航空術(shù)語詞典Dictionary of Aeronautical Terms 中

時(shí)間：2011-03-11 23:13來源：藍(lán)天飛行翻譯 作者：admin 點(diǎn)擊：次

flasher (electric lights). An automatic switch installed in a light system to turn the lights on and off in a definite sequence. Flashers may be operated by a thermal switch, or they may have a motor that drives a selector switch.
In a thermally operated switch, the current used in the lights passes through a strip of bimetallic material and heats it. When the strip gets hot, it warps and separates the contacts, opening the circuit. Current stops flowing, and the lights go out. When the strip cools, it snaps back to its original shape and closes the contacts, and the lights turn back on.
flashing off (finishing system). A step in the curing process of a finishing system. The finishing material is thinned with a solvent to get the proper viscosity for spraying. When the finish is sprayed on the surface, it is shiny because of the solvents. These solvents evaporate very soon and leave the surface of the finish dry to the touch, but it is not completely cured. The evaporation of the thinning solvents is called flashing off.
flashing the field (generator maintenance). A maintenance procedure for an aircraft generator that restores residual magnetism to the field frame. DC generators get their field excitation current from the armature, and the field frame must retain a small amount of permanent magnetism to furnish the magnetic field to begin producing current in the armature. As soon as current begins to flow in the armature, it excites the field.
If the field frame loses its residual magnetism, it must be restored before the generator can produce current. This residual magnetism is restored by flashing the field. A battery is momentarily connected to the field coil so current flows through it in its normal direction for a few seconds. This current magnetizes the field frame.
flash line (molded products). The raised line along the surface of a molded part caused by the molten material flowing into the space formed by the slightly rounded edges of the two halves of the mold.
flashover (reciprocating engine ignition system fault). An ignition system problem in which the high voltage in the magneto distributor jumps to the wrong terminal. Flashover causes the wrong spark plug to fire, and this reduces the engine power and produces vibration and excessive heat.
Flashover is often caused by moisture inside the distributor, but it also occurs when flying at high altitude where the air inside the distributor does not have enough density to act as an effective dielectric. Physically large distributors, low-tension ignition systems, and pressurized distributors have been used to prevent flashover.
flash plating (metal finishing). The deposit of an extremely thin coating of metal on a surface. A flash coating is only thick enough to give color to the surface.
flash point (petroleum specification). The temperature to which a material must be raised for it to ignite, but not continue to burn, when a flame is passed above it.
flash resistant. 14 CFR Part 1: “Not susceptible to burning violently when ignited.”

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