What was found
PDIS 668 32-30 3276 20MAR21 GSO ON APPROACH TO KGSO THE GEAR DID NOT EXTEND IN SYS 2. THERE WAS NO ECAM MESSAGE. THE ONLY INDICATION WE RECEIVED WERE THREE UNLK LIGHTS ON THE LANDING GEAR PANEL AND OVERHEAD PANEL. THERE WAS NO NOISE INDICATING GEAR MOVEMENT. WE DISCONTINUED THE APPROACH. FOUND A SAFE AREA TO WORK THE PROBLEM. WE TRIED SYS 1 AND HAD SOME INDICATIONS. NEVER IN EITHER POSITION DID WE GET THE SOUND OF GEAR OR GEAR DOORS MOVING. WE DECLARED AN EMERGENCY WITH ATC. TALKED WITH MAINTENANCE , OPS & GOC. AFTER SEVERAL MINUTES THE ECAM DIRECTED US TO LANDING GEAR GRAVITY EXTENSION CHECKLIST. WE ACCOMPLISHED THIS AND LANDED. SHGN 21MAR21 05:14 GSO RMVD AND RPLD LANDING GEAR SELECTOR VALVE 3GA AS PER AMM 32-31-12-04. NEEDS LK CKED AND TESTED AS PER AMM 32-31-12-06. FACT 21MAR21 23:04 GSO COMPLIED WITH GEAR SWING IN BOTH POSTION 1 AND 2 PER MM 07-11-00-00 (JACKING OF AIRCRAFT) AND 32-31-00-05 ( NORMAL EXTENSION AND RETRACTION ) NO DEFECTS NOTED ALL INDICATIONS SATISFACTORY A/C OK FOR SERVICE.