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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X-ray inspection is used to examine the inside of a structure for corrosion or damage that deforms the structure. X-rays. Rays of electromagnetic energy having a wavelength of approximately one angstrom. X-rays are produced by accelerating electrons to a high velocity and then stopping them instantly by collision with a solid object. X-rays are able to penetrate many types of solid objects and are used to produce a photographic record of the inside of an aircraft structure. xylene. A flammable, oily, aromatic, hydrocarbon fluid. Xylene is mixed with other hydrocarbon fluids and used as a solvent and as an additive to improve the combustion characteristics of reciprocating engine fuels. Y yagi antenna (radio antenna). A highly directional antenna used for high-frequency (HF) radio communications. A yagi antenna has a single dipole connected to the transmission line (this is the driven dipole) and several unconnected dipoles parallel to the driven dipole. These unconnected dipoles act as reflectors and directors for the radio-frequency energy transmitted from the antenna. yard (unit of measure). A unit of length in the English system of measurement. One yard is equal to 36 inches, three feet, or 0.9144 meter. yardstick. A wooden measuring stick with the length of three feet, or one yard. A yardstick is marked at every inch along its length. yaw (aircraft flight condition). A flight condition of an aircraft in which the aircraft rotates about its vertical axis. Yawing is not the same as turning, because an aircraft can be yawed and continue in straight flight with the wind striking it from the side. When an airplane is turned, it follows a curved flight path, with the wind always flowing parallel to its longitudinal axis. yaw damper (airplane control). A part of an aircraft automatic flight control system used to keep the aircraft from unwanted yawing. Yaw dampers are generally needed for swept-wing airplanes because of the tendency of this type of airplane to Dutch roll. See Dutch roll. Y-axis. The lateral, or pitch, axis of an aircraft. The vertical, or yaw, axis is the Z-axis, and the longitudinal, or roll, axis is the X-axis. See lateral axis. Y-connected circuit (electrical circuit). A three-phase alternating current circuit in which one end of each of the three windings of a three-phase generator or transformer is connected to form a common point. In a Y-connected circuit, two windings are in series with each other, and the current flowing in each of the two windings is 120 electrical degrees out of phase with the current flowing in the other windings. The voltage across the ends of the two windings is 1.73 times the voltage across either of the windings and the common point. A Y-connected circuit is sometimes called a wye-connected circuit or a star-connected circuit. yellow arc (aircraft instrument marking). A type of range marking for aircraft instruments that identifies a caution area. A yellow arc on the dial of an airspeed indicator identifies a range of airspeeds that can be safely flown in calm air, but the aircraft must not be flown at these speeds in rough air. There must be no abrupt maneuvers made while flying in this speed range. |
