On March 16, 1995, a Hughes 269A (registration N8873F) was involved in an aviation accident near Van Nuys, CA. Investigators recorded the probable cause as: the operation of the helicopter with improper adjustment of the landing gear and main rotor dampers due to the inadequate maintenance inspection of the helicopter by maintenance personnel and an inadequate preflight inspection by the pilot. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
After a light touchdown, a helicopter began oscillating side-to-side due to ground resonance, continuing until the landing gear structure failed and the helicopter rolled onto its side. Post-accident inspection revealed four landing gear dampers and two main rotor dampers were out of limits. The flight was the first after a 50-hour inspection.
Accident and Findings
The pilot encountered ground resonance immediately after the helicopter landed. The helicopter had touched down lightly on its landing gear system and subsequently began a side-to-side oscillation. This oscillation continued unabated until one side of the helicopter's landing gear structure failed, at which point the helicopter rolled onto its side. A post-accident examination revealed that four landing gear dampers and two main rotor dampers were found to be out of their permissible limits.
Maintenance and Preflight
The accident flight was the first flight following a 50-hour inspection. The inspection required that the landing gear dampers be checked for proper extension. Furthermore, the pilot's preflight preparation should have included verification of both the landing gear dampers and the main rotor dampers.