Narrative:

While being vectored to final approach at den, a runway change from 17L and right to runway 26L and right occurred. Approach control did a nice job of keeping things in order using a min of separation between aircraft. We were given the position of our traffic to follow and called him in sight. We accepted the 'visual approach' clearance seeing a 3 NM separation from our traffic on our TCASII system. We anticipated our traffic maintaining the requested '170 KTS to the marker,' however we began to notice a very gradual deceleration. We were then distraction by the TCASII system issuing ras on the parallel approach traffic. In watching the parallel traffic, we did not notice the deceleration of our traffic to follow until separation had decreased to approximately 2 1/2 NM. We then knew the timing of our traffic's exit from the runway would be critical... So did the tower. The tower requested the traffic to exit at the high speed exit. The traffic said they were unable and proceeded to the next exit. Our altitude (AGL) on final was less than 500 ft when the traffic got to the next exit. Chances are we would have touched down as the traffic cleared, however, and rightfully so, the tower took the more conservative option and directed us to 'go around.' an uneventful go around, approach and landing followed. We recognize it is our responsibility to maintain adequate separation from traffic during visual approachs. Many factors were coming together on this visual approach that required ultimate attention to detail. At the end of a long day, we allowed ourselves to be distraction by the TCASII ras on the parallel traffic to runway 26R. Although the TCASII was extremely useful in recognizing separation on our traffic, it ultimately lead to a loss of separation necessary to land out of the visual approach. Again, loss of adequate separation was our responsibility. But TCASII RA's are serious occurrences that require attention. However, it seems we may have given it too much attention and not enough on our traffic ahead.

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Original NASA ASRS Text

Title: MLG MADE GAR WHEN SPACING WAS LOST WITH THE PRECEDING ACFT.

Narrative: WHILE BEING VECTORED TO FINAL APCH AT DEN, A RWY CHANGE FROM 17L AND R TO RWY 26L AND R OCCURRED. APCH CTL DID A NICE JOB OF KEEPING THINGS IN ORDER USING A MIN OF SEPARATION BTWN ACFT. WE WERE GIVEN THE POS OF OUR TFC TO FOLLOW AND CALLED HIM IN SIGHT. WE ACCEPTED THE 'VISUAL APCH' CLRNC SEEING A 3 NM SEPARATION FROM OUR TFC ON OUR TCASII SYS. WE ANTICIPATED OUR TFC MAINTAINING THE REQUESTED '170 KTS TO THE MARKER,' HOWEVER WE BEGAN TO NOTICE A VERY GRADUAL DECELERATION. WE WERE THEN DISTR BY THE TCASII SYS ISSUING RAS ON THE PARALLEL APCH TFC. IN WATCHING THE PARALLEL TFC, WE DID NOT NOTICE THE DECELERATION OF OUR TFC TO FOLLOW UNTIL SEPARATION HAD DECREASED TO APPROX 2 1/2 NM. WE THEN KNEW THE TIMING OF OUR TFC'S EXIT FROM THE RWY WOULD BE CRITICAL... SO DID THE TWR. THE TWR REQUESTED THE TFC TO EXIT AT THE HIGH SPD EXIT. THE TFC SAID THEY WERE UNABLE AND PROCEEDED TO THE NEXT EXIT. OUR ALT (AGL) ON FINAL WAS LESS THAN 500 FT WHEN THE TFC GOT TO THE NEXT EXIT. CHANCES ARE WE WOULD HAVE TOUCHED DOWN AS THE TFC CLRED, HOWEVER, AND RIGHTFULLY SO, THE TWR TOOK THE MORE CONSERVATIVE OPTION AND DIRECTED US TO 'GAR.' AN UNEVENTFUL GAR, APCH AND LNDG FOLLOWED. WE RECOGNIZE IT IS OUR RESPONSIBILITY TO MAINTAIN ADEQUATE SEPARATION FROM TFC DURING VISUAL APCHS. MANY FACTORS WERE COMING TOGETHER ON THIS VISUAL APCH THAT REQUIRED ULTIMATE ATTN TO DETAIL. AT THE END OF A LONG DAY, WE ALLOWED OURSELVES TO BE DISTR BY THE TCASII RAS ON THE PARALLEL TFC TO RWY 26R. ALTHOUGH THE TCASII WAS EXTREMELY USEFUL IN RECOGNIZING SEPARATION ON OUR TFC, IT ULTIMATELY LEAD TO A LOSS OF SEPARATION NECESSARY TO LAND OUT OF THE VISUAL APCH. AGAIN, LOSS OF ADEQUATE SEPARATION WAS OUR RESPONSIBILITY. BUT TCASII RA'S ARE SERIOUS OCCURRENCES THAT REQUIRE ATTN. HOWEVER, IT SEEMS WE MAY HAVE GIVEN IT TOO MUCH ATTN AND NOT ENOUGH ON OUR TFC AHEAD.

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.