NTSB Identification: SEA98LA188.
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Accident occurred Tuesday, September 29, 1998 in FREELAND, WA
Probable Cause Approval Date: 01/11/2000
Aircraft: Cessna 150L, registration: N5867C
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, while practicing 'S' turns at 2,500 feet above ground, the engine shuddered and then stopped. After an unsuccessful restart, the student maneuvered to a nearby field, and executed a forced landing during which the nose gear folded as the aircraft passed across an irrigation ditch. The aircraft then nosed over. During examination of the engine, the number two cylinder rocker arm for the intake valve was observed to be broken at its hinge point. Inspection of the fracture surface revealed fatigue striations originating in the vicinity of the oil lubrication port on the rocker arm. No mechanical damage or microstructural abnormalities were found associated with the area of apparent fatigue cracking.

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

Failure of the number two intake valve rocker arm in fatigue, and overload of the nose landing gear assembly. Factors include a ditch encountered during the forced landing.

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