Definitions and Jargon
1179 - Flight test to add a new aircraft type to a professional license -- actually the number of the test form used.
AA - American
AAATS - Australian Advanced Air Traffic Services
AAC - Aeronautical Administration Communication (a class of communication which supports administrative communication)
AAIB - Air Accident Investigation Branch of the Department of Transport. ( UK )
AAE - Above Airport Elevation.
AAL - Above Airport Level.
AAS - Advanced Automation System (the end systems for all FAA air traffic control, located at the ARTCCs)
ab initio - literally `from the beginning', elementary flying training.
abm abeam - an aircraft is abeam a point when that point is at ninety degrees left or right of the aircraft's track, but term usually used to indicate a general position rather than a specific point.
A/C - Aircraft.
AC - Air Canada.
ACARS - Aircraft Communication Adressing and Reporting System.
ACAS Airborne Collision and Avoidance System
ACC - Area Control Center.
ACCEL - Acceleration, Accelerate.
Accelerate-Stop Distance - Calculated distance required for an aircraft to accelerate to V1, reject take-off and brake safely to a halt.
ACF Area Control Facility
ACFS Advanced Concepts Flight Simulator (a generic "glass cockpit")
ACFT - Aircraft.
ACMS - Aircraft Condition Monitoring System.
ACR - Airport Control Radar.
ACT - Active.
ACZ - Airport Control Zone.
A/D - Aerodrome.
AD - Airworthiness Directive, issued by airworthiness authorities to correct a defect found in an aircraft type after certification. Compliance is mandatory and may be required immediately and before further flight, within a specified period of time or number of flying hours, or when next due for routine maintenance.
ADC - Air Data Computer.
ADF - Automatic Direction Finder. Radio compass which gives a relative bearing to the non-directional radio beacon to which it is tuned.
ADG - Air Driven Generator.
ADI - Attitude Deviation Indicator. An advanced type of artificial horizon, part of a flight director system providing pitch and roll information and commands.
ADIRS - Air Data Inertial Reference System.
ADIRU - Air Data Inertial Reference Unit.
ADIZ - Air Defence Identification Zone. An area of airspace extending upwards from the surface, usually along a national boundary, within which identification of all aircraft is required in the interests of national security.
ADJ - Adjusted / Adjustment.
ADLP - Aircraft Data Link Processor, the Mode S subnetwork function onboard the aircraft that implements the OSI network layer protocols.
ADR - Accident Data Recorder.
ADRS - Address.
ADS - Automatic Dependence Surveillance
AEF - Airports Environmental Federation.
Aerad - UK-published flight guide and navigational chart system.
Airport/airport elevation - highest point of an Airport's usable runway(s) expressed in feet above mean sea level (amsl).
AFB - Air Force Base, usually U.S. or Canadian.
AFCS - automatic flight control system, an advanced autopilot. Also IFCS, integrated flight control system.
AFDS - Autopilot Flight Director System.
AFI - Assistant Flying Instructor.
AFIC - Assistant flying Instructor Course.
AFIS - Airport Flight Information Service, providing information to, but not control of, aircraft using that Airport. Also AFISO, AFIS officer, and AGO, air-to-ground operator.
AFS - Airport Fire Service.
AFTN - Aeronautical Fixed Telecommunications Network. A ground- based teleprinter network transmitting flight plans, weather information etc.
A/G - Air-To-Ground.
agl - Above Ground Level.
AHRS - Attitude Heading Reference System. A sensor deriving aircraft attitude and heading information from gyros and accelerometers.
AIAA - Area of Intense Aerial Activity, usually military.
AIC - Aeronautical Information Circular. Bulletins issued at intervals by the CAA relating to matters of airworthiness, administration, operating procedures, safety etc. AICs are colour-coded according to subject, e.g. safety circulars are pink, thus `Pink 12' issued in December 1990.
AIP - Aeronautical Information Publication. The UK Air Pilot, statutory bible of aeronautical information published by the CAA.
Airep - Form for reporting position and Met conditions in flight.
Airmet - CAA's telephone aviation weather service, covering Southern, Northern and Scottish regions of the UK. Also Metdial and Metplan, privately-operated aviation weather services. For full details see Pilot, February 1991.
