Aeronautical Terms
14 CFR–Title 14 of the Code of Federal Regulations
The federal aviation regulations governing the operation of aircraft, airways, and airmen.
A-RNAV
Advanced Area Navigation
A.C.
Alternating Current.
A/FD
Airport/Facility Directory—obsolete. Changed to Chart Supplement.
Abbreviated IFR Flight Plans
An authorization by ATC requiring pilots to submit only that information needed for the purpose of ATC. It includes only a small portion of the usual IFR flight plan information. In certain instances, this may be only aircraft identification, location, and pilot request. Other information may be requested if needed by ATC for separation/control purposes. It is frequently used by aircraft which are airborne and desire an instrument approach or by aircraft which are on the ground and desire a climb to VFR-on-top.
Abeam 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 altitude
The actual distance between an aircraft and the terrain over which it is flying.
Absolute pressure
Pressure measured from the reference of zero pressure, or a vacuum.
AC
Advisory Circular
ACAS
Airborne Collision Avoidance System
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 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.
ADF
Automatic Direction Finder.
ADI
Attitude Director Indicator.
ADM
Aeronautical Decision-Making.
ADS
Automatic Dependent Surveillance
ADSB
Automatic Dependent Surveillance Broadcast.
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.
AER
Approach End of Runway
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.
AFM
Airplane Flight Manual or Aircraft Flight Manual
AFSS
Automated Flight Service Station
AGL
Above Ground Level
Agonic line
An irregular imaginary line across the surface of the Earth along which the magnetic and geographic poles are in alignment, and along which there is no magnetic variation.
AIM
Aeronautical Information Manual
AIP
Aeronautical Information Publication
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 route surveillance radar (ARSR)
Air route traffic control center (ARTCC) radar used primarily to detect and display an aircrafts position while en route between terminal areas.
Air Route Traffic Control Center (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 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 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.
Aircraft Approach Category
A grouping of aircraft based on a speed of 1.3 times the stall speed in the landing configuration at maximum gross landing weight. An aircraft must fit in only one category. If it is necessary to maneuver at speeds in excess of the upper limit of a speed range for a category, the minimums for the category for that speed must be used. For example, an aircraft which falls in Category A, but is circling to land at a speed in excess of 91 knots, must use the approach Category B minimums when circling to land. The categories are A-E.
AIRMET
Inflight weather advisory issued as an amendment to the area forecast, concerning weather phenomena of operational interest to all aircraft and that is potentially hazardous to aircraft with limited capability due to lack of equipment, instrumentation, or pilot qualifications.
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 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 surveillance radar (ASR)
Approach control radar used to detect and display an aircrafts position in the terminal area.
Airport surveillance radar approach
An instrument approach in which ATC issues instructions for pilot compliance based on aircraft position in relation to the final approach course and the distance from the end of the runway as displayed on the controllers radar scope.
Airport/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.
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.
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.
AIS
Airmen’s Information System
ALAR
Approach and Landing Accident Reduction
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.
ALS
Approach Lighting System.
ALSF-1
Approach Light System With Sequenced Flashing Lights In ILS CAT-I Configuration
ALSF-2
Approach Light System With Sequenced Flashing Lights In ILS Cat-II Configuration. The ALSF-2 May Operate As An SSALR When Weather Conditions Permit
Alternate 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 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.
Altimeter
An instrument which determines the altitude of an object with respect to a fixed level. A pressure altimeter.
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.
AMASS
Airport Movement Area Safety System
AME
Aviation Medical Examiner.
Amendment status
The circulation date and revision number of an instrument approach procedure, printed above the procedure identification.
Ammeter
An instrument installed in series with an electrical load used to measure the amount of current flowing through the load.
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 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.
Angle of attack
The acute angle formed between the chord line of an airfoil and the direction of the air striking the airfoil.
ANP
Actual Navigation Performance
ANR
Advanced Navigation Route
Anti-ice
Preventing the accumulation of ice on an aircraft structure via a system designed for that purpose.
AOA
Airport Operating Area
AP
Autopilot System
Approach Clearance
Authorization by ATC for a pilot to conduct an instrument approach. The type of instrument approach for which a clearance and other pertinent information is provided in the approach clearance when required.
Approach End of Runway (AER)
The first portion of the runway available for landing. If the runway threshold is displaced, use the displaced threshold latitude/longitude as the AER.
Approach Fix
From a database coding standpoint, an approach fix is considered to be an identifiable point in space from the intermediate fix (IF) inbound. A fix located between the initial approach fix (IAF) and the IF is considered to be associated with the approach transition or feeder route.
Approach Gate
An imaginary point used by ATC to vector aircraft to the final approach course. The approach gate is established along the final approach course 1 NM from the final approach fix (FAF) on the side away from the airport and is located no closer than 5 NM from the landing threshold.
Approach Light System (ALS)
An airport lighting facility which provides visual guidance to landing aircraft by radiating light beams in a directional pattern by which the pilot aligns the aircraft with the extended centerline of the runway on his/her final approach for landing. Condenser-Discharge Sequential Flashing Lights/Sequenced Flashing Lights may be installed in conjunction with the ALS at some airports. Types of Approach Light Systems are: ALSF-1, ALSF-2, SSALF, SSALR, MALSF, MALSR, LDIN, RAIL, ODALS.
Appropriate Obstacle Clearance Minimum Altitude
Any of the following: Minimum En Route IFR Altitude, Minimum IFR Altitude, Minimum Obstruction Clearance Altitude, Minimum Vectoring Altitude.
Appropriate Terrain Clearance Minimum Altitude
Any of the following: Minimum En Route IFR Altitude, Minimum IFR Altitude, Minimum Obstruction Clearance Altitude, Minimum Vectoring Altitude.
APV
Approach With Vertical Guidance
Arc
The track over the ground of an aircraft flying at a constant distance from a navigational aid by reference to distance measuring equipment (DME).
Area chart
Part of the low-altitude en route chart series, this chart furnishes terminal data at a larger scale for congested areas.
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.
ARSR
Air Route Surveillance Radar.
ARTCC
Air Route Traffic Control Center.
ARTS
Automated Radar Terminal System
ASDA
Accelerate-Stop Distance Available
ASDAR
Aircraft To Satellite Data Relay
ASDE
Airport Surface Detection Equipment.
ASDE-3
Airport Surface Detection Equipment-3
ASDE-X
Airport Surface Detection Equipment-X
ASOS
Automated Surface Observing Station.
ASR
Airport Surveillance Radar.
ATC
Air Traffic Control.
ATC-TFM
Air Traffic Control Traffic Flow Management
ATCRBS
Air Traffic Control Radar Beacon System.
ATCSCC
Air Traffic Control System Command Center
ATCT
Airport Traffic Control Tower
ATD
Along-Track Distance
ATIS
Automatic Terminal Information Service.
ATM
Air Traffic Management
Atmospheric propagation delay
A bending of the electromagnetic (EM) wave from the satellite that creates an error in the GPS system.
ATS
Air Traffic Service
ATT
Attitude Retention System
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 indicator
The foundation for all instrument flight, this instrument reflects the airplanes attitude in relation to the horizon.
Attitude instrument flying
Controlling the aircraft by reference to the instruments rather than by outside visual cues.
Autokinesis
Nighttime visual illusion that a stationary light is moving, which becomes apparent after several seconds of staring at the light.
Autoland Approach
An autoland approach is a precision instrument approach to touchdown and, in some cases, through the landing rollout. An autoland approach is performed by the aircraft autopilot which is receiving position information and/or steering commands from onboard navigation equipment. Note: Autoland and coupled approaches are flown in VFR and IFR. It is common for carriers to require their crews to fly coupled approaches and autoland approaches (if certified) when the weather conditions are less than approximately 4,000 RVR.
Automated 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)/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 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 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 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 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.
Aviation medical examiner (AME)
A physician with training in aviation medicine designated by the Civil Aerospace Medical Institute (CAMI).
AVN
Office of Aviation System Standards
AWOS
Automated Weather Observing System.
AWSS
Automated Weather Sensor System
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.
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-VNAV
Barometric Vertical Navigation
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.
BC
Back Course.
Below Minimums
Weather conditions below the minimums prescribed by regulation for the particular action involved; e.g., landing minimums, takeoff minimums.
Block altitude
A block of altitudes assigned by ATC to allow altitude deviations; for example, Maintain block altitude 9 to 11 thousand.
BRITE
Bright Radar Indicator Tower Equipment
Cage
The black markings on the ball instrument indicating its neutral position.
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 orifice
A hole of specific diameter used to delay the pressure change in the case of a vertical speed indicator.
Call For Release
Wherein the overlying ARTCC requires a terminal facility to initiate verbal coordination to secure ARTCC approval for release of a departure into the en route environment.
CARF
Central Altitude Reservation Function
CAS
Calibrated Airspeed.
CAT
Category
CAT II
Category II.
Catch Point
A fix/waypoint that serves as a transition point from the high altitude waypoint navigation structure to an arrival procedure (STAR) or the low altitude ground-based navigation structure.
CDI
Course Deviation Indicator.
CDM
Collaborative Decision Making
CDR
Coded Departure Routes. Predefined routes used to route air traffic around areas of severe weather.
CDTI
Cockpit Display of Traffic Information
CDU
Control Display Unit
CENRAP
Center Radar Arts Processing
CFIT
Controlled Flight Into Terrain
CFR
Code of Federal Regulations
CFR
Call For Release
CGD
Combined Graphic Display
Changeover Point (COP)
A COP indicates the point where a frequency change is necessary between navigation aids when other than the midpoint on an airway, to receive course guidance from the facility ahead of the aircraft instead of the one behind. These COPs divide an airway or route segment and ensure continuous reception of navigational signals at the prescribed minimum en route IFR altitude.
