Glossary

A small postcard-like form (FAA Form 8330) used by repair stations, maintenance shops, and technicians to report an unacceptable condition to the FAA. Information on these forms provides the basis for the General Airworthiness Alerts and subsequent Airworthiness Directives.

Aviation Maintenance Technician Handbook — Powerplant, p. G-17

Mean aerodynamic chord.

Aircraft Weight and Balance Handbook, p. G-3

The instrument that displays the ratio of the speed of sound to the true airspeed an aircraft is flying.

Pilot's Handbook of Aeronautical Knowledge, p. G-18

The registered trade name of a remote indicating instrument system. A Magnesyn system uses a permanent magnet as its rotor and a toroidal coil excited by 400-hertz AC as its stator. A small magnet in the center of the indicator coil follows the movement of a larger magnet in the transmitter coil.

Aviation Maintenance Technician Handbook — Powerplant, p. G-17

The direction to or from a radio transmitting station measured relative to magnetic north.

Aviation Maintenance Technician Handbook — Airframe, p. G-21; Pilot's Handbook of Aeronautical Knowledge, p. G-18

A device for determining direction measured from magnetic north.

Pilot's Handbook of Aeronautical Knowledge, p. G-18

A vertical attraction between a compass needle and the magnetic poles. The closer the aircraft is to a pole, the more severe the effect.

Pilot's Handbook of Aeronautical Knowledge, p. G-18

The invisible, but measurable, force surrounding a permanent magnet or current-carrying conductor. This field is produced when the orbital axes of the electrons of the atoms in the material are all in alignment.

Aviation Maintenance Technician Handbook — Powerplant, p. G-17

Lines of magnetic force that are assumed to leave a magnet at its north end and return to its south end. Lines of flux tend to be as short as possible and cannot cross each other.

Aviation Maintenance Technician Handbook — Powerplant, p. G-17

The direction an aircraft is pointed with respect to magnetic north.

Pilot's Handbook of Aeronautical Knowledge, p. G-18

A method of detecting invisible cracks and other defects in ferromagnetic materials such as iron and steel. The inspection process consists of magnetizing the part and then applying ferromagnetic particles to the surface area to be inspected.

Aviation Maintenance Technician Handbook — General, p. G-6

A self-contained, engine-driven unit that supplies electrical current to the spark plugs; completely independent of the airplane’s electrical system. Normally there are two magnetos per engine.

Pilot's Handbook of Aeronautical Knowledge, p. G-18

Lifting force produced when a rotating cylinder produces a pressure differential. This is the same effect that makes a baseball curve or a golf ball slice.

Pilot's Handbook of Aeronautical Knowledge, p. G-18

The disassembly, cleaning, and inspection of an engine and the repair and replacement of all parts that do not meet the manufacturer’s specification.

Aviation Maintenance Technician Handbook — Powerplant, p. G-17

A repair that (1) if improperly done, might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness, or (2) is not done according to accepted practices, or cannot be done by elementary operations.

Aviation Maintenance Technician Handbook — General, p. G-6

A report (FAA Form 8010- 4) providing the FAA and industry with a very essential service record of mechanical difficulties encountered in aircraft operations. Such reports contribute to the correction of conditions or situations which otherwise will continue to prove costly and/or adversely affect the airworthiness of aircraft.

Aviation Maintenance Technician Handbook — General, p. G-6

An altitude depicted on an instrument approach chart with the altitude value both underscored and overscored. Aircraft are required to maintain altitude at the depicted value.

Pilot's Handbook of Aeronautical Knowledge, p. G-18

An altitude depicted on an instrument approach chart with two underscored and overscored altitude values between which aircraft are required to maintain altitude.

Pilot's Handbook of Aeronautical Knowledge, p. G-18

A precision steel bar on which a propeller is mounted for balancing. The mandrel is placed across two perfectly level knife-edge plates, and the propeller is allowed to rotate until it stops with its heavy point at the bottom.

