Primary finding
Probable cause
The fatigue cracking fracture of the propeller hub, resulting in a forced landing, and collision with a house.
Investigator assessment
Analysis narrative
The pilot said, 'while crusing at 9500 feet...there was a 'boom'...i realized...the engine just blew...' during the forced landing, the airplane struck a house. Examination of the maintenance records revealed that there had been two propeller strikes with this airplane. An examination of the engine revealed no malfunction or defect which would have contributed to the failure. The propeller blade hub assembly was examined by the NTSB metallurgist. In his report he stated: 'the hub failed as a result of fatigue cracking....the origin of the fatigue was not located on a part of the hub that was recovered. Damage to the preload plate shelf...indicated that the hub had previously experienced a blade strike....the ground strike could have had an affect on the failure of the hub, but without the origin area for examination other...causes...cannot be ruled out.'
Source record
Factual narrative
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