Aviation Terms & Acronyms

Please our our extensive list of aviation terms and acronyms to help better understand some of the industry terminology.  If you see any that we have missed or that you have questions about, please contact us and we will be sure to get your suggestions added.

AC – Advisory circular.

A/C – Airconditioning Unit

ACARS – Airline communications and reporting system.

Actuator – component that deflects a control surface or, in hydraulics, moves a structure such as a landing gear

AD – Airworthiness Dirctive. Maintenance or modification ordered by FAA.

ADC – Air Data Computer

ADF – Automatic Direction Finder

ADI – Attitude direction indicator

ADS – Automatic dependent surveillance.

AES – Aircraft Earth station.

AFCS – Automatic flight control system.

AFD – Adaptive flight displays.

AFDS – Autopilot flight director system.

AFIS – Automated flight information system (AlliedSignal)

AHRS – Attitude-heading reference system.

AI – Altitude indicator

aileron – A small hinged portion of an airplane’s wing, used to make an airplane roll, or turn around its long axis.

air data – Values cmputed from pitot, static and temperature measurements, usually by means of a digital computer; ARINC 575 defines outputs.

airfoil – A surface, such as an airplane wing, shaped to produce more lift than resistance when driven through the air.

All-weather fighter – A radar-equipped jet fighter airplane which can operate at night or in the worst weather.

All-weather interceptor – A radar-equipped jet fighter airplane which can operate at night or in the worst weather.

AM – Amplitude modulation.

AME – Aviation Medical Examiner (U.S.)

AMLCD – Active-matrix liquid crystal display.

AMOC – (logbook term – Alternate Method Of Compliance – with an AD, requires FAA LOA)

Annual – Mandatory inspection of airframe and powerpland that occurs every 12 months.

AOA – Angle-of-attack

AP – Auto Pilot

APR – Auxiliary Power Reserve

APU – Auxiliary power unit

ARINC – Aeronautical Radio, Inc. A nonprofit corporation owned by member airlines to define form, fit and function of avionics equipment and to provide radio communication services.

ARINC 419 – Digital information transfer characteristics as applied in ARINC 500-series equipment specifications.

ARINC 547 – Digital specification for ILS reference sensors.

ARINC 561 – Inertial navigation system specifications.

ARINC 568 – Inertial sensor DME reference specification.

ARINC 571 – Inertial sensor attitude-heading reference system specifications.

ARINC 575 – Digital air-data system specifications.

ARINC 700-series – All-digital equipment specifications for new-generation transport category aircraft.

ARINC 743 – All-digital specificaitons for FANS-1 compatibilty.

ASA – Autoland status annunciator.

ASCB – Avionics standard communication bus (Honeywell)

A/T – Auto throttle.

ATC – Air Traffic Control. The people in control towers (at airports that have them) to regulate takeoffs, landings, and planes moving through their general area.

ATI and ATR – ARINC from factors.

ATM – Air traffic management.

ATP – Airline Transport Pilot (the “highest” grade of pilot certificate)

Audio Panel – Electronic device used to switch between radios.

Autogyro – An aircraft equipped with a rotating wing, or rotor, to sustain itself in the air, and a propeller to move forward.

AUX Fuel – Auxiliary fuel tanks.

AWACS – Airborne Warning And Control System. An electronically very souped-up Boeing 707. [Pronounced “AY-wax.”]

Barnstormer – A pilot who, in the early years of aviation, gave airplane rides to people and performed aerobatics for a fee.

Basic Operating Weight (BOW)

Empty weight typically equipped + unusable fuel and trapped liquids + 2 pilots (400 lbs.) + supplies.

BCD – Binary coded decimal.

Beam width – The included angle of a weather radar interrogation signal.

Bendix – Avionics mfgr.

BITE – Built-in test equipment.

Bleed Air – High pressure air ducted from engine to pressurize cabin and other uses.

