Modulated continuous wave code differs from continuous wave (CW) code in that a beat-frequency oscillator is not needed in the receiver for MCW to be heard.
MDA (minimum descent altitude). 14 CFR Part 1: “The lowest altitude, expressed in feet above mean sea level, to which descent is authorized on final approach or during circle-to-land maneuvering in execution of a standard instrument approach procedure, where no electronic glide slope is provided.”
MEA (minimum enroute IFR altitude). The lowest published altitude between radio fixes which assures acceptable navigational signal coverage and meets obstacle clearance requirements between those fixes.
The MEA prescribed for a federal airway or segment thereof, area navigation low or high route, or other direct route applies to the entire width of the airway, segment, or route between the radio fixes defining that airway, segment, or route.
mean. A term used for the middle-point, or median. Mean sea level is the midpoint between the highest and lowest level of the sea. Mean values are used when measuring from a reference that moves, or changes, between specific limits.
mean aerodynamic chord. See MAC.
mean camber. A line that is drawn midway between the upper and lower camber of an airfoil section. The mean camber determines the aerodynamic characteristics of the airfoil.
mean sea level. See MSL.
mean solar day. The time it takes the earth to rotate about its axis, with respect to the mean location of the sun. The length of a mean solar day is 24 hours, 3 minutes, and 56.555 seconds.
measured ceiling (meteorology). A ceiling classification applied when the ceiling value has been determined by instruments or the known heights of unobscured portions of objects other than natural landmarks.
mechanic. A person skilled in repairing mechanical devices. The Federal Aviation Administration issues a license for aircraft mechanics, and there were two ratings used with this license: airframe and powerplant. The term mechanic is scheduled to be replaced by technician, and the Mechanic Certificate replaced by the Aviation Maintenance Technician Certificate by the proposed 14 CFR Part 66, Aviation Maintenance Personnel.
mechanical advantage. The increase in force or speed produced by a mechanical device, such as the lever, pulley, gears, or hydraulic cylinder. These devices increase speed or force, but they cannot produce work. The force needed to lift a weight may be reduced, or the speed at which an object moves may be changed. But if mechanical losses are discounted, the amount of work (force times distance) taken from the device is the same as the amount of work put into it.
mechanical blockage thrust reverser (gas turbine engine component). A type of thrust reverser that uses a pair of clamshell doors set into the tail cone of the engine to deflect the exhaust gases forward when the pilot wants to slow the aircraft.
mechanical efficiency (reciprocating engines). The ratio of the amount of brake horsepower delivered to the output shaft of a reciprocating engine to the amount of indicated horsepower produced in the cylinders of the engine.
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