Aviation Glossary

ADF

Automatic Direction Finder — radio compass pointing to an NDB station.

ADS-B

Automatic Dependent Surveillance-Broadcast — aircraft self-reports position via GPS.

Aerodrome

A defined area used for aircraft takeoff, landing, and surface movement.

Aerofoil

Cross-sectional shape of a wing designed to generate lift.

AFIS

Aerodrome Flight Information Service — information service at non-towered airports.

AGL

Above Ground Level — altitude measured from the terrain surface below.

AIP

Aeronautical Information Publication — official state document with aviation data.

AIRAC

Aeronautical Information Regulation and Control — fixed 28-day update cycle.

Airway

Defined corridor in the sky connecting navigation points for IFR traffic.

Altimeter

Instrument displaying altitude based on atmospheric pressure.

AMSL

Above Mean Sea Level — standard altitude reference datum.

Angle of Attack

Angle between the wing chord line and the relative wind.

Apron

Paved area at an airport for aircraft parking, loading, and servicing.

APU

Auxiliary Power Unit — small engine providing electrical and pneumatic power on the ground.

ARFF

Aircraft Rescue and Firefighting — specialized airport fire and rescue services.

ASDA

Accelerate-Stop Distance Available — runway plus stopway for aborted takeoff.

ASDE-X

Airport Surface Detection Equipment — radar tracking aircraft and vehicles on the ground.

ATC

Air Traffic Control — service managing aircraft movement for safety and efficiency.

ATIS

Automatic Terminal Information Service — continuous broadcast of airport conditions.

Autoland

Automatic landing system — aircraft lands without pilot manual input.

Autopilot

System that automatically controls the aircraft flight path.

Avgas

Aviation gasoline — fuel for piston-engine aircraft.

Avionics

Electronic systems used in aircraft — navigation, communication, and displays.

Backtrack

Taxiing on the runway in the opposite direction to line up for takeoff.

Baro-VNAV

Barometric Vertical Navigation — vertical guidance using barometric altitude.

Bearing

Horizontal angle from north to a reference point, measured in degrees.

CAVOK

Ceiling And Visibility OK — shorthand for excellent weather conditions.

CDL

Configuration Deviation List — allows dispatch with minor missing components.

Ceiling

Height of the lowest cloud layer covering more than half the sky.

Center of Gravity

CG — the point where the aircraft weight is balanced.

CFIT

Controlled Flight Into Terrain — accident where a functioning aircraft hits the ground.

Chord

Straight-line distance from the leading edge to trailing edge of a wing.

Circuit

Rectangular flight pattern around an airport runway — also called traffic pattern.

Class A Airspace

Controlled airspace — IFR only, ATC clearance required, full separation provided.

Class B Airspace

Controlled airspace around major airports — ATC clearance required for all traffic.

Class C Airspace

Controlled airspace — ATC service required, radar separation for IFR traffic.

Class D Airspace

Controlled airspace around towered airports — radio contact required.

Clearway

Defined area beyond the runway available for initial climb after takeoff.

Cockpit Voice Recorder

CVR — records cockpit audio for accident investigation.

Compass Rose

Painted markings on an airport surface used for calibrating aircraft compasses.

Contrail

Condensation trail — visible ice crystal trail behind aircraft at high altitude.

Crab

Crosswind technique — pointing the nose into the wind to maintain runway track.

Crosswind

Wind blowing perpendicular to the runway or flight path.

CTR

Control Zone — controlled airspace extending from the surface around an airport.

DA/DH

Decision Altitude/Height — altitude where a pilot must decide to land or go around.

Dead Reckoning

Navigation by calculating position from heading, speed, time, and wind.

Density Altitude

Pressure altitude corrected for non-standard temperature — affects performance.

Dihedral

Upward angle of wings from the fuselage — provides lateral stability.

Displaced Threshold

Runway threshold located beyond the physical start of the pavement.

DME

Distance Measuring Equipment — provides slant range distance to a ground station.

Drag

Aerodynamic force opposing aircraft motion through the air.

EASA

European Union Aviation Safety Agency — EU authority for civil aviation safety.

EFIS

Electronic Flight Instrument System — digital glass cockpit displays.

Elevator

Movable control surface on the horizontal stabilizer controlling pitch.

ELT

Emergency Locator Transmitter — distress beacon activated in a crash.

Empennage

Tail assembly of an aircraft — includes vertical and horizontal stabilizers.

