Aeroelastic Roll Control for High Aspect Ratio Wings

The undersigned hereby certify that they have read and recommend to the Faculty of Aerospace Engineering for acceptance a thesis entitled " Aeroelastic Roll Control for High Aspect Ratio Wings " Summary Modern aircraft tend to be light and slender. The high aspect ratio reduces the induced drag, increase fuel efficiency, and provide enough lift at low speeds. Therefore such wing types are used for long endurance unmanned aerial vehicles (UAV). A drawback of these wings is that they are more vulnerable for aeroelastic phenomena like divergence, aileron reversal, and flutter. To increase the dynamic pressure, at which one of these phenomena occurs, the stiffness of the wing needs to be increased leading to an increase of the wing weight. Instead of increasing the wing weight, the flexibility of the wing can be used to change the shape of the wing to optimize flight performance or to control the rolling motion of the aircraft. This research area of Active Aeroelastic Wings has grown in the recent years. With this concept, very little control surface motion is used to employ the energy of the airstream to achieve the desirable wing twist. In this thesis work, an Active Aeroelastic Wing is designed, built and tested in a low-speed wind tunnel. After testing, the possibility to predict the performance accurately with a state-of-the-art modeling tool is verified. First, a qualitative background overview is given about the three most important aeroelastic phenomena. These phenomena are torsional divergence, control reversal, and classical flutter and are described to understand the effects of the different wing parameters on the deformations. Secondly, an overview is given of the techniques that have been used to change the shape of the wing. From these concepts, the sweepable spar method has been chosen. This method uses the ability to change the position of the elastic axis, so that the twist deformations can be increased or decreased. Based on this method, a test article has been built that has similar planform shape as the Global Hawk. Instead of ailerons for roll control, the test article is equipped with an aeroelastic outer wing segment that can change its elastic axis. With this aeroelastic outer wing part, the wing is able to provide a rolling moment. Afterwards, its performance has been tested in the Open Jet Facility of the TU Delft. The results of the bench tests showed that the moveable spar is able …