Incident Overview
At an altitude of 12,000 feet above ground level, the pilot encountered severe engine vibrations. Simultaneously, oil was observed escaping from the engine cowling and spreading onto the windshield. The pilot notified air traffic control, who initially provided vectors to an airport located approximately 18 miles away.
Forced Landing
As the oil on the windshield increasingly obscured visibility and the engine vibrations intensified, the pilot decided to abandon the attempt to reach the airport and instead conducted a forced landing off the airport. The landing was performed on wet, plowed terrain. During the landing roll, the airplane nosed over.
Examination Findings
Subsequent examination of the engine revealed that four of the number two cylinder studs exhibited multi-origin fatigue at the fracture surface. This condition was attributed to improper stretch or torque applied to the studs.