ETA

Estimated Time of Arrival — predicted time an aircraft will reach its destination.

ETOPS

Extended-range Twin-engine Operations — allows twin-engine aircraft on oceanic routes.

ETP

Equal Time Point — position equidistant in time to two diversion airports.

FAA

Federal Aviation Administration — US authority for civil aviation regulation.

FBO

Fixed-Base Operator — private company providing airport services to aircraft.

FDR

Flight Data Recorder — records aircraft parameters for accident investigation.

Feathering

Rotating propeller blades edge-on to the airflow to minimize drag after engine failure.

Final Approach Fix

FAF — point where the final descent to the runway begins on an instrument approach.

FIR

Flight Information Region — defined airspace with flight information and alerting services.

Firewall

Heat-resistant barrier separating the engine compartment from the rest of the aircraft.

Flaps

Movable surfaces on the wing trailing edge that increase lift and drag.

Flight Level

Altitude reference based on standard pressure 1013.25 hPa (e.g., FL350 = 35,000 ft).

FMS

Flight Management System — computer managing navigation, performance, and flight planning.

FPL

Flight Plan — formal document filed with ATC detailing a planned flight.

Fuel Dump

Jettisoning fuel in flight to reduce weight for emergency landing.

Fuselage

Main body of the aircraft housing passengers, cargo, and systems.

GA

General Aviation — all civil aviation except scheduled airline and military operations.

Glideslope

Vertical component of ILS providing descent angle guidance to the runway.

GNSS

Global Navigation Satellite System — umbrella term for satellite navigation systems.

Go-Around

Abandoning an approach and climbing to attempt another landing.

GPU

Ground Power Unit — external electrical power source for aircraft on the ground.

GPWS

Ground Proximity Warning System — alerts pilots of terrain collision risk.

Great Circle

Shortest distance between two points on Earth surface — used for flight routing.

Ground Effect

Increased lift and reduced drag when flying close to the surface.

Hangar

Enclosed building for aircraft storage, maintenance, and protection.

Heading

Direction the aircraft nose is pointing, measured in degrees from north.

Holding Pattern

Racetrack-shaped flight path to delay aircraft when sequencing for approach.

Hydraulic System

High-pressure fluid system powering flight controls, landing gear, and brakes.

Hypoxia

Oxygen deficiency affecting the body — dangerous at high altitudes without pressurization.

IATA

International Air Transport Association — airline industry trade organization.

ICAO

International Civil Aviation Organization — UN agency setting global aviation standards.

IFR

Instrument Flight Rules — flight by reference to instruments with ATC separation.

ILS

Instrument Landing System — precision approach guidance using radio beams.

IMC

Instrument Meteorological Conditions — weather below VFR visibility minimums.

Jet Blast

High-velocity exhaust gases from jet engines — hazardous to people and objects.

Jet Stream

High-altitude wind band with speeds exceeding 60 knots — affects flight times.

Knot

Unit of speed — one nautical mile per hour (1.852 km/h).

LDA

Landing Distance Available — runway length available for landing and rollout.

LNAV

Lateral Navigation — horizontal guidance along a defined flight path.

Localizer

Horizontal component of ILS providing lateral guidance to the runway centerline.

Logbook

Official record of aircraft maintenance and flight time.

LPV

Localizer Performance with Vertical Guidance — GPS-based precision-like approach.

Mach Number

Ratio of aircraft speed to the local speed of sound.

Mach Tuck

Nose-down pitch tendency at transonic speeds caused by shifting center of pressure.

Magnetic Variation

Angle between true north and magnetic north at a given location.

Marshaller

Ground crew member guiding aircraft to parking position using hand signals.

Maximum Landing Weight

MLW — highest weight at which an aircraft is certified to land.

Maximum Takeoff Weight

MTOW — highest weight at which an aircraft is certified to take off.

MDA

Minimum Descent Altitude — lowest altitude on a non-precision approach.

MEL

Minimum Equipment List — allows dispatch with certain equipment inoperative.

METAR

Aviation routine weather report in standardized format.

Minimum Safe Altitude

MSA — lowest altitude providing obstacle clearance within 25 nm of a navaid.

Missed Approach Point

MAP — defined point where missed approach must be initiated if runway not in sight.

MSL

Mean Sea Level — standard vertical reference for altitude measurement.

Nautical Mile

Unit of distance — 1,852 meters, based on one minute of latitude.

