NTSB Identification: SEA94LA029.
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Accident occurred Tuesday, November 09, 1993 in TOLEDO, WA
Probable Cause Approval Date: 12/02/1994
Aircraft: BELL 47G3B2, registration: N8169J
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.

WHILE LIFTING CHRISTMAS TREES UNDER EXTERNAL LOAD CONDITIONS THE PILOT HEARD A CLUNK AND EXPERIENCED A LOSS OF POWER. HE ATTEMPTED AN AUTOROTATION FROM 40 TO 50 FEET INTO THE CHRISTMAS TREE FARM, STRIKING AND BENDING THE TAIL BOOM WHEN IT IMPACTED A TREE. INVESTIGATION REVEALED THAT THE TRANSMISSION SHEAR BOLTS, PN 47-620-485-9, HAD SHEARED. THE PILOT ATTRIBUTED THE FAILURE OF THE SHEAR BOLTS TO POWER IMPULSES FROM REPEATED COMPRESSOR STALLS.

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

TRANSMISSION SHEAR BOLTS FAILED CAUSING A LOSS OF POWER TO THE ROTOR SYSTEM, AND THE PILOT ENCOUNTERED UNSUITABLE TERRAIN DURING HIS AUTOROTATION ATTEMPT.

Full narrative available

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