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Glossary — Complete List of Terms

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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).


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.



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.



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.



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.



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



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).



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.



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.



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: 4.546 litres.

INAS (1) Integrated nav/attack system (2) Inertial Navigation and Attack (3) Indian Naval Air Station.

Inc Incorporated (company constitution).

incidence The angle at which the wing is set in relation to the fore/aft axis. Often wrongly used to mean angle of attack (which see).

inertial navigation Measuring all accelerations imparted to a vehicle and, by integrating these with respect to time, calculating speed at every instant (in all three planes) and, by integrating a second time, calculating total change of position in relation to starting point.

INS Inertial navigation system.

integral construction Machined from solid instead of assembled from separate parts.

integral tank Fuel (or other liquid) tank formed by sealing part of structure.

intercom Wired telephone system for communication within aircraft.

inverter Electric or electronic device for inverting (reversing polarity of) alternate waves in AC power to produce DC.

IOC Initial operational capability.

IR Infra-red.

IRADS Infra-red acquisition and designation system.

IRCM Infra-red countermeasures.

IRIAF Islamic Republic of Iran Air Force.

IRLS Infra-red linescan (builds TV-type picture showing cool and hot regions as contrasting shades).

IRS Inertial reference system.

IRST Infra-red search and track.

ISA International Standard Atmosphere (1013.5 mb, 1 225 g/m3 and 15°C at mean sea level; lapse rate 1.98°C per 1 000 ft up to –56.5°C at 36,090 ft).

ISAR Imaging Synthetic Aperture Radar.



JAA Joint Aviation Authorities.

JAR Joint Aviation Requirements, agreed by all major EC countries (JAR 25 equivalent to FAR Pt 25).

JAR-VLA JAR classification for Very Light Aircraft (MTOW limit of 750 kg; 1 653 Ib).

JASDF Japan Air Self-Defence Force.

JASSM Joint Air-to-Surface Stand-off Missile (US designation = AGM-158).

JATO Jet-assisted take-off (actually means rocket-assisted).

JCAB Japan Civil Airworthiness Board.

JDA Japan Defence Agency.

JDAM Joint Direct Attack Munition, being a GPS-duidane package added to existing bomb bodies, US designations being GBU-29 (with Mk 81 bomb), GBU-30 (Mk 82), GBU-31 (Mk 83), GBU-32 (Mk 84 or BLU-109/B) and GBU-35 (BLU-110/B).

JGSDF Japan Ground Self-Defence Force.

JMSA Japan Maritime Safety Agency.

JMSDF Japan Maritime Self-Defence Force.

joined wing Tandem wing layout in which forward and aft wings are swept so that the outer sections meet.

JPATS Joint Primary Aircraft Training System (Beech T-6A Texan ll).

JSC Joint stock company.

JSF Joint Strike Fighter. (The Lockheed Martin F-35).

JSOW Joint Stand-Off Weapon, US designations being AGM-154A (with 145 BLU-97/B bomblets), AGM-154B (with six BLU-108/B bomblets) and AGM-154C (with BROACH penetrating warhead).

J-STARS US Air Force/Navy Joint Surveillance and Target Attack Radar System in Northrop Grumman E-8C.

JTIDS Joint Tactical Information Distribution System (NATO Link 16).

Junkers aileron Control surface (sometimes flaperon) suspended from mountings to the rear of wing trailing edge.

JVX Joint Vertical experimental – the tiltrotor project which became the V-22 Osprey.



K Kerosene (tanker – UK designator).

Ka Kamov (Russian design bureau).

KAI Korean Aerospace Industries (South Korea).

kbit One thousand bits of memory.

Kevlar Aramid fibre used as basis of high-strength composites material.

kg Kilogram (2.20462 lb).

kitbuilt Prefabricated aircraft for amateur assembly.

KK Kabushiki Kaisha (Japanese company constitution

km/h Kilometres per hour.

kN KiloNewtons (Nx103). See N.

knot 1 n mile per hour (1.852 km/h; 1.15078 mph).

Krueger flap Hinges down and then forward from be the leading-edge.

kVA Kilovolt-amperes.

kW Kilowatt, SI measure of all forms of power (not just electrical). Equal to 1000 Watts.



LAMPS Light airborne multipurpose system.

LANTIRN Low-altitude navigation and targeting by infra-red at night.

LAPES Low-altitude parachute extraction system.

LASTE Low-Altitude Safety and Targeting.

LBA Luftfahrtbundesamt (German civil aviation authority).

Ib Pound, non-SI unit of weight: 0.453592 kg.

Ib st Pounds of static thrust.

LCD Liquid crystal display, used for showing instrument information.

