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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unfeather (propeller operation). To change the blade pitch of a propeller from the feathered high pitch, which prevents air loads windmilling it, to a lower pitch. When a propeller is unfeathered in flight, aerodynamic forces produced by air flowing over the blades cause the propeller to turn the engine. UNICOM (radio communications). A privately owned radio station located on an airport. Pilots of aircraft operating from the airport can talk with the operator of the UNICOM station to order service or to have the operator ready to service their aircraft when they land. UNICOM can be used to give advisory information about the airport, but it cannot be used to control traffic around the airport. unidirectional current (electrical current). Another name for direct current. Unidirectional current flows in one direction only. It does not reverse its direction as alternating current does. It is always either positive or negative, with respect to a reference value. unidirectional fabric. Fabric in which all of the threads run in the same direction. These threads are often bound with a few fibers which cross them at right angles, just enough to hold the yarns together and prevent their bunching. uniform acceleration. The speeding up of an object in which the velocity increases at a uniform rate. It changes the same amount each second it moves. union (threaded pipe fitting). A three-piece threaded pipe fitting used to join two pipes or to connect a pipe to a component. A union allows the pipes to be connected without either of the pipes having to be turned. |
