NTSB Identification: SEA02LA133.
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Accident occurred Saturday, July 20, 2002 in Pe Ell, WA
Probable Cause Approval Date: 11/25/2003
Aircraft: Cessna 150J, registration: N51286
Injuries: 2 Serious.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

During a VFR cross-country flight, the engine started running rough and would only develop about 2,300 RPM. The pilot tried using carburetor heat for about 90 seconds, without effect. Then some smoke or oil started coming from the engine area. Soon thereafter the pilot heard a "bang" and saw something depart the engine area, and the engine lost all power. He then performed a power-off landing in an old grown-over clear-cut area, and as the aircraft touched down it became entangled in the high vegetation and nosed over. It was later determined that the #2 cylinder had fractured completely around the circumference of the barrel. The cylinder was examined by the NTSB materials laboratory, and it was determined that the cylinder failure was the result of the propagation of a fatigue crack that initiated in the root area between the eighth and ninth cooling fins. The crack advanced circumferentially until the cylinder wall failed between the eighth and tenth fins. Further examination of the initiation site revealed no evidence of surface or material defects, and in the area of the fracture, the cylinder met the drawing requirements for hardness, wall thickness, fin root radius, and material composition and processing. There was no evidence of inadequate lubrication or overheating, and no root cause for the initiation of the fatigue fracture could be determined.

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

The fatigue failure of the number two engine cylinder for undetermined reasons during cruise flight. Factors include high vegetation in the area where the pilot found it necessary to make a forced landing.

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