What was found
IAH - FLIGHT 3471, THE CREW REPORTED EXPERIENCING HEAVY VIBRATION FROM FONT OF AIRCRAFT AFTER BRINGING UP THE GEAR. THE AIRCRAFT LANDED AT IAH WITHOUT INCIDENT. THE AIRCRAFT WAS TEST FLOWN, AND FOUND THAT THE NOSE LANDING GEAR DOORS WERE NOT CLOSING. MAINTENANCE REMOVED AND REPLACED THE NLG PROXIMITY SWITCH, OPERATIONALLY CHECKED WITH NO DEFECTS, AND THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE.