The Aviation Dictionary

ABSOLUTE CEILING - The maximum altitude above sea level at which a heavier-than-air craft can be maintained in level flight.

ACLS - (I) Air cushion landing system, or (II) automatic carrier landing system.

ADF - Automatic Direction Finding; utilizing an automated radio direction finding (RDF) technique.

AEROBATICS - Voluntary maneuvers, initiated by a pilot, other than those for conventional flight.

AERODROME - An area set aside for the operation of aircraft.

AERODYNAMICS - The branch of fluid mechanics dealing with air (gaseous) motion, and the reactions of a body moving within that air.

AEROFOIL (AIRFOIL) - A body or structure shaped to obtain an aerodynamic reaction when travelling through the air.

AERONAUTICS - Concerned with flight within the Earth's atmosphere.

AEROPLANE (AIRPLANE)- Meaning in modern usage a heavier-than-air powered craft.

AEROSTAT - A lighter-than-air craft.

AEW - Airborne early warning; aircraft equipped to give maximum advance warning of approaching hostile aircraft.

AFCS - Automatic flight control system.

AFTERBURNER - Thrust augmentation feature of a gas turbine engine.

Al- Airborne interception; radar device carried by military aircraft to aid location and interception of hostile aircraft.

AILERONS - Movable control surfaces, usually mounted in the trailing-edge of a wing adjacent to the wingtips, to control an aircraft's rolling movements.

AIRBRAKE- A drag-inducing surface which can be deployed in flight, perhaps for speed reducing or limiting, but see also spoilers.

AIRFIELD- More modern term for aerodrome, and applying more particularly to one used by military aircraft.

AIRFLOW- The movement of air about a body (aircraft) in motion.

AIRFOIL (AEROFOIL)- A structure shaped to obtain an aerodynamic reaction in the air, thus affecting the performance of the aircraft.

AIRFRAME - An aircraft's structure, without power plant and systems.

AIRPLANE (AEROPLANE) - Meaning in modern usage a heavier-than-air powered craft, as opposed to a balloon or glider.

AIRPORT - More modern term for aerodrome, and applying more particularly to one used for civil transport operations.

AIRSCREW - Now little-used word for propeller; believed to have originated to provide distinction from ship's propeller.

AIRSHIP - A powered lighter-than-air craft.

AIRSPEED - The speed of an aircraft through the air, relative to the air mass in which it is moving.

AIRSTRIP - A natural surface used for the operation of aircraft, often in an unimproved state.

ALTIMETER - An instrument, most usually an aneroid barometer, calibrated in meters and/or feet, to indicate an aircraft's height.

ALTITUDE - Height

AMPHIBIAN - An aircraft able to operate from both land and water.

ANGLE OF ATTACK - Angle at which the air-stream meets an aerofoil surface.

ANGLE OF INCIDENCE - Angle at which an airfoil surface is normally set in relation to the fore and aft axis of the airframe structure.

ANHEDRAL - Angle which the spanwise axis of an airfoil makes to the fuselage when the wing or tailplane tip is lower than its root attachment point.

APU - Auxiliary power unit. Usually small engine carried on board an aircraft to provide an independent power source for such services as electrics, hydraulics, pneumatics, ventilation, and air conditioning, both on the ground and in the air if needed.

ASI - Air speed indicator.

ASPECT RATIO - Ratio of the span to the chord of an airfoil. Hence, a high aspect ratio wing has great span and narrow chord, and vice versa.

ASTRODOME - Transparent dome, usually on dorsal surface of fuselage, to permit celestial navigation by traditional means.

ASW - Antsubmarine warfare.

ATC - Air traffic control.

AUTOGYRO - An aircraft with an unpowered rotary wing, which autorotates as the machine is propelled through the air by a conventional power plant. "Autogiro" is the trade name for autogyros developed by Juan de la Cierva.

AUTOMATIC PILOT (AUTOPILOT) - A gyroscopically stabilized system maintaining an aircraft in level flight at predetermined heading and altitude.

AUTOROTATION - Automatic rotation of a rotary wing due to forward, or downward, movement of an autogyro

AWACS - Airborne warning and control system; an advanced AEW aircraft, with additional facilities for deployment and control of defence, interception, and counter-strike forces.

