Narrative:

Air carrier X was at the abeam downwind position for runway 36L when tower advised something like 'air carrier X you have traffic at 1 O'clock a mi and a half an small transport Y who will be landing on 36R, he has the airport in sight and will not be a factor, cleared to turn base your discretion.' shortly thereafter, the so and I (now strapped in to the jump seat) saw the traffic. Sometime after our sighting, the captain in the seat and first officer student reported the traffic in sight as well. We began our base turn when it appeared that small transport Y was turning slightly toward us still a little high appearing to be in a descent. We rolled out on base heading 090, still having small transport Y in sight. Small transport Y rapidly turned toward us I observed the collision course dynamic. He appeared to be headed toward us in course and descent. At that moment, TCASII said 'stop climb, stop climb!!' and the three colored radials appeared on both vsi's. The command was to level or descend. I loudly said 'lower the nose' and the captain in the seat immediately took the aircraft and abruptly lowered the nose, as I recall, TCASII then said 'descend, descend' and commanded at least a 1000 FPM descent. Small transport Y passed overhead. I believe lateral separation may have been nil and vertical separation less than 300 ft. Small transport Y then reported that he had mistaken another landmark for the airport and requested vectors for another approach. I recall the tower asking small transport Y if he had the large transport in sight and he said no. The tower controller then quickly called us using his 'may-day' voice asking if we had seen small transport Y and telling that 'traffic is no longer a factor'. TCASII proved its value and reliability. Human factors particularly relevant were outside vigilance and team work. When necessary, at cockpit. Also, all cockpit crew members clearly performed as if traffic vigilance and awareness were his own personal responsibilities.

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Original NASA ASRS Text

Title: ACR X HAD NMAC WITH SMT Y IN TFC PATTERN. SEE AND AVOID CONCEPT. TCASII RA EVASIVE ACTION TAKEN.

Narrative: ACR X WAS AT THE ABEAM DOWNWIND POS FOR RWY 36L WHEN TWR ADVISED SOMETHING LIKE 'ACR X YOU HAVE TFC AT 1 O'CLOCK A MI AND A HALF AN SMT Y WHO WILL BE LNDG ON 36R, HE HAS THE ARPT IN SIGHT AND WILL NOT BE A FACTOR, CLRED TO TURN BASE YOUR DISCRETION.' SHORTLY THEREAFTER, THE SO AND I (NOW STRAPPED IN TO THE JUMP SEAT) SAW THE TFC. SOMETIME AFTER OUR SIGHTING, THE CAPT IN THE SEAT AND FO STUDENT RPTED THE TFC IN SIGHT AS WELL. WE BEGAN OUR BASE TURN WHEN IT APPEARED THAT SMT Y WAS TURNING SLIGHTLY TOWARD US STILL A LITTLE HIGH APPEARING TO BE IN A DSCNT. WE ROLLED OUT ON BASE HDG 090, STILL HAVING SMT Y IN SIGHT. SMT Y RAPIDLY TURNED TOWARD US I OBSERVED THE COLLISION COURSE DYNAMIC. HE APPEARED TO BE HEADED TOWARD US IN COURSE AND DSCNT. AT THAT MOMENT, TCASII SAID 'STOP CLB, STOP CLB!!' AND THE THREE COLORED RADIALS APPEARED ON BOTH VSI'S. THE COMMAND WAS TO LEVEL OR DSND. I LOUDLY SAID 'LOWER THE NOSE' AND THE CAPT IN THE SEAT IMMEDIATELY TOOK THE ACFT AND ABRUPTLY LOWERED THE NOSE, AS I RECALL, TCASII THEN SAID 'DSND, DSND' AND COMMANDED AT LEAST A 1000 FPM DSCNT. SMT Y PASSED OVERHEAD. I BELIEVE LATERAL SEPARATION MAY HAVE BEEN NIL AND VERT SEPARATION LESS THAN 300 FT. SMT Y THEN RPTED THAT HE HAD MISTAKEN ANOTHER LANDMARK FOR THE ARPT AND REQUESTED VECTORS FOR ANOTHER APCH. I RECALL THE TWR ASKING SMT Y IF HE HAD THE LGT IN SIGHT AND HE SAID NO. THE TWR CTLR THEN QUICKLY CALLED US USING HIS 'MAY-DAY' VOICE ASKING IF WE HAD SEEN SMT Y AND TELLING THAT 'TFC IS NO LONGER A FACTOR'. TCASII PROVED ITS VALUE AND RELIABILITY. HUMAN FACTORS PARTICULARLY RELEVANT WERE OUTSIDE VIGILANCE AND TEAM WORK. WHEN NECESSARY, AT COCKPIT. ALSO, ALL COCKPIT CREW MEMBERS CLEARLY PERFORMED AS IF TFC VIGILANCE AND AWARENESS WERE HIS OWN PERSONAL RESPONSIBILITIES.

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.