Glossary - Letter M

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m |abbreviation| meter, minute


Mach |noun| the ratio of the speed of an object to the speed of sound in the same atmospheric conditions / Mach 2 equals twice the speed of sound. /


machine |noun| a device with fixed and moving parts that takes mechanical energy and uses it to do useful work / A drill is a machine for making holes in things. An electrical circuit is designed to carry energy to a particular device or machine which can then perform useful work. /


Mach-meter |noun| an instrument for measuring the Mach number of an aircraft


Mach number |noun| a number that expresses the ratio of the speed of an object to the speed of sound


magnesium |noun| a light, silvery-white metallic element that burns with a brilliant white flame. Symbol: Mg (NOTE: The atomic number of magnesium is 12.)


magnesium flare |noun| a device for distress signalling at night


magnet |noun| an object that produces a magnetic field, and attracts iron and steel / Magnetism in a magnet appears to be concentrated at two points called the poles. /


magnetic |adjective| referring to or having the power of a magnet or something with a magnetic field / A freely suspended magnet – not influenced by outside forces – will align itself with the Earth’s magnetic lines of force which run from the north magnetic pole to the south magnetic pole. /


magnetic bearing |noun| the angle measured in a clockwise direction of a distant point, relative to magnetic north


magnetic declination |noun| same as magnetic variation / To convert magnetic bearing into true bearing it is necessary to apply magnetic variation at the point at which the bearing was taken. /


magnetic field |noun| area of magnetic influence


magnetic north |noun| the direction of the Earth’s magnetic pole, to which the north-seeking pole of a magnetic needle points if unaffected by nearby influences


magnetic pole |noun| one of the two poles which are the centers of the Earth’s magnetic field

magnetic track |noun| a track / course using the Earth’s magnetic field. Given the fluctuations in magnetic field in the polar regions, magnetic navigation cannot be used here.

magnetic variation |noun| differences in the Earth’s magnetic field in time and place / To convert magnetic bearing into true bearing it is necessary to apply magnetic variation at the point at which the bearing was taken. / Also called: magnetic declination


magnetize |verb| to convert an object or material into a magnet / Ferromagnetic materials are easily magnetized. /


magnetism |noun| a force exerted by a magnetic field / An electric current produces magnetism, and movement of a magnet can produce electricity. /


magneto |noun| a device that produces electrical current for distribution to the spark plugs of piston aero-engines (NOTE: The crankshaft turns the magnetos, which provide the electrical energy to create a spark from the spark plugs. This ensures that the spark plugs work even if the aircraft’s battery and electrical system fail. Most aircraft have two magnetos per engine in case one fails.)


magnify |verb|  1. to increase the size of, especially by using a lens, microscope, etc. / It was only after the image was magnified that it was possible to see the flaw. /  2. to increase the effect of something / The stress level is magnified at times of high work load, for example, preparation for landing. / (NOTE: magnifying – magnified)


magnitude |noun| greatness in size or extent / The magnitude of the pressure gradient force is inversely proportional to the distance apart of the isobars. When the surface wind speed reaches a particular magnitude the term gale is used. /


maiden flight |noun| the first flight of a new aircraft / The maiden flight of the A340 was in October 1991. /


main |adjective| most important; principal - main disadvantages > principal negative points

main equipment center |noun| the under-floor avionics compartment where computers and other electronic equipment are located (Boeing); on Airbus aircraft this is referred to as the avionics bay

main gear |noun| two main landing wheel assemblies

main landing gear |noun| the main landing gear which is located under the inner wing and, in very large aircraft, under the center fuselage. It consists of wheels mounted on axles connected by a boggie which is attached to the gear leg through a shock absorber. The gear is maintained rigid, retracted and extended by a series of struts, braces and actuators. Abbreviation: MLG

main-plane |noun| an aircraft wing, compared with the tailplane / The region between the main-plane front and rear spars is commonly sealed off and used as tanks. /


maintain |verb|  1. to keep up, to carry on or continue - to maintain the present heading > to continue on the same heading - to maintain a constant selected engine speed > not to change the engine speed  2. to keep in good mechanical or working order / Aero-engines must be maintained regularly to maximize engine life. / - to maintain own separation > the crew uses its vision of other aircraft to keep the necessary distance from other traffic


maintenance |noun| a regular periodic inspection, overhaul, repair and replacement of parts of an aircraft and/or engine / The gas turbine is a very simple engine with few moving parts when compared with a piston engine, giving it a high reliability factor with less maintenance. / - maintenance manual > the manufacturer’s instruction book of maintenance procedures ‘…poor maintenance training is expensive for the airline who notices the problem in late departures, longer than necessary maintenance periods and worst of all, crashes’ [Civil Aviation Training]


