Narrative:

Denver approach had us on a vector towards the airport. The controller had just given us a clearance for a visual approach to 28L when the TCASII gave an aural warning of 'traffic.' the TCASII display showed traffic at 2 O'clock, 4 mi, in yellow. I visually acquired traffic level with us and aimed right at us. I told the captain that I had traffic in sight coming right at us and level. Simultaneously, the TCASII gave an RA telling us to descend. The captain started a descent and I kept an eye on the traffic. The traffic was an air carrier large transport aircraft and he passed about 1/2 mi behind us at what I estimated was the same altitude we were at. I immediately told approach control that we had taken evasive action based on a TCASII RA. He replied that the traffic had us in sight. We were never told about this traffic until I mentioned we had taken evasive action. We should have been told ahead of time. The traffic in question should not have come as close as it did to us even if it had us in sight. The captain called approach control after landing and was told on the telephone that they admitted having screwed up by not pointing the traffic to us earlier.

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Original NASA ASRS Text

Title: CAPT OF ACR LGT ACFT TOOK EVASIVE ACTION IN RESPONDING TO A TCASII RA RESULTING IN A DEV FROM ASSIGNED ALT.

Narrative: DENVER APCH HAD US ON A VECTOR TOWARDS THE ARPT. THE CTLR HAD JUST GIVEN US A CLRNC FOR A VISUAL APCH TO 28L WHEN THE TCASII GAVE AN AURAL WARNING OF 'TFC.' THE TCASII DISPLAY SHOWED TFC AT 2 O'CLOCK, 4 MI, IN YELLOW. I VISUALLY ACQUIRED TFC LEVEL WITH US AND AIMED RIGHT AT US. I TOLD THE CAPT THAT I HAD TFC IN SIGHT COMING RIGHT AT US AND LEVEL. SIMULTANEOUSLY, THE TCASII GAVE AN RA TELLING US TO DSND. THE CAPT STARTED A DSCNT AND I KEPT AN EYE ON THE TFC. THE TFC WAS AN ACR LGT ACFT AND HE PASSED ABOUT 1/2 MI BEHIND US AT WHAT I ESTIMATED WAS THE SAME ALT WE WERE AT. I IMMEDIATELY TOLD APCH CTL THAT WE HAD TAKEN EVASIVE ACTION BASED ON A TCASII RA. HE REPLIED THAT THE TFC HAD US IN SIGHT. WE WERE NEVER TOLD ABOUT THIS TFC UNTIL I MENTIONED WE HAD TAKEN EVASIVE ACTION. WE SHOULD HAVE BEEN TOLD AHEAD OF TIME. THE TFC IN QUESTION SHOULD NOT HAVE COME AS CLOSE AS IT DID TO US EVEN IF IT HAD US IN SIGHT. THE CAPT CALLED APCH CTL AFTER LNDG AND WAS TOLD ON THE TELEPHONE THAT THEY ADMITTED HAVING SCREWED UP BY NOT POINTING THE TFC TO US EARLIER.

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.