LCN Load classification number, measure of ‘flotation’ of aircraft landing gear linking aircraft weight, weight distribution, tyre numbers, pressures and disposition.

LED Light-emitting diode.

LERX Leading-Edge Root eXtension.

LGB Laser-Guided Bomb.

LHTEC Light Helicopter Turbine Engine Company (US), jont venture between Rolls-Royce (formerly Allison) and Honeywell (formerly Garrett).

LHX Light Helicopter experimental (RAH-66 Comanche).

LII Grovom Flight Institute.

LIFT Lead-In Fighter Trainer.

lift dumper Spoiler designed to open on landing to reduce lift and thus increase effectiveness of wheel braking.

LINS Laser inertial navigation system.

litre SI unit of volume (0.264177 US gallon; 0.219975 Imp gallon).

LLTV Low-light TV (thus, LLLTV, low-light level); see ALLTV.

LO Low-observables, which see (stealth).

load factor (1) Percentage of maximum payload; (2) design factor (g limit) for airframe.

LOC Localiser (which see).

LOCAAS Low-cost anti-armour submuntion.

localiser Element giving steering guidance in ILS.

LOH Light observation helicopter.

loiter Fly for maximum endurance, at much less than normal cruise speed.

longerons Principal fore-and-aft structural members (for example in fuselage).

Loran Long-range navigation; family of hyperbolic navaids based on ground radio emissions, now mainly Loran C.

LOROP Long-range oblique photography.

LOS Line of sight.

Low-observables Materials, structures and techniques designed to minimise aircraft signatures of all kinds.

lox Liquid oxygen.

LP Low pressure (LPC, compressor; LPT, turbine).

LRIP Low-rate initial production.

LRMTS Laser ranger and marked-target seeker.

LRU Line-replaceable unit.

Ltd Limited (company constitution).



m Metre(s), SI unit of length (3.28084 feet.)

M or Mach number The ratio of the speed of a body to the speed of sound (340 m; 1 116 ft/s in air at 15 degrees C) under the same ambient conditions.

MAD Magnetic anomaly detector.

mass balance Mass attached to flight control surface, typically ahead of hinge axis, internally or externally, to reduce or eliminate coupling with airframe flutter modes.

mass flow Mass of air passing per second (usually at T-O, S/L).

MAWS Missile-approach warning system.

mb Millibar, bar x 10-3.

MBB Messerschmitt Bolkow Blohm (Germany).

McDD McDonnell Douglas (US). Also MD or MDD.

MCM Mine countermeasures.

medevac Medical evacuation.

MFD Multifunction (electronic) display.

MFI mnogofunktseeonahl’nyy frontovoy istrebeetel = multi-role tactical fighter.

MHz Megahertz: 1 million (106 ) Hertz.

Mi Mil (Russian design bureau).

MICA Missile d’Interception et de Combat Aerien = combat and air-intercept missile.

microlight See ultralight.

MIDS Multifunction information distribution system.

MiG Mikoyan-Guryevich (Russian design bureau). Also Mikoyan-Gurevich.

MKR Marker beacon receiver.

MLS Microwave landing system.

MLU Mid-life update.

MLW Maximum landing weight.

mm Millimetres, metres x 10-3.

MMO Maximum operating Mach number.

MMS Mast-mounted sight.

MMW MilliMetric (or MilliMetre) Wave (as AN/APG-78 Longbow radar for the AH-64D Apache Longbow helicopter).

MoD Ministry of Defence.

monocoque Structure with strength in outer shell, devoid of internal bracing (semi-monocoque, with some internal supporting structure).

MoU Memorandum of Understanding.

MPA Maritime patrol aircraft.

mph Miles per hour.

MR Maritime Reconnaissance (UK designator).

MRA Maritime Reconnaissance and Attack (UK designator).

MRCA Multi-Role Combat Aircraft (re-named Tornado).

MRT Multi-Role Transport.

MRTT Multi-Role Taneker/Transport.

MSIP Multistage/d improvement program (US).

MTBF Mean time between failures.

MTI Moving-target indication (radar).

MTOW Maximum take-off weight (minus taxi/run-up fuel).

MTU Motoren und Turbinen Union (Germany).

MYP Multiyear procurement (US).

MZFW Maximum zero-fuel weight.



N Newton, SI unit of force, = 0.22480455 lb force.

N/A or n/a Not Available or Not Applicable.

NACES Navy aircrew common ejection seat (US).

NAMC Nanchang Aircraft Manufacturing Company (China).

NAS Naval Air Station (US).

NASA National Aeronautics and Space Administration (US).

NASC Naval Air Systems Command (also several other aerospace meanings) (US).

NATC Naval Air Training Command or Test Center (also several other aerospace meanings) (US).

