Narrative:

While vectoring numerous aircraft through a line of heavy thunderstorms, I received a pointout for air carrier Y, B737, at 6000 ft to descend to 3000 ft. Workload was heavy as pilots were constantly inquiring about WX conditions, requests for deviation, etc. I observed air carrier Y mode C at 5800 ft while scanning and after determining a descent was occurring proceed to clear my arrs including air carrier X, B757, to 6000 ft. Situation developed because other arrival controller was similarly overwhelmed by workload and failed to issue further descent clearance in a timely manner to air carrier Y. This was compounded by a mode C fluctuation which appeared to indicate a descent. When I observed the conflict, aircraft were on 60 degree converging path. I issued a turn and climb to air carrier X to establish separation. Conflict alert went off after targets were separated by course divergence. The lesson here I believe is to resist the urge to continue to run traffic at a normal volume when abnormal meteorological conditions create a high workload environment. Supplemental information from acn 341365: we were assigned, and at, 6000 ft on a 170 degree heading, approximately 10 mi north of speez intersection. Approach then issued an immediate clearance to climb to 7000 ft and left turn to 090 degrees. At the same time we started the climb the TCASII gave us an RA at 100 ft above us, and told us to descend. However, we were already established in the climb and very shortly the TCASII changed to don't descend. We reached 6500 ft as the other aircraft passed 1 1/2 mi behind and 1000 ft below us, as seen on TCASII and confirmed by ATC later on the phone. After landing, the ATC supervisor relayed to the captain, that the controller had used poor judgement. When he noticed the aircraft too close he gave us the climb to 7000 ft and the other aircraft a descent to 5000 ft. We never visually saw the other aircraft as we were IMC. Also the TCASII allowed us to see the position of the other aircraft, but because we had already received a clearance to avoid the aircraft, the TCASII correction was a nuisance.

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Original NASA ASRS Text

Title: APCH CTLR VECTORING A B757 FOR APCH DSNDED THE ACFT TO 6000 FT WHEN HE SAW A B737 WORKING WITH ADJACENT ARR CTLR APPEAR TO LEAVE 6000 FT. ON A SECOND SCAN HE SAW THAT THE B737 WAS STILL AT 6000 FT AND ACFT WERE CONVERGING, SO HE CLBED THE B757 TO 7000 FT. THE B757 GOT A TCASII RA TO DSND, BUT IGNORED IT AS HE WAS ALREADY CLBING AND IN THE TURN THE CTLR HAD GIVEN HIM. LTSS OCCURRED.

Narrative: WHILE VECTORING NUMEROUS ACFT THROUGH A LINE OF HVY TSTMS, I RECEIVED A POINTOUT FOR ACR Y, B737, AT 6000 FT TO DSND TO 3000 FT. WORKLOAD WAS HVY AS PLTS WERE CONSTANTLY INQUIRING ABOUT WX CONDITIONS, REQUESTS FOR DEV, ETC. I OBSERVED ACR Y MODE C AT 5800 FT WHILE SCANNING AND AFTER DETERMINING A DSCNT WAS OCCURRING PROCEED TO CLR MY ARRS INCLUDING ACR X, B757, TO 6000 FT. SIT DEVELOPED BECAUSE OTHER ARR CTLR WAS SIMILARLY OVERWHELMED BY WORKLOAD AND FAILED TO ISSUE FURTHER DSCNT CLRNC IN A TIMELY MANNER TO ACR Y. THIS WAS COMPOUNDED BY A MODE C FLUCTUATION WHICH APPEARED TO INDICATE A DSCNT. WHEN I OBSERVED THE CONFLICT, ACFT WERE ON 60 DEG CONVERGING PATH. I ISSUED A TURN AND CLB TO ACR X TO ESTABLISH SEPARATION. CONFLICT ALERT WENT OFF AFTER TARGETS WERE SEPARATED BY COURSE DIVERGENCE. THE LESSON HERE I BELIEVE IS TO RESIST THE URGE TO CONTINUE TO RUN TFC AT A NORMAL VOLUME WHEN ABNORMAL METEOROLOGICAL CONDITIONS CREATE A HIGH WORKLOAD ENVIRONMENT. SUPPLEMENTAL INFO FROM ACN 341365: WE WERE ASSIGNED, AND AT, 6000 FT ON A 170 DEG HDG, APPROX 10 MI N OF SPEEZ INTXN. APCH THEN ISSUED AN IMMEDIATE CLRNC TO CLB TO 7000 FT AND L TURN TO 090 DEGS. AT THE SAME TIME WE STARTED THE CLB THE TCASII GAVE US AN RA AT 100 FT ABOVE US, AND TOLD US TO DSND. HOWEVER, WE WERE ALREADY ESTABLISHED IN THE CLB AND VERY SHORTLY THE TCASII CHANGED TO DON'T DSND. WE REACHED 6500 FT AS THE OTHER ACFT PASSED 1 1/2 MI BEHIND AND 1000 FT BELOW US, AS SEEN ON TCASII AND CONFIRMED BY ATC LATER ON THE PHONE. AFTER LNDG, THE ATC SUPVR RELAYED TO THE CAPT, THAT THE CTLR HAD USED POOR JUDGEMENT. WHEN HE NOTICED THE ACFT TOO CLOSE HE GAVE US THE CLB TO 7000 FT AND THE OTHER ACFT A DSCNT TO 5000 FT. WE NEVER VISUALLY SAW THE OTHER ACFT AS WE WERE IMC. ALSO THE TCASII ALLOWED US TO SEE THE POS OF THE OTHER ACFT, BUT BECAUSE WE HAD ALREADY RECEIVED A CLRNC TO AVOID THE ACFT, THE TCASII CORRECTION WAS A NUISANCE.

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.