Summary
On a dark night, a pilot flying aircraft N8CC reported level at 9,000 feet mean sea level about six minutes after departure. Approximately two minutes later, he transmitted that he was experiencing trouble, unable to control or disengage the autopilot, which was causing the aircraft to descend. He stated he was descending at 6,000 feet per minute. Another company pilot in another aircraft suggested locating the autopilot circuit breaker. The pilot of N8CC replied, "call you back," after which radio and radar contact were lost. A search was initiated, and the wreckage was discovered the following morning.
Investigation
Examination of the accident site indicated that the aircraft had impacted in a steep, nose-down, inverted attitude at high speed, with much of the wreckage buried. No preimpact part failure or malfunction was found. It was noted that with the autopilot engaged, back pressure on the control column would have caused the autopilot to trim the aircraft nose-down. Subsequently, the manufacturer issued a precautionary advisory to all MU-2 owner/operators regarding proper operation of the autopilot and the various ways to disengage it. The pilot, who was the sole occupant, was killed.
Probable Cause
The official probable cause findings listed two occurrences. Occurrence #1: Loss of Control in Flight during cruise. Contributing factors included dark night, undetermined autopilot/flight director issues, inadequate emergency procedure by the pilot, and the pilot's lack of familiarity with the aircraft. The descent was uncontrolled. Occurrence #2: In Flight Collision with Terrain/Water during uncontrolled descent.