Glossary — Complete List of Terms

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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

A

A-W AgustaWestland

AAM Air-to-air missile.

AAAW Advanced Anti-Armour Weapon (became Brimstone).

AAR Air-to-air refuelling.

AB Air Base.

AB Aktiebolag (Swedish company constitution).

ABCCC Airborne Battlefield Command and Control Centre.

absolute ceiling Greatest altitude attainable by aircraft in level flight.

AC Alternating current.

ACC Air Combat Command (US).

ACLS Automatic carrier landing system.

ACM Advanced Cruise Missile (US designation means AGM-129).

ACMI Air combat manoeuvring instrumentation.

ACN Aircraft classification number.

ADC Air data computer.

ADV Air Defence Variant (of Tornado), RAF designations = Tornado F2/2A or F/3.

ADF Medium-frequency Automatic Direction-Finding (equipment).

ADI Attitude/director indicator.

aerofoil Any solid body so shaped that, as a fluid medium (air or hot gas) moves past it, it experiences a useful force perpendicular to the direction of relative motion; thus, a wing generates lift, while a turbine blade generates torque on a shaft.

aeroplane (North America, airplane) Heavier-than-air aircraft with propulsion and a wing that does not rotate in order to generate lift.

AEW Airborne early warning.

AEW&C Airborne Early Warning and Control.

AFB Air Force Base (USAF).

AFCS Automatic flight control system.

AFRC Air Force Reserve Command (US).

AFRES Air Force REServe.

AFRP Aramid fibre-reinforced plastics.

AFSOC Air Force Special Operations Command.

afterburning Temporarily augmenting the thrust of a turbofan or turbojet by burning additional fuel in the jetpipe.

AGM Air-to-ground missile.

Ah Ampere-hours.

AH Army Helicopter (UK designator).

AHIP Army Helicopter Improvement Programme (for US Army OH-58 Kiowa).

AHRS Attitude/heading reference system.

airbrake Passive device extended from aircraft to increase drag. The most common form is hinged flap(s) or plate(s), mounted in locations where operation causes no significant deterioration in stability and control at any attainable airspeed. Airbrakes are also mounted on the spine of an aircraft as on the F-15 and Su-27.

AIDC Aerospace Industrial Development Corporation (Taiwan).

AIM Air Interception Missile (used in US designations, such as AIM-9).

aircraft All manmade vehicles for off-surface navigation within the atmosphere, including helicopters and balloons. Air-cushion vehicles and wing-in-ground-effect vehicles are excluded from the classification.

airship Power-driven lighter-than-air aircraft. Traditional classes are: blimp, a small non-rigid; non-rigid, in which envelope is essentially devoid of rigid members and maintains shape by inflation pressure; semi-rigid, non-rigid with strong axial keel acting as beam to support load: and rigid, in which envelope is itself stiff in local bending or supported within or around rigid framework.

airstair Retractable stairway built into aircraft. Often incorporated into the door.

aka also known as.

ALARM Air-launched anti-radiation missile.

ALAT Aviation Legere de l’Armee de Terre. (French army aviation).

ALCM Air-launched cruise missile.

ALH Advanced Light Helicopter (HAL Druhvs).

Allithium Aluminium-lithium alloy.

ALLTV All-light level television.

AM Amplitude modulation.

AMC Air Mobility Command (US).

AMRAAM Advanced Medium-Range AAM.

An Antonov (Russian design bureau).

ANG Air National Guard (US).

anhedral Downward slope of wing or tailplane from root to tip.

anti-balance tab Hinged surface on trailing-edge of stabilator and operating in same direction, so as to dampen its movement.

ANVIS Aviator's night vision system.

AO Aktsionernoye Obshchestvo (Co Ltd; Russian company constitution).

AoA Angle of attack (see ‘attack’ below).

AOOT Aktsionernoye Obshchestvo Oktrytogo Tipa (Russian company constitution).

APACHE Armement Propulsee A Charges Ejectables – French weapons dispenser weapon from which StormShadow/SCALP EG weapons are derived.

APN Aviation of the People’s Navy (China’s naval air arm).

approach noise Measured 1 nautical mile from downwind end of runway with aircraft passing overhead at 113 m (370 ft).

APR Auxiliary power reserve.

APU Auxiliary power unit (part of aircraft).

ARINC Aeronautical Radio Inc, US company whose electronic box sizes (racking sizes) are the international standard.

ARM Anti-radiation missile.

ArNG Army National Guard (US).

AS&C Airborne Surveillance & Control (UK designator).

