility (SDF)

Single Engine Absolute Ceiling

The altitude that a twin-engine airplane can no longer climb with one engine inoperative.

Single Engine Service Ceiling

The altitude that a twin-engine airplane can no longer climb at a rate greater then 50 f.p.m. 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.

Sites

Internet addresses which provide information and often are linked to other similar sites.

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.

Skin friction drag

Drag generated between air molecules and the solid surface of the aircraft.

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

Small aircraft

Aircraft of 12,500 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.

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

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.

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

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

Special Use Airspace Management System (SAMS)

A joint FAA and military program designed to improve civilian access to special use airspace by providing information on whether the airspace is active or scheduled to be active. The information is available to authorized users via an Internet website.

Special VFR conditions

Meteorological conditions that are less than those required for basic VFR flight in controlled airspace and in which some aircraft are permitted flight under visual flight rules.

Special VFR operations

Aircraft operating in accordance with clearances within controlled airspace in meteorological 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

The distance traveled in a given time.

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.

Spin

An aggravated stall that results in an airplane descending in a helical, or corkscrew path.

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.

Spoilers

Spool

A shaft in a turbine engine which drives one or more compressors with the power derived from one or more turbines.

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).

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.

St. Elmo’s Fire

A corona discharge which lights up the aircraft surface areas where maximum static discharge occurs.

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.

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.

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

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.

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

The atmosphere defined in U.S. Standard Atmosphere, 1962 (Geopotential altitude tables).

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) Weight of a standard airplane including unusable fuel, full operating fluids, and full oil.

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 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 holding pattern

A holding pattern in which all turns are made to the right.

Standard Instrument Departure (SID)

An ATC requested and developed departure route designed to increase capacity of terminal airspace, effectively control the flow of traffic with minimal communication, and reduce environmental impact through noise abatement procedures.

Standard instrument departure procedures (SIDS)

Published procedures to expedite clearance delivery and to facilitate transition between takeoff and en route operations.

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 service volume (SSV)

Defines the limits of the volume of airspace which the VOR serves.

Standard service volume (SSV)

Defines the limits of the volume of airspace which the VOR serves.

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 route (STAR)

A preplanned IFR ATC arrival procedure published for pilot use in graphic and/or textual form.

Standard terminal arrival route (STAR)

A preplanned IFR ATC arrival procedure published for pilot use in graphic and/or textual form.

Standard Weights

These have been established for numerous items involved in weight and balance computations. These weights should not be used if actual weights are available.

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 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.

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

(GAMA) A location along the airplane fuselage usually given in terms of distance from the reference datum.

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 is moving at a speed of less than 5 knots.

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

The point after which additional descent is permitted within a segment of an IAP.

Stepdown fix

The point after which additional descent is permitted within a segment of an IAP.

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.

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.

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.

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 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

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 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.

Sublimation

The change of (a) ice to water vapor or (b) water vapor to ice.

Sublimation

Process by which a solid is changed to a gas without going through the 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).

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.

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 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 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.

Swept Wing

A wing planform in which the tips of the wing are farther back than the wing root.

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 realistic display depiction of the aircraft in relation to terrain and flight path.

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

A realistic display depiction of the aircraft in relation to terrain and flight path.

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.

T-tail

An aircraft with the horizontal stabilizer mounted on the top of the vertical stabilizer, forming a T.

Tactical air navigation (TACAN)

An electronic navigation system used by military aircraft, providing both distance and direction information.

Tactical air navigation (TACAN)

An electronic navigation system used by military aircraft, providing both distance and direction information.

Tailwheel Aircraft

See Conventional landing Gear.

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 Runway Available (TORA)

ICAO defines TORA as the length of runway declared available and suitable for the ground run of an aeroplane takeoff.

Takeoff safety speed

A referenced airspeed obtained after lift-off at which the required one-engine-inoperative climb performance can be achieved.

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 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.

Task

Knowledge area, flight procedure, or maneuver within an area of operation in a practical test standard.

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.

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.

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.

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.

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 Arrival Area (TAA)

TAAs are the method by which aircraft are transitioned from the RNAV en route structure to the terminal area with minimal ATC interaction. The TAA consists of a designated volume of airspace designed to allow aircraft to enter a protected area, offering guaranteed obstacle clearance where the initial approach course is intercepted based on the location of the aircraft relative to the airport.

