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

Continuous-time equation.
A mathematical relationship to describe a function of time, expressed in terms of continuous time; Compare: difference equation, differential equation, discrete-time equation, Laplace transform, state-space model, Z transform; See Also: first-order filter, second-order filter, unit functions for examples;

Control law.
The mathematical definition of a system used to control or to change the dynamic response of a system;

Control surface.
An airfoil attached to an aircraft that is moved to control the attitude of the aircraft; an surface to control flight of an aircraft indirectly, such as a swashplate to control pitch of rotor blades; See Also: aileron, rudder, spoiler, elevator, flaps, trim tab, stabilizer; Symbols: delta; Typical Units: rad, deg;

Controlled altitude (CTALT).
A guidance control law parameter, generated by the vertical guidance modes; altitude that is being controlled Typical Units: ft; Dimensions: Length;

Controlled speed (CTS).
A guidance control law parameter, generated by the longitudinal guidance modes; speed that is being controlled Typical Units: ft/s, kt; Dimensions: Length / Time;

Coriolis acceleration.
Tangential acceleration caused by motion on a radial on a rotating surface, in aviation, it is acceleration in the earth's longitudinal direction caused by changing latitude, usually computed from system state data; Symbols: a sub c; Typical Units: ft/s-squared,g; Dimensions: Length / Time-squared;

Corrected altitude.
Measured pressure altitude corrected for instrumentation errors

Coupled.
Describes operation of flight director in which automatic flight control system causes flight controls to follow commands from flight director or errors from guidance

Course cut limit (CCLIM).
A guidance control law parameter, generated by the lateral guidance modes; limits the intercept angle of the flight path with a desired course, typically 45deg Typical Units: deg, rad;

Course.
Towards a point at a specified course; Compare: direct

Creeping line search.
A pattern of equally spaced parallel lines followed for searching the ground from an aircraft; Compare: expanding square search, sector search;

Cross track.
Perpendicular to the course;

Crosstrack deviation (XTKD).
A guidance control law parameter, generated by the lateral guidance modes; distance from the aircraft to a desired course measured along a prependicular to the course Typical Units: ft; Dimensions: Length;

Crosstrack deviation gain (KXTKD).
A guidance control law parameter, generated by the lateral guidance modes; relative weighting of crosstrack deviation in the lateral control law Typical Units: rad/ft; Dimensions: 1/L;

Crosstrack deviation rate (XTKR).
A guidance control law parameter, generated by the lateral guidance modes; rate of change of crosstrack deviation Typical Units: ft/s; Dimensions: Length / Time;

CTALT.
Controlled altitude

CTS.
Controlled speed

Cue.
A indicator to an operator for control placement, tells the operator where to place controls; Synonyms: command

Cursor.
See: moding cursor, target cursor

Cutoff frequency.
The frequency at which the gain of a filter is at an edge of a band, usually taken to be when gain is 0.5, or -3.01dB; the frequency at which the output of a filter is half the power of the input; See Also: band-pass filter, high-pass filter, low-pass filter; Symbols: omega sub c; Typical Units: rad/s,Hz; Dimensions: 1/Time;

Cyclic.
See: longitudinal cyclic, lateral cyclic;

Damped frequency.
The frequency of oscillation of an underdamped second-order filter; See Also: second-order filter; Symbols: omega; Typical Units: rad/s,Hz; Dimensions: 1/Time;

Damping ratio.
Control parameter for a second order filter. Symbols: zeta;

Data source object (DSO).
Software that receives data from a physical device, translates the data into standard units, maintains equipment status, and provides a common interface for each variation of a particular device;

Data Transfer System (DTS).
A device for transferring data with avionics, similar to a diskette drive;

Dead reckoning (DR).
A method of navigation based on basic information (barometric altitude, magnetic heading, airspeed, wind conditions) from best available source; sometimes short for air data dead reckoning;

Delta.
Difference; error.

