Accident Details
A helicopter involved in a previous accident due to a tail rotor strike was repaired, inspected, and returned to service. As part of the repairs, the four landing gear dampers were serviced. Following a main rotor track and balance check with no discrepancies noted, the helicopter was cleared for flight.
During a landing from a hover, the pilot reported that the helicopter began to oscillate fore and aft, characteristic of ground resonance. At that time, full power was applied and the collective control was down. The pilot did not raise the collective. Subsequently, the left skid failed, causing the helicopter to roll onto its left side.
Investigation Findings
Post-accident examination revealed that three of the four landing gear dampers were improperly serviced. The main rotor blade dampers were tested and found to be free of preimpact failure or malfunction. The improper servicing of the landing gear dampers was identified as a contributing factor to the occurrence of ground resonance and the subsequent rollover.
Conclusion
The accident resulted from the helicopter entering ground resonance during landing, leading to structural failure of the left skid. The root cause was determined to be improper servicing of the landing gear dampers.