Active Hinged Wingtip Control for Reducing Wing Root Bending Moment

The development of lighter and more efficient transport aircraft has increased the focus on reducing gust loads. One recent design innovation is the use of hinged wingtip devices to increase the aspect ratio, thereby enhancing aircraft performance. Experimental tests have demonstrated that passive hinged wingtips can provide additional gust load alleviation. This study introduces a brushed DC motor in the hinge to control wingtip rotation, improving gust load reduction through a proportional-derivative control. A lightweight wingtip was designed to be either free-hinged or actively controlled by the motor, with the motor configuration also allowing for a fixed wingtip option. Wind tunnel experiments were conducted to test responses to 1-cosine and harmonic gusts for all wingtip configurations to measure the root bending moment caused by gusts. Additionally, the effects of nonzero angles of attack at the root, simulating takeoff conditions, and varying starting fold angles of the wingtip were examined to determine their impact on root loads under gust conditions. The results showed that an active wingtip significantly reduces both positive and negative peaks in the root bending moment and identified some limitations of passive wingtips, such as flapping at higher gust frequencies.