FBO - fixed-base operator, American term for commercial operators supplying fuel, maintenance, aircraft sales, rental, flight training, handling and other GA services at an airport. (So-called because 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. Also see FBL.

FCL - Flight Crew Licensing (Division), a CAA department handling all aspects of private and professional pilot, flight engineer and navigator licensing.

FCS - flight control system.

fcst - forecast.

FDR - flight data recorder, popularly known as a '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.

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 Centre.

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.

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.

FLG - flashing.

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 infra-red.

FLM - foot-launched microlight.

FLPA - foot-launched powered aircraft, e.g. powered parachutes.

FM - frequency modulation.

FMC/S - flight management computer/system

FMGC - flight management guidance computer.

FMS - flight management system.

FMU - flight management unit.

FOD - foreign object damage, usually to turbine engines through ingestion of runway debris etc.

FPL - filed flight plan.

fpm - feet per minute, a measure of an aircraft's rate of climb or descent. Similarly m/s or mps, metres per second.

FSS - Flight Service Station (USA).

FTO - flying training organisation.

FTS - Flying Training School (RAF)

ft/min - feet per minute

G
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. [page]

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.

gall imp/U.S. - gallons, imperial or USA. One imp gall = 1.201 U.S. gall.

GAMA - General Aviation Manufacturers Association, an American trade organisation.

GAMTA - General Aviation Manufacturers & Traders Association, UK.

GAPAN - Guild of Air Pilots and Air Navigators.

GASCo - General Aviation Safety Council

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.

Glonass - Russian equivalent of GPS/Navstar satellite navigation system.

glove - non-movable part of a variable geometry wing.

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').

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; also CFRP, carbon-fibre 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.

H
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.

HIGE - hover in ground effect. Also see HOGE.

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.

HOCAC - hands on cyclic and collective - see HOTAS below.

HOGE - hover out of ground effect. Also see HIGE.

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.

HOTCC - hands on throttle, collective & cyclic - see HOTAS above. [page]

hp - horsepower.

HRA - Highlands Restricted Area

hrs - hours

HSD - horizontal situation display.

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.

Hz - Hertz.

I
IAOPA - International Council of Aircraft Owners and Pilots Associations

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. Also see CAS, RAS and TAS.

IATA - International Air Transport Association.

i/c - intercom

ICAO - International Civil Aviation Organisation.

IF - instrument flying. Also intermediate frequency.

IFF - identification friend or foe.

IFR - instrument flight rules prescribed for the operation of aircraft in instrument meteorological conditions (see below). 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.

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

IRAN - Inspect and repair as necessary

IRE - Instrument Rating Examiner

IRT - Instrument Rating Test

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 15 degrees C. Aircraft performance figures quoted by manufacturers are often based on such a 'standard day'.

ITT - inter-turbine temperature. Also TGT, turbine gas temperature TIT, turbine inlet temperature.

IWR - Instrument weather rating. Proposed by the JAA as a replacement for the UK's unique IMC rating

J
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.

JEFTS - Joint Elementary Flying Training Squadron based at RAF Barkston Heath, Lincolnshire

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.

K
kg - kilogram(s)

kHz - kilohertz, the frequency of a radio carrier wave measured in thousands of cycles per second. 1 kHz = 1,000 Hertz.

KIAS - knots indicated airspeed.

km - kilomrtre(s)

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.

kV- kilovolt

kW - kilowatt.

L
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.

LATCC - London Area & Terminal Control Centre at West Drayton, near Heathrow.

lb - pound(s)

lbf - engine thrust in pounds force

LCD - liquid crystal display

lczt - (ILS) localizer (USA) [page]

l/d ratio - lift /drag ratio, a measurement of the efficiency of a wing aerofoil section

LDA - landing distance available.

LED - light emitting diode

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 ((USA).

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..

LOFT - Line-orientated flying training. Usually on large jet simulators to prepare newly-qualified commercial pilots for multi-crew airline operations

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.