AIS - Aeronautical Information Service. CAA unit based at London-Heathrow Airport, providing flight-planning services and information for pilots. Publishes AICs, above.
AIZ - Airport Information Zone. See ATZ below.
ALERFA - alert phase of search-and-rescue procedure.
ALPA - Air Line Pilots Association.
ALT - Altitude
ALT - Alternate
Alternate - Airport specified on a flight plan to which an aircraft chooses to divert if a landing at its intended destination is not possible (for reasons of poor weather, for example).
ALT HOLD - Altitude Hold Mode
Altimeter Setting - Barometric pressure reading in millibars, hectopascals or (in USA) inches of mercury (Hg) used to set a pressure altimeter's sub-scale to QFE or QNH.
ALTN - Alternate
AM - Amplitude Modulation
AM - Aeromexico
AME - Authorized Medical Examiner. A doctor approved by the CAA (or foreign licensing authority) to conduct examinations for the issue or renewal of aircrew medical certificates.
AMSL - Above Mean Sea Level (sometimes asl in USA).
ANA - All Nippon Airways
ANO - Air Navigation Order. Statutory legal instrument defining the laws of air navigation, pilot licensing etc, in the UK. Other aviation legislation includes the Rules of the Air and Air Traffic regulations and the Air Navigation (General) Regulations
AoA - Angle Of Attack.
AOA - Airport Operators' Association.
AOC - Air Operator's Certificate, issued by the CAA and required by aircraft operators flying scheduled or charter public transport flights, including cargo, air-taxi and pleasure-flying work. Also Air Officer Commanding in RAF parlance.
AoE - airport of entry (usually in USA).
AOG - aircraft on ground, a term used to denote urgency when requesting spares or service from suppliers or manufacturers, meaning that the aircraft cannot fly again until the parts have been supplied.
AOM - Aircraft Operating Manual
AOPA - Aircraft Owners and Pilots Association.
A/P - Airport or Autopilot.
A & P - Airframe and Powerplant Mechanic (USA).
APA - Aerodromes Protection Agency, the federation of associations for the advancement of British general aviation facilities.
APHAZ - Aircraft Proximity Hazards Assessment Panel, which investigates near-miss reports filed by air traffic controllers (see also JAWG).
APP - Approach (control).
APU - Auxiliary Power Unit. Large transport aircraft and some business jets have an APU, typically a small turbine, to provide power for engine-starting and for running systems when on the ground, obviating the need for external power or ground power unit, GPU.
ARB - Airworthiness Review Board.
ARCAL - Aircraft Radio Control of Airport lighting.
Aresti - Key shorthand notation system devised by Spaniard José L Aresti whereby aerobatic display routines or competition sequences can be drawn up on paper like a musical score. Now largely superseded by the simpler FAI Aerobatic Catalogue system.
ARINC - Aeronautical Radio Incorporated. A non-profit corporation owned by airlines to set standards for airline avionics and provide communications services.
ARP - Airport reference point.
ARR - Arrival
ASDA - Accelerate-Stop Distance Available.
ASI - Airspeed Indicator, a flight instrument which measures the speed of an aircraft through the air.
ASR - altimeter setting region, a geographical area for which the lowest value of QNH (which see) is forecast hourly and relayed by air traffic control centers. Also airport surveillance radar and air-sea rescue.
A/T - Autothrottle
ATA - Air Transport Association
ATA - Actual Time of Arrival.
ATC - Air Traffic Control.
ATCO - air traffic control officer. Also ATCA, air traffic control assistant; ATCC, air traffic control center; SATCO, senior air traffic control officer.
ATHR - Autothrust System
ATIS - automatic terminal information service, a continuous recorded broadcast of routine non-control airport information, usually at large airports.
ATPL - Air Transport Pilot's Licence, needed to act as pilot-in- command of a commercial air transport aircraft exceeding 20,000 kg all-up weight.
ATS - Air Traffic Service. Also ATSU, ATS Unit.
ATS - Automatic Throttle System
ATSORA - air traffic services outside regulated airspace.
ATZ - Airport Traffic Zone. An area of protected airspace surrounding an Airport bounded by a circle of 2 nm or 2.5 nm radius (depending on runway length) centered on the mid-point of the longest runway. Permission is required for entry into and movement in an ATZ.