Aviation Maintenance Technician Handbook — Powerplant, p. G-17

Ability of an aircraft to change directions along a flight path and withstand the stresses imposed upon it.

Pilot's Handbook of Aeronautical Knowledge, p. G-19

The design maneuvering speed. Operating at or below design maneuvering speed does not provide structural protection against multiple full control inputs in one axis or full control inputs in more than one axis at the same time.

Pilot's Handbook of Aeronautical Knowledge, p. G-19

The absolute pressure of the fuel/air mixture within the intake manifold, usually indicated in inches of mercury.

Pilot's Handbook of Aeronautical Knowledge, p. G-19

A type of fuel system commonly used in large transport category aircraft. All fuel tanks feed into a common manifold, and the dump chutes and the single-point fueling valves are connected to the manifold. Fuel lines to each engine are taken from the manifold.

Aviation Maintenance Technician Handbook — Airframe, p. G-22

A pressure gauge that measures the absolute pressure inside the induction system of a reciprocating engine. When the engine is not operating, this instrument shows the existing atmospheric pressure.

Aviation Maintenance Technician Handbook — Airframe, p. G-22

See flow divider (reciprocating engine).

Aviation Maintenance Technician Handbook — Powerplant, p. G-17

A manual provided by an aircraft manufacturer that outlines the methods, techniques, and practices prescribed for each person performing maintenance, alteration, or preventive maintenance on an aircraft, engine, propeller, or appliance.

Aviation Maintenance Technician Handbook — General, p. G-6

Manifold absolute pressure. The absolute pressure that exists within the induction system of a reciprocating engine. It is the MAP that forces air into the cylinders of the engine. MAP is commonly called manifold pressure.

Aviation Maintenance Technician Handbook — Powerplant, p. G-17

The top and bottom areas on an instrument approach chart that depict information about the procedure, including airport location and procedure identification.

Pilot's Handbook of Aeronautical Knowledge, p. G-19

A low-powered transmitter that directs its signal upward in a small, fan-shaped pattern. Used along the flight path when approaching an airport for landing, marker beacons indicate both aurally and visually when the aircraft is directly over the facility.

Pilot's Handbook of Aeronautical Knowledge, p. G-19

A term used when two hands of an instrument are superimposed over each other, as on the engine/rotor tachometer.

Helicopter Flying Handbook, p. G-4

A measure of the quantity of matter in an object.

Aviation Maintenance Technician Handbook — General, p. G-6

The component that supports the main rotor.

Helicopter Flying Handbook, p. G-4

Action of the rotor head striking the mast, occurring on underslung rotors only.

Helicopter Flying Handbook, p. G-4

A switch in an aircraft electrical system that can disconnect the battery from the bus and open the generator or alternator field circuit.

Aviation Maintenance Technician Handbook — Airframe, p. G-22

The material used in composite construction to bond the fibers together and to transmit the forces into the fibers. Resins are the most widely used matrix materials.

Aviation Maintenance Technician Handbook — Airframe, p. G-22

Any substance that has mass and takes up space.

Aviation Maintenance Technician Handbook — General, p. G-6

An altitude depicted on an instrument approach chart with overscored altitude value at which or below aircraft are required to maintain altitude.

Pilot's Handbook of Aeronautical Knowledge, p. G-19

A published altitude representing the maximum usable altitude or flight level for an airspace structure or route segment.

Pilot's Handbook of Aeronautical Knowledge, p. G-19

The heaviest weight an aircraft can have when it lands. For large wide body commercial airplanes, it can be 100,000 pounds less than maximum takeoff weight, or even more.

Aviation Maintenance Technician Handbook — General, p. G-7

The maximum external load that is permitted for a helicopter to carry. This load is specified in the POH

Aircraft Weight and Balance Handbook, p. G-3

The heaviest weight to which an aircraft can be loaded while it is sitting on the ground, sometimes referred to as the maximum taxi weight.

