Primary finding
Probable cause
The improper welding of the inboard boss by an unknown person resulting in a fatigue failure on the inboard boss. A factor related to the accident was the vehicle that was struck during the forced landing.
Investigator assessment
Analysis narrative
During flight at 8000 feet, the engine lost power. The pilot tried to make a forced landing at lake havasu airport, but was unable to reach the airport. He selected a roadway about 2 1/2 miles south of the airport. During the final approach to the roadway, the airplane struck a vehicle. A metallurgical examination revealed that the number two cylinder's inboard boss had been welded. The weld repair is specifically prohibited by teledyne continental motors specification mhs 217. This unapproved weld led to significant softening of the inboard boss, and a reduction of fatigue strength. The airplane records revealed that the cylinders had been purchased at a auction, and the cylinder's maintenance history is unknown. The airplane records did not reflect that any welding repairs were performed on the number two cylinder.
Source record
Factual narrative
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