This study investigates the wing deformation of the DelFly II in forward flight conditions. A measurement setup was developed that maintains adequate viewing axes of the flapping wings for all pitch angles. Recordings of a high-speed camera pair were processed using a point tracking algorithm, allowing 136 points per wing to be measured simultaneously with an estimated accuracy of 0.25 mm. The measurements of forward flight show little change in the typical clap-and-peel motion, suggesting similar effectiveness in all cases. It was found that an air-buffer remains at all times during this phase. The wing rotation and camber reduction during the upstroke suggests low loading during the upstroke in fast forward flight. In slow cases a torsional wave and recoil is found. A study of the isolated effects showed asymmetric deformations even in symmetric freestream conditions. Furthermore, it shows a dominant role of the flapping frequency on the clap-and-peel, while the freestream velocity reduces wing loading outside this phase.@en

This study investigates the wing deformation of a flapping-wing micro air vehicle (MAV) in climbing and forward flight conditions. A measurement setup was developed that maintains adequate viewing axes of the wings for all pitch angles. Recordings of a high-speed camera pair are processed using a point tracking algorithm, allowing 136 points per wing to be measured simultaneously with an estimated accuracy of 0.25mm. Results of the climbing flight study show that although inflow is symmetric, the wing deformations are slightly asymmetric. Furthermore, it was found that an air-buffer remains present between the wing surfaces at all times, especially with increased freestream velocity. Apart from a minor camber reduction, the clapand- peel motion remains mostly unchanged for changing velocities, while during the remaining cycle the incidence angle and camber ratio are reduced, together with the angle of attack. In forward flight the clap-and-peel motion is twisted around its contact area to align with the inflow direction, while the general deformation remains unchanged, suggesting similar effectiveness as in hover. Positive mean incidence angles are present for the entire cycle, especially for fast forward flight and stroke reversals. Furthermore, camber is positive during downstroke, while approaching zero for the upstroke in fast forward flight, which suggests low loading during the upstroke. @en