Experimental research on whirl flutter of tiltrotor aircraft

Abstract

The instable phenomenon of the tiltrotor aircraft's whirl flutter is induced from the aeroelastic coupling between flapping of the rotor and bending/torsion of the flexible wing when its flight velocity exceeds the critical speed of the stability boundary. The wind tunnel test using semi-span model is an effective and convincing method to validate the accuracy of analytical methodologies and effect of active/passive control techniques to suppress whirl flutter. A semi-span model was developed and fabricated to conduct tests related to aeroelastic problems of tiltrotor aircrafts. Tests were carried out to ascertain the critical speed of this model with different configurations including rotor/wing tests and rotor/wing/fuselage tests. The stiffness of this model was adjusted to guarantee that whirl flutter would occur in wind tunnel test. Good agreement was shown in the comparison between results of the wind tunnel tests and the theoretical analysis, which indicated that the semi-span model designed in this study and the corresponding theoretical analysis method were capable for studies of whirl flutter problems.