ASARS Advanced Synthetic Aperture Radar System.

ASE (1) Automatic stabilisation equipment; (2) Aircraft survivability equipment.

AshM Anti-ship Missile.

ASI Airspeed indicator.

ASM Air-to-surface missile.

ASMP Air-Sol-Moyenne Portee – French nuclear stand-off missile.

aspect ratio Measure of wing (or other aerofoil) slenderness seen in plan view, usually defined as the square of the span divided by gross area.

AST Air Staff Target (UK).

ASTOVL Advanced STOVL.

ASUW Anti-surface unit warfare.

ASRAAM Advanced Short-Range Air-to-Air Missile.

ASV/AsuV Anti-surface vessel.

ASVW Anti-Surface Vessel Warfare.

ASW Anti-submarine warfare.

ATC Air traffic control.

ATGM Anti-Tank Guided Missile.

ATGW Anti-Tank Guided Weapon

ATM Anti-Tank Missile.

ATR Airline Transport Radio ARINC 404 black box racking standards.

attack, angle of (alpha) Angle at which airstream meets aerofoil (angle between mean chord and free-stream direction). Not to be confused with angle of incidence (which see).

augmented Boosted by afterburning (turbofan), as in augmented turbofan.

autogyro Rotary-wing aircraft propelled by a propeller (or other thrusting device) and lifted by a freely running autorotating rotor.

AUW All-up weight (term meaning total weight of aircraft under defined conditions, or at a specific time during flight). Not to be confused with MTOW (which see).

avionics Aviation electronics.

AVLF Airborne Very Low Frequency – communications system used to communicate with submersed USN submarines.

AWACS Airborne warning and control system (aircraft category). The USAF programme which spawned the E-3 Sentry and often incorrectly used as the aircraft name itself.

axisymmetric intakes Twin, circular engine air intakes mounted astride the spinner of New Piper light aircraft.

axisymmetric nozzle Circular jet-engine nozzle capable of unrestricted vectoring movement (within a cone specified by mechanical limitation) to enhance aircraft manoeuvrability.

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B

B Bomber (US designation prefix).

BAC British Aircraft Corporation.

BAe British Aerospace.

ballistic parachute Emergency recovery parachute installed in (generally light) aircraft and capable of supporting both machine and occupants.

band See radar frequency.

bar Non-SI unit of pressure adopted by this yearbook pending wider acceptance of Pa. 1 bar = 10⁵ Pa. ISA pressure at S/L is 1013.2 mb or just over 1 bar. ICAO has standardised hectopascal for atmospheric pressure, in which ISA S/L pressure is 101.32 hPa.

basic operating weight MTOW minus payload (thus, including crew, fuel and oil, bar stocks, cutlery and so on).

BBMF Battle of Britain Memorial Flight.

Be Beriev (Russian design bureau).

bearingless rotor Rotor in which flapping, lead/lag and pitch change movements are provided by the flexibility of the structural material and not by bearings. No rotor is truly rigid.

BERP British Experimental Rotorcraft Programme.

BITE Built-in test equipment.

bladder tank Fuel (or other fluid) tank of flexible material.

BLC Boundary-layer control.

bleed air Hot high-pressure air extracted from gas turbine engine compressor or combustor and taken through valves and pipes to perform useful work such as pressurisation, driving machinery or anti-icing by heating surfaces.

blown flap Flap across which bleed air is discharged at high (often supersonic) speed to prevent flow breakaway.

BOW Basic operating weight (which see).

BPR Bypass ratio.

BTU Non-SI energy unit (British Thermal Unit) = 0.9478 J.

bulk cargo All cargo not packed in containers or on pallets.

bus Busbar, main terminal in electrical system to which battery or generator power is supplied.

BV Besloten Vennootschap (Netherlands company constitution).

BVR Beyond visual range.

BWB Blended wing/body.

bypass ratio Air flow through fan duct (not passing through core) divided by airflow through core.

byte Group of bits of information forming unit in computer processing.

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C

C Cargo (transport) – UK designator and US prefix.

C²W Command and Control Warfare.

C³ Command, control and communications.

C³I Command, Control, Communications, Intelligence.

CAA Civil Aviation Authority (UK).

cabane Structure, usually of braced struts, to support load above fuselage or wing. May carry parasol wing, engine nacelle or upper wing of most biplanes.

cabin altitude Height above S/L at which ambient pressure is same as inside cabin.

CAC Chengdu Aircraft Industrial Corporation (China).

