What happened
After touching down lightly on its landing gear system, the helicopter encountered ground resonance. This caused the aircraft to begin oscillating from side to side. The oscillations continued until one side of the helicopter's landing gear structure failed, resulting in the aircraft rolling onto its side.
The investigation
Investigators found that the four landing gear dampers and two main rotor dampers were out of limits. This accident flight occurred immediately following a 50-hour inspection.
Findings
During the 50-hour inspection, the landing gear dampers should have been checked for proper extension. Additionally, the pilot is responsible for checking both the landing gear and main rotor dampers during preflight preparations.