Incident Summary
Shortly after initiating an enroute letdown, the aircraft experienced a catastrophic engine failure at approximately 4,500 feet mean sea level. The pilot selected a road for an attempted emergency landing, but a car turned onto the road in front of the aircraft, forcing a diversion to a nearby field. Upon touchdown, the aircraft encountered berms, ruts, and clumps of bushes.
Engine Examination
Examination of the engine revealed that the number 6 cylinder connecting rod had failed near the crankshaft end. High cycle fatigue was evident over approximately 60% of the material thickness.
Maintenance Records
Review of the aircraft maintenance records disclosed that since its manufacture in 1964, the aircraft had accrued a total of 1,299 hours, with only 109 hours in operation since 1976. Lycoming publications indicated that the connecting rod had been superseded in production several times, and that this particular part number was not allowed for reuse at overhaul. The manufacturer's recommended overhaul period is 1,800 hours or 10 years time in service, whichever comes first.