Incident Summary
While in cruise flight at 4,500 feet, the airplane suffered a catastrophic engine failure. The pilot declared an emergency and initiated the emergency checklist. Selecting a flat field for landing, the aircraft struck a barbed wire fence during the landing roll. The impact damaged the wings and collapsed the nose gear.
Engine Examination
The engine was sent to the Textron Lycoming factory for materials examination. Investigators found that the No. 6 connecting rod initially fractured through the cap. The fracture most likely originated from an area of galling on the inner diameter of the cap. This fracture propagated by a fatigue mechanism until it failed due to catastrophic overload.
Following the metallurgical examination of the No. 6 connecting rod and associated components, additional disassembly of the engine was performed. This disassembly did not conform to investigative protocols. No measurements were taken of the case through bolt torque or the remaining rod end cap bolt torque. No determination was made regarding whether the bearing inserts were of the correct size or assembled properly during engine build-up.
Maintenance Records
Review of the engine maintenance records disclosed that the engine was remanufactured by the Lycoming factory in 1991. It had operated for 869 hours since its rebuild and installation in the airframe. No removal and replacement of cylinders was noted in the records.