maintenance crew |noun| ground staff whose responsibility it is to keep the aircraft serviceable / The maintenance crew worked through the night to complete the work. /


major |adjective| important / There are two major cloud groups, stratus and cumulus. / - major airport > a large, important or international airport - major problem > a serious problem. Opposite: minor


majority |noun| the greater number or larger part – anything more than 50% / The majority of passengers prefer to sit in a non-smoking area of the cabin. /


malfunction |noun| a failure to work or to function correctly / The oil pressure and temperature of the CSDU can be monitored by the pilot and if a malfunction occurs, the pilot can then choose to disconnect the CSDU from the engine. / - |verb| to function incorrectly or fail to function / Oscillating outputs from the alternators could cause sensitive equipment to malfunction. /

manage |verb|  1. to succeed in doing something / We managed to isolate the failure. /  2. to control a situation / ATC manages traffic flow. /

mandatory |adjective| compulsory, required or ordered by an official organization or authority / Fire detection systems in toilets are mandatory. /


maneuver |noun| US same as manoeuvre


maneuverability |noun| US same as manoeuvrability


maneuvering area |noun| US same as manoeuvring area


manifold |noun| a system of pipes for a fluid from single input to multiple output or multiple input to single output / inlet and exhaust manifolds of a piston engine /


manifold pressure |noun| absolute pressure in the induction system of a piston engine measured in inches of mercury


manner |noun| a way of doing something / Wind is said to be veering when it changes direction in a clockwise manner. Pre-flight checks should be done in the correct manner. /


manoeuvrability |noun| the ability and speed with which an aircraft can turn away from its previous path / Light training aircraft do not have great manoeuvrability but they are stable and therefore easier to fly. / (NOTE: The US spelling is maneuverability.)


manoeuvre |noun| any deliberate or intended departure from the existing flight or ground path (NOTE: It is also written maneuver in US English.) - flight manoeuvre > turns, loops, climbs and descents - ground manoeuvre > taxiing and turning onto runways and taxiways, etc.


manoeuvring area |noun| the part of the aerodrome used for the take-off, landing and taxiing of aircraft


manual |adjective| referring to the hands, or done or worked by hand / The electronic flight instrument system has two self-test facilities – automatic and manual. / - |noun| a reference book giving instructions on how to operate equipment, machinery, etc. / maintenance manual, aircraft operating manual /


manual control |noun| hand-flying an aircraft equipped with an autopilot or automatic flight control system


manually |adverb| by hand / The system is switched on manually. /


manufacture |verb| to make a product for sale using industrial machines / The centrifugal compressor is usually more robust than the axial flow type and also easier to develop and manufacture. /


map |noun| a representation of the Earth’s surface on a flat surface such as a sheet of paper - |verb| to make measurements and calculations of part of the Earth’s surface in order to produce a map


MAP |abbreviation| missed approach point


margin |noun|  1. a blank space bordering the written or printed area on a page / Write notes in the margin of the book. /  2. an amount allowed in addition to what is needed / In some configurations, it is possible for the buffet speed to be less than the required 7% margin ahead of the stall. /


maritime |adjective| referring to the sea / The Rocky Mountains of North America act as a barrier to the cool maritime winds from the Pacific Ocean. /


mark |noun|  1. a visible trace on a surface, e.g. a dot or a line / There are marks on tires and wheel rims which are aligned and indicate the extent of tire creep. /  2. the number of points or a percentage given for academic work - |verb|  1. to make a visible line, dot, etc., on a surface / Mark the departure point on the chart. /  2. to show or indicate / The weather front marks the boundary between the two air masses. /  3. to correct or check academic work done by a student / The instructor marked the exam papers. /


marked |adjective| very noticeable, clear and definite - a marked increase > a noticeable, therefore possibly large, increase - a marked change in the weather > a significant change in the weather


marker |noun|  1. something which acts as an indicator of something such as distance or position  2. a radio beacon that is part of the ILS (NOTE: The outer marker (OM) is indicated on the instrument panel, by a blue light. The middle marker (MM) is indicated by an amber light and the inner marker (IM) by a white light.)


marker dye |noun| a brightly colored substance used by people adrift at sea to draw the attention of flight crews to their position

marking |noun| an indication painted horizontally onto the runway or taxiway / Holding points are identified by continuous and broken yellow markings. /

marshal |verb| to direct aircraft into their parking positions on the apron by means of hand signals / After taxiing, a marshaller marshals the aircraft to the disembarkation and unloading point. /


marshaller |noun| a member of ground staff whose job is to direct aircraft into parking positions by means of hand signals ‘…when under a marshaller’s control, reduce speed to a walking pace’ [ Civil Aviation Authority, General Aviation Safety Sense Leaflet]


marshaling signals |plural noun| hand signals used by a marshaller / Marshaling signals are used to direct aircraft on the ground. /


