Alpha
Bismillah
Charlie Delta
Echo
Foxtrot
Golf
Hotel
insaallah Juliett
Kilo
Lima
Mike
November
Oscar
Piaggio Quebec Romeo
Sierra Turks Uniform
Victory Water X-ray
Yankee Zulu Main Page
Mach
mach
The ratio of the aircraft s true airspeed to the speed of sound.mach cone The cone-shaped shock wave produced by an object exceeding the speed of sound.
mach number The ratio of the speed of an airplane to the speed of sound in the same atmospheric conditions; e.g., MACH.82, MACH 1.6.
mach technique [ICAO] Describes a control technique used by air traffic control whereby turbojet aircraft operating successively along suitable routes are cleared to maintain appropriate MACH numbers for a relevant portion of the enroute phase of flight. The principle objective is to achieve improved utilization of the airspace and to ensure that separation between successive aircraft does not decrease below the established minima.
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.
machine bolt The common name for a hex head bolt with uniform threads.
machine language A language used in a computer system made up of zeros and ones. A special program called a compiler converts a programming language into machine language that can be used by the computer.
machine screw A screw fastener with uniform threads that can be screwed into a tapped hole or into a nut. The head of a machine screw can be round, flat, truss, oval, or a fillister-type.
machine-sewn fabric seams Machine-sewn aircraft fabric seams. The most common types of machine-sewn fabric seams include the French fell, folded fell, and plain overlap.
machining The process of forming the surface by cutting away material by turning, planing, shaping, and milling. Normally accomplished with machine operated tools such as lathes, milling machines, shapers, and planers.
machinist A skilled person in the operation of metal-working machine tools such as lathes, shapers, planers, and milling machines.
machmeter A direct-reading indicator installed in the instrument panel of high-speed aircraft that gives the pilot an indication of his flight Mach number. The internal mechanism of a machmeter includes a bellows for measuring the difference between pitot pressure and static pressure, and includes an aneroid that modifies the output from this differential pressure bellows to correct for the changes in altitude.
mackerel sky A meteorological condition of clouds that resemble the scales on a mackerel fish. The clouds consist of rows of altocumulus or cirrocumulus clouds.
macroscale Spatial scales of 1,000 NM or more.
magamp A contraction of magnetic amplified. An amplifier system using saturable reactors to control an output to obtain amplification. See also magnetic amplifier.
magnesium A silver-white, malleable, ductile metallic element with a symbol of Mg and an atomic number of 12. Used to produce light alloys for aircraft construction.
Magnesyn system An AC remote indicating system in which a permanent magnet is used as the rotor. Based upon the synchronous-motor principle, in which the angular position of the rotor of one motor at the measuring source is duplicated by the rotor of the indicator motor. Used in fuel-quantity or fuel-flow measuring systems, position-indicating systems, etc.
magnet A device or material that has the property of attracting or repelling other magnetic materials. Lines of magnetic flux link its external poles, and a conductor cutting across the flux will have a voltage induced into it.
magnet keeper A soft iron bar placed across the north and south poles of a U-shaped magnet. The iron bar produces a closed path through which magnetic lines of force pass.
magnet wire A small-diameter, varnish-insulated copper wire used in coil windings for electromagnets, transformers, motors, and generators.
magnetic amplifier An electronic control device that uses a saturable reactor. The condition of saturation is controlled by the input signal to modulate the flow of a much larger current in the output circuit. It is essentially a multi-coil transformer that controls the amount of load current allowed to flow in the load winding by a small amount of current in the magnetic core. Changing the amount of DC flowing in the magnetic core changes the permeability of the core. This, in turn, changes the amount of inductive reactance that opposes the AC flowing in the load winding.
magnetic bearing The magnetic course to go direct to an NDB station.
magnetic brake 1. A friction brake controlled by an electromagnetic solenoid. The brake can be either actuated or released by electromagnetic action (usually on or off). 2. A brake that uses magnetism to oppose rotation of a disc or drum without any physical contact
to create the slowing force. Often used in motor driven devices and in effect reverses the rotational forces on the motor until the motor comes to a stop. If the reverse forces were not removed when the motor stops, the motor would start to turn the opposite direction.
magnetic bubble memory The memory stored in the form of bubbles or circular areas on a thin film of magnetic media. Used on early digital computers as non-volatile memory, but no longer widely used.
magnetic chuck A metal machining tool that consists of a special work surface that uses electromagnetism to hold the material being machined.
magnetic circuit Any complete path of magnetic lines of flux that leaves the north magnet pole of an electrical machine such as a motor or generator and enters the magnetic south pole.
magnetic circuit breaker A circuit breaker that opens a circuit whenever there is an excess of current flow in the circuit. It works on the principle of electromagnetism. When rated current flow is exceeded, the magnetic field develops enough strength to open a set of contacts and deenergize the circuit.
magnetic compass error Acceleration error, magnetic dip, and turning error. Acceleration error is inherent in magnetic compasses, caused by the force of acceleration acting on the dip compensating weight when the aircraft accelerates or decelerates on an easterly or westerly heading. In compasses compensated for flight in the Northern Hemisphere, when the aircraft accelerates on an easterly or westerly heading, the compass gives the indication that the aircraft is turning to the North. When the aircraft decelerates on either of these headings, the compass gives the indication that the aircraft is turning to the South. Magnetic dip is an error as the result of the north end of the compass trying to dip toward the magnetic poles in the North and South Hemispheres. This is compensated for by adding weights on the south end of the bar magnet in the Northern Hemisphere, and the north end in the Southern Hemisphere. Turning error is caused by the dip compensating weight. It shows up mostly on turns to or from north or south headings and causes the compass to lead or lag the actual turn.
magnetic course The path of an airplane as measured from magnetic north.
magnetic deviation A compass error caused by localized magnetic fields in the airplane attracting the floating magnets in the magnetic compass and deflecting it away from magnetic north.
magnetic drag cup The aluminum or copper cup surrounding the rotating magnet in a simple mechanical tachometer. Eddy currents are generated in this cup by the rotating magnetic field, resulting in eddy currents and attendant magnetic fields. This resultant magnetic field interacts with those of the rotating magnet and the cup then is displaced axially by the rotation.
magnetic drain plug Similar to a chip detector, except some types cannot be powered to show contamination on a warning light in the cockpit. The drain plug consists of two small permanent magnets built into it to attract and hold any ferrous metal particles that can be in the lubricating oil system. Ferrous metal chips on the drain plug indicate the possibility of internal engine failure. Usually located in the lower portion of a sump in the scavenge oil subsystem.
magnetic field The space around a magnet or conductor where magnetic flux is found.
magnetic flux The invisible lines of magnetic force that exist between the poles of a magnet, and which follow the path of least resistance. Traditionally, they are given the direction from north pole to south pole. When an electrical conductor cuts across the lines of magnetic flux, a voltage is produced in the conductor. One line of magnetic force is called one maxwell.
magnetic flux density The unit of field intensity is the gauss. An individual line of force, called a maxwell, in an area of one square centimeter produces a field intensity of one gauss.
magnetic heading The angle between the longitudinal axis of an aircraft and magnetic north.
magnetic hysteresis The tendency of a material to retain magnetism after the magnetizing influence has been removed. Hysteresis loops are graphs that indicate the magnetic properties of different materials.
magnetic north True north direction corrected for variation error.
magnetic north pole The point on the Earth s surface in the Northern Hemisphere where isolines of the Earth s magnetic field converge. Compasses align with the lines of magnetic flux that connect the north and south magnetic poles, with the north-facing pointer directed toward the magnetic north pole. The pole s location is not co-located with the north axis of rotation of the Earth known as true north.