BALLISTIC MISSILE - A weapon which, in the terminal and unpowered stage of its flight, becomes a free-falling body subject to ballistic reactions.

BALLOON - An unpowered lighter-than-air craft, its direction of flight imposed by ambient airstreams.

BIPLANE - A fixed-wing aircraft with two sets of wings mounted, generally, one above the other.

BLEED AIR - Hot air, at high pressure, taken usually from the bypass section of a gas turbine engine, for heating, de-icing and other useful work.

BLOWN FLAPS - Aerodynamic surface over which bleed air is discharged at high speed to prevent breakaway of the normal airflow.

BOUNDARY LAYER - Thin stratum of air nearest to an aircraft's external surface structure.

BOX KITE - Form of kite devised by Australian Lawrence Hargrave, used by many early constructors to provide rigid biplane structures.

BUFFET - Irregular, often violent, oscillations of an aircraft's structure, caused by turbulent airflow or conditions of compressibility.

CAA - Civil Aviation Administration (U.K.).

CAB - Civil Aeronautics Board (U.S.A.).

CABIN - Enclosed compartment for crew and/or passengers in an aircraft.

CAMBER - The curvature, convex or concave, of an airfoil surface.

CANARD - Describes an aircraft which flies tail first, with its main lift surface at the aft end of its structure.

CANTILEVER - A beam, or other structure, supported at one end only, and without external bracing.

CATHEDRAL - Early word to describe anhedral, or negative dihedral.

CEILING - Normal maximum operating altitude of an aircraft.

CENTER OF GRAVITY - (CQ), the point on an aircraft's structure where the total combined weight forces act.

CENTER-SECTION - The central panel, or section, of an aircraft's wing.

CHORD - The distance measured from the leading-to trailing-edge of an airfoil.

COCKPIT - Compartment, originally open to the air, for accommodation of pilot'and crew/passengers. Nowadays used informally by laymen to describe the forward part of the cabin, especially of an airliner, which is off-limits to passengers, and properlv called flight deck.

COIN - Counter-insurgency aircraft.

COLLECTIVE PITCH CONTROL - Used to change simultaneously the pitch of all of a helicopter rotor's blades to permit ascent or descent.

CONSTANT-SPEED PROPELLER - One which governs an engine at its optimum speed, the blade pitch being increased or decreased automatically to achieve this result.

COWLING - The name of the fairing which, usually, encloses an engine.

CYCLIC PITCH CONTROL - Means of changing the pitch of a rotor's blades progressively, to provide a horizontal thrust component for flight in any horizontal direction.

DELTA WING - When viewed in plan has the shape of an isosceles triangle; the apex leads, the wing trailing-edge forming the base of the triangle.

DERATED - An engine which is restricted to a cower output below its potential maximum.

DIHEDRAL - Angle which the spanwise axis of an aerofoil makes to the fuselage when the wing or tailplane tip is higher than its root attachment point (positive dihedral).

DIVE BRAKE - Drag-inducing surface deployed in a dive to maintain speed below structural limitations, or improve controllability (see airbrake).

DORSAL - Relating to the upper surface of an aircraft's fuselage.

DRAG - A force exerted on a moving body in a direction opposite to its direction of motion.

DRAG CHUTE - A heavy-duty parachute attached to an aircraft's structure which can be used to reduce its landing run.

DRONE - A pilotless aircraft, usually following a predetermined or programmed set of maneuvers. See also RPV.

DROP TANK - An externally carried auxiliary tank, usually to contain fuel, which may be jettisoned if necessary.

ECM - Electronic counter-measures; airborne equipment to reduce the effectiveness of an enemy's radar or other devices which generate electromagnetic radiations.

ELEVATOR - Movable control surface, attached to the trailing-edge of an aircraft's tailplane (stabilizer) to controll pitching movements.

ELEVONS - Movable control surfaces which act collectively as elevators, but differentially as ailerons.

ELT - Emergency locator transmitter; emits a homing signal from a crashed aircraft to simplify location for rescue services.

ENVELOPE - Container, usually flexible, or the lifting gas or hot air of an airship or balloon.

FAA - Federal Aviation Administration.

FAI - Federation Aeronautique Internationale.

