| Acronym |
Definition |
| H24 |
Continuous round-the-clock operation. Also :- HN, HJ, HO |
| HJ |
Operates during day. |
| HN |
Operates during night. |
| HO |
Operates during times to meet operational requirements. |
| HX |
No specific operational hours. |
| HAA |
Historic Aircraft Association. |
| HAI |
Helicopter Association International. |
| Half-mill(ion) |
1:500000 scale ICAO aeronautical chart. |
| HDG |
Heading. The direction in which an aircrafts nose points in flight in the horizontal plane expressed in compass degrees. |
| Heavy |
Suffix used in RT callsigns to indicate that the aircraft is a large transport alerting controllers and following aircraft to the possibility of wake turbulence (which see). |
| Hectopascal (hPa) |
Unit of pressure measurement. |
| HEMS |
Helicopter Emergency Medical Services. |
| Hertz |
Standard radio equivalent of frequency in cycles per second. |
| HF |
High-Frequency Band. |
| Hg |
Inches of mercury a unit of pressure measurement. |
| HIAL |
High Intensity Approach Lighting. |
| HIRF |
High Intensity Radiated (Electromagnetic) Fields. |
| HIRL |
High Intensity Runway Lighting. |
| HISL |
High Intensity Strobe Light. |
| Holding Pattern |
Set path which keeps aircraft within a specified airspace while awaiting further clearance from air traffic control. |
| Hot-And-High |
Airfield conditions of high altitude and high ambient temperatures. |
| HOTAS |
Hands On Throttle And Stick. |
| HRA |
Highlands Restricted Area |
| HSI |
Horizontal Situation Indicator. A cockpit navigation display combining navigation and heading. |
| HUD |
Head-Up Display. Aircraft data projected on to the pilots aircraft windscreen. |
