Narrative:

On descent into las 8000 ft, 250 KTS, we reported when asked that we had the airport in sight. We were then cleared for the visual approach for runway 25L at las. The first officer was the PF. The aircraft was on autoplt in LNAV on centerline fix for runway 25L and flight level change. I noticed a target on TCASII about 1-2 O'clock with no altitude readout. ATC also reported a target at 12-1 O'clock with no altitude report. At this point I asked the first officer to level off, which he did immediately by hitting altitude hold. I was assuming the target was below us since there is a small airport in the vicinity, and we were just near the edge of class B airspace. I would say about 3 seconds after we stopped the descent, the RA function of the TCASII commanded a climb. I immediately disconnected the autoplt and started to climb. When the TCASII reported clear of traffic, the first officer resumed control. I looked out the left window and saw a light twin pass from right to left below us. I reported the RA to ATC. At this point we were high on the glide path and needed the gear and speed brake to get back on glide path. A normal landing was made. I think our speed 240-250 KTS and descending was a factor in the TCASII RA warning.

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Original NASA ASRS Text

Title: NMAC BTWN AN LGT DSNDING FOR A VISUAL APCH AND A LIGHT TWIN CLBING 15 MI FROM THE ARPT.

Narrative: ON DSCNT INTO LAS 8000 FT, 250 KTS, WE RPTED WHEN ASKED THAT WE HAD THE ARPT IN SIGHT. WE WERE THEN CLRED FOR THE VISUAL APCH FOR RWY 25L AT LAS. THE FO WAS THE PF. THE ACFT WAS ON AUTOPLT IN LNAV ON CTRLINE FIX FOR RWY 25L AND FLT LEVEL CHANGE. I NOTICED A TARGET ON TCASII ABOUT 1-2 O'CLOCK WITH NO ALT READOUT. ATC ALSO RPTED A TARGET AT 12-1 O'CLOCK WITH NO ALT RPT. AT THIS POINT I ASKED THE FO TO LEVEL OFF, WHICH HE DID IMMEDIATELY BY HITTING ALT HOLD. I WAS ASSUMING THE TARGET WAS BELOW US SINCE THERE IS A SMALL ARPT IN THE VICINITY, AND WE WERE JUST NEAR THE EDGE OF CLASS B AIRSPACE. I WOULD SAY ABOUT 3 SECONDS AFTER WE STOPPED THE DSCNT, THE RA FUNCTION OF THE TCASII COMMANDED A CLB. I IMMEDIATELY DISCONNECTED THE AUTOPLT AND STARTED TO CLB. WHEN THE TCASII RPTED CLR OF TFC, THE FO RESUMED CTL. I LOOKED OUT THE L WINDOW AND SAW A LIGHT TWIN PASS FROM R TO L BELOW US. I RPTED THE RA TO ATC. AT THIS POINT WE WERE HIGH ON THE GLIDE PATH AND NEEDED THE GEAR AND SPD BRAKE TO GET BACK ON GLIDE PATH. A NORMAL LNDG WAS MADE. I THINK OUR SPD 240-250 KTS AND DSNDING WAS A FACTOR IN THE TCASII RA WARNING.

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.