AUW - All-Up Weight, a term for the total loaded weight of an aircraft.
avgas - Aviation Gasoline, usually followed by the octane rating. Used by piston-engined aircraft. Also LL, low lead.
avtur - Aviation Turbine Fuel (kerosene). Used by turboprops and jets.
AWACS - Airborne Warning And Control System
AWY - airway.
BAA - British Airports Authority.
BAeA - British Aerobatic Association.
BALPA - British Airline Pilots Association.
BAUA - Business Aircraft Users Association.
BCAR - British Civil Air Requirements. Airworthiness standards laid down by the CAA for certification of aircraft on the UK Civil Aircraft Register.
BCP - Break Cloud Procedure.
BCPL - Basic Commercial Pilot's Licence, the minimum qualification necessary in the UK to receive payment for acting as a pilot. Also CPL, Commercial Pilot's Licence, and SCPL, Senior Commercial Pilot's Licence (no longer issued).
Beta Mode - Manually-controlled mode for CS propellers on turboprop aircraft enabling reverse pitch to be selected for braking or to aid ground manoeuvring.
BF - MarkAir
BFR - Biennial Flight Review (USA). Holders of U.S. FAA Private Pilot Licences must undergo a flight check with an FAA-approved examiner every two years. No UK equivalent.
BGA - British Gliding Association.
BHAB - British Helicopter Advisory Board
BHPA - British Hang-Gliding and Paragliding Association.
BMAA - British Microlight Aircraft Association.
Bottlang - Loose-leaf Euopean airfields manual for VFR operations.
BRG - Bearing, the horizontal direction to or from any point expressed in degrees of the compass.
BWPA - British Women Pilots Association.
C - Celsius (temperature) or compass.
CAA - Civil Aviation Authority. ( UK )
CAD/CAM - computer-aided design/manufacture.
CAAFU - Civil Aviation Authority Flying Unit, based at Stansted Airport, which performs such tasks as navaid checking and calibration and also examines candidates for instrument ratings and commercial pilot's licences.
CANP - Civil Aviation Notification Procedure. A voluntary system whereby civil operators notify their intention to fly at low level (at or below 1,000 feet agl, when crop-spraying or powerline inspecting for example), aimed at avoiding conflict with low-flying military aircraft.
CAP - Civil Air Publication. Information booklets issued by the CAA, e.g. CAP 53 The Private Pilot Licence.
CAPT - Captain.
CAS - Calibrated Airspeed -- indicated airspeed corrected for air density and compressibility.
CAT - Clear-Air Turbulence. Also CATegory when referring to certain instrument landing systems which require special aircraft instrumentation, certification and pilot qualification beyond those needed for standard instrument approaches.
CAVOK - pronounced CAV-okay (ceiling and visibility OK), visibility at least ten kilometres, with no cloud below 5,000 feet, with no Cbs, precipitation, thunderstorms, shallow fog or low drifting snow.
CAVU - Ceiling and visibility unlimited. Cloudless (or scattered cloud) conditions with visibility in excess of ten kilometres.
CDI - Course Deviation Indicator. The vertical needle of a VOR indicator which shows the aircraft's position relative to the selected VOR radial.
CDU - Control Display Unit.
Ceiling - Height above ground or water of the base of the lowest layer of cloud below 20,000 feet which covers more than half of the sky.
CFI - Chief Flying Instructor (certified flying instructor in USA).
CH - Compass Heading.
CHIRP - Confidential Human Factors Incident Reporting system, whereby professional pilots and ATC staff may report in confidence incidents arising from human errors for analysis by the RAF Institute of Aviation Medicine at Farnborough.
CHT - Cylinder Head Temperature (gauge). A device which, by means of a probe(s) gives a cockpit readout of the temperature of one or more of an aircraft engine's cylinder heads.
CI - China Airlines
Circuit - Pattern around which aircraft fly when arriving at an airfield. See also finals, below.
C/L - Center-line (of a runway, for example).
Clearance - Authorization from air traffic control to proceed as requested or instructed. Used for ground and air manoeuvring, thus "cleared for take-off", "cleared flight-planned route", "cleared to descend" etc.
