What happened
The aircraft experienced a sudden loss of power while cruising at an altitude of 8000 feet. The pilot was forced to execute an emergency landing due to the engine failure. During the event, oil from the engine sprayed over the windshield, significantly obscuring the pilot's forward vision and complicating the approach.
The investigation
A post-accident examination of the engine revealed catastrophic internal mechanical failure. The top of the crankcase was found to be cracked, with a distinct hole located at the position of the number two cylinder. Investigation confirmed that the bottom of the cap on the number two connecting rod had broken off completely. The connecting rod itself protruded through the hole in the crankcase case, creating the breach that allowed oil to escape.
Records indicated that the aircraft was a 1964 model. According to available documentation, the engine had never been removed from the airframe or subjected to an overhaul during its 22-year service life since new. The total time on both the aircraft and the engine was recorded at 1446 hours. The owner and pilot noted that they expected the engine to last for 1600 hours or more before any such failure occurred.
Findings
The mechanical evidence points to a fatigue-related failure of the number two connecting rod. The lack of an overhaul over 22 years suggests that wear contributed to the structural integrity loss. The resulting breach in the crankcase allowed high-pressure oil to spray onto the windshield, which was a critical factor in the pilot's ability to manage the forced landing.