Wind Tunnel Testing of Gust Load Alleviation Performance of Flexible wing with Semi-Aeroelastic Hinge

High aspect ratio wings are particularly of interest to future aircraft design due to their superior aerodynamic performance. This paper describes an experimental campaign, as part of the U-HAWRAWD project, which was undertaken to investigate the gust load alleviation capability of the semi-aeroelastic hinge (SAH), i.e. a semi-passive device to keep the wingtip fixed in the cruise condition and free-floating during maneuver and gust encounters to mitigate the wing loads. A 2.17m long flexible wing incorporating a wingtip of 25% of the wingspan was installed in a half-aircraft model that is free to heave and pitch. The load alleviation performance of the SAHto discrete 1-cosine gusts with various lengths was assessed. It was shown that the bending moment measured from the free hinge configuration was significantly lower compared to that of the fixed hinge, consistent with previous numerical studies. Furthermore, a test was conducted to investigate the effect of transient response due to the in-flight wingtip release. The dynamic response due to the wingtip release exacerbated the gust response, potentially leading to greater bending loads. However, both experimental and numerical results suggest the loads induced by transient responses can be mitigated by accurately adjusting the hinge release time during gust encounters. For example, enhanced load alleviation can be achieved by allowing the wingtip’s transient response to counteract the gust response.