MAS |abbreviation| middle airspace service


mask |noun| a device to cover the face - oxygen mask > a device to cover the nose and mouth which is connected to an oxygen supply / Anoxia at high altitudes can be overcome by breathing through an oxygen mask. / - |verb| to hide or cover up / When practicing instrument flying, the aircraft windows are masked to prevent the (student) pilot from seeing out of the aircraft. /


MASPS |abbreviation| minimum aircraft system performance specifications


mass |noun|  1. the physical volume of a solid body / Mass is a basic property of matter and is called weight when it is in a field of gravity such as that of the Earth. /  2. a large body of something with no particular shape / a land mass such as the continent of Africa / - |adjective| involving a large number of people or things - mass exit > the departure of everybody, or nearly everybody, from a place


mass ascent |noun| a slow ascent of a large body of air in regions of low pressure and of warm air rising over a cold air mass


mast |noun|  1. a vertical pole for a flag or antenna / Ice accretes on the leading edge of the detector mast. /  2. a tube projecting from the underside of the aircraft from which liquid can drain well away from the airframe


master |adjective| main or principal - master cylinder > a hydraulic cylinder from which pressure is transmitted to smaller slave cylinders - |verb| to overcome the difficulty of something / It takes practice to master crosswind landings in light aircraft. /


master key |noun| a key which can open a number of doors, etc.


master switch |noun| the most important of a number of switches operating a system


match |verb|  1. to go well together / The most important factor when matching a propeller to an engine is tip velocity. /  2. to be equal to / The polarization of the antenna must match that of the transmitter. /


material |noun| a substance out of which something can be made / Wood, fabric and paper are all free-burning materials. /


MATO |abbreviation| military air traffic operations


matrix |noun| a grid-like arrangement of circuit elements / Oil coolers consist of a matrix, divided into sections by baffle plates. /


matter |noun|  1. a physical substance / Mass is a basic property of matter. / - foreign matter > something unwanted which is found in a substance or a device (such as sand or water in fuel) / Turbine blades can be damaged by foreign matter such as stones entering through the engine intake on take-off. / - solid matter > solid substances  2. a subject for discussion, concern or action / Safety is a matter of great importance. /  3. trouble or difficulty - what’s the matter? > what’s the problem? - it doesn’t matter > it isn’t important, so don’t worry


MATZ |abbreviation| military aerodrome traffic zone


maximum |adjective| greatest possible / The maximum daily temperature is 35°C. The maximum speed of the aircraft is 200 kt. / - |noun| the greatest possible quantity, amount, etc. / There is a net gain of heat by the Earth until terrestrial radiation balances solar radiation when the daily temperature is at its maximum. /

maximum landing weight |noun| the weight at which an aircraft can land without risking structural damage. Abbreviation: MLW

maximum total weight authorized |noun| the maximum authorized weight of aircraft fuel, payload, etc., given in the Certificate of Airworthiness. Abbreviation: MTWA


mb |abbreviation| millibar

MCP |abbreviation| Mode Control Panel

MD-83 |noun| a McDonnell Douglas narrow-body jet aircraft of an older generation (1990s) with twin engines mounted on the rear fuselage; it was derived from the earlier DC-9 and resulted in the later MD-90 series

MDA |abbreviation| minimum descent altitude

meal tray |noun| a flat support containing food / Catering delivered 139 standard and 21 vegetarian meal trays. /

mean |adjective| referring to something average, midway between two extremes - mean daily temperature > average daily temperature - mean wind > the average speed of a wind - |noun| something having a medium or average position, midway between two extremes - arithmetic mean > the average value of a set of numbers - |verb|  1. to signify or to have something as an explanation / Airspeed means the speed of the aircraft in relation to the air around it. /  2. to intend to do something / I meant to telephone the reservations desk this morning but I forgot. /  3. to result in / Installing a new computer network means a lot of problems for everybody. / (NOTE: meaning – meant)


mean effective pressure |noun| the average pressure exerted on the piston during the power stroke. Abbreviation: MEP


means |noun| a way of doing something which brings a result / A clear window fitted in the reservoir provides a means of checking hydraulic fluid level during servicing. / (NOTE: Means has no plural form.) - by means of > by using / Fuel is transferred from the tanks to the carburetor by means of pipes. / - there are various means for navigation > there are various different methods used for the purposes of navigation


