Accident Sequence
The pilot reported that while climbing to cruise flight, he heard a bang from the engine, followed by a major vibration. The engine continued vibrating and he was unable to maintain altitude, so he pulled the aircraft into a stall to stop and feather the propeller. He stated that he attempted to land in a parking lot, but came in too high and too fast. He touched down on a road and collided with a berm.
Aircraft and Engine Examination
A Federal Aviation Administration (FAA) inspector examined the aircraft and noted two holes in the engine case above the forward cylinder's connecting rods. Further examination of the powerplant revealed that the Nos. 2 and 6 cylinders were intact. Neither piston displayed any sign of heat discoloration around the skirts. Combustion deposits were noted on the piston crowns. There was no staining or piston crown edge erosion. Both skirts were failed. The No. 4 cylinder piston was disintegrated around the pin. The piston rod was bent and the piston pin was still intact through the rod wrist. Neither the rod nor the pin displayed any indication of heat distress. There was no scoring noted inside the cylinder barrel. The No. 4 bottom sparkplug was fouled with metal. The sump contained oil and large chunks of pistons.
The pilot reported that the Continental O-470-U engine had 2536.1 hours of total time, 75.2 hours since the last inspection, and 806.8 hours since the last overhaul. The maintenance records revealed that the six pistons, each with a Superior Air Parts, Inc., part number SA 648029, were installed during the last major engine overhaul on February 19, 1990.