The helicopter pilot reported that, after landing on the helicopter landing platform, he decided to reposition the helicopter on the platform. He increased collective and, "felt as if the nose was turning or yawing to the right."

To correct the right yaw he applied, "more left pedal but the aircraft continued in its movement." The helicopter rolled to the right and the main rotor blades struck the ground. The helicopter came to rest on its right side.

The helicopter sustained substantial damage to the main and tail rotor drive system.

The pilot reported that there were no preaccident mechanical failures or malfunctions with the helicopter that would have precluded normal operation.