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heavy bomber
density; most consist chiefly of tungsten, but osmium,
iridium and depleted uranium are important.
heavy bomber Aircraft designed to deliver heavy load of
conventional ordnance to targets in enemy heartlands
(arch.).
heavy dropping Delivery by system of parachutes of
exceptionally bulky or heavy load, suitably packaged and
cushioned.
Heavy Fuel In US usage, all DFs (diesel fuels) plus JP-5
and JP-8.
heavy landing See hard landing (1).
heavy maintenance Maintenance taking 30 days or
longer.
heavy metal Classic warbird, esp. large and powerful
(colloq.).
Heavyside E-layer.
Heavy Wagon Designated routes for lo military flights
within Conus; 300 series for various nav/electronic
systems evaluation and 400 Series for nav. training and
weather evaluation at 500 ft (152 m) down to MOCA,
normally not over 500 kt (USAF, USN).
HECS High-performance engine control system.
hectare Non-SI unit of large areas = 100 are = 10 4 m 2 .
hecto Prefix, multiplied by 10 2 , symbol h.
hectopascal Pressure of 100 Nm -2 = 1 mb, symbol hPa.
hedge-hopping Lo(2) flight by light GA aircraft
(colloq.).
hedging Increasing one’s stock of a commodity
[especially fuel] in the belief price will rise.
Hedi, HEDI High-endoatmospheric defense interceptor
(SDI).
HEDP Ammunition, high-explosive, dual-purpose.
HEDR High-energy dynamic radiography.
Heel Helicopter emergency-egress lighting; s adds
system.
heeling Roll due to turn while taxiing.
HEETE, Heete Highly efficient embedded turbofan [or
turbine engine].
HEF High-expansion foam (anti-fire) usable at 1.5%
concentration.
HEH Hershey, Eberhardt, Hottel, basic analysis and
charts for idealised piston engine cylinder performance.
HEI 1 Ammunition, high-explosive incendiary.
2 Hot-end inspection.
height 1 In performance, Ht defined as true vertical
clearance between lowest part of aircraft (assumed aeroplane)
in unbanked attitude and relevant datum.
2 General common definition: h, vertical distance of
level, point or object considered as point, measured from
specified datum (normally associated with QFE).
3 Vertical distance from reference ground level to specified
upper extremity (close to but not necessarily highest
point, which may be small whip aerial, static wick or other
flexible part) of aircraft at specified weight (usually
MTOW) and tyre inflation pressure when parked on flat
horizontal surface.
height above airport, HAA Height of MDA above
published airfield elevation.
height above touchdown, HAT Height of DH or MDA
above highest obstruction in touchdown zone.
height computer Calculator for converting barometrically
indicated to true altitude by correcting for
atmospheric density.
heightfinder radar, HFR One whose primary output is
heliosynchronous
precise height of distant target; has nodding aerial giving
multi-lobe beam.
height lock Function of autopilot or flight system in
holding (after in some cases capturing) selected height h.
height ring Visible on most displays of weather/
mapping/AW/cloud-collision warning and other forwardlooking
radars as bright ring beyond zero-range ring
formed by direct reflection from Earth’s surface.
height/velocity curve Fundamental plot of IAS against
altitude included in helicopter flight manual; indicates
region(s) from which safe autorotative descent is possible,
normally assuming zero wind, sea level, MTOW.
Heim joint Universal coupling in torque tube.
Heine mat Flexible mat towed by support vessel on to
which marine aircraft taxies before being hoisted on
board.
HEIPT Helicopter engines integrated product team.
HEI-SAP High-explosive incendiary, semi-armourpiercing.
HEI-T Ammunition, HE incendiary, tracer.
HEJOA Heathrow Executive Jet Operators’
Association,
HEL High-energy laser [A adds applications, also see
HELCM, Helex, HELJTO, Hels, HELSTF and Heltads].
Helarm Helicopter, armed (sortie).
HELCM HEL countermeasures.
HELD Helicopter [or high-energy] laser designator.
Helex HEL experiment[al].
Heli Helicopter.
Heliarc Inert (helium) gas welding technique patented
by Northrop 1940.
helical compressor Diagonal-flow compressor.
helical gear Spur gear with teeth arranged diagonally;
contact begins at one end of tooth and proceeds
diagonally across width, two teeth, normally transmit
load at any time. Double * (herringbone) gear eliminates
axial load.
helical tip speed Actual airspeed at tip of propeller,
taking account of vehicle’s airspeed.
Heli-Coil Patented hard-steel thread inserted in soft
metal or to repair stripped female thread.
helicopter Rotorcraft deriving both lift and control from
one or more power-driven rotors rotating about substantially
vertical axes. Rotors are driven as long as engines
operate above certain minimum input speed, and airflow
through rotor(s) is downwards except in autorotative
engine-failure mode.
helicopter approach-path indicator Hapi, ground optical
aid giving steady white for correct [0.25-0.75°] glidepath,
with green and flashing green above and red and flashing
red below. Signal width 24°.
helicopter lane Safety air corridor reserved for helicopters
(DoD, NATO).
helideck Operating platform for helicopters, e.g. on oil
rig.
helidrop Discharge of passengers/cargo/weapons while
hovering.
heliocentric Centred on the Sun.
heliopause Frontier beyond which Sun has little or no
influence.
Helios Helicopter instrument and operational procedures
simulator.
heliosphere Region of solar influence.
heliosynchronous Satellite orbit inclined at 90° to give
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