时间：2011-03-11 23:11来源：蓝天飞行翻译 作者：admin 点击：次
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Climb or descent within the airspace may be made at the discretion of the pilot. However, once the pilot starts descent and verbally reports leaving an altitude in the block, he may not return to that altitude without additional ATC clearance. cruise (aircraft flight condition). A flight condition that allows an aircraft to operate smoothly and efficiently for a long period of time. cruise climb (air traffic control). A climb technique employed by aircraft usually at a constant power setting, resulting in an increase of altitude as the aircraft weight decreases. cruising altitude. An altitude or flight level maintained during en route level flight. cruising level (ICAO). A level maintained during a significant portion of a flight. crush gasket. A form of gasket made of thin copper, formed around a core of asbestos. When the component being sealed by this gasket is screwed tightly into its housing, the gasket is crushed so it conforms to the two surfaces and provides a leakproof seal. cryogenic gyroscope. A form of gyroscope which uses a spherical rotor made of niobium. The rotor is suspended in a magnetic field and is operated at a cryogenic (extremely low) temperature. At this temperature the niobium acts as a superconductor. cryogenic liquid. A liquid which boils at temperatures of less than about 110°K (–163°C) at normal atmospheric pressures. Liquid nitrogen and liquid oxygen are commonly used cryogenic liquids. cryogenics. The branch of science or engineering that deals with technical operations involving very low temperatures; temperatures near absolute zero. crystal (frequency control device). A piece of quartz or Rochelle salt which has piezoelectric characteristics. A piezoelectric crystal produces a voltage between two of its opposite surfaces, or faces, when it is bent or compressed. A crystal also distorts when a voltage is placed across two of its opposite faces. All physical objects have a natural resonant frequency at which they vibrate most easily. A piezoelectric crystal will, when it is placed in an electrical circuit and excited with a pulse of electrical energy, vibrate at its resonant frequency. As the crystal vibrates, it produces an AC voltage whose frequency is the same as the resonant frequency of the crystal. crystal-controlled oscillator. An electronic oscillator which produces alternating current from direct current. The frequency of the AC is determined by the resonant frequency of a piezoelectric crystal in the oscillator circuit. crystal diode. A form of electronic check valve. A crystal diode uses a semiconductor material which allows electrons to pass in one direction, but prevents their flowing in the opposite direction. A crystal diode is made of either silicon or germanium which has areas doped with impurities that make P-areas and N-areas. crystal earphones. Earphones in which alternating current distorts a piezoelectric crystal. The crystal is attached to a diaphragm in such a way that, as the crystal distorts, the diaphragm produces changes in air pressure (sound waves). The sound waves duplicate the changes in the alternating current. |
