FLC OF AN MD SUPER 80 FLEW THROUGH THE FINAL LOC COURSE FOR THE PARALLEL RWY TO WHICH THEY WERE MAKING A VISUAL APCH AND ANOTHER ACFT WAS MAKING A VISUAL TO THE OTHER PARALLEL RWY. IN ADDITION; THE CREW FAILED TO RPT THAT THEY HAD LOST VISUAL SIGHTING OF THE ARPT WHEN TURNING BASE TO FINAL.

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ARPT WX WAS CLR. WE HAD POSITIVELY IDENTED THE DEST ARPT 20 NM OUT. CTR CLRED US TO THE VOR (CO-LOCATED WITH THE ARPT) AND ASSIGNED US A HDG TO FLY. XING THE VORTAC WE WERE VECTORED TO A DOWNWIND AND THEN GIVEN A CLRNC FOR A PUBLISHED VISUAL APCH. ON BASE WE WERE ASSIGNED THE L RWY AND A COMMUTER ACFT WAS ASSIGNED THE R RWY OF PARALLEL RWYS. I WAS THE PNF AND POSITIVELY IDENTED THE COMMUTER ACFT ALSO ON A BASE LEG FOR THE R RWY. WE HAD EXPECTED THE R RWY WHICH WAS THE NORMAL PROC FOR THIS; OUR HOME ARPT. THE R RWY IS SERVED BY AN ILS WHICH WAS OPERATING. THE L RWY IS NOT SERVED BY AN ILS. WHEN WE WERE CLRED FOR THE L RWY I DESELECTED THE ILS FREQ ON MY SIDE BECAUSE WE WERE NOT CLRED FOR THE R RWY BUT FOR THE L. I HAD MY EYES ON THE COMMUTER ACFT MOST OF THE TIME; I GLANCED OVER TO THE CAPT'S INSTS AND NOTICED OUR ACFT HAD FLOWN THROUGH THE ILS LOC FOR THE R SIDE. I WAS CONFIRMING THE CAPT STILL HAD THE R SIDE LOC FREQ TUNED AND I HAD CORRECTLY INTERPRETED WHAT I WAS SEEING; WHEN THE CAPT SAID THAT WE HAD FLOWN THROUGH THE LOC AND TURNED BACK TO THE L. WHEN WE TURNED BASE TO FINAL; WE LOST THE ARPT VISUALLY (TOTALLY UNEXPECTEDLY) IN A COMBINATION OF HAZE AND GLARE OFF THE LATE AFTERNOON SUN. BOTH OF US COMMENTED ON THE SUDDEN DIFFICULTY WE ENCOUNTERED LOCATING THE ARPT. AS THE CAPT WAS TURNING BACK TO THE L; THE APCH CTLR ASKED US IF WE WERE S-TURNING ON FINAL. THEN HE TOLD US TO BE SURE WE CLR ANY SUCH MANEUVERS WITH HIM PRIOR. WE HAD TFC OFF OUR R SIDE (I HAD THIS ACFT IN SIGHT DURING THIS EVENT). THE COMMUTER PLT ALSO ACKNOWLEDGED HE HAD US IN SIGHT. IN RETROSPECT; GIVEN THE EXCELLENT WX; I DO NOT THINK I COULD HAVE ANTICIPATED LOSING VISUAL CONTACT WITH THE ARPT. HOWEVER; ONCE WE DID LOSE VISUAL CONTACT WE SHOULD HAVE TOLD THE APCH CTLR. TCASII DID ACTIVATE GIVING US A TA -- TFC WAS ALREADY IN SIGHT.