Aviation Maintenance Terms beginning with H

H/L

High/Low

HAE

Height Above Ellipsoid

HAG

Height Above Geoid

HEA

High-frequency Radio Antenna

HF (hf)

High Frequency (3 to 30 MHz)

HFCP

High-frequency Radio Control Panel

HFOM

Horizontal Figure of Merit

HI Z

High Impedance

HIL

Horizontal Integrity Level

HPL

Horizontal Protection Level

HRD

High-rate-discharge.

HRD fire extinguisher

A fire extinguisher that carries the extinguishing agent in a sealed sphere or cylinder. When the agent-discharged switch is closed, an ignited powder charge drives a cutter through a frangible disc which releases the agent. The entire contents of the container is emptied in much less than a second.

HSI

Horizontal situation indicator.

HUL

Horizontal Uncertainty Level

HZ

Hertz

Hz