Aerodynamic Model Identification of an Aircraft with Feather-inspired Flow Control Devices

Passive suction-side flaps, inspired by a bird’s covert feathers, have been shown to increase the critical angle of attack for subscale aircraft in flight experiments. In this paper, a data-driven aerodynamic model for the coefficient of lift was derived to explore the effects of such bio-inspired flow control devices at high angles of attack. This model was derived from flight test data during a power-on stall maneuver that achieves high angles of attack. The model structure was derived iteratively using stepwise regression and the Bayesian Information Criterion to balance goodness of fit and statistical significance. Once identified, the vehicle’s lift coefficient derivatives were estimated from the flight data. By comparing the estimated aerodynamic derivatives of an aircraft with the flow control devices to that of a baseline vehicle without them, it is evident that the suction side covert flaps increase lift at a given angle of attack. Additionally, it is observed that the covert flaps enhance pitch damping, which contributes to a stabilizing effect that mitigates the frequency and severity of stall. This initial study identifies a data-driven aerodynamic model for maneuvering in the stall regime, estimates parameters for that model, and compares derived models to provide evidence that bio-inspired covert flaps are an effective flow control device to improve aircraft performance near stall conditions.