What happened
While operating in cruise flight at 4,500 feet, the aircraft experienced a catastrophic engine failure. In response to the failure, the pilot declared an emergency and initiated the appropriate emergency checklists. The pilot identified a flat field for an emergency landing; however, during the landing roll, the aircraft struck a barbed wire fence. This impact caused damage to the wings and resulted in the collapse of the nose gear.
The investigation
The engine was returned to the Textron Lycoming factory for a materials examination. Investigators determined that the No. 6 connecting rod initially fractured through the cap. The fracture likely originated from an area of galling located on the inner diameter of the cap, with the fracture propagating via a fatigue mechanism until it reached catastrophic overload.
During the investigation, additional disassembly of the engine was performed in a manner that did not follow established investigative protocols. Because of this, no measurements were recorded regarding the torque of the case through bolt or the remaining rod end cap bolt. Furthermore, investigators could not determine if the bearing inserts were the correct size or if they had been properly assembled during the engine build-up.
Maintenance records indicated that the engine had been remanufactured by the Lycoming factory in 1991. At the time of the accident, the engine had operated for 869 hours since its rebuild and installation in the airframe. The records showed no instances of cylinder removal or replacement.