magnetic particle inspection A nondestructive inspection for ferrous metal parts in which the part is magnetized, producing north and south poles across any discontinuity, either on the surface or subsurface. Iron oxide, sometimes mixed with a fluorescent dye, is attracted and held over the discontinuity. The discontinuity shows up as a line of iron oxide. If using fluorescent dye, an ultraviolet light (a black light) shined on the part shows the discontinuity as an incandescent line.
magnetic pickup RPM system A
newer fan speed indicating system that uses a magnetic
pickup in the fan case. Blade motion produces eddy
currents that are
magnetic poles A suspended magnet swinging freely will align itself with the Earth s magnetic poles. One end is labeled N, meaning north-seeking. The opposite end of the magnet is labeled S, meaning south-seeking.
magnetic saturation A magnet s saturated condition in which all of the magnetic domains are lined up in the same direction, and any increase in the magnetic field is not possible.
magnetic shunt A piece of soft iron shunted across the air gap of a magnet used in an electrical measuring instrument. The position of the magnetic shunt can be changed to calibrate the instrument by varying the amount of magnetic flux that crosses the air gap.
magnetic variation The angular difference between the geographic north pole and the magnetic north pole. The exact value of variation depends on the position on the Earth where the measurement is taken.
magnetic wave The component of a radio wave perpendicular to the antenna.
magnetic yoke The mechanical support that completes the magnetic circuit between the poles of a generator. Also used to describe any ferrous material within the magnetic field of a magnet. This material serves as a low impedance path of least resistance route for magnetic lines of flux.
magnetic-drag tachometer A simple mechanical tachometer that contains an aluminum or copper drag cup surrounding a rotating magnet. The magnet is connected to the equipment whose RPM is to be measured and the drag cup is attached to the pointer in the tachometer instrument. Eddy currents are generated in this cup by the rotating magnetic field, resulting in eddy currents and attendant magnetic fields. This resultant magnetic field interacts with those of the rotating magnet and the cup is then displaced axially by the rotation.
magnetism The ability to attract certain materials containing iron and to influence moving electrons.
magneto A self-contained, permanent-magnet AC generator with a set of current interrupter contacts and a step-up transformer. It is used to supply the high voltage required for ignition in an aircraft reciprocating engine.
magneto safety check An operational check on an aircraft reciprocating engine in which the magneto switch is placed in the OFF position with the engine idling to ascertain that the switch actually does ground out both magnetos.
magnetometer An instrument used to measure the intensity of a magnetic field. Also used detect the presence of a metallic object.
magnetomotive force (MMF) The magnetizing force in a magnetic field. Measured in gilberts or ampere-turns.
magnetosphere The magnetic field surrounding a celestial object (Earth , Moon, stars, etc.). Charged particles are trapped within the magnetosphere.
magnetron A vacuum tube that generates power at microwave frequencies. The flow of electrons is controlled by an externally applied magnetic field.
magnitude A condition of size, quantity, or number.
main bus A common voltage tie point for electrical circuits.
main fuel system The fuel distribution system used for all normal engine operating conditions.
main rotor The rotor that supplies the principal lift to a rotorcraft.
main wheels The wheels of an aircraft landing gear that support the major part of the aircraft weight.
maintain 1. Concerning altitude/flight level, the term means to remain at the altitude/flight level specified. The phrase climb and or descend and normally precedes maintain and the altitude assignment; e.g., descend and maintain 5,000. 2. Concerning other ATC instructions, the term is used in its literal sense; e.g., maintain VFR.
maintenance The inspection, overhaul, repair, preservation, and replacement of parts, excluding preventive maintenance.
maintenance manual A manual produced by the manufacturer of an aircraft, aircraft engine, or component, which details the approved methods of maintenance.
maintenance planning friction level The friction level specified in AC 150/5320-12, Measurement, Construction, and Maintenance of Skid Resistant Airport Pavement Surfaces that represents the friction value below which the runway pavement surface remains acceptable for any category or class of aircraft operations but that is beginning to show signs of deterioration. This value will vary depending on the particular friction measurement equipment used.
maintenance release A return to service approval of an aircraft by an authorized A&P technician or IA. Logged in the appropriate maintenance record.
major alteration An alteration not listed in the aircraft, aircraft engine, or propeller specification, and one which might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness.
major axis of an ellipse The longer axis passing through one focus of an ellipse. See also ellipse.
major diameter The diameter of a bolt or a screw to the tip of the threads.
major overhaul The complete disassembly, cleaning, inspection, repair, and reassembly of an aircraft, engine, or other aircraft component in accordance with the manufacturer s specifications, and which will return the device to a serviceable condition.
major repair A repair that, if improperly done, might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness. FAR 43, Appendix A provides guidance on what constitutes major repairs and alterations.
major structural damage Damage to a structure that requires a major repair in order to return it to proper working or operating condition.
make short approach Used by ATC to inform a pilot to alter his traffic pattern so as to make a short final approach.
make-and-break ignition One of the earliest forms of electrical ignitions for internal combustion engines. It produced an arc when two contacts carrying low-voltage current within the cylinder were separated.
male electrical connector The pin contact that completes a circuit by sliding inside a socket (the female connector).
male fitting A fitting designed to be placed, screwed, or bolted into another unit.
malfunction The failure of a part of a component to function; a deviation in the operation of a unit from its intended purpose or design.
malleability The measure of a material s ability to be stretched or shaped by beating it with a hammer or passing through rollers without breaking.
malleable The ability to be stretched or shaped by beating with a hammer or passing through rollers without breaking.
mallet A hammer with a heavy wood, plastic, rubber, or leather head.
mammatus Bulges or pouches that appear under the anvil of a mature cumulonimbus cloud.
mandatory altitude An altitude depicted on an instrument Approach Procedure Chart requiring the aircraft to maintain altitude at the depicted value.
mandatory altitude An altitude depicted on an instrument Approach Procedure Chart requiring the aircraft to maintain altitude at the depicted value.
mandrel 1. Lathe: A tapered shaft that fits into a hole used to support and center a device or piece of material so that it can be machined. 2. Tube bending: A long steel rod with a rounded end inserted into a piece of metal tubing in order to keep the tubing from flattening while it is being bent.
maneuverability The ability of an aircraft to change directions along a flight path and withstand the stresses imposed upon it.
maneuvering In aviation, to move through a specific series of changes in direction, speed and position for a specific purpose. Often used in regards to positioning an aircraft in the landing pattern.
manganese A non-magnetic chemical element of grayish white with a symbol of Mn and an atomic number of 25. Used in the manufacturing of iron, aluminum, and copper alloys.
manganese dioxide A chemical compound used in carbon-zinc batteries to absorb the hydrogen gas that would otherwise insulate the carbon rod when electrons flow from the zinc can to the carbon.
Manganin An alloy of copper, manganese, and nickel.
manifest A list of passengers and cargo carried on any one flight.
manifold A chamber having several outlets through which a liquid or gas is distributed or gathered.
manifold absolute pressure (MAP) The absolute pressure, measured in inches of mercury, existing in the intake manifold of an engine. This is the pressure that forces the fuel-air mixture into the cylinders.
manifold pressure The absolute pressure, measured in inches of mercury, existing in the intake manifold of an engine. This is the pressure that forces the fuel-air mixture into the cylinder.
manometer An instrument consisting of a glass tube filled with a liquid for measuring the pressure of gases or vapors either above or below atmospheric pressure.
manual depressurization valve A back-up valve used to control cabin pressurization by manually controlling the outflow of air from the cabin if the automatic system malfunctions.
manufactured rivet head The preformed head of an aircraft rivet when it is manufactured at the factory. Also referred to as a shop head.
manufacturer In aviation, a person or a company who manufactures aircraft, aircraft engines, or aircraft components.
manufacturing The process of taking raw materials and changing them into finished and usable products.
