On June 24, 1995, a Bell 47G-2 (registration N1968H) was involved in an aviation accident near Zillah, WA. Investigators recorded the probable cause as: Failure of the left cyclic control rod due to severe corrosion. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter lost lateral cyclic control during low-altitude maneuvering, rolled left, struck trees, and cartwheeled into the ground. Investigation revealed a failed left cyclic control rod due to severe corrosion and lack of annual inspection for over two years.
Accident Sequence
The pilot was maneuvering the helicopter at approximately 50 feet above ground level when he suddenly lost lateral cyclic control. Despite the pilot's corrective efforts, the helicopter began to roll left. The main rotor blades then contacted trees, causing the helicopter to cartwheel into the ground.
Examination Findings
Post-accident examination of the helicopter revealed that a portion of the left cyclic control rod had failed. Further metallurgical examination of the failed component showed that the failure was due to severe corrosion.
Maintenance Records
An examination of the maintenance records disclosed that the helicopter had not received an annual inspection in over two years.
Probable cause
Failure of the left cyclic control rod due to severe corrosion.