Aviation Maintenance Technician Handbook — General, p. G-7

The heaviest weight an aircraft can have when it starts the takeoff roll. The difference between this weight and the maximum ramp weight would equal the weight of the fuel that would be consumed prior to takeoff.

Aviation Maintenance Technician Handbook — General, p. G-7

The maximum weight approved for ground maneuvers. This is the same as maximum ramp weight.

Aircraft Weight and Balance Handbook, p. G-4

The maximum authorized weight of the aircraft and its contents, and is indicated in the Aircraft Specifications or Type Certificate Data Sheet.

Aviation Maintenance Technician Handbook — General, p. G-7

The heaviest weight an aircraft can be loaded to without having any usable fuel in the fuel tanks. Any weight loaded above this value must be in the form of fuel.

Aviation Maintenance Technician Handbook — General, p. G-7

See magnetic bearing.

Pilot's Handbook of Aeronautical Knowledge, p. G-19

The average distance from the leading edge to the trailing edge of the wing.

Aviation Maintenance Technician Handbook — General, p. G-7; Aircraft Weight and Balance Handbook, p. G-4; Pilot's Handbook of Aeronautical Knowledge, p. G-19

A line that is drawn midway between the upper and lower camber of an airfoil section. The mean camber determines the aerodynamic characteristics of the airfoil.

Aviation Maintenance Technician Handbook — Airframe, p. G-22

The average height of the surface of the sea at a particular location for all stages of the tide over a 19-year period.

Pilot's Handbook of Aeronautical Knowledge, p. G-19

A ratio of the resistance force to the effort force.

Aviation Maintenance Technician Handbook — General, p. G-7

This includes all methods of producing increased motion of molecules such as friction, impact of bodies, or compression of gases.

Aviation Maintenance Technician Handbook — General, p. G-7

A turbofan engine whose bypass ratio is between 2:1 and 4:1.

Aviation Maintenance Technician Handbook — Powerplant, p. G-18

Methyl-ethyl-ketone is an organic chemical solvent that is soluble in water and is used as a solvent for vinyl and nitrocellulose films. MEK is an efficient cleaner for preparing surfaces for priming or painting.

Aviation Maintenance Technician Handbook — Airframe, p. G-22

A treatment given to cotton thread to make it strong and lustrous. The thread is stretched while it is soaked in a solution of caustic soda.

Aviation Maintenance Technician Handbook — Airframe, p. G-22

Lines of longitude.

Pilot's Handbook of Aeronautical Knowledge, p. G-19

A layer of the atmosphere directly above the stratosphere.

Pilot's Handbook of Aeronautical Knowledge, p. G-19

See Aviation Routine Weather Report.

Pilot's Handbook of Aeronautical Knowledge, p. G-19

Alcohol made from wood.

Aviation Maintenance Technician Handbook — Powerplant, p. G-18

The maximum power allowed to be continuously produced by an engine. Takeoff power is usually limited to a given amount of time, such as 1 minute or 5 minutes.

Aviation Maintenance Technician Handbook — General, p. G-7

Multi-function display.

Aviation Maintenance Technician Handbook — Airframe, p. G-22

See magnetic heading.

Pilot's Handbook of Aeronautical Knowledge, p. G-19

1,000,000 cycles per second.

Aviation Maintenance Technician Handbook — Airframe, p. G-22

A patented graduated series of cloth-backed cushioned seats that contain abrasive crystals. Micro-Mesh is used for polishing and restoring transparency to acrylic plastic windows and windshields.

Aviation Maintenance Technician Handbook — Airframe, p. G-22

An organism, normally bacteria or fungus, or microscopic size.

Aviation Maintenance Technician Handbook — Airframe, p. G-22

Tiny, hollow spheres of glass or phenolic material used to add body to a resin.

