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throttle back
admission to engine of either air, fuel or (piston engine
only) mixture.
4 To reduce power of engine, also called to * back.
5 To constrict fluid flow path and thus reduce mass
flow.
throttle back To reduce power.
throttle friction Pilot-operated device which greatly
increases resistance of throttle lever(s) to movement,
effectively locking them in set position; also called friction
lock.
throttle icing Ice accretion in carburettor near or on
partially closed throttle (3).
throttle lock See throttle friction.
throttle push Pilot action to increase power.
throttle sensitivity Change in thrust or power per unit
movement of throttle lever.
throttle tension Locking resistance value of friction lock.
throttling capability Range of thrust expressed as
percentage to 100, over which liquid rocket (occasionally
other type of engine or propulsion) is designed to operate.
through-deck ship Generally, one with flight deck unobstructed
by any full-width superstructure, even though
not necessarily extending to bow.
through hardening Heat treatment or other procedure
which increases hardness through the entire piece of metal
[see case hardening].
through-stick feedback Characteristic of some autopilots
that, when engaged, pilots flight controls move.
through-thickness pinning Repair of major damage to
composite structure in which numerous fine pins are
collapsed by a foam carrier.
throw 1 Part of crankshaft to which conrod attached,
comprising webs and crankpin.
2 Loose measurement of distance to which ECS freshair
inlet projects, in absence of bulk cabin air movement.
thrower ring Flange on rotating shaft which flings off
leakage oil or other fluid.
throw-off clutch Mechanical shaft drive which automatically
disconnects as a particular condition is reached [in
starting an engine, when torque falls to zero].
throw weight Total mass of payload carried by ballistic
missile, in case of ICBM including warheads, RVs, decoys
and other penaids, post-boost propulsion and terminal
guidance systems.
THRP Port throttle (caption).
THRS Starboard throttle (caption).
THRU, Thru 1 Through.
2 I am switching you to ...
thrust Force, esp. that imparting propulsion, SI unit is
newton (N), conveniently multiplied in kN = 224.80 lb st;
1 lb st = 4.44483 N [see force for other conversions].
Useful * of turbofan or turbojet is resultant of all * generated
by fan (positive), front of combustor (positive),
turbines (negative) and nozzles (negative),
* at each location being AP + ––––
WV
g
where A
is area of flow cross section, P is pressure, W is mass flow
W(V
and V flow velocity. Overall net * is A (P-Po) + –––––––– j V)
g
where P is static pressure at nozzle, Po local atmospheric
pressure, V j is jet velocity and V velocity of aircraft.
thrust angle 1 Acute angle between axis of nozzle of
canted solid motor and centreline axis of vehicle,
measured in plane passing through both axes if possible.
thrust/frontal area
2 See propeller angle of attack.
thrust augmentation Usually means afterburning, but
also applied to water injection, and to piston engine
ejector-exhaust schemes.
thrust-augmented wing Aeroplane wing in which
enhancement of circulation by powered-lift system also
gives significant additional thrust (many arrangements,
but augmentation of thrust invariably secondary
objective).
thrust axis Axis along which resultant propulsive thrust
acts. With a turbofan this is resultant of fan and core jets,
and with a turboprop that of propeller and (probably
angled) jet. In multiengined aircraft * can oscillate
because of engines outboard on flexible wing.
thrust bearing Bearing, usually tapered roller, needle or
ball, that resists axial shaft load due to propeller thrust.
thrust buildup Sequence of programmed events in large
rocket engine between ignition and liftoff.
thrust bump Sudden uncommanded change [especially
increase] in thrust.
thrust chamber Complete thrust-producing portion of
liquid rocket engine comprising combustion chamber and
nozzle, often mounted on gimbals; not applicable to other
types of engine.
thrust coefficient 1 For propeller, basic performance
calculation method based on Drzwiecki method of plotting
grading curve of thrust against blade radius, yielding
value k T , constant for each value of advance ratio J; **
then equals k T J 2 and has symbol C T . This is also measured
thrust divided by ρ n 2 D 4 where ρ is density, n rpm and D
diameter.
2 For rocket motor, measured ** is thrust: time integral
over action-time interval divided by product of average
throat area and integral of chamber pressure: time over
action-time interval, symbol C f .
3 For CC/BLC blowing slit, T/qS.
thrust component In propeller theory (Drzwiecki), force
on one element parallel to axis of rotation, T c ; convenient
to plot T c as ordinate against blade radius, area under
curve being measure of total thrust, T = N½ρV 2 ∫ r o T c dr
where N is number of blades, ½ρV 2 dynamic head and T c
integrated between axis of rotation (or, in practice,
spinner diameter) and tip radius r.
thrust control computer AFCS computer providing
control of engine N 1 and thrust, computation of engine
limit parameters, and autothrottle.
thrust cutoff See cutoff.
thrust decay Gradual falloff in thrust of solid motor,
usually a slow fall from peak to cutoff or burnout
followed by rapid ** over 2 to 8 s and to zero after perhaps
10–12 s.
thrust-decay system Idle-area reset (turbofan).
thrust deflector Various schemes for V/STOL or
STOVL, see four-poster, switch-in deflector, vectored
thrust, etc.
thrust equivalent horsepower See thrust horsepower.
thruster Small propulsor, normally any of many kinds
of rocket, used for spacecraft attitude control or fine
adjustment of velocity.
thrust face Side of propeller blade corresponding to
underside of aerofoil.
thrust/frontal area Jet-engine thrust divided by engine’s
nominal or published frontal area; fair criterion in early
days of jet propulsion but today meaningless. Important
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