| F | Fahrenheit |
| F | farad |
| F | floating point |
| F | force |
| F&A | fabrication and assembly |
| F&D | fill and drain |
| F&E | facility and environment |
| F&IE | facilities and industrial engineering |
| F&M | force and moment |
| F&P | fluids and propulsion |
| F&PC | finance and program control |
| F-F | face-to-face |
| F/A | fabrication and assembly |
| F/A | failure analysis |
| F/A | fuel-to-air ratio |
| F/C | fire control |
| F/C | fit check |
| F/C | flight control |
| F/C | flow control |
| F/C | fuel cell |
| F/D | face of drawing |
| F/D | field of drawing |
| F/D | fill/drain |
| F/E | full/empty |
| F/F | fill/full |
| F/O | fuel oxidizer |
| F/R | flared rudder |
| FA | factor analysis |
| FA | failure analysis |
| FA | feedback analysis |
| FA | final approach |
| FA | final assembly |
| FA | flight acceptance |
| FA | flight aft |
| FA | flight-critical aft |
| FA | fully automatic |
| FA/COSI | final assembly closeout systems installation |
| FA< | first approach and landing test |
| FAA | Federal Aviation Administration |
| FAA | false alarm avoidance |
| FAB | flight assignment baseline |
| FABU | fuel additive blender unit |
| FACC | Ford Aerospace and Communications Corporation |
| FACI | first-article configuration inspection |
| FACO | fabrication and acceptance checkout |
| FACO | factory acceptance checkout |
| FACO | factory assembly and checkout |
| FACO | final assembly checkout |
| FACR | first-article configuration review |
| FACS | finance and control system |
| FACT | first-address control table |
| FACT | flexible automatic circuit tester |
| FACT | flight acceptance composite test |
| FACTS | FDF automated control and tracking system |
| FAD | final approach display |
| FAD | flight assessment delta |
| FAE | final approach equipment |
| FAF | final assembly fixture |
| FAF | first aerodynamic flight |
| FAFS | Falcon Air Force Station |
| FAIR | fabrication, assembly, and inspection record |
| FAIR | fly-along infrared |
| FAL | facility area layout |
| FAL | first approach and landing |
| FAME | formatting and multiplexing equipment |
| FAMOS | flight acceleration monitor system |
| FAMS | FDF automated monitoring system |
| FAMU | fuel additive moisture unit |
| FAO | flight activities officer |
| FAP | FORTRAN assembly program |
| FAP | final approach plane |
| FAPE | Florida Association of Professional Employees |
| FAR | Federal Aviation regulation |
| FAR | failure analysis report |
| FAR | federal acquisition regulation |
| FAR | final acceptance review |
| FAR | flight acceptance review |
| FAR | flight analysis review |
| FAS | flight analysis system |
| FAS | forward acquisition sensor |
| FASCOS | flight acceleration safety cutoff system |
| FAT | factory acceptance test (some subcontractors) |
| FAT | final acceptance test (Rockwell) |
| FAT | flight attitude table |
| FAWG | Flight Assignment Working Group |
| FB | feedback |
| FB | field bulletin |
| FB | final braking |
| FB | flat bar |
| FB | fleet broadcast |
| FBAS | fixed-base aft station |
| FBB | flyback booster |
| FBC | fluidized-bed combustion |
| FBCS | fixed-base crew station (SMS) |
| FBM | fleet ballistic missile |
| FBV | field-base visit |
| FBV | fuel bleed valve |
| FC | facility control |
| FC | ferrite core |
| FC | fire control |
| FC | fit check |
| FC | flight computer |
| FC | flight control |
| FC | flight critical |
| FC | fuel cell |
| FCA | field change analysis |
| FCA | flow control assembly |
| FCA | forward controller assembly |
| FCA | frequency control analysis |
| FCA | functional compatibility analysis |
| FCA | functional configuration audit |
| FCAF | Flight Crew Accommodation Facility |
| FCAP | flight control applications program |
| FCB | Fracture Control Board |
| FCC | Federal Communications Commission |
| FCC | flat conductor cable |
| FCCP | firm contract cost proposal |
| FCD | Flight Control Division (NASA) |
| FCDB | flight control data bus |
| FCDC | flexible confined detonating cord |
| FCDR | final critical design review |
| FCE | fast-cycle executive |
| FCE | flight control equipment |
| FCE | flight crew equipment |
| FCEF | Flight Crew Equipment Facility |
| FCEI | facility contract end item |
