Accident Summary
A commercial helicopter pilot, who held a helicopter rating and had accumulated 6,500 flight hours, inadvertently encountered ground resonance while ground taxiing the helicopter. The sequence of events began with a normal startup and preparation for taxi. The pilot moved the helicopter forward and then initiated a 90-degree ground taxi turn, executed in 30-degree intervals.
Sequence of Events
During the taxi, the pilot applied the toe brakes to stop the helicopter in order to give right of way to another aircraft taxiing down the taxiway. At that moment, the helicopter began to shake and bounce. Before the pilot could shut down the aircraft, the helicopter executed an uncommanded 90-degree turn to the left. Subsequently, the helicopter's main rotors and transmission assembly separated from the airframe.
Weather Conditions
At the time of the accident, the wind was reported from 170 degrees at 17 knots, gusting to 23 knots.
Probable Cause
The probable cause of the accident is that the pilot inadvertently encountered ground resonance while ground taxiing.