时间：2011-03-11 23:13来源：蓝天飞行翻译 作者：admin 点击：次
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Dry-type pumps require no lubrication, but the vanes are extremely susceptible to damage from solid airborne particles. These pumps must therefore be operated with filters in their inlet. dual-beam oscilloscope. A cathode-ray oscilloscope with two electron beams which produce two traces on the screen at the same time. Dual-beam oscilloscopes may be used to observe the signals on the input and the output of a portion of a circuit at the same time. dual controls (aircraft flight controls). Two sets of fully functioning flight controls in an aircraft. Dual controls allow the aircraft to be flown from either the left or right seat. All aircraft whose certification requires a pilot and copilot must be equipped with fully functioning dual controls. dual ignition. An ignition system of an aircraft reciprocating engine that has two of every critical unit, including two spark plugs in each cylinder. Dual ignition provides safety in the event of one system malfunctioning, but more important, igniting the fuel-air mixture inside the cylinder at two locations provides more efficient expansion of the air in the cylinder. dual indicator (aircraft instrument). An aircraft instrument in which two instrument mechanisms move pointers across a single dial. Many engine instruments installed in multiengine aircraft are dual indicators. For example, the oil pressure for both engines may be indicated on a single instrument. There are two separate indicator mechanisms and two pointers, but only one instrument case and one dial. dual magneto. A magneto having a single rotating magnet and cam, but two sets of breaker points, two coils, two condensers, and two distributors. A dual magneto is considered to be the equivalent of two separate ignition systems for an aircraft engine. dual rotor system (helicopter rotor system). A system of helicopter rotors in which there are two main rotors driven by coaxial drive shafts. The rotors turn in opposite directions so their torques counteract each other. dual-spool gas-turbine engine. An axial-flow turbine engine that has two independent compressors, each driven by its own stage or stages of turbines. The high-pressure, or N2, compressor is speed governed by the fuel control, but the low-pressure, or N1, compressor is not governed but seeks its own best speed as the ambient air density changes. duckbill pliers (mechanic’s hand tools). A special type of pliers used to twist safety wire. Duckbill pliers have long handles and wide, flat jaws with serrations to grip the wire, but they do not have jaws for cutting the wire. duct (air conditioning and heating component). A thin-wall tube installed in an aircraft to carry heated or cooled air for distribution at the proper locations. ducted-fan engine (aircraft engine). A form of aircraft engine in which a propeller or fan is enclosed in a specially shaped shroud, or duct. A ducted-fan engine has a high degree of propulsive efficiency. duct heater. A thrust augmentation system similar to an afterburner in which fuel is added to the fan discharge air and burned. |
