What was found
ENROUTE, AUTOPILOT KICKED OFF MULTIPLE TIMES DURING FLT, AND HAD AN OVERSPEED WARNING DUE TO LOSS OF MACH TRIM, MASTER CAUTION FOR LOSS OF PRIMARY STAB TRIM. ELECTED TO REDIRECT & PROCEED TO SERVICE CENTER. DURING REMAINDER OF FLT, PITCH CONTROL PRESSURE INCREASED & ENGAGED SECONDARY TRIM BUT WHEN SECONDARY TRIM SWITCH HELD, RECEIVED A MASTER CAUTION FOR FAILURE OF SECONDARY TRIM. DECLARED AN EMERGENCY & LANDED UNEVENTFULLY. POST-FLT EVALUATION DETERMINED STAB TRIM SYS TO BE FULLY OPERATIONAL, BOTH ON PRIMARY & SECONDARY. FURTHER INVESTIGATION NOT ABLE TO DETERMINE CAUSE OF FAILURE, ACTUATOR ASSY REMOVED FOR FURTHER EVALUATION. TROUBLESHOT ACTUATOR. AFTER A 3 HR COLD-SOAK AT -65 DEG F, ACTUATOR FOUND TO BE NON-FUNCTIONING. FOUND MICROPROCESSOR, WHEN FROZEN, PREVENTED CONTROLLER FROM FUNCTIONING CORRECTLY. MICROPROCESSORS REMOVED & RETURNED TO SUPPLIER FOR EVALUATION. OPEN