Accident Overview
Shortly after takeoff, the aircraft caught fire. The pilot attempted to turn back to the airport, but the engine lost power and the aircraft could not maintain altitude. It subsequently crashed into a heavily wooded state park.
Findings
During the post-accident examination, the #5 cylinder exhaust pipe was found separated. The separated pipe was not burned or sooted. Extensive melting was evident around the intake and exhaust ports on the #5 cylinder. The head of the #5 cylinder was completely burned through.
Maintenance History
The aircraft had completed an annual inspection 30 hours prior to the accident. Records revealed that the exhaust system gaskets had been replaced during that inspection.
Metallurgical Examination
Metallurgical examination with a scanning electron microscope showed no evidence of nut-tightening marks on the failed exhaust pipe flange. In contrast, distinct nut-tightening marks were observed on two exhaust pipes that remained attached.