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lift index
flap or other fixed or movable surface to assist jet VTO by
reducing hot-gas reingestion, suckdown or other undesirable
effects.
lift index Air stability expressed as positive number if
stable, zero neutral and negative unstable.
lift-induced drag For all practical purposes, the same as
lift-dependent drag or drag due to lift, the rearwards
component of the total [resultant] force vector on a wing.
Purists could say lift-dependent drag is the difference
between drag at a given C L and that at a datum C L . They
could also argue * is not synonymous with trailing-vortex
drag, because the latter can exist in an inviscid flow.
lifting body Aircraft whose chief or sole lift is generated
by its body; usually hypersonic aircraft or spacecraft.
lifting re-entry One in which aerodynamic lift forces
play a significant role.
lift jet Ultra-lightweight turbojet or turbofan installed
only for upward thrust.
lift-lift/cruise Equipped with both lift jet(s) and
vectored-thrust engine.
lift motor Engine driving vertical-axis prop/rotor on
airship.
lift off 1 Separation of any aircraft or other flight or
space vehicle from ground or (eg Space Shuttle atmospheric
tests) a parent vehicle. Hence * speed, VLOF. For
aircraft, synonymous with unstick.
2 Undesirable gap between an eddy-current crack tester
and the inspected surface.
lift slope See lift-curve slope.
lift strut Bears tensile (rarely compression) load due to
wing lift.
LIFTT Leaders in flight-test training, includes [2002]
ETPS, Epner, CCA, DUT and IAS.
lift/thrust Ratio of lift to thrust of vectored-thrust
engine, usually varies from unity to zero over range of
nozzle movement; also see L/T.
lift vector Vector drawn through point at which lift force
acts, with angle showing direction (usually normal to
chord or OX axis, irrespective of aircraft attitude) and
length showing magnitude.
lift wire Bears tensile load due to lift of wing.
LIG 1 Laser image generator.
2 Lithium/iron gel.
light Visible * extends from about 0.4 µ [red] to 0.75 µ
[violet]. Velocity in vacuum = 299,792,456 ms -1
[983,571,007 ft/s].
light aircraft 1 Traditionally one having MTOW less
than 12,500 lb (5,670 kg).
2 Pre-1957, ‘aeroplane having a.u.w. less than 1,200 lb’.
3 Since 2006 LAPL has meant maximum weight 2,000
kg (4,409 lb).
light alloy One whose principal constituent is
aluminium; some authorities add ‘or magnesium’ but
these are usually described as magnesium alloys.
light anti-aircraft Guns 40 mm.
light bomber Today meaningless, and never universally
defined.
light-case Bomb encased in thin sheet steel for use
against cities and other soft targets.
light-emitting bar Vertical bar of three (rarely, more) Si
LEDs.
light-emitting diode Solid-state diode emitting visible
light when stimulated by electronic input, giving quickreacting
shaped light source.
light-emitting strip Horizontal rectangular strip display
made up of number of light-emitting bars, often used to
give analog lateral-position readout.
lightening hole Cut-out in relatively unstressed region of
structural sheet part to save weight.
lighter than air Buoyant in atmosphere (see aerostat).
light fighter Unusually small fighter intended chiefly for
close air-combat role.
light flight control Easy to move, esp. when adjacent
flight controls are heavy.
light gun Aldis lamp or other projector of visible pencil
beam, usually selectable white, red or green.
light ice Traditionally, can be ignored for up to 1 h.
light machine gun Not greater than rifle calibre.
light-microsecond Almost exactly 300 m, 984 ft.
lightning Any natural electrical discharge between
clouds or between cloud and ground.
Lightning Bolt Procedures enabling existing procurement
to be streamlined, and commercially available items
to be bought when appropriate (USAF).
lightoff, light off 1 Ignition followed by acceleration of
gas turbine during starting cycle.
2 Ignition of afterburner.
light pen Fibre-optic device for interfacing and accessing
computer via visual display.
light pipe Single or bundle of optical fibres.
lightplane See light aircraft.
light propeller aircraft 5,700 kg MTOW.
light-round Progression of the combustion flame from
one fuel burner to the next during gas-turbine starting
cycle.
Light Series Carrier for four 20-lb practice bombs (UK,
1922-c60).
Light Sport Aircraft Defined by the FAA as: 1 or 2 seats,
single engine, GTOW