CAD/CAM Computer-assisted design/computer-assisted manufacture.

CAF Canadian Armed Forces.

CAG Commander, Carrier Air Wing.

CAHI Central Aero and Hydrodynamics Institute of the Russian Federation; also transliterated as TsAGI.

CALCM Conventional (-armed) Air-Launched Cruise Missile (US designation = AGM-86C/D).

canards Foreplanes, fixed or controllable aerodynamic surfaces ahead of the centre of gravity.

CAP Combat Air Patrol.

capacity The volume swept out on each stroke by the pistons of a piston engine. It is expressed in cc (cubic centimetres) for small engines and in litres (1 litre = 1 000 cc) for larger ones. Also known as displacement or swept volume.

carbon fibre Fine filament of carbon/graphite used as strength element in composites.

CAS (1) Calibrated airspeed, ASI calibrated to allow for air compressibility according to ISA S/L; (2) close air support (ground attack).

casevac Casualty evacuation.

Cat Category. Meanings include runway visibility and decision height minima for ILS.

CATIA Computer-aided three-dimensional interactive analysis: Anglicised form of French CAD proprietary system (Conception assistee tridimensionelle interactive d'applications).

CBLS Carrier, Bomb, Light Stores (a practice bomb carrier).

CBU Cluster bomb unit.

CEAM Centre d'Experiences Aeriennes Militaires.

CEAT Centre d'Essais Aeronautiques de Toulouse.

Ceconite Manmade covering material for light aircraft; trade name.

CEM Combined Effects Munition.

CEO Chief executive officer.

CEV Centre d'Essais en Vol.

CFE Conventional Forces in Europe.

CFRP Carbon fibre-reinforced plastics.

CFT Conformal Fuel Tank (first used on the F-15 but now being applied to a variety of military aircraft).

CG Centre of gravity.

chaff Thin slivers of radar-reflective material cut to length appropriate to wavelengths of hostile radars and scattered in bundles to protect friendly aircraft.

CHAIC Changhe Aircraft Industries Corporation (China).

chord Distance from leading-edge to trailing-edge measured parallel to longitudinal axis.

CIA Central Intelligence Agency.

CIS Commonwealth of Independent [ex-USSR] States. See also RFAS.

CKD Component knocked down, for assembly elsewhere.

clean (1) In flight configuration with landing gear, flaps, slats and so on retracted; (2) Without any optional external stores.

c/n Constructor's number: manufacturer's serial number.

C of A Certificate of Airworthiness; awarded to each individual aircraft (compare Type Certificate).

COD Carrier Onboard Delivery.

COIN Counter-insurgency.

collective pitch Controls pitch of all blades of helicopter main rotor in unison.

combi Civil aircraft carrying both freight and passengers on main deck.

comint Communications intelligence.

composite Material made of two constituents, such as filament, or short whiskers plus adhesive forming binding matrix.

constant-speed Variable-pitch propeller governed by a CSU so that its rotational speed is held constant.

contrarotating Propellers on same axis turning in opposite directions (compare C/R).

CONUS CONtinental United States.

conventional and manual Aeroplane manoeuvring surfaces mechanically linked to pilot's hand and foot controls, unassisted (except, optionally, by aerodynamic or mass balances) and comprising ailerons on the outboard wing, rudder(s) to the rear of fixed tailfin(s) and elevators to the rear of a fixed (but optionally, incidence angle trimmable) tailplane. The description optionally includes leading-edge slats, flaps on inboard trailing-edges and trim tabs, all of which are mentioned separately, if installed. Ailerons which droop in unison with flaps (and thus are not the primary means of lowering stalling speed) are regarded as conventional. Control systems not conforming to the above - in that they have foreplanes, one or more all-moving tail surfaces, or flaperons, and those with mechanical/electronic assistance or interception of the pilot's movements-are described in appropriate detail.

convertible Transport aircraft able to be equipped to carry passengers or cargo, but not both simultaneously.

COO Chief operating officer.

core Gas generator portion of turbofan comprising compressor(s), combustion chamber and turbine(s).

C/R Counter-rotating; propellers of multi-engined aircraft turning in opposite directions on different axes (compare contrarotating).

CRT Cathode-ray tube.

cruising speed Flight speed on less than full engine power, maximum is normally at 75%, if not otherwise specified, but some manufacturers use higher throttle settings.

C-SAR Combat Search And Rescue.

CSAS Command and stability augmentation system (part of AFCS).

CTOL Conventional take-off and landing (compare V/STOL).