Marconi antenna A non-directional, quarter-wave antenna utilizing a ground plane that serves as a quarter-wave reflector. Used for transmitting and receiving radio communications in the higher frequency bands.
marginal VFR (MVFR) Weather characterized by ceilings 1,000 to 3,000 feet AGL and/or visibility three to five statute miles.
marine grommet A plastic or metal reinforcement ring designed with a special shield used to keep water spray caused by takeoff and landings from entering the structure. It is normally attached to the underside of wings and control surfaces of fabric-covered aircraft and used to reinforce drain holes that are cut into the fabric.
marker beacon (MB) An electronic navigation facility transmitting a 75 MHz vertical fan or boneshaped radiation pattern. Marker beacons are identified by their modulation frequency and keying code, and when received by compatible airborne equipment, indicate to the pilot, both aurally and visually, that he is passing over the facility.
married needles A term used regarding an engine-rotor tachometer when the hands are superimposed. One hand indicates engine RPM and the other hand indicates the main rotor RPM.
Marvel balancer A universal balancer commonly used throughout the helicopter industry.
masking material Aluminum foil or special paper used during painting to cover areas of an aircraft surface that are not to be sprayed or on which a finish is not to be applied.
masking tape Paper tape that has a sticky surface on one side and generally comes in rolls of varying widths. Used for masking areas during painting.
Maslow s hierarchy of human needs A listing by Abraham Maslow of needs from the most basic to the most fulfilling. These range from physical through safety, social, and ego to self-fulfillment.
Masonite A type of fiberboard.
mass A measure of the amount of material or matter contained in a body. It is the property of a body that causes the force of gravity to give a body weight.
mass flow rate The result of a fluid s density and its linear velocity.
mass production The production of objects in very large quantities in a relatively short time period by the use of complex, and often computerized, equipment.
massive-electrode spark plug Spark plugs using two, three, or four, large nickel-alloy ground electrodes.
mass-type fuel flowmeter A fuel-flow measurement system used with turbine engines that indicates the mass flow rather than the volume flow.
mast In rotorcraft, the component that supports the main rotor.
mast bumping In rotorcraft, the action of the rotor head striking the mast, occurring on underslung rotors only.
master cylinder A combination cylinder, piston, and reservoir used in an aircraft brake system. Fluid is stored when the brakes are not applied and is then forced into the system for braking.
master minimum equipment list (MMEL) A master list developed by the Federal Aviation Administration for an aircraft by make and model delineating the specific equipment allowed to be inoperative during various types of flight operations. The MMEL is the basis for the development of an MEL.
master rod The only connecting rod in a radial engine attached directly to the crankshaft. All of the other rods connect to the master rod rather than the crankshaft.
master switch A single switch designed to control electric power to all circuits in a system.
mat In composites, typically used in the mold making process. Chopped fibers are held together with a binder. When the resin matrix is applied, the binder melts. Typically used with polyester resin systems.
matched gears Two gears used in a set and only replaced in a set.
matching transformer An electronic device used to connect a load and a source of electrical power that differ in their impedance. It consists of a transformer with a primary winding that matches the impedance of the source and a secondary winding that matches the load.
mathematics That branch of science dealing with numbers and their operation.
mating surfaces Two surfaces that come together to form a seal.
matrix In composite construction, the material that bonds the fibers together, and distributes the stress to the fibers. Typically in advanced composites, the matrix is a resin.
matter Any substance that has weight and occupies space.
mature stage In meteorology, the most intense stage of a thunderstorm. Begins when the precipitation-induced downdraft reaches the ground. Usually lasts about 20 minutes.
maximum allowable zero-fuel weight The maximum weight authorized for an aircraft excluding its fuel load.
maximum authorized altitude (MAA)
A published altitude representing the maximum
usable altitude or flight level for an airspace
structure or route segment. It is the highest altitude
on a Federal airway, jet route,
METO
maximum except takeoff power (METO) The maximum continuous power an engine is allowed to develop without any time restrictions.
maximum landing weight The maximum authorized weight of the aircraft for landing.
maximum range The maximum distance an aircraft can travel by flying at the most economical speed and altitude during all stages of flight.
maximum takeoff power The maximum power an engine is allowed to develop for a limited period of time, usually about one minute.
maximum takeoff weight The maximum design weight of any aircraft for takeoff.
maximum weight The maximum allowable weight for an aircraft under any conditions.
maxwell A unit of magnetic flux. One magnetic line of force.
may As related to aircraft maintenance, means that such an item is allowed, but not required.
mayday The international radiotelephony distress signal. When repeated three times, it indicates imminent and grave danger and that immediate assistance is requested.
mean The average of a number of factors. Often used to indicate the mid-point between two extremes.
mean aerodynamic chord (MAC) The chord of an imaginary rectangular airfoil having the same aerodynamic characteristics as that of the actual wing.
mean sea level (MSL) The reference used for measuring altitude above sea level. Mean sea level is the average height of the surface of the sea.
mean solar day The average time it takes the Earth to rotate about its axis in one day.
measuring circuit Any combination of resistors, batteries, and meters that make it possible to measure electrical values.
mechanic In aviation, a person certificated by the FAA as an Airframe and Powerplant (A & P) mechanic. (Mechanics can be certified as either a Powerplant and/or Airframe mechanic.) Aviation Maintenance Technician (AMT) has become the preferred term.
mechanical advantage The increase in force or speed gained by using such devices as levers, pulleys, gears, or hydraulic cylinders.
mechanical blockage thrust reverser A thrust reverser usually of the post exit-type (clamshell) used to reverse the hot exhaust stream of a gas turbine engine to help slow the airplane during landings.
mechanical bond The joining of two or more parts or pieces by mechanical methods such as bolts, rivets, or pins.
mechanical efficiency The ratio of the brake horsepower delivered to the output shaft of an engine to its indicated horsepower.
mechanical energy Energy that expresses itself in mechanical movement or the physical production of work.
mechanical linkage A direct connection between a control and a unit. No remote actuator.
mechanical mixture A mixture of two or more elements or compounds that can be identified by microscopic examination.
mechanical properties Those properties that involve a relationship between strain and stress.
mechanical turbulence The turbulence that results when airflow is slowed by surface friction.
median In mathematics, the number in an ordered set of values below and above which there is an equal number of values. In the list 1,2,3,7,15,16, and 23, the median is seven since there are three numbers smaller and three numbers greater than seven. Note that this differs from the mathematical mean.
medical certificate Short for FAA Airman Medical Certificate. Obtained by passing a physical examination administered by a doctor who is an FAA-authorized Aviation Medical Examiner (AME).
medium bypass turbofan Engines with 2:1 or 3:1 bypass ratios, which is the ratio of the amount of air the fan moves (or bypasses) in relation to the core engine. Also referred to as moderate bypass.
medium frequency (MF) The band of electromagnetic radiation frequencies that lie between 300 kHz and 3 MHz.
medium-frequency radio transmission An outgoing signal from a transmitter broadcasting an electromagnetic radiation frequency between 300 kHz and 3 MHz.
medium-scale integration A method of fabricating integrated circuit (IC) chips to place multiple transistors or logic circuits on one small IC. Medium-scale integration places 10 to 100 circuits on one integrated circuit.
megahertz (MHz) 1,000,000 cycles per second.
megger A high-voltage, high-range ohmmeter that has a built-in (often hand-turned) generator for producing the voltage needed to measure insulation resistance and the resistance between a component and electrical ground. Also referred to as a megohmmeter.
megohmmeter High-resistance measuring instrument incorporating a high-voltage DC generator in the instrument case. Not only does this measure high resistance, it does it with a high enough voltage to cause insulation breakdown if it has been weakened. Also referred to as a megger.
melt A change in the physical state of a material when it goes from a solid to a liquid as a result of absorbing sufficient heat to produce the change.
melting The change of state of a solid to a liquid, as ice to water.
melting point A temperature at which a solid becomes a liquid.
member Any portion of the aircraft structure essential to the whole.
memory effect A reduction in the service capacity of nickel-cadmium cells that occurs when cells on standby service are regularly recharged after being discharged to only a small fraction of their full service capacity.
meniscus The curved upper surface of a column of liquid in a tube. If the liquid wets the tube, the curve will be concave; if the liquid does not wet the tube, the curve will be convex.
mensuration The act or process of measuring.