FAR - Federal Aviation Regulations.

FIN - A fixed vertical aerofoil surface, usually a dorsal component of the tail unit, to provide stability in yaw.

FIRING - An addition to an aircraft's basic structure which is intended primarily to reduce drag.

FLAP - Most usually awing trailing-edge movable surface which can be deployed partially to increase lift, or completely to increase drag.

FLAT-FOUR - Characteristic description of a horizontally opposed four-cylinder engine; hence flat-twin, flat-six.

FLIGHT DECK - (I) Separate crew compartment of a cabin aircraft, or (II) the operational deck of an aircraft carrier.

FLIGHT SIMULATOR - A ground-based training device to permit the practice of flight operations; often specific to a particular aircraft for detailed training.

FLOATPLANE - Aircraft which is supported on the water by floats; more usually termed a seaplane

FLUTTER - Unstable oscillation of an airfoil surface.

FLYING-BOAT - A heavier-than-air craft which is supported on the water by its water-tight fuselage.

FLYING WIRES (LIFT WIRES) - External bracing wires, usually of streamline section, which carry the weight of the fuselage in flight.

FULLY-FEATHERING PROPELLER - One in which the blades can be rotated so that the leading-edge of each faces the oncoming airstream. This reduces drag if an engine has to be stopped in flight.

FUSELAGE - The body structure of an aircraft.

GLIDER - A heavier-than-air, fixed wing, unpowered aircraft for gliding or soaring flight.

HARDPOINT - A strengthened section of the under-wing or fuselage, intended for the carriage of external weapons or stores, usually on pylons.

HELICOPTER - A heavier-than-air craft with a powered rotary wing.

HELIUM - A non-inflammable lifting gas tor lighter-than-air craft.

HIGH-WING MONOPLANE - An aircraft which has its single wing mounted high on the fuselage.

HULL - The water-tight fuselage or body of a flying-boat.

HYDRO-AEROPLANE - Early term for an aircraft which could operate from water.

HYDROGEN - The lightest known lifting gas, used to inflate balloons and airships, unfortunately highly inflammable.

IATA - International Air Transport Association.

ICAO - International Civil Aviation Organization.

ICING - Condition arising when atmospheric moisture freezes on the external surfaces of an aircraft.

IFF - Identification, friend or foe; an electronic device to interrogate approaching aircraft.

IFR - Instrument Flight Rules; i.e. flight by reference to on-board instruments under conditions of poor visibility or darkness.

ILS - Instrument Landing System.

IN-LINE ENGINE - Engine in which the cylinders are one behind another, in straight lines.

INS - Inertial navigation system, in which highly sensitive accelerometers record, via a computer, the complex accelerations of an aircraft about its three axes, thus integrating its linear displacement from the beginning of a selected course and pinpointing the aircraft's position at all times.

ISA - Agreed International Standard Atmosphere (1013.2 millibars at 15'C) to permit accurate comparison of aircraft performance figures.

JATO - Jet-assisted take-off, utilising solid or liquid fuel rockets to augment the take-off power of an aircraft's engines. See also RATO.

KINETIC HEATING - Heating of an aircraft's structure as a result of air friction.

KITE - Usually tethered heavier-than-air craft, sustained in the air by its airfoil surfaces being inclined to the wind to generate lift.

LANDING WEIGHT - Normal maximum weight at which an aircraft is permitted to land.

LANDING WIRES - External bracing wires, usually of streamline section, which support the wings when the aircraft is on the ground.

LANDPLANE - A heavier-than-air craft which is equipped to operate from land surfaces only.

LBA - Luftfahrtbundesamt; the Federal German Civil Aviation Authority.

LEADING-EDGE - The edge of an airfoil which first meets the airstream in normal flight.

LIFT - The force generated by an airfoil section, acting at right angles to the airstream flowing past it

LORAN - A long-range radio-based navigation aid.

LOW-WING MONOPLANE - An aircraft which has its single wing mounted low on the fuselage.

MACH NUMBER - Named after the Austrian physicist Ernst Mach, a means of recording the speed of a body as a ratio of the speed of sound in the same ambient conditions. The speed of sound in dry air at 32"F (CTC) is approximately 1087ft/sec (331m/sec); 741mph (1193km/h). Hence Mach 0.8 represents eight-tenths of the speed of sound.

