Narrative:

I was providing OJT instruction on the arrival east position, we had approximately 10 aircraft on frequency at the time of the error. Air carrier X was on a left downwind, east of the airport, for runway 18L, at 5000'. Air carrier Y was 20 mi northeast of the airport on a base leg to 18L, descending to 6000' inbound to follow air carrier X. Controller a, my trainee, was feeding aircraft to the final controller, at 5000' on a downwind and base leg. Controller a descended air carrier Y to 5000 abeam the airport and handed him off to the east final controller. Radio communications were never transferred. Air carrier X was heading 250 and was descended from 6000 to 5000. The final controller advised the arrival east coordinator that he was not talking to air carrier X. Air carrier Y and air carrier X were then 6-7 mi apart on converging courses, with air carrier X descending out of 5600. I, controller B, then turned air carrier Y left, to heading 200 and descended him to 3000. At the moment that I unkeyed my transmitter, controller a keyed his microphone and turned air carrier X to 270. Controller a then made another transmission, and I never received acknowledgement from air carrier Y. At this time I did not observe air carrier Y making any turns or appear to be descending. I, controller B, instructed air carrier X to turn right immediately heading 360. Controller a again keyed his microphone and turned air carrier Y to heading 250 and climbed air carrier X to 6000. Standard separation was lost about 10 mi northeast of the airport, with both aircraft in turns away from each other. The aircraft came within 2 mi of each other, at the same altitude. I feel the error could have been avoided if controller a had stayed of F the frequency and I took control of the situation.

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Original NASA ASRS Text

Title: ACR WAS VECTORED TOWARD ANOTHER ACR RESULTING IN LESS THAN STANDARD SEPARATION.

Narrative: I WAS PROVIDING OJT INSTRUCTION ON THE ARR EAST POSITION, WE HAD APPROX 10 ACFT ON FREQ AT THE TIME OF THE ERROR. ACR X WAS ON A LEFT DOWNWIND, EAST OF THE ARPT, FOR RWY 18L, AT 5000'. ACR Y WAS 20 MI NE OF THE ARPT ON A BASE LEG TO 18L, DESCENDING TO 6000' INBND TO FOLLOW ACR X. CTLR A, MY TRAINEE, WAS FEEDING ACFT TO THE FINAL CTLR, AT 5000' ON A DOWNWIND AND BASE LEG. CTLR A DESCENDED ACR Y TO 5000 ABEAM THE ARPT AND HANDED HIM OFF TO THE EAST FINAL CTLR. RADIO COMS WERE NEVER TRANSFERRED. ACR X WAS HDG 250 AND WAS DESCENDED FROM 6000 TO 5000. THE FINAL CTLR ADVISED THE ARR EAST COORDINATOR THAT HE WAS NOT TALKING TO ACR X. ACR Y AND ACR X WERE THEN 6-7 MI APART ON CONVERGING COURSES, WITH ACR X DESCENDING OUT OF 5600. I, CTLR B, THEN TURNED ACR Y LEFT, TO HDG 200 AND DESCENDED HIM TO 3000. AT THE MOMENT THAT I UNKEYED MY XMITTER, CTLR A KEYED HIS MIKE AND TURNED ACR X TO 270. CTLR A THEN MADE ANOTHER XMISSION, AND I NEVER RECEIVED ACKNOWLEDGEMENT FROM ACR Y. AT THIS TIME I DID NOT OBSERVE ACR Y MAKING ANY TURNS OR APPEAR TO BE DESCENDING. I, CTLR B, INSTRUCTED ACR X TO TURN RIGHT IMMEDIATELY HDG 360. CTLR A AGAIN KEYED HIS MIKE AND TURNED ACR Y TO HDG 250 AND CLIMBED ACR X TO 6000. STANDARD SEPARATION WAS LOST ABOUT 10 MI NE OF THE ARPT, WITH BOTH ACFT IN TURNS AWAY FROM EACH OTHER. THE ACFT CAME WITHIN 2 MI OF EACH OTHER, AT THE SAME ALT. I FEEL THE ERROR COULD HAVE BEEN AVOIDED IF CTLR A HAD STAYED OF F THE FREQ AND I TOOK CONTROL OF THE SITUATION.

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