NATO North Atlantic Treaty Organisation.

nav/com Navigation and communications receiver.

NBAA National Business Aircraft Association (US).

NBC Nuclear, biological, chemical (warfare).

NDT Non-destructive testing.

Newton See N.

NFH Naval Frigate Helicopter (NH 90 variant).

NFO Naval flight officer; second crew member in US Navy aircraft; compare WSO.

N-G Northrop Grumman (US).

Ni/Cd Nickel/cadmium.

Nib Forward-pointing extension at inner end of fixed glove on VG aircraft or leading-edge root extension on light aircraft.

n mile nautical mile, 1.852 km, 1.15078 miles.

NOE Nap-of-the-Earth (low flying in military aircraft, using natural cover of hills, trees and so on).

NOTAR NO TAil Rotor – patented tail stabilisation system developed for MD 500-type helicopter.

NV Naamloze Venuootschap (Belgian/Netherlands company constitution).

NVG Night vision goggles.

NVS Noise vibration suppression.



OAO Otkrytolye Aktsionernoye Obshchestvo (JSC; Russian company constitution).

OAT Outside air temperature.

OBIGGS Onboard inert gas generating system.

OBOGS Onboard oxygen generating system.

OCU (1) Operational Conversion Unit; (2) Operational Capabilities Upgrade.

OEI One engine inoperative.

OEU Operational Evaluation Unit.

offset Workshare granted to a customer nation to offset the cost of an imported system.

OGE Out of ground effect; helicopter hovering, far above nearest surface.

OKB Opytnyi Konstruktorskoye Byuro (Russian experimental design bureau).

Omega Long-range hyperbolic radio navaid.

000 Obshchestvo Ogranichennoye Otvetstvennostyu (Russian company constitution).

opeval Operational evaluation.

OSD Out-of-Service Date.

OSF Optronique Secteur Frontale.

OTH Over-the-horizon.

OTHT Over-the-horizon targeting.

OTPI On-top position indicator (indicates overhead of submarine in ASW).

OWE Operating weight empty. MTOW minus payload, usable fuel and oil and other consumables (thus, includes crew).



P&W Pratt & Whitney (US).

P&WC Pratt & Whitney Canada.

PAC Pakistan Aeronautical Complex.

PAH PanzerAbwehr-Hubschrauber (Army [anti-] tank helicopter).

Pallet (1) for freight, rigid platform for handling by forklift or conveyor (2) for missile, interface mounting and electronics box outside aircraft.

Panavia Tri-national consortium formed to produce Tornado, comprising MBB of Germany (now EADS/DASA), Aeritalia of Italy (now Alenia Aerospazio) and BAC (now BAE Systems).

Pascal SI unit of pressure =1 Nm-2 (one Newton per square metre).

payload Disposable load generating revenue (passengers, cargo, mail and other paid items): in military aircraft loosely used to mean total load carried of weapons. cargo or other mission equipment.

PDLCT Day/night TV/thermal imaging laser-designation pod produced by Thomson-CSF.

Performance Aircraft capabilities after S/L take-off at MTOW in ISA with normal full tankage, except as otherwise specified, and with landing data at MLW (where different).

PFA Popular Flying Association (UK).

PGM Precision-guided munition.

phased array Radar in which the beam is scanned electronically in one or both axes without moving the antenna.

Pirate Passive infra-red airborne tracking equipment.

PLA (1) People’s Liberation Army (China) (2) Prelaunch activities.

PLAAF People’s Liberation Army Air Force (China).

PLANAF People’s Liberation Army Naval Air Force (China).

plane A lifting surface (for example wing, tailplane).

plc Public limited company (company constitution).

PLSS Precision Location Strike System.

plug door Door larger than its frame in pressurised fuselage, either opening inwards or arranged to retract parts before opening outwards.

plume The region of hot air and gas emitted by a helicopter jetpipe.

ply Indication (ply rating) of tyre strength in a specific application; not necessarily the actual number of carcass plies in the tyre.

pneumatic de-icing Covered with flexible surfaces alternately pumped up and deflated to throw off ice.

port Left side, looking forward.

power-by-wire Using electric power alone (not electro-hydraulic) to drive control surfaces and perform other mechanical tasks.

power loading Aircraft weight (usually MTOW) divided by total propulsive power or thrust at T-O. For helicopters, based on transmission rating rather than total engine power.

power train A complete mechanical drive system, for example the sequence of gearwheels, clutches and shafts transmitting power from one or more engines to the rotors of a helicopter.