Charted Visual Flight Procedure Approach
An approach conducted while operating on an instrument flight rules (IFR) flight plan which authorizes the pilot of an aircraft to proceed visually and clear of clouds to the airport via visual landmarks and other information depicted on a charted visual flight procedure. This approach must be authorized and under the control of the appropriate air traffic control facility. Weather minimums required are depicted on the chart.
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.
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 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 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 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 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.
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 ice
Glossy, clear, or translucent ice formed by the relatively slow freezing of large, supercooled water droplets.
Clearance
ATC permission for an aircraft to proceed under specified traffic conditions within controlled airspace, for the purpose of providing separation between known aircraft.
Clearance delivery
Control tower position responsible for transmitting departure clearances to IFR flights.
Clearance limit
The fix, point, or location to which an aircraft is cleared when issued an air traffic clearance.
Clearance on request
An IFR clearance not yet received after filing a flight plan.
Clearance void 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.
CNF
Computer Navigation Fix
CNS
Communication,Navigation, and Surveillance
Columns
See Database Columns
Common Route
Typically the portion of a RNAV STAR between the en route transition end point and the runway transition start point; however, the common route may only consist of a single point that joins the en route and runway transitions.
Compass course
A true course corrected for variation and deviation errors.
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.
Comply With Restrictions
An ATC instruction that requires an aircraft being vectored back onto an arrival or departure procedure to comply with all altitude and/or speed restrictions depicted on the procedure. This term may be used in lieu of repeating each remaining restriction that appears on the procedure.
Composite Flight Plan
A flight plan which specifies VFR operation for one portion of flight and IFR for another portion. It is used primarily in military operations.
Compulsory Reporting Points
Reporting points which must be reported to ATC. They are designated on aeronautical charts by solid triangles or filed in a flight plan as fixes selected to define direct routes. These points are geographical locations which are defined by navigation aids/fixes. Pilots should discontinue position reporting over compulsory reporting points when informed by ATC that their aircraft is in “radar contact.”
Computer navigation fix
A point used to define a navigation track for an airborne computer system such as GPS or FMS.
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.
Cone of confusion
A cone-shaped volume of airspace directly above a VOR station where no signal is received, causing the CDI to fluctuate.
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.
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 pressures
The amount of physical exertion on the control column necessary to achieve the desired attitude.
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 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.
Convective SIGMET
Weather advisory concerning convective weather significant to the safety of all aircraft, including thunderstorms, hail, and tornadoes.
Coordinated flight
Flight with a minimum disturbance of the forces maintaining equilibrium, established via effective control use.
COP
Changeover Point.
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.
COTS
Commercial Off The Shelf
Coupled Approach
A coupled approach is an instrument approach performed by the aircraft autopilot which is receiving position information and/or steering commands from onboard navigation equipment. In general, coupled nonprecision approaches must be discontinued and flown manually at altitudes lower than 50 feet below the minimum descent altitude, and coupled precision approaches must be flown manually below 50 feet AGL. Note: Coupled and autoland approaches are flown in VFR and IFR. It is common for carriers to require their crews to fly coupled approaches and autoland approaches (if certified) when the weather conditions are less than approximately 4,000 RVR.
Course Controlled Airspace
A. The intended direction of flight in the horizontal plane measured in degrees from north. B. The ILS localizer signal pattern usually specified as the front course or the back course. C. The intended track along a straight, curved, or segmented MLS path.
CPDLC
Controller Pilot Data Link Communications
CRC
Cyclic Redundancy Check
CRCT
Collaborative Routing Coordination Tool
Crew resource management (CRM)
The effective use of all available resources human, hardware, and information.
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.
CRM
Crew Resource Management.
Cross (Fix) At (Altitude)
Used by ATC when a specific altitude restriction at a specified fix is required.
Cross (Fix) At Or Above (Altitude)
Used by ATC when an altitude restriction at a specified fix is required. It does not prohibit the aircraft from crossing the fix at a higher altitude than specified; however, the higher altitude may not be one that will violate a succeeding altitude restriction or altitude assignment.
Cross (Fix) At Or Below (Altitude)
Used by ATC when a maximum crossing altitude at a specific fix is required. It does not prohibit the aircraft from crossing the fix at a lower altitude; however, it must be at or above the minimum IFR altitude.
Cross-check
The first fundamental skill of instrument flight, also known as scan, the continuous and logical observation of instruments for attitude and performance information.
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.
CTAF
Common Traffic Advisory Frequency
CTD
Controlled Time of Departure
Current Flight Plan [ICAO]
The flight plan, including changes, if any, brought about by subsequent clearances.
Current Plan
The ATC clearance the aircraft has received and is expected to fly.
CVFP
Charted Visual Flight Procedure
D.C.
Direct Current.
DA
Decision Altitude.
DACS
Digital Aeronautical Chart Supplement
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.
DBRITE
Digital Bright Radar Indicator Tower Equipment
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 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.
Deice
The act of removing ice accumulation from an aircraft structure.
Delay Indefinite (Reason If Known) Expect Further Clearance
Used by ATC to inform a pilot when an accurate estimate of the delay time and the reason for the delay cannot immediately be determined; e.g., a disabled aircraft on the runway, terminal or center area saturation, weather below landing minimums, etc.
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.
DER
Departure End of The Runway
Descend Via
A descend via clearance instructs you to follow the altitudes published on a STAR. You are not authorized to leave your last assigned altitude unless specifically cleared to do so. If ATC amends the altitude or route to one that is different from the published procedure, the rest of the charted descent procedure is canceled. ATC will assign you any further route, altitude, or airspeed clearances, as necessary.
Deviation
A magnetic compass error caused by local magnetic fields within the aircraft. Deviation error is different on each heading.
Deviations
A. A departure from a current clearance, such as an off course maneuver to avoid weather or turbulence.
B. Where specifically authorized in the CFRs and requested by the pilot, ATC may permit pilots to deviate from certain regulations.
DF Approach Procedure
Used under emergency conditions where another instrument approach procedure cannot be executed. DF (Direction Finding) guidance for an instrument approach is given by ATC facilities with DF capability.
DGPS
Differential Global Positioning System.
DH
Decision Height
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.
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.
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 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.
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.
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
Distance Measuring Equipment.
DME arc
A flight track that is a constant distance from the station or waypoint.
DME/N
Standard DME
DME/P
Precision DME
Doghouse
A turn-and-slip indicator dial mark in the shape of a doghouse.
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.
DP
Departure Procedure.
DPs
Departure Procedures
Drag
The net aerodynamic force parallel to the relative wind, usually the sum of two components: induced drag and parasite drag.
Drag curve
The curve created when plotting induced drag and parasite drag.
Drift Angle
Angle between heading and track.
DRT
Diversion Recovery Tool
DRVSM
Domestic Reduced Vertical Separation Minimums
DSR
Display System Replacement
DUATS
Direct User Access Terminal System (shut down May 16, 2018).
Duplex
Transmitting on one frequency and receiving on a separate frequency.
DVA
Diverse Vector Area
DVRSN
Diversion
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.
EDCT
Expect Departure Clearance Time
Eddy currents
Current induced in a metal cup or disc when it is crossed by lines of flux from a moving magnet.
EFAS
En Route Flight Advisory Service.
EFB
Electronic Flight Bag
EFC
Expect-Further-Clearance.
EFIS
Electronic Flight Information System
EFV
Enhanced Flight Visibility
EFVS
Enhanced Flight Vision System.
EGPWS
Enhanced Ground Proximity Warning Systems
EICAS
Engine Indicating and Crew Alerting System
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.)
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 Safe Altitudes
Altitudes depicted on approach charts which provide at least 1,000 feet of obstacle clearance in nonmountainous areas and 2,000 feet of obstacle clearance in designated mountainous areas within a 100-mile radius of the navigation facility upon which the procedure is predicated and normally used only in military procedures. These altitudes are identified on published procedures as “Emergency Safe Altitudes.”
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.
En Route Air Traffic Control Services
Air traffic control service provided aircraft on IFR flight plans, generally by centers, when these aircraft are operating between departure and destination terminal areas. When equipment, capabilities, and controller workload permit, certain advisory/assistance services may be provided to VFR aircraft.
En Route Automation System (EAS)
The complex integrated environment consisting of situation display systems, surveillance systems and flight data processing, remote devices, decision support tools, and the related communications equipment that form the heart of the automated IFR air traffic control system. It interfaces with automated terminal systems and is used in the control of en route IFR aircraft.
En Route Charts
Aeronautical Chart.
En Route Descent
Descent from the en route cruising altitude which takes place along the route of flight.
En route facilities ring
Depicted in the plan view of IAP charts, a circle which designates NAVAIDs, fixes, and intersections that are part of the en route low altitude airway structure.
En Route Flight Advisory Service (EFAS)
An en route weather-only AFSS service.
En Route High Altitude Charts
Provide aeronautical information for en route instrument navigation (IFR) in the high altitude stratum. Information includes the portrayal of jet routes, identification and frequencies of radio aids, selected airports, distances, time zones, special use airspace, and related information.
En route high-altitude charts
Aeronautical charts for en route instrument navigation at or above 18,000 feet MSL.
En route low-altitude charts
Aeronautical charts for en route IFR navigation below 18,000 feet MSL.
En Route Minimum Safe Altitude Warning
A function of the EAS that aids the controller by providing an alert when a tracked aircraft is below or predicted by the computer to go below a predetermined minimum IFR altitude (MIA).
En Route Obstacle Clearance Areas
Obstacle clearance areas for en route planning are identified as primary, secondary, and turning areas, and they are designed to provide obstacle clearance route protection width for airways and routes.
En Route Transition
A. Conventional STARs/SIDs. The portion of a SID/STAR that connects to one or more en route airway/jet route.
B. RNAV STARs/SIDs. The portion of a STAR preceding the common route or point, or for a SID the portion following, that is coded for a specific en route fix, airway or jet route.
Encoding altimeter
A special type of pressure altimeter used to send a signal to the air traffic controller on the ground, showing the pressure altitude the aircraft is flying.
