The aerodynamics of an actively twisted wing

Aerodynamic performance of aircraft can be changed by moving separate surfaces which are mechanically connected to the main wing and moved with complex linkages. A possible alternative method of changing performance with less mechanical complexity is presented. Instead of separate control surfaces, the shape of complete aerodynamic structures can be changed with shape memory alloy (SMA) materials as part of the structure. In this work SMA wire is wrapped around a simple test wing. When activated by heating, the wire contracts which results in twisting the wing. The angle of attack along the wingspan changes which changes the aerodynamic forces on the wing. This could be used to optimize the flight condition. Results are presented from initial wind tunnel experiments which show the change in lift due to twisting. Aerodynamic models that account for the variable angle of attack along the span are also developed. The results from the experiments and aerodynamic model are compared.