Incident Details
The flight was cruising at 7,500 feet when the engine began to run rough approximately 12.2 nautical miles from Norfolk Airport. The pilot stated that he did not change the propeller setting until overhead the airport. Shortly thereafter, a loud explosion occurred, the oil access door blew open, and pieces of the engine exited the airplane. During the subsequent forced landing on Runway 23, the airplane touched down on the grassy area.
Examination Findings
Post-incident examination revealed that the No. 2 cylinder assembly, piston, and connecting rod had separated from the crankcase at the cylinder hold-down stud area. The hold-down studs and crankcase were sent to the NTSB laboratory in Washington, DC, for metallurgical examination. The examination disclosed fatigue cracks and evidence of welding through the crankcase. The welding areas were found to be softer than the areas that were not welded.