Aeronautical Terms beginning with M
Mach number
The ratio of true airspeed to the speed of sound.
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 en route 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 bearing (MB)
The direction to or from a radio transmitting station measured relative to magnetic north.
Magnetic compass
A device for determining direction measured from magnetic north.
Magnetic Course
A predetermined desired course direction to be followed (measured in degrees from local magnetic north).
Magnetic dip
A vertical attraction between a compass needle and the magnetic poles. The closer the aircraft is to a pole, the more severe the effect.
Magnetic heading (MH)
The direction an aircraft is pointed with respect to magnetic north.
Maintain
A. 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 5,000.”
B. Concerning other ATC instructions, the term is used in its literal sense; e.g., maintain VFR.
Make Short Approach
Used by ATC to inform a pilot to alter his/her traffic pattern so as to make a short final approach.
MALS
Medium Intensity Approach Light System.
MALSR
Medium Intensity Approach Light System with Runway Alignment Indicator Lights.
Man Portable Air Defense Systems (MANPADS)
MANPADS are lightweight, shoulder-launched, missile systems used to bring down aircraft and create mass casualties. The potential for MANPADS use against airborne aircraft is real and requires familiarity with the subject. Terrorists choose MANPADS because the weapons are low cost, highly mobile, require minimal set-up time, and are easy to use and maintain. Although the weapons have limited range, and their accuracy is affected by poor visibility and adverse weather, they can be fired from anywhere on land or from boats where there is unrestricted visibility to the target.
Maneuvering speed (Va)
The maximum speed at which full, abrupt control movement can be used without overstressing the airframe.
MANPADS
Man Portable Air Defense Systems
Mass
The amount of matter in a body.
Maximum weight
The maximum authorized weight of the aircraft and all of its equipment as specified in the Type Certificate Data Sheets (TCDS) for the aircraft.
Mayday
The international radiotelephony distress signal. When repeated three times, it indicates imminent and grave danger and that immediate assistance is requested.
MB
Magnetic Bearing.
Mean sea level
The average height of the surface of the sea at a particular location for all stages of the tide over a 19-year period.
Medical certificate
Acceptable evidence of physical fitness on a form prescribed by the Administrator.
MEL
Minimum Equipment List.
Meridians
Lines of longitude.
METAR
Aviation Routine Weather Report.
Metering Fix
A fix along an established route from over which aircraft will be metered prior to entering terminal airspace. Normally, this fix should be established at a distance from the airport which will facilitate a profile descent 10,000 feet above airport elevation (AAE) or above.
MFD
Multi-Function Display.
MH
Magnetic Heading.
MHz
Megahertz
Middle Compass Locator (LMM)
A compass locator installed at the site of the middle marker of an instrument landing system.
Middle Marker
A marker beacon that defines a point along the glideslope of an ILS normally located at or near the point of decision height (ILS Category I). It is keyed to transmit alternate dots and dashes, with the alternate dots and dashes keyed at the rate of 95 dot/dash combinations per minute on a 1300 Hz tone, which is received aurally and visually by compatible airborne equipment.
Mileage breakdown
A fix indicating a course change that appears on the chart as an “x” at a break between two segments of a federal airway.
Military Landing Zone
A landing strip used exclusively by the military for training. A military landing zone does not carry a runway designation.
Military operations area
A military operations area (MOA) is airspace established outside Class A airspace to separate or segregate certain nonhazardous military activities from IFR Traffic and to identify for VFR traffic where theses activities are conducted.
Military Operations Area (MOA)
A MOA is airspace established outside of Class A airspace area to separate or segregate certain nonhazardous military activities from IFR traffic and to identify for VFR traffic where these activities are conducted.
Military training route (MTR)
Airspace of defined vertical and lateral dimensions established for the conduct of military training at airspeeds in excess of 250 knots indicated airspeed (KIAS).
Minima
Minimums.
Minimum Fuel
Indicates that an aircraft’s fuel supply has reached a state where, upon reaching the destination, it can accept little or no delay. This is not an emergency situation but merely indicates an emergency situation is possible should any undue delay occur.
Minimum Holding Altitude
The lowest altitude prescribed for a holding pattern which assures navigational signal coverage, communications, and meets obstacle clearance requirements.
Minimum Safe Altitude Warning
A function of the ARTS III computer that aids the controller by alerting him/her when a tracked Mode C equipped aircraft is below or is predicted by the computer to go below a predetermined minimum safe altitude.
Minimum Vectoring Altitude (MVA)
The lowest MSL altitude at which an IFR aircraft will be vectored by a radar controller, except as otherwise authorized for radar approaches, departures, and missed approaches. The altitude meets IFR obstacle clearance criteria. It may be lower than the published MEA along an airway or J-route segment. It may be utilized for radar vectoring only upon the controller’s determination that an adequate radar return is being received from the aircraft being controlled. Charts depicting minimum vectoring altitudes are normally available only to the controllers and not to pilots.
Minimums
Weather condition requirements established for a particular operation or type of operation; e.g., IFR takeoff or landing, alternate airport for IFR flight plans, VFR flight, etc.
MIRL
Medium Intensity Runway Lights
Missed Approach
A. A maneuver conducted by a pilot when an instrument approach cannot be completed to a landing. The route of flight and altitude are shown on instrument approach procedure charts. A pilot executing a missed approach prior to the Missed Approach Point (MAP) must continue along the final approach to the MAP.
B. A term used by the pilot to inform ATC that he/she is executing the missed approach.
C. At locations where ATC radar service is provided, the pilot should conform to radar vectors when provided by ATC in lieu of the published missed approach procedure.
Missed Approach
The segment between the missed approach point or the point of arrival at decision height and the missed approach fix at the prescribed altitude.
MOA
Military Operations Area
Mode
The letter or number assigned to a specific pulse spacing of radio signals transmitted or received by ground interrogator or airborne transponder components of the Air Traffic Control Radar Beacon System (ATCRBS). Mode A (military Mode 3) and Mode C (altitude reporting) are used in air traffic control.
Mode C
Altitude reporting transponder mode.
Moderate Icing
The rate of accumulation is such that even short encounters become potentially hazardous and use of deicing/anti-icing equipment or flight diversion is necessary.
Modified T
An RNAV approach design for single or multiple runways where terrain or operational constraints do not allow for the standard T. The “T” may be modified by increasing or decreasing the angle from the corner IAF(s) to the IF or by eliminating one or both corner IAFs.
Monitor
(When used with communication transfer) listen on a specific frequency and stand by for instructions. Under normal circumstances do not establish communications.
Movement Area
The runways, taxiways, and other areas of an airport/heliport which are utilized for taxiing/hover taxiing, air taxiing, takeoff, and landing of aircraft, exclusive of loading ramps and parking areas. At those airports/heliports with a tower, specific approval for entry onto the movement area must be obtained from ATC.
Moving Target Indicator
A digital moving target indicator (MTI) radar system for rejection of low velocity "clutter" by utilizing techniques to identify those radar echo returns from targets having radial velocities lower than fixed predetermined values.
MRB
Magnetic Reference Bearing
MSL
Mean Sea Level.
MSL Altitude
Altitude expressed in feet measured from mean sea level.
MTI
Moving Target Indicator
MTR
Military Training Route
Multicom
A mobile service not open to public correspondence used to provide communications essential to conduct the activities being performed by or directed from private aircraft.
Multiple Runways
The utilization of a dedicated arrival runway(s) for departures and a dedicated departure runway(s) for arrivals when feasible to reduce delays and enhance capacity.
Mushing
A flight condition caused by slow speed where the control surfaces are marginally effective.
MWO
Meteorological Watch Office
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