Analyzing the Dynamic Behavior of a High Aspect Ratio Wing Incorporating a Folding Wingtip

High aspect ratio wings have been the focus of recent aircraft designs for improving fuel efficiency through induced drag reduction. The lengthened wingspan derived from these designs have led to the introduction of folding wingtips in order to meet airport gate width requirements. Previous numerical and experimental studies have demonstrated that folding wingtips can also provide a gust load alleviation benefit, when the folding wingtips are able to rotate freely about the hinge during the gust encounter. This work examines the dynamic characteristics and behavior of the folding wingtip, and the overall wing in such a configuration. A series of wind tunnel tests was conducted using a specially designed high aspect ratio wing model to establish its modal characteristics through application of a stepped-sine frequency sweep, performed using a gust generator as well as a secondary aerodynamic surface incorporated into the wingtip as the excitation source. In addition, a pseudo-random gust sequence was used as a faster test method through broadband excitation, which yielded results that were in excellent agreement with the stepped-sine methods.