The General Purpose Research Rotor - Design Features and Considerations

The General Purpose Research Rotor is a fourbladed configuration with each blade fabricated from composite materials. The GPRR will include dual controls - a pitch horn at the root end and servoflap in the outboard region - to control blade twist and blade airload distributions radially and azimuthally. The blade torsional stiffness will be designed to properly accommodate the dual control system, to avoid aeroelastic instabilities, and to enhance overall rotor performance. The controls will be sized to permit their use as primary controls, as secondary controls or as higher harmonic controls. All three control modes of the GPRR will have the same planform. The compliant rotor will be evaluated by locking out the servoflap and using the pitch horn as the primary control. The advanced servoflap rotor will be evaluated by locking out the pitch horn and using the servoflap as the primary control. The controllable twist rotor will i be evaluated by using the pitch horn as primary control and the servoflap as a secondary control to obtain optimum steady and one/rev twist. Various design features, design considerations, and configuration options are described. An approach is outlined to provide a configuration that will fulfill the GPRR objectives. The selected configuration will be designed for flight tests on the RSRA.