Clouds - commonly-used abbrevitaions for cloud types :-
CO - Continetnal
C of A - Certificate of Airworthiness issued by the CAA indicating that an aircraft meets the Authority's airworthiness standards. Cs of A are issued to individual aircraft, and also to generic aircraft types (Type Certification in the USA) when the first example of a type is registered. Cs of A on individual aircraft are granted in several categories, e.g. Private, Public Transport, Aerial Work etc. and much be renewed at intervals. Permits to Fly are authorisations granted to aircraft such as homebuilts, vintage aeroplanes, warbirds and some simple classic light aircraft which are not required to meet the standards demanded for a full C of A, and are accordingly restricted in the kinds of operation for which they may be used.
C of E - Certificate of Experience, valid for private pilot licence holders for thirteen months, and renewed by flight test or evidence of completing the minimum required flying experience in the preceding thirteen-month period. Also C of T, certificate of test.
c of g - Center of gravity. The point on an aircraft through which the entire aircraft's weight may be assumed to act (i.e. around which the aircraft, if suspended, would balance). C of G limits are the most forward and rearward positions of the C of G permitted for safe operation. An aircraft loaded outside its C of G limits can be difficult or impossible to control.
COM(M) - communication(s)
C of P - Center of pressure, the point through which the total effect of lift may be said to act on an aeroplane.
CPL - Commercial Pilot's Licence
CPU - Central Processing Unit
CR or C/R - counter-rotating. Usually in general aviation referring to twin-engined aircraft with `handed' engines whose propellers turn in opposite directions to eliminate propeller torque effect.
CRP - compulsory reporting point.
CRS - Course
CRT - Cathode ray (television) tube. Used in flight deck displays of new-generation airliners, business aircraft and military jets instead of conventional instruments. See also EFIS, below.
Critical Altitude - The highest density altitude at which it is possible to maintain the maximum continuous rated power or manifold pressure of an aero engine.
Critical Engine - The engine on a multi-engined aircraft whose failure would most seriously effect performance or handling of the aircraft, through asymmetric effects or loss of power to systems such as hydraulics.
CRS Course - The intended direction of flight in the horizontal plane expressed in degrees of the compass.
CRZ - Cruise
c/s - call sign.
CS - constant-speed (propeller). A variable-pitch propeller which maintains constant rpm by automatically changing blade angle. Also CSU, constant-speed unit.
CTA - Control Area. An area of controlled airspace extending upwards from specified limit agl.
CTR - Control Zone. An area of controlled airspace extending upwards from ground level to a specified upper limit.
CVR - cockpit voice recorder. A tape recorder installed on the flight decks of commercial transport aircraft and helicopters and some business aeroplanes to record crew conversation, RT transmissions and cockpit background noises (e.g. trim-wheel operation, flap motor running) in case required for incident or accident investigation.
CW - carrier wave or continuous wave.
CZ - Control Zone (USA).
DA - Danger Area. Also DACS, Danger Area Crossing Service, and
EAA - Experimental Aircraft Association, the American homebuilders' organisation.
EADI - Electronic Attitude Director Indicator. An ADI with CRT cockpit display forming part of an EFIS, below.
EAT - Estimated Approach Time.
EBAA - European Business Aircraft Association.
ECAC - European Civil Aviation Conference.
ECOGAS - European Council of General Aviation Support.
ECU - Environmental Control Unit.
EET - Estimated Elapsed Time.
EFAS - Electronic Flash Approach light System.
EFATO - Engine Failure At (or after) Take-Off.
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'. Now common in commercial transports, corporate aircraft and helicopters, military fighters and some GA piston singles and twins.
EGT - Exhaust Gas Temperature (gauge). A device which provides a cockpit readout of the exhaust gas temperature of an aircraft's (piston) engine(s), enabling the pilot to lean the mixture for maximum fuel efficiency.
EHSI - Electronic Horizontal Situation Indicator. CRT-based HSI forming part of an EFIS.
EICAS - Engine Indicating and Crew Alerting System. CRT display which monitors engine performance and alerts the crew to system or airframe failure. Found in new-generation transports and business jets.