PPV Pre-production verification.

prepreg Glass fibre cloth or rovings pre-impregnated with resin to simplify layup.

pressure fuelling Fuelling via a leakproof connection through which fuel passes at high rate under pressure.

primary flight controls Those used to control trajectory of aircraft (thus, not trimmers, tabs, flaps, slats, airbrakes or lift dumpers, and so on).

primary flight display Single screen bearing all data for aircraft flight-path control.

propfan A family of new-technology propellers characterised by multiple scimitar-shaped blades with thin sharp-edged profile. Single and contrarotating examples promise to extend propeller efficiency up to an aircraft Mach number of about 0.8.

proprotor Large propeller, tilting for forward or vertical flight.

PT Pesawat Terbang (Indonesian company constitution).

Pty Proprietary (company constitution).

pulse Doppler Radar sending out pulses and measuring frequency-shift to detect returns only from moving target (s) seen against background clutter.

PVO Protivovosduzhnaya Oborona (Part of Russian air force).

pylon Structure linking aircraft to external load (engine nacelle, drop tank, bomb, and so on).

PZL Polskie Zadlady Lotnicze (Polish Aviation Factory).



Q US designation prefix for done-configured aircraft.



R Radio (ELINT/SIGINT) – UK designator.

RAAF Royal Australian Air Force.

RAC-MiG Russian Aircraft Corporation-MiG (RSK-MiG in Russian – the Mikoyan Guryevich design bureau and former state production factories).

Radar frequency Operating bands of airborne radars are given according to frequency. That part of the electromagnetic spectrum appropriate to above-surface short-range communication and radar (but not OTH) used in aviation is given in the adjacent table with an approximate cross-reference to previously used wavelength bands.

The Electromagnetic Spectrum



General Designation

US Band
30-3 kHz
10,000-100 km
3-30 kHz
100-10 km
30-300 kHz
10-1 km
300 kHz-3 MHz
1,000-100 m
3-30 MHz
100-10 m
30-230 MHz
10-1.3 m
230-250 MHz
13-1.2 m
250-300 MHz
1.2-1 m
300-500 MHz
100-60 cm
500-1,000 MHz
60-30 cm
1-2 GHz
30-13 cm
2-3 GHz
15-10 cm
3-4 GHz
10-7.5 cm
4-6 GHz
7-5.5 cm
6-8 GHz
5-7.5 cm
8-10 GHz
3.75-3 cm
10-12.5 GHz
3-2.5 cm
12.5-18 GHz
2.5-1.6 cm
18-20 GHz
1.6-1.5 cm
20-26.5 GHz
1.5-1.1 cm
26.5-30 GHz
1.1-1 cm
30-40 GHz
10-7.5 mm
40-60 GHz
7.5-5 mm
60-100 GHz
5-3 mm
100-300 GHz
3-1 mm

Notes: Three overlapping descriptive systems are used in the West.
General designations are Extremely Low, Very Low, Low, Medium, High, Very High, Ultra High, Super High and Extremely High Frequency.
Frequencies are measured in kilo (1,000), mega (1,000,000) and giga (1,000,000,000) cycles per second (Hertz); wavelengths measured in kilometres, metres, centimetres and millimetres. 'NATO' bands describe radar and electronic warfare equipment; 'US' bands are used for radar and satellite communications. The latter's bounds are slightly 'elastic'.
Aircraft-to-ground voice communications for air traffic control and similar purposes (including ground ration beacons) uses 108-136 MHz in the VHF band and 225-400 MHz in the V/UHF bands, the latter principally military, and not entirely accurately termed 'UHF'.

radius The approximate distance an aircraft can fly from base and return without intermediate landing.

RAF Royal Air Force

RAI Registro Aeronautico Italiano (Italian civil aviation authority).

RAM Radar absorbent material.

ramp weight Maximum weight at start of flight (MTOW plus taxi/run-up fuel).

range Too many definitions to list, but essentially the distance an aircraft can fly (or is permitted to fly) with specified load and usually while making allowance for specified additional manoeuvres (diversions, standoff, go-around and so on).

RAS Rectified airspeed, IAS corrected for position error.

raster Generation of large-area display, for example TV screen, by close-spaced horizontal lines scanned either alternately or in sequence.

RAT Ram air turbine.

rating Any of several values of thrust or shaft power which an engine is qualified (usually also guaranteed) to develop under specified conditions.

RCS Radar cross-section; apparent size of echo.

Recce Reconnaissance.

redundant Provided with spare capacity or data channels and thus able to survive failures.

reversion Ability to switch to manual control following failure of a powered system.

RFAS Russian Federation and Associated States (CIS).

RFP Request(s) for proposals.

RHAW Radar Homing and Warning.

rigid rotor See bearingless rotor.

RMAF Royal Malaysian Air Force.

RMI Radio magnetic indicator; combines compass and navaid bearings.

