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VIP levels
4 Vehicle improvement programme.
5 Variable installation position (engines).
6 Voice over Internet protocol.
7 Verified indentity pass (TSA).
VIP levels Those of video processor yielding weather
echo intensity for precipitation, from * 1 (weak) to * 6
(extreme).
VIPER, Viper Vitreous improved-performance extreme
removal.
Viper Video-input encoder.
VIPPS Visual-imaging pass-production system,
controlling personnel access.
virage Tight turn (pre-WW1).
virga Streaks of water or ice particles falling from cloud
but evaporating before reaching surface.
virgin fibre Continuous tow, long staple.
VIRSS Visual and IR sensor systems.
virtual airline Air carrier created only as legal entity to
facilitate franchising agreement.
virtual attrition Reduction in offensive tasking, either by
reducing overall numbers or by transfer of attack aircraft
to support roles, made necessary by effectiveness of
defences.
virtual cockpit One offering no natural external view,
only displays from sensors.
virtual collaborative engineering Links users at remote
locations into conference [eg, all can have input to a
drawing].
virtual gravity Terrestrial acceleration acting on parcel
of atmosphere, reduced by centrifugal force due to
parcel’s relative motion; symbol g* = approx. 99.99% g.
virtual height Apparent height of ionized atmospheric
layer calculated from time for radio pulse to complete
vertical round trip.
virtual image One visible in mirror but not projectable
on surface.
virtual image display Small CRT binocular colour highresolution
image of surface target, which appears to be
935 mm (36.9 in) behind face of magnifying lens.
virtual inertia That part of inertia forces acting on oscillating
body due to surrounding fluid (eg air) and
proportional to fluid density.
virtual level Energy level of subatomic nuclear system
for which excitation energy exceeds lowest nuclearparticle
dissociated energy.
virtual manufacturing Integration of available technologies
to get right information to right people at right
time to increase speed and accuracy of decisions.
virtual mass Actual mass plus apparent mass.
virtual piston Pumping effect caused by collapse of
launch tube by explosive lens.
virtual star Created by laser illuminating diffuse sodium
c100 km above Earth to give continuous readout of
atmospheric distortion of telescope optics.
virtual stress See Reynolds stress.
virtual temperature Temperature parcel of air would
have had had it been entirely free of water vapour, symbol
T v = (1 + 0.61 q) T where T is measured temperature and
q is specific humidity.
virtual VFR Combined enhanced and synthetic vision
giving pilot apparent VFR view of the external world at
all times.
VIS Voice-interactive subsystem.
Lowest selectable airspeed.
V IS
visibility meter
vis Invariably means visibility, but ambiguous.
Visa Vertically interconnected sensor array.
Visac Variable input speed alternating current.
viscoelasticity Behaviour of material which has hereditary
or prior stress-history memory and exhibits viscous
and delayed elastic response to stress superimposed on
normal instantaneous elastic strain.
viscosimeter Instrument for measuring viscosity;
Saybolt and Engler * are simple calibrated containers with
narrow orifice, result being obtained by timing run-off;
accurate (absolute) * include Stokes (falling speed of small
sphere), rotating-cylinder (outer cylinder drives inner via
fluid interface whose drive torque is measured), capillary
tube (Poiseuille), and oscillating disc (parallel and close to
plane surface).
viscosity 1 Dynamic * can be considered internal
friction in fluid; property which enables fluid to generate
tangential forces and offer dissipative resistance to flow,
defined as ratio of shear stress to strain; in air almost unaffected
by pressure but increases with temperature.
Symbol µ; unit Ns/m 2 = 1,000 cP; for air 1.78593 × 10 –5
Ns/m 2 (in traditional units 3.73 slug/ft-s).
2 Kinematic * is µ/ρ where ρ is density; varies with
pressure as well as temperature, units are m 2 /s = 10 6 cSt;
1 ft 2 s -1 = 0.092903 m 2 s -1 = 929.03 St. Also called dynamic
*. Symbol ν.
viscosity coefficient Synonymous with viscosity.
viscosity index Usually synonymous with viscosity, or
its variation with temperature.
viscosity-index improver Long-chain waxy polymer[s]
which stay thick at elevated temperatures.
viscosity manometer Instrument for measuring very low
fluid pressure by torque exerted on disc suspended on
quartz fibre very close to spinning disc; examples are
Dushman and Langmuir gauges.
viscosity valve Liquid-system control valve controlled
by viscosity of medium, eg in bypassing lube-oil cooler.
viscous aquaplaning Occurs when the runway is merely
damp, with a water film not penetrated by tyres;
important on smooth surfaces, especially coated with
deposited tyre rubber; persists to low speeds.
viscous damping Energy dissipation in vibrating system
in which motion is opposed by force proportional to
relative velocity.
viscous flow Flow in which viscosity is important; can be
laminar or turbulent but criterion is that smallest crosssection
of flow must be very large in relation to mean free
path. At very low R inertia becomes unimportant and
flow is governed by Stokes equations.
viscous fluid One in which viscosity is significant.
viscous force Force per unit mass or volume due to
tangential shear in fluid.
viscous stress Fluid shear stress, symbol τ = µdu/dy
(Newton’s law) where u is velocity distant y from surface
or other reference layer.
Visgard Polyurethane conductive coating for transparencies,
anti-fog, anti-scratch, anti-static.
visibility Distance at which large dark object can just be
seen against horizon sky in daylight (DoD, NATO, see
RVR, RVV).
visibility meter Instrument for measurement of visibility,
visual range, eg telephotometer, transmissometer,
nephelometer etc.
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