Incident Details
During a precautionary landing with the right engine shut down, an airplane maneuvered and entered a Vmc roll, resulting in an uncontrolled descent. The aircraft subsequently struck wires, trees, and terrain before coming to rest. The wreckage was fragmented and destroyed by impact forces and a post-impact fire.
Flight History
According to air traffic control communications, the pilot experienced a rough running right engine while en route and performed a precautionary shutdown of that engine. The pilot decided to divert to an airport and received vectors from air traffic control for a visual approach.
Witness Accounts
Witnesses located at the airport reported that the airplane was on a normal downwind leg for the intended runway. As the airplane reached the approach end of the runway, the pilot executed a right turn away from the airport. A witness monitoring the UNICOM frequency informed the pilot that he was turning away from the airport, to which the pilot responded, "Busy." The airplane continued the right turn and subsequently entered a Vmc roll and a rapid descent toward the terrain.
Wreckage and Examination
The airplane wreckage was located on hilly, rocky terrain approximately 3 miles south of the airport. Examination of the airframe and propellers revealed no anomalies that would have precluded normal operations. The left engine's forward gearbox was destroyed, but mechanical continuity of rotating components and internal mechanisms was established. Similarly, the right engine's forward gearbox was destroyed, and mechanical continuity was confirmed. The reason for the reported rough running engine could not be determined. It was noted that lifters installed in both engines during overhauls were not approved for those engines.
Probable Cause
The official probable cause was the pilot's failure to maintain minimum controllable airspeed, which resulted in loss of control and impact with wires, a tree, and terrain.