NTSB Identification: LAX99LA061.
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Accident occurred Tuesday, December 29, 1998 in SAN YSABEL, CA
Probable Cause Approval Date: 02/16/2001
Aircraft: Ercoupe (Eng & Research Corp.) 415-C, registration: N99371
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.

In cruise flight at 4,500 feet, the pilot added power as the terrain began to rise, then the engine started to vibrate. As the pilot looked down to check the mixture and carburetor heat, the vibration intensified. The crankshaft fractured and the propeller separated from the airplane. The pilot subsequently made a forced landing on uneven terrain and the nose gear collapsed. Metallurgical laboratory examination of the remaining crankshaft piece determined the crankshaft separated forward of the oil-slinger flange due to fatigue. The fatigue region had an origin point in an area mechanically damaged during the crankshaft failure.

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

A fatigue fracture of the crankshaft and the resulting separation of the propeller.

Full narrative available

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