Accident Sequence
After climbing to and leveling at 15,000 feet, the airplane departed controlled flight, descended rapidly in a nose-down vertical dive, and impacted terrain. An explosion and postaccident fire occurred. Most of the wreckage was located in or near a single impact crater; however, the outer portion of the left wing impacted the ground about half a mile from the main wreckage.
Pilot and Aircraft Background
Following the previous flight, the pilot reported to a maintenance person in another state that he had several malfunctioning flight instruments, including the autopilot, horizontal situation indicator, and artificial horizon gyros. The pilot, who was not a mechanic, had maintenance personnel replace the right side artificial horizon gyro but did not have any other maintenance performed. The pilot was approved under an FAA exemption to operate the airplane as a single pilot; the exemption required that all equipment be operational, including a fully functioning autopilot, flight director, and gyroscopic flight instruments. Despite the malfunctioning instruments, the pilot chose to take off and fly in instrument meteorological conditions.
Weather and Flight Conditions
At the time of the loss of control, the airplane had just entered an area with supercooled large water droplets and severe icing, which would have affected the airplane's flying characteristics. At the same time, the air traffic controller provided the pilot with a radio frequency change, a change in assigned altitude, and a slight routing change. It is likely that these instructions increased the pilot's workload as the airplane began to rapidly accumulate structural icing. Because of the malfunctioning instruments, it is likely that the pilot became disoriented while attempting to maneuver and maintain control of the airplane as the ice accumulated, which led to a loss of control.