Boeing -“The Boeing Company, with headquarters in Seattle, Washington, U.S., is the world’s leading manufacturer of commercial airplanes and one of the nation’s largest exporters. The company is a major U.S. government contractor, with capabilities in space systems, helicopters, military airplanes, missile systems, information and electronic systems and software products.”

Boots – Inflatable device on leading edge of wings and tail. Used to remove ice.

Bracing wire – A solid steel wire used to support the structure of an airplane’s wings or fuselage.

BRG – Bearing.

BSU – Beam steering unit.

CAB – Civilian Aviation Board.

Cabin pressurization – A mechanism used to maintain air pressure in an airplane’s sealed cabin at a level suitable for passengers.

Canard – An airplane designed to have its normal horizontal tail surface on the front rather than the rear of its fuselage.

Caster – To swivel or rotate slightly.

Category I (CAT I) – An ILS facility providing operation down to a 200 foot decision height and an RVR of not less than 2,400 feet.

Category II (CAT II) – An ILS facility providing operation down to a 100-foot decision height and an RVR of not less than 1,200 feet.

Category IIIa (CAT IIIa) – An ILS facility providing operation with no decision height to and along the surface of the runway with external visual reference during the final phase of landing and with an RVR of not less than 7000 feet.

Category IIIb (CAT IIIb) – An ILS facility providing operation with no decision height limit to and along the surface of the runway without reliance on external visual reference and, subsequently, taxiing with an external RVR of not less than 150 feet.

Category IIIc (CAT IIIc) – An ILS facility providing operation with no decision height limit to and alsont the surface of the runway and taxiways without reliance on external visual reference.

CAVU – Ceiling And Visibility Unlimited. Perfect flying weather — no major clouds, no major haze.

CD-ROM – Compact disc read-only memory.

CDU – Control-display unit.

Centre-pod configuration – A type of airplane whose fairly short fuselage is not connected to the tail surfaces.

CESC – Cescom Maintenance Program.

CFI – Certified Flight Instructor.

CMOS – Complementary metal oxide semiconductor.

CMU – Communications management unit.

CNS – Communications, navigation and surveillance.

Coherent detection – A technique used in certain ADF receivers to improve useful range.

Collins – Avionics mfgr.

COM – Communications.

Comosite video – Analog VOR receiver output before processing.

CONT – Teledyne-Continental (engine mfgr.)

Contact digitizer – A mechanical device that converts analog information to digital codes by means of electrical contacts.

Cowling – A removable metal covering placed over and around an airplane’s engine(s).

C/R – Counter-rotating propellers.

Cross-over exhaust – A mechanism through which the exhaust from one side of an inline engine is carried to the other.

CRT – Cathode ray tube.

CSDB – Commercial standard data bus.

CVR – Cockpic Voice Recorder. Device that records crew conversations. Used in accident investigations.

CW – Continuous wave. A radio carrier broadcast that does not have modulation.

Cycles – Pertaining to turbine engines. Cycle begins with starting, continues through full-power, and ends with shutdown.

DA – Drift angle.

DADC – Digital air-data computer.

dB – Decibel.

DG – Directional gyro.

DGPS – Differential global positioning system. LA- prefix refers to local area DGPS; WA- prefix refers to wide-area DGPS signal retransmission schemes.

Digitizer – Any electronic device capable of converting information to a digital format; usually refers to encoding devices that convert sensed altitude into a transponder code.

DME – Distance Measuring Equipment.

DP – Deal Pending.

DR – Ded (deduced) reckoning.

drms – Distance root mean squared.

DTK – Desired track.

DTU – Data transfer unit.

Duplex – Separate channels for transmitting and receiving.

EAROM – Electrically alterable read-only memory, a type of digital memory device.

EEPROM – Electrically erasable programmable read-only-memory.

EEVIP – Early Extended Validation Integration Program. An FAA program, first implemented for the Boeing 777, to give “out-of-the-box” ETOPS clearance to a new plane, rather than waiting for a couple of years of domestic service experience.

