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hi
hi Flight at tropopause or above, adopted by gasturbine
combat aircraft flying for range outside hostile
environments.
HIA Held in abeyance.
HIADC High-integration air-data computer.
HIAL 1 High-intensity approach lighting; S adds
system.
2 Highlands & Islands Airports Ltd [Inverness IV2 7JB]
(UK).
HIAPER, Hiaper High-performance instrumented [or
instruments] airborne platform for environmental
research (NCAR).
HIB Helicopter identification by [AT adds acoustic
techniques Hibat, IRD adds IR detection Hibird, RAD
adds radar detection Hibrad].
hibernate To remain on station in space or in orbit with
as many subsystems as possible switched off until reactivated
by Earth command.
Hibird Helicopter identification by IR detection.
Hibrad Helicopter identification by radar detection.
HIC Head impact criteria.
Hi-camp Highly calibrated aircraft measurements
program (Darpa).
Hicar Acrilonitrile to DTD.5509.
Hi-CAT CAT above 55,000 ft (16.8 km).
HICT Hand-held imaging communications terminal.
HICU HIPSS interface control unit.
Hidar High instantaneous dynamic acoustic range.
Hidas Helicopter integrated defensive-aids system, or
suite.
hide Locally constructed aircraft shelter of posts, net
and camouflage.
Hidec Highly integrated digital engine [or electronic]
control.
HIDL High-integrity data-link (UAV).
HIDSS Helmet integrated display sighting [or and
sight] system.
Hiduminium Family of duralumin-type alloys, including
RR (Rolls-Royce) formulations, often also containing
nickel and iron; developed for piston engine pistons and
similar applications, also used in supersonic airframes (in
Concorde also known by French designations such as
AU2GN).
Hidyne See Hydyne.
HIE Helicopter-installed equipment.
Hi-Ex High-expansion [typically volume factor of
1,000] firefighting foam.
HIF Horizontal integration facility (space launchers).
Hifast High-frequency active suppression technology.
HIFR Helicopter in-flight refuelling from ship, also
rendered hover in-flight refuelling.
HIG, Hig Hermetic integrating gyroscope.
HIGE Hover[ing] in ground effect.
Higger High-integrity GPS guidance enhanced receiver
(blind STOVL).
high Region of high atmospheric pressure, anticyclone.
high altitude 1 Above 10 km (32,800 ft) (NATO).
2 Between 25,000 and 50,000 ft (7.6–15.2 km) (DoD).
High-altitude airship To remain geostationary at
70,000 ft (21.34 km) for six months (US).
high-altitude bombing Level bombing with release at
over 15,000 ft (4.57 km) (DoD).
high-altitude burst Nuclear weapon explosion at over
100,000 ft (30.5 km).
high-lift
high blower See high supercharger.
high boost Piston engine operated at high inlet-manifold
pressure, esp. one well above SL atmospheric pressure for
takeoff.
high boss Variable stator vane outer bearing.
high BPR Bypass ratio exceeding 5.
high-capacity bomb Large thin-case bomb for demolition
of major soft target.
high cloud Extremely loose classification, typical band
being 6–8 km (20,000–60,000 ft) in tropics, 5–13 km
(16,000–43,000 ft) in temperate, 3–8 km (10,000–26,000 ft)
polar. Always mainly ice crystals, Ci, Ce, Cs.
high compressor HP compressor (US).
high-cycle fatigue That due to high-frequency
vibrations, flexure or rotation of machinery, typically at
rate many times per second.
high-density focal-plane array EO sensor with thousands
of 2-D IR elements integral in substrate with CCD
readout and processing circuitry.
high-density rule Applied at four busy US airports to
limit arrival rates [from 1 Non. 04] (FAA).
high-density seating Normally, that giving greatest
practical number of passengers, more even than alleconomy,
tourist or other classifications.
high-density tunnel One having closed circuit filled with
air or other gas under pressure, power required for given
Mach/Reynolds combination being inversely proportional
to density.
high-energy laser No lasting definition; varies with
family, whether continuous, pulse or gated, and with
rapid progress, which by 1980 had made GW output not
uncommon.
higher harmonic control Reduction of helicopter stress,
noise and vibration by using dynamic absorption
methods.
high-flash fuel See Avcat.
higher heating value Gross calorific value of fuel.
high-flotation gear Landing gear having geometry and
other characteristics suitable for operation from soft soils,
sand and similar surfaces.
high-flotation tyre One of low inflation pressure and
very large contact area; not necessarily used on highflotation
gear.
high frequency See Appendix 2.
high-frequency pulse detonation Proposed propulsion
systems based on pulse detonation at frequencies not less
than 2 kHz, pioneered by Moscow State University.
high-gain aerial Usually means strongly directional,
designed to transmit or receive along single axis.
high gate Different meaning in different programmes
(lunar landing, air speed record runs, etc) but always a
specified rectangle in exact relation to surface of Earth or
other body through which vehicle must pass, often at
precise time, for mission to be successful (see gate [10,
11]).
high gear High supercharger gear.
high-incidence stall Unaccelerated symmetric stall at
highest angle of attack, normally with high-lift configuration.
high-inclination mission Usually means satellite inclination
from about 63° to 99° to Equator.
high-lift System, device, configuration or mode giving
lift greater than in clean or cruise configuration. Normal
* devices include leading-edge flaps, droops, slats,
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