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hack
Halon
to same reduction in brightness, and various characteristics
hack 1 Aircraft informally used as general transport and
Hafnium Hf, corrosion-resistant silver metal, density half-reverse Cuban Aerobatic manoeuvre: two left rolls
13.3, MPt 2,230°C, * carbide and * nitride MPts are well up up-45 line, two flick rolls to right, increase trajectory
beyond 3,000°C.
to vertical to zero airspeed, tailslide followed by other
HAGB Helicopter Association of Great Britain.
manoeuvres on down-45.
Hagen-Poiseuille Law for velocity or pressure drop per half-roll Rotation of aircraft sensibly about longitudinal
unit length for pure streamline (laminar) flow in constantsection
pipe. Equal to u = ––– (a 2 r 2 )
axis through 180°, usually from upright to inverted attitude
or vice versa; can be half of barrel roll or of slow roll.
P
4 Thickness of absorbing medium which
μ
transmits half intensity of radiation incident upon it.
where u is local velocity, P pressure drop per unit length, halftone screen Fine opaque grating usually scribed on
μ coefficient of viscosity, a radius of tube, and r radius at glass to break up photographic image into halftone dot
point concerned. Equation denotes parabolic velocity pattern, for printing or digitising purposes.
distribution.
halftone tube CRT containing conventional gun for
HAGR High-gain advanced GPS receiver.
writing separated from screen by fine-mesh electrode and
HAH Hot and high.
storage plate.
HAHO, Haho High-altitude high-opening.
half-view Drawing showing half a symmetrical object.
HAHS Hibernian Aviation Historical Society [office half-wave rectification Use of single-phase rectifier
Dublin].
which passes only half of each alternate wave from input.
HAHST High-altitude high-speed target.
Hall effect When current-carrying material is subjected
HAHV, HaHv Haute altitude, haute vitesse.
to magnetic field (or when conductor is moved through
HAI Helicopter Association International [office, magnetic field) potential difference is set up perpendicular
Alexandria, VA22314–2818] (US, Int.).
to both current (or motion) and field; small in metals but
HAIL Highlands and Islands Airports plc (UK).
important in semiconductor systems and in study of electricity
in ionosphere. Since 1990 the operating principle of
hail Precipitation in form of hard or soft ice pellets,
utility vehicle by military unit (often captured from enemy
of storage tubes and displays.
or retired from combat duty).
half chat Vaguely, any partial power setting [colloq.].
2 To be able to accomplish (military/RAF, transative, half-Cuban Aerobatic manoeuvre consisting of up-45
colloq.).
3 To penetrate private network, especially a secure
line, half-roll followed by remainder of loop [many variations
and additions].
LAN.
half glidepath ILS glidepath within points at which
HACP High-altitude communications platform DDM is 0.0875.
[unmanned airships].
half-life Time required for decomposition of half original
HACS Helicopter armoured crashworthy seat.
mass or number of atoms of radio-active material.
HACT Helicopter active-control technology.
half-mil[lion] Aeronautical chart series on scale
HAD 1 Hybride analog/digital.
1:500,000 (ICAO).
2 Hélicoptère d’Appui-Destruction (F).
half-period zone See Fresnel zone.
3 Hardware architecture document.
half-power points, rings Points, whose locus is normally
Hadas Helmet airborne display and sight.
closed ring, where radiated power from antenna is half
Hadec Highly-adaptive digital engine control.
lobe maximum.
HADF High-accuracy direction finder.
half-power width Total angle at antenna between two
HADS 1 High-accuracy digital sensor.
opposite half-power points measured in plane containing
2 Helicopter air-data system.
lobe peak.
HAE High-altitude endurance.
half-residence time Time for quantity of delayed fallout
HAF Hellenic air force [UK usage].
(weapon debris) deposited in particular part of atmosphere
HAFFS Heliborne aerial firefighting system.
to decrease to half original value.
varying size; maximum for certification test is usually 1 in some space thrusters.
(25.4 mm) sphere.
Halo 1 High-altitude, low-opening (paradrop system).
HAILSS Helicopter aircrew integrated lift-support 2 High-altitude large optics.
system.
3 High altitude [or agility], low observable.
HAINS, Hains High-accuracy INS.
4 Hypersonic air-launched option.
Hair High-altitude IR.
5 High altitude, long operation.
hair absorber Family of RAM (2) coatings consisting of halo 1 Any of several species of part-circular
dense mats of hair with conductive coatings, eg carbonblack
in neoprene.
phenomena caused by ice crystals in upper atmosphere,
chief of which is 22° radius around Sun or Moon.
hairline crack One in which the two sides are in close 2 Coloured ring or disc seen on cloud in direction away
contact, hence inconspicuous to eye.
from Sun, ie with aircraft shadow at centre; also called
HAISS High-altitude IR sensor system.
pilot’s *.
HAL 1 Height above landing [on helicopter pad].
3 Reflection of cockpit instrument seen in canopy at
2 Host accessory logic.
night.
Hale, HALE High-altitude, long-endurance.
halo effect Ability of SST service to generate or attract
half-brightness life Used in several senses, eg time from additional first-class subsonic traffic to same carrier on
cutoff of stimulating radiation of phosphor to luminescence
same route(s).
falling to half peak, time of cutoff of current to LED Halon Family of halogen-based fluids, mainly
BCF,
309