Mercator projection A map projection where parallel meridians and lines of latitude are straight lines at right angles to the meridians. The distance between lines of latitude increases as they move farther away from the equator.
mercerize See mercerizing.
mercerizing The process of dipping cotton yarn or fabric into a hot solution of caustic soda. It gives the material greater strength and luster and is stronger and more pliable than untreated fabric.
mercury A heavy, silver-colored, toxic, liquid, metallic chemical element with a symbol of Hg and an atomic number of 80. Mercury remains in a liquid state under standard conditions of pressure and temperature. Mercury is approximately 13 times as heavy as water.
mercury barometer A closed glass tube partially filled with mercury, used to determine the pressure exerted by the atmosphere. The standard atmospheric pressure at sea level will hold the mercury in the tube to a height of 760 mm or 29.92 .
mercury cell A primary cell using zinc for the negative electrode, mercuric oxide for the positive electrode, and potassium hydroxide as the electrolyte.
mercury clutch A centrifugal clutch in which mercury is used to engage the clutch.
mercury oxide cell A chemical cell using powdered mercuric oxide and powdered zinc as its pole pieces. The electrolyte is a liquid solution of potassium hydroxide.
mercury switch A switch that makes and breaks the circuit by way of mercury in a glass tube bridging the contacts as the tube is rocked back and forth.
mercury thermometer A thermometer consisting of a glass tube with an extremely small inside diameter to which is attached a small reservoir containing mercury. A temperature scale marked alongside the tube is used to indicate the temperature when the mercury expands up the tube due to a rise in temperature.
mercury trap A container in the pick-up tube of a vacuum cleaner used to retrieve spilled mercury. The mercury is sucked up by the cleaner and deposited in the bottle that prevents it from being sprayed out by the discharge of the cleaner.
mercury vapor lamp A lamp that glows from the excitation of mercury vapor atoms by an electric arc.
mercury-vapor rectifier A rectifier tube containing mercury, which vaporizes during operation and increases the current-carrying capacity of the tube.
mesh The engagement of the teeth of gears.
mesh rating A U.S. sieve number and filtration rating common to fuel filters. Similar to a micron rating, e.g. a 74 micron filter carries an equivalent U.S. sieve number of 200 and has 200 openings per linear inch.
mesopause The outer extent of the mesosphere, slightly more than 280,000 feet MSL, the boundary between the mesosphere and thermosphere.
mesoscale Spatial scales from 1 to 1,000 nautical miles.
mesoscale convective complex (MCC) The nearly circular clusters of thunderstorms 300 NM or more in diameter. MCC develops primarily between the Rockies and the Appalachians during the warmer part of the year.
mesoscale convective systems (MCS) A large cluster of thunderstorms with horizontal dimensions on the order of 100 miles. MCSs are sometimes organized in a long line of thunderstorms (e.g., a squall line) or as a random grouping of thunderstorms. Individual thunderstorms within the MCS may be severe.
mesosphere A layer of the atmosphere between the top of the stratosphere or the ionosphere and the exosphere (about 250-600 miles above the Earth).
metal A chemical possessing most of the following characteristics: usually rather heavy, with a bright and shining surface, malleable, ductile, and a good electrical conductor.
metal chip detector (MCD) An electrical device for warning the aircrew of ferrous particles in the oil. Consists of two magnets separated by a narrow gap or insulator. The detector is found in the bottom of the oil sump. When ferrous particles from the oil are attracted to the magnets and bridge the gap, a circuit is completed and a warning lamp illuminates in the cockpit.
metal fatigue A method of work hardening or cold working of a metal that results from flexing or vibration and which increases the brittleness of the material to its breaking point.
metal foil A very thin sheet of metal such as aluminum foil.
metal oxide rectifier An electronic device that enables one-way flow of current through the flow of electrons from the base material to an oxide layer, but not from the oxide layer to the base material.
metal oxide semiconductor capacitor An electronic device that utilizes metal oxide as a dielectric to create capacitance.
metal oxide semiconductor field effect transistor (MOSFET) A semiconductor whose gate is insulated from the channel. The MOSFET was originally called the insulated-gate FET (IGFET). The MOSFET has an extremely large input impedance. Because the insulating oxide layer is extremely thin, the MOSFET is susceptible to destruction by electrostatic charges. Special precautions are necessary when handling or transporting MOS devices.
metal sheath A close-fitting metal cover.
metal spinning A process of metal forming in which sheet metal is clamped into a lathe along with the male die. A shaping tool is used to force the spinning metal against the die.
metal spraying A method of covering or repairing a material with a coating of metal. The metal to be used for the coating is melted and sprayed out with hot, high-velocity compressed air.
metal-film resistor A resistor in which an oxide of metal is deposited as a film onto a base material. The type of metal and the thickness determine the resistance of the device.
metallic Having the nature of metal or containing metal.
metallic ion concentration cell corrosion Corrosion that results from a concentration of metallic ions in the electrolyte. The area of high concentration of metallic ions is the cathode.
metallic pigment Extremely tiny flakes of metal suspended in paint to produce a sheen.
metallic ring test A test for delaminations in a bonded structure in which a coin or similar object is used to tap on the surface. If the bond is good, a metallic ringing sound will be produced, however, if it is delaminated, a dull thud will be heard.
metallizing 1. To replace the fabric covering on an aircraft structure with sheet metal. 2. A method of metal overlay or metal bonding to repair worn parts
metallurgy The science and technology dealing with metals and their use.
metal-matrix composites (MMC) In composites, fibers bonded together with a metal as the bonding material.
metalworking tools Machines and tools used in the construction and repair of sheet metal structures.
metamerism index A measurement used for scientific color matching. It indicates the way a pigment will look under varying light conditions.
METAR The international weather reporting code that will be introduced in the U.S., after June 1, 1996.
metastable compound A chemical compound that has only a slight margin of stability.
meteor A small particle of matter in the solar system visible only as it burns due to the high temperature caused by friction as the meteor falls through the Earth s atmosphere.
meteorological impact statement An unscheduled planning forecast describing conditions expected to begin within 4 to 12 hours that can impact the flow of air traffic in a specific center s (ARTCC) area.
meteorological visibility A measure of horizontal visibility in a given direction near the Earth s surface, based on sighting of objects in the daytime or unfocused lights of moderate intensity at night.
meteorology The study of weather and atmospheric phenomena.
meter 1. A device used to measure, indicate, or record. 2. The basic unit of length measurement in the metric system equal to approximately 39.37 .
meter fix time/slot time A calculated time to depart the meter fix in order to cross the vertex at the ACLT. This time reflects descent speed adjustment and any applicable time that must be absorbed prior to crossing the meter fix.
meter list display interval A dynamic parameter that controls the number of minutes prior to the flight plan calculated time of arrival at the meter fix for each aircraft, at which time the TCLT is frozen and becomes an ACLT; i.e., the VTA is updated and consequently the
TCLT modified as appropriate until frozen at which time updating is suspended and an ACLT is assigned. When frozen, the flight entry is inserted into the arrival sector s meter list for display on the sector PVD/MDM. MLDI is used if filed true airspeed is less than or equal to freeze speed parameters (FSPD).
metering A method of time-regulating arrival traffic flow into a terminal area so as not to exceed a predetermined terminal acceptance rate.
metering airports Airports adapted for metering and for which optimum flight paths are defined. A maximum of 15 airports can be adapted.
metering device -A device used to measure or control the amount of fluid flow.
