Incident Overview
According to the pilot, about ten minutes after takeoff, the engine began to run roughly. During troubleshooting, the pilot noted that all indications appeared normal except for low fuel flow. He then advanced the throttle, switched fuel tanks, and turned on the fuel boost pump. Shortly thereafter, a loud bang was heard from the engine, followed by a complete loss of engine power.
Forced Landing
With no engine power, the pilot conducted a forced landing onto an access road adjacent to a highway. The aircraft came to rest on the road surface. No further details about the landing or post-landing events are available from the report.
Postaccident Examination
Examination of the engine after the incident revealed that the number four cylinder had separated from the crankcase. The fractures of the cylinder hold-down studs showed no clear evidence of fatigue cracking. Instead, the fractures were representative of overstress separations. Additionally, fretting damage was observed on the mating cylinder flange, crankcase boss, and metal folds on the cylinder flange/hole wall corners.
Conclusion
The investigation determined that the cylinder separated due to overstress, but no probable cause was explicitly stated in the source.