What happened
While cruising at 7,500 feet, approximately 12.2 nautical miles from Norfolk Airport, the aircraft's engine began to run roughly. The pilot reported that the propeller setting remained unchanged until the aircraft was directly overhead the airport. At that point, a loud explosion occurred, causing the oil access door to blow open and engine components to be ejected from the aircraft.
The pilot performed a forced landing on Runway 23, during which the aircraft touched down on the grassy area adjacent to the runway. The occupants were not injured.
The investigation
Mechanical examination of the engine revealed that the number 2 cylinder assembly, including the piston and connecting rod, had separated from the crankcase at the cylinder hold-down stud area.
To facilitate a metallurgical analysis, the crankcase and the hold-down studs were sent to the NTSB laboratory in Washington, D.C. The examination identified fatigue cracks within the components. Additionally, investigators found evidence of welding through the crankcase, noting that the welded sections were softer than the unwelded portions of the metal.