Depart from hover (dhov).
A guidance mode providing lateral guidance, longitudinal guidance and vertical guidance for a set heading or bank angle, a set speed, and a set climb rate, altitude or pitch;

Derivative.
Rate of change, usually with respect to time; Symbols: x dot, x prime, x sup (1), dx/dt, Dx;

Derived.
Calculated values for which no direct measurement exists; Compare: estimated, filtered, measured, raw, selected, smoothed

DESALT.
Desired altitude

Desired altitude (DESALT).
A guidance control law parameter, generated by the vertical guidance modes; altitude which controlled altitude is attempting to achieve Typical Units: ft; Dimensions: Length;

Desired path.
A trajectory in space determined by guidance to meet the current mission objectives;

Desired speed (DESS).
A guidance control law parameter, generated by the longitudinal guidance modes; speed which controlled speed is attempting to achieve Typical Units: ft/s,kt; Dimensions: Length / Time;

Desired.
What must be achieved in order to match a plan; Synonyms: reference;

DESS.
Desired speed

Deviation.
Difference from desired;

Device.
A piece of equipment, a subsystem; Synonyms: physical device, unit

DFAD.
Digitized Feature Analysis Data

DHOV.
Depart from hover

Difference equation.
A mathematical relationship to model a discrete function, expressed in terms of other values in the sequence; Difference equations are usually derived from differential equations. Compare: continuous-time equation, differential equation, discrete-time equation, Laplace transform, state-space model, Z transform; in avionics, a difference equation us...

Differential equation.
A mathematical relationship to model a continuous function, expressed in terms of derivatives; Initial conditions are usually given or implied. In avionics, differential equations are commonly used by systems engineers to model avionics systems. The systems engineer usually converts differential equations to difference equations for specification a...

Digital Map Generator (DMG).
Digitial equipment that produces map video, and sometimes contains TRN; uses Digital Terrain Elevation Data and Digitized Feature Analysis Data; Displays reconstructed digital map data, aeronautical charts or photographs. The digital map data can be annotated with natural and man-made (point and linear) features as well as threats. A Terrain Refere...

Dimensionless.
No units, such as ratios; Synonyms: unitless;

Direct.
Towards a point along the shortest distance; Compare: course

Direction.
bearing.

Discrete time.
Time divided into quantized intervals; in avionics, time is usually divived into equal intervals to create a periodic process; Compare: continuous time;

Discrete-time equation.
A mathematical relationship to describe a function of time, expressed in terms of discrete time; Compare: continuous-time equation, difference equation, differential equation, Laplace transform, state-space model, Z transform; See Also: first-order filter, unit functions;

Distance Measuring Equipment (DME).
Equipment for measuring distance, usually from an aircraft to a ground station; usually part of a Tactical Air Navigation system

Distance.
Method of measurement dependent on use; Synonyms: range;

DME.
Distance Measuring Equipment

DMG.
Digital Map Generator

DNS.
Doppler Navigation System

Doppler.
A technique for measuring velocity by radiating and determining frequency shift

DPLR.
Doppler navigation system

DR.
Dead reckoning

Drag.
Force of air against aircraft acting in opposite direction of the airspeed vector projected into horizontal plane; Symbols: D; Typical Units: lbf,kip; Dimensions: Mass * Length / Time-squared;

Drift.
Slow, monotonic change in measured data

DSO.
Data source object

DTED.
Digital Terrain Elevation Data

DTS.
Data Transfer System

Dynamic pressure.
Total pressure

Earth coordinates.
Coordinates referenced to the earth; See Also: east-north-up; Compare: body coordinates, stability coordinates

Earth data.
Environmental data related to the earth at some point of interest; usually a function of latitude and longitude

Earth eccentricity.
A measure of the degree to which the earth is oblate; Symbols: epsilon;

Earth model.
The earth model computes data related to the earth. Most data is a function of position. Standard models are: International, Clarke 1866, Clarke 1880, Everest, Modified Everest, Bessel 1841, Australian National, World Geodetic Survey 1972, World Geodetic Survey 1984, Airy, Hough, South American.