NDB

Non-Directional Beacon — low-frequency radio navigation transmitter.

NOTAM

Notice to Airmen — alerts about hazards or changes affecting flight.

OAT

Outside Air Temperature — ambient temperature outside the aircraft.

PAPI

Precision Approach Path Indicator — visual lights showing glide slope guidance.

PAX

Passengers — common aviation abbreviation for the number of passengers.

PIC

Pilot In Command — pilot with final authority and responsibility for the flight.

Pitot Tube

External probe measuring ram air pressure to determine airspeed.

PPR

Prior Permission Required — advance approval needed before landing at an airport.

Precision Approach

Instrument approach with both lateral and vertical guidance (e.g., ILS, GLS).

Pressurization

Maintaining cabin air pressure above ambient to allow safe flight at high altitude.

Prop Wash

Turbulent air behind a propeller — can affect following aircraft.

Pushback

Moving an aircraft backward from the gate using a tug vehicle.

QNH

Atmospheric pressure adjusted to sea level — used to set aircraft altimeters.

Radial

Magnetic bearing from a VOR station, like a spoke on a wheel.

Reduced Vertical Separation Minimum

RVSM — allows 1,000 ft separation between FL290 and FL410.

RNAV

Area Navigation — allows aircraft to fly any desired path using onboard systems.

Runway Incursion

Unauthorized presence of an aircraft, vehicle, or person on an active runway.

Runway Threshold

Beginning of the runway portion available for landing.

RVR

Runway Visual Range — measured visibility along the runway in meters or feet.

SBAS

Satellite-Based Augmentation System — improves GPS accuracy for approaches.

SID

Standard Instrument Departure — published departure procedure from an airport.

Sidestick

Side-mounted control stick replacing the traditional yoke in fly-by-wire aircraft.

Slats

Leading edge devices that extend to increase lift at low speeds.

Slot

Designated time window for takeoff or landing at a congested airport.

Speed of Sound

Approximately 661 knots at sea level — varies with temperature.

Squawk

Four-digit transponder code assigned by ATC for aircraft identification.

Stall

Loss of lift when the wing exceeds its critical angle of attack.

STAR

Standard Terminal Arrival Route — published procedure guiding aircraft to an approach.

Stopway

Paved area beyond the runway for decelerating during aborted takeoff.

TAF

Terminal Aerodrome Forecast — weather forecast for a specific airport.

Taxiway

Paved path connecting runways to aprons, hangars, and terminals.

TCAS

Traffic Collision Avoidance System — airborne system preventing mid-air collisions.

Thrust Reverser

System redirecting engine exhaust forward to decelerate after landing.

TMA

Terminal Control Area — controlled airspace around one or more major airports.

TODA

Takeoff Distance Available — runway plus clearway for takeoff calculations.

TORA

Takeoff Run Available — runway length available for the takeoff ground roll.

Touch and Go

Landing practice where the aircraft touches down and immediately takes off again.

Transition Altitude

Altitude above which aircraft use standard pressure (1013.25 hPa) for flight levels.

Transponder

Airborne device that responds to radar interrogation with identification and altitude.

Trim

Adjusting control surfaces to maintain flight attitude without constant pilot input.

Turbulence

Irregular air movement causing sudden changes in aircraft altitude or attitude.

Uncontrolled Airspace

Class G airspace — no ATC service required, pilot responsible for separation.

V-Speeds

Reference speeds for different phases of flight (V1, Vr, V2, etc.).

VASI

Visual Approach Slope Indicator — light system showing approach angle guidance.

VFR

Visual Flight Rules — flight by visual reference to the ground and horizon.

VMC

Visual Meteorological Conditions — weather good enough for VFR flight.

VOR

VHF Omnidirectional Range — ground-based navigation beacon.

Wake Turbulence

Rotating air vortices behind an aircraft — dangerous for following traffic.

Waypoint

Geographic reference point used for navigation and route definition.

Wind Shear

Sudden change in wind speed or direction — hazardous during takeoff and landing.

Windsock

Fabric cone at airports showing wind direction and approximate speed.

Winglet

Vertical extension at the wingtip reducing drag and improving fuel efficiency.

Yaw

Rotation around the vertical axis — controlled by the rudder.

Zonal Dryer

System removing moisture from aircraft insulation to reduce weight and corrosion.

Zulu Time

UTC/GMT — universal time reference used in all aviation operations.