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h ant
h ant Height of ILS or MLS antenna above ground plane.
HANZ Helicopter Association of New Zealand.
HAP Hélicoptère d’appui et de protection (F).
Hapdar Hardpoint demonstration array radar.
HAPI, Hapi Helicopter approach-path indicator.
Happ High-altitude powered platform, lightweight,
solar-powered, unmanned aircraft able to hold station for
months to years.
Haps 1 Helmet-angle position sensor.
2 Helicopter acoustic processing system.
HAR 1 Helicopter, air rescue (role prefix, UK).
2 Helicopter alternative route.
harass 1 Air attack on any target in area of land battle
not connected with CAS or interdiction, with objective of
reducing enemy’s combat effectiveness.
2 To interfere with progress of another aircraft by
making repeated close passes against it.
Harc jet Hall-effect arc jet, using magnetic field on
hydrogen plasma jet (see Hall).
Harco Hyperbolic area-coverage.
HARD Helicopter and aeroplane radar detection.
hard copy Immediately readable output, eg printed
pages, as distinct from tape, microfilm or software.
hard data Remains in memory when power switched off.
hard deck The ground, especially in air combat at low
altitude.
hardened 1 Protected against blast, ground shock, overpressure,
EMP, radiation and possibly other effects of
nuclear explosion, and (DoD only) likely to be protected
against chemical, biological or radiological attack (see
hardness).
2 More recently, protected against terrorist attack, eg
cockpit or LD3 container.
3 Of avionics, protected against EMP and any other
powerful external EM effects which in particular would
normally degrade or destroy most memory cores.
4 Of metal, physically * by precipitation, quenching or
cold working.
hard flutter Normally well damped but extremely
violent over one narrow range of conditions.
hard intervals Precisely scheduled service/overhaul
periods, as distinct from on-condition.
hard intervals Precisely scheduled service/overhaul
periods, as distinct from on-condition.
hard-iron magnetism That induced into all magnetic
parts of aircraft during manufacture, esp. by hammering
or riveting, orientation and polarity depending on
assembly heading and terrestrial latitude.
hard lander Spacecraft designed to free-fall to surface of
heavenly body.
hard landing 1 Conventional aircraft landing with excessive
rate of descent, esp. that results in damage or
overstressing.
2 Arrival of hard lander on lunar/planetary surface.
hardness 1 Various measures of physical * such as
Moh’s scale for non-engineering (eg geological) materials,
and Rockwell, Vickers, Brinell and many other standard
tests for precise quantified readings.
2 Any of five measures of nuclear hardening; eg resistance
to overpressure, which varies from c 2 lb/sq in
(c 14 kPa) for aircraft parked in open to over
11,000 lb/sq in (c 75 MPa) for hardest concrete silo.
hardover runaway Sudden unwanted operation of
harmonization
system, esp. flight-control channel, to extreme limit of
travel.
hardover signal Fault condition resulting in full demand
for unidirectional system operation unrestrained by
normal feedback.
hardpoint Anchorage built into aircraft structure for
heavy external load, usually via intermediate pylon, MER
or launcher.
hard radiation High penetrating power from very shortwavelength;
usual definition is ability to pass through
100 mm of lead.
hard recovery Landing under difficulties, eg barrier
crash into net in bad weather with tower out of action
(probably colloq.).
hardstanding Paved parking area (US, often hardstand).
hard target 1 One that is hardened (1).
2 In air-to-air or surface-to-air firing practice, a rigid
drone, as distinct from a sleeve or banner.
hard-target functional defeat Use of air/ground weapons
to disable deeply buried installations without necessarily
killing humans.
hard temper Modification of light-alloy properties, eg
by cold working, denoted by scale such as 3/4H (= 75%
fully hard); increased tensile strength is usually accompanied
by reduced ductility, which in airframes tends to
be equated with shorter fatigue life.
hard time Period, usually an inspection interval, precisly
written into service/overhaul documentation and mandatory.
Today increasingly replaced by flexible routines
such as OCM.
hardtop Paved with permanent all-weather surface.
hard turn Planned turn in air combat at rate governed by
angle-off and range.
hard vacuum High vacuum, pressure below 10 -9 Nm -2
(10 -7 torr).
hardwall hose Does not collapse under atmospheric
pressure when used for suction; not necessarily armoured.
hardware 1 Originally introduced to distinguish
mechanical parts of EDP (1) systems from software, today
useful to imply manufactured items of any kind that exist,
as distinct from software, system concepts, paper designs
and proposals, simulations, capabilities and functions.
2 In narrow sense, small fasteners and similar small
parts.
hardware in the loop Flight-motion simulation system
incorporating portions of actual aircraft dynamics.
hard wing 1 One with simplified leading edge compared
with particular previous wings, eg no slat.
2 Any wing with fixed-geometry leading edge.
3 In combat mission, wing man locked-in to follow
leader in (almost) all circumstances.
Harm, HARM High-speed anti-radiation missile.
Harmattan Dry, dust-filled NE wind (W Africa).
harmonic Component of sinusoidal or complex waveform
or tone whose frequency is integer multiple of
fundamental frequency.
harmonic analyser Device, typically variable-frequency
filter, which can resolve waveform into harmonic
constituents.
harmonization 1 Boresighting of all guns fixed to fire in
same basic direction (eg ahead) so that all are correctly
aligned with respect to aircraft axes, usually so that all gun
axes converge at specified distance from aircraft.
2 Adjustment of flight-control system so that effect of
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