Glossary of Aviation Terminology


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Laplace transform: A mathematical relationship to model a continuous function in the complex frequency domain (S-plane); Laplace transforms are commonly used by systems engineers to describe avionics systems; Compare: continuous-time equation, difference equation, differential equation, discrete-time equation, state-space model, Z transform; See Also: first-order filter, integrator, second-order filter, unit functions;

Laser obstacle avoidance / terrain avoidance sensor (OA/TA): A sensor that provides warnings for long, thin objects (like wires). It has at least a 20deg x 30deg FOV, which is both velocity tracked and pitch stabilized. It provides warnings (every 2.5 seconds) for long, thin obstacles (like wires) at 400 meters detection range and contour flight at 80-120 knots.

Lateral: Related to latitude; across an aircraft left to right

Lateral cue: A cue to control heading; lateral cyclic cue See Also: wheel cue,

Lateral cyclic: A flight control operated by moving left or right with hand in rotary-wing aircraft, primarily to control roll (heading); controls differential pitch of the rotors as they rotate from one side to the other on a rotary-wing aircraft;

Lateral cyclic cue: A lateral flight director cue for rotary-wing aircraft, primarily to control heading, by changing roll; Compare: wheel cue; Symbols: Gamma sub 'LAT'; Typical Units: percent,in;

Lateral guidance: Calculations for the lateral axis of the appropriate guidance modes. The control law lateral axis input data are: Cross Track Deviation, Cross Track Deviation Rate, Cross Track Deviation Rate Gain, Track Angle Error, Track Angle Error Gain, Course Cut Limit, Path Integral Limit, Path Integral Gain. The major output from Longitudinal Guidance is the speed error for the selected longitudinal guidance mode.

Latitude: Position on earth, north or south of the equator; See Also: astronomical latitude, geocentric latitude, geodetic latitude; Symbols: Phi; Typical Units: rad, deg;

Leg: A segment of a flight plan; flight path between two waypoints

LF ADF: Low Frequency Automatic Direction Finding

LOC: Localizer

Lift: Force, created primarily by wings (fixed wing) or by rotors (rotary wing), acting in opposite direction of gravity vector; Symbols: Length; Typical Units: lbf,kip; Dimensions: Mass * Length / Time-squared;

Limiter: A filter that passes the input to the output, except that the output is limited to a minimum value and a maximum value; Compare: rate limiter;

Localizer (LOC): Part of ILS that provides lateral deviations from a preset course;

Longitude: Position on earth, east or west of the prime meridian; Symbols: lambda; Typical Units: rad, deg;

Longitudinal: Related to longitude; lengthwise along the center line of an aircraft forward

Longitudinal cue: A cue to control pitch; longitudinal cyclic cue See Also: throttle cue,

Longitudinal cyclic: A flight control operated by moving fore or aft with hand in rotary-wing aircraft, primarily to control pitch (speed); controls differential pitch of the rotors as they rotate from nose to tail on a rotary-wing aircraft;

Longitudinal cyclic cue: A longitudinal flight director cue for rotary-wing aircraft, primarily to control speed, by changing pitch; Compare: throttle cue; Symbols: Gamma sub 'LONG' ; Typical Units: percent,in;

Longitudinal guidance: Calculations for the longitudinal axis of the guidance modes. The control law longitudinal axis input data are: Reference Acceleration, Reference Acceleration Gain, Desired Velocity, Velocity Error Scale Factor. The major output from Longitudinal Guidance is the speed error for the selected longitudinal guidance mode.

Low Frequency Automatic Direction Finding (LF ADF): Equipment that determines bearing to a radio station on a low frequency band, usually the standard AM band;

Low-pass filter (LPF): A filter that allows frequencies below a cutoff frequency to pass while attenuating frequencies above the cutoff frequency; See Also: first-order filter;

LPF: Low-pass filter


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