Narrative:

While working radar arrival north and south combined, I took 2 handoffs from ZLC, 35 mi south of boise. Runway 28L&right in use. The aircraft on the left (west) was air carrier X. The aircraft on the right (east) was air carrier Y. They were approximately 6 mi apart, both direct to boise VOR and the same distance out. Air carrier X was about 14000 ft descending to 13000 ft. Air carrier Y was about 16000 ft descending to 14000 ft. I descended air carrier X to 9000 ft and then (before 10000 ft) again to 5000 ft. I descended air carrier Y to 10000 ft and turned air carrier Y left towards air carrier X to achieve a sequence behind air carrier X. At the time I turned air carrier Y, I thought air carrier X was leaving 10000 ft (air carrier Y was at about 11500 ft at that time) and I called air carrier X traffic to air carrier Y and told air carrier Y that air carrier X was leaving 10000 ft. After talking to another aircraft, I looked back to discover that air carrier X was level at 10000 ft and air carrier Y was about 3 mi away, closing and at 10500 ft. I told air carrier Y about the traffic again and told air carrier Y to climb and maintain 11000 ft. Immediately after that transmission, air carrier X advised that he had an RA and was climbing in response. I then went right back to air carrier Y and advised him that air carrier X was climbing and that instead of climbing that air carrier Y should descend. I then resumed normal operation after the aircraft were 1000+ ft, vertically separated and notified the supervisor of what had happened. Supplemental information from acn 348096: air carrier X arriving boi from south, while air carrier Y arriving from sse abeam each other on converging courses with air carrier Y at higher altitude on our right. Boi landing west. Boi approach decided we would be #1 account lower and cleared us from 14000 ft to 9000 ft and keep speed up. Air carrier Y cleared to 10000 ft. Approximately 18 mi south boi at 10100 ft slowing, I saw TCASII target closing from 3 O'clock. I changed to 10 mi scale to check separation and noted 3 mi and closing at 10000 ft. I advised first officer (flying) of traffic closing at 3 O'clock and as I finished the remark, we got a TA followed shortly by an RA climb. First officer reaction was very prompt. I reported RA climbing to ATC. Only after ATC reply did air carrier Y report RA and begin descent. Display showed air carrier Y slow to leave 10000 ft. We climbed above 11500 ft to stop the RA. Later personal contact with air carrier Y captain revealed he saw 200 ft separation on his TCASII. He said he was on 350 degree heading. We were direct boi (approximately heading 010 degrees). Wind strong from northwest. Phone call to tower supervisor and approach controller revealed controller had neglected our slowing at 10000 ft and converging tracks. He said he should have cleared air carrier Y only to 11000 ft. He said it was his fault as he had diverted his attention to another aircraft. We missed only because of our 10100 ft slowing and very prompt RA response by first officer. We could not read TCASII altitude information at instant of RA because it was obscured by our aircraft symbol. Our notice of traffic prior to TA certainly helped our response. Simply flying our own aircraft is not adequate, we must always have part of our mind functioning as a controller. Supplemental information from acn 347799: air carrier X 'descend to 4000 ft' from 10000 ft. Keep your speed up #1 to the airport. My instructions were to descend to 10000 ft turn left to 360 degrees to follow air carrier X. We both entered the clouds at 10000 ft. Soon thereafter we both got an RA on the TCASII. We both reacted to the RA to avoid the conflict at 10000 ft. The controller asked the air carrier X why he didn't descend to 4000 ft. His response was that he had to level at 10000 ft to slow down, putting both of us at 10000 ft. The controller had 2 airplanes in his space and he almost brought them together. I feel he was asleep at the wheel. Both airplanes did what they were told or by FARS.

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Original NASA ASRS Text

Title: APCH CTLR WORKING COMBINED POS WITH 2 ACR ACFT INBOUND VECTORS ONE OF THE ACFT BEHIND THE OTHER RESULTING IN LTSS. BOTH ACFT REACT TO TCASII.

