Effects of 2/rev Trailing Edge Flap Input on Helicopter Vibrations for Concurrent Vibration and Noise Reduction

For the simultaneous operation of two independent active rotor controllers, one with the goal of reducing helicopter vibration, the other aiming at BVI noise reduction, the interactions between the two control tasks need to be considered in order to achieve an optimal operation. In this work, the direct interactions between BVI noise reduction using 2/rev trailing edge flap inputs and vibration reduction are investigated in the form of effects of 2/rev trailing edge flap input on 4/rev helicopter vibration. The purpose of this investigation is to find models describing this kind of interaction in order to determine an optimal way for simultaneous operation of independent controllers for the reduction of BVI noise and helicopter vibration. To this end, flight data consisting of two flight tests with a full-scale EC145, the rotor of which was equipped with trailing edge flaps, is examined. From one part of the flight data a model, based on a transfer matrix approach, is derived, the other part of the flight data is used for validation. Finally the robustness of the model is examined by looking at flight data at different flight conditions.