Incident Description
The pilot was performing a hover taxi from the west side of the airport to his hangar on the east side. He reported lifting the helicopter to approximately three feet in a hover when the cyclic began rotating in a circle of about six to eight inches in his hand. The pilot heard a low pitch or frequency oscillation. Subsequently, the helicopter began a strong uncontrollable roll to the left. The pilot attempted to push the cyclic to the right but found no change in stopping the roll or direction of movement. Aware that airplanes and people were in the direction the helicopter was heading, the pilot decided to put the helicopter down on its side to prevent further movement. A witness observed the helicopter lift off the ramp to an estimated height of three to five feet. The tail rotor then struck the ramp, and the helicopter impacted on its left side.
Damage and Examination
The accident resulted in substantial damage to the main rotor blades, tail rotor, skids, and cockpit area. An examination of the helicopter's systems revealed no anomalies. Wind conditions in the area, recorded approximately 30 minutes prior to the accident, were from 350 degrees at 11 knots with gusts to 16 knots.
Previous Maintenance
According to the mechanic who had performed the previous annual inspection on the helicopter, the aircraft would experience a small amount of stick swirl when in hover. The mechanic noted that 'if you work it, it will go away.'