poundal. A measure of force in the English system. One poundal is the amount of force needed to cause a mass of one pound to accelerate at the rate of one foot per second each second it is acted upon.
pour point (petroleum product specification). The lowest temperature at which a material will pour without assistance.
powdered-iron core (electrical component). A highly permeable core used in some electrical coils. The core is made of fine particles of powdered iron, mixed with a suitable binder, and molded into the needed shape. Powdered-iron cores have a high permeability and low eddy current losses.
power (electrical). The product of the applied voltage and the current in a DC circuit. In an AC circuit, power is the product of the applied voltage and only that portion of the current in phase with the voltage. The basic unit of electrical power is the watt, the amount of power used when one ampere of current is forced through an electrical load under a pressure of one volt. One mechanical horsepower is equal to 746 watts of electrical power.
power (mechanical). The time rate of doing work. Power is found by dividing the amount of work done, measured in foot-pounds, by the time in seconds or minutes used to do the work.
Power can be expressed in terms of foot-pounds of work per minute, horsepower, or watts. One horsepower is equal to 33,000 foot-pounds of work per minute, 550 foot-pounds of work per second, or 746 watts. One metric horsepower is equal to 75 meter-kilograms of work per second or 0.9863 English horsepower.
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 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.
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