Terminal arrival area (TAA)

A procedure to provide a new transition method for arriving aircraft equipped with FMS and/or GPS navigational equipment. The TAA contains a T structure that normally provides a NoPT for aircraft using the approach.

Terminal arrival area (TAA)

A procedure to provide a new transition method for arriving aircraft equipped with FMS and/or GPS navigational equipment. The TAA contains a “T” structure that normally provides a NoPT for aircraft using the approach.

Terminal instrument approach procedure (TERP)

Prescribes standardized methods for use in designing instrument flight procedures.

Terminal Instrument Approach Procedure (TERP).

Prescribes standardized methods for use in designing instrument flight procedures.

Terminal radar service areas (TRSA)

Areas where participating pilots can receive additional radar services. The purpose of the service is to provide separation between all IFR operations and participating VFR aircraft.

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)

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.

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.

Threshold

The beginning of the part 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 crossing height (TCH)

The theoretical height above the runway threshold at which the aircraft’s glideslope antenna would be if the aircraft maintained the trajectory established by the mean ILS glideslope or MLS glidepath.

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

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.

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 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.

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.

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.

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 Elevation (TDZE)

The highest elevation in the first 3,000 feet of the landing surface.

Touchdown zone elevation (TDZE)

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 elevation (TDZE)

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 Lights

Two rows of transverse light bars disposed symmetrically about the runway centerline in the runway touchdown zone.

Touchdown zone lights

Two rows of transverse light bars disposed symmetrically about the runway centerline in the runway touchdown zone.

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 En Route Control (TEC)

The control of IFR en route traffic within delegated airspace between two or more adjacent approach control facilities, designed to expedite traffic and reduce control and pilot communication requirements.

Tower En Route Control (TEC)

Tower visibility

Prevailing VIsibility determined from the control tower.

Towering cumulus

A rapidly growing cumulus in which height exceeds width.

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.

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 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 midair collisions.

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 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)

An air traffic surveillance system that combines all available traffic information on a single display.

Traffic Management Advisor (TMA)

A software suite that helps air traffic controllers to sequence arriving air traffic.

Traffic pattern

The traffic flow that is prescribed for aircraft landing at, taxiing on, or taking off from, an airport.

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 learning

The ability to apply knowledge or procedures learned in one context to new contexts.

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.

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.

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 portion of the ATC radar beacon system.

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.

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 boundary layer between the troposphere and the mesosphere which acts as a lid to confine most of the water vapor, and the associated weather, to the troposphere.

Tropopause

The transition zone between the troposphere and stratosphere, usually characterized by an abrupt change of lapse rate.

Tropopause

The boundary layer between the troposphere and the mesosphere which acts as a lid to confine most of the water vapor, and the associated weather, to the troposphere.

Troposphere

The layer of the atmosphere extending from the surface to a height of 20,000 to 60,000 feet depending on latitude.

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.

Troposphere

The layer of the atmosphere extending from the surface to a height of 20,000 to 60,000 feet, depending on latitude.

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.

True airspeed

Actual airspeed, determined by applying a correction for pressure altitude and temperature to the CAS.

True airspeed

The airspeed of an aircraft relative to undisturbed air. True airspeed is equal to equivalent airspeed multiplied by (ρ0/ρ)1/2.

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 altitude

True wind direction

The direction, with respect to true north, from which the wind is blowing.

True-false test item

A test item consisting of a statement followed by an opportunity for the student to determine whether the statement is true or false.

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.

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.

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.

Turbofan engine

A fanlike turbojet engine designed to create additional thrust by diverting a secondary airflow around the combustion chamber.

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.

Turbojet engine

A turbine engine which produces its thrust entirely by accelerating the air through the engine.

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.

Turboprop engine

A turbine engine which drives a propeller through a reduction gearing arrangement. Most of the energy in the exhaust gases is converted into torque, rather than using its acceleration to drive 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 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.

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.

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).

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.

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.

Ultra-high frequency (UHF)

The range of electromagnetic frequencies between 962 MHz and 1213 MHz.

Ultra-high frequency (UHF)

The range of electromagnetic frequencies between 962 MHz and 1213 MHz.

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.