Earth radius best sphere.
Gaussian radius of curvature

Earth radius east/west.
Prime radius of curvature

Earth radius north/south.
Meridian radius of curvature

Earth radius.
Radius of the earth, function of position, separate radii for longitudinal radius and for lateral radius; See Also: state data; Symbols: rho; Typical Units: ft; Dimensions: Length;

Earth-referenced flight path angle.
Angle in vertical plane of airspeed vector and groundspeed vector; usual definition for flight path angle; Compare: air-mass flight path angle; Symbols: gamma sub T; Typical Units: rad, deg;

Earthspeed.
Total velocity measured with respect to a plane tangent to the earth's surface at the current position; a vector composed of velocity north, velocity east, and vertical velocity; See Also: state data; Symbols: V sub E; Typical Units: kt,ft/s; Dimensions: Length / Time;

East-north-up (ENU).
A standard earth coordinate frame and sign convention, where east, north, and up are positive; vertical, or V, is sometimes used in place of up; Synonyms: east-north-vertical; Compare: XYZ;

East-north-vertical (ENV).
East-north-up.

ECI.
Earth Centered Inertial

Elevation.
An angle in the vertical plane through a longitudinal axis; height above mean sea level, usually of terrain;

Elevator.
A control surface on fixed-wing aircraft, usually mounted on the aft edge of stabilizers, that controls pitch, and is controlled by the yoke; Symbols: delta sub E; Typical Units: rad, deg;

ENU.
East-north-up

ENV.
East-north-vertical

Environmental data.
Atmospheric data and earth data

Equipment status.
Operational status of a piece of equipment consisting of a status indicator and status words; Synonyms: health;

Error.
Difference between desired and measured data; Synonyms: delta;

Estimated.
Data that is the result of filtering two or more signals; Compare: derived, filtered, measured, raw, selected, smoothed

Euler angles.
Pitch, roll, and yaw

Euler parameters.
Four parameters for specifiying quaternions; Symbols: e sub < 1 , 2 , 3 , 4 >,a,b,c,s;

Everest.
A standard model for computing earth data

Expanding square search.
A pattern of progressively larger squares (a ``square spiral'') followed for searching the ground from an aircraft; Compare: creeping line search, sector search;

Extrapolate.
Function to determine values from two or values in a table, when the given value lies outside of the range of the table; usually linear but can be higher order;

FCS.
Flight control system

Filter.
A device to alter a signal; software to alter a data steam; See Also: averaging filter, band-pass filter, complementary filter, first-order filter, high-pass filter, hysteresis, Kalman filter, limiter, low-pass filter, rate limiter, second-order filter, smoothing filter, wash-out filter;

Filtered.
Data that is the result of filtering a signal; filtering is usually more sophisticated than smoothing Compare: derived, estimated, measured, raw, selected, smoothed;

First-order filter.
A filter in which the output follows the input, only more slowly; It is usually implemented in software as a difference equation of period T. The first-order filter is commonly used in avionics to smooth data, and to wash out transients at mode change. It is also used as a low-pass filter. When implementing a second-order filter on normalized varia...

Fix.
A determination of one's position based on external data, such as a known terrain point

Fixed wing.
An airplane, as opposed to a rotory wing / helicopter;

Flaps.
A control surface on fixed-wing aircraft, usually mounted to the fore edge of the wings, that extends the wing to provide added lift at low speeds; Compare: slats; Symbols: delta sub F; Typical Units: rad, deg,percent;

Flight control system (FCS).
A primary flight control system or an automatic flight control system;

Flight controls.
Controls in a cockpit for flying an aircraft; primary flight controls are wheel, yoke, cyclic, pedals, throttle, and collective; secondary flight controls are flight controls other than primary, such as flaps, slats, stabilizer, and landing gear;

Flight director.
System, usually software, that generates stick position cues from state errors - typically three cues:. pitch, roll, and throttle for fixed-wing and longitudinal cyclic, lateral cyclic, and collective for rotory wing;

Flight path angle (FPA).
Angle in vertical plane of earthspeed vector and groundspeed vector (usual definition), earth-referenced flight path angle; angle in vertical plane of airspeed vector and groundspeed vector (occasional definition), air-mass flight path angle; Symbols: gamma; Typical Units: rad, deg;

Flight plan.
A predetermined route, possibly including guidance modes, communications, and mission objectives, used by guidance and mission management for moding and planning; Series of navigation reference points, waypoints, and mode commands for navigation, radio navigation, guidance, and flight director