Forced Landing on Gravel Road
The pilot of a single-engine aircraft executed a forced landing on a gravel road following a complete loss of engine power. The flight had been airborne for approximately 20 minutes and the pilot was in cruise flight when the engine emitted a loud noise, began to vibrate severely, and subsequently lost power. During the landing, the right wing struck a road sign.
Engine Examination Findings
A post-accident examination of the engine revealed a fracture in the engine case in the vicinity of the No. 6 cylinder, and the cylinder's base had become displaced away from the case. The engine could not be rotated by hand, but oil was present in the oil pan.
Further inspection showed that the piston in cylinder No. 1 had fractured and separated at the piston pin. The piston rod continued to rotate, causing the camshaft to fracture into two halves and separating both magnetos. The piston rings in cylinder No. 1 also fractured and scored the interior wall of the cylinder in the direction of the cylinder stroke.
No discoloration of engine components or other signs of oil starvation were observed. Additionally, there was no mechanical damage on the piston face that would indicate the possibility of a stuck valve.
Maintenance History
The aircraft had received its annual inspection one month prior to the accident, and all applicable airworthiness directives and required inspections had been complied with. The engine manufacturer recommends that this engine model be overhauled at 1,500 hours of operation. At the time of the accident, the engine had accumulated over 1,820 hours since its last overhaul.