EFIS – Electronic Flight Instrument System

EGT – Exhaust gas temperature indicator.

EICAS – Engine indicating and crew alerting system.

Elevator – A small control surface hinged to the rear of the horizontal stabilizer and used to tilt an airplane up or down.

encal – Encoding Altimeter

Encoder – Displays aircraft’s altitiude on ground-based radar screens.

Engine cowl – A removable metal covering placed over and around an airplane’s engine.

EROS – Brand Name for Oxygen Mask

ETOPS – Extended Twin-engine operations. FAA designation of over-ocean flights far from possible emergency landing strips, in which the possibility of engine failure in a twin-engine plane represents a heightened risk. ETOPS certification is not normally given to a new passenger aircraft until it has been in regular domestic service for at least a year.

FAA – Federal Aviation Administration.

FADEC – Full authority digital engine control.

Fairing – A section of aircraft surface, or an attached structure, designed to reduce drag. For example, the contoured sheet metal where wing meets fuselage.

FAR – Federal Aviation Regulations (U.S.)

FAR 36 Noise Levels – In order to meet FAR 36 Stage 3 requirements, the maximum noise level permitted is:

*Take Off 89.0 EPNdB

*Sideline 94.0

*Approach 98.0

FDE – Fault detection and exclusion (GPS)

FDR – Flight Data Recorder

FDS – Flight Director System

FFON – Flight Phone

Flare – The point where an airplane floats above the runway just before touchdown.

Flight Data Recorder – Electronic device that records aircraft maneuvers. Used in accident investigations.

Flight Phone – Air-to-ground telephone system.

FM – Frequency modulation.

FMCS – Flight management computer system.

FMS – Flight Management System

FOG – Fiber-optic gyro.

Forward elevator – A control surface used to tilt an airplane up or down and mounted on the front rather than the rear of an airplane.

Full De-ice – Complete anti – and/or de-ice equipment installed on wings, tail, props, and windsheild.

Full Panel – All gyros necessary for instrument flight.

Galley – On-board meal service equipment.

Gas discharge – A type of luminescent digital display.

GCR – Ground clutter rejection.

GE – General Electric. They make aircraft engines.

GLU – GNSS landing unit. Provides precision GPS guidance to the runway in Category III operations.

GNSS – Global navigation satellite system.

Gold Crown – Trade name owned by King Radio Corp.

GPADIRS – Global positioning, air data, inertial reference system.

GPS – Global positioning system.

GPWs – Ground Proximity Warning System

Ground Air – A/C unit to cool aircraft while on the ground.

GS – Groundspeed.

G/S – Glide slope reciver and indicator.

GTWO – Gross Take off Weight

HF – High Frequency radio equipment.

HF COM – High Frequency Communication.

HIRF – High intensity radiated field.

HP – Horsepower.

HPA – High-power amplifier.

HUD – Head-up display.

Hz or Hertz – Cycles per second, used to describe radio frequencies; usually with the prefix k for kilo (one thousand), M for mega (one million) or G for giga (one billion).

IAC – Integrated avionics computer. Central processor of a Honeywell integrated cockpit system.

IAPS – Integrated avionics processing system. Central processor of a colins integrated cockpit system.

IAW – (logbook term – In Accordance With – and AD or SB)

IFR – Instrument Flight Rules. An Instrument Rating is further training after a Pilot’s license to allow pilots to fly in bad weather. The pilot has been trained to not merely fly by instruments alone, but also to understand the Air Traffic Control system, because an IFR flight is continuously monitored by ATC, radar, flight following, and a dozen other agencies.

ILS – Instrument Landing System.

In-line engine – An engine in which the cylinders are mounted in a straight line or else in two, connected at an angle.

INS – Inertial Naviagation System

INT – Interior.

ITC – Investment tax credit.

ITU – International Telephone Union, refers to certain HF channels.

IVSI – Instantaneous vertical speed indicator.

Jet Prop – Describes aircraft using turbine engines to drive propellers.