R/Nav Calculates position, distance and time from groups of airways beacons.

RNS Russian Naval Ship.

RoA Radius of Action

RoCAF Republic of China (Taiwan) Air Force.

RON Research octane number of fuel.

roving Multiple strands of fibre, as in a rope (but usually not twisted).

rpm Revolutions per minute.

RPV Remotely piloted vehicle (pilot in other aircraft or on ground); contrast UAV.

R-R Rollys-Royce.

RS Reconnaissance Squadron.

RSA Reseau du Sport de l’Air.

ruddervators Flying control surfaces, usually a V tail, that control both yaw and pitch attitude.

RVSM Reduced vertical separation minimum. Halved (1 000 ft) air traffic control separation between FL290 and FL410.

RWR Radar warning receiver.



s Second(s)

S Sikorsky (model designator, e.g S-60).

SA Societe Anonyme (France, Romania), Sociedad Anonima (Brazil, Spain) or Spolka Akeyjna (Poland) (company constitution).

SAAF South African Air Force.

SAC Strategic Air Command.

safe-life A term denoting that a component has proved by testing that it can be expected to continue to function safely for a precisely defined period before replacement.

SALT/START Strategic Arms Limitation Talks/Strategic Arms Reduction Talks.

SAM Surface-to-air missile.

SAR (I) Search and rescue; (2) synthetic aperture radar.

SARH Semi-Active Radar Homing.

SAS Stability augmentation system.

satcom Satellite communications.

sawtooth Same as dog-tooth.

SCALP Systeme de Croisiere conventional Autonome a Longue Portee de precision – French derivative of APACHE weapon.

Sdn Bhd Sendirian Berhad (Malaysian company constitution).

SEAD Suppression of enemy air defence(s).

semi-active Homing on to radiation reflected from target illuminated by radar or laser energy beamed from elsewhere (for example, from launch aircraft).

sensitive altimeter Altitude indicator of mechanical type, having acute sensitivity.

SEPECAT Societe Europeane de Productin de l’Avion Ecolet et Combat Appui Tactique = European company to produce the [Jaguar] training and tactical combat aircraft. 50:50 Anglo-French company responsible for Jaguar, with BAC (now BAE Systems) and Breguet (now Dassault).

service ceiling Usually height equivalent to air density at which maximum attainable rate of climb is 100 ft/min.

servo A device which acts as a relay, usually augmenting the pilot's efforts to move a control surface, or the like.

sfc Specific fuel consumption (which see).

SFW Sensor-Fuzed Weapon.

shaft Connection between gas-turbine and compressor or other driven unit. Two-shaft engine has second shaft, rotating at different speed, surrounding the first (thus. HP surrounds inner LP or fanshaft).

shipment One item or consignment delivered (by any means of transport) to customer.

shp Shaft horsepower, measure of power transmitted via rotating shaft.

shroud Many meanings, including: (1) a fixed circular duct surrounding a fan or propfan; (2) a ring formed by lateral projections on a rotor (for example fan) blade (part-span or at the tip); (3) a portion of a wing or other fixed aerofoil projecting aft over the leading-edge of a hinged or otherwise movable surface such as a flap, aileron or elevator.

SI Système International (d’Unités). French abbreviation meaning International System of Units: an internationally accepted unit of measurement under the Système International d’Unités in science and technology. There are seven fundamental units: the metre, kilogram, second, ampere, kelvin, candela, and mole, and two supplementary units, the radian and steradian.

sideline noise EPNdB measure of aircraft landing and taking off, at point 0.25 n mile (2- or 3-engined) or 0.35 n mile (4-engined) from runway centreline.

sidestick Control column in the form of a short handgrip beside the pilot.

sigint Signals intelligence.

signature Characteristic 'fingerprint' of all acoustic or electromagnetic radiation (radar, IR, and so on).

single-aisle Passenger cabin has seats on each side of a single aisle along or near the centre.

single-shaft Gas-turbine in which all compressors and turbines are fixed to common shaft.

SIVAM Sistema de Vigilancia da Amazonia – Brazil’s surveillance programme for its Amazon region.

S/L Sea level.

SLAM Stand-off Land Attack Missile (US designation = AGM-84G).

SLAM-ER Stand-off Land Attack Missile – Expanded Response (US designation = AGM-84H).

SLAR Side-looking airborne radar.

slat Auxiliary curved or mini-aerofoil surface designed to prevent flow breakaway from a wing or tail. On a tail leading-edge it may be fixed, leaving a narrow slot. On a wing it is almost always retractable, normally flush with the wing profile but extended (under power or by aerodynamic lift) to leave a narrow slot for take-off, low-speed loiter or landing.

SLEP Service (or Structural) Life Extension Programme.

slot, slotted See slat.

