Glossary — H

h Hour(s).

HAC Helicoptere Anti-Char (anti-tank helicopter), version of Tigre/Tiger.

HAL Hindustan Aeronautics Limited (India).

HAMC Harbin Aircraft Manufacturing Corporation (China).

handed Rotating in opposite directions.

HAP Helicoptere d’Appui et de Protection (escort/fire support helicopter), version of Tigre/Tiger.

hardened Protected as far as possible against nuclear explosion.

hardpoint Reinforced part of aircraft to which external load can be attached, for example weapon or tank pylon.

HARM High-speed Anti-Radar[/Radiation] Missile (US designation AGM-88).

HAS Helicopter Anti-Submarine (UK designator).

HC Helicopter Cargo (UK designator).

HCP Helicoptere de Combat Polyvalent (multirole combat helicopter) applied to Tigre/Tiger.

HDD Head-down display (which see).

HDU Hose-drum unit.

head-down display On the cockpit instrument panel (as distinct from a HUD).

head-level display Immediately below HUD.

helicopter Rotary-wing aircraft both lifted and propelled by one or more power-driven rotors turning about substantially vertical axes.

HF High frequency.

HIFR Helicopter in-flight refuelling.

HIRF High-intensity radiated field(s).

HMA Helicopter, Maritime Attack (UK designator).

HMD Helmet-mounted display; hence HMS = sight.

HMMWV High-Mobility Multi-purpose Wheeled Vehicle. Aka Humvee.

HOCAC Hands on cyclic and collective.

homebuilt Aircraft built/assembled from plans or kits.

HOT Haut subsonique Optiquement teleguide tire d’un Tube (subsonic optically-tracked tube-launched). French acronym for an anti-tank missile.

hot-and-high Adverse combination of airfield height and high ambient temperature, which lengthens required take-off distance.

HOTAS Hands on throttle and stick.

hot refuelling Replenishment of fuel while engine(s) running.

hovering ceiling Ceiling of helicopter (corresponding to air density at which maximum rate of climb is zero), either GE or OGE.

HP High pressure (HPC, compressor; HPT, turbine).

hp Horsepower, non-SI unit of power. Equal in the United Kingdom to 550 foot-pounds per second and in the United States to 745.7 watts.

HSA Hawker Siddeley Aviation (UK).

HSI Horizontal situation indicator.

HUD Head-up display (bright numbers and symbols projected on pilot's aiming sight glass and focused on infinity so that pilot can simultaneously read display and look ahead). The term is increasingly rendered in the USA as "heads up", which is incorrect.

Hz Hertz, cycles per second.