Dynamically Extendable Chords with Non-Harmonic Motions to Improve the Performance of Variable-Speed Tail Rotors

Abstract

Dynamically extendable chords with controlled non-harmonic motions are studied for improving the performance of variable-speed tail rotors. A validated helicopter performance model is utilized, which consists of a rotor, a fuselage, a tail rotor and a propulsive trim method. The results show that the optimal azimuth angles for the deployment of extendable chords are 40°–50° and 130°–140° at the nominal tail rotor speed. In order to improve the efficiency of the extendable chord, a non-harmonic motion of the extendable chord is proposed. Extendable chords can reduce the blade area with high drag and lower the angle-of-attack, which can lead to significant power savings during high-speed flight. Extendable chords are more suitable to reduce the power of variable-speed tail rotors. When the tail rotor speed is reduced by 20%, the power can be reduced up to 19.4%.