B737-300 CREW HAS UNSAFE GEAR INDICATION AND LANDS SAFELY.

Narrative

WE WERE ON APCH TO RWY AT ZZZ. WHEN THE LNDG GEAR WAS SELECTED DOWN; THE L MAIN GEAR DID NOT SHOW DOWN AND LOCKED (THE RED GEAR UNSAFE LIGHT WAS ILLUMINATED AND THERE WAS NO GREEN INDICATION ON THE L MAIN GEAR). WE INFORMED THE TWR AND CONTINUED THE APCH SO THAT THE TWR COULD LOOK AT THE GEAR AND THEN MAKE A MISSED APCH. THE TWR SAID THE GEAR APPEARED TO BE DOWN. WHILE BEING VECTORED WE RAN THE UNSAFE GEAR/MANUAL EXTENSION CHKLIST AND WAS UNABLE TO MAKE ANY CHANGES TO OUR INDICATIONS. WE INFORMED THE FLT ATTENDANTS OF WHAT WAS GOING ON AND HAD THEM CHK THE VIEWFINDER FOR THE L MAIN LNDG GEAR. THEY WERE NOT SURE IF THE GEAR WAS DOWN AND LOCKED. THE A FLT ATTENDANT CAME TO THE COCKPIT AND I WENT TO LOOK THROUGH THE VIEWFINDER AND FOUND THAT THE GEAR APPEARED TO BE DOWN AND LOCKED. AFTER I RETURNED TO THE COCKPIT THE CAPT TOLD ME HE HAD TALKED TO THE FLT ATTENDANT ABOUT A POSSIBLE EVAC. DURING THIS WHOLE TIME HE HAD ALSO BEEN TALKING WITH OPS AND DISPATCH ABOUT OUR SITUATION AND WHAT TO DO. AFTER FINDING THAT THE GEAR APPEARED TO BE DOWN AND LOCKED WE DECIDED TO MAKE ANOTHER LOW APCH AND LET THE TWR LOOK AT THE GEAR AGAIN. THIS TIME THE ZZZ ARPT POLICE SHINED A FLOOD LIGHT ON THE GEAR AND MADE IT MORE VISIBLE. ONCE AGAIN IT WAS FOUND TO BE DOWN. WE COORDINATED WITH THE FLT ATTENDANTS TO PREPARE THE CABIN FOR AN EMER LNDG AND A POSSIBLE EVAC (WORSE CASE SCENARIO). IN THE MEANTIME WE WERE BEING VECTORED BACK AROUND FOR ANOTHER APCH TO RWY. THE CAPT AND I ACCOMPLISHED THE FIRST 3 STEPS OF THE PARTIAL OR GEAR UP LNDG CHKLIST AND REVIEWED THE REST. WE ALSO REVIEWED THE EMER EVAC CHKLIST. WE DECLARED AN EMER; REQUESTED THE CRASH; FIRE AND RESCUE TRUCKS; AND INFORMED APCH THAT WE WERE READY TO FLY THE APCH AND LAND. WHEN THE FLT ATTENDANTS HAD THE CABIN PREPARED; WE STARTED THE APCH TO RWY. THE APCH WAS FLOWN FLAPS 40 DEGS; AN UNEVENTFUL NORMAL LNDG WAS MADE AND THE ACFT WAS BROUGHT TO A COMPLETE STOP ON THE RWY. AFTER THE ACFT WAS INSPECTED BY THE RESCUE PERSONNEL; THE R ENG WAS SHUT DOWN; I THREW THE GEAR PINS OUT MY WINDOW TO A COMPANY OPS AGENT AND ALL 3 LNDG GEAR WERE PINNED. AFTER RECEIVING CLRNC TO TAXI TO THE GATE; WE DID SO WITH NO FURTHER INCIDENT. AFTER ARRIVING AT THE GATE THE CAPT CONTACTED DISPATCH; THE CHIEF PLT AND MADE AN ENTRY INTO THE LOGBOOK. AFTER ALL OF THE PAX WERE DEPLANED; THE ACFT WAS SHUT DOWN AND WE WENT TO THE HOTEL. THIS WAS THE FIRST TIME I HAD EVER LOOKED THROUGH THE VIEWFINDER AT THE LNDG GEAR DOWN AND LOCKED INDICATIONS. I THINK IT WOULD BE BENEFICIAL TO EVERYONE IF THIS COULD BE DONE DURING TRAINING SO THE CREW MEMBERS WILL BE MORE FAMILIAR WITH WHAT THEY ARE LOOKING FOR. I WAS ABLE TO SEE WHAT I NEEDED TO SEE; BUT IT WOULD HAVE BEEN NICE TO HAVE SEEN IT BEFORE INSTEAD OF THE FIRST TIME BEING DURING AN EMER.