CVR Cockpit voice recorder.

CY Calendar year: 1 January to 31 December. Compare FY.

cyclic pitch Controls variation of pitch as helicopter rotor blade makes each revolution.

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D

Dacron Artificial fabric for light aircraft covering; trade name.

DADC Digital air data computer.

DADS Digital air data system.

DARPA Defense Advanced Research Projects Agency (US) (briefly ARPA before February 1996).

DAS Defensive Aids Suite.

databus Electronic highway for passing digital data between aircraft sensors and system processors, usually MIL-STD-1553B or ARINC 419 (one-way) and 619 (two-way) systems.

dB Decibel.

DC Direct Current.

DECU Digital engine (or electronic) control unit.

dem/val Demonstration/validation.

derated Engine restricted to power less than potential maximum (usually such engine is flat rated, which see).

design weight Different authorities have different definitions; weight chosen as typical of mission but usually much less than MTOW.

DF Direction-finder, or direction-finding.

DGAC Direction Generale a l'Aviation Civile. French certification authority.

DHI Daewoo Heavy Industries (South Korea).

dihedral Upward slope of wing from root (or intermediate point) to tip.

disposable load Sum of masses that can be loaded or unloaded, including payload, crew, removable equipment, usable fuel and other consumables; MTOW minus OWE.

DLIR Downward-Looking Infra-Red.

DME UHF distance-measuring equipment gives slant distance to a beacon; DME element of Tacan.

DoD Department of Defense.

dog-tooth A sharp discontinuity in the leadin-edge of a wing or tail surface resulting from an increase in chord (see also sawtooth).

Doppler Short for Doppler radar - radar using fact that received frequency is a function of relative velocity between transmitter or reflecting surface and receiver; used for measuring speed over ground or for detecting aircraft or moving vehicles against static ground or sea.

double-slotted flap One having an auxiliary aerofoil ahead of main surface to increase maximum lift.

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E

EAA Experimental Aircraft Association (divided into local branches called Chapters).

EADS European Aeronautic and Deence Systems Company.

EAP Experimental Aircraft Programme. (Led to the Eurofighter).

EAS Equivalent airspeed. RAS minus correction for compressibility.

ECCM Electronic counter-countermeasures.

ECM Electronic countermeasures.

ECR Electronic Combat and Reconnaissance (Variant of Tornado).

ECS Environmental control system.

EEZ Economic exclusion (or exclusive-economic) zone.

EFIS Electronic flight instrumentation system, in which large multifunction CRT displays replace traditional instruments.

EGPWS Enhanced ground proximity warning system.

EGT Exhaust gas temperature.

ehp Equivalent horsepower, measure of propulsive power of turboprop made up of slip plus addition due to residual thrust from jet.

EICAS Engine indication (and) crew alerting system.

ekW Equivalent kilowatts, SI measure of propulsive power of turboprop (see ehp).

elevon Wing trailing-edge control surface combining functions of aileron and elevator.

elint electronics intelligence.

ELT Emergency locator transmitter, to help rescuers home on to a disabled or crashed aircraft.

EMD Engineering and manufacturing development.

EMBRAER EMpresa BRasiliera de AERonautica (Brazil).

ENAER Empresa Nacional de AERonautica (Chile).

EO Electro-optical.

EPNdB Effective perceived noise decibel, SI unit of EPNL.

ERU Ejector release unit.

ESM (1) Electronic surveillance (or support) measures; (2) Electronic signal monitoring.

ESSS External Stores Support System (for S-70A/UH-60).

ETOPS Extended-range twin (engine) operations (thus sometimes given as EROPS), routeing not more than a given flight time (120, 180 or 240 minutes) from a usable alternative airfield.

EW Electronic warfare.

EWO Electronic Warfare Officer

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F

F Fighter (UK and US designator).

FAA Federal Aviation Administration or Fleet Air Arm (Bitish).

FAC Forward air control (or controller).

factored Multiplied by an agreed number to take account of extreme adverse conditions, errors, design deficiencies or other inaccuracies.

FADEC Full-authority digital engine (or electronic) control.

FAI Federation Aeronautique Internationale.

fail-operational System which continues to function after any single fault has occurred.

fail-safe Structure or system which survives failure (in case of system, may no longer function normally).

FAR Federal Aviation Regulations.

FAR Pt 23 Defines the airworthiness of private and air taxi aeroplanes of 5 670 kg (12 500 lb) MTOW and below.

FAR Pt 25 Defines the airworthiness of public transport aeroplanes exceeding 5 670 kg (12 500 lb) MTOW.