mean sea level |noun| the average level of the sea taking tidal variations into account / Below FL50 cloud heights are referred to a datum of mean sea level. / Abbreviation: MSL


mean sun |noun| the position of an imaginary sun in a solar day of exactly 24 hours, behind the real sun in February and in advance of the real sun in November / Local mean time (LMT) is the time according to the mean sun. /


mean time between failures |noun| full form of MTBF


mean time to repair |noun| full form of MTTR


measure |noun|  1. an indication or way of assessing / The way he dealt with the in-flight emergency is a measure of his skill as a pilot. /  2. a reference for discovering the dimensions or amount of something / The liter is a measure of capacity. /  3. a device used for measuring - a 1-metre measure > a ruler that is 1 meter long  4. an action taken to get a result / Stricter safety measures were introduced. /  5. an amount of something / To be a good pilot, you need a measure of self-confidence. / - |verb|  1. to find the dimensions or amount of something / Wind directions are measured from magnetic north. /  2. to be of a particular size, length, quantity, etc. / How much does the pipe measure? /


measurement |noun|  1. an act of measuring / Measurement of relative humidity is done using an instrument called a hygrometer. /  2. the result of measuring / The measurements of the room are: height = 4 meters, length = 10 meters, width = 4 meters. /


mechanical |adjective| referring to machines / Activation may be electrical or mechanical. / - mechanical pump > a pump operated by the engine rather than by electrical power


mechanical advantage |noun| the ratio of the output force produced by a machine to the input force


mechanical engineering |noun| the study of design, construction, and use of machinery or mechanical structures / She gained a degree in mechanical engineering from university. /


mechanical linkage |noun| a system of rods, cables and levers in a light aircraft, which connect the control column in the cockpit to the control surfaces on the wings, tailplane and fin


mechanics |noun|  1. the study of the action of forces on matter or material systems  2. the way something works / The mechanics of the föhn wind provide a good illustration of the adiabatic process. /


mechanism |noun| 1. the arrangement of connected parts in a machine or system / the landing gear mechanism, the nose wheel steering mechanism / 2. a physical process / the mechanism by which thunderstorms develop /


MEDA |abbreviation| military emergency division aerodrome


medical certificate |noun| a document which confirms that the named person has been medically examined and declared to be in good physical condition


medical emergency |noun| a situation when somebody is unwell and quickly needs medical care


medium |adjective| referring to something that has a position or represents a condition midway between extremes - |noun| a substance through which something else is transmitted or carried / Tubes convey the cooling medium. The cooling medium for cooling oil can be ram-air or fuel. /


medium frequency, medium frequency band |noun| radio frequency range between 300 kHz and 3000 kHz – often referred to as medium wave (MW). Abbreviation: MF

medium haul flight |noun| a medium range flight / Medium haul flights usually last from between three to five hours. /

mega- |prefix| large. Opposite: micro- (NOTE: The prefix mega- is used in front of SI units to indicate one million: megahertz = one million hertz.)


megahertz |noun| a measure of frequency equal to one million cycles per second. Abbreviation: MHz

MEL |abbreviation| Minimum Equipment List

melt |verb| to become liquid by heating / Ice melts at temperatures above freezing. / - melting point > temperature at which a solid turns to liquid / Magnesium has a melting point of 1204°F. /


member |noun|  1. a large, important structural unit / The skin is bonded to the internal members. A beam is a member which is designed to withstand loading applied at an angle to it, often perpendicular. /  2. a person who joins a club or organization / He is a member of the gliding club. /  3. a person in a team or crew / Most large passenger aircraft are now operated by two crew members. /


memorize |verb| to fix in the memory, to learn by heart / It is helpful if a student pilot can memorize certain items, such as downwind checks, early in his training. /


memory |noun|  1. the mental ability of remembering and recalling past events or information - he has a good memory > he remembers things easily  2. part of a computer which is used for the fast recall of information / The computer cannot run many programs at the same time because it doesn’t have enough memory. /


mental |adjective| referring to the mind or brain / Anoxia severely limits physical and mental performance. / - mental calculation > a calculation done in your head, without using aids such as pen, paper or calculator


mention |verb| to refer to something briefly / No one mentioned the incident. /


MEP |abbreviation| mean effective pressure


Mercator’s projection |noun| a map projection of the Earth onto a cylinder so that all the parallels of latitude are the same length as the equator / Since meridians on this projection are represented by parallel straight lines, it is impossible to represent the poles on Mercator’s projection. /


