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topping
topping Operating cycle of liquid-propellant turbopump
for rocket engine in which cryogenic fuel is heated,
producing high-pressure gas used to drive turbine(s); this
gas then passes at lower pressure to combustion chamber
(different nozzles from main flow), where it burns. Hence
* cycle, * engine.
topping off Replacement of cryogenic propellant lost by
boiloff.
topping up Replenishment of gas-filled aerostat, eg after
a flight.
topple Real or apparent wander in vertical plane of
gyro-axis (see toppled).
toppled Gyro whose gimbals have for any reason ceased
to maintain its correct axis in space, so that further
rotation of mounting results in violent direct precession.
Traditional gyro instruments can be * by aerobatics or
any rotation of aircraft axes beyond defined limits, instrument
then being useless as attitude reference until gyro has
settled again into normal operation. New term is needed
for either topple or toppled.
top rudder Applying rudder towards the upper wing in a
turn: thus, in a steeply banked L turn, pushing on R pedal
[eg, to keep nose from dropping below horizon].
TOPS 1 Thermoelectric outer-planet spacecraft.
2 Transfer orbit and payload-testing support.
Topsar Topographical synthetic-aperture radar.
Topsat Tactical optical satellite (UK).
Topscene Tactical operational scene (Tamps).
Top Secret High grade of defence classification for
material whose unauthorized disclosure might result in
severance of diplomatic relations, war or collapse of
defence planning.
Topsep Targeting optimization for solar-electric
propulsion.
top shock Shockwave on upper surface of aerofoil.
topside On carrier flight deck, esp. movement thereto by
elevator; eg coming * as aircraft or other item appears
level with deck (USN).
top-temperature control Any subsystem limiting a
temperature to a specified safe limit, esp. that for TET,
TGT or equivalents.
TOR, T-OR 1 Takeoff run.
2 Tentative operational requirement.
3 Terms of reference.
tor Torr.
TOR a , TORA Takeoff run available, usually = TOR.
Toray Trade name [from torched rayon] of carbon
fibres of outstanding specific strength and modulus.
torch igniter Combined igniter plug and fuel atomizer
emitting jet of flame from burning fuel. Very rare in gas
turbines but occasionally used in afterburners and a
minority of liquid and solid rockets.
torching 1 Faulty operation of gas turbine, esp. jet
engine, in which unburned fuel travels past turbine and
results in flames travelling down jetpipe, often expelled
from exhaust nozzle.
2 Faulty operation of piston engine in which unburned
fuel travels through exhaust valve and burns in exhaust
pipe, often causing visible flame beyond exhaust nozzle.
3 Degassing in ultrahigh-vacuum technology by
applying gas flame to walls.
toric Having a surface described by a segment of a conic
section.
toric combiner Optical lens assembly used to combine a
torque-set screw
generated-information display with an image of real
world.
Torlon Heat-resistant resin used in graphite-fibre
composites for high-temperature applications (Amoco).
tornado Localized violent whirlwind east of Rockies in
US with such low pressure in core as to explode structures
in its path, usually pendant under a Cb. Also used for Gulf
of Guinea thunder squalls advancing westwards in line.
toroidal Shaped like doughnut.
toroidal vanes Rings of curved section guiding air to eye
of centrifugal compressor.
torpedo director Traditional optical sight for aerial
torpedo attack; user sets target size/speed and receives
azimuth guidance.
torque For all practical purposes, synonymous with
turning moment or couple [which see]. A rigorous definition
is effectiveness of a force in setting a body into
rotation, according to which trying to loosen a tight nut
unsuccessfully or rotate free end of rod fixed at other is
not application of * (though in second case it is torsion).
Often invertedly defined as resistance to a twisting action.
Conversions include 1 lbf-in = 0.112985 Nm; 1 lbf-ft =
1.35582 Nm; 1 Nm = 8.8507 lbf-in = 0.73756 lbf-ft. For
propellers see * component.
torque box Box-like structure, eg wing torsion box,
designed to resist applied torque.
torque brake Variable brake on rotating shaft, eg slat
drive, triggered at particular point of system travel.
torque coefficient Product of propeller torque divided by
ρN 2 D 5 ; k Q = Q/ ρN 2 D. 5 .
torque component Q c , tangential force acting in plane of
propeller rotation on any elementary chordwise lamina;
thus total propeller torque Q = N½ρ V 2 × integral of Q c
from axis to tip with respect to radius.
torque dynamometer Measures shaft power by
measuring N (rpm) and torque.
torque effect Reaction on vehicle of torque applied to
propeller or rotor (** for rotodome usually ignored); in
helicopter countered by tail rotor.
torque gauge Indicator of torque in propeller shaft.
torque horsepower Shaft horsepower, often same as
brake horsepower. Use to be discouraged because of
confusion with thp (thrust horsepower).
torque link Pivoted links preventing relative rotation
between cylinder and piston of oleo shockstrut; limiting
factor with bogie main gears on allowable steering angle
of nose gear. Also called scissors or nutcracker.
torquemeter Device, either instrument or component
part of engine, for measuring torque; in turboprop or
some piston engines, usually oil-pressure system sensing
axial load on reduction-gear planetary helical gears or,
less often, tangential reactive load around annulus gear.
torquer Device imparting torque to an axis of freedom
of a gyro, usually in response to signal input.
torque roll Performable only by aircraft with fastresponding
(eg piston) engine on centreline giving very
large torque in relation to aircraft weight; approach is
made at flight idle at minimum safe flying speed, whereupon
throttle is banged wide open to cause rapid roll in
opposite direction as aircraft accelerates, pilot recovering
to wings-level with aileron.
torque-set screw Can be repeatedly unscrewed without
losing original torque needed to release; used to latch
long-MTBM panels.
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