UNSAFE GEAR INDICATION ON APCH.

Narrative

ON FINAL FOR VISUAL APCH RWY 28R PIT; LOWERED GEAR AT NORMAL CONFIGN POINT AND DID NOT GET A GREEN GEAR DOWN LIGHT FOR R MAIN GEAR. L MAIN GEAR AND NOSE GEAR GREEN LIGHTS WERE ILLUMINATED. NO RED GEAR UNSAFE LIGHTS WERE ILLUMINATED. SEQUENCE OF GEAR LIGHTS APPEARED NORMAL DURING EXTENSION. EXECUTED GAR TO ANALYZE SIT AND RUN CHKLISTS. TWR NOTED THAT ALL GEAR APPEARED TO BE NORMALLY EXTENDED. WE HAD PLENTY OF FUEL AND THE WX WAS EXCELLENT. WE STAYED CONFIGURED AT GEAR DOWN AND 20 DEGS FLAPS AND WERE VECTORED BY APCH CTL AS WE RAN ALL APPROPRIATE CHKLISTS THE FO CONFIRMED THE R MAIN GEAR WAS IN THE DOWN AND LOCKED POS THROUGH THE PERISCOPE VIEWER. ACCOMPLISHING ALL CHKLIST PROCS RESULTED IN NO CHANGES TO ACFT STATUS. DISPATCH WAS NOTIFIED. AS A PRECAUTION I ADVISED OUR LEAD FLT ATTENDANT TO BRIEF THE PAX ON EMER LNDG PROC AND ASKED THE TWR TO HAVE THE EMER VEHICLES STANDING BY. THE ACFT WAS FULLY CONFIGURED FOR LNDG. THE SUBSEQUENT APCH TOUCHDOWN AND ROLLOUT WERE UNEVENTFUL. AFTER CLRING THE RWY AT THE HIGH SPD TURNOFF; THE RESPONSE TEAM PINNED THE GEAR AND WE TAXIED TO THE GATE WITHOUT INCIDENT. ALL CREW MEMBERS PERFORMED THEIR DUTIES IN AN OUTSTANDING; PROFESSIONAL MANNER. THERE WERE NO PAX COMPLAINTS WE WERE AWARE OF; AND NUMEROUS COMPLIMENTS WERE HEARD FROM THE PAX. A SENSING MALFUNCTION OF SOME TYPE WAS SUSPECTED.