What was found
THE CREW REPORTED AT CRUISE AT LEVEL 17000`, THEY DETECTED A THUMPING UNDER THE PILOTS FEET FOR 20 SECONDS, THEN THE NOSE GEAR UNLOCK LIGHT ON GEAR PANEL NR 1 CAME ON FOR 15 SECONDS THEN ALL SYMPTOMS QUIT. LIGHT & NOISE RETURNED 1 MORE TIME BRIEFLY. THE ACFT LANDED WITHOUT INCIDENT. THE ACFT WAS REMOVED FROM SERVICE. R & R THE NLG UPLOCK BOX LIMIT SWITCH IAW ATR JIC 32-61-00 RAI 10010. THE OPS CHECK WAS GOOD. THE ACFT WAS RETURNED TO SERVICE.