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TVRS
3 Tactical video link.
TVRS 1 Tactical voice-recognition system.
2 Tactical video receiving system.
TVS 1 Target value structure.
2 Thermal video system.
TVSU Television sight unit.
TVT 1 TV tracker.
2 Thermal vacuum testing.
TV/TR Thrust vectoring, thrust reversing.
TW 1 Threat warning.
2 Training, water-cooled (USA 1919–24).
3 Tare weight.
T/W Thrust/weight ratio.
T w Torque applied at wing root.
TWA 1 Trailing-wire antenna.
2 Tare-weight allowance.
TW/AA Tactical warning and attack assessment
(Norad).
TWACN Theatre-wide area communications network
[Cormorant].
TWATN Theater-wide area telecommunications
network, not same as above.
TWC 1 Tungsten-wire composite.
2 Tailwheel conversion [of pilot].
TWCC Threat warning and countermeasures control.
TWD 1 Touchwire display.
2 Toward[s].
TWDL 1 Two-way data-link.
2 Terminal-weather data-link.
TWDR Terminal weather Doppler radar (TDWR is
more usual).
TWE Threat-warning equipment.
TWEB Transcribed weather broadcast.
12-5 Rule limiting MTOW to 12,500 lb.
1250 Paybook for RAF airmen in which career details
are recorded.
20-minute rating A-h rating of battery indicating current
required to discharge from maximum to zero in 20 min.
TWF Tail warning function (ECM).
TWG 1 Treaty Working Group (JAA).
2 Technical Working Group (US/NATO Stanags).
TWI 1 Threat- (or tail-) warning indicator.
2 The Welding Institute (UK).
TWIC Transport Workers Identification Credential
(TSA, 2004–).
Twids Taut-wire [perimeter] intrusion detection system.
twilight Designated civil *, nautical * or astronomical *
at Sun zenith angles of 96°, 102°, 108°, respectively.
twilight band Strip, about one aircraft span in width,
where radio range A/N just detected against steady note
(obs.).
twilight effect Faulty indications of radio navaids of pre-
1950 (occasionally, later) during twilight, ascribed to
ionospheric distortions.
twilight zone Bi-signal radio range zone where only A or
N heard (obs.).
twin Aircraft, usually aeroplane, powered by two
similar engines; arguably, one powered by two different
engines, eg jet plus prop.
twin-aisle aircraft Usually synonymous with widebody,
transport whose passenger seating is divided by two axial
aisles.
twin-array VASI One located ahead of desired touchdown
point, the other beyond.
twizzle
twin-boom aircraft Aeroplane [airplane] whose tail is
carried on left/right booms (1) symmetric about centreline.
twin cable Plastic extrusion containing two side-by-side
untwisted conductors.
twin-contact tyre See twin-tread.
twin-float seaplane One supported on water by two
similar floats side-by-side.
twin-gyro platform Platform housing two gimballed
gyros providing precision heading and attitude reference
for military aircraft; additional input, eg Doppler, is
needed for position readout.
twinkle roll Has been used to mean flick roll, but
normally maximum-rate slow aileron roll performed by
two or more formating aircraft simultaneously, each
about own axis.
twin paradox See time dilation.
twin-row engine Piston engine of radial type with two
rows each occupying one plane and each driving on one
crankpin.
twin-shaft Two-shaft engine.
twin-spool Two-spool.
twin tail Conventional tail with twin vertical surfaces,
often at or close to extremities of tailplane in slipstream
from engines, esp. with single fuselage.
twin-tread tyre Contacting ground around two circular
treads separated by deep groove; intended to reduce
shimmy, esp. of tailwheels.
twin-tub aircraft Two-seater, especially with open cockpits.
twin-wing aircraft 1 Term currently in use for diamondwing
aircraft; especially when tips are joined by
vortex-generator endplates.
2 Since 2002 also used to mean a UAV biplane.
TWIP Terminal weather information for pilots.
twist 1 Variation in angle of incidence along aerofoil,
always present in rotating blades. In wing, normally
subdivided into aerodynamic (defined as variation in nolift
direction along span) and geometric (variation in angle
between chord and fixed datum along span). Positive
called washin, negative washout.
2 Roll about longitudinal axis, as in * and steer.
twist and steer Control method for fixed-wing aerodynes
in which it is necessary first to roll to (normally large)
bank angle and then pull round on to desired heading.
Only possible method on aircraft (eg missiles) with no
control surfaces other than main wings, which pivot
independently for twist and together for steer. Not applicable
to conventional aeroplanes, which make
simultaneous harmonized movements about all axes.
twister 1 Device twisting electric component of EM,
especially coherent radar.
2 Tornado (colloq.).
Twisteron Idea for continuously optimising L/D ratio
by twisting under torsional loads L/R wings in unison
(Utah State Univ.).
twitch factor Unquantified factor degrading flight-crew
(esp. pilot) performance in terms of accuracy or incidence
of errors, resulting from fear or high workload. In
simplest case ** magnifies task of adding 2+2.
twizzle Various manoeuvres adopted by combat pilots,
esp. of large aircraft, to throw fighter off aim or effect
escape; always involved steep climb and/or dive,
combined with limited rolling manoeuvres (WW2).
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