A Glossary of Aviation, Technical and Flight Safety Terms


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Glossary of Aviation & Technical Terms

 The following Glossary contains brief definitions of terms and acronyms used in Gremline articles. Many of our readers will be familiar with most, if not all, of the aviation and technical terms used on this site. New entrants to the world of aviation and casual readers may feel less confident when confronted with the plethora of acronyms, etc., that are the shorthand of the initiated. Our Glossary will be updated as more articles are added and as the breadth of technical coverage expands.


AAIB: Air Accidents Investigation Branch (UK).


ABS: automatic braking system.

ADF: automatic direction finding equipment.


AFIS(O): Aerodrome Flight Information Service (Officer).


AFS: Aerodrome Fire Service.


agl: above ground level.

AIC: Aeronautical Information Circular.


AME: Aviation Medical Examiner.


amsl: above mean sea level.


APU: auxiliary power unit (normally used during engine start).

ASI: airspeed indicator.


ATC: Air Traffic Control.


ATCC: Air Traffic Control Centre.

AVGAS: aviation gasoline.



BCAR: British Civil Airworthiness Requirements (UK).

BGA: British Gliding Association (UK).

BMAA: British Microlight Aircraft Association (UK).


CAA: Civil Aviation Authority (UK).


CAP: Civil Aviation Publication (UK).


CFIT: Controlled Flight Into Terrain.


CG: Centre of Gravity.


Cold Shock: The loss of body functions, or death, immediately on sudden immersion in very cold water. See also Hypothermia and Vasogenic Shock.


Controlled Airspace: Airspace closed to unauthorised aircraft (and see TPA).


CVR: Cockpit Voice Recorder.


°C, F, M, T: degrees Celsius, Fahrenheit, magnetic, true.



D&D Cell: Distress and Diversion Cell (at ATCC listening out on 121.5Mhz and 243Mhz).


Dewpoint: The OAT at which the airmass reaches saturation point.


DME: Distance Measuring Equipment.


Endurance Speed: The speed at which an aircraft’s total drag is at a minimum and thus requires minimum thrust and fuel consumption to maintain level flight.


ETA: estimated time of arrival.

ETD: estimated time of departure.

FAA: Federal Aviation Administration (USA).

FIR: flight information region.

FL: flight level (using altimeter datum of 1013mbs).

ft/min: feet per minute.


g: normal acceleration.

gall imp/US: gallons, imperial or United States.


gremlin: (RAF slang) Mischievous sprite imagined to frequent aircraft and to cause mishaps [OED].

GPS: Global Positioning System.


Ground Effect: The effect of ground interference on the airflow patterns around an aircraft when the aircraft is close to the ground.



HASELL Check: Cockpit checks prior to stall/spin, aerobatics, (practice) forced landing.

hrs: hours.


Hypothermia: The decrease of core body temperature to a level at which normal muscular and cerebral functions are impaired (and see Cold Shock and Vasogenic Shock).


IAS: indicated airspeed.

IFR: Instrument Flight Rules.

ILS: Instrument Landing System.

IMC: Instrument Meteorological Conditions (flight in cloud etc).


IMC Rating: Instrument Met. Conditions rating (peculiar to UK and invalid elsewhere).

IR: Instrument Rating

IRE: Instrument Rating Examiner.

ISA: International Standard Atmosphere



JAR-OPS: Joint Airworthiness Requirements – Operations (European Union regulations).

kg: kilogram(s).


KIAS: knots indicated airspeed.

km: kilometre(s).

kt: knot(s).


LAMS: Light Aircraft Maintenance Schedule (UK).


LASORS: Licensing, Administration, Standardisation, Operating Requirements and Procedures (UK).


Lexicographer: A writer of dictionaries [or glossaries?], a harmless drudge.” Samuel Johnson.

Lift Induced Drag: Drag resulting from turbulence originating in the wingtip vortices that are created when the wings begin to generate lift.


LDA: Landing Distance Available.

LRA: Landing Run Available.


LTE: Loss of Tail Rotor Effectiveness in helicopters. A low speed aerodynamic characteristic that can result in an uncommanded rapid yaw rate that does not subside of its own accord. Also known as ‘unanticipated yaw’ or ‘loss of tail rotor authority’.



mb: millibar(s).

MDA: Minimum Descent Altitude (approach limitation).


METAR: Meteorological Airfield Report.


mm: millimetre(s).

mph: miles per hour.


MRT: Mountain Rescue Team.


MTWA: Maximum Total Weight Authorised.


MTOW: Maximum Take-off Weight.


MOGAS: motor gasoline (as distinct from AVGAS).

NDB: non-directional radio beacon.

nm: nautical mile(s).

NOTAM: Notice to Airmen.



OAT: Outside Air Temperature.

OCH: Obstacle Clearance Height.



PAPI: Precision Approach Path Indicator.


PAR: Precision Approach Radar.

PFA: Popular Flying Association (UK).

PIC: pilot in command.


PIO: Pilot Induced Oscillation.

psi: pounds per square inch.


QFE: altimeter setting to read zero at airfield level.


QNH: altimeter setting to indicate height amsl.


RCC: Rescue Co-ordination Centre.

RPM: revolutions per minute.

RVR: runway visual range.


SAFETYCOM: Frequency for use in certain circumstances by aircraft operating in the vicinity of UK aerodromes and landing sites that do not have a frequency assigned for communication. Introduced on 11 November 2004. Full details can be found on the Civil Aviation Authority web site at www.caa.co.uk.

SAR: Search and Rescue.


Slow Flying: Flight at any airspeed less than Endurance Speed (q.v.).


SSLs: Safety Sense Leaflets, published by the UK Civil Aviation Authority.

SSR: secondary surveillance radar.


STOL: Short Takeoff & Landing


TAF: Terminal Airfield Forecast.


TAS: true airspeed.


TODR: Take-off Distance Required.


TORA: Take-off Run Available.


TORR: Take-off Run Required.


TPA: Temporary Prohibited Area. Airspace closed to unauthorised aircraft (and see Controlled Airspace).


Thermal Runaway: In batteries. Can occur if rating capacities are exceeded. Involves violent gassing, boiling of the electrolyte, damage to the plates and even melting of the battery case or explosion.


Unanticipated Yaw: In helicopters. See LTE – Loss of Tail Rotor Effectiveness.


UCT: Universal Co-ordinated Time (replacing Greenwich Mean Time).



Vasogenic Shock: When the body is immersed in water in a vertical position for some time, the water pressure reduces the tendency for blood to pool in the lower limbs, keeping the blood pressure higher in the body core. When the body is lifted vertically from the water the blood rushes downwards into the legs causing a drop in blood pressure that can lead to heart failure. Winchmen will therefore try to lift survivors out of the water in a horizontal position. And see Hypothermia and Cold Shock.


Va: design manoeuvring speed (or turbulence penetration speed).


Venturi Effect: Increase in the speed of flow of gasses or liquids caused by a constriction or bend in the containing duct.


VFR: Visual Flight Rules.


VMC: Visual Meteorological Conditions.


Vne: never exceed speed.


VOLMET: Voice Met. Broadcast.


VRP: Visual Reporting Point.


VSI: vertical speed indicator.


Vy: speed for best RATE of climb.


Vx: speed for best ANGLE of climb.


WAT: Weight, Altitude, Temperature. Variables that affect takeoff performance.



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