MACH—Speed relative to the speed of sound. Mach 1 is the speed of sound.

MACH BUFFET— Airflow separation behind a shock-wave pressure barrier caused by airflow over flight surfaces exceeding the speed of sound.

MACH COMPENSATING DEVICE—A device to alert the pilot of inadvertent excursions beyond its certified maximum operating speed.

MACH CRITICAL—The MACH speed at which some portion of the airflow over the wing first equals MACH 1.0. This is also the speed at which a shock wave first appears on the airplane.

MACH TUCK—A condition that can occur when operating a swept-wing airplane in the transonic speed range. A shock wave could form in the root portion of the wing and cause the air behind it to separate. This shock-induced separation causes the center of pressure to move aft. This, combined with the increasing amount of nose down force at higher speeds to maintain left flight, causes the nose to “tuck.” If not corrected, the airplane could enter a steep, sometimes unrecoverable dive.

MAGNETIC COMPASS—A device for determining direction measured from magnetic north.

MAIN GEAR—The wheels of an aircraft’s landing gear that supports the major part of the aircraft’s weight.

MANEUVERABILITY—Ability of an aircraft to change directions along a flightpath and withstand the stresses imposed upon it.

MANEUVERING SPEED (VA) — The maximum speed where full, abrupt control movement can be used without overstressing the airframe.

MANIFOLD PRESSURE (MP)— The absolute pressure of the fuel/air mixture within the intake manifold, usually indicated in inches of mercury.

MAXIMUM ALLOWABLE TAKEOFF POWER—The maximum power an engine is allowed to develop for a limited period of time; usually about one minute.

MAXIMUM LANDING WEIGHT—The greatest weight that an airplane normally is allowed to have at landing.

MAXIMUM RAMP WEIGHT— The total weight of a loaded aircraft, including all fuel. It is greater than the takeoff weight due to the fuel that will be burned during the taxi and runup operations. Ramp weight may also be referred to as taxi weight.

MAXIMUM TAKEOFF WEIGHT—The maximum allowable weight for takeoff.

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.

MAXIMUM ZERO FUEL WEIGHT (GAMA)—The maximum weight, exclusive of usable fuel.

MINIMUM CONTROLLABLE AIRSPEED—An airspeed at which any further increase in angle of attack, increase in load factor, or reduction in power, would result in an immediate stall.

MINIMUM DRAG SPEED (L/DMAX)—The point on the total drag curve where the lift-to-drag ratio is the greatest. At this speed, total drag is minimized.

MIXTURE—The ratio of fuel to air entering the engine’s cylinders.

MMO—Maximum operating speed expressed in terms of a decimal of mach speed.

MOMENT ARM—The distance from a datum to the applied force.

MOMENT INDEX (OR INDEX)— A moment divided by a constant such as 100, 1,000, or 10,000. The purpose of using a moment index is to simplify weight and balance computations of airplanes where heavy items and long arms result in large, unmanageable numbers.

MOMENT—The product of the weight of an item multiplied by its arm. Moments are expressed in pound-inches (lb-in). Total moment is the weight of the airplane multiplied by the distance between the datum and the CG.

MOVABLE SLAT—A movable auxiliary airfoil on the leading edge of a wing. It is closed in normal flight but extends at high angles of attack. This allows air to continue flowing over the top of the wing and delays airflow separation.

MUSHING—A flight condition caused by slow speed where the control surfaces are marginally effective.