DFW TWR ALERT MD88 FLC WHEN OBSERVED XING INTENDED FINAL APCH COURSE; CONFLICTING WITH AN ATR.

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WE ARRIVED AT DFW FROM THE SW. THE VISIBILITY WAS SPECTACULAR AND THERE WERE A FEW PUFFY CLOUDS AROUND 8000 FT. WE HAD THE ARPT IN SIGHT FROM 25 MI OUT. APCH CTL ASKED US TO EXPEDITE DSCNT ON DOWNWIND AND EXPECT A SHORT APCH TO RWY 18R. WE RPTED THE ARPT IN SIGHT AND THEY GAVE US A TURN TO 090 DEGS AND CLRED US FOR THE VISUAL; 180 KTS OR GREATER TO THE MARKER AND TURNED US OVER TO TWR. WE WERE BACKING UP THE VISUAL WITH THE ILS AND BOTH HAD THE MAP MODE DISPLAYED ON THE NAV DISPLAY. I WAS FLYING FROM THE L SEAT AND PERFORMING THE R TURN TO BASE AND FINAL. I HAVE BEEN FLYING OUT OF DFW FOR 13 YRS AND AM INTIMATELY FAMILIAR WITH THE ARPT ENVIRONMENT. BUT; SOMEHOW; I BECAME FOCUSED ON RWY 17R INSTEAD OF RWY 18R. I AM ABSOLUTELY MYSTIFIED AT HOW THIS HAPPENED. THE ONLY FACTOR I CAN IMAGINE IS THAT THE W COMPLEX OF RWYS WAS BATHED IN SHADOWS FROM THE HIGHER CLOUDS AND THE SUN WAS SHINING BRIGHTLY ON THE E COMPLEX; MAKING THEM MUCH MORE PROMINENTLY VISIBLE. THE FO WAS APPARENTLY FOCUSED ON THE SAME THING AND DID NOT NOTICE ME SLIP RIGHT ON THROUGH THE LOC COURSE FOR RWY 18R. WE WERE WITHIN A MI OF BEING LINED UP ON RWY 17R BEFORE THE TWR CTLR QUESTIONED OUR RWY ALIGNMENT. WE HAD PLENTY OF ROOM TO CORRECT BACK FOR A NORMAL LNDG ON RWY 18R. BUT I WAS IN A STATE OF SHOCK AND MORTIFIED WITH EMBARRASSMENT FROM MAKING SUCH A MISTAKE. I WAS GRATEFUL THAT THE TWR CTLR GAVE US THE HEADS UP AND SAVED US. I HAVE OFTEN WONDERED HOW SOMEONE COULD LAND AT THE WRONG ARPT OR RWY. BUT; I NEARLY DID IT; IN BROAD DAYLIGHT WITH PERFECT VISIBILITY. SUPPLEMENTAL INFO FROM ACN 514584: WE WERE ON THE LAST LEG OF A 4 DAY TRIP FRAUGHT WITH WX AND OPERATIONAL CHALLENGES. APCH CLRED US FOR A VISUAL APCH AT ABOUT 7 MI ON THE BASE LEG AND SWITCHED US TO TWR AS WE STARTED A TURN TO DOGLEG. I REFED AN RJ ON SHORT FINAL THEN SWITCHED THE RADIO AND RPTED IN TO TWR. I TURNED MY ATTN BACK INSIDE AND CHKED THE NAV RADIOS; TUNED TO THE RWY 18R ILS AND THEN SET THE APPROPRIATE GND FREQ IN THE OTHER VHF FOR OUR TAXI. WHEN I NEXT LOOKED OUTSIDE; SOMETHING SEEMED AMISS. I NOTICED A NORMALLY UNSEEN GOLF COURSE GOING BELOW US; AND AT THAT MOMENT WE RECEIVED A TA FROM THE TCASII. I STARTED SEARCHING BELOW AND AHEAD OF OUR ACFT; THINKING IT MIGHT BE A LIGHT ACFT; AND WAS SURPRISED TO FIND AN ATR ABOVE AND TO OUR L. I NOW REALIZED WHAT LOOKED WRONG! WE HAD FLOWN THROUGH THE W (RWY 18L/R) COMPLEX AND WERE ON A DOGLEG FOR RWY 17R. I DON'T BELIEVE WE CAME CLOSER THAN 500 FT TO THE RWY 17R CTRLINE; OR WITHIN 1/2 MI OF THE ATR. THIS HAPPENED AS THE RESULT OF SEVERAL FACTORS; CHIEF AMONG THEM WAS MY FAILURE TO MENTALLY FLY THE ACFT. I DISTRACTED MYSELF INSIDE DOING UNNECESSARY FUNCTIONS AND DIDN'T BACK UP THE PF. I ALSO DIDN'T USE THE INFO FROM THE ILS THAT I SO CAREFULLY TUNED; INSTEAD USED THE CAPT'S PURE VISUAL APCH. ALSO; THE DAY PRIOR TO THIS WE FLEW A SIMILAR APCH TO DFW AND WERE CHANGED FROM RWY 18R TO RWY 17C WHILE ON BASE LEG; ALMOST AT THE SAME POS WE INITIATED TODAY'S VISUAL. THAT MAY HAVE REINFORCED THE VISUAL PICTURE THE CAPT HAD AND HELPED LEAD HIM TO FOCUS ON THE WRONG RWY. MY COMPANY'S PROCS AND TRAINING ARE MORE THAN ADEQUATE TO COVER THIS PROB -- IT WAS CAUSED BY THE SERIES OF EVENTS I DESCRIBED AND MY FAILURE TO STAY IN THE LOOP ON THE ARR AND LNDG.