Aviation Maintenance Technician Handbook — Airframe, p. G-22

The scum that forms inside the fuel tanks of turbine-engine-powered aircraft that is caused by micro-organisms. These micro-organisms live in water that condenses from fuel, and they feed on the fuel. The scum they form clogs fuel filters, lines, and fuel controls and holds water in contact with the aluminum alloy structure, causing corrosion.

Aviation Maintenance Technician Handbook — Airframe, p. G-22

A strong downdraft which normally occurs over horizontal distances of 1 NM or less and vertical distances of less than 1,000 feet. In spite of its small horizontal scale, an intense microburst could induce windspeeds greater than 100 knots and downdrafts as strong as 6,000 feet per minute.

Pilot's Handbook of Aeronautical Knowledge, p. G-19

A measure used for cylinder wall surface roughness. Twenty microinches rms means that the highest and lowest deviation from the average surface is 20 millionths of an inch.

Aviation Maintenance Technician Handbook — Powerplant, p. G-18

A unit of linear measurement equal to one millionth of a meter, one thousandth of a millimeter, or 0.000039 inch. A micron is also called a micrometer.

Aviation Maintenance Technician Handbook — Airframe, p. G-22

The registered trade name of a type of fluid filter whose filtering element is a specially treated cellulose paper formed into vertical convolutions, or wrinkles. Micronic filters prevent the passage of solids larger than about 10 microns, and are normally replaced with new filters rather than cleaned.

Aviation Maintenance Technician Handbook — Airframe, p. G-22

A single silicon chip that contains the arithmetic and logic functions of a computer.

Aviation Maintenance Technician Handbook — Powerplant, p. G-18

The registered trade name for a precision switch that uses a short throw of the control plunger to actuate the contacts. Microswitches are used primarily as limit switches to control electrical units automatically.

Aviation Maintenance Technician Handbook — Airframe, p. G-22

A precision instrument approach system operating in the microwave spectrum which normally consists of an azimuth station, elevation station, and precision distance measuring equipment.

Pilot's Handbook of Aeronautical Knowledge, p. G-19

Metal inert gas welding is a form of electric arc welding in which the electrode is an expendable wire. MIG welding is now called GMA (gas metal arc) welding.

Aviation Maintenance Technician Handbook — Airframe, p. G-22

One thousandth of an inch (0.001 inch). Paint film thickness is usually measured in mils.

Aviation Maintenance Technician Handbook — Airframe, p. G-22

A gray or white fungus growth that forms on organic materials. Mildew forms on cotton and linen aircraft fabric and destroys its strength.

Aviation Maintenance Technician Handbook — Airframe, p. G-22

A fix indicating a course change that appears on the chart as an “x” at a break between two segments of a federal airway.

Pilot's Handbook of Aeronautical Knowledge, p. G-19

Airspace of defined vertical and lateral dimensions established for the conduct of military training at airspeeds in excess of 250 knots indicated airspeed (KIAS).

Pilot's Handbook of Aeronautical Knowledge, p. G-20

An instrument that measures electrical current in units of thousandths of an ampere.

Aviation Maintenance Technician Handbook — Powerplant, p. G-18

A unit of pressure in the metric system. One bar is a pressure of 14.5 psi, or 29.52 in. Hg. One millibar is one thousandth of a bar, or 0.01469 psi, or 0.02952 in. Hg.

Aviation Maintenance Technician Handbook — Powerplant, p. G-18

An electrical instrument that measures voltage in units of millivolts (thousandths of a volt).

Aviation Maintenance Technician Handbook — Airframe, p. G-22

An altitude depicted on an instrument approach chart with the altitude value underscored. Aircraft are required to maintain altitude at or above the depicted value.

Pilot's Handbook of Aeronautical Knowledge, p. G-20

The lowest allowed altitude at certain fixes an aircraft must cross when proceeding in the direction of a higher minimum en route altitude (MEA).

Pilot's Handbook of Aeronautical Knowledge, p. G-20

The point on the total drag curve where the lift-to-drag ratio is the greatest. At this speed, total drag is minimized.

