AN ACR A320 FLC HAD AN UNSAFE INDICATION ON THE L MAIN GEAR AND ALTHOUGH THEY ACCOMPLISHED THE OPERATIONAL PROCS SEVERAL TIMES THE GEAR DID NOT INDICATE DOWN AND LOCKED UNTIL THE ACFT WAS ON FINAL APCH FOR LNDG.

Narrative

UPON EXTENDING THE LNDG GEAR; THE L MAIN GEAR INDICATOR WAS RED; UNLOCKED AND A RED INDICATION OF THE L MAIN GEAR INDICATOR ON THE WHEELS PAGE ON THE LOWER ECAM WAS ALSO PRESENT. CAPT WAS FLYING AND TOOK OVER COM AND INSTRUCTED ME TO GO THROUGH AIRBUS 320 COMPANY OPERATIONAL PROCS. RECYCLED LNDG GEAR WITH UNSUCCESSFUL RESULTS. CALLED COMPANY MAINT FOR ASSISTANCE. NO DIFFERENT PROCS WERE OFFERED. EMER EXTENDED THE LNDG GEAR WITH NO CHANGE IN STATUS. BRIEFED THE CABIN CREW; DECLARED AN EMER WITH ATC. PERFORMED THE EMER LNDG PROCS. AFTER ALL CHKLIST WERE PERFORMED AND THE CABIN WAS READY; AN APCH TO RWY 27 WAS PERFORMED. AT THE FINAL APCH FIX THE LNDG CHKLIST WAS COMPLETED; AND AT THAT TIME THE INDICATORS READ ALL 3 GREEN GEAR DOWN. THE CAPT MADE A PA INFORMING THE PAX AND CREW THAT WE SHOULD HAVE A NORMAL LNDG; THAT THE INDICATIONS WERE NORMAL. BRIEFED THE FLT ATTENDANTS THAT A NORMAL LNDG WOULD BE MADE AND THAT THE BRIEFED CALLOUT (BRACE FOR IMPACT) WOULD NOT BE MADE. THE LNDG WAS SMOOTH ON THE R GEAR THEN THE L TOUCHDOWN WAS UNEVENTFUL. I ASKED THE CAPT IF HE HAD NOSEWHEEL STEERING AND HE DID. HE INSTRUCTED ME TO CANCEL THE EMER EQUIP AND NOTIFY ATC THAT WE WOULD BE ABLE TO TAXI UNDER OUR OWN PWR TO THE GATE. INITIALLY THE PROB WAS ENCOUNTERED AT 210 KTS THEN THE PROCS WERE PERFORMED WHILE AT 185 KTS. THE ALL GREEN GEAR DOWN INDICATION OCCURRED AT APPROX 140 KTS. A FAULTY LNDG GEAR CTL AND INTERFACE UNIT WAS REPLACED AND THE PROB WAS CORRECTED BY MAINT ON THE GND IN SAN DIEGO.