FAV Fuerza Aerea Venezolana. (Venezuelan air force).

FBL Fly-by-light (which see).

FBW Fly-by-wire (which see).

FCS Flight control system.

FDR Flight data recorder (which see).

FDS Flight director system.

feathering Setting propeller blades at pitch aligned with slipstream to minimise drag.

fence A chordwise projection on the surface of a wing, used to modify the distribution of pressure and prevent spanwise flow.

Fenestron Helicopter tail rotor with many slender blades rotating in short duct (registered name).

ferry range Extreme safe range with zero payload.

FFAR Folding fin (or free-flight) aircraft rocket.

field length Measure of distance needed to land and/or take off; many different measures for particular purposes, each precisely defined.

fixed-pitch Propeller with blades fixed to the hub.

FL Flight level. Notional altitude for air traffic control purposes which assumes ISA pressure (1 013.25 mb; 29.92 in Hg) at S/L. Expressed in hundreds of feet; thus FL255 indicates approximately 25 500 ft.

FLI Fighter Lead-In (trainer).

flap A surface carried on the leading- or trailing-edge of a wing and able to move relative to it. The simplest leading-edge flap and so-called plain (trailing-edge) flap is formed by hinging the entire edge of the wing. The Krueger is a leading-edge flap forming part of the wing undersurface, swung down and forwards on arms to give a bluff leading-edge. A split flap is formed by hinging only the undersurface of the trailing-edge. A slotted flap is a hinged trailing-edge which moves aft as well as down on tracks to leave a narrow slot ahead of it: hence double- and triple-slotted. A Fowler flap is a complete auxiliary aerofoil mounted on tracks under a fixed trailing-edge; initially it moves aft, to emerge behind the fixed part of the wing, and at the end of its travel it rotates down. A Gouge flap has an upper surface forming part of a cylinder, and rotates (on rails or brackets) about that cylinder's centre.

flaperon Wing trailing-edge surface combining functions of flap and aileron.

FLAR Federatsii Lvubitelei Aviatsii Rossii, Russian PFA.

flat-four Piston engine having four horizontally opposed cylinders; thus, flat-twin, flat-six and so on.

Flight-adjustable pitch Propeller with blades that can be changed in pitch during flight to a limited extent (eg one way only). Compare variable pitch.

flat rated Propulsion engine capable of giving full thrust or power for take-off at an airfield well above S/L and/or at high ambient temperature (thus, probably derated at S/L).

flight data recorder Crash-protected recorder of dynamic/static pressure, air temperature, control-surface and slat/flap positions, 3-axis accelerations, engine parameters and possibly other variables.

FLIR Forward-looking infra-red.

fly-by-light Flight control system in which signals pass between computers and actuators along fibre-optic leads.

fly-by-wire Flight control system with electrical signalling, without mechanical interconnection between cockpit flying controls and control surfaces.

FM Frequency modulation.

FMA Spanish acronym for Military Aircraft Factory, now Lockheed Martin Aircraft Argentina SA.

FMRAAM Future Medium-Range Air-to-Air Missile.

FMS (1) Foreign military sales (US DoD); (2) Flight management system.

Footprint (1) A precisely delineated boundary on the surface around an airfield, inside which the perceived noise of an aircraft exceeds a specified level during take-off and/or landing;

(2) Dispersion of weapon or submunition impact points.

foreplanes Pivoted canard surfaces forming part of the primary flight control system with authority in pitch and possibly also in roll. See also canards.

FOV Field of view.

Fowler flap See flap.

frequency See radar frequency.

frequency agile (frequency hopping) Making a transmission harder to detect by switching automatically to a succession of frequencies.

FRY Federal Republic of Yugoslavia.

FSD Full-scale development.

FSED Full-scale engineering development.

FY Fiscal year; in US government affairs, runs from 1 October to 30 September (FY05 begins 1 October 2004); in Japan, from 1 April (FY 16 or FY04 began 1 April 2004).

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G

g Acceleration due to mean Earth gravity, that is of a body in free-fall; or acceleration due to rapid change of direction of flight path.

gallons Non-SI measure; 1 Imp gallon (UK) = 4.546 litres, 1 US gallon = 3.785 litres.

GE General Electric (US).

GFRP Glass fibre-reinforced plastics.

‘glass cockpit’ Cockpit in which dial instruments are replaced by multifunction electronic displays.

glass fibre Spun molten glass; see GFRP.

glideslope Element giving vertical (height) guidance in ILS.

glove (1) Fixed portion of wing inboard of variable sweep wing;

(2) additional aerofoil profile added around normal wing for test purposes.

