A Large-Scale Active-Twist Rotor

The feasibility of active-twist rotors, which use piezoelectric actuators incorporated into the blade structure to improve vibration, noise, and performance, has been previously demonstrated in model scale. This paper discusses subsequent research efforts to scale the technology up to meet the needs of a heavy-lift rotorcraft. These efforts include the design and analysis of a full-scale active-twist rotor for the CH-47 and the fabrication and testing of a full-scale blade section. This blade section test article features a production-representative manufacturing approach, large Active Fiber Composite actuator packs, and a robust structurally-integrated power bus. The full-scale design effort showed that the results from previous Mach-scale rotors scale sensibly to full-scale and that a meaningful actuation capability can be achieved within the weight limits of a full-scale passive blade. The blade section validated the manufacturing approach and power bus design. Incorrect polarity of the actuators prevented the section from demonstrating the predicted twist deformation, but measured twists and strain have been correlated with analysis.