Design Variables For A Controllable Twist Rotor

The controllable twist rotor features a torsionally-flexible helicopter blade with a dual control system. Inboard pitch horns, swashplate and actuators provide conventional primary control. An aerodynamic trim tab near the blade tip, actuated collectively and cyclically, gives control over blade twisting. The ability to optimize blade pitch distribution along the radius and around the azimuth promises improved performance, delayed retreating blade stall, and reduced bending moments and vibration levels. Design of a test rotor is described, with discussion of the principal design variables and their influence on rotor performance, dynamics and cost. The procedure by which an efficient combination of design variables was developed, the resulting configuration and its performance, under analysis and in whirl stand testing, are described.