A study was conducted to address the challenges associated with investigating a bistable composite flap for an airfoil. A full-scale rotor blade section with a span of 2.114 m and a chord of 0.68 m, fitted with a 1 m span flap was wind-tunnel tested up to a speed of 60 m/s with the flap moving between two stable states for various angles of attack. The blade was approximated as a NACA 24016 section with a 20% chord trailing-edge flap to simplify the analysis. The trailing-edge flap was designed to change between its stable geometries between hover and forward flight conditions for aerodynamic performance improvements. The flap was driven by an electromechanical actuator that was mounted inside the blade D-spar at the leading edge. All of the rotor blade structure remote from this bistable flap region was unmodified and assumed to be completely rigid during wind-tunnel testing.