Glossary of Aviation Terminology


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HDG SEL: Heading select

Heading: Direction on a compass that aircraft is pointed, measured with respect to true north or magnetic north; Symbols: psi; Typical Units: rad, deg;

Heading error: A basic output from guidance to flight director, indicating the difference between actual heading and desired heading; Symbols: DELTA psi; Typical Units: rad, deg;

Heading select (HDG SEL): A basic guidance mode, providing lateral guidance to an operator selected heading (magnetic heading or true heading, again, operator selectable);

Health: Equipment status

High-pass filter (HPF): A filter that allows frequencies above a cutoff frequency to pass while attenuating frequencies below the cutoff frequency;

Hold: To maintain some aspect(s) of aircraft state, such as heading, airspeed, altitude, pitch

Hook: In the US Navy, a target cursor;

Hough: A standard model for computing earth data

Hover hold (HVR SYM): A basic guidance mode, providing lateral guidance and longitudinal guidance to maintain an operator selected north velocity and east velocity; if the selected velocities are zero, then a position is held

HPF: High-pass filter

HVR SYM: Hover hold

Hysteresis: A function in which the algorithm for computing output changes at defined events or thresholds, such that output follows one path as input increases and another path as input decreases; Hysteresis can be formalized: (0) at initialization, select algorithm-0 (1).if event-1 occurs, switch to algorithm-1 (2) if event-2 occurs, switch to algorithm-2 ... (N) if event-n occurs, switch to algorithm-n Frequently in avionics, hysteresis prevents a test from oscillating near the transition point due to noise. Implementation is usually: (0) at initialization, set y = 0 (1) if x sub c + h/2 le x, then set y = 1 (2) if x sub c - h/2 lt x lt x sub c + h/2, then let y retain its value (3) if x le x sub c - h/2, then set y = 0


A , B , C , D , E , F , G , H , I , J - K , L , M , N , O , P , Q - R , S , T , U , V, W, X - Z