SMD Stand-off Munitions Dispenser.

snap-down Air-to-air interception of low-flying aircraft by AAM fired from fighter at a higher altitude.

SNECMA Societe Nationale d’Etude et de Construction de Moteurs d’Aviation (France).

SOA Special Operations Aviation.

SOCAT Romanian acronym for the IAR-Brasov/Elbit upgrade of 24 IAR-330L Pumas with modern avionics and armament.

SOM Stand-Off Munitions.

SONAR, sonar Sound navigation and ranging.

SpA Societa per Azioni (Italian company constitution).

specific fuel consumption Rate at which fuel is consumed divided by power or thrust developed, and thus a measure of engine efficiency. For jet engines (air-breathing, not rockets) unit is mg/Ns, milligrams per Newton-second; for shaft engines unit is µg/J, micrograms (millionths of a gram) per Joule (SI unit of work or energy).

spoiler Plank-like surface normally recessed into top of wing, hinged up under power to reduce (spoil) lift and increase drag. Used asymmetrically for lateral control.

spoileron Small spoiler augmenting ailerons.

sportplane Light aircraft design in which performance takes precedence over utility.

Sp. z o.o Spolka z ograniczona odpowiedzialnoscia (Polish company constitution)

SRAM Short-Range Attack Missile.

Srl Societa Reponsibilita Limitata (Italian company constitution).

SSB Single-sideband (radio).

SSN Nuclear attack submarine.

SSR Secondary surveillance radar.

SST Supersonic transport.

st Static thrust.

stabilator One-piece, all-moving horizontal tail, combining functions of horizontal stabiliser and elevator.

stabilizer Tailplane (US); vertical stabilizer = fin.

stall Sudden near-total loss of lift of a wing because AoA has exceeded a critical value.

stall strips Sharp-edged strips on wing leading-edge to induce stall to initiate at that point.

stalling speed Airspeed at which aircraft stalls at 1 g.

starboard Right side, looking forward.

static inverter Solid-state (not rotary machine) inverter of alternating wave-form to produce DC from AC.

STC Supplementary Type Certificate.

stealth See low-observable

stick-pusher Stall-protection device that forces pilot's control column forward as stalling angle of attack is neared.

stick-shaker Stall-warning device that noisily shakes pilot's control column as stalling angle of attack is neared.

STO Short Take-Off.

STOL Short take-off and landing. (Several definitions, stipulating allowable horizontal distance to clear screen height of 35 or 50 ft or various SI measures.)

store Object carried as part of payload on external attachment (for example bomb, drop tank).

STOVL Short take-off, vertical landing.

strobe light High-intensity flashing beacon.

Su Sukhoi (Russian design bureau).

supercritical wing Wing of relatively deep, flat-topped profile generating lift right across upper surface instead of concentrated close behind leading-edge.

sweepback Backwards inclination of wing or other aerofoil, seen from above, measured relative to fuselage or other reference axis, usually measured at quarter chord (25 per cent) or at leading-edge.



t Tonne, 1 Megagram, 1 000 kg.

T Trainer (UK and US designator).

tab Small auxiliary surface hinged (flight-adjustable) or attached in a fixed position (ground-adjustable) to trailing-edge of control surface for trimming, balancing (reducing hinge moment: force needed to operate main surface) or in other way assisting pilot. Compare anti-balance tab.

tabbed flap Fitted with narrow-chord tab along trailing-edge which deflects to greater angle than main surface.

TAC Tactical Air Command.

TACAMO Take Charge And Move Out – USN AVLF relay system.

Tacan Tactical air navigation, UHF navaid giving bearing and distance to ground beacons; distance element (see DME) can be paired with civil VOR.

taileron Left and right tailplanes used as primary control surfaces in both pitch and roll.

tailplane Horizontal stabiliser; main horizontal tail surface, originally fixed and carrying hinged elevator(s) but today often a single ‘slab’ serving as control surface (see stabiliser, stabilator).

TANS Tactical air navigation system: Decca Navigator or Doppler-based computer, control and display unit.

TARPS Tactical Airborne Reconnaissance Podded System.

TAS True airspeed, EAS corrected for density (often very large factor) appropriate to aircraft altitude.

TBAP Tyazhelyy Bombardirovochnyy Aviatsionnyy Polk = heavy bomber aviation regiment.

TBO Time between overhauls.

t/c ratio Ratio of the thickness (aerodynamic depth) of a wing or other surface to its chord, both measured at the same place parallel to the fore-and-aft axis.

TCAS Traffic-alert and collision-avoidance system.

Tercom Terrain-comparison (or contour-matching), navigation aid which compares relief of terrain with profile stored in memory.

