Whirl-Flutter Suppression in Advanced Turboprops and Propfans by Active Control Techniques - Part II.

Abstract

The feasibility of using the active control technique to suppress the whirl-flutter instability of advanced turboprops is further investigated. Aerodynamic vanes are incorporated at the engine nacelles to generate control airloads. The actuator system is driven by a control law which is based on the Kalman filter estimation of the critical aeroelastic modes of the structure. The results demonstrate that the compensator provides enough controllability to prevent the whirl-flutter onset well beyond the design speed. The present study suggests that a very efficient vibration isolation in advanced turboprops may be achieved by both optimizing the engine-propeller suspension in the actual flying envelope, and employing the active control technique to deal with the safe margins required by the present aircraft certification regulations.