EPE
Estimated Position Error
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.
Estimated Elapsed Time [ICAO]
The estimated time required to proceed from one significant point to another.
Estimated Off-Block Time [ICAO]
The estimated time at which the aircraft will commence movement associated with departure.
Estimated Position Error (EPE)
A measure of the current estimated navigational performance. Also referred to as Actual Navigation Performance (ANP).
ETA
Estimated Time of Arrival
EWINS
Enhanced Weather Information System
Execute Missed Approach
Instructions issued to a pilot making an instrument approach which means continue inbound to the missed approach point and execute the missed approach procedure as described on the Instrument Approach Procedure Chart or as previously assigned by ATC. The pilot may climb immediately to the altitude specified in the missed approach procedure upon making a missed approach. No turns should be initiated prior to reaching the missed approach point. When conducting an ASR or PAR approach, execute the assigned missed approach procedure immediately upon receiving instructions to “execute missed approach.”
Expanded Service Volume
When ATC or a procedures specialist requires the use of a NAVAID beyond the limitations specified for standard service volume, an expanded service volume (ESV) may be established. See standard service volume.
Expect (Altitude) At (Time) Or (Fix)
Used under certain conditions to provide a pilot with an altitude to be used in the event of two-way communications failure. It also provides altitude information to assist the pilot in planning.
Expect Further Clearance (Time)
The time a pilot can expect to receive clearance beyond a clearance limit.
Expect Further Clearance Via (Airways, Routes Or Fixes)
Used to inform a pilot of the routing he/she can expect if any part of the route beyond a short range clearance limit differs from that filed.
Expedite
Used by ATC when prompt compliance is required to avoid the development of an imminent situation. Expedite climb/descent normally indicates to a pilot that the approximate best rate of climb/descent should be used without requiring an exceptional change in aircraft handling characteristics.
FAF
Final Approach Fix.
False horizon
Inaccurate visual information for aligning the aircraft, caused by various natural and geometric formations that disorient the pilot from the actual horizon.
FAP
Final Approach Point
FB
Fly-By
FBWP
Fly-By Waypoint
FD
Winds and Temperatures Aloft Forecast
FDP
Flight Data Processing
Federal airways
Class E airspace areas that extend upward from 1,200 feet to, but not including, 18,000 feet MSL, unless otherwise specified.
Feeder facilities
Used by ATC to direct aircraft to intervening fixes between the en route structure and the initial approach fix.
Feeder Fix
The fix depicted on Instrument Approach Procedure Charts which establishes the starting point of the feeder route.
Feeder Route
A feeder route is a route depicted on IAP charts to designate courses for aircraft to proceed from the en route structure to the IAF. Feeder routes, also referred to as approach transitions, technically are not considered approach segments but are an integral part of many IAPs.
Final
Commonly used to mean that an aircraft is on the final approach course or is aligned with a landing area.
Final approach
Part of an instrument approach procedure in which alignment and descent for landing are accomplished.
Final Approach
The segment between the final approach fix or point and the runway, airport, or missed approach point.
Final Approach Course
A bearing/radial/track of an instrument approach leading to a runway or an extended runway centerline all without regard to distance.
Final Approach Fix
The fix from which the final approach (IFR) to an airport is executed and which identifies the beginning of the final approach segment. It is designated on Government charts by the Maltese Cross symbol for nonprecision approaches and the lightning bolt symbol for precision approaches; or when ATC directs a lower-than-published glideslope/path intercept altitude, it is the resultant actual point of the glideslope/path intercept.
Final Approach Point
The point, applicable only to a nonprecision approach with no depicted FAF (such as an on airport VOR), where the aircraft is established inbound on the final approach course from the procedure turn and where the final approach descent may be commenced. The FAP serves as the FAF and identifies the beginning of the final approach segment.
Final Approach Segment
Segments Of An Instrument Approach Procedure.
Final Approach [ICAO]
That part of an instrument approach procedure which commences at the specified final approach fix or point, or where such a fix or point is not specified. a. At the end of the last procedure turn, base turn or inbound turn of a racetrack procedure, if specified; or b. At the point of interception of the last track specified in the approach procedure; and ends at a point in the vicinity of an aerodrome from which: 1. A landing can be made; or 2. A missed approach procedure is initiated.
FIR
Flight Information Region
FIS
Flight Information System
FIS-B
Flight Information Service Broadcast
FISDL
Flight Information Services Data Link
Fix
A geographical position determined by visual reference to the surface, by reference to one or more radio NAVAIDs, by celestial plotting, or by another navigational device. Note:Fix is a generic name for a geographical position and is referred to as a fix, waypoint, intersection, reporting point, etc.
Fixating
Staring at a single instrument, thereby interrupting the cross-check process.
FL
Flight Level.
Flag
A warning device incorporated in certain airborne navigation and flight instruments indicating that: a. Instruments are inoperative or otherwise not operating satisfactorily, or b. Signal strength or quality of the received signal falls below acceptable values.
Flight configurations
Adjusting the aircraft control surfaces (including flaps and landing gear) in a manner that will achieve a specified attitude.
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 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 Inspection
Inflight investigation and evaluation of a navigational aid to determine whether it meets established tolerances.
Flight Level (FL)
A flight level is a level of constant atmospheric pressure related to a reference datum of 29.92 in.Hg. Each flight level is stated in three digits that represents hundreds of feet. For example, FL 250 represents an altimeter indication of 25,000 feet.
Flight management system (FMS)
Provides pilot and crew with highly accurate and automatic long-range navigation capability, blending available inputs from long- and short- range sensors.
Flight 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 strips
Paper strips containing instrument flight information, used by ATC when processing flight plans.
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.
Fly Visual To Airport
Published Instrument Approach Procedure Visual Segment.
Fly-By (FB) Waypoint
A waypoint that requires the use of turn anticipation to avoid overshooting the next flight segment.
Fly-Over (FO) Waypoint
A waypoint that precludes any turn until the waypoint is overflown, and is followed by either an intercept maneuver of the next flight segment or direct flight to the next waypoint.
FMC
Flight Management Computer
FMS
Flight Management System.
FO
Fly-Over
FOM
Flight Operations Manual
Four Corner Post Configuration
An arrangement of air traffic pathways in a terminal area that brings incoming flights over fixes at four corners of the traffic area, while outbound flights depart between the fixes, thus minimizing conflicts between arriving and departing traffic.
FOWP
Fly-Over Waypoint
FPM
Feet Per Minute
FPNM
Feet Per Nautical Mile
FSDO
Flight Standards District Office
FSS
Flight Service Station
FTD
Flight Training Device.
FTE
Flight Technical Error
Fundamental skills
Pilot skills of instrument cross-check, instrument interpretation, and aircraft control.
G/S
Glide Slope
GAMA
General Aviation Manufacturers Association
Gateway Fix
A navigational aid or fix where an aircraft transitions between the domestic route structure and the oceanic route airspace.
GBT
Ground-Based Transmitter
GCA
Ground Controlled Approach
GCO
Ground Communication Outlet
GDP
Ground Delay Programs
GDPE
Ground Delay Program Enhancements
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.
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 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).
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.
Global landing system (GLS)
An instrument approach with lateral and vertical guidance with integrity limits (similar to barometric vertical navigation (BRO VNAV).
Global Navigation Satellite System (GNSS)
An umbrella term adopted by the International Civil Aviation Organization (ICAO) to encompass any independent satellite navigation system used by a pilot to perform onboard position determinations from the satellite data.
Global positioning system (GPS)
Navigation system that uses satellite rather than ground-based transmitters for location information.
GLS
Global Navigation Satellite System Landing System
GNE
Gross Navigation Error
GNSS
Global Navigation Satellite Systems.
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.
GPS
Global Positioning System.
GPS Approach Overlay Program
An authorization for pilots to use GPS avionics under IFR for flying designated existing nonprecision instrument approach procedures, with the exception of LOC, LDA, and SDF procedures.
GPWS
Ground Proximity Warning System
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.
Ground Controlled Approach
A radar approach system operated from the ground by air traffic control personnel transmitting instructions to the pilot by radio. The approach may be conducted with surveillance radar (ASR) only or with both surveillance and precision approach radar (PAR). Usage of the term “GCA” by pilots is discouraged except when referring to a GCA facility. Pilots should specifically request a “PAR” approach when a precision radar approach is desired or request an “ASR” or “surveillance” approach when a nonprecision radar approach is desired.
Ground 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.
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.
GS
Glide Slope.
GS
Groundspeed
GWPS
Ground Proximity Warning System.
GWS
Graphical Weather Service
HAA
Height Above Airport.
HAL
Height Above Landing.
HAT
Height Above Touchdown Elevation.
Hazardous attitudes
Five aeronautical decision-making attitudes that may contribute to poor pilot judgment: antiauthority, 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.
Head-Up Display (HUD)
See Head-Up Guidance System (HGS)
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 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.
Height Above Airport
The height of the Minimum Descent Altitude above the published airport elevation. This is published in conjunction with circling minimums.
Height Above Touchdown
The height of the Decision Height or Minimum Descent Altitude above the highest runway elevation in the touchdown zone (first 3,000 feet of the runway). HAT is published on instrument approach charts in conjunction with all straight-in minimums.
Height above touchdown elevation (HAT)
The DA/DH or MDA above the highest runway elevation in the touchdown zone (first 3,000 feet of the runway).
HEMS
Helicopter Emergency Medical Service
HF
High Frequency.
HFDL
High Frequency Data Link
Hg
Abbreviation for mercury, from the Latin hydrargyrum.
HIRL
High Intensity Runway Lights
HITS
Highway In The Sky
HIWAS
Hazardous Inflight Weather Advisory Service. Discontinued on January 8, 2020.
Hold For Release
Used by ATC to delay an aircraft for traffic management reasons; i.e., weather, traffic volume, etc. Hold for release instructions (including departure delay information) are used to inform a pilot or a controller (either directly or through an authorized relay) that an IFR departure clearance is not valid until a release time or additional instructions have been received.
