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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profile drag (aerodynamic drag). Aerodynamic drag caused by friction between the air and the surfaces of an aircraft over which it is flowing. Profile drag is one of the forms of parasite drag. profile tip (turbine engine compressor blade tip). An axial-flow compressor blade whose tip thickness is reduced to give it a higher resonant frequency so it will not be subject to the vibrations that would affect a blade with a squared tip. The profile tip also provides a more aerodynamically efficient shape for the high-velocity air that is moved by the blade. Profile tips often touch the housing and make a squealing noise as the engine is shut down. For this reason, profile tips are sometimes called squealer tips. profilometer. A precision measuring instrument used to measure the depth of the hone marks in the surface of an aircraft engine cylinder wall. prognostic chart (meteorology). A chart showing expected or forecast weather conditions. Prognostic charts are generally referred to as prog charts. program (computer operation). A series of step-by-step instructions that tells a computer exactly how it is to receive data, store it, process it, and deliver it to the user. program flowchart (computer operation). A chart of the steps taken in the execution of a program by a computer. Symbols are used in the flowchart to show the beginning and the end of the program, data input and output points, and decision points. programmable calculator. An electronic calculator controlled by a program stored in its memory. A programmable calculator is a versatile instrument that allows the use of different programs to solve many different types of problems. programmable read-only memory. See PROM. progressive inspection (aircraft maintenance inspection). An inspection that may be used in place of an annual or 100-hour inspection. It has the same scope as an annual inspection, but it may be performed in increments so the aircraft does not have to be out of service for a lengthy period of time. progressive taxi (air traffic control). Precise taxi instructions given to a pilot unfamiliar with the airport or issued in stages as the aircraft proceeds along the taxi route. PROM (programmable read-only memory). An integrated circuit memory device for a digital computer. Read-only memory is stored in PROM as a series of logic zeros and ones, by burning out certain diodes in it. Once the PROM is programmed, it cannot be changed. There is an erasable, programmable read-only memory (EPROM) that can be erased by exposing it to ultraviolet light. It can then be reprogrammed by using a special programmer. prohibited area. 14 CFR Part 1: “Designated airspace within which flight of aircraft is prohibited.” promethium. A radioactive, rare-earth chemical element used as a source of beta rays. Promethium’s symbol is Pm, its atomic number is 61, and the mass number of its most stable isotope is 145. prony brake. An instrument used to measure the amount of horsepower an engine or motor is delivering to its output shaft. The engine is operated at a specified RPM, and a brake is applied to its output shaft. The amount of torque applied to the brake is measured, and this, with the RPM, is converted into brake horsepower. |
