F Fahrenheit
FAA Federal Aviation Administration (US)
also:   Fleet Air Arm (UK)
FAC Forward air control(ler)
FADEC Full authority digital engine control
FAE Fuel-air explosive
FAI Fédération Aéronautique Internationale
FANS Future Air Navigation System
FAR Federal aviation regulations (US)
FARP Forward arming and refueling point
also:   Forward area rearm/refuel point
FBL re: Fly by light
FBW re: Fly by wire
FCR Fire control radar
FCS Flight control system
FDO Flight deck officer (on aircraft carrier)
FDR Flight data recorder
FDS Flight director system
feathering Alignment of propeller blades with airstream to prevent windmilling and minimise drag with engine shut-down
FEBA Forward edge of battle area
fence Wing surface projection, parallel to chord, to prevent spanwise airflow
fenestrom Tail rotor for helicopters, consisting of many narrow blades in a short duct
ferry range Maximum safe range with no payload
FEWSG Fleet Electronic Warfare Support Group (USN)
FF First flight
FFAR Folding fin aircraft rocket
also:   Free flight aircraft rocket
FFOS Forward flying observation station
FG Fighter Group (USAF)
FGA Fighter Ground attack (UK)
FGR Fighter Ground attack Reconnaissance (UK)
field length Distance needed for take-off and/or landing; varies upon circumstances
fine pitch Propeller pitch most suitable for take-off and low-speed flight
FIR Flight Information Region
FIRAMS Flight incidence recorder and aircraft monitoring system
fire-and-forget missile A missile with self-homing capability
firewall Fire-resistant bulkhead seperating powerplant from rest of aircraft
fixed pitch Propeller with blades fixed immovably to hub
FL Flight Level; expressed in hunderds of feet: FL175 is 17500ft
flameout Discontinuation of combustion in gas turbine not caused by fuel shut-off
flap Part of trailing or leading edge of wing which can be moved to alter lift and drag characteristics during low-speed flight
flaperon Trailing edge control surface combining functions of flap and aileron
flare A source of heat energy used to divert infra-red (heat-seeking) homing missiles
flat-rated Engine restricted in output at s/l but able to give constant power at higher ambient temperatures and/or higher altitude
FLCC Flight control computer
FLCS Flight control system
flight envelope The design limits (speed, altitude, G-forces etc) of the aircrafts' performance
FLIR Forward looking infra-red
flutter High frequency oscillation caused by interaction of aeroelastic and aerodynamic forces
fly by light Fibre-optically signalled flight control system
fly by wire Electrically-signalled flight control system
FM Frequency modulation
FMC Flight management computer
FMCS Flight management computer system
FMD Flight management display
FMS Flight management system
also:   Foreign military sales (US)
FOB Forward operating base
FOC Full operational capability
FOD Foreign object damage
FOL Forward operating location
footprint re: noise footprint
foreplanes Canard surfaces providing the primary pitch control
FOT&E Follow-on test and evaluation
FOV Field of view
Fowler flap Trailing edge flap which moves rearwards first, then deflects downwards
fpm Feet per minute; standard measure to express climb or descent speed of an aircraft
FR Flight refueling
free turbine Turbine which drives the output shaft but is mechanically independent of the compressor
frequency agile Automatically switching over a range of frequencies to minimise chance of  eavesdropping
FRS Fleet Replenishment Squadron (USN)
also:   Fighter Reconnaissance Strike (UK)
FS Fighter Squadron (USAF)
FSAT Full-scale aerial target
FSD Full scale development
FSED Full scale engineering development
FSS Flight Screening Squadron (USAF)
FSW Forward swept wing
ft Foot (= 12 inch; = 30.5 cm)
FTS Flying Training Squadron (USAF)
also:   Flying Training School (RAF)
FTW Flying Training Wing (USAF)
FW Fighter Wing (USAF)
FY Fiscal Year (US: October 1 to September 30; FY 2006 starts in October 2005)
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