Pilot's Handbook of Aeronautical Knowledge, p. G-20

The lowest published altitude between radio fixes that ensures acceptable navigational signal coverage and meets obstacle clearance requirements between those fixes.

Pilot's Handbook of Aeronautical Knowledge, p. G-20

A list developed for larger aircraft that outlines equipment that can be inoperative for various types of flight including IFR and icing conditions. This list is based on the master minimum equipment list (MMEL) developed by the FAA and must be approved by the FAA for use. It is specific to an individual aircraft make and model.

Pilot's Handbook of Aeronautical Knowledge, p. G-20

The amount of fuel necessary for one-half hour of operation at the rated maximum-continuous power setting of the engine, which, for weight and balance purposes, is 1⁄12 gallon per maximum-except-takeoff (METO) horse-power. It is the maximum amount of fuel that could be used in weight and balance computations when low fuel might adversely affect the most critical balance conditions. To determine the weight of the minimum fuel in pounds, divide the METO horsepower by two.

Aircraft Weight and Balance Handbook, p. G-4

The lowest published altitude in effect between radio fixes on VOR airways, off-airway routes, or route segments, which meets obstacle clearance requirements for the entire route segment and which ensures acceptable navigational signal coverage only within 25 statute (22 nautical) miles of a VOR.

Pilot's Handbook of Aeronautical Knowledge, p. G-20

The lowest altitude at which an airway intersection can be determined.

Pilot's Handbook of Aeronautical Knowledge, p. G-20

The minimum altitude depicted on approach charts which provides at least 1,000 feet of obstacle clearance for emergency use within a specified distance from the listed navigation facility.

Pilot's Handbook of Aeronautical Knowledge, p. G-20

An IFR altitude lower than the minimum en route altitude (MEA) that provides terrain and obstacle clearance.

Pilot's Handbook of Aeronautical Knowledge, p. G-20

The area on an IAP chart that displays the lowest altitude and visibility requirements for the approach.

Pilot's Handbook of Aeronautical Knowledge, p. G-20

A maneuver conducted by a pilot when an instrument approach cannot be completed to a landing.

Pilot's Handbook of Aeronautical Knowledge, p. G-20

A point prescribed in each instrument approach at which a missed approach procedure shall be executed if the required visual reference has not been established.

Pilot's Handbook of Aeronautical Knowledge, p. G-20

A very light coat of zinc chromate primer. It is so thin that the metal is still visible, but the primer makes pencil marks easy to see.

Aviation Maintenance Technician Handbook — Airframe, p. G-22

A mixture of clear ice and rime ice.

Pilot's Handbook of Aeronautical Knowledge, p. G-20

A combination of a whole number and a fraction. For example, 53⁄8 is a mixed number.

Aviation Maintenance Technician Handbook — General, p. G-7

See microwave landing system.

Pilot's Handbook of Aeronautical Knowledge, p. G-20

See military operations area.

Pilot's Handbook of Aeronautical Knowledge, p. G-20

Altitude reporting transponder mode.

Pilot's Handbook of Aeronautical Knowledge, p. G-20

The method of construction for mast modern gas turbine engine. The engine is made of several modules, or units, that can be removed and replaced or serviced independent of the rest of the engine.

Aviation Maintenance Technician Handbook — Powerplant, p. G-18

A component in a high-pressure pneumatic system that removes most of the water vapor from the compressed air. When the compressed air is used, its pressure drops, and this pressure drop causes a drop in temperature. If any moisture were allowed to remain in the air, it would freeze and block the system.

Aviation Maintenance Technician Handbook — Airframe, p. G-23

A line used in the development of a flat pattern for a formed piece of sheet metal. The mold line is an extension of the flat side of a part beyond the radius. The mold line dimension of a part is the dimension made to the intersection of mold lines and is the dimension the part would have if its corners had no radius.

Aviation Maintenance Technician Handbook — Airframe, p. G-23

The intersection of two mold lines of a part. Mold line dimensions are made between mold points.