| FCEI | facility contractor end item |
| FCF | first captive flight |
| FCF | functional check flight |
| FCH | Flight Controller's Handbook |
| FCHL | Flight Control Hydraulics Laboratory |
| FCI | flight control indicator |
| FCI | flight crew integration |
| FCI | functional configuration identification |
| FCIM | flight control interface module |
| FCIP | flight cargo implementation plan |
| FCITE | FCI time element |
| FCL | Freon coolant line |
| FCL | Freon coolant loop |
| FCL | feeder control logic |
| FCL | fluid coolant loop |
| FCM | flow control module |
| FCMC | facility control and monitor console |
| FCMU | foot-controlled maneuvering unit |
| FCO | field change order |
| FCO | final checkout |
| FCO | flight crew operations |
| FCO | functional checkout |
| FCOB | Flight Crew Operations Branch (NASA) |
| FCOD | Flight Crew Operations Directorate |
| FCOH | Flight Controller's Operational Handbook |
| FCOS | flight computer operating system |
| FCOS | flight control operating system |
| FCOS | flight control operational software |
| FCP | Failure Correction Panel |
| FCP | firm cost proposal |
| FCP | flight correction proposal |
| FCP | fuel cell power plant |
| FCP | fuel cell propellant |
| FCPS | fuel cell power system (subsystem) |
| FCR | facility change request |
| FCR | final configuration review |
| FCR | flight configuration review |
| FCR | flight control room |
| FCRA | fecal collection receptacle assembly |
| FCRT | flight display CRT |
| FCS | fecal containment system |
| FCS | federal communications system |
| FCS | fire control system |
| FCS | flight control simulator |
| FCS | flight control system |
| FCS | flight crew system |
| FCS | front crew system |
| FCSD | Flight Crew Support Division (JSC) |
| FCSM | flight combustion stability monitor |
| FCSS | fuel cell servicing system |
| FCSTF | Fuel Cell System Test Facility |
| FCT | filament center tap |
| FCT | flight control team |
| FCT | flight controller trainer |
| FCT | flight crew trainer |
| FCT | fuel cell test |
| FCTB | Flight Crew Training Building |
| FCTF | Fuel Cell Test Facility |
| FCTR | flight controller training room |
| FCTS | flight crew trainer simulator |
| FCU | fluid checkout unit |
| FCV | flow control valve |
| FCW | format control word |
| FD | fault detection |
| FD | flight day |
| FD | flight director |
| FD | freeze-dried |
| FD | function designator |
| FD | functional designator |
| FD/FI | fault detection/fault isolation |
| FDA | fault detection and annunciation |
| FDA | flight deck assembly |
| FDAI | flight director attitude indicator |
| FDB | Fahrenheit dry bulb |
| FDB | facility data base |
| FDCF | Flight Design Control Facility |
| FDDB | function designator data base |
| FDDI | fiber distributed data interface |
| FDF | first drop flight |
| FDF | flight data file |
| FDI | failure detector indicator |
| FDI | fault detection and identification |
| FDI | fault detection and isolation |
| FDI | flight detection and isolation |
| FDI | flight director instrument |
| FDIIR | fault detection, isolation, identification, and |
| FDIR | fault detection, identification, and recovery |
| FDIR | fault detection, isolation, and recovery |
| FDIR | fault detection/isolation and reconfiguration |
| FDK | flight display keyboard |
| FDL | flight director loop |
| FDLC | final design load cycle |
| FDM | flight data manager |
| FDM | flight design manager |
| FDM | frequency data multiplexer |
| FDM | frequency division multiplexer |
| FDM | frequency domain multiplexer |
| FDMA | frequency division multiple access |
| FDO | Flight Director's Office |
| FDO | fee determination official |
| FDO | flight dynamics officer |
| FDOR | flight design operations review |
| FDP | Flight Design Panel |
| FDR | final design review |
| FDR | flight definition requirement |
| FDR | functional design review |
| FDRD | flight definition and requirements directive |
| FDRD | flight definition and requirements document |
| FDRD | flight determination and requirements directive |
| FDRI | flight director rate indicator |
| FDS | failure dynamics software |
| FDS | fire detection and suppression |
| FDS | flight design and scheduling |
| FDS | flight design system |
