Modeling Micro Air Vehicle Aerodynamics in Unsteady High Angle-of-Attack Flight

Abstract

An approach to modeling longitudinal airplane aerodynamics during unsteady maneuvers was developed for a micro air vehicle at angles of attack well past stall under unsteady conditions, including dynamic stall as might be experienced in perching maneuvers. To gather unsteady micro air vehicle flight data, an offboard motion tracking system was used to capture free-flight trajectories of a micro air vehicle with a weight of 14.44 g (0.0594 oz) and a wingspan of 37.47 cm (14.75 in.), operating at a nominal Reynolds number of 25,000. The measured trajectories included nominal gliding flight as well as mild-to-aggressive stalls. For the most aggressive stall case, the maximum lift coefficient reached a value near 2.5. The new model derived from the test data relied on a so-called separation parameter that modeled the aerodynamic lag during rapid changes in the angle of attack, and it thereby captured the effects of dynamic stall seen in the lift, drag, and moment coefficient data. Results from the model were shown for flights that covered a range of conditions from quasi-steady low angle-of-attack flight to aggressive stalls with angles of attack approaching 90 deg.