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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Dutch roll (flight condition). An undesirable, low-amplitude oscillation about both the yaw and roll axes that affects many swept wing airplanes. Dutch roll is minimized by the use of a yaw damper. duty cycle. A schedule that allows a device to operate for a given period of time, with a cooling down period required before the device can be operated again. D-value (meteorology). The difference, shown on a constant-pressure chart, between the actual height and the standard atmospheric height of a constant-pressure surface. D-value is the algebraic difference between true altitude and pressure altitude. DVFR (defense visual flight rules). Rules applicable to flights within an air defense identification zone (ADIZ) conducted under visual flight rules as defined in 14 CFR Part 91. DVFR flight plan (air traffic control). A flight plan filed for a VFR aircraft which intends to operate in airspace within which the ready identification, location, and control of aircraft are required in the interest of national security. dwell chamber (turbine engine lubrication system component). A chamber in a turbine engine oil tank into which the scavenged oil is returned. Entrapped air can separate from the oil in this chamber before it is picked up by the pressure pump. dwell time (penetrant inspection). The length of time a penetrant is allowed to remain on the surface of a part being inspected. The dwell time is determined by the temperature of the part and the size of the suspected defect. dye. A colored substance used to add a more or less permanent color to another object. Dyes are added to aviation gasoline to give each grade an identifying color. Dyes are also used to add an attractive color to the oxide film that forms when aluminum alloys are anodized. dye penetrant inspection. A method of nondestructive inspection used to detect surface defects in metal or plastic parts. The part to be inspected is soaked in a penetrating liquid for a specified period of time, and then all the penetrant is washed from its surface. The surface is then covered with a developing powder that pulls the penetrant from any defects that extend to the surface of the part. The penetrant plainly shows up on the powder-covered surface, outlining the defect. dynafocal engine mount (reciprocating engine mount). A special type of mount for an aircraft engine in which straight lines that pass through the engine mount bolts intersect at the center of gravity of the engine and propeller assembly. Dynafocal engine mounts absorb much of the torsional vibration caused by the engine. dynamic (air traffic control). Continuous review, evaluation, and change to meet demands. dynamic balance. The balance of a rotating object, such as a wheel or propeller spinner. The condition of dynamic balance is checked with the object rotating. If an unbalanced condition causes vibration, the balancing equipment shows the amount of weight and the location of the weight needed to stop the vibration. Wheels and tires, as well as propellers, are dynamically balanced. |
