Narrative
During cruise flight, the pilot experienced a vibration that continued. Subsequently, oil began covering the windshield, and the engine lost power. Air traffic control vectored the flight toward a nearby airport. However, the pilot did not communicate his intentions to perform a forced landing over the correct UNICOM frequency. Due to an airplane ahead on the runway, he landed hard on the displaced portion of the runway.
Examination
Post-incident examination of the engine revealed several holes in the crankcase near the Nos. 1 and 4 cylinders. The connecting rods for the Nos. 1 and 4 cylinders had failed. Metallurgical examination of the failed components showed high stress low cycle fatigue on the No. 4 connecting rod. Additionally, galling was noted in critical areas on the Nos. 1, 2, and 4 connecting rods and/or their caps.
A service bulletin indicated that galling in critical areas could cause failure of connecting rods, and that galling could occur as a result of high loading such as during engine overspeed or operation with excessive manifold pressure. The engine had been overhauled by the manufacturer and had accumulated approximately 1,252 hours since that overhaul.