Glossary of Aviation Terminology

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Mach number: Ratio of airspeed to the local speed of sound (Mach 1 is the speed of sound under current atmospheric conditions); Symbols: M;

Magnetic heading: Heading of the aircraft relative to magnetic north; A Magnetic Heading Sensor provides this heading data. Symbols: psi sub M; Typical Units: rad, deg;

Magnetic variation (MVAR, MAGVAR): Difference between true north and magnetic north, varying with position; magnetic variation drifts with time; Symbols: nu; Typical Units: rad, deg;

MAGVAR: Magnetic variation

Maintenance: Indicates device is in a maintenance mode; Values: non-maintanance, calibration, alignment, boresight

Map: Equipment that produces a map image; See Also: Digital Map Generator

Marker beacon (MB): Part of Instrument Landing System that signals crew members of distance to runway, consisting of three markers:. inner, middle, and outer;

Massaged: Filtered, estimated, or derived, or some combination of the three

Master caution: A signal which indicates that one or more caution lights has been activated (from MIL-STD-1472D);

Master warning: A signal which indicates that one or more warning lights has been activated (from MIL-STD-1472D);

MB: Marker Beacon

MC: Mission computer

Mean sea level (MSL): Standard aviation term See Also: above sea level;

Measured: Raw data converted to standard units; Compare: derived, estimated, filtered, raw, selected, smoothed

Meridian radius of curvature: Radius of the earth in the east/west direction at a given position; Synonyms: earth radius north/south; Symbols: rho sub M; Typical Units: ft; Dimensions: Length;

Middle marker: Marker beacon located where the center of the glideslope is 200ft above the runway

Mission computer (MC): Mission processor;

Mission objectives: Goals to be accomplished during a specific mission, including flight plan, NRPs, legs, and a plan on how to accomplish these objectives; plan includes, usually on a leg-by-leg basis, navigation modes, radio navigation modes, guidance modes, flight director modes, data source control information such as frequencies; See Also: capture criterion

Mission processor (MP): A general purpose computer to host avionics software. Synonyms: mission computer;

MLS: Microwave Landing System

Mode: A selection of one of several alternatives, such as guidance mode (VOR, TACAN, or Waypoint), or navigation mode (INS, Doppler, or dead reckoning)

Modified Everest: A standard model for computing earth data

Moding cursor: A symbol on a display, moved by an operator much like arrow keys for menu selection, to select one of several options

MP: Mission processor

MSL: Mean sea level

Multi-mode radar (MMR): A Multi-Mode Radar is used for Terrain Following (TF) and Terrain Avoidance (TA), Ground Mapping (GM) and Air-to Ground Ranging (AGR). The TF mode supplies commands which are processed and displayed as climb/dive commands on the Flight Director display and E-squared video used by the operators in anticipating near term TF commands. When in TA or GM modes, the operator is provided with a Plan Position Indicator (PPI) display. The AGR mode allows the operators to determine the range to a designated target, which can be used for position updates.

MVAR: Magnetic variation

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