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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national search and rescue plan (air traffic control). An interagency agreement which provides for the effective utilization of all available facilities in all types of search and rescue missions. natural aging (metal heat treatment). A step in the heat treatment of aluminum alloys in which the metal is removed from the quench bath and allowed to gain its full strength at room temperature. In artificial aging, the metal is held at an elevated temperature for it to gain its full strength in a shorter period of time. naturally aspirated engine (reciprocating engine). A reciprocating engine that uses atmospheric pressure to force the charge of fuel-air mixture into the cylinders. A naturally aspirated engine differs from a supercharged engine that uses a mechanical air compressor to increase the pressure of the air and force the fuel-air mixture into the cylinders. natural numbers. Positive integers (numbers, such as 1, 2, 3, 4, 5, etc.). Natural numbers are also called counting numbers. Zero, negative numbers, and fractions are not natural numbers. nautical mile. A measure of distance used in air and sea navigation. One nautical mile is equal to the length of one minute of latitude along the earth’s equator. One nautical mile is nominally considered to be 6,080 feet, or 1,853.2 meters. However, when the United States accepted the metric system in 1959, the nautical mile was officially set as 6,076.115 feet. nautical twilight. The period of time before sunrise and after sunset when the sun is not more the 12° below the horizon. navaids (navigational aids). Any visual or electronic device, airborne or on the surface, which provides point-to-point guidance information or position data to aircraft in flight. Electronic navaids have been installed around airports and along airways to help pilots navigate without reference to visual features of the terrain. Very-high-frequency OmniRange navigation equipment (VOR), Instrument Landing Systems (ILS), and Distance Measuring Equipment (DME) are examples of navaids. navaid classes. Classification of navigational aids according to their operational uses. The three classes are: T – Terminal, L – Low altitude, and H – High altitude. navigable airspace. 14 CFR Part 1: “Airspace at and above the minimum flight altitudes prescribed by or under this chapter, including airspace needed for safe takeoff and landing.” navigation lights (aircraft). Colored lights on an aircraft used at night to show the direction the aircraft is moving. A red light is installed on the left wing tip, a green light is on the right wing tip, and a white light is installed on the tail of the aircraft. N-channel FET (semiconductor device). A field-effect transistor in which the resistive area between the source and drain is made of N-type semiconductor material. NDB (nondirectional beacons). A L/MF or UHF radio beacon transmitting nondirectional signals. The pilot of an aircraft equipped with direction finding equipment can determine his bearing to or from the NDB and home on or track to or from the station. |
