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velocity of light
synonymous with slipstream speed. Always greater than
aircraft airspeed, provided engine is operating.
velocity of light In vacuum 2.9979250 × 10 8 m/s, symbol c.
velocity of propagation Speed at which EM wave travels
along conductor, eg co-axial cable, waveguide; usually
= kc, where k is velocity factor.
velocity of rotation Rotational speed.
velocity of sound See sound.
velocity potential Integral of flow velocity parallel to
surface,
V
= φ, = Ux + Vy (rectilinear) = –––
Γθ
(vortex) = –– .
2π
∇
velocity profile Plot of velocity of viscous fluid in
traverse (2) perpendicular to flow direction; thus for
laminar flow through small tube ** = parabolic curve.
velocity ratio 1 Common meaning is q/q j where
q j = dynamic pressure of jet.
2 Free-stream relative velocity divided by propulsive
jet velocity, Vα/(Vj–Vα).
3 Generally, velocity of jet or propeller slipstream to
free-stream relative velocity.
4 Mechanical advantage.
velocity shear The difference in velocity between the
periphery of a propulsive jet and the surrounding atmosphere.
velocity signature Record of Doppler track of aerial or
other moving target.
velocity transducer Generates electrical output proportional
to imparted V, symbol V e .
velocity vector 1 Flight path in three dimensions. In
most aeroplanes, at high speed, this differs only slightly
from the longitudinal axis, whereas in a modern fighter in
a minimum-airspeed flypast the difference can be 20° or
more.
2 Main reference on primary flight display showing
desired flight path on which aircraft is held by FCS.
VEMD Vehicle and engine multifunction, or management,
display.
VEN Variable exhaust nozzle.
vendor Supplier to a programme, almost always manufacturer
of finished parts, devices and equipment though
* list often includes suppliers of raw material and even
services.
vendor audit Survey of vendor profiles, eg before
entering into discussion or negotiation.
vendor profile Detailed standardized description of
vendor companies for benefit of large-system prime
contractors.
veneer Thin sheet wood; when applied to plastics usually
means sheet with simulated woodgrain.
vent 1 Opening to atmosphere, eg from fuel tank, to
equalize internal and external pressures.
2 Opening in centre of parachute for stabilization.
3 Precision aperture in aircraft skin sensing true local
static pressure; called static *.
4 Spanwise aperture on USB flap either to entrain air
from below or to reduce Coanda attachment to upper
surface.
vent cap Vent (2) patch.
vent hem Reinforced hem around vent (2).
ventilated shock Shockwave at UST point which has
been stabilized and weakened by a double slot system.
ventilated suit Partial-pressure or pressure suit provided
with ventilation system, eg by ventilation garment.
ventilated tunnel Wind tunnel whose working section is
Verdan
perforated by holes or slots to prevent choking at Mach
0.8–1.2.
ventilated wet suit Designed to protect downed aircrew
against exposure.
ventilation garment Light inner suit, forming part of
pressure suit, through which dry air is pumped to control
body surface temperature and evaporation.
venting capability Ability of a closed volume to dissipate
sudden increase in pressure.
venting cycle Regular or automatic venting of Ni/Cd
battery to avoid cell imbalance or thermal runaway.
vent patch Piece of fabric covering vent (2) sewn to hem.
vent plug Cover over hole in outer skin [e.g., engine-bay
ventilation] inserted manually after each flight.
ventral 1 On belly side of body; hence with horizontal
fuselage, on underside, or, occasionally, firing or directed
through underside.
2 Underfin, vertical or inclined, fixed or hinged.
ventral container/pallet/pod/radar/tank Criterion for
adjective ‘ventral’, as distinct from fuselage, centreline etc,
is that item either forms underside of fuselage or is flush
against it, eg Beech 99 baggage container, RF-111 reconnaissance
pallet, Harrier gun pod, RA-5C SLAR and
Attacker drop tank.
ventral fin Fixed or movable fin on underside of body,
usually but not necessarily at tail.
ventral inlet Inlet on underside of body far enough from
nose not to be called chin inlet.
ventral nozzle Plain downward facing nozzle in underside
of jetpipe from ejector-lift engine, with pilot or
auto-controlled valve.
ventral turret Defensive gun turret on the underside of
the fuselage, usually aft of wing. One species was the ball
turret.
venturi Duct for fluid flow which contracts to minimum
cross-section at throat and then expands (usually to same
area as inlet); pressure at throat falls to minimum value
which can be used to drive vacuum instruments or as
measure of airspeed; flow throughout always subsonic.
venturi meter Instrument for measuring fluid mass flow
through calibrated horizontal venturi;
flow Q = A
p
2
where p 1 , A 1 are pressure
1 – p
––––––––––––– 2
ρ/2[1 – (A 2
/A 1 ) 2 ]
and cross-sectional area at start of venturi, p 2 , A 2 are
values at throat and ρ is density. Assumes flow laminar
and compressibility ignored.
venturi pitot Combination of pitot tube and venturi, one
giving pressure above atmospheric, other below.
venturi tube See venturi.
vent valve Located at a high point in an aircraft fuel
system, this provides an escape route for air during refuelling,
and can also spill excess fuel overboard.
Venus Visual-engine numeric spaces, produces smooth
3-D landscapes.
VEO-wing Vectored engine over, used in several RALS
studies.
VER 1 Vertical ejector, or ejection, rack; VER-2 is twinstore
*.
2 Vertical.
3 Version.
verb APPC command.
Verdan Versatile digital analyser; pioneer airborne
computer used in Reins (Autonetics); colloq. translated as
‘Very Effective Replacement for Dumb-Ass Navigators’.
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