What was found
SHORTLY AFTER ENGAGING AUTOPILOT, STAB CH1 STATUS MESSAGE DISPLAYED FOLLOWED BY AN AP PITCH TRIM CAUTION AND STAB TRIM RUNAWAY AURAL WARNING. FOLLOWED QRC AND QRH FOR RUNAWAY AND THE MESSAGES RESULTING IN FLYING AND LANDING WITH STAB TRIM AND MACH TRIM DISENGAGED. (FLIGHT 6255) REFERENCE AML 1878489 MDC SHOWS B1 CODES OF 007959, 060017, & 007953. FDR DATA SHOWS THAT AIRCRAFT NEVER HAD AN UNCOMMANDED VERTICAL DEVIATION DUE TO UNCOMMANDED STAB TRIM MOVEMENT. THIS WAS ALSO RELAYED TO THE MECHS FROM FLT CREW AS THEY NEVER FELT ANY UNCOMMANDED VERTICAL MOVEMENT OF ACFT DURING FLT. FOLLOWED FIM 27-42-03 & R & R CHANNEL 1 HSTA MOTOR IAW AMM 27-42-03. PERFORMED SPOST 1 & SPOST 2. STAB TRIM SYSTEM OPS CHECKS GOOD.