ELT - Emergency Locator Transmitter. A small radio transmitter fixed to an aircraft's structure which is automatically activated by impact or water immersion and transmits a code on emergency frequencies enabling SAR satellites or search units equipped with DF to locate the crash or ditching site. Carriage mandatory in the USA, but not in UK. Sometimes styled ADELT, automatically deployable ELT, or ELB, emergency locator beacon.
Empty Weight - Weight of the basic aeroplane including all fixed equipment, plus unusable fuel, oil, hydraulic and other fluids.
Encoding Altimeter - An altimeter which gives a digital output to the transponder (which see) for automatic transmission of the aircraft's pressure altitude to ATC.
ENG - Engine
EOBT - Estimated Off-Blocks Time.
EPNdB - Effective perceived noise decibel. Unit of measurement of aircraft noise levels.
ETA - Estimated Time of Arrival. Also ETD, estimated time of departure; ETE, estimated time en route.
EROPS - extended range operations, usually long over-water flights by twin-jet airliners.
ETPS - Empire Test Pilots School, based at the Aircraft & Armament Experimental Establishment, Boscombe Down.
Eurocontrol - organisation, headquartered in The Netherlands, comprising Belgium, France, Germany, Ireland, Luxembourg, Netherlands and UK for coordinating enroute air traffic control in Europe.
FAA - Federal Aviation Administration, ( US )
FADEC - Full-Authority Digital Engine Control.
FAF - Final Approach Fix, the point at which a published instrument approach begins.
FAI - Fédération Aéronautique Internationale, the international body for verification of aeronautical record attempts and sporting regulations.
FAR - Federal Aviation Regulations ( US )
FARA - Formula Air Racing Association.
FBO - Fixed-Base Operator, American term for commercial operators supplying fuel, maintenance, aircraft sales, rental, flight training, handling and other general aviation services at an airport. (So-called because the the first FBOs were early barnstormers who chose to settle at one field.)
FBW - Fly-By-Wire. Aircraft control systems in which pilots' control inputs are transmitted to control surfaces electronically or via fibre optics rather than by mechanical linkage.
FDR - Flight Data Recorder, Better known as the `black box' (actually painted bright orange), by which various parameters of an aircraft's flight performance are recorded for analysis in the event of an incident or accident.
Feather (of a propeller) - To set the angle of CS or VP propeller edge-on to the airflow to minimise drag and rotation following engine failure on multi-engined aircraft. Also applies to motor gliders which have feathering propellers to enhance engine-off soaring performance.
FF - Fuel Flow
Final(s) - Final Approach. 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. Downwind is the segment of the circuit paralleling the runway and flown on a reciprocal heading. Base leg is the crosswind segment bringing the aircraft from the downwind leg to final approach. The leg before downwind is called the Crosswind leg.
FIC - Flight Information Center.
FIR - Flight Information Region. UK airspace is divided into two FIRs, London and Scottish.
FIS - Flight Information Service, providing a variety of services and information (but not control) to air traffic in the two FIRs above.
Fix - Position in space usually on aircraft's flight plan
FJ - fast jet.
FL - flight level, a level of constant atmospheric pressure shown by an altimeter set to a standard 1013.2 millibars, expressed in rounds hundreds of feet, thus FL330 is 33,000 feet.
Flag - Warning signal incorporated in certain navigation and flight instruments indicating that the instrument is not operating satisfactorily or that the strength of signals being received from ground stations is below acceptable limits.
Flat Rating - throttling or other restriction of engine power ouput (usually in turboprops and turboshafts) at sea level to enable it to give constant predictable power at higher operating altitudes.
Flameout - combustion failure in a turbine engine resulting in power loss.
FLCH - Flight Level Change.
Flicker Effect - nausea, dizziness or vertigo which can be brought on by flickering at certain frequencies of a bright light source such as sunlight or strobe when viewed through a rotating propeller or rotor blades.
FLIR - Forward Looking Infrared.
FLT - Flight
FMC - Flight Management Computer
FMCS - Flight Management Computer System.
FMS - Flight Management System.
FO - First Officer , also F/O
FOB - Fuel on Board.
FOD - Foreign Object Damage, usually to turbine engines through ingestion of runway debris etc.
FPA - Flight Path Angle
FPF - Flight Plan Forecast.
