Experimental demonstration of the influence of wing couplings on whirl-flutter instability

An experimental demonstration is presented of the influence and the effecti veness of tiltrotor wing couplings in postponing whirl-flutter instability in forward Eight. The experimental setup is based on a small-scale model wh ere the wing supplies a coupled Elastic support hut does not introduce any aerodynamic contribution, The elastic deformation of the beam has been meas ured using a system of strain gauges at its root. Stability characteristics were calculated based on the recorded time history of the system response to an external abrupt disturbance. Beamwise bending-chordwise bending coupl ings were created by tilting the wing structure, whereas beamwise bending-t wist couplings were introduced by changing the nacelle Length. Both types o f the wing coupling effects were found influential. The results indicate th at adequate exploiting of wing coupling effects has the potential to signif icantly improve the stability characteristics of coupled rotor-wing systems .