metering fix A fix along an established route from over which aircraft will be metered prior to entering terminal airspace. Normally, this fix should be established at a distance from the airport that will facilitate a profile descent 10,000 feet above airport elevation (AAE) or above.
metering jet The calibrated orifice in a fluid-flow system used to control the amount of flow for a given pressure drop across the jet.
metering pin A flow control device such as a tapered pin in an oleo shock absorber used to progressively restrict the passage of fluid from one chamber into the other, cushioning the landing impact. The shape or contour of the metering pin determines the amount of fluid that can flow with the pin in any position other than full in or full out.
metering valve A valve used to control the flow of a fluid.
meter-kilogram The amount of work produced when one kilogram of force acts through a distance of one meter.
methanol wood alcohol A liquid alcohol produced by the distillation of wood pulp.
methyl bromide A fire extinguishing agent (CH3Br). More effective than C02 from a standpoint of weight, but more toxic than CO2. It will seriously corrode aluminum alloy, zinc, and magnesium. Methyl bromide cannot be used in areas where harmful concentrations can enter personnel compartments.
methylene chloride A liquid solvent (CH2CL2) used as the active agent in many paint strippers.
methyl-ethyl-ketone (MEK) A low-cost solvent similar to acetone. Used as a cleaning agent to prepare a surface for painting and as a stripper for certain finishes. Should be used only in well-ventilated areas.
metric horsepower A measurement of power in the metric system of measurement. One metric horsepower is equal to 1.0139 mechanical horsepower in the system of measurement used in the United States.
metric prefixes A system of prefixes that indicate multiples and submultiples of ten. Some of the more common prefixes used are:
Tera 1012
Giga 109
Mega 106
Kilo 103
milli 10-3
micro 10-6
nano 10-9
pico 10-12
mho A unit of electrical conductance; the reciprocal of ohm.
mica A transparent silicate mineral. It is used as an electrical insulator in capacitors and as an insulator for electric irons and heaters.
Micarta A phenolic-type thermosetting resin impregnated cloth. It is used as an electrical insulator and for the manufacturing of control pulleys.
MICRO
mice Small sheet metal, wedge-shaped tabs inserted into the tail pipe of some older turbine engines to reduce the nozzle opening and increase thrust. Used to trim a turbine engine. Also referred to as tail pipe inserts.
micro One millionth (0.000001) of a unit.
microammeter An electrical current measuring instrument capable of measuring current flow in millionths of an ampere.
microballoons Microscopic-size phenolic or glass spheres used to add body with very little weight to a resin when used as a filler or potting compound.
microbarograph An instrument used in meteorology to measure very small changes in pressure.
microbes Microscopic forms of animal life. They exist in water and feed on hydrocarbon aircraft fuel. Microbes form a water-entrapping scum on the bottom of jet aircraft fuel tanks.
microbiological corrosion The deterioration of materials caused directly or indirectly by bacteria, algae, molds, or fungi, either alone or in combination. Microbiological corrosion is significant to aviation when linked to corrosion of airframe components, particularly in fuel tanks and related systems.
microburst A small downburst with outbursts of damaging winds extending 2.5 miles or less. In spite of its small horizontal scale, an intense microburst could induce wind speeds as high as 150 knots.
microcircuit An extremely small electronic component that has a large number of circuit elements combined into a single unit.
microelectronics The branch of electronics that deals with integrated circuits and other small electronic devices.
micro-en route automated radar tracking system (M-EARTS) An automated radar and radar beacon tracking system capable of employing both short-range (ASR) and long-range (ARSR) radars. This microcomputer driven system provides improved tracking, continuous data recording, and use of full digital radar displays.
microfarad (μF ) One millionth (0.000001) of a farad.
microfiche Sheets of film that store reduced-size printed and graphic information. One sheet of microfiche can stores between 24 and 288 individual frames or pages of material on a single 4 x 6 sheet of photographic film. The microfiche film is read on a reader that enlarges the image and can often make a printed copy of the desired page(s), if needed.
microfilm Reproduction of printed material on 35 mm or 16 mm photographic film; used to store vast quantities of written material in a small space. The microfilm is read on a reader that enlarges the image and can make a full size printed copy of the desired page(s), if needed.
microinch One millionth (0.000001) of an inch.
micrometer One millionth (0.000001) of a meter. A micrometer is also referred to as a micron.
micrometer caliper A precision measuring device having a single movable jaw, advanced by a screw. One revolution of the screw advances the jaw 0.025 .
micrometer setting torque wrench A hand-operated torque wrench in which a preset torque is adjusted with a micrometer-type scale. When torque is reached, the handle of the wrench breaks over, indicating the torque to the operator.
micro-microfarad A unit of capacitance equal to one millionth of a millionth of a farad. Also referred to as picofarad.
micron 1. One millionth (0.000001) of a meter, or one thousandth (0.001) of a millimeter (0.000001 meter or 1 x 106 meter). Also referred to as a micrometer. 2. The pressure measurement in a column of mercury: One micron of pressure is equal to 0.001 millimeter of mercury (1 x 106 meter of mercury) at 0 C. 3. One micron is normally used to denote the effectiveness of a filter.
micronic filter A disposable element filter used in hydraulic or pneumatic systems that filters particles as small as one micron.
microorganism An organism of microscopic size, normally bacteria or fungus.
microphone A device for converting sound waves to electric signals.
microprocessor A small central processing unit (CPU) for a microcomputer.
microscale Spatial scales of 1 n.m. or less.
microscope An optical instrument used to magnify extremely small objects so they can be seen by the human eye.
microsecond One millionth (0.000001) of a second.
microshaver An adjustable metal-cutting tool used for shaving the heads of countersunk rivets so they are flush with the surface.
microshaving A process in sheet metalwork in which the head of the countersunk rivet is shaved to absolute smoothness with the surface of the skin.
microswitch An electrical switch used to open or close a circuit with an extremely small movement of the actuator.
microwave landing system A precision instrument approach system operating in the microwave spectrum that normally consists of the following components:
a. Azimuth Station.
b. Elevation Station.
c. Precision Distance Measuring Equipment.
microwaves Electromagnetic radiation with a wavelength between infrared and short-wave radio wavelengths (frequency higher than 1 gigahertz and a wavelength shorter than 30 centimeters).
mid RVR The RVR (runway visual range ) readout values obtained from RVR equipment located midfield of the runway.
middle compass locator A low power, low or medium frequency (L/MF) radio beacon installed at the site of the middle marker of an instrument landing system (ILS).
middle marker A marker beacon that defines a point along the glide slope of an ILS normally located at or near the point of decision height (ILS Category I). It is keyed to transmit alternate dots and dashes, with the alternate dots and dashes keyed at the rate of 95 dot/dash combinations per minute on a 1300 Hz tone, which is received aurally and visually by compatible airborne equipment.
mid-flap The middle flap on a triple-slotted segmented flap.
mid-span shrouds The lugs on fan blades that contact each other to provide a circular support ring. Mid-span shrouds provide strength and reduce vibration.
mid-span weight A weight placed in the mid-span area of a helicopter rotor blade to add inertia to the blade.
mid-wing airplane An airplane having its main aerodynamic surface located in the center of the fuselage.
migrate To move from one place to another. During an inspection, a technician might discover a fastener has moved or migrated from its intended location to another location due to vibration or jostling.
migration See migrate.
mil Commonly used to represent one one-thousandth (0.001) of an inch.
mild steel Steel that contains between 0.05 and 0.25% carbon.
mildew A gray colored parasitic fungus growth that forms on organic matter.
mildewcide An additive to dope or sealers used when covering organic materials to inhibit the growth of mildew.
mile (mi) One statute mile. Equal to 5,280 ft.
mileage break point On IFR charts, points other than intersections or navaids where the mileage is broken down for reasons such as reception distance. The distances between navaids is in a box. A number without an outlined box indicates mileage between any combination of intersections, navaids, or mileage break points. All distances are in Nautical Miles.
miles-in-trail A specified distance between aircraft, normally, in the same stratum associated with the same destination or route of flight.
military authority assumes responsibility for separation of aircraft (MARSA) A condition whereby the military services involved assume responsibility for separation between participating military aircraft in the ATC system. It is used only for required IFR operations that are specified in letters of agreement or other appropriate FAA or military documents.
military operations area (MOA) Airspace established outside of a Class A airspace area to separate or segregate certain nonhazardous military activities from IFR traffic and to identify for VFR traffic where these activities are conducted.
