NTSB Identification: LAX96LA291.
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Accident occurred Monday, July 29, 1996 in TRACY, CA
Probable Cause Approval Date: 12/16/1996
Aircraft: Boeing A75N1, registration: N68251
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 that the engine quit while he was en route to a job and he landed in an alfalfa field. The aircraft collided with a ditch which was obscured by the crops. A postcrash fire erupted and consumed the aircraft. The aircraft was examined by an FAA airworthiness inspector. He reported that the engine crankshaft would rotate; however, no corresponding valve action was noted on any cylinder. The inspector observed a disassembly of the engine and reported that the eight screws which secure the crankshaft hub to the crankshaft gear had sheared. The crankshaft gear rotates all accessory drive gears, including the magnetos.

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

A loss of engine power due to the disengagement of the crankshaft gear from it's hub due to the overload shear of the eight retaining screws.

Full narrative available

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