What was found
CLE - FLT 1255 - WHILE CRUISING AT FL 220 EN ROUTE FROM BDL TO CLE AND WITH AUTOPILOT ENGAGED IN 'B' MODE, THE AIRCRAFT MADE AN ABRUPT BANK TO THE RIGHT. THE AUTOPILOT WAS DISCONNECTED AND THE AIRCRAFT FLEW NORMAL FOR REMAINDER OF FLIGHT. THE 'B' AUTOPILOT WAS PLACARDED INOPERATIVE. THE SDR WILL REMAIN OPEN FOR PART INFORMATION PENDING CORRECTIVE ACTION/INVESTIGATION. SUPPLEMENT - INVESTIGATION REVEALED THE AIR DATA COMPUTER WAS AT FAULT. SHOP TEAR DOWN REVEALED WINDINGS IN TRANSFORMER HAD OPENED UP. (X)