WHIRL-FLUTTER SUPPRESSION IN ADVANCED TURBOPROPS AND PROPFANS BY ACTIVE CONTROL TECHNIQUES

The feasibility of using the active control technique to suppress the whirl-flutter instability of advanced turboprops is investigated. Aerodynamic vanes are incorporated at the engine nacelle to generate control airloads. The actuator system is driven by a control law that 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 both by optimizing the engine-propeller suspension in the actual flying envelope and by employing the active control technique to deal with the safe margins required by the present aircraft certification regulations.