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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proportional control. A type of control in which the magnitude of the corrective action (the output) is directly proportional to the magnitude of the error (the input signal). An autopilot controls an airplane by proportional control. If a wing drops slightly (the error), the autopilot servo causes the proper aileron movement to smoothly return the aircraft to level flight. proposed departure time (air traffic control). The time a scheduled flight will depart the gate for scheduled operators, or the actual runway-off time for nonscheduled operators. For expected departure clearance time (EDCT) purposes, the air traffic control system command center (ATCSCC) adjusts the proposed departure time for scheduled operators to reflect the runway-off time. propulsive efficiency. A measure of the effectiveness with which an aircraft engine converts the fuel it burns into useful thrust, and is the ratio of the thrust horsepower produced by a propeller to the torque horsepower of the shaft turning the propeller. The more nearly the speed of the aircraft is to the speed of the exhaust jet or propeller wake, the less kinetic energy is lost in the jet or wake, and the higher the propulsive efficiency. propwash. A commonly used term for the air blown back from an airplane by the propeller. In the early days of aviation, one of the ways of hazing a fledgling mechanic was to send him across the airport “to get a bucket of propwash.” protactinium. A rare, radioactive chemical element in the actinide group. Protactinium’s symbol is Pa, and its atomic number is 91. The most common isotope of protactinium, Pa 231, has a half-life of more than 32,000 years. proton. The positively charged particles in the nucleus of an atom. prototype device. A working model of a device usually made by hand. The prototype of an aircraft is built to prove the design or design concept. After all of the design “bugs” are worked out of the prototype, production tooling is set up, and production models are built. The production models are quite similar to, but not exactly like the prototype. protractor. An instrument used to measure angles. protruding head rivet (aircraft structural component). An aircraft rivet whose head protrudes, or sticks up, above the surface of the metal it is used to join. The universal head rivet (MS20470) is the most commonly used protruding head rivet in modern aircraft construction. PRT (power recovery turbine). A turbine driven by the exhaust gases from several cylinders of a reciprocating engine. Energy extracted from the exhaust gases by the turbine is coupled, through a fluid clutch, to the engine crankshaft. |
