Vibratory Loads Reduction Testing of the NASA/Army/MIT Active Twist Rotor

Recent studies have indicated that controlled strain‐induced blade twisting can be attained using piezoelectric Active Fiber Composite technology, and that such advancement may provide a mechanism for reduced rotorcraft vibrations and increased rotor performance. To validate these findings experimentally, a cooperative effort between the NASA Langley Research Center, the Army Research Lahoratory, and the MIT Active Materials and Structures Lahoratory has been developed. As a result of this collaboration a four‐bladed, aeroelastically scaled, active‐twist model rotor has been designed and fabricated for testing in the heavy gas test medium of the NASA Langley Transonic Dynamics Tunnel. Initial wind tunnel testing has been conducted to assess the impact of active blade twist on both fixed‐ and rotating‐system vibratory loads in forward flight. The active twist control was found to have a pronounced effect on all system loads and was shown to offer generally reductions in fixed‐system loads of 60% to 95%, depending upon flight condition, with 1.1° to 1.4° of dynamic blade twist observed. A summary of the systems developed and the vibratory loads reduction results obtained are presented in this paper.