Crash of a Mitsubishi MU-2B-35 Marquise in Austin: 1 killed

About 6 minutes after takeoff, at 2138:31 cdt, the pilot reported level at 9,000 feet msl. At 2140:17, he transmitted that he had trouble and said he could not control or disconnect the autopilot (a/p) which was causing the aircraft to descend. At 2141:14, he stated he was descending at 6,000 feet/min. Another company pilot in another aircraft asked if he could find the breaker, meaning the a/p circuit breaker. At 2141:27, the pilot of N8CC replied, 'call you back.' Seconds later, radio and radar contact with N8CC were lost. A search was initiated, but the aircraft was not found until the following morning. An exam revealed the aircraft impacted in a steep, nose down, inverted attitude while at high speed; much of the wreckage was buried. No preimpact part failure/malfunction was found. With the a/p engaged, back pressure on the control column would have caused the a/p to trim nose down. Subsequently, the manufacturer issued a precautionary advisory to all MU-2 owner/operators regarding proper operation of the a/p and the various ways in which it can be disengaged. The pilot, sole on board, was killed.