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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needle and ball indicator (aircraft flight instrument). An old name for a turn and slip indicator. See turn and slip indicator. needle bearings. A type of anti-friction bearing. Needle bearings are made of a series of relatively long, small-diameter rollers (the needles) made of hardened steel. The needles ride between two hardened and polished steel races. One race is pressed into the housing, and the other race is pressed onto the rotating shaft. Needle bearings are effective for radial loads only. needle valve. A fluid control valve that uses a long tapered needle to control the amount of fluid that can flow through an orifice. The needle valve can be moved into or out of the orifice. When the needle is completely in the orifice, the fluid flow is minimum, and when it is completely out of the orifice, the flow is limited by the size of the orifice. When the needle is neither fully in nor fully out, its position controls the effective size of the orifice and thus the amount of fluid allowed to flow. “Negative” (air traffic control). A term used by ATC to mean “no,” or “permission not granted,” or “that is not correct.” negative (electrical condition). A condition in which there are more electrons (negative charges) than there are protons (positive charges). A negative condition is indicated by a minus sign (–) in front of the value. For example, –6 volts is negative six volts. negative acceleration. A term meaning deceleration, or slowing down. Negative acceleration is a decrease in speed with time and is expressed in such terms as feet per second, per second or meters per second, per second. negative charge (electrical charge). An unbalanced electrical condition caused by there being more electrons than there are protons. “Negative contact” (air traffic control). A term used by pilots to inform ATC that the previously issued traffic is not in sight, or they are unable to contact ATC on a particular frequency. negative dihedral (airplane stability). The downslope of airplane wings, or the downward angle formed between the wings and the lateral axis of an airplane. Negative dihedral, also called cathedral, increases the maneuverability of the airplane while decreasing its lateral stability. negative feedback (electronic circuit condition). A condition in an electronic circuit in which a part of the output signal is fed back into the input 180° out of phase with the input signal. Negative feedback decreases circuit amplification and also circuit distortion. It makes the output signal a truer copy of the input signal. negative ion. An unbalanced atom having more electrons spinning around the nucleus than there are protons in the nucleus. negative logic (digital electronics). A type of logic used in some digital electronic circuits. In negative logic, the lower of two voltage levels represents the condition of one, or yes, while the higher voltage represents the condition of zero, or no. |
