NTSB Identification: DFW08LA100
14 CFR Part 137: Agricultural
Accident occurred Monday, April 07, 2008 in Quinton, OK
Probable Cause Approval Date: 12/24/2008
Aircraft: Hiller UH-12E, registration: N34SD
Injuries: 1 Uninjured.

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 reported hearing a loud noise and experiencing vibrations while piloting his helicopter in cruise about 1,000 feet above the ground. The pilot performed an autorotation to an open field, and was able to maintain control of the helicopter throughout the autorotaion. The pilot reported that a tail rotor strike did not occur. Failed parts from the transmission, tail rotor blades, and associated tail rotor drive hardware were submitted to the NTSB for metallurgical examination. All parts appeared to have failed in overload; however, the origin of the overload failures, or whether they were pre- or post-impact, could not be determined

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

An undetermined mechanical malfuction associated with the tail rotor drive system which led to a loss of control.

Full narrative available

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