| FDS | flight dynamics simulator |
| FDS | flight dynamics software |
| FDS | flight dynamics support |
| FDS | flight dynamics system |
| FDS | fluid distribution system |
| FDS | functional design specification |
| FDSC | flight dynamics simulation complex |
| FDSC | flight dynamics situation complex |
| FDSCU | fluid distribution system control unit |
| FDSR | final design status review |
| FDT | full-duplex teletype |
| FDU | fluid distribution unit |
| FDX | simultaneous, two-way, full-duplex channel |
| FE | flight execution |
| FE | flight executive |
| FE | flight experiment |
| FE | force execution |
| FEA | failure effects analysis |
| FEA | flight experiment apparatus |
| FEA | fluids experiment apparatus |
| FEAT | final engineering acceptance test |
| FEB | forward equipment bay |
| FEB | fourth entry battery |
| FEB | functional electronic block |
| FEC | field engineering change |
| FEC | forward events controller |
| FECR | final experiment concept review |
| FED | flight events demonstration |
| FEDB | flight execution data base |
| FEDP | facility and equipment design plan |
| FEE | failure effects evaluation |
| FEID | flight equipment interface design |
| FEID | flight equipment interface device |
| FEID | functional engineering interface device |
| FEL | first-element launch |
| FEL | free-electron laser |
| FEM | finite-element method |
| FEM | finite-element model |
| FEMCPL | facilities and environmental measurement component parts |
| FEO | field engineering order |
| FEP | fluorinated ethylene-propylene |
| FEP | front-end processor |
| FEPC | flight equipment processing contractor |
| FERD | facility and equipment requirements document |
| FES | flash evaporator system |
| FES | flight element set |
| FESL | failure effects summary list |
| FESP | flight execution support plan |
| FET | field effect transistor |
| FET | flight elapsed time |
| FEWG | Flight Evaluation Working Group |
| FF | flight forward |
| FF | flight-critical forward |
| FF | flip-flop |
| FF | forecasting funding |
| FF | forward fuselage |
| FF | free flight |
| FF | free flyer |
| FF | full field |
| FF | full functional |
| FFBD | functional flow block diagram |
| FFC | final flight certification |
| FFC | first-flight capability |
| FFD | fixed-format display |
| FFD | functional flow diagram |
| FFF | final factory functional |
| FFM | free-flying (experiment) module |
| FFP | firm fixed price |
| FFP | firmed fixed price |
| FFR | flight feasibility review |
| FFRR | first flight readiness review |
| FFSAC | field functional systems assembly and checkout |
| FFT | factory functional test |
| FFT | fast Fourier transform |
| FFT | frame format table |
| FFTO | free-flying teleoperator |
| FH | flex hose |
| FHC | flight half-coupling |
| FHD | fixed-head disk |
| FHF | first horizontal flight |
| FHO | failed hardover |
| FHP | fuel high pressure |
| FHS | forward heat shield |
| FHST | fixed-head star tracker |
| FI | fault identification |
| FI | fault isolation |
| FI | field intensity |
| FI | formal inspection |
| FIA | flight integration assessment |
| FIAB | Flight Integration Assessment Board |
| FIAR | failure investigation action report |
| FICA | Federal Insurance Contribution Act |
| FID | flight implementation directive |
| FIE | flight instrumentation engineer |
| FIFO | first in/first out (high-speed data buffer) |
| FIIG | federal item identification guide |
| FIIN | federal item identification number |
| FIIWG | Facility Integration and Installation Working Group |
| FILE | feature identification and location equipment |
| FIM | field instruction memorandum |
| FIMS | framework for integrated manufacturing system |
| FIO | furnished and installed by others |
| FIR | fuel indicator reading |
| FIRSSE | Far Infrared Sky Survey Experiment |
| FIS | facility interface sheet |
| FISA | facility inspection shakedown acceptance |
| FIST | final integrated system test |
| FIST | functional integrated system test |
| FIT | fault isolation test |
| FITH | fire in the hole |
| FIV | fuel isolation valve |
| FKB | flight display keyboard |
| FL | feed line |
| FL | flow line |
| FL | forward link |
| FLAG | flexible assignment generator |
| FLAGE | Flexible Lightweight Agile Guided Experiment |