TERPROM TERrain PROfile Matching. (Same as Tercom).

TFR Terrain-following radar (for low-level attack).

TFW Tactical Fighter Wing.

thickness Depth of wing or other aerofoil; maximum perpendicular distance between upper and lower surfaces.

thrust vectoring Rotation of a vehicle's thrust axis to control its trajectory or support its weight.

TIALD Thermal imaging and laser designation (pod).

tiltrotor Aircraft with fixed wing and rotors that tilt up for hovering and forward for fast flight.

TINS Tactical Inertial Navigation System.

T-O Takeoff

T-0 noise EPNdB measure of aircraft taking off, at point directly under flight path 3.5 n miles from brakes-release.

TOGW Take-off gross weight (not necessarily MTOW).

TOW Tube-launched, Optically-tracked, Wire-guided (anti-tank guided missile). Designation = BGM-71.

ton Imperial (long) ton = 1 016 t or 2 240 Ib, US (short) ton = 0.9072 t or 2 000 lb.

track Distance between centres of contact areas of main landing wheels measured left/right across aircraft (with bogies, distance between centres of contact areas of each bogie).

transceiver Radio transmitter/receiver.

transformer-rectifier Device for converting AC to DC at a different voltage.

transponder Radio transmitter triggered automatically by a particular received signal, as in secondary surveillance radar (SSR).

TsENTROSPAS (in Russian Federation) Ministry for Civil Defence, Emergencies and Elimination of the Consequences of Natural Disasters.

TTH Troop Trnasport Helcopter (NH-90 variant).

Tu Tupolev (Russian design bureau).

turbofan Gas-turbine jet engine generating most thrust by a large-diameter cowled fan, with small part added by jet from core.

turbojet Simplest form of gas turbine comprising compressor, combustion chamber, turbine and propulsive nozzle.

turboprop Gas turbine in which as much energy as possible is taken from gas jet and used to drive reduction gearbox and propeller.

turboshaft Gas turbine in which as much energy as possible is taken from gas jet and used to drive high-speed shaft (which in turn drives external load such as helicopter transmission).

twist Progressive change of angle of incidence of a wing, rotor blade or other aerofoil from root to tip.

Type Certificate Airworthiness licence granted to enable a manufacturer to produce and market a specified type of aircraft (compare C of A).

tyre sizes Five systems of classification are in current use; Type I, consisting of a single figure indicating nominal diameter in inches, is obsolete. See adjacent table and also ‘ply’.

Tyre classification

Classification Name

Nominal Diameter
Nominal Section Width
Nominal Rim Diameter
Type III
8.5 in
10 in
Type VII
49 in
17 in
Three Part
49 in
19 in
20 in
32 in
8.8 in
16 in
670 mm
210 mm
12 in



UAE United Arab Emirates

UAV Unmanned (or uninhabited) aerial vehicle; contrast RPV.

UHCA Ultra-high capacity airliner.

UHF Ultra-high frequency.

UHT UnterstutuzungHubschrauber Tiger – the final anti-tank/fire support configuration of German Army Tigers, replacing original PAH-2.

UK United Kingdom.

ultralight Light aircraft with parameters below specified national limits, qualifying for less rigorous licensing; also known as microlight. See table.

540 kg
300 kg 2
35 kt 3
450 kg 2
35 kt 3
472.5 kg
450 kg
35 kt
254 lb
5 USg
1,232 lb

1 Ultra leger motorise; criteria accepted by several European countries.

2 Plus 10 per cent for seaplanes and amphibians.

3 Plus 5 percent for seaplanes and amphibians.

UN United Nations.

upper surface blowing Turbofan jet expelled over upper surface of wing to increase lift.

usable fuel Total mass of fuel consumable in flight, usually 95 to 98 per cent of system capacity.

USAF United States Air Force.

USCG United States Coast Guard.

useful load Usable fuel and other consumables plus payload.

US gallon 0.83267 Imperial gallon; 3.785 litres.

USMC United States Marine Corps.

USN United States Navy.

USNR United States Naval Reserve.

USSR Union of Soviet Socialist Republics (see CIS).

UTTAS Utility Tactical Transport Aircraft System.

UV Ultra-violet.



‘V-speeds’ Shorthand notation of significant speeds within an aircraft's flight envelope (see table).

V1 Decision speed, up to which it should be possible to abort a take-off after failure of the critical engine and stop safely within the remaining runway length. After reaching V1 the take-off must be continued.

V2 Minimum take-off safety speed.

VA Design manoeuvring speed. The speed below which abrupt and extreme control movements are possible (though not advised) without exceeding the airframe’s limiting load factors.

VB Design speed for maximum gust intensity.

VC Design cruising speed.