Hold In Lieu Of Procedure Turn
A hold in lieu of procedure turn shall be established over a final or intermediate fix when an approach can be made from a properly aligned holding pattern. The hold in lieu of procedure turn permits the pilot to align with the final or intermediate segment of the approach and/or descend in the holding pattern to an altitude that will permit a normal descent to the final approach fix altitude. The hold in lieu of procedure turn is a required maneuver (the same as a procedure turn) unless the aircraft is being radar vectored to the final approach course, when “NoPT” is shown on the approach chart, or when the pilot requests or the controller advises the pilot to make a “straight-in” approach.
Hold Procedure
A predetermined maneuver which keeps aircraft within a specified airspace while awaiting further clearance from air traffic control. Also used during ground operations to keep aircraft within a specified area or at a specified point while awaiting further clearance from air traffic control.
Holding
A predetermined maneuver that keeps aircraft within a specified airspace while awaiting further clearance from ATC.
Holding Fix
A specified fix identifiable to a pilot by NAVAIDs or visual reference to the ground used as a reference point in establishing and maintaining the position of an aircraft while holding.
Holding pattern
A racetrack pattern, involving two turns and two legs, used to keep an aircraft within a prescribed airspace with respect to a geographic fix. A standard pattern uses right turns; nonstandard patterns use left turns.
Homing
Flying the aircraft on any heading required to keep the needle pointing to the 0 relative bearing position.
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.
HSI
Horizontal Situation Indicator.
HUD
Head-Up Display.
Human factors
A multidisciplinary field encompassing the behavioral and social sciences, engineering, and physiology, to consider the variables that influence individual and crew performance for the purpose of optimizing human performance and reducing errors.
Hypoxia
A state of oxygen deficiency in the body sufficient to impair functions of the brain and other organs.
IAF
Initial Approach Fix.
IAP
Instrument Approach Procedures.
IAS
Indicated Airspeed.
IAWP
Initial Approach Waypoint
ICA
Initial Climb Area
ICAO
International Civil Aviation Organization.
Ident
Air Traffic Control request for a pilot to push the button on the transponder to identify return on the controllers scope.
IF
Intermediate Fix
If No Transmission Received For (Time)
Used by ATC in radar approaches to prefix procedures which should be followed by the pilot in event of lost communications.
IFR
Instrument Flight Rules.
IFR (Instrument Flight Rules)
Rules that govern the procedure for conducting flight in weather conditions below VFR weather minimums. The term “IFR” also is used to define weather conditions and the type of flight plan under which an aircraft is operating.
IFR Aircraft
An aircraft conducting flight in accordance with instrument flight rules.
IFR conditions
Weather conditions below the minimum for flight under visual flight rules.
IFR Departure Procedure
IFR Takeoff Minimums And Departure Procedures.
IFR Flight
IFR Aircraft.
IFR Landing Minimums
Landing Minimums.
IFR over-the-top
With respect to the operation of aircraft, the operation of an aircraft over-the-top on an IFR flight plan when cleared by air traffic control to maintain “VFR conditions” or “VFR conditions on top”.
IFR Takeoff Minimums And Departure Procedures
Title 14 Code of Federal Regulations Part 91, prescribes standard takeoff rules for certain civil users. At some airports, obstructions or other factors require the establishment of nonstandard takeoff minimums, departure procedures, or both to assist pilots in avoiding obstacles during climb to the minimum en route altitude. Those airports are listed in FAA/DOD Instrument Approach Procedures (IAPs) Charts under a section entitled “IFR Takeoff Minimums and Departure Procedures.” The FAA/DOD IAP chart legend illustrates the symbol used to alert the pilot to nonstandard takeoff minimums and departure procedures. When departing IFR from such airports or from any airports where there are no departure procedures, DPs, or ATC facilities available, pilots should advise ATC of any departure limitations. Controllers may query a pilot to determine acceptable departure directions, turns, or headings after takeoff. Pilots should be familiar with the departure procedures and must assure that their aircraft can meet or exceed any specified climb gradients.
ILS
Instrument Landing System.
ILS Categories
1. Category I. An ILS approach procedure which provides for approach to a height above touchdown of not less than 200 feet and with runway visual range of not less than 1,800 feet. 2. Special Authorization Category I. An ILS approach procedure which provides for approach to a height above touchdown of not less than 150 feet and with runway visual range of not less than 1,400 feet, HUD to DH. 3. Category II. An ILS approach procedure which provides for approach to a height above touchdown of not less than 100 feet and with runway visual range of not less than 1,200 feet (with autoland or HUD to touchdown and noted on authorization, RVR 1,000 feet). 4. Special Authorization Category II with Reduced Lighting. An ILS approach procedure which provides for approach to a height above touchdown of not less than 100 feet and with runway visual range of not less than 1,200 feet with autoland or HUD to touchdown and noted on authorization (no touchdown zone and centerline lighting are required). 5. Category III: a. IIIA.-An ILS approach procedure which provides for approach without a decision height minimum and with runway visual range of not less than 700 feet. b. IIIB.-An ILS approach procedure which provides for approach without a decision height minimum and with runway visual range of not less than 150 feet. c. IIIC.-An ILS approach procedure which provides for approach without a decision height minimum and without runway visual range minimum.
ILS Category I
Provides for approach to a height above touchdown of not less than 200 feet, and with runway visual range of not less than 1,800 feet.
ILS Category II
Provides for approach to a height above touchdown of not less than 100 feet and with runway visual range of not less than 1,200 feet.
ILS Category IIIA
Provides for approach without a decision height minimum and with runway visual range of not less than 700 feet.
ILS Category IIIB
Provides for approach without a decision height minimum and with runway visual range of not less than 150 feet.
ILS Category IIIC
Provides for approach without a decision height minimum and without runway visual range minimum.
ILS/PRM
Instrument Landing System/Precision Runway Monitor
IM
ILS Inner Marker.
IMC
Instrument Meteorological Conditions.
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.
Indirect indication
A reflection of aircraft pitch-and-bank attitude by the instruments other than the attitude indicator.
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.
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.
Initial Approach
The segment between the initial approach fix and the intermediate fix or the point where the aircraft is established on the intermediate course or final approach course.
Initial approach fix (IAF)
The fix depicted on IAP charts where the instrument approach procedure (IAP) begins unless otherwise authorized by ATC.
Initial Approach Segment
Segments Of An Instrument Approach Procedure.
Initial Climb Area (ICA)
An area beginning at the departure end of runway (DER) to provide unrestricted climb to at least 400 feet above DER elevation.
Inner Marker
A marker beacon used with an ILS (CAT II) precision approach located between the middle marker and the end of the ILS runway, transmitting a radiation pattern keyed at six dots per second and indicating to the pilot, both aurally and visually, that he/she is at the designated decision height (DH), normally 100 feet above the touchdown zone elevation, on the ILS CAT II approach. It also marks progress during a CAT III approach.
Inner Marker Beacon
Inner Marker.
Inner-Approach OFZ
The inner-approach OFZ (Obstacle Free Zone)is a defined volume of airspace centered on the approach area. The inner-approach OFZ applies only to runways with an approach lighting system. The inner-approach OFZ begins 200 feet from the runway threshold at the same elevation as the runway threshold and extends 200 feet beyond the last light unit in the approach lighting system. The width of the inner-approach OFZ is the same as the runway OFZ and rises at a slope of 50 (horizontal) to 1 (vertical) from the beginning.
Inner-Transitional OFZ
The inner transitional surface OFZ (Obstacle Free Zone) is a defined volume of airspace along the sides of the runway and inner-approach OFZ and applies only to precision instrument runways. The inner-transitional surface OFZ slopes 3 (horizontal) to 1 (vertical) out from the edges of the runway OFZ and inner-approach OFZ to a height of 150 feet above the established airport elevation.
Inoperative components
Higher minimums are prescribed when the specified visual aids are not functioning; this information is listed in the Inoperative Components Table found in the United States Terminal Procedures Publications.
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).
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) Charts
Portray the aeronautical data which is required to execute an instrument approach to an airport. These charts depict the procedures, including all related data, and the airport diagram. Each procedure is designated for use with a specific type of electronic navigation system including NDB, TACAN, VOR, ILS/MLS, and RNAV. These charts are identified by the type of navigational aid(s) which provide final approach guidance.
Instrument Approach Waypoint
Fixes used in defining RNAV IAPs, including the feeder waypoint (FWP), the initial approach waypoint (IAWP), the intermediate waypoint (IWP), the final approach waypoint (FAWP), the RWY WP, and the APT WP, when required.
Instrument 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 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 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 Procedure with Vertical Guidance (IPV)
Satellite or Flight Management System (FMS) lateral navigation (LNAV) with computed positive vertical guidance based on barometric or satellite elevation. This term has been renamed APV.
Instrument proficiency check
An evaluation ride based on the instrument rating practical test standard which is required to regain instrument flying privileges when the privileges have expired due to lack of currency.
Instrument Runway
A runway equipped with electronic and visual navigation aids for which a precision or nonprecision approach procedure having straight-in landing minimums has been approved.
Instrument takeoff
Using the instruments rather than outside visual cues to maintain runway heading and execute a safe takeoff.
Interference drag
Drag generated by the collision of airstreams creating eddy currents, turbulence, or restrictions to smooth flow.
Intermediate Approach
The segment between the intermediate fix or point and the final approach fix.
Intermediate Approach Segment
Segments Of An Instrument Approach Procedure.
Intermediate Fix
The fix that identifies the beginning of the intermediate approach segment of an instrument approach procedure. The fix is not normally identified on the instrument approach chart as an intermediate fix (IF).
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 standard atmosphere (IAS)
A model of standard variation of pressure and temperature.
Into A.C
Current of the proper voltage and frequency to operate A.C. gyro instruments.
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.
