NTSB Identification: SEA98LA006.
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Accident occurred Saturday, October 18, 1997 in WINSTON, MT
Probable Cause Approval Date: 02/15/2000
Aircraft: Bell 47-G3B, registration: N47AH
Injuries: 2 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.

Post accident inspection revealed a loose bellows housing on the MA-6AA carburetor's automatic mixture control. The bellows housing was found loose on the threaded tube, which was still locked to the seat, allowing the bellows to screw down onto the tube, thereby restricting the fuel delivery orifice. The seat and lock nut remained securely bolted to the float. The last recorded carburetor repair was on 7/22/93, with 817 hours since that repair. Records did not reflect the nature of that repair. According to the carburetor manufacturer's engineering drawings, the bellows is bonded to the threaded tube with a permanent type plastic resin.

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

Fuel starvation due to fuel flow restriction from a failed carburetor automatic mixture control device. Factors include night light conditions for the forced landing.

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