NTSB Identification: DEN00LA045.
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Accident occurred Saturday, January 29, 2000 in MT PLEASANT, UT
Probable Cause Approval Date: 07/02/2001
Aircraft: Bell 212, registration: N212HQ
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.

While in level flight approximately 120 feet above ground level, carrying an external load of logs, the main rotor mast separated from the helicopter. The fuselage descended into a tree covered slope and broke into three sections. The pilot received serious injuries. Laboratory examination of the main rotor mast provided evidence the mast failed in fatigue at the lower ring groove of the damper splines where burrs were left during machining of the part. Retirement requirements for the mast were 15,000 flight hours or 300,000 RIN (retirement index number). The mast had 5,644.4 hours with the last overhaul being done at 3,660.8 hours. The FAA calculated the RIN number to be 291,065.

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

Failure of the main rotor mast due to fatigue that resulted from inadequate quality assurance during the manufacturing process.

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