King – King Radio Corp. (Avionics mfgr.)

Known Icing – FAA certified for flight into icing conditions.

Laser IRS – An inertial reference system deriving angular rate information by measuring Doppler shift between two contra-rotating light beams.

Lateral control – The ability to make an airplane roll, or turn around its long axis, according to its pilot’s wishes.

L-band – A radio frequency between 890 and 1550 MHz.

LCD or LC – Liquid-crystal display.

Leading and trailing edges- The foremost and rearmost edges of a wing.

LED – Light-emitting diode.

LMB – Light marker beacon.

LNAV – Lateral navigation guidance.

LOA – Letter Of Authorization

LOC – Localizer receiver and indicator.

Looks per minute – Scanning or sweep rate of a wather radar antenna.

LOP – Line of position.

Loran-C – Hyperbolic grid navigation system based upon measured time differences (TD) from pulse transmissions.

LRT – Long range fuel tanks.

LRU – Line replaceable unit.

LYC – Avco-Lycoming (Engine mfgr.)

Maximum Payload = Maximum Zero Fuel Weight – (minus) Basic Operating Weight

MCU– Minimum configuration unit.

MDAU – Maintenance data acquisition unit.

MDH – Major damage history.

MFD – Multifunction display. The third or fifth tube in an EFIS, it replaces the weather radar screen and displays radar data, navigation maps, checklists and other information.

Microline – Trade name owned by Collins.

MNPS – Minimum navigational performance specificaitons.

MLS – Microwave Landing System

Mode- A – A transponder which does not give the controllers altitude information

Mode-C – A transponder and encoding altimeter which together give air traffic controllers altitude information

Mode-S – A transponder which features unique identification per unit, the potential for low-speed up and down datalinks, and “selective interrogation” triggered by ground facilities

MOH – Major overhaul.

MOPS – Minimum operational performance standard (RTCA)

MSP – Maintanance Servie Program. (Garret engine)

NARA – NARA is a professional trade association of 54 reputable business companies organized to promote the growth and public understanding of the aircraft resale industry. Its members abide by a 12-point Code of Ethics that provides standards of business conduct regarding aircraft transactions.

NAT – North Atlantic Tracks.

Nautical Mile – Measurment of distance. Equals 1.15 statute miles.

NAV – Navigation Receivers

NAV/COM – Navigation and communication radios combined in a single unit.

NBAA IFR Fuel Reserves = Fuel for go-around at destination airport + climb to 500 ft. and hold for 5 minutes + fly to and land at alternate airport 200 NMi. away + fuel to hold at 5000 ft. for 30 minutes.

NDB – Non-Directional Beacon – an older type of electronic navigation aid, basically a low-power AM radio station

NDH – No Damage History

NMS – Navigation management system.

NMU – Navigation management unit.

NTSB – National Transportation Safety Board. Investigates airplane accidents. Plays at most an advisory role in flightworthiness accreditation.

NVM – Nonvolatile memory. Digital memory that retains information through system shutdown.

OAT – Outside Air Temperature.

OBS – Omnibearing Selector – part of a VOR receiver system, which allows the pilot to select a course to or from a VOR station

OFUELWT – Zero Fuel Weight.

OH – Overhaul.

Omega – A very-low-frequency navigation system.

Opitcal digitizer – Any device using a photosensor that can convert analog informatin to digital code.

OXY – Oxygen system for passengers and crew.

Payload with Full Fuel = Useful Load – (minus) Usable Fuel

PBH – Power by the Hour. (Rolls Royce engines)

PC – Positive Control. (Trade name for Mooney Aircrft wing leveler)

PAR – Precision Approach Radar – a ground-radar based instrument approach which provides both horizontal and vertical guidance

Peak power output – The maximum transitter power output measured over a short time; usually used to rate pulse transmissions.

PEP – Peak envelope power. A standard electronic rating of any AC source, including a radio transmitter.

