NOTE - Sensors are not all associated with specific runways, and descriptions of the remote sites are based on an eight point compass system. Airports equipped with this system will be shown in the Enroute Supplement under Remarks.
MACH NUMBER (P/CG) - The ratio of True Airspeed to the speed of sound, e.g., MACH .82, MACH 1.6. (See Airspeed)
MACH NUMBER (JCS, NATO) - The ratio of the velocity of a body to that of sound in the surrounding medium.
MACH TECHNIQUE (ICAO) - Describes a control technique used by air traffic control whereby turbojet aircraft operating successively along suitable routes are cleared to maintain appropriate MACH numbers for a relevant portion of the enroute phase of flight. The principle objective is to achieve improved utilization of the airspace and to ensure that separation between successive aircraft does not decrease below the established minima.
MAGNETIC VARIATION - The angular difference between true North and magnetic North.
MAINTAIN -
(1)
Concerning altitude/Flight Level, the term means to remain at the altitude/Flight Level specified. The phrase "climb and” or “descend and” normally precedes “maintain” and the altitude assignment, e.g., “descend and maintain 5000".
(2)
Concerning other Air Traffic Control instructions, the term is used in its literal sense, e.g., maintain Visual Flight Rules.
MAKE SHORT APPROACH - Used by Air Traffic Control to inform a pilot to alter his traffic pattern so as to make a short final approach. (See Traffic Pattern)
MANDATORY ALTITUDE - An altitude depicted on an Instrument Approach Procedure Chart requiring the aircraft to maintain altitude at the depicted value.
MANDATORY TRAFFIC ADVISORY FREQUENCY/MTAF (NGA) - A mandatory frequency designed for the purpose of carrying out airport advisory practices while operating to or from an aerodrome when the control tower is closed, uncontrolled airport, or within a designated area. The MTAF may be a UNICOM, MULTICOM, Flight Service Station or tower frequency. The MTAF is used when within 15 nautical miles and below 5000 feet above ground level unless otherwise noted.
MARKER BEACON - An electronic navigation facility transmitting a 75 Megahertz vertical fan or bone shaped radiation pattern. Marker beacons are identified by their modulation frequency and keying code and when received by compatible airborne equipment, indicate to the pilot, both aurally and visually, that he is passing over the facility. (See Outer Marker, Middle Marker, Inner Marker)
MAXIMUM AUTHORIZED ALTITUDE/MAA - A published altitude representing the maximum usable altitude or Flight Level for an airspace structure or route segment. It is the highest altitude on a federal airway, jet route, area navigation low or high route, or other direct route for which a Minimum Enroute Altitude is designated in Federal Air Regulations Part 95, at which adequate reception of navigation aid signals is assured.
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