PD 680 -- cleaning solvent for exterior of engine and its attached components.
Pneumatic -- something moved or worked by air pressure.
Power-to-weight ratio -- relationship between power and weight. Turbine engines produce more power
for weight than reciprocating engines.
Power turbine (N2) -- turbine that is free and independent of the gas producer system. It develops
rotational shaft power.
Pressure oil system -- method of supplying oil under pressure to engine parts.
Pressure pumps -- devices to put oil into the system.
Pressurizing and drain dump valve -- device to prevent flow of fuel to the nozzle until enough pressure
is built up in the fuel control. One also drains the fuel manifold at engine shutdown and traps
fuel in the upper portion of the system to keep the fuel control primed for faster starts.
Primary air -- air that mixes with fuel in the combustion chamber, to form a combustible mixture. The
ratio is 15 parts of air to 1 part of fuel.
Radial inflow turbine -- type of turbine made by some manufacturers, not used in any Army aircraft
today, even though it is rugged and simple, relatively inexpensive, and easy to manufacture.
Similar in design and construction to the centrifugal-flow compressor.
Ram air pressure -- free stream air pressure, provided by the forward motion of the engine.
Rear of engine -- end of engine from which exhaust gas is expelled.
Reciprocating engine -- device which produces motion in which the power originates in pistons and
cylinders.
Reverse flow -- change in direction of airflow in the combustion chamber of a gas turbine engine.
Rotational direction -- direction of movement of the rotating part, determined by viewing the engine
from the rear.
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