What was found
CAUTION MESSAGE INFLIGHT, STAB TRIM, MACH TRIM, AUTOPILOT TRIM NOSE DOWN. PITCH STUCK AT 6.0. WHEN AUTOPILOT DISENGAGED AT 1000` AGL ALL MESSAGES DISAPPEARED PITCH TRIM WAS OPERATIONAL. HSTCU FAIL, REMOVED AND REPLACED HSTCU IAW 27-41-01, NO FAULTS NOTED. OPS CHECK GOOD. (M)