VD Design diving speed.

VDF Maximum demonstrated diving speed. Also MDF, maximum demonstrated Mach No. in a dive.

VE Maximum speed at which landing gear (or other item) may be extended or retracted (cycled).

VFE Maximum flap extension speed (top of white arc on ASI).

VH Maximum level-flight speed with maximum continuous power.

VLE Maximum speed with landing gear extended.

VMCA Minimum control speed (air). Minimum speed at which directional control of a multi-engined aircraft can be maintained after failure of critical engine (in effect, the lowest speed at which the aircraft possesses sufficient rudder authority to counteract the yaw induced by asymmetric thrust).

VMU Minimum unstick speed.

VNE Never exceed speed.

VMO Maximum operating speed. Also MMO, maximum operating Mach No.

VNO Normal operating speed. The maximum structural cruising speed allowable for normal operating conditions.

VR Rotation speed, at which to raise the nose for take-off.

VRA Rough air speed. Maximum recommended airspeed for penetrating turbulent air.

VREF Any reference or ‘bug’ speed, typically quoted for approach speeds.

VSO Stalling speed at maximum take-off weight, in landing configuration with flaps and landing gear down, at sea level, ISA conditions (bottom of white arc on ASI). Also VS, stalling speed ‘clean’, and VS1, stalling speed for a given configuration other than ‘clean’.

VSSE Minimum speed for deliberate shutting down of one engine for purposes of asymmetric flight training.

VX Best angle of climb speed on all engines. Sometimes (UK usage) V%.

VXSE Best engine out angle of climb speed.

VY Best rate of climb speed on all engines.

VYSE Best engine-out rate of climb speed. Sometimes V%SE.

VZRC Zero rate of climb speed (on one engine, where drag of inoperative engine reduces climb gradient to zero).

variable geometry Capable of grossly changing shape in flight, especially by varying sweep of wings.

variable pitch Propeller with its blades held in rotary bearings in the hub, so that pitch (of all blades in unison) can be altered in flight. See constant speed: compare ground- and flight-adjustable pitch.

VC Vickers Commercial.

VDU Video (or visual) display unit.

vectored Capable of being pointed in different directions.

vertrep Vertical replenishment.

VFR Visual flight rules.

V-G Variable Geometry (which see).

VHF Very high frequency.

VIP Very Important Person.

VLF Very low frequency (area-coverage navaid/radio transmission band).

VMS Vehicle management system.

VOR VHF omnidirectional range (network of VHF radio beacons each providing to/from bearing).

vortex generators Small blades attached to wing and tail surfaces to energise local airflow and improve control.

vortillon Short-chord fence (particularly on MD-80 series) ahead of and below leading-edge.

VSI Vertical speed (climb/descent) indicator.

V/STOL Vertical/short take-off and landing.

VTA Voenno-Transportnaya Aviatsiya.

VTO Vertical Take-Off.

VVS Voenno-Vozdushnye Sili (Russian air force).



washout Inbuilt twist of wing or rotor blade reducing angle of incidence towards the tip.

watt SI unit of power, equal to 1 Js-1 (one Joule per second).

WCMD Wind-Corrected Munition Dispenser, being an add-on to the US series of CBU-78/B, CBU-87/B CEM and CBU-98/ Gator cluster munitions.

WDNS Weapon delivery and navigation system.

wet Housing fuel; wet wing often has extra connotation of integral tankage. Wet pylon can accommodate external fuel tank.

wheelbase Minimum distance from nosewheel or tailwheel (centre of contact area) to line joining mainwheels (centres of contact areas).

wide-body Passenger aircraft with cabin wide enough to have two longitudinal aisles between seats.

wing area Total projected area of clean wing (no projecting flaps, slats and so on) including all control surfaces and area of fuselage bounded by leading- and trailing-edges projected to centreline (inapplicable to slender-delta aircraft with extremely large leading-edge sweep angle).

wing loading Aircraft weight (usually MTOW) divided by wing area.

winglet Small auxiliary aerofoil, usually sharply upturned and often sweptback, at tip of wing.

WSO Weapon(s) system(s) officer.

WVR Within Visual Range.



X US designation prefix for experimental aircraft.



Y US designation prefix for developmental aircraft.

yoke Pilot's flight control interface for pitch and roll axes in the form of a stick (control column) to the top of which is laterally pivoted a pair of handgrips in the form of a Y.



ZAO Zakrytoe Aktsionernoye Obshchestvo (Russian company constitution).

zero-fuel weight MTOW minus usable fuel and other consumables, in most aircraft imposing severest stress on wing and defining limit on payload.

zero/zero seat Ejection seat designed for use even at zero speed on ground.

ZFW Zero-fuel weight.