Incident Summary
The pilot reported that the takeoff and climb to 2,200 feet MSL were normal. Following the transition to cruise configuration, he heard an abnormal noise and elected to return to the departure airport. As he proceeded, the noise intensified and the engine began to vibrate. A piece of metal was observed protruding through the cowling. The pilot shut down the engine and turned off the master switch. He selected a suitable area for a forced landing. Before touching down, he momentarily turned on the master switch to lower the flaps. The airplane touched down on hilly terrain, resulting in substantial damage.
Investigation Findings
Post-accident examination showed that the No. 2 connecting rod had become disconnected from its crankpin. The bearing was disintegrated, the crankpin exhibited black discoloration consistent with thermal damage, and the rod bolts were fractured. The specific reason for the failure could not be determined.