Aviation Dictionary

On this page you will find a searchable and comprehensive alphabetical list of aviation terms. You can help us make it the most comprehensive list in the world. If we have missed anything, click on the ‘send us your word’ button to send us your word, acronym or definition and we will consider adding it to our dictionary.

Aviation Dictionary: M

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MAC Mean aerodynamic chord
MAPt Missed approach point
Magnetic North The direction that a compass needle will point to. This aligns with the earth's magnetic fields and is not in the same position as True North. Magnetic North drifts at a rate of between 9 - 30 miles per year and is currently in the Arctic Ocean between Canada and Russia
Manoeuvring Area The areas of the aerodrome that is used for the surface movement of aircraft associated with take-off and landing, but does not include areas set aside for loading, unloading or maintenance of aircraft.
Mayday A distress call that is sent out by a pilot of either a ship or aircraft and is used to signal a life threatening emergency. Mayday calls have priority over any other radio call
Maximum demonstrated Crosswind Component This is a figure that can be found in the flight manual, detailing the maximum amount of crosswind that the aircraft has been factory tested in and has shown that directional control can still be maintained. It is affected by the size of the rudder, its distance from the CoG and the availability of asymmetric braking 
Maximum Take-Off Weight (MTOW) The maximum weight an aircraft can be at take-off
Maximum Landing Weight (MLW) The maximum weight an aircraft can be at landing. In most light aircraft, this weight will be the same as the MTOW, whereas larger aircraft will have a much lower landing weight then take-off weight.
Magnetic North The direction that a compass needle will point to. This aligns with the earth's magnetic fields and is not in the same position as True North. Magnetic North drifts at a rate of between 9 - 30 miles per year and is currently in the Arctic Ocean between Canada and Russia
MBZ Mandatory Broadcast Zone. An MBZ is established to provide increased protection to aircraft in areas of uncontrolled airspace which may have a high volume of traffic, Position reports are required on the designated frequency at regular time intervals and when at specific reporting points. Lights should also be used when operating in or around high traffic areas
MCT Morning Civil Twilight. This begins when the sun is 6 degrees below the horizon and ends at sunset.
MDA Minimum descent altitude. The minimum altitude for a non-precision approach below which a descent must not be made unless visual reference with the required indicators are acquired.
MDH Minimum descent height. The minimum height above aerodrome level for a non-precision approach below which a descent must not be made unless visual reference with the required indicators are acquired.
Mean Sea Level (MSL) A measurement of your true altitude or elevation above the standard sea level datum.
Mechanical Turbulence This occurs closer to ground level by air moving over buildings, trees or other obstacles, which disrupt a smooth flow of air
Medical A medical certificate issued by a certified aviation doctor
Medium Turn A turn done at a constant bank angle of 30 degrees
MEIR Multi Engine Instrument Rating
MEL Minimum equipment list
Mesosphere The third layer in our atmosphere. The coldest layer and temperature decreases with an increase in height.
Met Meteorology
METAR Routine aerodrome meteorological report, valid for 1 hour
Metar Auto Automated observations provided by an AWS. Produced every 30 mins on the hr and half hr. Will not include cloud type
MF Medium frequency
MI Shallow
Military Operating Areas An airspace area which is generally designated for extensive military operations, including live firing. An entry approval is required and some non-permanent areas may be established and can be found in NOTAMS
Minimum Fuel A term used to describe an aircraft's fuel level where the fuel supply has reached a state where the aircraft is committed to land at a specific aerodrome with no additional delay
Minimum Safe Altitude The lowest altitude round up to the nearest 100ft  which provides the required terrain clearance.
Missed Approach Generally an IFR term used for aborting a landing attempt, possibly because the approach minimas,or visual contact with the runway, lights, or other requirements to land, were not met. Performing a missed approach will lead to further instructions from ATC to reposition for another approach, or continue on towards your alternate.
Mixture This is the ratio of fuel/air which is controlled by the mixture lever. A pilot is able to control the amount of fuel that is mixed with the air and this is useful when climbing to high altitudes where there is less air, which if the pilot does nothing, the mixture will be rich, or have more fuel than required and could lead to rough engine running, so the pilot would lean the mixture. When descending from a high altitude, the pilot would richen the mixture, or increase the amount of fuel to air ratio as there is more air closer to MSL than at altitude. If the pilot forgot to enrich the mixture, the engine could stop because of fuel starvation.
MLS Microwave landing system
MLW Maximum landing weight
MOS Manual of standards
Mountain Waves A disturbance in the airflow on the Lee side of a mountain. Lenticular clouds can show the wave pattern
MP Manifold pressure
MPL Multi-crew pilot licence
MSA Minimum Sector Altitude. The lowest altitude that may be used that will provide a minimum clearance of 1000 ft or 2000 ft above designated mountainous zones, above the highest obstacle located within 25nm of the designated nav aid or aerodrome designation point.
MSL Mean sea level
MTOW Maximum take-off weight
Multi Engine Aircraft An aircraft powered by two or more engines
MZW Mid-zone weight

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