What happened
During an en route flight, the pilot reported that the right engine was running roughly. In response, the pilot performed a precautionary shutdown of the right engine and requested a diversion to a nearby airport. Air traffic control provided vectors for a visual approach, and witnesses at the airport observed the aircraft on a standard downwind pattern for the runway.
As the aircraft reached the approach end of the runway, the pilot initiated a right-hand turn that directed the plane away from the airfield. Although a witness on the UNICOM frequency alerted the pilot that the turn was leading away from the airport, the pilot did not correct the maneuver. During this turn, the aircraft entered a Vmc roll, resulting in a rapid, uncontrolled descent. The aircraft struck trees, wires, and the ground approximately 3 miles south of the airport. The impact and subsequent fire resulted in the total destruction of the aircraft.
Findings
Investigations into the wreckage showed that the airframe and propellers were in normal condition and showed no signs of malfunction prior to the crash. While both engines had destroyed forward gearboxes, the internal rotating components and mechanisms remained mechanically continuous. Investigators were unable to identify the specific cause of the initial engine roughness. However, it was noted that the lifters installed in both engines during previous overhauls were not approved parts for these specific engines.