mercury |noun| a silver-colored metallic element, liquid at room temperature, used in thermometers / Manifold pressure gauges are calibrated in inches of mercury. /


mercury barometer |noun| type of barometer where the atmospheric pressure is balanced against a column of mercury / The principle of a mercury barometer has not changed since 1643 when Torricelli demonstrated that the atmosphere can support a column of liquid. /


meridian |noun| an imaginary great circle on the Earth’s surface passing through the north and south geographic poles


mesh |noun| a net-like structure - |verb| (of gears) to link together with cogs on another wheel


message |noun| a short written, coded or verbal communication / The crew can use the public address system to broadcast messages to the passengers. There’s a message from Mr.Jones on your desk. /


met |abbreviation| meteorology, meteorological, relating to the weather / met office, met report /

met office |noun| shorter for meteorological office: an organization gathering and distributing updated weather reports and forecasts / The met office has announced the likelihood of electric storms in the vicinity of Adis Ababa. /

metal |noun| one of the metallic elements e.g. iron, gold, mercury, copper, aluminum

metal debris |noun| parts which may become detached from aircraft during take-off and landing and can have devastating effects as was shown by the Air France Concorde accident at Charles de Gaulle

metallic |adjective| referring to or like metal - metallic materials > metals such as aluminum, titanium, steel, etc. / Some fire extinguishers do not harm metallic, wooden, plastic or fabric materials. / - non-metallic materials > wood, plastics, fabrics, etc., which are not made of metal


METAR |abbreviation| aviation routine weather report, a weather report from an airport or weather station often used by pilots as a print-out during the pre-flight briefing. It can be obtained for any location in the world and is usually updated hourly


meteorological |adjective| referring to meteorology - meteorological forecast > a prediction of the weather to come - meteorological visibility > the greatest horizontal distance at which objects can be seen and recognized by an observer on the ground with normal eyesight and under conditions of normal daylight illumination / Meteorological visibility is given in meters up to 5,000 meters, and thereafter in kilometers. /


meteorological chart |noun| a chart of part of the Earth’s surface with information about weather conditions


meteorological conditions |plural noun| a description of the weather in a given area


meteorologist |noun| a person who studies, reports and forecasts the weather / The analysis of the surface chart is the procedure in which the meteorologist completes the chart by inserting the fronts and isobars in their correct positions. /


meteorology |noun| a science which studies weather and weather conditions /Terrestrial radiation plays an important part in meteorology./


meter |noun|  1. US same as meter  2. a device to measure current, rate of flow, vertical distance, speed, etc.


methanol |noun| a colorless, toxic, flammable liquid, CH3OH, used as an antifreeze, a general solvent, and a fuel, also called methyl alcohol or wood alcohol / Power output can be restored, or can be boosted to a value over 100% maximum power, by the injection of a water/methanol mixture at the compressor inlet or at the combustion chamber inlet. /


method |noun| a particular way of doing something, especially if it is well thought out and systematic / The most common method of displaying radar information is on a cathode ray tube. /


metre |noun| an international standard unit of length, approximately equivalent to 39.37 inches. Abbreviation: m (NOTE: It is also written meter in US English.)


MF |abbreviation| medium frequency


MFD |abbreviation| multifunction display


MHz |symbol| megahertz


micro- |prefix| small. Opposite: mega- (NOTE: The prefix micro- is used in front of SI units to indicate a one millionth part: microsecond = one millionth of a second.)


micro-burst |noun| a particularly strong wind-shear especially associated with thunderstorms / The investigation revealed that the crew lost control of the aircraft as it flew through the micro-burst. /


microlight |noun| a small light aircraft, often with an open fuselage, that can carry one or two people at low speeds and is used for flying for pleasure or reconnaissance


micro-switch |noun| a miniature switch used to govern systems automatically / Operation of an aircraft may also be seriously affected by the freezing of moisture in controls, hinges and micro-switches. / (NOTE: The plural form is micro-switches.)


microwave landing system |noun| an extremely accurate guidance system for landing aircraft that uses microwaves. Abbreviation: MLS


mid- |prefix| middle - mid-summer > the middle of the summer


mid-air |adjective| - mid-air collision > collision between aircraft in the air rather than on the ground


middle |adjective| in the center / middle marker / - |noun| the center / the seat in the middle of the row /


middle airspace service |noun| a radar service provided by an air traffic control area radar unit in the airspace between FL100 and FL245. Abbreviation: MAS


middle marker |noun| an ILS marker beacon on extended runway center line, usually 3500 feet from the runway threshold


