What happened
During the cruise phase of flight, the pilot observed the engine becoming rough, accompanied by a drop in oil pressure and fluctuations on the tachometer. These symptoms were followed by a total loss of engine power. The pilot subsequently attempted an emergency landing in a field. After touching down, the aircraft traveled approximately 240 feet before encountering soft dirt, which caused the airplane to nose over.
The investigation
Upon inspection, investigators found that the engine would not rotate, although both oil and fuel were present in the system. Following the disassembly of the engine, it was discovered that the crankshaft had suffered a complete fracture at the number one connecting rod journal. The examination of the fracture site showed a clean break with no visible exterior evidence of prior cracking or deterioration. However, the internal structure of the fracture contained ridges, valleys, and what appeared to be air bubbles near those features.