Some definitions

[center]This is a list of words belonging in the commercial aviation vocabulary. Definitions were assembled from many sources, compiled by James Allan, Mike Jerram and Tony French. Some definitions use words in the glossary and are identified by an asterisk (*).


A

AB: Air Base. More often used when describing a military airport.
ACARS: Aircraft Communication Adressing and Reporting System
ADELT: Automatically Deployable Emergency Locator Transmitter. Synonym of ELT*.
ADF: Automatic Direction Finder. Radio compass giving a relative bearing to a NDB*.
ADI: Attitude Deviation Indicator. Enhanced artificial horizon with pitch and roll information. It is part of a flight director system.
ADT: Approved Departure Time
AFB: Air Force Base
AFCS: Automatic Flight Control System. It is an advanced autopilot.
AFDS: Autopilot and Flight Director System
AGL: Above Ground Level
Alternate: Airport indicated on a flight plan where it is possible to divert the aircraft from its scheduled destination (in case of bad weather or any other major situation).
Altimeter setting: barometric pressure reading in millibars (e.g. 1015), or inches of mercury (e.g. 29.80) used to set a pressure altimeter's sub-scale to QFE or QNH*.
APP: Approach control
APU: Auxiliary Power Unit. Device (usually a small turbine) that provides power for engine-starting and other systems while on the ground. Such device is present on large aircraft and some business jets, and replaces the GPU*.
ARTCC: Air Route Traffic Control Centre
ATA: Actual Time of Arrival
ATC: Air Traffic Control
ATCC: Air Traffic Control Centre
ATIS: Automatic Terminal Information Service. Automatically recorded message transmitted on a particular frequency, containing current weather conditions, QNH* setting, active runways, etc., provided at the major airports.
AVGAS: Aviation Gasoline. Usually followed by the octane rating. Used by piston-engined aircraft.
AVTUR: Aviation Turbine fuel (kerosene). Used by turboprops and jet aircraft.


B

Base: Base of operations or a hub* for an airline. The base leg is also one of the many words describing the approach segments. See Final* for a diagram.
Bleed air: Hot compressed air taken from turbine engines.
Black Box: Popular name given to either the CVR* or the FDR* used to investigate an accident.
BRG: Bearing. Horizontal direction to/from a point, expressed in degrees (e.g. 000 or 360 is North, 090 is East).


C

Callsign: Phrase used in radio transmissions to identify an aircraft, before proceeding to actual instructions. A callsign for a commercial aircraft may be "Swissair 111" or "TWA 800". As for a private plane, it could be something like "Cessna 13 Whisky", "Baron 232 Zulu" or "November 17 Victor". See the Communications section of the reference.
Capt: Captain
CAS: Calibrated Airspeed. IAS* corrected for air density and compressibility.
CDI: Course Deviation Indicator. The vertical needle of a VOR* indicator which shows the aircraft's position relative to the selected VOR radial*.
Ceiling: Height above ground or water level of the base of the lowest layer of cloud, below 20,000 feet, covering more than half of the sky. Service ceiling also means an aircraft's density altitude* at which its maximum rate of climb is lower or equal to 100 feet per minute. The absolute celing is the highest altitude at which the aircraft can maintain level flight.
CFB: Canadian Forces Base.
Clearance: Authorization given by ATC* to proceed as requested or instructed, e.g. "Cleared for take-off", "Cleared for visual approach", "Cleared to land".
COMAT: Company Material. Non-revenue* cargo, such as aircraft spare parts.
Crosswind: Wind perpendicular to the motion of the aircraft. The crosswind leg is also one of the many words describing the approach segments. See Final* for a diagram.
CRT: Cathode Ray Tube. Television-like screens used in flight decks of new-generation aircraft, replacing the conventional instruments. See also EFIS*.
CVR: Cockpit Voice Recorder. One of the so-called "black boxes". It is a device recording the last 30 minutes of sound inside the cockpit, before impact. Sounds recorded include all conversations, radio transmissions, and background noise.
CWR: Color Weather Radar


D

DCT: Direct
Dead-heading: See Repositioning*.
Density altitude: pressure altitude (as indicated by the altimeter) corrected for air temperature.
DH: Decision Height. Height on a precision approach at which the pilot must have the runway approach lights in sight to continue descent, or if not, initiate a go-around*. Below the DH, the pilot has no other choice than land the plane.
DI: Direction Indicator. A gyro instrument which indicates the magnetic heading of an aircraft. The DI, also known as the directional gyro (DG), is free of the turning errors associated with magnetic compasses but is prone to precession (wander) and must be reset against the magnetic compass at intervals.
DME: Distance-Measuring Equipment. A combination of ground and airborne equipment which gives a continuous slant range distance-from-station readout by measuring time-lapse of a signal transmitted by the aircraft to the station and responded back. DMEs can also provide groundspeed and time-to-station readouts by differentiation.
Downwind: One of the many words describing the approach segments. See Final* for a diagram.


E

EAT: Estimated (or expected) Approach Time
ECAM: Electronic Centralized Aircraft Monitor. A form of CRT*
EFIS: Electronic Flight Instrument System, in which multi-function CRT* displays replace traditional instruments for providing flight, navigation and aircraft systems information, forming a so-called "glass cockpit".
EGT: Exhaust Gas Temperature. One of the flight deck's engine gauges.
EICAS: Engine Indication and Crew Alerting System. A CRT display indicating engine performance and alerts.
ELT Emergency Locator Transmitter. Small radio transmitter fixed on the aircraft's structure, automatically activated by impact or water immersion, transmitting a code enabling SAR satellites or search units equipped with Direction Finders to locate the aircraft's crash site. Also called ADELT or ELB (Emergency Locator Becon).
ER: Extended Range. Suffix used by some aircraft models, e.g. Boeing 767-300ER.
ETA: Estimated Time of Arrival
ETD: Estimated Time of Departure
ETE: Estimated Time Enroute
ETOPS: Extended-range Twin Operations. Certification given to two-engine aircraft for long overwater flights. Popular deformation of this term is "Engines Turning Or Passengers Swimming"!


