Narrative:

Den approach had just given us a turn to a right downwind runway 16R at den. We were level at 13;000 ft and 250 KTS. Approach control gave us a descent to 11;000 ft and slow to 210 KTS. As we began the descent; we got a TA ('traffic; traffic'). The pilot not flying noticed a target at our 2 O'clock position moving right to left at 12;500 ft on TCAS. Shortly after the TA we got an RA ('monitor vertical speed'). The pilot flying disconnected the autopilot and followed the ADI guidance. The pilot not flying told approach control that we were responding to an RA. As I recall; the approach controller did not acknowledge the radio call. We then got another RA ('climb; climb') and the pilot flying responded by advancing the power and following the ADI guidance into a climb. When we got the 'climb' RA we were at 12;700 ft and according to the TCAS display the traffic was at our 12 O'clock position less than 1 mile 12;500 ft. Neither pilot made visual contact with the traffic. The pilot not flying made a second radio call to approach control that we were responding to a second RA. We got a 'clear of conflict' about the same time the approach controller acknowledged our radio call and told us tht the traffic was at our 6 O'clock position and 12;500 ft. The pilot flying re-engaged the autopilot and continued the descent to 11;000 ft. The pilot not flying told the approach controller 'that was way too close;' and the approach controller handed us off to the next approach controller. The pilot not flying asked the following approach controller if the traffic was in the class B airspace. The approach controller told us that the top of the class B is 12;000 ft it appeared that the traffic was VFR and skimming the top of the class B. In my opinion; if the flight crew had been advised of the VFR traffic; the situation would not have resulted in an RA. Bottom line; it is quite possible that the TCAS saved a hull loss.

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Original NASA ASRS Text

Title: B757 landing DEN with D01 experienced TCAS RA with unreported VFR traffic; ATC indicating traffic was above Class B and observed after the event.

Narrative: DEN Approach had just given us a turn to a right downwind Runway 16R at DEN. We were level at 13;000 FT and 250 KTS. Approach Control gave us a descent to 11;000 FT and slow to 210 KTS. As we began the descent; we got a TA ('traffic; traffic'). The Pilot Not Flying noticed a target at our 2 O'clock position moving right to left at 12;500 FT on TCAS. Shortly after the TA we got an RA ('monitor vertical speed'). The Pilot Flying disconnected the autopilot and followed the ADI guidance. The Pilot Not Flying told Approach Control that we were responding to an RA. As I recall; the Approach Controller did not acknowledge the radio call. We then got another RA ('climb; climb') and the Pilot Flying responded by advancing the power and following the ADI guidance into a climb. When we got the 'climb' RA we were at 12;700 FT and according to the TCAS display the traffic was at our 12 O'clock position less than 1 mile 12;500 FT. Neither pilot made visual contact with the traffic. The Pilot Not Flying made a second radio call to Approach Control that we were responding to a second RA. We got a 'clear of conflict' about the same time the Approach Controller acknowledged our radio call and told us tht the traffic was at our 6 O'clock position and 12;500 FT. The Pilot Flying re-engaged the autopilot and continued the descent to 11;000 FT. the Pilot Not Flying told the Approach Controller 'That was way too close;' and the Approach Controller handed us off to the next Approach Controller. The Pilot Not Flying asked the following Approach Controller if the traffic was in the Class B Airspace. The Approach Controller told us that the top of the Class B is 12;000 FT it appeared that the traffic was VFR and skimming the top of the Class B. In my opinion; if the flight crew had been advised of the VFR traffic; the situation would not have resulted in an RA. Bottom line; it is quite possible that the TCAS saved a hull loss.

Data retrieved from NASA's ASRS site as of May 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.