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

TRN-INS.
TRN with INS

TRN.
Terrain Referenced Navigation;

True airspeed (TAS).
Airspeed corrected for instrumentation errors and air density; See Also: airspeed; Symbols: V sub 'TAS'; Typical Units: kt,ft/s; Dimensions: Length / Time;

True bearing.
Symbols: B sub T; Typical Units: rad, deg;

True heading.
Heading of the aircraft relative to true north; Symbols: psi sub T; Typical Units: rad, deg;

True track.
Ground track angle; Symbols: T sub T; Typical Units: rad, deg;

True.
Best available estimate, such as true airspeed; referenced to true north, such as true heading;

Tune.
To set the operating frequency or channel for a device

Unit functions.
A collection of functions used as standard test cases in control systems engineering; The primary unit functions of interest in avionics are the unit impulse, the unit step, and the unit ramp. Symbols: u sub k ( t );

Unit impulse.
A function used as a standard test case in control systems engineering; a spike of ``area'' one at time t = 0; Synonyms: impulse; See Also: unit functions; Symbols: u sub <0> ( t ), delta ( t );

Unit ramp.
A function used as a standard test case in control systems engineering; a line of slope 1 starting at zero at time t = 0; Synonyms: ramp; See Also: unit functions; Symbols: u sub < -2> ( t );

Unit step.
A function used as a standard test case in control systems engineering; a step from zero to one at time t = 0; Synonyms: step; See Also: unit functions; Symbols: u sub< -1>( t ), u( t );

Unitless.
No units, such as ratios; a quantity with standard units of 1; a quantity with primary units of 1; Synonyms: dimensionless;

Units.
A standard quantity, such as ft or mi; Synonyms: dimension;

Update.
A process by which position is reset with a known better position; updates occur at the data source level or at the physical device level, depending upon specific implementation of the device and the data source (choice of implementation is transparent above the data source); all updates are operator initiated, but the new position may be derived f...

UTM.
Universal Transverse Mercator

Velocity east.
Aircraft velocity in true east direction; Symbols: V sub E; Typical Units: kt, ft/s; Dimensions: Length / Time;

Velocity error scale factor (KVSF).
A guidance control law parameter, generated by the longitudinal guidance modes;

Velocity north.
Aircraft velocity in true north direction; Symbols: V sub N; Typical Units: kt,ft/s; Dimensions: Length / Time;

Velocity.
Rate of change of location, either scalar or vector, often with subscripts such as ENU or XYZ to denote the coordinate frame; time derivative of position; time integral of acceleration; Symbols: v,V; Typical Units: kt,ft/s; Dimensions: Length / Time;

VERT SPD.
Vertical speed hold

Vertical acceleration.
Aircraft acceleration in earth vertical direction; Symbols: A sub V; Typical Units: ft/s-squared,g; Dimensions: Length / Time-squared;

Vertical cue.
A cue to control altitude; See Also: yoke cue, collective cue;

Vertical guidance.
Calculations for the vertical axis, rather than the longitudinal axis. The control law vertical axis input data are: Desired Altitude, Altitude Integral, Altitude Integral Gain, Altitude Integral Limit, Altitude Error Scale Factor, Magnitude limit for delta altitudes. The major output from Vertical Guidance is the altitude error for the selected ve...

Vertical speed hold (VERT SPD).
A basic guidance mode, providing vertical guidance to maintain an operator selected vertical speed;

Vertical velocity.
Aircraft velocity in earth vertical direction; Symbols: V sub V; Typical Units: ft/s; Dimensions: Length / Time;

Vertical.
Reference to earth radial, for example, vertical velocity is velocity along earth radial; See Also: East-North-Vertical;

VHF Omnirange (VOR).
Equipment that determines bearing to a radio station with a VOR transmitter; VOR transmitters usually contain ILS transmitters in addition to VOR; A basic guidance mode, providing lateral guidance to a VOR station. A VOR/ILS/MB. radio receiver provides a VHF Omni-Direction Range (VOR) function and Instrument Landing System with Marker Beacon (MB) f...

VOR.
VHF Omnirange;

VORTAC.
Collocation of VOR and TACAN providing distance and bearing to station; a basic guidance mode, providing lateral guidance to a set of a VOR station and a TACAN station that are collocated

Warning, Caution, Advisory (WCA).
See: warning, caution, advisory, annunciator, alert;

Warning.
A signal which alerts the operator to a dangerous condition requiring immediate action (from MIL-STD-1472D); an annunciator that is the most critical (more than an advisory or a caution); Also, an indicator of potential failure soon; Values: none, hot, low-power, high-power, other;

Wash-out filter.
A filter to smooth a transition due to change of input source, such as when changing modes; See Also: transient-free switch;

Waypoint (WYPT).
A point on the ground, predefined as a point of interest for the flight; a basic guidance mode, providing lateral guidance to a waypoint, either by course or by direct (operator selectable);

Waypoint approach.
To approach a waypoint

WCA.
Warning, Caution, Advisory

Weight on wheels (WOW).
Indication of whether the aircraft has weight on its wheels, meaning airborne or on the ground; weight on wheels can be detected by a sensor on the wheels, computed from other state data, or a combination;

WGS72.
World Geodetic Survey 1972

WGS84.
World Geodetic Survey 1984

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

Wheel.
A flight control operated by turning with hands in fixed-wing aircraft, primarily to control roll (heading) via the ailerons; wheel is connected to yoke;

Wind bearing.
Symbols: B sub W; Typical Units: rad, deg;

Wind speed.
Symbols: V sub W; Typical Units: kt,ft/s; Dimensions: Length / Time;

World Geodetic Survey 1972 (WGS72).
A standard model for computing earth data;

World Geodetic Survey 1984 (WGS84).
A standard model for computing earth data;

WOW.
Weight on wheels

Wrap test.
A test to send data to a device having it sent back unaltered

WYPT.
Waypoint

XTKD.
Crosstrack deviation

XTKR.
Crosstrack deviation rate

XYZ.
A standard aircraft coordinate frame and sign convention, where nose, right wing, and down are positive X, Y, and Z, respectively; often used as subscripts; Compare: east-north-up;

Yaw rate.
Rate of change of yaw; time derivative of yaw; Symbols: r; Symbols: psi dot; Typical Units: rad/s, deg/s; Dimensions: 1/Time;

Yaw.
Angle of heading; Symbols: psi,Psi; Typical Units: rad, deg;

Yoke cue.
A vertical flight director cue for fixed-wing aircraft, primarily to control altitude, by changing pitch; Compare: collective cue; Symbols: Gamma sub VERT; Typical Units: percent,in;

Yoke.
A flight control operated by pushing and pulling with hands in fixed-wing aircraft, primarily to control pitch (altitude) via the elevators; yoke is mounted on a column between the operator's legs, positioned much like a steering wheel in a car; yoke control is achieved by pushing and pulling the wheel to move the column (yoke) fore and aft;

ZOC.
Zone of confusion

Zone of confusion (ZOC).
A circular area centered at a TACAN station in which bearing is extremely noisy

S-plane.
Continuous complex frequency plane; S-plane is used in control systems engineering in the design of control laws See Also: Laplace transform;

Z-plane.
Discrete complex frequency plane; Z-plane is used in control systems engineering in the design of control laws See Also: Z transform;

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