FPM - Feet Per Minute, a measure of an aircraft's rate of climb or descent. Similarly m/s or mps, metres per second.
FPT - Flight Plan Time.
FREQ - Frequency
FSS - Flight Service Station ( US ).
g - the acceleration force of gravity, normally 1g on earth. Zero g (0g) is weightlessness, as experienced by orbiting astronauts. g is expressed as positive (+) and negative (-) values, During a normal loop a pilot experiences positive g, tending to force him down in his seat. In an outside loop, with the pilot's head on the outside of the vertical circle, negative g forces him up against his straps. Aircraft structural load limits are expressed in positive and negative values, the positive limit usually greater than negative, except in specialist aerobatic types.
g-loc - g-induced loss of consciousness. Pilot blackouts caused by excessive g or by too-rapid onset of g-forces. Experienced mostly by pilots of high-performance military jets and competition aerobatic aircraft, has led to fatal crashes.
GA - General Aviation, all flying other than airlines and the military.
GAAC - General Aviation Awareness Campaign.
GAFOR - General Aviation Visual Flight Forecast. Met briefing service
in operation in France, Germany, the Netherlands and some other European countries.
GAMA - General Aviation Manufacturers Association, an American trade organisation.
GAMTA - General Aviation Manufacturers & Traders Association, ( UK )
GAPAN - Guild of Air Pilots and Air Navigators.
GASIL - General Aviation Safety Information Leaflet. Monthly safety and accident prevention bulletin for pilots and engineers published by the CAA.
GCA - Ground-Controlled Approach. A landing approach in which a ground controller gives verbal guidance in azimuth and elevation to a pilot using precision approach radar (PAR) to monitor the aircraft's approach path. Still used by the military, but defunct in civil aviation.
GFT - General Flying Test, taken by student pilots to qualify for the PPL, and also by candidates for the BCPL and CPL. Also NFT, navigation flight test, which is part of the practical examination for the PPL.
GHz - Gigahertz
Glonass - Russian equivalent of GPS/Navstar satellite navigation system.
GMT - Greenwich MeanTime
GND - Ground
GNSS - Global Navigation Satellite Systems. Go-around to climb away from a runway after making an approach, either to make a further attempt at landing or to divert to an alternate airport (formerly `overshoot').
GOSSU - Global Positioning System Sensor Unit
Goxio - VHF direction-finding (France)
GP - Glidepath
GPH - Gallons Per Hour, an expression of fuel consumption or fuel flow (FF) in either imperial or U.S. gallons. Usually lb/hr for turbine-powered aircraft.
GPS - Global Positioning System (Navstar). A U.S. developed satellite-based high-precision navigation system, intended primarily for military use but now in widespread use by commercial and private operators, though with reduced accuracy compared with military versions.
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.
GRADU - Gradual (term used in Met reports).
GRP - Glassfibre-Reinforced Plastic. Composite materials seeing increasing use in entire airframes for GA aircraft (e.g. Beech Starship) and for components for helicopters, airliners and military aircraft.
GS - Glideslope. The vertical guidance part of an instrument landing system which establishes a safe glidepath (usually three degrees) to a runway.
G/S - Groundspeed. The speed an aircraft makes over the ground, a product of its airspeed and wind speed.
H24 - Continuous round-the-clock operation. Also HJ operates during day; HN operates during night; HO operates during times to meet operational requirements, and HX no specific operational hours.
HAA - Historic Aircraft Association.
HAI - Helicopter Association International.
Half-Mill(ion) - 1:500,000 scale ICAO aeronautical chart.
HDG - Heading. The direction in which an aircraft's nose points in flight in the horizontal plane, expressed in compass degrees.
Heavy - Suffix used in RT callsigns to indicate that the aircraft is a large transport, alerting controllers and following aircraft to the possibility of wake turbulence.
Hectopascal (hPa) - unit of pressure measurement, equivalent to one millibar (which see), now the ICAO-standard for altimeter setting.
HEMS - Helicopter emergency medical services.
Hertz - Standard radio equivalent of frequency in cycles per second. See also kHz and MHz.
HF - High-Frequency band, used for long-range radio communications in the 3-30 MHz range.
Hg - Inches Of Mercury, a unit of pressure measurement.
HIAL - High Intensity Approach Lighting.
