This paper presents a method to determine utter and divergence instability limits for a 2D airfoil section tted with active control. The control system consists of a ap-like deformable trailing edge actuator, maneuvered by algorithms based on measurements of either heave displacement, local angle of attack, or pressure dierence over the airfoil. The purpose of the trailing edge actuator is to reduce uctuations in the aerodynamic forcing and a signicant potential for active fatigue load

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... on has been reported in recent studies. Besides the control, the full model of the ap equipped airfoil also comprises a structural and an aerodynamic part. The in-plane motion and deformation of the 2D structure are described by three degrees of freedom: heave translation, pitch rotation and ap deection. A potential ow model provides the aerodynamic forces and their distribution, the unsteady aerodynamics are described using an indicial function approximation. Stability of the full aeroservoelastic system is determined through eigenvalue analysis. Validation is carried out against a reimplementation of the recursive method by Theodorsen and Garrick for'exure-torsion-aileron' utter. The implemented stability tool is then applied to an airfoil section representative of a wind turbine blade with active ap control. It is thereby observed that the airfoil stability limits are signicantly modied by the presence of the ap, and they depend on several parameters: ap structural characteristics, type of control, control gain factors and time lag. 1