PNT – Paint

port – Nautical usage adopted in aviation. The left side, as determined by an observer in the vehicle, when vehicle and observer are right side up, and observer is looking “forward” (in the normal direction of travel of the vessel or vehicle).

PSI – Pounds per square inch.

PTT – Push-to-talk (switch)

Pulse – A transmission of very brief duration used to carry information by using time measurement or as a series of pulses representing code.

PVT – Private (pilot certificate)

PW – Pratt & Whitney, the world’s leading designer, developer and manufacturer of gas turbine engines for commercial, military and general aviation aircraft.”

RA – (1) Radio altitiude; (2) Resolution advisory (TCAS)

radal – Radio Altimeter

Radar – On-board weather radar.

Radar Altimeter – Device that senses aircraft’s height above the terrain. Different from normal (barometric) altimeter.

Radome – A detachable nose cone made of plastic-type material, used to cover and protect an airplane’s radar antenna.

RAIM – Receiver autonomous integrity monitoring (GPS)

RAM – Random access memory.

Ramjet – A type of jet engine with very few moving parts which consists of a specially shaped tube open at both ends.

Rate of roll – A measure of the speed with which an airplane can turn around its long axis, or roll.

RCA – Avionics mfgr.

RCU – Radio control unit.

Reversers – System for braking aircraft during landing roll.

RFU – Radio frequency unit.

RG – Retractable landing gear.

RMI – radio magnetic indicator – an ADF-like display with a pair of pointers which might be attached to either VOR or ADF receivers

RNAV – Area navigation device.

RNP – Required navigation performance.

ROM – Read-only memory.

RR – Rolls Royce makes engines for a variety of aircraft, including the Boeing 777 and Airbus 330.

RT – Receiver-transmitter combined in a singel line-replacable unit.

RTCA, Inc. – An association of U.S. governmental and industry aeronautical organizations dedicated to advancing aeronautics through consensus and recommendations.

Runway XX – Runways are numbered after magnetic compass points, minus the 1’s column (where North is 0, and 360, degrees).

RVSM – Reduced Vertical Seperatation Minimum

SAR – Search and rescue.

SB – Service Bulletin

SL – Service Letter

Satcom – Satellite communications system.

SDU – Satellite data unit.

SELCAL – Selective Calling system (used primarily with HF)

Service ceiling – The altitude above sea level beyond which an airplane can no longer climb more than 30 m(100 ft) per minute.

Servo Tab – moves control surface using aerodynamic force

Servo – device that moves an actuator

SHP – Shaft horsepower. (refers to turbine engines.)

Silver Crown – Trade name owned by King Radio.

Simplex – Single frequency for both transmitting and recieving in communications; generally implies a push-to-talk function and verbal procedures.

Slaved compass – North-seeking gyro-stabilized compass system. Technically superior to DG.

slip – A way to lose altitude in a hurry (on purpose), or slide into a final approach during a heavy wind. The technique is to put nearly full rudder in one direction, and then bank in the opposite. This keeps the plane almost level, except pointing to one side.

SMOH – Since major overhaul.

SMPI – Time Since Major Periodic Inspection

SN – Serial Number.

Spar – A principal section of the wing structure of an airplane, going from tip to tip.

Sperry – Avionics mfgr.

SPOH – Since prop overhaul.

Squawk – A 4-digit (actually 4-octal-digit -> 12-bit) number which is set into a transponder by the pilot to identify the aircraft to air traffic controllers

Squitter – The transmission of a specified reply format at a minimum rate without the need to be interrogated (transponders)

SSB – Single sideband. A highly efficient form of radio transmission wherein information is carried on a sideband instead of the center carrier in order to gain range performance; usually used in HF communication transceivers.

SSCVR – Solid state cockpit voice recorder.

Stall – The point at which wings fail to generate enough lift to keep the plane stable.

Starboard – Nautical usage adopted in aviation. The right side, as determined by an observer in the vehicle, when vehicle and observer are right side up, and observer is looking “forward” (in the normal direction of travel of the vessel or vehicle).

