Experimental Study of the Impact of Folding Wingtip Devices on Aircraft Flight Mechanics and Handling Qualities

Recent advances in the semi-aeroelastic hinge (SAH) concept utilizes the folding wingtip as a passive load alleviation device, which significantly reduces the aerodynamic loads during manoeuvre and gust, leading to an improved structure efficiency and aircraft performance. This paper experimentally investigates the effect of implementing such device on the flight mechanics and flight handling quality. Wind tunnel tests are conducted with an aircraft model incorporating folding wingtips, where the aerodynamic derivatives of the aircraft are measured for various hinge configurations. A 5 degree of freedom (DoF) rig is implemented in the test which allows the model to heave, pitch, roll, yaw and sway to replicate flying conditions. The pitch motion is excited by applying the elevator input, where the frequency response function (FRF), short-period damping and frequency are determined. Furthermore, the gust response is measured for the model trimmed under a constant wind speed, in which a significant reduction in the gust loads is achieved with the folding wingtip device.