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Self-excited vibration of the helicopters on the ground has been the cause of several accidents. It is, therefore, essential for the helicopter design that serious attention should be paid to the methods of ensuring freedom from such phenomena. In this paper, the theory of Coleman is reviewed and the results of the experimental investigations of several model rotors and small viscous dampers are presented. The models were built to represent the dynamic system of the rotor head without the freedom in the"y"direction to avoid the experimental errors. The test results showed, as expected, that the viscous dampers and the drag hinge offsets have large effect on the characteristics of ground resonance of the helicopter. The comparison between the experimental and the theoreticatl resuls, affords that Coleman's theory is useful forengineering practice.

Correlation Study for Ground Resonance of the Helicopter by the Model Tests