词条 | gliding |
释义 | gliding sport also called soaring flight in an unpowered heavier-than-air craft. Any engineless aircraft (airplane), from the simplest hang glider to a space shuttle on its return flight to the Earth, is a glider. The glider is powered by gravity, which means that it is always sinking through the air. However, when an efficient glider is flown through air that is rising faster than the aircraft's rate of sink, the glider will climb. There are many types of glider, the most efficient of which is the sailplane (airplane). hang gliding and paragliding are specialized forms of gliding. ![]() ![]() ![]() The basic method of soaring, called thermaling, is to find and use rising currents of warm air, such as those above a sunlit field of ripened grain, to lift the glider. Thermals can rise very rapidly, which allows the sailplane, if deftly piloted, to attain substantial increases in altitude. Slope soaring occurs when moving air is forced up by a ridge. By following the ridge, the sailplane can glide for great distances. In wave soaring, the glider flies along vertical waves of wind that form on the lee side of mountain ranges (the side protected from fiercer winds). Riding such waves allows extreme altitude to be gained rapidly. To facilitate all such maneuvers as well as navigation, gliders can be equipped with familiar airplane instruments such as an altimeter, an airspeed indicator, a turn-and-bank indicator, a compass, and GPS (Global Positioning System) equipment. The most important instrument is the variometer, which shows when the glider is moving up or down even when that movement is too minute to be noticed by the pilot. National and international records for gliding include categories for straight distance, out-and-return (a course in which a pilot begins at a designated place, travels a distance, and then returns to the designated place), and triangle distance (a course that begins at a designated place after which there are two turning places before return), speed over triangular courses, gain of height, and absolute altitude. World championship competitions began in 1937 and since 1950 have been held every other year. The competition occupies about two weeks, and the tasks usually consist of elapsed-time races over out-and-return or triangular courses. The overall champion is determined by point total. Apart from competition, many pilots soar purely for recreation. |
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