STC – (1) Supplemental Type Certificate. (2) Sensitivity-time compensation. In weather radar, a technique and circuit for calibrating a display.

STOL – Short takeoff and landing ability.

sumps – Points underneath each fuel tank to test for contamination like water or other debris.

Supercharged – Method for increasing engine power.

Synchro – Any device capable of converting mechanical position into an analog electronic signal.

Synthesizer – Frequency synthesizer, an electronic circuit capable of generating multiple frequencies from a single crystal oscillator.

Swept-wing – A wing in which both the leading and trailing edges are slanted backward, to reduce air resistance at high speed.

Synch – Engine Fan Synchronizer

TA – Traffic advisory (TCAS)

TBO – Time between overhaul

TCAS – Traffic Collison Avoidance System. TCAS-I provides warnings (TAs) of other nearby aircraft; TCAS II provides warnings and resolutions advisories (RAs), and coordinates RAs with other TCAS II equipped aircraft via Mode S transponder.

TCDS – Type Certificate Data Sheet

TKE – Track error.

T/Rs – Thrust Reversers

Trend Monitoring – Continuous computerized observation of turbine engine performance. Used to detect early sings of wear.

Trim Tab – holds control surface at desired deflection

TSC – Total Time Since CORE

TSN – Time Since New (also TTSN)

TSO – Technical standard order. A performance specification and production compliance criteria applied to avionics and defined by FARs and the RTCA.

TT – Total Time

TTAF – Total Time Airframe

TTE – Total Time Engine

TTG, TTS or TTW – Time to go, time to station, time to waypoint.

Turbo prop – Is said of an airplane powered by a type of jet engine, the turbo prop, equipped with a turbine-driven propeller.

Turbulence mode – Flight control system mode in which a “softer” response to gust upsets is programmed.

TX – Transponder

Undercarriage strut – A part of an airplane’s structure, designed to resist distortion, which supports the landing gear.

Usable Fuel (lbs) = Usable fuel (gallons) x 6.7 lbs/gallon

Useful Load = Maximum Ramp Weight – (minus) Basic Operating Weight

UTC – Universal Coordinated Time.

VAC – Volts alternating current.

VDC – Volts direct current.

VFR – Visual Flight Rules. Private Pilots start as VFR certified. This means that, in most cases,they must have about 3 miles of visibility, be 500 feet below clouds, 1000 feet above clouds, and/or 2000 feet next to clouds at a bare minimum. Unless they have an Instrument Rating (and all the associated control along with that…see IFR), they are required to avoid all clouds and weather.

VHF – Very High Frequency radio equipment.

VLF – Very Low Frequency

VNAV – Vertical navigation, or the capability to compute pitch-axis maneuvers and altitude-related points in space.

VOR – VHF Omnidirectional Receiver. One of the more common navigational aids that the FAA has dropped all over the country (and sometimes the world). A VOR sends out a radio signal that is slightly different in each direction (the difference is phase, if you want to get technical). So, an airplane’s VOR tool listens to the VOR, and by measuring the difference in the radio, it can tell which direction it is from the VOR. Since your chart will show where the VOR is, and you now know where you are in relation to the VOR, it has helped you figure out where in the local area you might happen to be.

WAAS – GNSS wide-area augmentation system.

Wet wings – Method for containing fuel in wings without using rubber fuel cells.

Wing fence – Term preferred by Airbus and McDonnell-Douglas aircraft manufacturers for the vertical structures at the outside ends of the wings of some of their jets. More at winglet.

Winglet – Term preferred by Boeing for the vertical structures at the ends of the wings on their 747-400. Airbus and McDonnell-Douglas aircraft manufacturers use the term “wing fence.” The 747-400 winglets only rise from the end of the wing. MD-11 and Airbus wing fences extend both above and below the wing.

WPT – Waypoint.

Xpond – Transponder

X-band – Frequency range in which most general aviation weather radars operate.

XTK – Cross track; cross track error.

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