On June 20, 1987, a Bell 47G-2 (registration N6772D) operated by Kimura International was involved in an aviation accident near Miami, FL. Investigators recorded the probable cause as: The bolt attaching one side of the swashplate to the scissor assembly broke, resulting in the loss of pitch control of the main rotor blades. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 1 related events involving the same aircraft type or operator are linked below.
During an instructional flight, a helicopter began vibrating, leading to a forced landing. Post-landing inspection found a broken bolt in the swashplate assembly, causing loss of main rotor pitch control.
Incident Overview
During an instructional flight, the helicopter experienced vibrations while the student pilot was maneuvering. The instructor pilot took control and executed a forced landing. Upon touchdown, the main rotor blades struck the ground.
Inspection Findings
A post-incident inspection revealed that the bolt attaching one side of the swashplate to the scissor assembly had fractured. This failure resulted in a loss of pitch control for the main rotor blades.
Conclusion
The investigation determined that the broken bolt was the direct cause of the loss of control leading to the forced landing and subsequent rotor blade contact with the ground.
Probable cause
The bolt attaching one side of the swashplate to the scissor assembly broke, resulting in the loss of pitch control of the main rotor blades.