19990528006159A

Acft lost power, landed in a field. (.4)the airplane had a catastrophic engine failure while the pilot was in cruise flight at 4,500 feet. The pilot declared an emergency and began to perform the emergency checklist. The pilot located a flat field and struck a barbed wire fence during the landing roll, which damaged the wings and collapsed the nose gear. The engine was sent back to the Textron Lycoming factory for materials examination. The no. 6 connecting rod initially fractured through the cap with the fracture most likely initiating from an area of galling on the inner diameter of the cap. The fracture was propagated by a fatigue mechanism until it failed with catastrophic overload. Following the metallurgical examination on the no. 6 connecting rod and associated components, additional disassembly of the engine was accomplished that 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 whether the bearing inserts were of the correct size or assembled properly in engine build-up. Review of the engine maintenance reco rds disclosed that it was remanufactured by the Lycoming factory in 1991, and had operated 869 hours since rebuild and installation in the airframe. No removal and replacement of cylinders was noted in the records. (-23)aircraft made an off airport landing due to catastrophic engine failure causing substantial damage to aircraft.