Accident Sequence
During the initial takeoff climb, the pilot heard a "loud bang" from the engine. This was accompanied by a smell of fuel in the cockpit, a loss of fuel pressure, and substantial engine vibration. The pilot attempted to return to the airport, but the engine lost power, prompting a forced landing. During the landing, the airplane impacted a cattle gate and came to rest on its nose.
Engine Examination
Examination of the engine revealed that the #1 lower connecting rod bolt was fractured at the bolt's dowel section, corresponding to the split line between the connecting rod and rod cap. According to the engine manufacturer's metallurgist, the fracture initiated at the outer diameter of the bolt's dowel section. The fracture progressed in fatigue until the bolt fractured as a result of overstress. The bolt's dowel section exhibited fretting damage at the fracture origin.
Maintenance History
At the time of the accident, the engine had accumulated 9.64 hours since the annual inspection and 195.84 hours since major overhaul.