Military Standards (MS) The standards used for aircraft hardware in order to maintain a high degree of quality standards in the manufacturing, repair, and maintenance of aircraft. Originated by the U.S. military services.
military training route (MTR) Airspace of defined vertical and lateral dimensions established for the conduct of military flight training at airspeeds in excess of 250 knots IAS.
mill bit A tool used with a router to remove metal and honeycomb core for repairs to bonded structure.
mill file A single-cut file, tapered slightly in thickness and in width for about one-third of its length.
milli One one-thousandth (0.001) of a unit.
milliameter An electrical current measuring device calibrated to read in milliamperes. 1000 milliamperes = 1 ampere.
milliampere One-thousandth (0.001) of an ampere.
millibar A unit of barometric pressure equal to approximately 0.75 millimeters of mercury. Standard sea level atmospheric pressure is equal to 1,013.2 millibars.
milling machine A metal-working machine tool with a movable table that feeds the work into a rotating milling cutter.
millivolt One-thousandth (0.001) of a volt.
MILSPEC A term used to identify military specifications.
mineral-based hydraulic fluid A petroleum-based hydraulic fluid consisting essentially of kerosene and additives to inhibit corrosion and minimize foaming. It is dyed red and is identified as MIL-H-5606.
miniature screw A screw less than 0.06 in diameter, having a slotted head and threaded for assembly with a preformed internal thread.
minicomputer A small digital computer.
minidisk A mass storage medium used in digital computers. Most common is the 3-1/2-inch diskette, also known as a floppy. Older computers used 8-inch and 5-1/4-inch minidisks. Most modern personal computers use CD ROM disks as well as 3-1/2-inch diskettes.
minima Weather condition requirements established for a particular operation or type of operation; e.g., IFR takeoff or landing, alternate airport for IFR flight plans, VFR flight, etc. See minimums.
minimum crossing altitude The lowest altitude at certain fixes at which an aircraft must cross when proceeding in the direction of a higher minimum enroute IFR altitude (MEA).
minimum descent altitude 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.
minimum enroute altitude (MEA) Typically the lowest published altitude between radio fixes that guarantees adequate navigation signal reception and obstruction clearance (2,000 feet in mountainous areas and 1,000 feet elsewhere).
minimum enroute IFR altitude The lowest published altitude between radio fixes that 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 the airway, segment, or route.
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 MMEL (master minimum equipment list) developed by the FAA and must be approved by the FAA for use. It is specific to an individual aircraft make and model.
minimum friction level The friction level specified in AC 150/5320-12, Measurement, Construction, and Maintenance of Skid Resistant Airport Pavement Surfaces, that represents the minimum recommended wet pavement surface friction value for any turbojet aircraft engaged in LAHSO. This value will vary with the particular friction measurement equipment used.
minimum fuel 1. The minimum fuel specified for weight and balance purposes when computing an adverse loaded center of gravity. It is the quantity of fuel necessary for one half hour of operation at rated maximum continuous power. 2. Indicates that an aircraft s fuel supply has reached a state where, upon reaching the destination, it can accept little or no delay. This is not an emergency situation but merely indicates an emergency situation is possible should any undue delay occur.
minimum holding altitude The lowest altitude prescribed for a holding pattern that assures navigational signal coverage, communications, and meets obstacle clearance requirements.
minimum IFR altitudes Minimum altitudes for IFR operations as prescribed in FAR 91. These altitudes are published on aeronautical charts and prescribed in FAR 95 for airways and routes, and in FAR 97 for standard instrument approach procedures. If no applicable minimum altitude is prescribed in FAR 95 or FAR 97, the following minimum IFR altitude applies:
a. In designated mountainous areas, 2,000 feet above the highest obstacle within a horizontal distance of 4 nautical miles from the course to be flown; or
b. Other than mountainous areas, 1,000 feet above the highest obstacle within a horizontal distance of 4 nautical miles from the course to be flown; or
c. As otherwise authorized by the Administrator or assigned by ATC.
minimum level flight speed The speed below which a gyroplane, the propeller of which is producing maximum thrust, loses altitude.
minimum navigation performance specification A set of standards that 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 (MNPS) 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 CTA s Santa Maria Oceanic, Shanwick Oceanic, and Reykjavik;
d. In the west, the western boundaries of CTA s Reykjavik and Gander Oceanic and New York Oceanic excluding the area west of 60 W and south of 38 30 N.
minimum obstruction clearance altitude (MOCA) The lowest published altitude in effect between radio fixes on VOR airways, off-airway routes, or route segments that meets obstacle clearance requirements for the entire route segment and that assures acceptable navigational signal coverage only within 25 statute (22 nautical) miles of a VOR.
minimum reception altitude The lowest altitude at which an intersection can be determined.
minimum safe altitude (MSA) 1. The minimum altitude specified in FAR 91 for various aircraft operations. 2. Altitudes depicted on approach charts that provide at least 1,000 feet of obstacle clearance for emergency use within a specified distance from the navigation facility upon which a procedure is predicated. These altitudes will be identified as Minimum Sector Altitudes or Emergency Safe Altitudes and are established as follows:
minimum sector altitudes Altitudes depicted on approach charts that provide at least 1,000 feet of obstacle clearance within a 25-mile radius of the navigation facility upon which the procedure is predicated. Sectors depicted on approach charts must be at least 90 degrees in scope. These altitudes are for emergency use only and do not necessarily assure acceptable navigational signal coverage.
Emergency Safe Altitudes Altitudes depicted on approach charts that provide at least 1,000 feet of obstacle clearance in nonmountainous areas and 2,000 feet of obstacle clearance in designated mountainous areas
within a 100-mile radius of the navigation facility upon which the procedure is predicated and normally used only in military procedures. These altitudes are identified on published procedures as Emergency Safe Altitudes.
minimum safe altitude warning A function of the ARTS III computer that aids the controller by alerting him when a tracked Mode C equipped aircraft is below or is predicted by the computer to go below a predetermined minimum safe altitude.
minimum sector altitude [ICAO] The lowest altitude that can be used under emergency conditions to provide a minimum clearance of 300 m (1,000 feet) above all obstacles located in an area contained within a sector of a circle of 46 km (25 NM) radius centered on a radio aid to navigation.
minimum sink airspeed In gliders, the airspeed, as determined by the performance polar, at which the glider will achieve the lowest sink rate. That is, the glider will lose the least amount of altitude per unit of time at minimum sink airspeed.
minimum vectoring altitude (MVA) The lowest MSL altitude at which an IFR aircraft will be vectored by a radar controller, except as otherwise authorized for radar approaches, departures, and missed approaches. The altitude meets IFR obstacle clearance criteria. It may be lower than the published MEA along an airway or J-route segment. It may be utilized for radar vectoring only upon the controller s determination that an adequate radar return is being received from the aircraft being controlled. Charts depicting minimum vectoring altitudes are normally available only to the controllers and not to pilots.
minimum-flow stop Refers to a fuel control design that prevents the power lever from shutting off fuel. A separate shutoff is provided in this case.
minimums Weather condition requirements established for a particular operation or type of operation; e.g., IFR takeoff or landing, alternate airport for IFR flight plans, VFR flight, etc.
