时间：2011-03-11 23:18来源：蓝天飞行翻译 作者：航空 点击：次
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pulse generator (electronic test equipment). An electronic device that produces a series of pulses of electrical energy. These pulses have an accurately controlled pulse width, pulse spacing, pulse amplitude, and pulse repetition rate. pulse-jet engine. A type of air-breathing reaction engine that was used during World War II to power jet-propelled missiles. Fuel is sprayed into the combustion chamber and ignited. The air is thus heated, and as it expands, it closes the one-way shutter valve in the front of the engine and exits the engine through the nozzle at the rear. As soon as the pressure inside the combustion chamber decreases, air enters through the shutter valve and more fuel is ignited. The thrust is produced in a series of pulses. pulse length (radar technology). The dimension of a radar pulse. It may be expressed as the time duration or the length in linear units. The linear dimension of a pulse is equal to time duration multiplied by the speed of propagation, which is approximately the speed of light. pumice. A very fine abrasive powder used to polish metal surfaces. pump control valve (hydraulic system component). A control valve in a hydraulic system that allows the pilot to manually direct the output of the hydraulic pump back to the reservoir when no unit is being actuated. punch test (aircraft fabric). A test of the strength of aircraft fabric that can be performed on the aircraft with a minimum of damage to the fabric. A special tester with a sharp-pointed, spring-loaded punch is pressed into the fabric, and the amount of force needed for the punch to penetrate the fabric is measured. A punch test does not give a truly accurate indication of the strength of the fabric, but it is sufficiently accurate to tell whether or not the fabric strength is above a minimum value. Pureclad. A registered trade name for clad aluminum alloy sheets. purge (air conditioning system maintenance). The maintenance procedure in which all of the moisture and air is removed from a cooling system by flushing the system with a dry gaseous refrigerant. push-button switch (electrical switch). A type of electrical switch actuated by a push button. The button must be pushed each time the switch is to be opened or closed. pusher powerplant. A powerplant whose propeller is mounted at the rear of the airplane and pushes, rather than pulls, the airplane through the air. pusher propeller (aircraft propeller). A propeller installed on an aircraft engine whose propeller shaft faces the rear of the aircraft. Thrust produced by the propeller pushes the aircraft, rather than pulling it. push fit. A fit between pieces in a mechanical assembly that is close enough to require the parts to be pushed together. A push fit is looser than a press fit, but closer than a free fit. push-pull amplifier (electronic circuit). A type of electronic amplifier with two output circuits whose output voltages are equal but 180° out of phase with each other. A push-pull amplifier is also called a balanced amplifier. |