HIRF - High Intensity Radiated (electromagnetic) Fields.
HIRL - High Intensity Runway Lighting.
HISL - High Intensity Strobe Light.
Holding Pattern - Racetrack-shaped manoeuvre which keeps aircraft within a specified airspace while awaiting further clearance from air traffic control.
hot-and-high - Airfield conditions of high altitude and high ambient temperatures that can severely limit aircraft performance. See also density altitude.
HOTAS - Hands on throttle and stick. Ergonomic cockpit design technology, originally developed for military combat aircraft, enabling a pilot to fly the aircraft and manage all navigation, weapons and other systems from control column/throttle lever hand grips.
HP - Holding Pattern
HPA - Hectopascals
HRA - Highlands Restricted Area
HSI - Horizontal Situation Indicator. A cockpit navigation display, usually part of a flight-director system, which combines navigation and heading.
HUD - Head-Up Display. A method of projecting instrument readouts or data which enables a pilot to see them while looking through the aircraft's windscreen. Mostly used on military aircraft, but now in service on some commercial airliners.
IAS - Indicated Airspeed. An aircraft's speed through the air as indicated by the ASI, without correction for position error, altitude or outside air temperature.
IATA - International Air Transport Association.
I/C - Intercom
ICAO - International Civil Aviation Organisation.
IDG - Integrated Drive Generators.
IF - Instrument Flying.
IFF - Identification Friend or Foe.
IFR - Instrument Flight Rules prescribed for the operation of aircraft in instrument meteorological conditions. Flight in most controlled airspace in the UK is conducted under IFR or Special VFR. Also used by military to denote in-flight refuelling.
IGE - In Ground Effect. Helicopter performance with an earth surface immediately below. Also OGE, out of ground effect. Helicopters can hover at a greater maximum altitude IGE (above a mountain slope, for example) than they can in free air, OGE.
IGS - Instrument Guidance System.
ILS - Instrument Landing System. The approach aid employing two radio beams to provide pilots with vertical and horizontal guidance during the landing approach. The localiser provides azimuth guidance, while the glide-slope defines the correct vertical descent profile. Marker beacons and high intensity runways lights are also part of the ILS.
IMC - Instrument Meteorological Conditions: weather below VMC minima, see below. Also associated rating used in conjunction with UK PPL.
INCERFA - Uncertainty phase of search-and-rescue procedure.
INMARSAT - International Maritime Satellite.
INS - Inertial Navigation System. A gyroscope-based system which senses acceleration and deceleration and computes an aircraft's position in latitude and longitude with great accuracy. Used mostly by long-haul airliners, military aircraft and sophisticated business jets. Also IRS, inertial reference system.
INTER - Intermittent or fluctuating, term used in Met reports.
IR - Instrument Rating.
ISA - International Standard Atmosphere -- a set of standard conditions or temperature and pressure which serve as a basis for comparison. ISA = pressure 1013.2 millibars, temperature 15øC. Aircraft performance figures quoted by manufacturers are often based on such a `standard day'.
ITT - Inter-Turbine Temperature.
JAA - Joint Aviation Authority.
JAR - Joint Aviation Requirements, being drawn up by eighteen European states, aimed at unifying airworthiness, flight crew licensing and other criteria among signatory nations.
JAWG - Joint Airmiss Working Group. A civilian/military committee which reviews and reports on all airmisses which occur in UK airspace.
Jeppesen - U.S.-developed navigational/approach chart system with worldwide coverage, similar to British Aerad system.
JPATS - Joint Primary Aircraft Training System. A USAF/U.S. Navy programme to select a common aircraft design as a basic pilot trainer for the two services, due to be decided next year.
kHz - Kilohertz, the frequency of a radio carrier wave measured in thousands of cycles per second. 1 kHz = 1,000 Hertz.
KLM - Royal Dutch Airlines
Knot (kt) - One nautical mile per hour (never one knot per hour), the standard unit of aviation speed measurement. One knot equals 1.1515 mph; one nautical mile equals 6,080 feet.
kw - Kilowatt.
LARS - Lower Airspace Radar Advisory service, available to all aircraft flying in uncontrolled UK airspace from 3,000 feet amsl to FL95. See also MMARS, RAS and RIS, below.
