NTSB Identification: SEA93LA181.
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Accident occurred Sunday, August 22, 1993 in AUBURN, WA
Probable Cause Approval Date: 08/01/1994
Aircraft: HILLER UH-12E, registration: N9785C
Injuries: 3 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.

DURING A SIGHTSEEING FLIGHT, THE PILOT HEARD A SERIES OF POPS AND THE WARNING LIGHTS FOR THE OIL PRESSURE AND TEMPERATURE ILLUMINATED. THE PILOT INITIATED AN AUTOROTATION TO AN OPEN FIELD. DURING THE LANDING MANEUVER, THE TAIL ROTOR WAS SEPARATED. AN ENGINE INSPECTION REVEALED THAT THE NUMBER 4 CONNECTING ROD SHANK WAS BROKEN INTO THREE PIECES. A METALLURGICAL EXAMINATION OF THE CONNECTING ROD ASSEMBLY REVEALED THAT THE CONNECTING ROD BOLT DISPLAYED A FRACTURE TYPICAL OF A TENSILE OVERSTRESS SEPARATION. THE OTHER CONNECTING ROD BOLT WAS NOT LOCATED.

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

FAILURE OF THE CONNECTING ROD BOLT. THE HIGH VEGETATION WAS A FACTOR.

Full narrative available

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