minor alteration Any alteration not considered to be a major alteration.
minor axis of an ellipse A straight line that passes through the center of the ellipse and is perpendicular to the major axis.
minor fastener diameter The diameter of a threaded fastener measured at the thread root.
minor repair Any repair not considered a major repair or preventive maintenance. FAR 43, Appendix A provides guidance on what constitutes a major repair or alteration and preventive maintenance..
minority carriers A term used in reference to semiconductor electronic devices. Both electrons and holes are present in a semiconductor. The more abundant charge carriers are called majority carriers; the less abundant are called minority carriers. In N-type semiconductor material, electrons are the majority carriers and holes are the minority carriers. In P-type semiconductor material, the reverse is true. Current leakage in a reverse-bias direction is flow of the minority carriers.
minuend The number from which the subtrahend is subtracted.
minus A negative value. Minus values are indicated by using a short dash in front of the value (-4). A minus sign is used in electricity to indicate a negative condition.
minute 1. Measurement: An angular measurement equal to 1/60 of a degree in a 360 circle (21,600 minutes of angle in a circle.) 2. Time: A unit of time that is equal to 1/60 of an hour or 60 seconds.
minutes-in-trail A specified interval between aircraft expressed in time. This method would more likely be utilized regardless of altitude.
mirror image An object that is an exact duplicate of the original but reversed as if the object were viewed through a mirror.
misalignment A condition that exists when two mating surfaces do not meet or match as they should.
miscible The ability of a material to combine or mix with another material.
misfire The failure of an explosive charge, as in the misfire of a rocket or an engine.
misfiring The interruption of even firing of a reciprocating engine s cylinders.
missed approach 1. A maneuver conducted by a pilot when an instrument approach cannot be completed to a landing. The route of flight and altitude are shown on instrument approach procedure charts. A pilot executing a missed approach prior to the Missed Approach Point (MAP) must continue along the final approach to the MAP. The pilot can climb immediately to the altitude specified in the missed approach procedure. 2. A term used by the pilot to inform ATC that he is executing the missed approach. 3. At locations where ATC radar service is provided, the pilot should conform to radar vectors when provided by ATC in lieu of the published missed approach procedure.
missed approach point A point prescribed in each instrument approach procedure at which a missed approach procedure shall be executed if the required visual reference does not exist.
missed approach procedure [ICAO] The procedure to be followed if the approach cannot be continued.
MIST
missed approach segment See segments of an instrument approach procedure.
mist Tiny droplets of water suspended in the air.
mist coat A very light spray coat of thinner or other volatile solvent with little or no color in it.
miter A cut to the edges of a board or surface in such a way that they will match or fit together.
miter box A device used to guide a hand saw at the proper angle to cut wood or metal in order to form a miter joint.
miter square A small square used for marking the ends of wood or metal for other than right angle cuts.
mixed exhaust On a turbofan, a design that allows the primary and secondary airstreams to mix prior to leaving the engine. A sound attenuation feature of more modern engines. Same as forced exhaust mixer.
mixed icing A combination of clear and rime icing. See also clear ice and rime ice.
mixer 1. A system of bellcranks that prevents the cyclic inputs from changing the collective inputs on a helicopter control system. 2. A circuit in which two frequencies are combined to produce sum and difference frequencies.
mixing ratio The ratio of the mass of water vapor to the mass of dry air.
mixture A combination of matter composed of two or more components that retain their own properties.
mixture control The primary carburetor control for adjusting the fuel-air mixture ratio. It can be either a manual or automatic control, or it can be a combination of both. In the case of the combination, the pilot adjusts for a particular ratio and the automatic control maintains that ratio by compensating for temperature and pressure variations of the atmosphere.
MLS categories 1. MLS Category I An MLS approach procedure that 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. 2. MLS Category II Undefined until data gathering/ analysis completion. 3. MLS Category III Undefined until data gathering/ analysis completion.
MMM (manufacturers maintenance manual) A manual developed by the aircraft manufacturer that includes information prepared for the AMT or technician who performs work on units, components, and systems while they are installed on the airplane. It is normally supplied by the manufacturer and approved by the FAA as part of the original process of certification. It will contain the required instructions for continued airworthiness that must accompany each aircraft when it leaves the factory.
mobile charges Electrons in a semiconductor material that drift within the material from one electrically charged region to another.
mobile test stand An engine run-in stand that is portable and can be used at multiple locations.
Mobius loop A continuous loop with one surface and one edge. Made by twisting one end of a long, thin strip one half turn and attaching this end to the other end of the strip. This creates a loop with one edge and one surface.
mock-up A full-size reproduction of a part or assembly used to determine whether or not all of the components will fit as they are designed. It is also used for instruction when the real object is impractical to use.
mode 1. The manner of doing some operation. 2. The letter or number assigned to a specific pulse spacing of radio signals transmitted or received by ground interrogator or airborne transponder components of the Air Traffic Control Radar Beacon System (ATCRBS). Mode A (military Mode 3) and Mode C (altitude reporting) are used in air traffic control.
mode C intruder alert A function of certain air traffic control automated systems designed to alert radar controllers to existing or pending situations between a tracked target (known IFR or VFR aircraft) and an untracked target (unknown IFR or VFR aircraft) that requires immediate attention/action.
mode (SSR mode) [ICAO] The letter or number assigned to a specific pulse spacing of the interrogation signals transmitted by an interrogator. There are 4 modes, A, B, C and D corresponding to four different interrogation pulse spacings.
model A copy of a real object, which can be life-size, smaller, or larger than the original.
model number A manufacturer s designation of a particular piece of equipment.
modem A modulator-demodulator device used to connect two computers and allow them to communicate.
modification The change in the design or configuration of an original unit.
modify 1. To change something such as an alteration or redesign of an original unit. 2. To change a schedule from the original date or time.
modular maintenance A maintenance procedure that allows replacement of major assemblies, called modules, in a minimum amount of time and expense. The removed module is returned to a repair facility, bench tested, and repaired as needed.
modular structure Standardized units built up as modules.
modulate To change. This normally refers to a radio carrier wave being modulated to transmit audio information.
modulated anti-skid system An anti-skid brake system that senses the rate of deceleration of the wheels. The system maintains just enough pressure in the brakes to hold the tire in a slip condition, yet not allow a skid to develop. It does this by modulating, or continually changing, the pressure in the brake system.
modulated continuous wave A radio code transmission that consists of a carrier wave modulated with a series of short and long bursts.
modulated light Light that is modulated by audio frequency AC voltage. Such light can be received by a photo electric cell and fed into an amplifier to recreate the original audio qualities.
modulation The changing of frequency or amplitude by superimposing an audio frequency on a carrier frequency.
modulator That portion of a transmitter circuit that modulates the carrier wave.
modulus The ratio of a stress load applied to the deformation of a material.
moisture An all-inclusive term denoting water in any or all of its three states.
moisture absorption The pickup of water vapor from air by a material, in reference to vapor withdrawn from the air only, as distinguished from water absorption, which is the gain in weight due to the absorption of water by immersion.
moisture separator A device used in a pneumatic system to separate moisture from the air.
moisture-proof The property of an object that resists absorption of moisture.
mold The hollow form used to give shape to a laminate part while curing.
mold line In metal layout, a line used in the development of the pattern used for forming a piece of sheet metal. It is that part of the formed part that remains flat and is formed by the intersection of the flat surfaces of two sides of a sheet metal part.
mold line dimension The distance from the edge of metal to a mold point or between mold points.
mold release agent A material applied to the surface of a mold that prevents the molded product from sticking to the mold. Also referred to as a parting agent.
molecule The smallest particle of an element or compound that retains all the properties of the substance. Composed of one or more atoms.
molybdenum A metallic element similar to chromium with a symbol of Mo and an atomic number of 42. Used as an alloying agent in most aircraft alloys.
moment The product of the weight of an object in pounds and the distance from the center of gravity of the object to the datum or fulcrum (the point about which a lever rotates) in inches. Moment is used in weight and balance computations and is expressed in pound-inches. The formula used is: Moment = distance x force.
moment index The moment divided by a constant such as 200, 1,000, or 10,000. Its use is to simplify weight and balance computations by eliminating large and unwieldy numbers.
momentum The tendency of a body to continue in motion after being placed in motion.
moment-weight number An identification number or letter indicating a measurement of both weight and center of gravity and used on rotating airfoils for balancing purposes.