Narrative: WHILE WORKING RADAR ARR N AND S COMBINED, I TOOK 2 HDOFS FROM ZLC, 35 MI S OF BOISE. RWY 28L&R IN USE. THE ACFT ON THE L (W) WAS ACR X. THE ACFT ON THE R (E) WAS ACR Y. THEY WERE APPROX 6 MI APART, BOTH DIRECT TO BOISE VOR AND THE SAME DISTANCE OUT. ACR X WAS ABOUT 14000 FT DSNDING TO 13000 FT. ACR Y WAS ABOUT 16000 FT DSNDING TO 14000 FT. I DSNDED ACR X TO 9000 FT AND THEN (BEFORE 10000 FT) AGAIN TO 5000 FT. I DSNDED ACR Y TO 10000 FT AND TURNED ACR Y L TOWARDS ACR X TO ACHIEVE A SEQUENCE BEHIND ACR X. AT THE TIME I TURNED ACR Y, I THOUGHT ACR X WAS LEAVING 10000 FT (ACR Y WAS AT ABOUT 11500 FT AT THAT TIME) AND I CALLED ACR X TFC TO ACR Y AND TOLD ACR Y THAT ACR X WAS LEAVING 10000 FT. AFTER TALKING TO ANOTHER ACFT, I LOOKED BACK TO DISCOVER THAT ACR X WAS LEVEL AT 10000 FT AND ACR Y WAS ABOUT 3 MI AWAY, CLOSING AND AT 10500 FT. I TOLD ACR Y ABOUT THE TFC AGAIN AND TOLD ACR Y TO CLB AND MAINTAIN 11000 FT. IMMEDIATELY AFTER THAT XMISSION, ACR X ADVISED THAT HE HAD AN RA AND WAS CLBING IN RESPONSE. I THEN WENT RIGHT BACK TO ACR Y AND ADVISED HIM THAT ACR X WAS CLBING AND THAT INSTEAD OF CLBING THAT ACR Y SHOULD DSND. I THEN RESUMED NORMAL OP AFTER THE ACFT WERE 1000+ FT, VERTLY SEPARATED AND NOTIFIED THE SUPVR OF WHAT HAD HAPPENED. SUPPLEMENTAL INFO FROM ACN 348096: ACR X ARRIVING BOI FROM S, WHILE ACR Y ARRIVING FROM SSE ABEAM EACH OTHER ON CONVERGING COURSES WITH ACR Y AT HIGHER ALT ON OUR R. BOI LNDG W. BOI APCH DECIDED WE WOULD BE #1 ACCOUNT LOWER AND CLRED US FROM 14000 FT TO 9000 FT AND KEEP SPD UP. ACR Y CLRED TO 10000 FT. APPROX 18 MI S BOI AT 10100 FT SLOWING, I SAW TCASII TARGET CLOSING FROM 3 O'CLOCK. I CHANGED TO 10 MI SCALE TO CHK SEPARATION AND NOTED 3 MI AND CLOSING AT 10000 FT. I ADVISED FO (FLYING) OF TFC CLOSING AT 3 O'CLOCK AND AS I FINISHED THE REMARK, WE GOT A TA FOLLOWED SHORTLY BY AN RA CLB. FO REACTION WAS VERY PROMPT. I RPTED RA CLBING TO ATC. ONLY AFTER ATC REPLY DID ACR Y RPT RA AND BEGIN DSCNT. DISPLAY SHOWED ACR Y SLOW TO LEAVE 10000 FT. WE CLBED ABOVE 11500 FT TO STOP THE RA. LATER PERSONAL CONTACT WITH ACR Y CAPT REVEALED HE SAW 200 FT SEPARATION ON HIS TCASII. HE SAID HE WAS ON 350 DEG HDG. WE WERE DIRECT BOI (APPROX HDG 010 DEGS). WIND STRONG FROM NW. PHONE CALL TO TWR SUPVR AND APCH CTLR REVEALED CTLR HAD NEGLECTED OUR SLOWING AT 10000 FT AND CONVERGING TRACKS. HE SAID HE SHOULD HAVE CLRED ACR Y ONLY TO 11000 FT. HE SAID IT WAS HIS FAULT AS HE HAD DIVERTED HIS ATTN TO ANOTHER ACFT. WE MISSED ONLY BECAUSE OF OUR 10100 FT SLOWING AND VERY PROMPT RA RESPONSE BY FO. WE COULD NOT READ TCASII ALT INFO AT INSTANT OF RA BECAUSE IT WAS OBSCURED BY OUR ACFT SYMBOL. OUR NOTICE OF TFC PRIOR TO TA CERTAINLY HELPED OUR RESPONSE. SIMPLY FLYING OUR OWN ACFT IS NOT ADEQUATE, WE MUST ALWAYS HAVE PART OF OUR MIND FUNCTIONING AS A CTLR. SUPPLEMENTAL INFO FROM ACN 347799: ACR X 'DSND TO 4000 FT' FROM 10000 FT. KEEP YOUR SPD UP #1 TO THE ARPT. MY INSTRUCTIONS WERE TO DSND TO 10000 FT TURN L TO 360 DEGS TO FOLLOW ACR X. WE BOTH ENTERED THE CLOUDS AT 10000 FT. SOON THEREAFTER WE BOTH GOT AN RA ON THE TCASII. WE BOTH REACTED TO THE RA TO AVOID THE CONFLICT AT 10000 FT. THE CTLR ASKED THE ACR X WHY HE DIDN'T DSND TO 4000 FT. HIS RESPONSE WAS THAT HE HAD TO LEVEL AT 10000 FT TO SLOW DOWN, PUTTING BOTH OF US AT 10000 FT. THE CTLR HAD 2 AIRPLANES IN HIS SPACE AND HE ALMOST BROUGHT THEM TOGETHER. I FEEL HE WAS ASLEEP AT THE WHEEL. BOTH AIRPLANES DID WHAT THEY WERE TOLD OR BY FARS.

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.