| FLAIR | functional language articulated interactive resource |
| FLAPS | flight application software |
| FLC | Federal Library Committee |
| FLC | forward load control |
| FLCA | forward load controller assembly |
| FLIR | forward-looking infrared |
| FLLK | frustum-lifting lug kit |
| FLPS | flight load planning system |
| FLR | flight log recorder |
| FLSA | Fair Labor Standards Act |
| FLSC | flexible linear-shaped charge |
| FLTSATCOM | fleet satellite communications |
| FLW | Fellows (TACAN station) |
| FM | first mold |
| FM | flight model |
| FM | fluid module |
| FM | fracture mechanics |
| FM | frequency modulated |
| FM | frequency modulation |
| FM/CW | frequency-modulated continuous wave |
| FM/FM | frequency modulation/frequency multiplexing |
| FM/PM | frequency modulation/phase modulation |
| FMA | failure mode analysis |
| FMAD | fluid management and distribution |
| FMAHTS | flight manifest and hardware tracking system |
| FMAR | final mission analysis review |
| FMC | forward motor controller |
| FMCA | forward motor controller assembly |
| FMCF | first manned captive flight |
| FMCS | Federal Mediation and Conciliation Services |
| FMD | fixed-module drive |
| FMD&C | flight mechanics, dynamics, and control |
| FMDM | flexible multiplexer/demultiplexer |
| FMEA | failure mode and effects analysis |
| FMEC | forward master events controller |
| FMECA | failure modes and effects criticality analysis |
| FMECA | failure modes, effects, and criticality analysis |
| FMK | field modification kit |
| FML | fault message line |
| FML | final materials list |
| FMO | flight medical officer |
| FMOF | first manned operational flight |
| FMOF | first manned orbital flight |
| FMOFEV | first manned orbital flight with EVA |
| FMOFPL | first manned orbital flight with payload |
| FMP | facility management plan |
| FMPAC | fixed multipurpose application console |
| FMR | field modification request |
| FMR | function max rate |
| FMS | fluid management system |
| FMS | food management subsystem |
| FMS | forms management system |
| FMS | functional master schedule |
| FMSP | FM signal processor |
| FMSP | frequency modulation signal processor |
| FMT | flight management team |
| FMX | FM transmitter |
| FND | facility need date |
| FNOC | Fleet Numeric Oceanography Center (U.S. Navy) |
| FNOC | Fleet Numerical Oceanography Center |
| FNT | failure notification Telex |
| FO | fail operating |
| FO | fail operational |
| FO | fast operating |
| FO | fiber-optic |
| FO | flat oval |
| FO | functional objective |
| FO-FO-FS | fail operational/fail operational/fail safe |
| FO-FS | fail operational/fail safe |
| FOB | Flight Operations Building |
| FOB | fractional orbit bombardment |
| FOB | free on board |
| FOBS | fractional orbit bombing system |
| FOC | fleet operational capability |
| FOC | full operational capability |
| FOCR | final operational concept review |
| FOD | Flight Operations Directorate (JSC) |
| FODS | fiber-optic demonstration system |
| FOE | flight operations engineer |
| FOF | first operational flight |
| FOF | first orbital flight |
| FOF | flight operations facility |
| FOG | fiber-optic gyro |
| FOGM | fiber-optic guided missile |
| FOH | first-order hold |
| FOI | field operations installation |
| FOIH | Flight Operations Integration Handbook |
| FOM | field operations memorandum |
| FOM | figure of merit |
| FOMR | Flight Operations Management Room |
| FOP | Flight Operations Panel |
| FOP | facility operations plan |
| FOP | flight operations plan |
| FOP | follow-on production |
| FOPG | Flight Operations Planning Group |
| FOPP | follow-on parts production |
| FOPS | flight operations planning schedule |
| FOPSS | flight operation product scheduling system |
| FOR | field of regard |
| FOR | flight operations review |
| FORD | flight operations requirement document |
| FORTRAN | formula translation |
| FOS | flight operation security |
| FOS | flight operations support |
| FOSA | Flight Operations Support Annex |
| FOSDIC | film optical sensing device for input to computers |
| FOSMS | facility operation scheduling and monitoring system |
| FOSO | flight operations scheduling officer |
| FOSP | flight operations support personnel |