MAD - Magnetic anomaly detector carried, for example, by maritime reconnaissance aircraft to locate a submarine beneath the surface of the sea.

MID-WING MONOPLANE - An aircraft which has its single wing mounted in a mid-position on the fuselage.

MONOCOQUE - Structure in which the outer skin carries the primary stresses, and is free of internal bracing.

MONOPLANE - A fixed-wing aircraft with a single set of wings, i.e. one wing on each side.

NACA - National Advisory Committee for Aeronautics. Now NASA.

NAF - Naval Aircraft Factory (U.S.).

NASA - National Aeronautics and Space Administration.

NATO - North Atlantic Treaty Organization.

ORNITHOPTER - Name for a flapping-wing aircraft. Only model ornithopters have flown to date.

PARACHUTE - Collapsible device which, when deployed, will retard the rate of descent of a body falling through the air. Used originally as a safety device, has been adopted for dropping troops, supplies, equipment, etc.

PARASOL MONOPLANE - A fixed-wing aircraft which has its single wing strut-mounted above the fuselage.

PAYLOAD - The useful load of an aircraft cargo, passengers; in a military aircraft, its weapon load.

PITCH - The angle of incidence at which a propeller blade or rotor blade is set.

PORT - Left-hand side when facing forward.

PRESSURIZATION - Artificially increased pressure in an aircraft to compensate for the reduced external pressure as the aircraft gains altitude.

PROPELLER - Rotating blades of aerofoil section, engine driven, each of which reacts as an aircraft's wing, generating low-pressure in front and higher behind, thus pulling the aircraft forward.

PROTOTYPE - The first airworthy example of a new aircraft design or variant.

PUSHER PROPELLER - Inaccurate but accepted description of propeller mounted behind an engine. It acts aerodynamically as described under propeller, and is thus a tractor in action.

PYLON - Structure attached to wing or airframe to carry load, e.g. engines or weapons.

RADAR - Beamed and directed radio waves used for location and detection, as well as for navigational purposes.

RADIAL ENGINE - One in which the cylinders are mounted equidistant and circumferentially around a circular crankcase. Cylinders and crankcase are fixed, and the crankshaft rotates.

RAE - Royal Aircraft Establishment, formerly Royal Aircraft Factory.

RAF - Royal Aircraft Factory.

RAI - Registro Aeronautico Italiano.

RAMJET ENGINE - An aerodynamic duct in which fuel is burned to produce a high-velocity propulsive jet. It needs to be accelerated to high speed before it can become operative.

RATO - Rocket-assisted take-off virtually the same as JATO.

RDF - Radio direction finding; using the transmission from two or more stations to fix position of an aircraft by its bearing in relation to each.

ROCKET ENGINE - One burning liquid or solid fuel and carrying Its own oxidizer, enabling combustion to continue outside of the earth's atmosphere.

ROLL - Movement of an aircraft about its longitudinal axis, representing a wing-over rolling action.

ROTARY ENGINE - Cylinders disposed as for radial engine, but in this case the crankshaft is fixed, and cylinders and crankcase rotate around it.

ROTOR - The rotating-wing assembly of an autogyro or helicopter, comprising the rotor hub and rotor blades.

RPV - Remotely piloted vehicles, directed usually by radio by a pilot in another aircraft or based on the ground.

RUDDER - Movable control surface, attached to trailing-edge of fin, to control aircraft movement in yaw.

SAILPLANE - An unpowered heavier-than-air craft designed primarily for soaring flight.

SEAPLANE - A heavier-than-air craft which operates from water, and is supported on the surface of the water by floats.

SEMI-MONOCOQUE - An aircraft structure in which the outer skin is inadequate to carry the primary stresses, and is reinforced by frames, formers and longerons.

SERVICE CEILING - Normally height at which an aircraft can maintain a maximum rate of climb of 100 ft (30 m) /min.

SGAC - Secretariat Generate A I'Aviation Civile.

SKIN - The external covering of an aircraft's basic inner structure.

SLAT - Auxiliary airfoil surface, mounted forward of a main airfoil, to maintain a smooth airflow over the main airfoil at high angles of attack.

