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V-A
2 Axial gas velocity.
V-A Volt-amperes, electrical apparent power.
VAA 1 Vintage Aircraft Association (US).
2 Vertical alert annunciator.
VAAC Vectored-thrust aircraft advanced [flight]
control.
VAATE Versatile affordable advanced turbine engine
(USAF programme).
VAB 1 Vehicle (originally Vertical) Assembly Building,
at KSC.
2 Vehicular Assembly Building [Tanegashima] (J).
3 Variable-area bypass.
V AB Resultant velocity of circulation of two particles A
and B.
VABI, Vabi Variable-area bypass injector.
V abs Absolute velocity; i.e., not relative.
VAC 1 Vintage Aeroplane Club, 1951–55; Vintage
Aircraft Group 1964–74; Vintage Aircraft Club 1974–,
[OX8 8DW (UK).
2 Valiant Air Command [Florida-based warbird
centre].
3 Volts a.c.
4 Visual-approach chart.
VACA The Vintage Aircraft Club of Australia [office,
Adelaide, SA].
vacancy Unoccupied lattice site in crystal.
Vacbi Video and computer-based instruction.
VACIS, Vacis Vehicle and cargo inspection system.
VACL Virtual aircraft component location, 3-D software.
VACS 1 Variable-autonomy control system (UAVs).
2 Voice-activated control system.
VACT Visual air-combat training.
vacuum casting See vacuum melting.
vacuum evaporation Loss of molecules from body’s
surface in space.
vacuum gauge Instrument for measuring low fluid
pressure, eg Pirani, Knudsen, ionization, McLeod.
vacuum melting Almost self-explanatory, preparation of
advanced steels and other alloys in a near-vacuum in
order to reduce [almost eliminate] the unwanted formation
of oxides, hydrides and other impurities.
vacuum orbit Orbit of satellite round incomparably
more massive body in complete absence of any atmosphere.
vacuum pump Device for establishing unidirectional
flow of gas molecules and thus of evacuating fixed enclosure;
following gross evacuation by mechanical
pump alternatives include vapour/diffusion pump,
cryopump etc. Also, in aircraft, simple device for applying
depression to air-driven flight instruments, eg venturi.
vacuum specific impulse Specific impulse in vacuum
operation.
vacuum system control Sucks air from aircraft toilet WC.
vacuum thrust Thrust of rocket in vacuum, typically
about 25% greater than at sea level (actual thrust rises by
approx. product of atmospheric pressure and rocket
nozzle exit area).
vacuum tube Electronic tube whose internal pressure is
so low that residual gas or vapour atoms or molecules
have no significant effect on operation; also called
thermionic valve in most common form.
vacuum tunnel Wind tunnel operated at much less than
sea-level pressure.
valve lead
VAD 1 Velocity/azimuth display.
2 VHPIC applications demonstration (programme).
3 Visual approach and departure [usually helicopter]
chart.
VADR Voice and data recorder.
VADS Vulcan air-defense system (USA).
VAE Virtual air environment.
VAES Voice-activated electronic system.
VAFA Vintage Aircraft and Flying Association (UK).
VAFB Vandenberg AFB (USAF), see Vandenberg.
Vaftad Volcanic-ash forecast transport and distribution.
VAI Voice-interactive avionics (not VIA).
VAI-IPR Versatile affordable integrated-inlet fan for
performance and reliability.
VAL 1 Visual approach and landing [chart].
2 Variable approach light [3 intensities, 2°–8°
azimuth].
3 In valleys [mist/fog].
Valid Variability and life data.
validation Generalized word for activity intended to revalidate
licence or authority, esp. training, examinations
and emergency-procedure practice of graduate pilot,
instructor or ATC (1) officer. ATC * involves simulated
crises worse than any normally encountered.
validation phase Period when major-programme
characteristics are refined by study and test to validate
alternatives and decide whether to proceed to FSD.
valise Storage envelope for liferaft.
V∝, V-alpha Free-stream velocity, or far-field velocity
relative to aircraft..
VALPT Variable-area LP turbine.
Valsalva Called * manoeuvre, or * technique, involves
pinching nose and blowing/swallowing to relieve dP on
eardrums following sudden loss of cabin pressure.
Value Validated aircraft logistics utilization evaluation.
value engineering Complete engineering discipline
devoted to seeking ways to achieve desired hardware
performance, quality and reliability at minimal total cost,
eg by elimination of unnecessary items, changes in
material and manufacturing method, and simplification
of design.
valve 1 Device for controlling fluid flow, eg into and out
of piston-engine cylinder (inlet *, exhaust *) or into/out of
aerostat, esp. airship.
2 Numerous other fluid-flow control devices in
hydraulics, oxygen, propellants, hot-gas, bleed air, carburetion
[US spelling] and other systems.
3 Vacuum tube (UK usage).
4 To release air or gas from aerostat into atmosphere.
valve clearance Gap between end of stem and rocker
arm.
valve duration Time or angular crankshaft movement
during which a valve remains open.
valve face Mating edge of valve (1) bedded by grinding
into seat.
valve gear Mechanism driving valves of piston engine.
valve hood Umbrella-like cowl protecting main airship
gas valve against rain or icing.
valve lag Angular motion of crankshaft between either
maker’s specified valve-closing position or TDC and
point at which valve actually closes.
valve lead ‘Leed’, not ‘led’, angular motion of crankshaft
between closure of valve and either maker’s specified
closing position or TDC.
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