IPV
Instrument Procedure With Vertical Guidance (This term has been renamed APV)
Isogonic lines
Lines drawn across aeronautical charts to connect points having the same magnetic variation.
IVSI
Instantaneous Vertical Speed Indicator.
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.
KIAS
Knots Indicated Airspeed.
KIAS
Knots Indicated Airspeed
Kollsman window
A barometric scale window of a sensitive altimeter used to adjust the altitude for the altimeter setting.
L/MF
Low or Medium Frequency.
LAADR
Low Altitude Arrival/Departure Routing.
LAAS
Local Area Augmentation System.
Lag
The delay that occurs before an instrument needle attains a stable indication.
LAHSO
Land and Hold Short Operations
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 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 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.
Last Assigned Altitude
The last altitude/flight level assigned by ATC and acknowledged by the pilot.
Lateral Navigation (LNAV)
A function of area navigation (RNAV) equipment which calculates, displays, and provides lateral guidance to a profile or path.
LDA
Localizer-type Directional Aid.
LDA/PRM
Localizer Type Directional Aid/Precision Runway Monitor
LDIN
Lead-In-Light System. Consists Of One Or More Series Of Flashing Lights Installed At Or Near Ground Level That Provides Positive Visual Guidance Along An Approach Path, Either Curving Or Straight, Where Special Problems Exist With Hazardous Terrain, Obstructions, Or Noise Abatement Procedures
Lead radial
The radial at which the turn from the DME arc to the inbound course is started.
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.
Left Base Area
A type of Terminal Arrival Area. A 30NM arc centered on the right corner IAF (Initial Approach Fix). The area shares a boundary with the straight-in area except that it extends out for 30NM from the IAF and is bounded on the other side by a line extending from the IF through the FAF to the arc.
LF
Low Frequency
Lift
A component of the total aerodynamic force on an airfoil and acts perpendicular to the relative wind.
Lines of flux
Invisible lines of magnetic force passing between the poles of a magnet.
LMM
Locator Middle Marker.
LNAV
Lateral Navigation
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.
Loadmeter
A type of ammeter installed between the generator output and the main bus in an aircraft electrical system.
LOC
Localizer.
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.
Locator middle marker (LMM)
Nondirectional radio beacon (NDB) compass locator, collocated with a middle marker (MM).
Locator outer marker (LOM)
NDB compass locator, collocated with an outer marker (OM).
LOM
Locator Outer Marker.
Long range navigation (LORAN)
[Decommissioned in 2010] 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.
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 Separation
The longitudinal spacing of aircraft at the same altitude by a minimum distance expressed in units of time or miles.
LORAN
Long Range Navigation. [Decommissioned in 2010]
LORAN-C
[Decommissioned in 2010] A radio navigation system that utilizes master and slave stations transmitting timed pulses. The time difference in reception of pulses from several stations establishes a hyperbolic line of position, which can be identified on a LORAN chart. A fix in position is obtained by utilizing signals from two or more stations.
Loss of Separation
An occurrence or operation that results in less than prescribed separation between aircraft, or between an aircraft and a vehicle, pedestrian, or object.
Low Altitude Alert System
An automated function of the TPX-42 that alerts the controller when a Mode C transponder equipped aircraft on an IFR flight plan is below a predetermined minimum safe altitude. If requested by the pilot, Low Altitude Alert System monitoring is also available to VFR Mode C transponder equipped aircraft.
Low Altitude Alert, Check Your Altitude Immediately
Safety Alert.
Low 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.
LP
Localizer Performance
LPV
A Type Of Approach With Vertical Guidance (APV) Based On Waas, Published On RNAV (GPS) Approach Charts. This Procedure Takes Advantage Of The Precise Lateral Guidance Available From Waas. The Minima Is Published As A Decision Altitude (DA)
LTP
Landing Threshold Point
LUAW
Line Up And Wait
Lubber line
The reference line used in a magnetic compass or heading indicator.
MAA
Maximum Authorized Ifr Altitude.
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.
Magnetic bearing (MB)
The direction to or from a radio transmitting station measured relative 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.
MAHWP
Missed Approach Holding Waypoint
MALSF
Medium Intensity Approach Light System With Sequenced Flashing Lights
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.
MAP
Missed Approach Point.
Margin identification
The top and bottom areas on an instrument approach chart that depict information about the procedure, including airport location and procedure identification.
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.
MAWP
Missed Approach Waypoint
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.
MB
Magnetic Bearing.
MCA
Minimum Crossing Altitude.
MDA
Minimum Descent Altitude.
MDH
Minimum Descent Height
MEA
Minimum Enroute Altitude.
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.
MEL
Minimum Equipment List
METAR
Aviation Routine Weather Report
Metering
A method of time-regulating arrival traffic flow into a terminal area so as not to exceed a predetermined terminal acceptance rate.
Metering Fix
A fix along an established route over which aircraft will be metered prior to entering terminal airspace. Normally, this fix should be established at a distance from the airport which will facilitate a profile descent 10,000 feet above airport elevation (AAE) or above.
MFD
Multi-Function Display.
MH
Magnetic Heading.
MHA
Minimum Holding Altitude
MHz
Megahertz.
MIA
Minimum IFR Altitude
Microwave landing system (MLS)
A precision instrument approach system operating in the microwave spectrum which normally consists of an azimuth station, elevation station, and precision distance measuring equipment.
Mid-RVR
The RVR readout values obtained from sensors located midfield of the runway.
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.
Miles-In-Trail
A specified distance between aircraft, normally, in the same stratum associated with the same destination or route of flight.
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).
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 Crossing Altitude (MCA)
An MCA is the lowest altitude at certain fixes at which the aircraft must cross when proceeding in the direction of a higher minimum en route IFR altitude. MCAs are established in all cases where obstacles intervene to prevent pilots from maintaining obstacle clearance during a normal climb to a higher MEA after passing a point beyond which the higher MEA applies.
Minimum descent altitude (MDA)
The lowest altitude specified in a [nonprecision] instrument approach procedure, expressed in feet above mean sea level, to which descent is authorized on final approach or during circle-to-land maneuvering until the pilot sees the required visual references for the heliport or runway of intended landing.
Minimum 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 IFR Altitudes (MIA)
Minimum altitudes for IFR operations as prescribed in 14 CFR Part 91. These altitudes are published on aeronautical charts and prescribed in 14 CFR Part 95 for airways and routes, and in 14 CFR Part 97 for standard instrument approach procedures. If no applicable minimum altitude is prescribed in 14 CFR Part 95 or 14 CFR Part 97, the following minimum IFR altitude applies: a. In designated mountainous areas, 2,000 feet above the highest obstacle within a horizontal distance of 4 nautical miles from the course to be flown; or b. Other than mountainous areas, 1,000 feet above the highest obstacle within a horizontal distance of 4 nautical miles from the course to be flown; or c. As otherwise authorized by the Administrator or assigned by ATC.
Minimum obstruction clearance altitude (MOCA)
The lowest published altitude in effect between radio fixes on VOR airways, off-airway routes, or route segments, which meets obstacle clearance requirements for the entire route segment and which ensures acceptable navigational signal coverage only within 25 statute (22 nautical) miles of a VOR.
Minimum Reception Altitude (MRA)
An MRA is determined by FAA flight inspection traversing an entire route of flight to establish the minimum altitude the navigation signal can be received for the route and for off-course NAVAID facilities that determine a fix. When the MRA at the fix is higher than the MEA, an MRA is established for the fix, and is the lowest altitude at which an intersection can be determined.
Minimum Safe Altitudes (MSA)
MSAs are published for emergency use on IAP charts. For conventional navigation systems, the MSA is normally based on the primary omnidirectional facility on which the IAP is predicated. For RNAV approaches, the MSA is based on the runway waypoint (RWY WP) for straight in approaches, or the airport waypoint (APT WP) for circling approaches. For GPS approaches, the MSA center will be the Missed Approach Waypoint (MAWP).
Minimum Sector Altitudes
Altitudes depicted on approach charts which provide at least 1,000 feet of obstacle clearance within a 25-mile radius of the navigation facility upon which the procedure is predicated. Sectors depicted on approach charts must be at least 90 degrees in scope. These altitudes are for emergency use only and do not necessarily assure acceptable navigational signal coverage.
Minimums section
The area on an IAP chart that displays the lowest altitude and visibility requirements for the approach.
MINIT
Minutes in Trail. A specified interval between aircraft expressed in time.
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.
MIT
Miles-In-Trail
Mixed ice
A mixture of clear ice and rime ice.
MLS
Microwave Landing System.
MM
Middle Marker.
MNPS
Minimum Navigation Performance Specifications
MOA
Military Operations Area.
MOCA
Minimum Obstruction Clearance Altitude.
Mode C
Altitude Reporting Transponder Mode.
MORA
Minimum Off Route Altitude
MRA
Minimum Reception Altitude
MSA
Minimum Safe Altitude.
MSL
Mean Sea Level.
MTA
Minimum Turning Altitude
MTR
Military Training Route.
Multi-function display (MFD)
Small screen (CRT or LCD) in an aircraft that can be used to display information to the pilot in numerous configurable ways. Often an MFD will be used in concert with a Primary Flight Display.
MVA
Minimum Vectoring Altitude.
NA
Not Authorized
NACG
National Aeronautical Charting Group. (obsolete)
NACO
National Aeronautical Charting Office
NAS
National Airspace System.
NASA
National Aeronautics and Space Administration
NASSI
National Airspace System Status Information
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 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 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.
NAV/COM
Navigation and Communication Radio.
NAVAID
Navigational Aid.
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.
NDB
Nondirectional Radio Beacon.
NFDC
National Flight Data Center
NFPO
National Flight Procedures Office
NGA
National Geospatial Intelligence Agency
NIMA
National Imagery and Mapping Agency
NM
Nautical Mile.
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.
NOAA
National Oceanic and Atmospheric Administration.
Non-RNAV DP
A DP whose ground track is based on ground-based NAVAIDS and/or dead reckoning navigation.
