Wind Tunnel Testing of Folding Wing-Tip Devices for Gust Loads Alleviation

An increasing number of recent aircraft designs have begun considering the use of higher aspect ratio wings for reducing induced drag to improve fuel consumption. The increased wing span has led to the introduction of folding wing-tips as a solution for meeting airport gate requirements. Recent numerical studies have suggested such folding wing-tip solutions may be incorporated with spring devices to provide gust loads alleviation in flight as well. A series of low-speed wind tunnel tests was conducted in order to demonstrate such a concept using a prototype model. It was found that gust loads alleviation could be achieved using a folding wing-tip with a non-zero relative angle of the folding hinge axis to the stream-wise direction. The best loads alleviation performance varied with hinge angle setting and hinge stiffness, as well as lifting condition.