What happened
After notifying air traffic control that the engine had experienced a partial loss of power, the pilot attempted an emergency landing at an airport. Witnesses on the ground observed the aircraft touch down with excessive speed and a long touchdown distance, subsequently initiating a go-around maneuver.
During this phase of flight, the airplane was seen performing a climbing right turn with a high nose attitude and a lack of airspeed. The aircraft's nose then dropped, resulting in a collision with trees and the terrain while in a nose-down attitude. All occupants were not injured.
The investigation
Upon disassembly of the engine, investigators discovered that the piston plugs on the No. 3 and No. 5 cylinders had been installed on the forward sides of both pistons. This specific installation allowed the unprotected ends of the pins to rub against the cylinder walls. While the remaining cylinder assemblies were found to be correctly installed, a review of the engine logbook indicated that the engine had not undergone disassembly since its original assembly by the manufacturer.