GmbH Gesellschaft mit beschrankter Haftpflicht (or Haftung) (German company constitution).

GPMG General Purpose Machine Gun (UK weapon).

GPS Global Positioning System, US military/civil satellite-based precision navaid.

GPU Ground power unit (not part of aircraft).

GPWS Ground-proximity warning system.

GR Ground-attack and Reconnaissance (UK designator).

green aircraft Aircraft flyable but unpainted, unfurnished and basically equipped.

gross wing area See wing area.

ground-adjustable pitch Propeller with blades that can be adjusted in pitch by an engineer on the ground. Compare flight adjustable and variable pitch.

GS See glideslope.

gunship Aircraft designed for battlefield attack; helicopter gunships normally with slim body carrying pilot and weapon operator only.

GUP Gosudarstvennoye Unitarnoye Predpriyatie (Russian State Unitary Enterprise).

GvTBAP Gvardeyskyy Tyazhelyy Bombardirovochnyy Aviatsionnyy Polk = Guards heavy bomber aviation regiment.

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H

h Hour(s).

HAC Helicoptere Anti-Char (anti-tank helicopter), version of Tigre/Tiger.

HAL Hindustan Aeronautics Limited (India).

HAMC Harbin Aircraft Manufacturing Corporation (China).

handed Rotating in opposite directions.

HAP Helicoptere d’Appui et de Protection (escort/fire support helicopter), version of Tigre/Tiger.

hardened Protected as far as possible against nuclear explosion.

hardpoint Reinforced part of aircraft to which external load can be attached, for example weapon or tank pylon.

HARM High-speed Anti-Radar[/Radiation] Missile (US designation AGM-88).

HAS Helicopter Anti-Submarine (UK designator).

HC Helicopter Cargo (UK designator).

HCP Helicoptere de Combat Polyvalent (multirole combat helicopter) applied to Tigre/Tiger.

HDD Head-down display (which see).

HDU Hose-drum unit.

head-down display On the cockpit instrument panel (as distinct from a HUD).

head-level display Immediately below HUD.

helicopter Rotary-wing aircraft both lifted and propelled by one or more power-driven rotors turning about substantially vertical axes.

HF High frequency.

HIFR Helicopter in-flight refuelling.

HIRF High-intensity radiated field(s).

HMA Helicopter, Maritime Attack (UK designator).

HMD Helmet-mounted display; hence HMS = sight.

HMMWV High-Mobility Multi-purpose Wheeled Vehicle. Aka Humvee.

HOCAC Hands on cyclic and collective.

homebuilt Aircraft built/assembled from plans or kits.

HOT Haut subsonique Optiquement teleguide tire d’un Tube (subsonic optically-tracked tube-launched). French acronym for an anti-tank missile.

hot-and-high Adverse combination of airfield height and high ambient temperature, which lengthens required take-off distance.

HOTAS Hands on throttle and stick.

hot refuelling Replenishment of fuel while engine(s) running.

hovering ceiling Ceiling of helicopter (corresponding to air density at which maximum rate of climb is zero), either GE or OGE.

HP High pressure (HPC, compressor; HPT, turbine).

hp Horsepower, non-SI unit of power. Equal in the United Kingdom to 550 foot-pounds per second and in the United States to 745.7 watts.

HSA Hawker Siddeley Aviation (UK).

HSI Horizontal situation indicator.

HUD Head-up display (bright numbers and symbols projected on pilot's aiming sight glass and focused on infinity so that pilot can simultaneously read display and look ahead). The term is increasingly rendered in the USA as "heads up", which is incorrect.

Hz Hertz, cycles per second.

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I

IAF Indian Air Force.

IAI Israel Aircraft Industries.

IAS Indicated airspeed, airspeed indicator reading corrected for instrument error.

IATA International Air Transport Association.

ICAO International Civil Aviation Organisation.

ICH Improved Cargo Helicopter (US Army name of CH-47F).

IDF/AF Israeli Defence Force/Air Force.

IDS InterDictor Strike (variant of Tornado).

IFF Identification friend or foe.

IFR (1) Instrument flight rules (compare VFR); (2) in-flight refuelling.

IGE In ground effect: helicopter performance with theoretical flat horizontal surface just below it (for example mountain).

IIR Imaging infra-red.

ILS Instrument landing system. See Cat.

Imperial gallon 1.20095 US gallons: 4.54