What was found
DECLARED AN EMERGENCY AND RETURNED TO FIELD DUE TO ACFT FLEW THROUGH PRESELECTED ALT AND WAS UNABLE TO CORRECT UNTIL AUTOPILOT WAS DISENGAGED. MX DEBRIEFED THE FLIGHT AND VIEWED THE AFCS FLIGHT FAULTS. NO FAULTS NOTED. PREFORMED THE AFCS SYSTEM TEST AND FMS TEST. DURING THE FMS INTERFACE TEST #1 FMS WENT BLANK AND TEST WAS NOT ABLE TO BE PERFORMED. RESET ACFT POWER AND FMS SYSTEM TEST WAS NORMAL. REPOSITIONED THE #1 AND #2 FMS NAV COMPUTERS. RETESTED THE AUTOPILOT AND TESTED THE #1, #2 AND #3 FMS WITH NO DEFECTS NOTED