MIL |abbreviation| military


mile |noun| - statute mile


military |adjective| relating to war or to the armed services


milk run |noun| a routine trip, especially an airline’s regular flight


millibar |noun| a unit of atmospheric pressure equal to 1 thousandth of a bar. Symbol: mb


milligram |noun| one thousandth of a gram


millilitre |noun| one thousandth of a liter (NOTE: It is usually written ml after figures: 35ml. Also written milliliter in US English.)


millimetre |noun| one thousandth of a meter (NOTE: It is usually written mm after figures: 35mm. Also written millimeter in US English.)


min |abbreviation| minimum, minima


minimal |adjective| very small in amount, importance or degree / Safety equipment carried on some light aircraft may be as minimal as a portable fire extinguisher. Any attempt to increase range by applying power is of minimal benefit. /


minimize |verb| to reduce or decrease to the smallest amount possible


minimum |adjective| smallest possible / Minimum weather requirements for a particular operation such as runway visual range (RVR). / - |noun| the smallest or least possible quantity or amount / Fires should be tackled with the minimum of delay. To keep the weight of the fuselage structure to a minimum, the difference between cabin pressures and the external atmospheric pressures should be kept to a minimum. / (NOTE: The plural form is minima or minimums.)

minimum approach speed |noun| the fact that each aircraft type (B737, A320 etc.) will have a minimum speed at which it can safely fly in a given configuration, i.e. clean configuration (all flaps and gear retracted) and then with flaps and slats extended to different degrees (5°, 15°, 25° etc.) and the gear extended. This speed will decrease as the flaps, slats and gear are extended.

Minimum Descent Altitude |noun| the altitude in the terminal area (around the airport) below which no aircraft must descend unless it is on its approach path. In some airports, the MDA will be different in different directions depending on the terrain. Abbreviation: MDA

Minimum Equipment List |noun| a list of instruments and equipment on an aircraft which must be serviceable before the aircraft can be dispatched: if they are in doubt, the flight crew refers to the MEL. The MMEL (Master Minimum Equipment List) provides a list of equipment which are allowed to be inoperative under certain conditions when the aircraft is dispatched. Abbreviation: MEL

minimum flying speed |noun| the lowest true air speed at which an aircraft can maintain height


minimum fuel |noun| the amount of fuel required to reach destination and land without delay

Minimum Safe Altitude |noun| an altitude in the terminal area below which aircraft should not descend except on approach. Abbreviation: MSA

minimum sector altitude |noun| the lowest altitude at which an aircraft may fly under emergency conditions and which will provide a minimum clearance of 1000 ft above all obstacles located within a particular sector


minimum separation |noun| the minimum vertical or horizontal distance allowed between two aircraft


minor |noun| a person under the age of legal adulthood - |adjective| small in size or amount and therefore relatively unimportant. Opposite: major - minor repairs > repairs which can be made quickly and with the minimum amount of equipment


minus |preposition| reduced by / 6 minus 2 equals 4 (6 – 2 = 4). / - |noun| a minus sign (-) / minus forty degrees Celsius (- 40° Celsius) /


minute |noun|  1. a time period of 60 seconds / There are 60 minutes in one hour. / - wait a minute > wait a while or a short period of time  2. a unit of angular measurement equal to one sixtieth of a degree / 20 degrees and 20 minutes east (20° 20’E). / - |adjective| very small indeed / Metal fatigue begins as minute cracks, too small to be seen, at the point of maximum stress. /


miscellaneous |adjective| various, mixed, not all the same / The first aid box contains miscellaneous items for use in a medical emergency. /


miss |verb| not to get or catch / Two passengers arrived so late that they missed the flight. / - |noun| a near-collision, an airprox / It was a near miss, as separation was reduced to 650 feet vertically and 1,200 meters horizontally. /


missed approach |noun| an approach that does not result in a landing and is followed by a go-around


missed approach point |noun| the point at which a pilot must carry out a missed approach procedure if a particular visual reference has not been made


missed approach procedure |noun| the action and flight path to be followed after a missed approach at a particular aerodrome


mist |noun|  1. visible water vapor, in the form of very fine droplets, in the atmosphere / Mist is thinner than fog. /  2. liquid in spray form - |verb| - to mist up > to become covered in tiny water droplets and therefore prevent clear vision through a surface / The windscreen misted up. /

misunderstanding |noun| understanding incorrectly / There was a misunderstanding between the pilot and the controller and the crew continued their descent. /

mitigate |verb| to make less serious / The crew made a long approach to mitigate the risk of landing long. /

mix |verb| to put together in order to form one mass / It is a fact of nature that different air masses do not mix together. /


mixture |noun| something which is the result of a number of things mixed together


mixture control |noun| a device for controlling the ratio of fuel to air entering an engine’s carburetor or fuel injection system. / The mixture control is a knob or lever marked in red usually to the right of the throttle lever. In order to stop the engine, the mixture control should be moved fully aft. /