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.
Nonprecision approach
A standard instrument approach procedure in which only horizontal guidance is provided.
Nonprecision Approach Procedure
A standard instrument approach procedure in which no electronic glideslope is provided; e.g., VOR, TACAN, NDB, LOC, ASR, LDA, or SDF approaches.
Nonprecision Approach Runway
An instrument runway served by visual aids and a nonvisual aid providing at least directional guidance adequate for a straight-in approach.
Nonradar Approach
Used to describe instrument approaches for which course guidance on final approach is not provided by ground-based precision or surveillance radar. Radar vectors to the final approach course may or may not be provided by ATC. Examples of nonradar approaches are VOR, NDB, TACAN, and ILS/MLS approaches.
Nonradar Approach Control
An ATC facility providing approach control service without the use of radar.
Nonradar Arrival
An aircraft arriving at an airport without radar service or at an airport served by a radar facility and radar contact has not been established or has been terminated due to a lack of radar service to the airport.
Nonradar Route
A flight path or route over which the pilot is performing his/her own navigation. The pilot may be receiving radar separation, radar monitoring, or other ATC services while on a nonradar route.
Nonradar Separation
The spacing of aircraft in accordance with established minima without the use of radar; e.g., vertical, lateral, or longitudinal separation.
NoPT
No Procedure Turn.
NOTAM
Notice To Airmen
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.
NPA
Nonprecision Approach
NRP
National Route Program.
NRR
Non-Restrictive Routing
NSA
National Security Area.
NTAP
Notice To Airmen Publication
NTSB
National Transportation Safety Board.
NTZ
No Transgression Zone
NWS
National Weather Service.
Obstacle Clearance Surface (OCS)
An inclined or level surface associated with a defined area for obstruction evaluation.
Obstacle departure procedures (ODP)
A preplanned instrument flight rule (IFR) departure procedure printed for pilot use in textual or graphic form to provide obstruction clearance via the least onerous route from the terminal area to the appropriate en route structure. ODPs are recommended for obstruction clearance and may be flown without ATC clearance unless an alternate departure procedure (SID or radar vector) has been specifically assigned by ATC.
Obstacle 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.
OCS
Obstacle Clearance Surface
ODALS
Omnidirectional Approach Lighting System Consists of seven omnidirectional flashing lights located in the approach area of a nonprecision runway. Five lights are located on the runway centerline extended with the first light located 300 feet from the threshold and extending at equal intervals up to 1,500 feet from the threshold. The other two lights are located, one on each side of the runway threshold, at a lateral distance of 40 feet from the runway edge, or 75 feet from the runway edge when installed on a runway equipped with a VASI.
ODP
Obstacle Departure Procedures.
Off Course
A term used to describe a situation where an aircraft has reported a position fix or is observed on radar at a point not on the ATC-approved route of flight.
Off-Airway Routes
The FAA prescribes altitudes governing the operation of aircraft under IFR for off airway routes in a similar manner to those on federal airways, jet routes, area navigation low or high altitude routes, and other direct routes for which an MEA is designated.
Off-Route Obstruction Clearance Altitude (OROCA)
An off-route altitude that provides obstruction clearance with a 1,000 foot buffer in non-mountainous terrain areas and a 2,000 foot buffer in designated mountainous areas within the U.S. This altitude may not provide signal coverage from ground based navigational aids, air traffic control radar, or communications coverage.
Off-Route Vector
A vector by ATC which takes an aircraft off a previously assigned route. Altitudes assigned by ATC during such vectors provide required obstacle clearance.
OM
Outer Marker.
Omission error
The failure to anticipate significant instrument indications following attitude changes; for example, concentrating on pitch control while forgetting about heading or roll information, resulting in erratic control of heading and bank.
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.
Orientation
Awareness of the position of the aircraft and of oneself in relation to a specific reference point.
OROCA
An off-route altitude which provides obstruction clearance with a 1,000 foot buffer in nonmountainous terrain areas and a 2,000 foot buffer in designated mountainous areas within the United States. This altitude may not provide signal coverage from ground-based navigational aids, air traffic control radar, or communications coverage.
Otolith organ
An inner ear organ that detects linear acceleration and gravity orientation.
Outer Compass Locator (LOM)
A compass locator installed at the site of the outer marker of an instrument landing system.
Outer Fix
A general term used within ATC to describe fixes in the terminal area, other than the final approach fix. Aircraft are normally cleared to these fixes by an Air Route Traffic Control Center or an Approach Control Facility. Aircraft are normally cleared from these fixes to the final approach fix or final approach course.
Overcontrolling
Using more movement in the control column than is necessary to achieve the desired pitch-and bank condition.
Overpower
To use more power than required for the purpose of achieving a faster rate of airspeed change.
P-static
Precipitation Static.
PA
Precision Approach
PAPI
Precision Approach Path Indicator.
PAR
Precision Approach Radar.
Parallel ILS Approaches
Approaches to parallel runways by IFR aircraft which, when established inbound toward the airport on the adjacent final approach courses, are radar-separated by at least 2 miles.
Parallel MLS Approaches
Approaches to parallel runways by IFR aircraft which, when established inbound toward the airport on the adjacent final approach courses, are radar-separated by at least 2 miles.
Parasite drag
Drag caused by the friction of air moving over the aircraft structure; its amount varies directly with the airspeed.
PCG
Positive Course Guidance
PDC
Pre-Departure Clearance
PDR
Preferential Departure Route
PF
Pilot Flying
PFAST
Passive Final Approach Spacing Tool
PFD
Primary Flight Display.
PIC
Pilot-in-Command.
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 report (PIREP)
Report of meteorological phenomena encountered by aircraft.
Pilot’s Operating Handbook/Airplane Flight Manual (POH/AFM)
FAA-approved documents published by the airframe manufacturer that list the operating conditions for a particular model of aircraft.
PinS
Point-In-Space
PIREP
Pilot Report.
Pitch Point
A fix/waypoint that serves as a transition point from a departure procedure or the low altitude ground-based navigation structure into the high altitude waypoint system.
Pitot pressure
Ram air pressure used to measure airspeed.
Pitot-static head
A combination pickup used to sample pitot pressure and static air pressure.
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.
PM
Pilot Monitoring
POH/AFM
Pilots Operating Handbook/Airplane Flight Manual.
Point-To-Point (PTP)
A level of NRR service for aircraft that is based on traditional waypoints in their FMSs or RNAV equipage.
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 report
A report over a known location as transmitted by an aircraft to ATC.
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.
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 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 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 Procedure
A standard instrument approach procedure in which an electronic glideslope/glidepath is provided; e.g., ILS, MLS, and PAR.
Precision Approach Radar
Radar equipment in some ATC facilities operated by the FAA and/or the military services at joint-use civil/military locations and separate military installations to detect and display azimuth, elevation, and range of aircraft on the final approach course to a runway. This equipment may be used to monitor certain nonradar approaches, but is primarily used to conduct a precision instrument approach (PAR) wherein the controller issues guidance instructions to the pilot based on the aircraft’s position in relation to the final approach course (azimuth), the glidepath (elevation), and the distance (range) from the touchdown point on the runway as displayed on the radar scope. Note: The abbreviation “PAR” is also used to denote preferential arrival routes in ARTCC computers.
Precision 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.
Prevailing visibility
The greatest horizontal visibility equaled or exceeded throughout at least half the horizon circle (which is not necessarily continuous).
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.
Principal Operations Inspector (POI)
Scheduled air carriers and operators for compensation or hire are assigned a principal operations inspector (POI) who works directly with the company and coordinates FAA operating approval.
PRM
ILS PRM Approach and Precision Runway Monitor.
Procedure Turn
The maneuver prescribed when it is necessary to reverse direction to establish an aircraft on the intermediate approach segment or final approach course. The outbound course, direction of turn, distance within which the turn must be completed, and minimum altitude are specified in the procedure. However, unless otherwise restricted, the point at which the turn may be commenced and the type and rate of turn are left to the discretion of the pilot.
Procedure Turn Inbound
That point of a procedure turn maneuver where course reversal has been completed and an aircraft is established inbound on the intermediate approach segment or final approach course. A report of “procedure turn inbound” is normally used by ATC as a position report for separation purposes.
Profile view
Side view of an IAP chart illustrating the vertical approach path altitudes, headings, distances, and fixes.
Progress Report
Position Report.
Prohibited Area
Airspace designated under 14 CFR Part 73 within which no person may operate an aircraft without the permission of the using agency.
PT
Procedure Turn
PTP
Point-To-Point
Published Instrument Approach Procedure Visual Segment
A segment on an IAP chart annotated as “Fly Visual to Airport” or ”Fly Visual.” A dashed arrow will indicate the visual flight path on the profile and plan view with an associated note on the approximate heading and distance. The visual segment should be flown as a dead reckoning course while maintaining visual conditions.
Published Route
A route for which an IFR altitude has been established and published; e.g., Federal Airways, Jet Routes, Area Navigation Routes, Specified Direct Routes.
Q Route
`Q’ is the designator assigned to published RNAV routes used by the United States.
QFE
Transition Height
QNE
Transition Level
QNH
Transition Altitude
Quadrant
A quarter part of a circle, centered on a NAVAID, oriented clockwise from magnetic north as follows: NE quadrant 000-089, SE quadrant 090-179, SW quadrant 180-269, NW quadrant 270-359.
RA
Resolution Advisory,Radio Altitude
Rabbit, the
High-intensity flasher system installed at many large airports. The flashers consist of a series of brilliant blue-white bursts of light flashing in sequence along the approach lights, giving the effect of a ball of light traveling towards the runway.
Radar
Radio Detection And Ranging.
Radar 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 Required
A term displayed on charts and approach plates and included in FDC NOTAMs to alert pilots that segments of either an instrument approach procedure or a route are not navigable because of either the absence or unusability of a NAVAID. The pilot can expect to be provided radar navigational guidance while transiting segments labeled with this term.
