Abstract:
The next generation of rotorcraft will require advanced rotor systems to deliver better performance and vibration characteristics. Rotor system design has always been one of compromise - traditionally between the hover and cruise regimes. It has long been recognized that the optimal geometry (twist, chord, sweep) for hover performance does not perform optimally in forward flight. In addition, optimizing the rotor design for hover can result in unintended consequences, such as increased vibration, that often accompanies suboptimal cruise performance. The long-sought benefit of an active rotor system is to adapt its geometry or its operation to mitigate the penalties in one regime or the other, expanding the design space afforded the designer. Although active rotor systems have been demonstrated in recent years, they have used primarily on-blade active devices, and the benefits have not addressed all of the next generation rotor goals. The goal of the Multi-Role Rotor Technology Investment Agreement (TIA) between Boeing and the Army Aviation Development Directorate (ADD) is demonstrating technologies that avoid rotor design compromises in order to improve rotor performance and reduce vibration levels. The development of the innovative Multi-Role Rotor - Adaptive Performance (MRRAP) rotor promises the ability to truly adapt a blade to maximize hover and cruise efficiencies, while also incorporating control capabilities to reduce vibration.