| FOST | flight operations support team |
| FOT | flight operation trainer |
| FOT | flight operations team |
| FOV | field of view |
| FOV | field of vision |
| FOV | first orbital vehicle |
| FOWG | Flight Operations Working Group |
| FP | fine pointer |
| FP | fine pointing |
| FP | fixed point |
| FP | fixed price |
| FP | flat panel |
| FP | flexible processor |
| FP | flight plan |
| FP | focal plane |
| FP | freezing point |
| FP | fuel pressure |
| FP | function path |
| FP | functional path |
| FPA | focal plane array |
| FPA | focal plane assembly |
| FPB | fuel preburner |
| FPBOV | fuel preburner and oxidizer valve |
| FPC | Federal Power Commission |
| FPC | fixed-price contractor |
| FPC | forward power controller |
| FPCA | forward power controller assembly |
| FPDE | focal plane drive electronics |
| FPE | functional program element |
| FPEG | fast-pulse electron gun |
| FPH | Flight Procedures Handbook |
| FPI | fixed-price incentive |
| FPI | fuel pressure indicator |
| FPIF | fixed-price incentive fee |
| FPIT | field preinstallation test |
| FPL | fetch pointer list |
| FPL | full power load |
| FPO | Future Projects Office (MSFC) |
| FPOV | fuel preburner oxidizer valve |
| FPP | Freon pump package |
| FPP | floating-point processor |
| FPPR | fixed price with price revision |
| FPQ | fixed, special-purpose radar |
| FPR | flight performance reserve |
| FPRV | flight product requirements verification |
| FPSP | focal plane signal processor |
| FPSR | flight planning and stowage review |
| FPSS | fine-pointing sun sensor |
| FPU | floating-point unit |
| FPV | flow proportioning valve |
| FPWG | FSD Planning Working Group |
| FQ | flight qualification |
| FQF | first qualification flight |
| FQI | flight qualification instrumentation |
| FQR | final qualification review |
| FQR | flight qualification recorder |
| FQR | formal qualification review |
| FQT | formal qualification test |
| FR | fast release |
| FR | final review |
| FR | firing room |
| FR | flight rule |
| FR | force-reflective |
| FR | frame rate |
| FR | fully reusable |
| FRACAS | failure reporting, analysis, and corrective action |
| FRAGNET | fragmented network |
| FRB | Failure Review Board |
| FRC | fixed radio control |
| FRC | flight readiness certification |
| FRCB | Flight Rules Change Board |
| FRCB | Flight Rules Control Board |
| FRCI | fibrous refractory composite insulation |
| FRCS | forward reaction control system (subsystem) |
| FRD | flight requirements document |
| FRD | functional requirements document |
| FRDI | flight research and development instrumentation |
| FRDR | flight readiness design review |
| FRE | flight-related element |
| FRE | format request element |
| FRF | flight readiness firing |
| FRFT | flight readiness firing test |
| FRG | Federal Republic of Germany |
| FRJD | forward reaction jet driver |
| FRL | frame reference line |
| FRL | fuselage reference line |
| FRM | facility requirements manager |
| FRP | fuselage reference plane |
| FRR | flight readiness review |
| FRRID | flight readiness review item disposition |
| FRSI | felt reusable surface insulation |
| FRT | flight readiness test |
| FRT | frequency response test |
| FS | Freon servicer |
| FS | factor of safety |
| FS | fail safe |
| FS | fail to sync |
| FS | fault summary |
| FS | federal specification |
| FS | fire suppression |
| FS | fixed silo |
| FS | flight system |
| FS | fluid system |
| FS | full scale |
| FS | functional schematic |
| FS | fuselage station |
| FS3 | Future Security Strategy Study |
| FSA | final-stage acceptance |
| FSA | frequency standard assembly |
| FSAA | flight simulator for advanced aircraft |
| FSC | Fairchild Space Company |
| FSC | federal stock classification |
| FSCM | federal supply code for manufacturers |
| FSCP | fire sensor control panel |
| FSCP | flight support computer program |
| FSD | Flight Simulation Division (JSC) |
| FSD | full-scale development |
| FSD&P | flight systems design and performance |
| FSDU | frequency synthesizer and distribution unit |
| FSE | factory support equipment |
| FSE | flight simulation engineer |
| FSE | flight support equipment |
| FSED | full-scale engineering development |
