Aeronautical Terms beginning with M
M
Mach Number.
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 meter
The instrument that displays the ratio of the speed of sound to the true airspeed an aircraft is flying.
Mach number
The ratio of the true airspeed of the aircraft to the speed of sound in the same atmospheric conditions, named in honor of Ernst Mach, late 19th century physicist.
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 level flight, causes the nose to “tuck.” If not corrected, the airplane could enter a steep, sometimes unrecoverable dive.
Maximum engine overtorque
As it applies to turbopropeller and turboshaft engines incorporating free power turbines for all ratings except one engine inoperative (OEI) ratings of two minutes or less, the maximum torque of the free power turbine rotor assembly, the inadvertent occurrence of which, for periods of up to 20 seconds, will not require rejection of the engine from service, or any maintenance action other than to correct the cause. Maximum speed for stability characteristics, V FC/MFC means a speed that may not be less than a speed midway between maximum operating limit speed (VMO/MMO) and demonstrated flight diving speed (VDF/MDF), except that, for altitudes where the Mach number is the limiting factor, MFC need not exceed the Mach number at which effective speed warning occurs.
MEL
Minimum Equipment List.
Minimum equipment list (MEL)
A list developed for larger aircraft that outlines equipment that can be inoperative for various types of flight including IFR and icing conditions. This list is based on the master minimum equipment list (MMEL) developed by the FAA and must be approved by the FAA for use. It is specific to an individual aircraft make and model.
Minimum Navigation Performance Specification
A set of standards which require aircraft to have a minimum navigation performance capability in order to operate in MNPS designated airspace. In addition, aircraft must be certified by their State of Registry for MNPS operation.
Minimum Navigation Performance Specification Airspace
Designated airspace in which MNPS procedures are applied between MNPS certified and equipped aircraft. Under certain conditions, non-MNPS aircraft can operate in MNPSA. However, standard oceanic separation minima is provided between the non-MNPS aircraft and other traffic. Currently, the only designated MNPSA is described as follows: a. Between FL 285 and FL 420; b. Between latitudes 27°N and the North Pole; c. In the east, the eastern boundaries of the CTAs Santa Maria Oceanic, Shanwick Oceanic, and Reykjavik; d. In the west, the western boundaries of CTAs Reykjavik and Gander Oceanic and New York Oceanic excluding the area west of 60°W and south of 38°30’N.
Minutes-In-Trail
A specified interval between aircraft expressed in time. This method would more likely be utilized regardless of altitude.
MLS Categories
A. MLS Category I. An MLS approach procedure which provides for an approach to a height above touchdown of not less than 200 feet and a runway visual range of not less than 1,800 feet.
B. MLS Category II. Undefined until data gathering/analysis completion.
C. MLS Category III. Undefined until data gathering/analysis completion.
MMO
Maximum operating speed expressed in terms of a decimal of mach speed.
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