Accident Summary
Approximately eight minutes after departure, the pilot informed air traffic control that the cabin was filling with smoke and that he was diverting to a nearby airport. The airplane subsequently collided with trees approximately 30 to 40 feet tall bordering an open field, then contacted the terrain. A post-impact fire ensued.
Engine Examination
Inspection of the engine revealed two holes in the crankcase near the number four cylinder, and the number four piston rod was separated from the crankshaft. Teardown of the engine disclosed five cylinder deck stud nuts were missing, and the number five cylinder seventh stud had sheared. The crankshaft, counterweights, and rod bearings exhibited thermal damage, most prominent at the number four cylinder connecting rod journal. Material from the number four connecting rod bearing was fused to the crankshaft journal, displacing the oil tube toward the number three main journal.
The cylinders had been removed and overhauled approximately 380 hours before the accident. The cylinder base packings on all cylinders were flattened and extruded between the base of the cylinders and the crankcase. The cross-section diameter of these packings was larger than that of a sample packing (part number 641066) used on IO-520-BA engines, and similar in diameter to packings used on O-470 series engines.