Aeroelastically adaptive propeller using blades’ root flexibility

Abstract

Abstract Usually a fixed pitch propeller is designed to be optimal at cruise speeds. Thus the efficiency is quite low at takeoff or low speeds, as well as during other flight regimes. The present paper shows that by introducing a flexible element into the blade root, the propeller efficiency can be improved over a wide range of velocities. The flexible element reacts to root flap or torsion moments by changing the blade pitch at the root. The root flexibility and the pitch angles at the root at zero loads are chosen such that efficiency will increase during problematic regimes without decreasing the propeller thrust. In the case of straight blades the torsional moment at the root is too small to be used. In the case of swept blades this moment component is significantly increased and can contribute to the design of an optimal aeroelastically adaptive propeller.