Narrative:

We were being vectored for a left base to final visual for runway 17C. We had a TA on TCASII, followed shortly after with a 'descend' RA in excess of 1500 FPM. We saw visually an aircraft heading directly for us. He appeared to be on a right base for the same runway. We were on the left base at the same altitude. We responded to the RA with a descent to below 2500 ft. We advised the controller, who told us that the offending aircraft had overshot final. We presume he was to be on runway 18R. While the TCASII system worked, in the interest of safety, I do not believe aircraft should be on opposing bases at the same altitude with conflicting flight paths. Had TCASII been on MEL on both aircraft, only a lucky look ahead as both aircraft were looking for the runway would have averted at minimum a near miss.

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Original NASA ASRS Text

Title: MD80 CREW HAD TCASII RA IN DFW CLASS B AIRSPACE.

Narrative: WE WERE BEING VECTORED FOR A L BASE TO FINAL VISUAL FOR RWY 17C. WE HAD A TA ON TCASII, FOLLOWED SHORTLY AFTER WITH A 'DSND' RA IN EXCESS OF 1500 FPM. WE SAW VISUALLY AN ACFT HDG DIRECTLY FOR US. HE APPEARED TO BE ON A R BASE FOR THE SAME RWY. WE WERE ON THE L BASE AT THE SAME ALT. WE RESPONDED TO THE RA WITH A DSCNT TO BELOW 2500 FT. WE ADVISED THE CTLR, WHO TOLD US THAT THE OFFENDING ACFT HAD OVERSHOT FINAL. WE PRESUME HE WAS TO BE ON RWY 18R. WHILE THE TCASII SYS WORKED, IN THE INTEREST OF SAFETY, I DO NOT BELIEVE ACFT SHOULD BE ON OPPOSING BASES AT THE SAME ALT WITH CONFLICTING FLT PATHS. HAD TCASII BEEN ON MEL ON BOTH ACFT, ONLY A LUCKY LOOK AHEAD AS BOTH ACFT WERE LOOKING FOR THE RWY WOULD HAVE AVERTED AT MINIMUM A NEAR MISS.

Data retrieved from NASA's ASRS site as of July 2007 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.