MLG |abbreviation| main landing gear

MLS |abbreviation| microwave landing system

MLW |abbreviation| maximum landing weight

mm |abbreviation| millimeter


MM |abbreviation| middle marker


MMR |abbreviation| multi-mode receiver


mnemonic |noun| something such as a word, sentence or little poem which helps the memory (NOTE: Some of the well known mnemonics are: ARROW = Airworthiness Certificate, Registration Document, Radio Station License, Operating Handbook, Weight and Balance document – documents to be carried in (light) aircraft (U5); BUMF checks = Brakes, Undercarriage, Mixture, Fuel – downwind checks in a light, single engine aircraft with a fixed-pitch propeller; FREDA = Fuel, Radio, Engine, Direction indicator, Altimeter – airfield approach checks; HASELL = Height, Airframe, Security, Engine, Location, Lookout – pre-stall checks; variation east, magnetic least: variation west, magnetic best = a mnemonic to help remember whether to add or subtract variation.)


MOA |abbreviation| military operations area

mobile lounge |noun| a telescopic vehicle able to transport passengers and enable them to board directly at outlying stands

mode |noun|  1. a particular selected setting for the operation or functioning of equipment  2. a letter or number given to the various pulse spacings of airborne transponders and ground interrogators /Mode A and mode C for altitude reporting, are used in air traffic control./

Mode Control Panel |noun| a control panel on the glare-shield which, on a Boeing aircraft, fulfills the same function as a Flight Control Unit (FCU) on an Airbus aircraft, i.e. entering altitude, heading, speed, vertical speed (rate of climb / descent) values into the autopilot and auto-thrust / auto-throttle. Abbreviation: MCP

model |noun| a simplified description of a system, often in mathematical form, designed to make calculation simpler / The description of the weather patterns is a model only which, in reality, is modified greatly by a number of factors. /


moderate |adjective|  1. referring to something well within limits, not extreme - a moderate climate > a climate which is not too hot, not too cold  2. the middle of three descriptions of intensity or amount, i.e. light, moderate, severe - moderate humidity > humidity which is not light or severe - light to moderate > varying between light and moderate - moderate to severe > varying between moderate and severe - |verb| to become or cause to become less extreme / The south west wind moderates the climate of the UK. As the wind moderated, the aircraft was allowed to take off. /


modern |adjective| up to date, referring to the present day / Modern engines are far more powerful than engines used in the past. /


modification |noun| an alteration or change in character or form which is normally an improvement / There have been many modifications to the simple carburetor over the years. As a result of the crash, modifications were made to the rudder linkage. /


modify |verb| to change or alter in order to improve / The landing gear was modified to provide greater strength. / (NOTE: modifying – modified)


modulate |verb| to change the frequency, amplitude, phase, or other characteristic of an electromagnetic wave / The ground station transmits a code in two short bursts, each of which is modulated with two tones. /


modulation |noun| a change in a property of an electromagnetic wave or signal, such as its amplitude, frequency, or phase / Pulse modulation is a series of quick, short bursts of energy which are radiated from an antenna which serves both the transmitter and the receiver. /


module |noun| a replaceable detachable unit


moist |adjective| a little wet, damp or humid / Warm moist air from the Gulf of Mexico can extend into Canada. /


moisture |noun| water or other liquid / When the air passing through the carburetor is reduced below 0°C (Celsius), any moisture in the air changes into ice. /


moisture content |noun| the amount of water in the atmosphere or as seen when it condenses onto cold surfaces


mold |noun|,|verb| US same as mould


molecule |noun| the smallest particle into which an element or a compound can be divided without changing its chemical and physical properties / The molecules of a gas move more quickly than the molecules of a liquid. /

molten |adjective| fused or melted / Molten plastic and metal were found at the scene of the fire. /

moment |noun|  1. a short period of time / It only takes a moment to fill in the log book. /  2. a point in time - at the moment > at this particular time / He’s not in the office at the moment. /  3. the product of a quantity and its perpendicular distance from a reference point / A load on the end of a beam creates a bending moment. /  4. the tendency to cause rotation about a point or an axis / The tailplane provides a pitching moment to keep the aircraft level. /


momentum |noun| a measure of the motion of a body equal to the product of its mass and velocity / In rain, the faster an aircraft travels the more water it meets and the greater the relative momentum of the water droplets. /


