Maintenance allocation chart -- chart in a -20 TM that assigns maintenance tasks to the lowest level
capable of doing them, based on experience, skills, tools, and time available.
Manifold -- component in which air or gases are collected for intake or expulsion.
Micron --one millionth of a meter.
Mil -- unit of length equal to 1/1000 inch. Unit of angular measurement equal to 1/6400 of the
circumference of a circle.
N1 system -- gas producer.
N2 system -- power turbine and shaft.
Nacelle -- enclosed housing for an aircraft engine, outside the fuselage.
Nozzle -- channel through which gas is conveyed to the rotor vanes of a turbine. Its purpose is to
convert pressure into velocity.
Orifice -- opening having a closed perimeter through which a fluid may discharge. It may be open to the
atmosphere, or it may be partially or completely submerged in the discharged fluid.
Oscillograph -- instrument that produces a record of variations in an electrical quantity.
Oscilloscope -- instrument that shows the presence and form of an electric current.
Outside air temperature -- commonly abbreviated as O. A. T, the temperature of the air outside the
engine.
Otto cycle -- a constant volume cycle, with four distinct operations performed intermittently.
Reciprocating engines operate on this cycle.
Overspeed governor, N2 -- gearbox mounted on engine inlet housing and driven from the power shaft.
Overspeed governor, fuel control -- part of the torquemeter system, an individual pumping unit which,
with the tachometer drive assembly, sets the torquemeter oil pressure.
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