| FSF | first static firing |
| FSGS | flare/shallow glide slope |
| FSH | fixed superhard |
| FSI | final systems installation |
| FSI | flight software integration |
| FSIM | functional simulator |
| FSIWG | Flight System Interface Working Group |
| FSK | frequency shift key |
| FSL | Flight Simulation Laboratory |
| FSL | Flight Systems Laboratories |
| FSLP | first Spacelab payload |
| FSLT | first sea-level test |
| FSM | Firmware Support Manual |
| FSM | fuel supply module |
| FSN | federal stock number |
| FSO | facility security officer |
| FSO | functional supplementary objective |
| FSP | fault summary page |
| FSP | flight safety plan |
| FSPL | free-space-path loss |
| FSR | Flight Support Room |
| FSR | final system release |
| FSR | final systems review |
| FSR | flight support request |
| FSRR | flight software readiness review |
| FSRR | flight system readiness review |
| FSRS | flight system recording system |
| FSS | field spectrometer system |
| FSS | fire suppression system |
| FSS | fixed service structure |
| FSS | flight support station |
| FSS | flight support structure |
| FSS | flight support system |
| FSS | flight systems simulator |
| FSS | frequency selective surface |
| FSS | full-scale station |
| FSSE | flight sensor stimuli equipment |
| FSSR | flight system software request |
| FSSR | flight system software requirements |
| FSSR | functional subsystem software requirements |
| FSSS | Future Strategic Systems Study |
| FSTE | factory special test equipment |
| FSTS | frequency standard test set |
| FSU | Freon servicing unit |
| FSU | facility security office |
| FSU | factor of safety ultimate |
| FSU | frequency synthesizer unit |
| FSV | flight space vehicle |
| FSW | flight software |
| FSY | factor of safety yield |
| FT | fast track |
| FT | fault tolerant |
| FT | feed-through |
| FT | fine tracker |
| FT | flight team |
| FT | flight test |
| FT | formal training |
| FT | functional test |
| FT&C | formal training and certification |
| FTA | fatigue test article |
| FTA | fault-tree analysis |
| FTA | flight test article |
| FTAM | file transfer, access, and management |
| FTC | Florida Test Center (MDAC) |
| FTC | flight test conductor |
| FTD | Foreign Technology Division, U.S. Air Force |
| FTD | flight test directive |
| FTE | factory test equipment |
| FTE | flight test engineer |
| FTE | forced test end |
| FTFD | field test force director (AFSCF) |
| FTIR | Fourier transform infrared |
| FTIS | flight test instrumentation system |
| FTMC | fault-tolerant memory control |
| FTO | Foreign Technology Office |
| FTO | flight test objective |
| FTO | functional test objective |
| FTOH | Flight Test Operations Handbook |
| FTP | flight test procedure |
| FTP | full-throttle position |
| FTP | functional test program |
| FTP | functional test progress |
| FTPF | Flight and Training Planning Facility |
| FTR | flight test requirement |
| FTR | functional test requirement |
| FTRD | flight test requirements document |
| FTRD | functional test requirements document |
| FTS | far-term study |
| FTS | far-term system |
| FTS | federal telecommunications system |
| FTS | flight telerobotic service |
| FTS | flight telerobotic servicer |
| FTS | flight termination system |
| FTS | flight test station |
| FTS | flight test system |
| FTS | functional test specification |
| FTT | field test telescope |
| FTVE | functional technology validation experiment |
| FU | flight unit |
| FUB | forward utility bridge |
| FUI | federal unemployment insurance |
| FUO | follow-up output |
| FUT | flight unit test |
| FV | flight version |
| FV | front view |
| FV | incremental change in velocity |
| FVDS | fuel vent and drain system |
| FVF | first vertical flight |
| FVSS | fuel vapor scrubber system |
| FVV | facility verification vehicle |
| FW | flag word |
| FW | fuel wasting |
| FWB | Fahrenheit wet bulb |
| FWC | filament-wound case |
| FWG | Facility Working Group |
| FWW | food, water, and waste |
| FWWM | food, water, and waste management |
| FWWMS | food, water, and waste management subsystem |
| FXR | flash X-ray |
| FY | fiscal year |
| fpm | feet per minute |
| fps | feet per second |
| fps | frames per second |
| ft/sec | feet per second |