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voice-grade channel
voice-grade channel Covers about 300–3,000 Hz, for
speech, analog, digital or facsimile.
voice keying System enabling telecommunications to
use common R/T transmit and receive sites and similar
frequencies but with voice-operated carrier suppressor
and delay network to switch outgoing signal to transmitter
and incoming to receiver. Remote stations
normally switch automatically to receive mode except
when user is speaking.
voiceless homing Any electronic homing system not
using speech; traditionally meant radio range (arch.).
voice message unit Software-controlled system
providing voice or tone warnings of faults, sensor activity
and other occurrences.
voice-operated relay See voice keying.
voice rotating beacon Short-range radio navaid transmitting
stored-speech headings (usually QDMs) which
differ from 000° round to 359°; a form of talking VOR,
also called talking beacon, abb. VRB (arch.).
void Undesired gap in welded joint.
void fraction 1 Percentage of total frontal area of jet
engine through which airflow passes.
2 Also several meanings in composite materials and
structures.
Voigt effect Double refraction (associated with
Zeeman) of light passing through vapour perpendicular to
strong magnetic field.
VoIP Voice over Internet Protocol.
VOIR Venus-orbiting imaging radar.
Voiska-PVO Troops of air defence of homeland
(USSR, R).
Voispond Proposed Calsel function that would automatically
identify an aircraft by a voice recording.
VOL 1 Vertical on-board landing.
2 Volume.
volatile 1 EDP (1) memory which dissipates stored
information when electrical power is switched off; thus,
next morning or after weekend all bits must be restored
before computer operation. Also means electrical
transients cause corruption (though this may be only
temporary). Hence * data, * memory, volatility.
2 Having high vapour pressure, and thus low boiling or
subliming temperature at SL pressure; hence volatility.
volcano early warning system This would warn airtraffic
control centres within five minutes of the start of
an ash-producing eruption (US Geological Survey).
vol à voile(s) Gliding, soaring (F).
vol d’abeille Beeline, straight-line distance (F).
Volmet Routine ground-to-air broadcast of meteorological
information (ICAO). Today such broadcasts are
Metars and apply to a designated list of airfields.
Volocan Radar tracking/computing of flight paths to
solve stacking problems (USAF 1953).
vol piqué Dive (F).
vol plané Planing (inclined) flight, ie glide by powered
aeroplane (arch. except in F).
volt SI unit of EMF, = W/A.
voltage amplifier Delivers small current to high impedance
to obtain voltage gain.
voltage-dependent resistor Ohms = f(V); resistance
varies directly with applied voltage.
voltage drop PD across any impedance carrying current.
voltage-fed aerial (antenna) Fed from one end, where
signal potential is maximum.
Vorloc, VOR/Loc
voltage gain Ratio of output/input voltages.
voltage standing-wave ratio Ratio maximum/minimum
V along waveguide or coaxial.
volt-ampere SI unit of alternating-current power,
symbol S, made up of power component P watts and
reactive component Q; S = P 2 +Q 2 ; see power factor.
voltmeter Instrument for measuring potential difference,
ie V.
volume SI unit is m 3 (conversion factors for non-SI
measures, from ft 3 × 0.02831684, UK gal × 0.004546087
and US gal × 0.003895411); litre (dm 3 ) = 0.035287 ft 3
= 60.9756 in 3 ; cm 3 (cc) = 0.06102 in 3 ; UK gal [Imp. gal]
= 1.20095 US gal; US gal = 0.83267 UK gal.
volume fraction 1 Proportion, usually %, of reinforced
composite (FRP) occupied by reinforcing fibres.
2 Generally, proportion of whole volume occupied by
particular substance.
3 For aerostats see air *, gas *.
volumetric efficiency Volume of combustible mixture (in
diesel, air) actually drawn into cylinder of piston engine
on each operating cycle divided by capacity (swept
volume) of cylinder, usually expressed as %. Symbol η ν
or e ν .
volumetric loading Also called * density, total volume of
solid rocket motor propellant divided by total volume of
unloaded case, usually expressed as %. Symbol λ.
volume unit Measure of audio volume to be outputted by
electrical current, expressed in dB equal to ratio of magnitude
of electrical waves to magnitude of reference volume,
usually 1 mW; abb. VU.
volute Spiral or planar helix; thus, spiral casing of
centrifugal compressor or supercharger impeller.
Vom Volts/ohms/milliamps tester.
Vomit Comet Aircraft, e.g. KC-135, used for zerogravity
tests.
Von Brand Standard method of measuring jet smoke by
passing measured gas volume through filter and then
recording intensity of calibrated light reflected by filter
pad. Gives quantified measure of particulate matter
trapped by chosen filter. Hence * scale for visible smoke.
von Kármán street See street (also called Kármán street).
VOP Variation of price.
VOR V.h.f. omnidirectional radio range, announced by
RCA in 1941 and forced through by US in 1959 to become
universal global [except USSR] radio navaid. Comprises
fixed beacon emitting fixed circular horizontal radiation
pattern at 108–118MHz on which is superimposed
rotating directional pattern at 30 Hz giving output whose
phase modulation is unique for each bearing from beacon.
Thus airborne station can read from panel instrument
bearing of aircraft from station, called inbound or
outbound radial. Each fixed station identified by threeletter
keyed intermittent transmission (sometimes voice).
See Doppler *.
VOR/DME VOR steering guidance with DME distance
information.
Vorgen Voltage generator.
VOR/ILS Linkage of VOR signals to aircraft ILS so
that left/right steering guidance is given by ILS panel
instrument. Latter often called * deviation indicator, or
Vorloc.
Vorloc, VOR/Loc Panel instrument giving steering
guidance from received VOR signals; can be complete ILS
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