A fluid turbine has an annular-airfoil duct and passive, leading-edge flaps on the airfoil that enhance yaw stability and reduce extreme loads in excessive fluid-stream velocities when the turbine is in shutdown mode, or when it is parked or otherwise not producing power. Flaps retract and deploy passively to reduce loads by eliminating the lift over the airfoil, providing manageable loads in high-velocity flow at Up-0. The flaps are intended for use in extreme and unlikely events. Appropriate design and material selection mitigates the detrimental effects of dormancy.