Radar Route
A flight path or route over which an aircraft is vectored. Navigational guidance and altitude assignments are provided by ATC.
Radar Separation
Radar spacing of aircraft in accordance with established minima.
Radials
The courses oriented from a station.
Radio Beacon
Nondirectional Beacon.
Radio frequency (RF)
A term that refers to alternating current (AC) having characteristics such that, if the current is input to antenna, an electromagnetic (EM) field is generated suitable for wireless broadcasting and/or communications.
Radio 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 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 wave
An electromagnetic wave (EM wave) with frequency characteristics useful for radio transmission.
RAIL
Runway Alignment Indicator Lights Sequenced Flashing Lights Which Are Installed Only In Combination With Other Light Systems
RAIM
Receiver Autonomous Integrity Monitoring.
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.
Ranging signals
Transmitted from the GPS satellite, these allow the aircrafts receiver to determine range (distance) from each satellite.
RB
Relative Bearing.
RBI
Relative Bearing Indicator.
RCLS
Runway Centerline Light System.
RCO
Remote Communications Outlet.
RDOF
Radio Failure
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.
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.
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.
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 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.
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.
REIL
Runway End Identifier Lights.
Relative bearing (RB)
The angular difference between the aircraft heading and the direction to the station, measured clockwise from the nose of the aircraft.
Relative bearing indicator (RBI)
Also known as the fixed- card ADF, zero is always indicated at the top of the instrument and the needle indicates the relative bearing to the station.
Release Time
A departure time restriction issued to a pilot by ATC (either directly or through an authorized relay) when necessary to separate a departing aircraft from other traffic.
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.
Reporting Point
A geographical location in relation to which the position of an aircraft is reported. (See Compulsory Reporting Points)
Required navigation performance (RNP)
A specified level of accuracy defined by a lateral area of confined airspace in which an RNP-certified aircraft operates.
Restricted Area
Airspace designated under 14 CFR Part 73, within which the flight of aircraft, while not wholly prohibited, is subject to restriction. Most restricted areas are designated joint use and IFR/VFR operations in the area may be authorized by the controlling ATC facility when it is not being utilized by the using agency. Restricted areas are depicted on en route charts. Where joint use is authorized, the name of the ATC controlling facility is also shown.
Reverse sensing
The VOR needle appearing to indicate the reverse of normal operation.
RF
Radio Frequency.
Right Base Area
A type of Terminal Arrival Area. A 30NM arc centered on the left corner IAF (Initial Approach Fix). The area shares a boundary with the straight-in area except that it extends out for 30NM from the IAF and is bounded on the other side by a line extending from the IF through the FAF to the arc.
Rigidity
The characteristic of a gyroscope that prevents its axis of rotation tilting as the Earth rotates.
Rime ice
Rough, milky, opaque ice formed by the instantaneous freezing of small supercooled water droplets.
RLSD
Released
RMI
Radio Magnetic Indicator.
RNAV
Area Navigation.
RNAV Approach
An instrument approach procedure which relies on aircraft area navigation equipment for navigational guidance.
RNAV DP
A DP developed for RNAV-equipped aircraft whose ground track is based on satellite or DME/DME navigation systems.
RNP
Required Navigation Performance.
ROC
Required Obstacle Clearance
Roll-out RVR
The RVR readout values obtained from sensors located nearest the rollout end of the runway.
RPAT
RNP Parallel Approach Runway Transitions
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 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 Profile Descent
An instrument flight rules (IFR) air traffic control arrival procedure to a runway published for pilot use in graphic and/or textual form and may be associated with a STAR. Runway Profile Descents provide routing and may depict crossing altitudes, speed restrictions, and headings to be flown from the en route structure to the point where the pilot will receive clearance for and execute an instrument approach procedure. A Runway Profile Descent may apply to more than one runway if so stated on the chart.
Runway Transition
A. Conventional STARs/SIDs. The portion of a STAR/SID that serves a particular runway or runways at an airport.
B. RNAV STARs/SIDs. Defines a path(s) from the common route to the final point(s) on a STAR. For a SID, the common route that serves a particular runway or runways at an airport.
Runway 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 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.
RVR
Runway Visual Range.
RVSM
Reduced Vertical Separation Minimums
RVV
Runway Visibility Value.
RWY
Runway
SA
Selective Availability.
SAAAR
Special Aircraft and Aircrew Authorization Required
SALS
Short Approach Light System.
SAS
Stability Augmentation System
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.
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.
SDF
Simplified Directional Facility.
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.
Semicircular canal
An inner ear organ that detects angular acceleration of the body.
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.
Separation
In air traffic control, the spacing of aircraft to achieve their safe and orderly movement in flight and while landing and taking off.
Separation Minima
The minimum longitudinal, lateral, or vertical distances by which aircraft are spaced through the application of air traffic control procedures.
SER
Start End of Runway
Short Range Clearance
A clearance issued to a departing IFR flight which authorizes IFR flight to a specific fix short of the destination while air traffic control facilities are coordinating and obtaining the complete clearance.
SIAP
Standard Instrument Approach Procedure
SID
Standard Instrument Departure
Sidestep Maneuver
A visual maneuver accomplished by a pilot at the completion of an instrument approach to permit a straight-in landing on a parallel runway not more than 1,200 feet to either side of the runway to which the instrument approach was conducted.
SIDS
Standard Instrument Departure Procedures.
SIGMET
The acronym for Significant Meteorological information. A weather advisory issued concerning weather significant to the safety of all aircraft.
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.
Significant Point
A point, whether a named intersection, a NAVAID, a fix derived from a NAVAID(s), or geographical coordinate expressed in degrees of latitude and longitude, which is established for the purpose of providing separation, as a reporting point, or to delineate a route of flight.
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.
Simultaneous ILS Approaches
An approach system permitting simultaneous ILS/MLS approaches to airports having parallel runways separated by at least 4,300 feet between centerlines. Integral parts of a total system are ILS/MLS, radar, communications, ATC procedures, and appropriate airborne equipment.
Simultaneous MLS Approaches
An approach system permitting simultaneous ILS/MLS approaches to airports having parallel runways separated by at least 4,300 feet between centerlines. Integral parts of a total system are ILS/MLS, radar, communications, ATC procedures, and appropriate airborne equipment.
Single Direction Routes
Preferred IFR Routes which are sometimes depicted on high altitude en route charts and which are normally flown in one direction only.
Single-pilot resource management (SRM)
The ability for crew or pilot to manage all resources effectively to ensure the outcome of the flight is successful.
Situational awareness
Pilot knowledge of where the aircraft is in regard to location, air traffic control, weather, regulations, aircraft status, and other factors that may affect flight.
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.
Slant range
The horizontal distance from the aircraft antenna to the ground station, due to line-of-sight transmission of the DME signal.
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).
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.
SM
Statute Mile
SMA
Surface Movement Advisor
SOIA
Simultaneous Offset Instrument Approaches
Somatogravic illusion
The misperception of being in a nose-up or nose-down attitude, caused by a rapid acceleration or deceleration while in flight situations that lack visual reference.
SOP
Standard Operating Procedure
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.
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.
SRM
Single-pilot Resource Management.
SSALF
Simplified Short Approach Light System With Sequenced Flashing Lights
SSALR
Simplified Short Approach Light System With Runway Alignment Indicator Lights
SSALS
Simplified Short Approach Light System.
SSALSR
Simplified Short Approach Light System with Runway Alignment Indicator Lights.
SSR
Secondary Surveillance Radar.
SSV
Standard Service Volume.
St. Elmo’s Fire
A corona discharge which lights up the aircraft surface areas where maximum static discharge occurs.
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 holding pattern
A holding pattern in which all turns are made to the right.
Standard Instrument Departure (SID)
A preplanned instrument flight rule (IFR) air traffic control (ATC) departure procedure printed for pilot/controller use in graphic form to provide obstacle clearance and a transition from the terminal area to the appropriate en route structure. SIDs are primarily designed for system enhancement to expedite traffic flow and to reduce pilot/controller workload. ATC clearance must always be received prior to flying a SID.
Standard instrument departure procedures (SIDS).
Published procedures to expedite clearance delivery and to facilitate transition between takeoff and en route operations.
Standard rate turn
A turn in which an aircraft changes its direction at a rate of 3° per second (360° in 2 minutes) for low- or medium-speed aircraft. For high-speed aircraft, the standard rate turn is 1 1⁄2° per second (360° in 4 minutes).
Standard 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 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.
STAR
Standard Terminal Arrival Route.
STAR Transition
A published segment used to connect one or more en route airways, jet routes, or RNAV routes to the basic STAR procedure. It is one of several routes that bring traffic from different directions into one STAR. NACO publishes STARs for airports with procedures authorized by the FAA, and these STARs are included at the front of each Terminal Procedures Publication regional booklet.
STARS
Standard Terminal Automation Replacement System
Start End of Runway (SER)
The beginning of the takeoff runway available.
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.
Station Declination
The angular difference between true north and the zero radial of a VOR at the time the VOR was last site checked.
Steep turns
In instrument flight, any turn greater than standard rate; in visual flight, anything greater than a 45° bank.
Stepdown Fix
A fix permitting additional descent within a segment of an instrument approach procedure by identifying a point at which a controlling obstacle has been safely overflown.
STMP
Special Traffic Management Program
Straight-In Approach IFR
An instrument approach wherein final approach is begun without first having executed a procedure turn, not necessarily completed with a straight-in landing or made to straight-in landing minimums.
Straight-In Area
A type of Terminal Arrival Area. A 30NM arc centered on the IF (Intermediate Fix) bounded by a straight line extending through the IF perpendicular to the intermediate course.
Straight-In Landing
A landing made on a runway aligned within 30° of the final approach course following completion of an instrument approach.
Straight-In Minimums
Straight-In Landing Minimums.
Structural icing
The accumulation of ice on the exterior of the aircraft.
