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HTD
2 Heavy Transport Conversion Unit (RAF).
HTD Hard-target defeat.
H TD Wheel height at touchdown referenced to
depressed surface.
HTDU High-temperature demonstration unit.
HTFD Hard-target functional defeat.
HTI Horizontal technology integration.
HTIC House Transportation and Infrastructure
Committee (US).
HTIFT Hard-target influence-fuze technology.
HTK Hit to kill.
HTKP Hard-target kill probability.
HTL High-threshold logic.
HTLC High-temperature load calibration.
HTMPFG One of earliest of at least 35 Englishlanguage
safety acronyms = hood/harness, throttle/trim,
mixture, pitch, fuel/friction-nut/flaps, gills/gyros/possibly
goggles.
HTNS Helicopter tactical navigation system.
HTOVL Horizontal (conventional) takeoff, vertical
landing.
HTP 1 High-test peroxide.
2 High-tensile polyimide.
3 Horizontal tailplane.
HTPB Hydroxyl-terminated polybutadiene, rocket
propellant.
HTR Heat-transfer reduction.
HTS 1 High-tensile sheet (CFRP).
2 Harm targeting system.
3 Hydraulic test stand.
4 High-temperature superconductor.
5 High-temperature sensor.
HTSC High-temperature superconductor.
HTSF Hard-target smart fuze.
HTT Head, or helmet, tracker transmitter.
HTTB High-technology testbed (Lockheed).
HTU Hand-held terminal unit.
HTUFT Helicopter[s] taken up from trade, ie commandeered
[also Hetuft].
HTZ Helicopter traffic zone.
HU 1 Helicopter, utility (USN, USA, 1950-62).
2 Helmet unit, part of HMD(1).
hub 1 Strictly, those structural members required to
hold together blades of propeller or rotor; in practice
meaning has come to include all central portions,
including pitch and other mechanisms, de-icing and
instrumentation, but not spinner or other fairing.
2 Missile body section containing attachments for
cruciform wings.
3 Chief airport of major city.
4 Head office or largest plant of company.
hub and spoke Route pattern of carrier totally centred
on one city.
hubbed, hubbing Parked at hub (3).
hubbed loop An arbitrated loop in which the nodes are
arranged radially around a hub.
hub drive Driven by shaft input rather than tip jet reaction.
hub plane HP, in a helicopter the plane perpendicular to
the main-rotor shaft.
hub/tip ratio, H/T Ratio of radius at root of gas turbine
fan, compressor or turbine blade, to radius at tip (usually
inside tip shroud if fitted).
Hucks starter Device, often locally made, for starting
hung
piston engines. On a car or truck chassis a drive is taken
from the engine to a long shaft whose height and inclination
can be varied. This terminates in lateral pins [dog
clutch] which engage with a bayonet clutch on the end of
the propeller shaft (suggest obs.).
HUCP Highest useful compression pressure.
HUCR Highest useful compression ratio.
Hud, HUD Head-up display; C adds camera, or
computer, see next.
Hudwac HUD weapon-aiming computer.
Hudwass HUD weapon-aiming subsystem.
Hufford Family of large machine tools which grip
ductile sheet at each end in jaws on hydraulic rams
mounted on pivoting platforms and stretch it over male
die itself thrust forward on rams.
HUGS Head-up guidance system.
HULD Hardened unit-load device.
hull 1 Fuselage of flying boat.
2 Main body of rigid airship.
3 For insurance purposes, complete aircraft as defined
in policy, ignoring any load or persons on board.
hull insurance That covering capital value (assigned at
operative time, neither original first cost nor replacement
cost) of aircraft.
hull lines Set of plan views of LWLs of marine aircraft
or float.
hull loss Aircraft written off.
Hultec Hull to emitter correlation, EW/ESM software
programs.
HUM, Hum Health and usage monitor, or monitoring;
C adds computer, S adds system or and sensing, U unit.
human intelligence Gained by getting people ‘in the
know’ to disclose information, by whatever means.
human-operator describing function The transfer-function
model for the use of error information to track an
unpredictable target.
humidity Wetness of gas, esp. amount of water vapour
present in air; absolute * is mass of vapour in unit volume
g/m 3 , specific * is mass of vapour in unit mass of dry air
g/kg, relative is percentage degree of saturation = 100
times actual vapour pressure divided by SVP.
humidity mixing ratio Specific humidity.
Humint Human intelligence, ie countermeasures against
human decision-taking.
hump Region where, in takeoff of marine aircraft, T/W
–R/W is least; T is total thrust, W weight and R total resistance.
Point at which aerodynamic lift exceeds
hydrodynamic lift.
Humphrey cycle See constant-volume combustion.
hump speed That of marine aircraft (seaplane, flying
boat) or ACV at which total resistance of water is greatest;
in case of aircraft this speed [in US called V H ] is typically
about half V us .
Hums Health and usage (and performance) monitoring,
or management, system.
Hun 1 German aircraft or pilot (UK usage WW1,
occasional WW2).
2 Pupil pilot (colloq, RFC).
hundred per cent aircraft One that exactly measures up
to published performance.
hundredweight Non-SI unit of mass, abb. cwt = 112lb,
50.8023kg; in US [called short *, sh.cwt.] = 100 lb,
45.3592 kg.
hung Hung start.
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