Accident Details
An aerial application helicopter departed at approximately 1030 hours. After it was determined to be 45 minutes overdue, search efforts were initiated. The wreckage was located around 1300 hours in a marshy and grassy area.
Investigation Findings
Examination of the engine revealed no evidence of pre-impact mechanical failure or malfunction. Examination of the airframe showed evidence consistent with power being present on the rotor system at the time of impact. The helicopter frame aft of the cabin was connected and displayed little damage, but the short shaft had become detached. The universal joint, tail rotor drive yoke, tail rotor guard fork assembly, and their attachment points on the aft end of the tailboom exhibited fractures and mechanical damage consistent with overload.
Further analysis determined that the characteristics of the fractures and mechanical damage were consistent with overload from the tail rotor drive yoke, tube and gearbox pivoting up and forward around the two attachment lugs at the top side of the aft end of the tailboom. An area where paint had been scraped off was noted along the bottom of the tail rotor guard.
Witness Reports
Witnesses reported two tail strikes involving the aircraft prior to the accident flight. One witness reported seeing the helicopter hit its tail on the ground during landing earlier on the day of the accident. Another witness reported seeing the tail boom come into contact with the ground during landing a day earlier.
Examination of Prior Strike Site
The site where the helicopter had reportedly hit its tail on the day prior to the accident was examined. A rounded impression was observed in a sodden area, consistent with the size and shape of the helicopter's tail rotor guard.