F

F/A: Flight Attendant. Also known as Air Hostess in the UK, formerly known as Steward(ess) in North America.
FAA: Federal Aviation Administration. Organization in charge of defining the aviation safety standards in the USA. Its equivalent in the United Kingdom is the Civil Aviation Authority (CAA).
FBO: Fixed-Base Operator. Supplier of fuel, maintenance, aircraft rental or sale, flight training, etc, at the airport.
FBW: Fly-By-Wire. Aircraft controls where the pilot's commands (bank, yaw...) are transmitted to control surfaces electronically or via fiber optics, instead of mechanical linkage. Also called FBL (Fly-By-Light).
FDR: Flight Data Recorder. One of the so-called "black boxes". It is actually painted bright orange to be easily identified among aircraft debris, and records various parameters such as altitude, heading, airspeed, engine statistics, etc... It is used to investigate in the case of an accident.
F/E: Flight Engineer. Also known as Second Officer.
Ferry flight: See Repositioning*.
Fin number: See FN* below.
Final: Final Approach. One of the many words describing the approach segments. The part of a landing sequence or aerodrome circuit procedure in which the aircraft has made its final turn and is inbound to the active runway. See picture at right.
FL: Flight Level. Altitude at barometric setting of 1013.2 millibars or 29.92 inches of mercury, expressed in rounds hundreds of feet. This is usual mostly above 18,000 feet. FL350 is 35,000 feet.
F/O: First Officer. Also known as Co-Pilot.
FMS: Flight Management System
FN: Fleet Number. Internal number, for the use of the airline, identifying a particular aircraft within the fleet.
FPL: Filed Flight Plan
FPM: Feet Per Minute. Unit of measure of an aircraft's rate of climb or descent.


G

GND: Ground
Go-Around Balked approach, when the aircraft climbs away from the runway during the approach, to either start the approach again, or proceed to the alternate* airport.
GPS: Global Positioning System (Navstar). Navigational system using orbiting satellites to determine the aircraft's position on the Earth. Developed at first for military use, then widespread on commercial and private aircraft, it is now expected to replace the ground-based navigational systems for its accuracy and reliability.
GPWS: Ground Proximity Warning System. A radar-based flight deck system to give pilots audible warning by means of horns, hooters, taped or synthetic voices of terrain close beneath an aircraft's flight path. One of the GPWS' warnings might be: "TERRAIN! WHOOP WHOOP! PULL UP!" or "WINDSHEAR! WINDSHEAR!".
Ground speed: Actual speed of an airplane as measured relative to the ground.
GS: Glideslope. Vertical guidance, part of an ILS, establishing the safe glidepath to a runway. A standard ILS glideslope is 3 degrees.


H

HDG: Heading. The direction in which an aircraft's nose points in flight in the horizontal plane, expressed in compass degrees (e.g. 000 or 360 is North, 090 is East).
Heavy: Suffix used in radio transmission callsigns* (e.g. "United 492 Heavy") to indicate the aircraft is capable of generating wake turbulence*.
Holding pattern: Manoeuver consisting of making the aircraft turn around the aerodrome at an assigned altitude, while awaiting further ATC* instructions.
HSI: Horizontal Situation Indicator. A cockpit navigation display, usually part of a flight-director system, which combines navigation and heading.
Hub-and-spoke: Route system in which an airline will fly the majority of its flights from/to the same city (the hub), thus offering several connecting possibilities, as opposed to fly a series of point-to-point flights. Example: instead of flying non-stop from Los Angeles to New York, from Phoenix to Washington, from Las Vegas to Boston, etc., an airline will offer all these routes via its hub in Chicago.


I

IAS: Indicated Airspeed. Airspeed indicated by the Airspeed Indicator (ASI), without correction for position error, altitude, or outside air temperature.
IATA: International Air Transport Association
I/C: In Charge.
ICAO: International Civil Aviation Organisation
IFR: Instrument Flight Rules prescribed for the operation of aircraft in instrument meteorological conditions.
ILS: Instrument Landing System. Consists of the localizer, the glideslope and marker radio beacons (Outer, Middle, Inner). It provides horizontal and vertical guidance for the approach.
INS Inertial Navigation System. It uses gyroscopes and other electronic tracking systems to detect acceleration and deceleration, and computes an aircraft's position in latitude and longitude. Its accuracy, however, declines on long flights. Also called IRS, or Inertial Reference System.


K-L

Knot (kt): Standard unit of speed in aviation and marine transportation, equivalent to one nautical mile per hour. One knot equals 1.1515 mph, and one nautical mile equals 6,080 feet. The word "knot" replaces "nautical miles per hour", and one should never say for example "60 knots per hour".
Lat: Latitude
LATCC: London Area and Terminal Control Centre at West Drayton, near London's Heathrow Airport.
LN: Line Number. Priority of the aircraft in the manufacturer's* line. A Boeing 757-200 with a LN of 275 was the 275th plane of its type to be built.
LOC: Localizer. The azimuth guidance portion of an instrument landing system.
Lon(g): Longitude
LORAN: Long-Range low-frequency Radio Navigation. Its range is about 1,200 nm by day, and 2,300 nm by night.