NTSB Identification: SEA00FA015.
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Accident occurred Thursday, November 04, 1999 in EMIDA, ID
Probable Cause Approval Date: 04/19/2001
Aircraft: Kaman K-1200, registration: N164KA
Injuries: 1 Uninjured.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

Shortly after departure, during the initial climb, the helicopter experienced a sudden loss of power and the pilot initiated a forced landing to a nearby road. Post-accident inspection of the transmission assembly revealed that the splined engine adaptor was fractured due to a torsional overstress imposed on the transmission by the engine. It was determined that the adaptor fracture was secondary to another failure further along in the drive train or transmission. Further examination revealed that the helicopter's freewheeling sprag clutch assembly (located at the drive shaft input to the main transmission) exhibited signs of significant wear to include smearing, non-uniform surface wear and cam deformation. Damage or dragging in this assembly could account for the overstress fracture of the adaptor.

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

Failure of the splined engine adaptor as a result of torsional overstress. Factors include a worn freewheeling clutch assembly.

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