the Aviation Dictionary

moving-coil meter . Mylar ca~acitor
moving-coil meter - A d'Arsonva1 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
anival 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 hndamental 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 fkom 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.
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