LAMS - Light Aircraft Maintenance Schedule, the CAA-approved schedule for fixed-wing light aircraft below 2,730 kg auw whose Cs of A are valid for three years subject to compliance with LAMS.
LAT - Latitude.
LDA - Landing Distance Available.
LDG - Landing
LF - Low-Frequency radio waves with frequencies in the 30-300 kHz band.
LITAS - Low-Intensity Two-colour Approach System.
LLTV - Low Light Level Television.
LLZ - Localizer ( US )
LNAV - Lateral Navigation.
LOC - Localiser. The azimuth guidance portion of an instrument landing system.
Locator - Medium-frequency non-directional radio beacon used as an aid to establishing yourself on final approach during an instrument landing procedure. Also LOM, locator outer marker.
LON(g) - Longitude
Loran - Low-frequency hyperbolic radio long-range navigation system which measures time difference between reception of synchronised signals transmitted from ground transmitters. Loran-C, operates in the 100-110 kHz frequency band with an operating range of 600-1,500 nm independent of line-of-sight, and is becoming very popular among GA aircraft operators in the USA.
MAG - Magnetic
Mach number - Ratio of true airspeed to the speed of sound. Mach 1 is the speed of sound at sea level, ISA, approximately 1,100 feet per second or 760 mph.
MAP - Missed Approach Point. The point on a published ILS approach expressed in time or distance from the final approach fix, or as an altitude on the glideslope, at which the missed approach procedure must be initiated if the runway or approach lights are not clearly in sight.
Marker Beacons (mkrs) - Part of an instrument landing system using 75 MHz transmitters emitting fan-shaped or elliptical signal patterns vertically upwards, defining specific points along the glideslope. The outer marker OM is situated at or near the glideslope intercept altitude of the ILS localiser, the middle marker (MM) defines a point on the glideslope at or near decision height (DH). Markers provide aural and visual indications on a cockpit marker beacon receiver.
MATZ - Military Airport Traffic Zone. An area of protected airspace surrounding certain military airfields which normally extends for a five nautical mile radius around the airfield and upwards from the surface to 3,000 feet above Airport level. A 'stub' projection protects the final approach path to the main runway outwards from the MATZ boundary, enclosing an area two nautical miles either side of the extended runway Centerline and upwards from 1,000 feet above the surface to 3,000 feet above Airport elevation. Although recognition of a MATZ is not mandatory for civil aircraft, all MATZ Airports offer a penetration service to civil traffic during operational hours.
Mayday - International radio distress call (from the French, m'aidez -- help me). It signifies imminent danger to life requiring immediate assistance.
mb - Millibar.
MCDU - Multifunction Control Display Unit
MCP - Mode Control Panel
MDA - Minimum Descent Altitude. The lowest altitude, in feet amsl, to which descent is authorised on final approach during a non-precision instrument landing (i.e. where no glideslope guidance is given) without visual reference to the runway.
MDH - Minimum Descent Height, agl.
MEDA - Military Emergency Diversion Airfield.
MET - Meteorology, weather.
METAR - Coded Airport Met report.
MF - Medium Frequency. Radio waves with frequencies in the 300- 3,000 kHz range.
MFA - Military Flying Area
MFD - Multi-Function Display. An EFIS CRT offering selectable displays of weather radar, navigation maps, checklists and data other than primary flight information.
MH - Magnetic Heading
MHz - Megahertz, the frequency of radio carrier waves measured in millions of cycles per second.
Minimums - Weather condition requirements for a particular mode of flight (e.g. for VFR operation, IFR take-offs and landings).
MLS - Microwave Landing System. A microwave-based instrument approach system intended to replace ILS in the 1990s and claimed to offer a number of advantages such as the ability to fly segmented and curved precision approaches.
MMARS - Military Middle Airspace Radar Service, available to military and civil aircraft operating in UK airspace between FL100 and FL245.
MOA - Military Operations Area.
mogas - Car fuel, approved for use in some light aircraft subject to certain conditions.
MPA - Man-Powered Aircraft
MSA - Minimum sector altitude or minimum safe altitude.
MSL - Mean Sea Level
MTBF - Mean Time Between Failures.
MTMA - Military Terminal Control Area.
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