Abstract: hree kinds of devices of drag reducing are presented:swept wing-tip,stage by stage swept wing and downbend wing-tip. The effcets of changing geometry parameters of the swept wing-tip on the drag reducing are also presented.Wind-tunnel experiment results indicate that a properly designed swept wing-tip results in an increment in indueed efficiency of 4%～7% nd that swept wing-tip can increase longitudinal static-stability.Water-tunnel experiment re- sults indicate that the reason for drag reducing of swept wing-tip is that when the angle of attack is not Zero,the strength tip vortex of the wing is weakened by the combined effect of the leading edge and trailing edge vortices of the swept wing-tip.

Key words: light aircraft, drag reduction, wind tunnel tests