Monel A nickel-copper alloy that is extremely resistant to corrosion.
monitor (When used with communication transfer) listen on a specific frequency and stand by for instructions. Under normal circumstances do not establish communications.
monitor alert (MA) A function of the ETMS that provides traffic management personnel with a tool for predicting potential capacity problems in individual operational sectors. The MA is an indication that traffic management personnel need to analyze a particular sector for actual activity and to determine the required action(s), if any, needed to control the demand.
monitor alert parameter (MAP) The number designated for use in monitor alert processing by the ETMS (enhanced traffic management system). The MAP is designated for each operational sector for increments of 15 minutes.
monkey wrench A slang name for an adjustable wrench that has one fixed jaw and one movable jaw.
monocoque A stressed-skin type of construction in which the stiffness of the skin provides a large measure of the strength of the structure. No truss or substructure is required.
monolithic casting A casting formed as a single piece.
monomer A chemical compound that can be polymerized. (Polymerization is a chemical reaction in which two or more molecules are combined to form a larger molecule that contains repeating structural units.)
monoplane An airplane with one main supporting wing sometimes divided into two parts by the fuselage.
monopropellant A rocket engine propellant in which the fuel and the oxidizer are both part of a single substance.
monorail A single rail used to carry cars or objects.
monospar wing A fundamental wing design that incorporates only one main longitudinal member in its construction.
monostable The condition of a device that has one stable condition. When disturbed from this, it will attempt to return to its original state.
monostable multivibrator An electronic circuit that tries to maintain a condition of on or off. When it is disturbed from this position, it will automatically return to its stable condition.
monsoon A wind that blows in the summer from the sea to a continental interior, bringing copious rain, and in winter blows from the interior to the sea, resulting in sustained dry weather.
Morse code A system of dots and dashes used for transmitting messages by audible or visual signals. Used in aviation to identify radio navigation facilities.
most significant bit A bit in a binary number that has the highest value. It is the bit on the far left of a binary number.
most significant digit A digit in a decimal number that is the most meaningful. It is the digit on the far left of a decimal number.
mothball To preserve and store surplus airplanes, parts, or equipment for future use.
mothballed Parts, machinery, or equipment that has been preserved and placed in storage.
mother board The primary printed circuit board in an electronic device into which all other components are connected.
motion The act of changing place or position.
motivation A need or desire that causes a person to act. Motivation can be positive or negative, tangible or intangible, subtle or obvious.
motor bypass A device in a hydraulic system that prevents a hydraulic motor from receiving excessive fluid. The fluid bypasses the motor.
motor over The process of rotating the engine with the starter for reasons other than for starting.
motoring Rotating a turbine engine with the starter for reasons other than starting.
motorization The adding of an electric motor to equipment normally operated manually or by mechanical means other than electric motors.
mountain breeze Occurring on a larger scale than downslope winds, it blows down the valley with a return flow, or anti-mountain wind, above the mountaintops.
mountain wave An atmospheric gravity wave that forms in the lee of a mountain barrier. See lee wave.
mountain wave turbulence (MWT) Turbulence produced in conjunction with the mountain lee wave.
mounting lug A lug used to secure an accessory, cylinder, etc.
mounting pad A provision made on the accessory section of an aircraft engine for attaching such accessories as magnetos, generators or alternators, and fluid pumps.
movement The moving parts of a device that move in a defined manner, i.e., the inner workings of a watch.
movement area The runways, taxiways, and other areas of an airport/heliport utilized for taxiing/hover taxiing, air taxiing, takeoff, and landing of aircraft, exclusive of loading ramps and parking areas. At those airports/ heliports with a tower, specific approval for entry onto the movement area must be obtained from ATC.
movement area [ICAO] That part of an aerodrome to be used for the takeoff, landing and taxiing of aircraft, consisting of the maneuvering area and the apron(s).
moving target indicator An electronic device that permits radar scope presentation only from targets in motion. A partial remedy for ground clutter.
moving-coil meter A d Arsonval meter movement. Most commonly used meter movement in DC measuring instruments. A movable coil on which a pointer is mounted rotates in the field of a permanent magnet. The amount of current in the coil determines the strength of the coil s electromagnetic field and the amount the pointer is deflected by the magnetic field of the permanent magnet.
moving-iron meter movement A d Arsonval meter movement where the coil is fixed and the magnet (iron) is free to move.
muff A shroud placed around a section of the exhaust pipe. The shroud is open at the ends to permit air to flow into the space between the exhaust pipe and the wall of the shroud and be heated. This heated air can be used for carburetor heat or cockpit and cabin heat.
mule An auxiliary hydraulic power supply that can supply fluid under pressure to the aircraft hydraulic system when the engines are not running. The mule is normally used to test the landing gear and flight control systems.
multicell thunderstorm A group of thunderstorm cells at various stages of development. The proximity of the cells allows interaction that prolongs the lifetime of the group beyond that of a single cell.
multicom A mobile service not open to public correspondence used to provide communications essential to conduct the activities being performed by or directed from private aircraft.
multi-engine An aircraft having more than one engine.
multimedia A combination of more than one instructional medium. This format can include audio, text, graphics, animations, and video. Recently, multimedia implies a computer-based presentation.
multimeter A piece of electrical test equipment consisting of one meter movement and several shunts, multipliers, and other circuit elements to allow the meter to be used as a voltmeter, ohmmeter, milliammeter, and ammeter. Rectifiers make it usable for AC and well as DC.
multiple runways The utilization of a dedicated arrival runway(s) for departures and a dedicated departure runway(s) for arrivals when feasible to reduce delays and enhance capacity.
multiple-choice A test item consisting of a question or statement followed by a list of alternative answers.
multiple-disk brake An aircraft brake in which a series of discs, keyed to the wheel, mesh and rotate between a series of stationary discs keyed to the axle. The brakes are applied by hydraulically clamping the discs together.
multiple-spar (multi-spar) wing An airplane wing structure that uses several spanwise structural members to give the wing its strength.
multiplex communications A method of two-way communication in which two sites can transmit and receive on the same frequency and at the same time.
multiplicand Any number to be multiplied by another.
multiplier A number by which another number is multiplied. The factor by which something is multiplied or extended.
multiplier resistor The resistor in series with a voltmeter movement used to multiply or extend the range of the meter.
multiplier tube An electron tube designed to amplify or multiply very weak electron currents by means of secondary emission.
multi-spar wing A fundamental wing design that incorporates more than one spanwise structural member for support.
multivibrator An oscillator that produces its output by having two transistors or vacuum tubes alternately conduct current. When one conducts, the other is shut off. Conduction alternates between the two.
Mumetal A nickel alloy of iron, nickel, chromium, molybdenum, and copper. Used in transformer cores and for shielding electronic devices from external magnetic fields.
muriatic acid Commercial hydrochloric acid (HCl).
mushroom head A flared head that forms on a pounding tool such as a punch or chisel when it is hammered. This is a dangerous condition, and it must be ground away.
mutual inductance The inductance of a voltage in one coil due to the magnetic field produced by an adjacent coil. Inductive coupling is accomplished through the mutual inductance of two adjacent coils.
Mylar A polyester film.
Mylar capacitor A capacitor that uses Mylar film as a dielectric.