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OSWEGO - Avionics Dictionary Category: Electronics and Engineering > Avionic terms Date & country: 11/08/2008, USA Words: 560

FLIR.
Forward-Looking Infrared

Flux valve.
A device to measure the earth's magnetic flux; a compass

Fly over.
A position update by flying directly over a known point

Forward-Looking Infrared (FLIR).
Sensor equipment used to supplement AGR, extend the aircraft visual search capability and provide position information for guidance and navigation update capability. Imagery derived from the FLIR sensor is displayed in the cockpit. FLIR pointing can be controlled manually using a tracking handle or automatically by the Mission Computer. FLIR conver...

FPA.
Flight path angle

GA.
Go around

Gaussian radius of curvature.
Radius of the earth for the best fitting sphere at a given position; Synonyms: earth radius best sphere; Symbols: rho sub G; Typical Units: ft; Dimensions: Length;

GCLP.
Guidance control law parameter

Geocentric latitude.
Latitude measured with respect to horizontal through mass center of the earth; Compare: astronomical latitude, geodetic latitude; Symbols: Phi sub C; Typical Units: rad, deg; Reference: Kayton69. page 16

Geodetic latitude.
Latitude measured with respect to normal to reference ellipsoid; Compare: astronomical latitude, geocentric latitude; Symbols: Phi sub T; Typical Units: rad, deg; Reference: Kayton69. page 16

Gimbaled inertial sensor.
Accelerometers mounted to a platform which is free to rotate, with gyroscopes to measure rotation and servomotors to maintain a fixed attitude with respect to the earth Compare: strapdown inertial sensor;

Glideslope.
Angle approach a runway; Symbols: Gamma; Typical Units: rad, deg;

Global Positioning System (GPS).
A navigation sensor based on satellites; A Global Positioning System (GPS) provides highly accurate navigation data: position, velocity, and time reference. GPS is often aided by the INU, AHRS, and Doppler data. GPS is accurate with four or more properly oriented satellites. Accuracy is degraded with improperly placed satellites or fewer than four ...

Go around (GA).
A basic guidance mode, providing lateral guidance, longitudinal guidance and vertical guidance to climb then to accelerate, while maintaining a wings-level roll; in some implementations (such as SOA), individual axes can be overridden by other modes (for example, longitudinal with G/S SEL and vertical with RALT SEL or BALT SEL)

GPS-DNS.
GPS using DNS

GPS-INS.
GPS using INS

GPS.
Global Positioning System

Gravitational acceleration.
Acceleration caused by the force of gravity; Symbols: g; Typical Units: ft/s-squared,g; Dimensions: Length / Time-squared;

Gravity.
Force exerted by gravity; gravity sometimes includes effects of the earth's rotation; gravity is often treated as a constant, but for greater accuracy gravity is a function of latitude, altitude, and the phase of the moon (yes, it's true); Symbols: g; Typical Units: lbf,kip; Dimensions: Mass * Length / Time-squared;

Grid north.
Standard aviation term.

Grivation.
Symbols: nu sub g ; Typical Units: rad, deg;

Ground track angle (GTA).
Direction of ground speed vector with respect to true north; Synonyms: true track; Symbols: eta; Typical Units: rad, deg;

Groundspeed select (G/S SEL).
A basic guidance mode, providing longitudinal guidance to an operator selected groundspeed;

Groundspeed.
The speed over the ground; earthspeed projected to a horizontal plane; Symbols: V sub g; Typical Units: kt,ft/s; Dimensions: Length / Time;

GTA.
Ground track angle

Guidance.
System, usually software, that determines state errors of desired state minus current state, typically three states: heading, altitude, and speed;

Gyroscope (gyro).
An inertial device for measuring change of attitude (pitch rate, roll rate, and yaw rate); gyroscopes usually consist of a gimbled, rotating mass; gyroscopes are usually included in inertial sensors, such as AHRS and INS; See Also: ring-laser gyro;

HDG SEL.
Heading select

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);

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

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 .....