monitor |noun| a visual display unit for a computer - |verb| to check, on a continuing basis / Flow-meters are fitted which allow crew to monitor the flow of fuel to each engine. /


monitor system |noun| system for checking and warning


monocoque |noun| a three-dimensional body with all the strength in the skin and immediately underlying framework / In monocoque construction there is no internal stiffening, as the thickness of the skin gives the strength and stability. /


monoplane |noun| an aircraft that has only one pair of wings


monsoon |noun| a wind from the south-west or south that brings heavy rainfall to southern Asia in the summer / Although the monsoon winds are thought of as being Asiatic phenomena, they do occur over Africa and parts of North America, especially the Gulf of Mexico. / - monsoon season > a season of wind and heavy rainfall in tropical countries


morning mist |noun| a mist which usually disappears before midday, as the result of warming from the sun


Morse |noun| a code used for transmitting messages in which letters of the alphabet and numbers are represented by dots and dashes or short and long signals / VOR (very high frequency omni-directional radio range) stations transmit a 2 or 3-letter aural Morse call-sign on the reference signal at least every 30 seconds. / (NOTE: Morse is still used for identifying some radio beacons.)


motion |noun| movement, the act of changing position or place - horizontal motion > movement from side to side - rotary motion > circular movement - vertical motion > up and down movement


MOTNE |noun| a network for the exchange of meteorological information needed by meteorological offices, VOLMET broadcasting stations, air traffic service units, operators and other aeronautical users. Full form: Meteorological Operational Telecommunications Network Europe


motor |noun| a machine which provides power for moving a vehicle or device with moving parts (NOTE: Piston or jet power plants for aircraft are referred to as engines not motors.)


mould |noun| a hollow shape for forming plastics, etc. / Moulds are used in the manufacture of plastic components. / - |verb| to shape, often using a mould / Thermo-plastic material become soft when heated and can be moulded again and again. / (NOTE: It is also written mold in US English.)


mount |verb| to fix to a support / A propeller consists of a number of separate blades mounted in a hub. /


mountain |noun| a mass of rock rising above ground level, higher than a hill / They flew over mountains in the south of the country. /


Mountain Standard Time |noun| a time zone of the west-central part of the USA and Canada, 7 hours behind GMT

mountain wave effect |noun| the result of a powerful air mass immediately downstream of a transverse mountain range, rotating about a horizontal axis

mounted |adjective| fixed to a support - rear-mounted > mounted at the rear of the aircraft / Some aircraft such as the Boeing 727 have rear-mounted engines. /


mounting |noun| a supporting component or attachment point / Airbus aircraft have engine mountings under the wings. /


movement |noun| a change in place or position / The upward movement of the piston compresses the fuel/air mixture. / - movement of the crankshaft > the rotation of the crankshaft - the downward movement of cool air > the downward flow of cool air


mph |abbreviation| miles per hour

MSA |abbreviation| Minimum Safe Altitude

MSL |abbreviation| mean sea level


MTA |abbreviation| military training area


MTBF |noun| the average period of time that a piece of equipment will operate between problems. Full form: mean time between failures


MTTR |noun| the average period of time required to repair a faulty piece of equipment. Full form: mean time to repair


MTWA |abbreviation| maximum total weight authorized

mud |noun| a soft wet earth

muff |noun| - acoustic ear muffs


multi- |prefix| multiple or many


multi-engine, multi-engined |adjective| - multi-engine(d) aircraft > aircraft with more than two engines


multifunction display |noun| an electronic cockpit instrument which displays information such as weather radar or navigation data. Abbreviation: MFD


multi-mode receiver |noun| a type of radio receiver used in navigation and landing that can receive signals from a variety of different transmission systems


multiplane |noun| an aircraft with more than one pair of wings


multiple |adjective| many / Auto-land system redundancy employs multiple systems operating in such a manner that a single failure within a system will have little effect on the aircraft’s performance during the approach and landing operation. /


multiplication |noun| a mathematical operation to work out a specified number of times the value of a number (NOTE: The multiplication sign is x.)


multiply |verb| to work out a specified number of times the value of a number / To multiply 20 by 6 is to calculate what is 6 times 20 (6 x 20). 4 multiplied by 2 is 8 (4 x 2 = 8). To calculate fuel required, multiply the duration of the flight by the consumption of the engine at the required power. /


multipurpose |adjective| suitable for many different uses - multipurpose tool > a tool which can be used in many different ways


multi-wheel combinations |plural noun| undercarriages consisting of a number of wheels on each unit


mutual |adjective| directed and received in equal amount


mutual inductance |noun| electromagnetic field in one circuit caused by a quickly changing magnetic field in another circuit

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