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Unpowered aircraft are a group of aerial vehicles that can fly without onboard propulsion. They can be classified as Glider aircraft, balloons and kites. In this instance, 'flight' means a trajectory that is not merely a vertical descent such as a parachute. In the case of kites, the flight is obtained by tethering to a fixed or moving object, perhaps another kite.〔(System and method for wind-powered flight Dale C. Kramer )〕 In the case of balloons, the flight is free but there is little directional control. The remainder of this group are the heavier-than-air craft such as Glider (sailplane), hang gliders, and paragliders that have complete directional control and so can fly freely. ==History== * ''For history of gliders, see Glider aircraft * ''For history of glider/sailplanes, see Glider (sailplane) * ''For history of hang gliders, see History of hang gliding * ''For history of paragliders, see Paragliding * ''For history of balloons, see Balloon * ''For history of kites, see Kite * ''For history of airborne wind energy aircraft, see High altitude wind power The first manned aircraft were kites, balloons and gliders. Kites are recorded in ancient Chinese history as being used for lifting men. Unmanned hot air balloons are also recorded in Chinese history. However the first free flight (i.e., untethered) by manned craft was by balloon built by the brothers Joseph-Michel and Jacques-Etienne Montgolfier in Annonay, France in 1783. The first practical, controllable glider was designed and built by the British scientist and pioneer George Cayley who many recognise as the first aeronautical engineer. It flew in 1849. Thereafter gliders were used for aerodynamic research, until their sporting use was developed in the 1920s. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Unpowered aircraft」の詳細全文を読む スポンサード リンク
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