IAS.
Indicated airspeed

IBC.
Ils Back Course

IBIT.
Initiated built-in-test

IDS.
Infrared Detecting Set

ILS approach.
To approach a runway using ILS

ILS Back Course (IBC).
Operation of ILS in which the runway is approached in reverse direction, giving only lateral guidance; Compare: ILS Front Course;

ILS Front Course.
Operation of ILS in which the runway is approached in forward direction, giving lateral, longitudinal, and vertical guidance; sometimes called ILS Compare: ILS Back Course;

ILS.
Instrument Landing System

Indicated airspeed (IAS).
Airspeed as instruments would indicate, not corrected for instrumentation errors or air density; See Also: airspeed; Symbols: V sub 'IAS'; Typical Units: kt,ft/s; Dimensions: Length / Time;

Inertial Navigation System (INS).
An Inertial Navigation System (INS) is a self-contained navigation system. It consists of gyroscopes and accelerometers to provide attitude, heading, position, attitude, body/inertial velocity, and acceleration information. A primary navigation data source. INS loses accuracy with time due to drift of gyroscopes. INS-DNS is moderately accurate over...

Inertial Navigation Unit (INU).
A self-contained Inertial Navigation System;

Inertial.
Based on inertia, such as with an INS or an AHRS

Infrared Detecting Set (IDS).
Forward-Looking Infrared;

Initialization.
A basic control to a data source from controls and displays for initializing a device. Initiated by power-on, operator, driver, or MC; During initialization, the device is usually not available; Also, a procedure to reset physical devices to a known state; Values: initialization in progress, not initialized, unreliable, normal, redundant, degraded,...

Initiated built-in-test (IBIT).
Selftests running internal to a device initiated external to the device, usually an operator, causing the device to temporarily cease normal operation; Compare: periodic built-in-test;

Inner marker.
Innermost marker beacon on an ILS

INS.
Inertial Navigation System

Instrument Landing System (ILS).
Equipment determining glideslope, localizer (bearing), and distance (marker beacon) to a runway; ILS provides precision aiding for landing; ILS is usually part of a VOR station. A basic guidance mode, providing lateral guidance, longitudinal guidance, and vertical guidance to approach a runway for landing; in ILS back course, vertical guidance is n...

Instrumentation.
Hardware to measure and to monitor a system

Integrate.
To combine multiple systems; Also, to compute to integral of;

Integrator.
A function that integrates; Many types of integrators exist; in fact, they constitute entire books. Avionics software usually relies on rectangular, single integrators, but occassional uses trapezoidal or double integrators.

International.
A standard model for computing earth data

Interpolate.
Function to determine intermediate values from two or values in a table; usually linear but can be higher order; endpoints are either extrapolated or limited;

Interrogation.
A request of data

INTLIM.
Path integral limit

INTMAGLIM.
Altitude integral limit

INTVAL.
Path integral value

INU.
Inertial Navigation Unit

Invalid.
An indication that data from a device is bad and cannot be trusted

Jerk.
Rate of change of acceleration, either scalar or vector, often with subscripts such as ENU or XYZ to denote the coordinate frame; time derivative of acceleration; Symbols: j,J; Typical Units: ft/s-cubed; Dimensions: Length / Time-cubed;

Kalman filter.
A filter for combining multiple data sources, usually of different types, to produce an estimate better than any single source; Compare: averaging filter, complementary filter;

KALTINT.
Altitude integral gain

KINT.
Path integral gain

KLA.
Reference acceleration gain

KTAE.
Track angle error gain

KVSF.
Velocity error scale factor

KXTKD.
Crosstrack deviation gain

KXTKR.
Crosstrack deviation rate gain

KZSF.
Altitude error scale factor

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 fil...

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

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 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 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...

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

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

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;

LOC.
Localizer

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 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.

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

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