Incident Overview
During climb after departure, at approximately 3,500 feet, the pilot heard a sequence of loud bangs. The pilot reported that the airplane began to vibrate, prompting him to reduce throttle to idle and initiate a return to the departure airport. Unable to reach the active runway, the pilot elected to land on a grass strip located on the airport property. While attempting to slow the airplane, it impacted a ditch. The airplane nosed over at 40 knots and came to rest inverted.
Engine Examination
Post-incident examination of the engine revealed that the #4 cylinder head had separated from its cylinder barrel. The separation was determined to be a result of fatigue cracking that originated in the cylinder head threads. The engine had been overhauled 111.5 hours prior to the incident, during which six channel chrome overhauled cylinders were installed. The total hours accumulated on these cylinders, as well as the number of overhaul cycles they had undergone, could not be determined. There is no regulatory requirement to track cylinder hours or overhaul occurrences.
Sequence of Events
The pilot's actions following the initial bangs included reducing power and turning back toward the airport. The decision to land on the grass strip was made due to the inability to reach the main runway. The airplane's impact with the ditch occurred during the landing roll, and the resulting nose-over ended with the aircraft inverted. No further mechanical anomalies were reported aside from the cylinder head failure.