Incident Overview
During cruise flight at 3,000 feet, the pilot experienced slight engine surging and fluctuations in manifold pressure. After the surging ceased, approximately 30 seconds to one minute later, engine power suddenly reduced to idle and became rough. Shortly thereafter, the engine lost all power. The pilot executed a forced landing onto a paved road, but the airplane veered left and the left wing struck a small tree, resulting in substantial damage.
Engine Inspection Findings
Post-incident inspection of the engine revealed that the connecting rods for cylinders 3, 4, and 5 had broken loose from the crankshaft. The corresponding crank journals showed evidence of extreme heat. The number 6 piston exhibited a fatigue fracture across the piston crown structure, aligned with the piston pin. A hole was burned through the piston near the center of the crown along the fracture line, exposing the piston interior. The fracture originated at the crown surface. No number stamp or defects were observed at the fracture origin. Analysis indicated no material defects or surface anomalies at the origin of the larger fatigue crack, and the base metal composition matched AE109 specification. The engine manufacturer reported it was in the process of redesigning the piston used in the 310 horsepower TSIO-550-C engines.