Aviation Maintenance Technician Handbook — Airframe, p. G-23

The smallest particle of an element or compound that retains the chemical properties of the element or compound.

Aviation Maintenance Technician Handbook — General, p. G-7

In determining weight and balance, the moment is the product of a weight multiplied by its arm.

Aviation Maintenance Technician Handbook — General, p. G-7

The distance from a datum to the applied force.

Pilot's Handbook of Aeronautical Knowledge, p. G-20

The moment (weight times arm) divided by a reduction factor.

Aircraft Weight and Balance Handbook, p. G-4

An enclosed area on a graph of three parameters. The diagonal line, representing the moment/100, crosses the horizontal line, representing the weight at the vertical line, representing the CG location in inches aft of the datum. If the lines cross inside the envelope, the aircraft is loaded within its weight and CG limits.

Aircraft Weight and Balance Handbook, p. G-4

A force caused by the inertia of a moving body as it tries to keep the object moving in the same direction, at the same speed.

Aviation Maintenance Technician Handbook — Powerplant, p. G-18

An alloy of nickel, copper, and aluminum or silicon.

Aviation Maintenance Technician Handbook — Airframe, p. G-23

A single-shell type of aircraft structure in which all of the flight loads are carried in the outside skin of the structure.

Aviation Maintenance Technician Handbook — Airframe, p. G-23

Airplanes with a single set of wings.

Pilot's Handbook of Aeronautical Knowledge, p. G-20

(verb) The act of rotating a turbine engine using the starter, with the ignition system deactivated. An engine is motored to force air through it to purge fuel fumes.

Aviation Maintenance Technician Handbook — Powerplant, p. G-18

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

Pilot's Handbook of Aeronautical Knowledge, p. G-20

Designed primarily for highpressure (3,000 psi) hydraulic systems that may be subjected to severe vibration or fluctuating pressure. Using this type of fitting eliminates all tube flaring, yet provides a safe and strong, dependable tube connection. The fitting consists of three parts: a body, a sleeve, and a nut.

Aviation Maintenance Technician Handbook — General, p. G-7

See minimum safe altitude.

Pilot's Handbook of Aeronautical Knowledge, p. G-20

Material Safety Data Sheets. MSDS are required by the Federal Government to be available in workplaces to inform workers of the dangers that may exist from contact with certain materials.

Aviation Maintenance Technician Handbook — Airframe, p. G-23

Mean time between failures.

Aviation Maintenance Technician Handbook — Airframe, p. G-23

See military training route.

Pilot's Handbook of Aeronautical Knowledge, p. G-21

Small screen (CRT or LCD) in an aircraft that can be used to display information to the pilot in numerous configurable ways. Often an MFD will be used in concert with a primary flight display.

Pilot's Handbook of Aeronautical Knowledge, p. G-21

An electrical test instrument that consists of a single current-measuring meter and all of the needed components to allow the meter to be used to measure voltage, resistance, and current. Multimeters are available with either analog-or digital-type displays.

Aviation Maintenance Technician Handbook — Airframe, p. G-23

A combustor used in a gas turbine engine that consists of a series of individual burner cans, each made of an inner liner and an outer case. The individual cans are arranged around the periphery of a centrifugal compressor. Hot gases flow directly from the cans into the turbine.

Aviation Maintenance Technician Handbook — Powerplant, p. G-18

Aircraft brakes in which one set of discs is keyed to the axle and remains stationary. Between each stationary disc there is a rotating disc that is keyed to the inside of the wheel. When the brakes are applied, the stationary discs are forced together, clamping the rotating discs between them. The friction between the discs slows the aircraft.

Aviation Maintenance Technician Handbook — Airframe, p. G-23

The process of repeated addition.

Aviation Maintenance Technician Handbook — General, p. G-7

See minimum vectoring altitude.

Pilot's Handbook of Aeronautical Knowledge, p. G-21