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Glossary — 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).