Narrative:

When on the approach into runway 17C at dfw; we were on a 320 degree heading when we received a TCAS alert (TA). It was traffic landing on runway 17L. At the time of the alert; we were 4400 ft and descending to 4000 ft. Problem was that the TCAS showed the traffic to be only -1100 ft below us. So I realized that if I continued the descent to 4000 ft then we would only have 700 ft separation. I slowed the descent by manually flying the plane to the point of almost leveling off. I looked out my 'dv' window and located the traffic which was going right beneath us on approximately 220-240 degree heading. I had the aircraft in sight for just a short period when it was on the right side of the aircraft; but lost it when they crossed right below us. I told the captain that I saw the traffic. I meant I had it in sight for TCAS purposes not for visual approach purposes. About that time ATC gave us a heading 270 degrees or 280 degrees. The captain acknowledged the clearance and also told ATC we had traffic in sight. They then cleared us for the visual approach when I had really no idea where the other aircraft was (between the 2 diverging courses and the fact that I was on the right side of the aircraft with traffic going away from us). I was being cautious when I decided to turn in towards the runway 17C because I wasn't really sure where the aircraft was except for the TCAS display. When I started the turn for runway 17C; the localizer was not even 'alive' yet. Between turning slowly and looking for traffic; our turn was complete when we were approximately centerline for runway 17R. A few seconds after starting our turn. Approach asked us if we had started our turn yet and by that point we were 50 degrees into our turn from west.

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Original NASA ASRS Text

Title: EMB140 FO RPTS OVERSHOOTING RWY 17C ONTO RWY 17R CTRLINE DURING VISUAL APCH TO DFW.

Narrative: WHEN ON THE APCH INTO RWY 17C AT DFW; WE WERE ON A 320 DEG HDG WHEN WE RECEIVED A TCAS ALERT (TA). IT WAS TFC LNDG ON RWY 17L. AT THE TIME OF THE ALERT; WE WERE 4400 FT AND DSNDING TO 4000 FT. PROB WAS THAT THE TCAS SHOWED THE TFC TO BE ONLY -1100 FT BELOW US. SO I REALIZED THAT IF I CONTINUED THE DSCNT TO 4000 FT THEN WE WOULD ONLY HAVE 700 FT SEPARATION. I SLOWED THE DSCNT BY MANUALLY FLYING THE PLANE TO THE POINT OF ALMOST LEVELING OFF. I LOOKED OUT MY 'DV' WINDOW AND LOCATED THE TFC WHICH WAS GOING RIGHT BENEATH US ON APPROX 220-240 DEG HDG. I HAD THE ACFT IN SIGHT FOR JUST A SHORT PERIOD WHEN IT WAS ON THE R SIDE OF THE ACFT; BUT LOST IT WHEN THEY CROSSED RIGHT BELOW US. I TOLD THE CAPT THAT I SAW THE TFC. I MEANT I HAD IT IN SIGHT FOR TCAS PURPOSES NOT FOR VISUAL APCH PURPOSES. ABOUT THAT TIME ATC GAVE US A HDG 270 DEGS OR 280 DEGS. THE CAPT ACKNOWLEDGED THE CLRNC AND ALSO TOLD ATC WE HAD TFC IN SIGHT. THEY THEN CLRED US FOR THE VISUAL APCH WHEN I HAD REALLY NO IDEA WHERE THE OTHER ACFT WAS (BTWN THE 2 DIVERGING COURSES AND THE FACT THAT I WAS ON THE R SIDE OF THE ACFT WITH TFC GOING AWAY FROM US). I WAS BEING CAUTIOUS WHEN I DECIDED TO TURN IN TOWARDS THE RWY 17C BECAUSE I WASN'T REALLY SURE WHERE THE ACFT WAS EXCEPT FOR THE TCAS DISPLAY. WHEN I STARTED THE TURN FOR RWY 17C; THE LOC WAS NOT EVEN 'ALIVE' YET. BTWN TURNING SLOWLY AND LOOKING FOR TFC; OUR TURN WAS COMPLETE WHEN WE WERE APPROX CTRLINE FOR RWY 17R. A FEW SECONDS AFTER STARTING OUR TURN. APCH ASKED US IF WE HAD STARTED OUR TURN YET AND BY THAT POINT WE WERE 50 DEGS INTO OUR TURN FROM W.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.