SUA/ISE
Special Use Airspace/Inflight Service Enhancement
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.
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 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.
Surveillance Approach
An instrument approach wherein the air traffic controller issues instructions, for pilot compliance, based on aircraft position in relation to the final approach course (azimuth), and the distance (range) from the end of the runway as displayed on the controller’s radar scope. The controller will provide recommended altitudes on final approach if requested by the pilot.
SWAP
Severe Weather Avoidance Plan
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.
TA
Traffic Advisory
TAA
Terminal arrival area.
TACAN
Tactical air navigation.
Takeoff Distance Available (TODA)
ICAO defines TODA as the length of the takeoff runway available plus the length of the clearway, if provided.
Takeoff Run Available (TORA)
The runway length declared available and suitable for the ground run of an airplane taking off.
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.
TAS
True Air Speed
TAWS
Terrain Awareness and Warning System.
Taxiway lights
Omnidirectional lights that outline the edges of the taxiway and are blue in color.
Taxiway turnoff lights
Lights that are flush with the runway which emit a steady green color.
TCAS
Traffic Alert Collision Avoidance System.
TCH
Threshold Crossing Height.
TDLS
Terminal Data Link System
TDZ
Touchdown Zone
TDZE
Touchdown Zone Elevation.
TDZL
Touchdown Zone Lights.
TEC
Tower En Route Control.
Technique
The manner in which procedures are executed.
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.
Tension
Maintaining an excessively strong grip on the control column, usually resulting in an overcontrolled situation.
Terminal Arrival Area (TAA)
The TAA is controlled airspace established in conjunction with the Standard or Modified T and I RNAV approach configurations. In the standard TAA, there are three areas: straight-in, left base, and right base. The arc boundaries of the three areas of the TAA are published portions of the approach and allow aircraft to transition from the en route structure direct to the nearest IAF (Initial Approach Fix). TAAs will also eliminate or reduce feeder routes, departure extensions, and procedure turns or course reversal.
Terminal instrument approach procedure (TERP)
Prescribes standardized methods for use in designing instrument flight procedures.
Terminal-Very High Frequency Omnidirectional Range Station
A very high frequency terminal omnirange station located on or near an airport and used as an approach aid.
TERP
Terminal Instrument Approach Procedure.
TERPS
U.S. Standard For Terminal Instrument Procedures
Terrain Awareness and Warning System (TAWS)
A timed-based system that provides information concerning potential hazards with fixed objects by using GPS positioning and a database of terrain and obstructions to provide true predictability of the upcoming terrain and obstacles.
TFM
Traffic Flow Management
TFR
Temporary Flight Restriction.
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.
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.
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.
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.
TIS
Traffic Information Service.
TM
Traffic Management
TMA
Traffic Management Advisor
TOC
Top Of Climb
TOD
Top Of Descent
TODA
Takeoff Distance Available
TOGA
Take-Off/Go Around
Top of Climb (TOC)
An identifiable waypoint representing the point at which cruise altitude is first reached. TOC is calculated based on your current aircraft altitude, climb speed, and cruise altitude. There can only be one TOC waypoint at a time.
Top of Descent (TOD)
Generally utilized in flight management systems, top of descent is an identifiable waypoint representing the point at which descent is first initiated from cruise altitude. TOD is generally calculated using the destination elevation (if available) and the descent speed schedule.
TORA
Takeoff Runway Available
Touchdown RVR
The RVR visibility readout values obtained from sensors serving the runway touchdown zone.
Touchdown Zone
The first 3,000 feet of the runway beginning at the threshold. The area is used for determination of Touchdown Zone Elevation in the development of straight-in landing minimums for instrument approaches.
Touchdown Zone Elevation
The highest elevation in the first 3,000 feet of the landing surface. TDZE is indicated on the instrument approach procedure chart when straight-in landing minimums are authorized.
Touchdown Zone 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 To Tower
Tower En Route Control Service.
TPP
United States Terminal Procedures Publication.
TRACAB
A new type of air traffic facility that consists of a radar approach control facility located in the tower cab of the primary airport, as opposed to a separate room.
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.
TRACON
Terminal Radar Approach Control
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 Management Advisor (TMA)
A software suite that helps air traffic controllers to sequence arriving air traffic.
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.
Transition
A published procedure (DP Transition) used to connect the basic DP to one of several en route airways/jet routes, or a published procedure (STAR Transition) used to connect one of several en route airways/jet routes to the basic STAR.
Transition 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 Waypoint
The waypoint that defines the beginning of a runway or en route transition on an RNAV SID or STAR.
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.
Trend
Immediate indication of the direction of aircraft movement, as shown on instruments.
Trim
Adjusting the aerodynamic forces on the control surfaces so that the aircraft maintains the set attitude without any control input.
True airspeed
Actual airspeed, determined by applying a correction for pressure altitude and temperature to the CAS.
TSE
Total Navigation System Error
TSO
Technical Standard Order
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 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.
TWEB
Transcribed Weather Broadcast - Discontinued in the CONUS in September 2018 and in Alaska on Jan 1, 2020.
UAT
Universal Access Transceiver
UHF
Ultra-High Frequency.
Uncaging
Unlocking the gimbals of a gyroscopic instrument, making it susceptible to damage by abrupt flight maneuvers or rough handling.
Underpower
Using less power than required for the purpose of achieving a faster rate of airspeed change.
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.
Unusual attitude
An unintentional, unanticipated, or extreme aircraft attitude.
URET
User Request Evaluation Tool
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.
UTC
Coordinated Universal Time
Va
The design maneuvering speed. The maximum speed at which full, abrupt control movement can be used without overstressing the airframe.
Variation
Compass error caused by the difference in the physical locations of the magnetic north pole and the geographic north pole.
VASI
Visual Approach Slope Indicator.
VCOA
Visual Climb Over Airport
VDP
Visual Descent Point.
Vectoring
Navigational guidance by assigning headings.
Vei
Instrument flight never exceed speed, utilized instead of Vne for compliance with maximum limit speed requirements for instrument flight
Venturi tube
A specially shaped tube attached to the outside of an aircraft to produce suction to allow proper operation of gyro instruments.
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 Navigation (VNAV)
Traditionally, the only way to get glidepath information during an approach was to use a ground-based NAVAID, but modern area navigation systems allow flight crews to display an internally generated descent path that allows a constant rate descent to minimums during approaches that would otherwise include multiple level-offs.
Vertical Separation
Separation established by assignment of different altitudes or flight levels.
Vertical speed indicator (VSI)
A rate-of-pressure change instrument that gives an indication of any deviation from a constant pressure level.
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.
VFR
Visual Flight Rules.
VFR over-the-top
A VFR operation in which an aircraft operates in VFR conditions on top of an undercast.
VFR-On-Top
ATC authorization for an IFR aircraft to operate in VFR conditions at any appropriate VFR altitude (as specified in 14 CFR and as restricted by ATC). A pilot receiving this authorization must comply with the VFR visibility, distance from cloud criteria, and the minimum IFR altitudes specified in 14 CFR Part 91. The use of this term does not relieve controllers of their responsibility to separate aircraft in Class B and Class C airspace or TRSAs as required by FAAO JO 7110.65.
VGSI
Visual Glide Slope Indicator
VHF
Very High Frequency
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.
Visual approach slope indicator (VASI)
A visual aid of lights arranged to provide descent guidance information during the approach to the runway. A pilot on the correct glideslope will see red lights over white lights.
Visual Climb Over Airport (VCOA)
A departure option for an IFR aircraft, operating in visual meteorological conditions equal to or greater than the specified visibility and ceiling, to visually conduct climbing turns over the airport to the published “climb-to” altitude from which to proceed with the instrument portion of the departure. VCOA procedures are developed to avoid obstacles greater than 3 statute miles from the departure end of the runway as an alternative to complying with climb gradients greater than 200 feet per nautical mile. These procedures are published in the `Take-Off Minimums and (Obstacle) Departure Procedures’ section of the Terminal Procedures Publications.
Visual descent point (VDP)
A defined point on the final approach course of a nonprecision straight-in approach procedure from which normal descent from the MDA to the runway touchdown point may be commenced, provided the runway environment is clearly visible to the pilot.
Visual flight rules (VFR)
Flight rules adopted by the FAA governing aircraft flight using visual references. VFR operations specify the amount of ceiling and the visibility the pilot must have in order to operate according to these rules. When the weather conditions are such that the pilot can not operate according to VFR, he or she must use instrument flight rules (IFR).
Visual meteorological conditions (VMC)
Meteorological conditions expressed in terms of visibility, distance from cloud, and ceiling meeting or exceeding the minimums specified for VFR.
VMC
Visual Meteorological Conditions.
VNAV
Vertical Navigation
Vnei
Never Exceed Speed-IFR.
VOR
Very-high Frequency Omnidirectional 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.
VORTAC
A facility consisting of two components, VOR and TACAN, which provides three individual services: VOR azimuth, TACAN azimuth, and TACAN distance (DME) at one site.
VOT
A ground facility which emits a test signal to check vor receiver accuracy. Some VOTs are available to the user while airborne, and others are limited to ground use only.
VPA
Vertical Path Angle
VSI
Vertical Speed Indicator.
Vso
Stalling Speed or The minimum steady flight speed in the landing configuration
VTF
Vector to Final
Vyi
Instrument climb speed, utilized instead of Vy for compliance with the climb requirements for instrument flight
WAAS
Wide Area Augmentation System.
WAC
World Aeronautical Chart Discontinued on June 25, 2015
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.
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.
WCA
Wind Correction Angle.
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).
Weight
The force exerted by an aircraft from the pull of gravity.
Wide area augmentation system (WAAS)
A differential global positioning system (DGPS) that improves the accuracy of the system by determining position error from the GPS satellites, then transmitting the error, or corrective factors, to the airborne GPS receiver.
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.
Work
A measurement of force used to produce movement.
WP
Waypoint
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.
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