NTSB Identification: CHI97LA306.
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Accident occurred Tuesday, September 30, 1997 in PIPESTONE, MN
Probable Cause Approval Date: 11/17/1999
Aircraft: Bell 47, registration: N9005T
Injuries: 1 Serious.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The pilot stated that while he was ferrying the helicopter to the next field he, 'heard a loud bang from behind.' He said that the cyclic control, 'jerked,' the helicopter began to vibrate, and the rotor RPM decreased. He increased the throttle, but the engine responded as if there was no load on the engine. He initiated autorotation, but was unable to regain control, and the aircraft impacted the terrain. Post accident investigation revealed that one of two pitch control rod assemblies had fractured between the clevis and turnbuckle. Examination of the fracture showed areas of fatigue striations and multiple crack initiation sites on the machined surface.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

the fracture of the pitch control rod assembly.

Full narrative available

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