SLOT - The gap between the slat and leading-edge of the main airfoil, which splits the airflow and maintains a smooth flow over the main airfoil upper surface.

SPAN - The distance from tip to tip of the wing or tailplane.

SPAR - A primary structural member of an airfoil surface, from which ribs or frames are mounted to form the desired airfoil contours.

SPINNER - A streamlined fairing over a propeller hub.

SPOILERS - Drag-inducing surfaces which can be deployed differentially for lateral control, or simultaneously for lift dumping to improve the effectiveness of landing brakes.

STALL - Condition which arises when the smooth airflow over a wing's upper surface breaks down and its lift is destroyed.

STARBOARD - Right-hand side when facing forward.

STOL - Short take-off and landing capability.

STREAMLINE - To shape a structure so that it will cause the minimum aerodynamic drag.

STRUT- Solid or tubular member, usually streamlined, used for bracing, as, for example, between the two wings of a biplane. Can be required to carry tension or compression loads.

SUBSONIC - Flight at a speed below that of sound.

SUPERCHARGER - A form of compressor, often turbine-driven, to force more fuel/air mixture into the cylinders of a piston-engine than can be induced by the pistons at ambient atmospheric pressure.

SUPERSONIC - Speed in excess of that of sound.

SV-VS - Soviet Military Aviation Forces (Sovietskiye Voenno-Vozdushnye Sily).

SWEPT WING - Wing of which the angle between the wing leading-edge and the centre line of the rear fuselage is less than 90 degrees.

TABS - Small auxiliary control surfaces which can be adjusted to offset aerodynamic loads imposed on main control surfaces.

TAILPLANE (STABILIZER) - Primary horizontal airfoil surface of tail unit. Can be fixed, or may have variable incidence, and its purpose is to provide longitudinal stability.

TAKE-OFF WEIGHT - Maximum allowable weight of an aircraft at the beginning of its take-off run.

THRUST - Force which propels an aircraft through the air; generated by conventional propeller or the jet efflux of a turbine engine.

TRACTOR PROPELLER - Propeller mounted forward of the engine. (See propeller.)

TRAILING-EDGE - The rear edge of an aerofoil.

TRIPLANE - Fixed-wing aircraft with three sets of wings, mounted one above another.

TURBOFAN - Gas turbine engine with large diameter forward fan. Air is dueled from the tips of these fan blades and by-passed around the engine, and added to the normal jet efflux to provide high propulsive efficiency.

TURBOJET - Gas turbine engine in its simplest form, producing a high velocity jet efflux.

TURBOPROP - Gas turbine engine in which maximum energy is taken from the turbine to drive a reduction gear and conventional propeller.

TURBOSHAFT - Gas turbine engine in which maximum energy is taken from the turbine to drive a high speed shaft. It can be used to drive a helicopter's rotor or any other form of machinery.

VARIABLE-GEOMETRY WING - Wings which, fully extended, give the best low-speed performance for take-off and landing, and can be swept in flight to optimum positions for best cruising and high-speed flight performance.

VARIABLE-PITCH PROPELLER - Usually a propeller in which the blades can be set to two positions a fine-pitch setting for take-off and landing, and a coarse-pitch setting for economic cruise performance.

VEE-ENGINE - One with two banks of in-line cylinders mounted with an angular separation on a common crankcase.

VENTRAL - Relating to the under-surface of an aircraft's fuselage.

VFR - Visual Flight Rules; i.e. flight under conditions of good external visibility, without dependence on aircraft instruments.

VSTOL - Vertical or short take-off and landing.

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

VTOL - Vertical take-off and landing capability.

WING-LOADING - The gross take-off weight of an aircraft divided by its wing area. A Boeing 747, for example, can have a maximum wing loading of 149Ib/sq ft (727.8kg/m2); a high-performance sailplane, such as the Scheibe Bergfaike, can be as low as 6.02Ib/sq ft (29.4kg/m2).

WING WARPING - Method of lateral control adopted by Wright brothers and many early builders/designers, in which a flexible wing is twisted (warped) to provide roll control as with ailerons.

YAW - Movement of an aircraft about its vertical axis, representing movement of its tail unit to port or starboard, to change the aircraft's heading.