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LGM
LGM US weapon category, silo-launched missile.
LGOS Landing-gear operating speed.
LGR Laser guidance receiver.
LGS 1 Laser gunfire simulator.
2 Laser gyro strapdown.
3 Landing guidance system.
LGSC Linear glide-slope capture.
LGSM Light ground-station module.
LGT Landing-gear tread.
lgt Light, lighting.
Lgtd Lighted.
LGTR Laser-guided training round.
LGW Landing gross weight.
LGWB Landing gear wheelbase.
LH 1 Left-hand.
2 Light helicopter.
L/H Local horizontal.
LHA 1 US Navy ship category, large helicopter assault
carrier.
2 Local hour angle.
LHC 1 Light helicopter cycle (standard cycle for US
turboshaft engine testing).
2 Left-hand circuit.
3 Lower-hold cargo.
LHe Liquid helium.
LHF Liquid-cooled, heavy fuel.
LHM Laser-hardened materials.
LHN Long-haul network.
LHOX Low and high-pressure oxygen.
LHP Lightning HIRF protection.
LHS 1 Left-hand side.
2 Latin hyperscale sampling [alternative to Monte
Carlo].
LH 2 Liquid hydrogen.
LHV 1 Fuel lower heating value, L/kgK, formerly
measured in BTU/lb.
2 Hang-gliding (Liechtenstein).
LHW Laser-homing weapon.
LHWR Lightning-hazard warning radar.
LHX Light helicopter, experimental.
LI 1 Lane identification (early Decca).
2 Laser interrogator (or interrogation).
3 Lithium-iron [LiFe preferred].
4 Letter of intent.
5 Lift index; numerically positive, negative or zero if
atmosphere stable, unstable or neutral.
6 Low-intensity light[s].
L i Maximum weighted noise level over series of i noise
events.
LIB 1 Left inboard.
2 Loudspeaker intercom box.
libration Small long-period oscillation, esp. that of
Moon’s aspect from Earth.
LIC Low-intensity conflict [A adds aircraft, S system,
hence Licas].
licence US = license, document authorising holder to
carry out functions specified; see rating (3), validation.
LID 1 Lift-improvement device (jet V/STOL).
2 Luftfahrt Information Dienst (DDR).
3 Large integrated display.
4 Laser irradiation detector.
5 Liquid-interface diffusion (bonding).
lidar Light detection and ranging, laser counterpart of
radar.
lift-improvement device
Lids, LIDS Low-impact docking system.
LIF Lead-in fighter.
LiFe Lithium-iron.
life 1 Allowable total period of operation of hardware
item.
2 To assign such a period; hence, a lifed part.
lifeboat Transport vehicle for rescuing crew from spacecraft,
usually parafoil Earth landing.
life cycle Essentially self-explanatory, the sequence of
phases through which a product may be expected to pass.
The most common * comprises: concept – definition –
design – build – test – operate – [sometimes refurbish] –
scrap or retire. Also called product *.
liferaft Correct term for inflatable emergency ‘dinghy’.
life-support system Provides environment to sustain
human life in space, including during EVA.
LIFM Linear instantaneous frequency measurement.
Lifmop Linear frequency-modulated pulse.
Lifo Last in, first out.
LIFP Low-inertia flat-plate (antenna).
LIFR Low-altitude instrument flight rules.
LIFT Lead-in fighter training, or team.
lift 1 Total lifting force from a wing (component of
resultant force along lift axis), aerostat envelope or other
source excluding engine thrust. Normally, force
supporting aircraft. Traditionally L = C L ½ ρV 2 S, where
C L is lift coefficient, ρ density, V velocity and S area.
2 Any element of such lift, acting through particular
point.
3 Whole or part of an airborne operation, thus second
* means second force to be airlifted.
4 Aircraft-carrier elevator (British terminology).
5 Total traffic capability of fleet of transport aircraft
[esp. military].
lift axis Line through c.g. perpendicular to relative wind
in plane of symmetry.
lift coefficient C L , dimensionless measure of lift of
surface; actual lift divided by free-stream dynamic pressure
½ρV 2 and surface’s area S.
lift/cruise engine Turbofan or turbojet with vectoring to
give jet lift or thrust.
lift curve Plot of lift coefficient against angle of attack
(C L :α), theoretically = 2π per radian at low subsonic Mach
numbers.
lift curve slope Inclination of lift curve at any point, rate
of change dC L /dα.
lift-dependent drag See lift-induced drag.
lift/drag ratio, L/D Ratio of total lift to total drag,
fundamental measure of efficiency of aircraft; L is
normally constant and equal to weight but drag varies
approx as square of airspeed; thus L/D plot is curve with
peak at one particular airspeed for each aircraft, L/Dmax.
lift dumper Flat plate, usually long span and short
chord, raised by powered system (rendered operative by
weight on MLG) from upper surface of wing (usually
inboard and at about 60% chord) after landing to destroy
lift and improve wheel-brake traction. Usually synonymous
with ground spoiler.
lift fan 1 Turbofan of HBPR installed only for lift
thrust.
2 Free-running fan driven by tip turbine from external
gas supply installed only for lift (note: 1 and 2 may have
exit vanes to give a diagonal lift/thrust component).
lift-improvement device Any aerodynamic strake, dam,
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