时间：2011-03-11 23:18来源：蓝天飞行翻译 作者：航空 点击：次
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summation principle (meteorology). The principle which states that the sky cover assigned to a layer is equal to the summation of the cover of the lowest layer, plus the additional coverage at all successively higher layers, up to and including the layer in question. No layer can be assigned a sky cover less than a lower layer, and no sky cover can be greater than 1.0 (10/10). summerwood. The less porous, usually harder portion of an annual ring that forms in a tree during the latter part of the growing season, the summer of the year. sump (aircraft engine component). A low point in an aircraft engine in which lubricating oil collects and is stored or transferred to an external oil tank. A removable sump attached to the bottom of the crankcase of a reciprocating engine is often called an oil pan. sump (fuel tank component). A low point in an aircraft fuel tank in which water and other contaminants collect and are held until they can be drained out. sump jar (aircraft battery installation component). A small jar located in the vent line of an aircraft battery box. The sump jar used in a lead-acid battery installation contains a sponge saturated with a solution of bicarbonate of soda and water. Acid fumes from the battery pass through the sump jar where they are neutralized to prevent their causing corrosion in the aircraft structure. The sump jar in a nickel-cadmium battery installation contains a boric acid solution to neutralize the alkaline fumes from this battery. superadiabatic lapse rate (meteorology). A lapse rate greater than the dry-adiabatic lapse rate, greater than 3°F per thousand feet. supercharged engine. A reciprocating engine that uses an air compressor to increase the pressure of the air before it enters the engine cylinders. supercharger (reciprocating engine component). An air pump used to increase the pressure of the air taken into the cylinders of a reciprocating engine. The amount of power a reciprocating engine can develop is determined by the mass, or weight, of the fuel-air mixture taken into the cylinders. By compressing the air before it enters the cylinders, a greater mass of air can be used, and more power can be developed by the engine. Superchargers can be gear-driven from the engine, or they can be driven by a turbine spun by exhaust gases. Superchargers driven by exhaust gases are called turbochargers or turbosuperchargers. superconductivity. A condition of certain chemical elements (niobium, tantalum, vanadium, tin, and others) when they are held at a temperature near absolute zero. At this low temperature, these metals lose almost all their electrical resistance and become strongly diamagnetic. They try to orient themselves across a magnetic field, rather than aligning with the field. supercooled water. Water in its liquid form at a temperature well below its natural freezing temperature. When supercooled water is disturbed, it immediately freezes. supercritical airfoil (aerodynamics). An airfoil section that allows an airplane to cruise efficiently at a speed very near Mach one (the speed of sound). The center portion of the airfoil is nearly flat, and there is a distinct downward curve, or cusp, near the trailing edge. The lower side of the forward part of the airfoil is more curved than the upper side. |
