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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upholstery. The fabric, padding, and other components used to make a soft covering for a seat. Upholstery makes the seat comfortable to sit in and attractive to look at. upper deck pressure (fuel metering system pressure). The pressure that exists between the turbocharger compressor and the throttle plate of a fuel injection system installed on a reciprocating engine. Upper deck pressure, also called turbocharger discharge pressure, differs from manifold pressure by the pressure drop across the throttle valve. upper front (meteorology). A front aloft that does not extend to the earth’s surface. upset head (rivet head). The head of a rivet formed when the rivet is installed. The upset head is also called the shop head, to distinguish it from the manufactured head on the rivet before it is driven. upslope fog (meteorology). Fog formed when air flows upward over rising terrain and is cooled adiabatically to a temperature at or below its initial dew point. upwind. The direction from which the wind is blowing. uranium. A heavy, silvery-white, metallic chemical element in the actinide group. Uranium’s symbol is U, and its atomic number is 92. An isotope of uranium, U-235, is used as one of the basic atomic fuels. When U-235 is bombarded with neutrons, it changes into smaller atoms, and in making this change, it releases neutrons and produces an enormous amount of heat. useful load (aircraft operation). The difference between the maximum allowable weight of the aircraft and its empty weight. The useful load of an aircraft includes the weight of the fuel and oil, the crew, the passengers, all of their baggage, and any cargo carried. U.S. gallon. A measure of quantity equal to 231 cubic inches, or 0.133 cubic foot. utility category aircraft. A classification of aircraft approved for limited acrobatics. The maneuvers approved include spins, lazy eights, chandelles, and steep turns in which the bank angle exceeds sixty degrees. utility finish (type of aircraft finish). The finish of an aircraft that gives the necessary tautness and fill to the fabric and the necessary protection to the metal, but does not have the glossy appearance of a show-type finish. U-tube manometer. A pressure measuring instrument made of a glass tube bent into the shape of the letter U. A liquid such as water or mercury is poured into the tube until it is filled to a given level. Either a positive or a negative pressure applied to one end of the tube will cause the liquid to rise in one side of the tube and drop in the other side. The difference in the level of the liquid in the two sides of the tube is proportional to the difference in the pressure at the two ends of the tube. V vacuum. A space in which nothing exists, a completely empty space. For practical purposes, a vacuum is considered to be a negative pressure, or a pressure less than that of the surrounding atmosphere. |
