power amplifier (electronic circuit). An electronic amplifier designed to produce a gain in power (the
product of current and voltage), rather than just voltage.
power assurance check (gas turbine engine maintenance check). A test run made of a gas turbine engine
to determine the way its performance compares with its performance when it was new or freshly
overhauled.
power brake control valve (aircraft brake system component). The valve operated by the pilot of a
large aircraft to meter hydraulic system pressure into the brakes to apply them. The power brake control
valve meters pressure into the brake cylinders proportional to the amount of force the pilot exerts on the
brake pedals.
power brakes. Aircraft brakes that use the main hydraulic system to supply fluid for the brake actuation.
Aircraft that require a large amount of fluid for their brake actuation normally use power brakes, and the
volume of fluid sent to the brakes is increased by the use of deboosters. See debooster.
power control system (aircraft flight control system). A type of control system in which normal
operation of the flight controls causes hydraulic or pneumatic actuators to assist in moving the control
surfaces. This reduces the force needed by the pilot. An irreversible power control system is a type of
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 452
system that does not allow forces on the flight control surfaces to be fed back to the cockpit control.
power control valve (hydraulic system component). A hand-operated hydraulic pump unloading valve.
When the valve is open, fluid flows from the pump to the reservoir with little opposition. To actuate a unit,
the selector valve is turned to select the desired actuation and the power control valve is manually closed.
Pressurized fluid flows to the unit, and when actuation is completed, the power control valve automatically
opens.
power density (radar meteorology). The amount of radiated energy per unit cross-sectional area in a radar
beam.
power-enrichment system (fuel metering system). A subsystem in a carburetor or fuel injection system
used on a reciprocating engine. This system enriches the fuel-air mixture when the engine is operating at
full power.
The mixture ratio used for cruise power is adjusted to give the most economical operation, but
when the engine develops full power, enough heat is released to cause damage. The power enrichment
system meters additional fuel when the throttle is wide open. This fuel absorbs the excess heat. A
power-enrichment system is also called an economizer system.
power factor (electrical value). The ratio of the actual power to the apparent power in an alternating
current circuit. Actual power, measured by a wattmeter, is the product of the circuit voltage and only that
portion of the current in phase with the voltage. Apparent power is the product of the circuit voltage and the
total circuit current.
Power factor is also the ratio of the circuit resistance to the circuit impedance, and is the cosine of
the phase angle.
power frequencies (electrical power). The frequency of alternating current used to provide electrical
power. In the United States, 60 hertz is the most commonly used power frequency. In other parts of the
world, 50-hertz AC is used. Aircraft AC electrical systems use 400 hertz as the power frequency.
power lever (turbine engine control). The lever used to actuate the fuel control unit on an aircraft turbine
engine. The power lever programs the unit to supply the amount of fuel needed for the operation called for
by the pilot. The fuel control delivers this fuel only when all of the conditions in the engine are such that
allow it to take the fuel without stalling or flaming out.
power loading (aircraft performance). The ratio found by dividing the maximum weight of the aircraft
by the brake horsepower produced by all the engines.
power of a number (mathematics). The number of times a number is multiplied by itself. The power is
indicated by an exponent, a small superscript number such as the 3 in 43. For example, 43 = 64. This is the
same as 4 • 4 • 4 = 64.
power overlap (reciprocating engine parameter). The number of degrees of crankshaft rotation during
which more than one cylinder is on its power stroke.
powerplant (aircraft component). The complete installation of an aircraft engine, propeller, and all
accessories needed for its proper functioning.
powerplant rating (FAA rating). The rating associated with an FAA-issued aircraft mechanic license that
allows the holder to inspect, repair, and maintain the engine and propeller of an FAA-certificated aircraft.
power recovery turbine (reciprocating engines). A small turbine installed in the exhaust system of a
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