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 non-government air/ground radio communication station which may provide airport information at public use airports where there is no tower or FSS.

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.

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.

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.

Unusable Fuel

(GAMA) Fuel remaining after a runout test has been completed in accordance with governmental regulations.

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.

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

(GAMA) Difference between takeoff weight, or ramp weight if applicable, and basic empty weight.

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.

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.

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.

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-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.

V-tail

Validity

The extent to which a test measures what it is supposed to measure.

Vapor Lock

A condition in which air enters the fuel system and it may be difficult, or impossible, to restart the engine. Vapor lock may occur as a result of running a fuel tank completely dry, allowing air to enter the fuel system. On fuel-injected engines, the fuel may become so hot it vaporizes in the fuel line, not allowing fuel to reach the cylinders.

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.

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.

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).

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.

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 Navigation Planning

Included within certain STARs is information provided to help you reduce the amount of low altitude flying time for high performance aircraft, like jets and turboprops. An expected altitude is given for a key fix along the route. By knowing an intermediate altitude in advance when flying a high performance aircraft, you can plan the power or thrust settings and aircraft configurations that result in the most efficient descent, in terms of time, fuel requirements, and engine wear.

Vertical Speed Indicator (VSI)

An instrument that uses static pressure to display a rate of climb or descent in feet per minute. The VSI can also sometimes be called a vertical velocity indicator (VVI).

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 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 (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.

Vestibule

The central cavity of the bony labyrinth of the ear, or the parts of the membranous labyrinth that it contains.

VFR on top

ATC authorization for an IFR aircraft to operate in VFR conditions at any appropriate VFR altitude.

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 over-the-top

With respect to the operation of aircraft, the operation of an aircraft over-the-top under VFR when it is not being operated on an IFR flight plan.

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 Terminal Area Charts (1:250,000)

Depict 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 which includes 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.

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

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.

Visual Approach

A visual approach is an ATC authorization for an aircraft on an IFR flight plan to proceed visually to the airport of intended landing; it is not an IAP. Also, there is no missed approach segment. When it is operationally beneficial, ATC may authorize pilots to conduct a visual approach to the airport in lieu of the published IAP. A visual approach can be initiated by a pilot or the controller.

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 the Airport (VCOA)

An option to allow an aircraft to climb over the airport with visual reference to obstacles to attain a suitable altitude from which to proceed with an IFR departure.

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 descent point (VDP)

Visual Flight Rules (VFR)

Code of Federal Regulations that govern the procedures for conducting flight under visual conditions.

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 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.

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.

Vortex

In meteorology, any rotary flow in the atmosphere.

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.

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.

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.

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.

Vy

Best rate-of-climb speed. This airspeed provides the most altitude gain in a given period of time.

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.

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.

Wake turbulence

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

The boundary area formed when a warm air mass contacts and flows over a colder air mass. Warm fronts cause low ceilings and rain.

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.

Warning area

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.

Waste gate

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 designated geographical location used for route definition or progress-reporting purposes and is defined in terms of latitude/longitude coordinates.

Waypoint

A designated geographical location used for route definition or progress-reporting purposes and is defined in terms of latitude/longitude coordinates.

Waypoint (WP)

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.

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.

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 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.

Wheelbarrowing

A condition caused when forward yoke or stick pressure during takeoff or landing causes the aircraft to ride on the nosewheel alone.

Whirlwind

A small, rotating column of air; may be visible as a dust devil.

Wide Area Augmentation System (WAAS)

A method of navigation based on GPS. Ground correction stations transmit position corrections that enhance system accuracy and add vertical navigation (VNAV) features.

Wide area augmentation system (WAAS)

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

Correction applied to the course to establish a heading so that track will coincide with course.

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 direction indicators

Indicators that include a wind sock, wind tee, or tetrahedron. Visual reference will determine wind direction and runway in use.

Wind Shear

A sudden, drastic shift in windspeed, direction, or both that may occur in the horizontal or vertical plane.

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 sudden, drastic shift in windspeed, direction, or both that may occur in the horizontal or vertical plane.

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 area

The total surface of the wing (in 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 span

The maximum distance from wingtip to wingtip.

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.

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.

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

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.

Zero Fuel Weight

The weight of the aircraft to include all useful load except fuel.

Zero Fuel Weight

The weight of an aircraft without 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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