Narrative:

I had just sat down to work the arrival push into phoenix from the west coast; and had several items to do as well as several clrncs to issue. There were about 10 IFR aircraft and 4 VFR aircraft on frequency. I had a military aircraft X that was requesting a destination change in phoenix's airspace; and several IFR jets inbound to phoenix. There was an assistant controller trainee that was receiving OJT on the d-side of the sector I was working. When the error occurred; he and his instructor were online; but were talking about the military change in destination. The 2 aircraft that became in conflict were X and Y. Aircraft Y was traveling wbound at 10000 ft. Aircraft X was inbound to phoenix at 11000 ft. I issued aircraft X a 100 degree heading to join the BLH4 arrival. Per the arrival; aircraft X needs to be at 10000 ft MSL by phoenix boundary. I issued aircraft X a descent to 10000 ft because I had a lot of other things going on and I wanted to get him out of the way of the jet traffic inbound to phoenix. (The jets descend to 11000 ft.) at the time; I had several data blocks in the vicinity of abc intersection. Although there was no data block overlap; a VFR data block was covering the tag of aircraft Y. After issuing the descent clearance to aircraft X; I gave a clearance to aircraft Y for his change in destination. He read back part of the clearance and then stated I was broken and could I repeat after blh VOR. While I reissued aircraft Y his clearance; aircraft X was descending to 10000 ft. I did not have a j-ring (or halo) on either aircraft X or aircraft Y; and so I did not see when I lost separation. Conflict alert activated after they were less than 5 NM apart; and that's when I took evasive action to separate the 2 aircraft. I issued both aircraft 40 degree turns; and then once they were separated by more than 5 NM I turned them back on course. The 2 aircraft came within 3.82 NM of one another. I overlooked aircraft Y as he was traveling wbound due to 1) his target being covered by another data block; 2) the complexity of the traffic on the scope; and 3) by being in a hurry in wanting to get the aircraft X down to 10000 ft and out of the way.

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Original NASA ASRS Text

Title: ZAB CONTROLLER EXPERIENCED OPERATIONAL ERROR AT 10000 FT WHEN DESCENDING AIRCRAFT THROUGH OCCUPIED ALTITUDE; FAILING TO SEE CONFLICTING TRAFFIC BECAUSE OF VFR DATA BLOCK COVERING INFORMATION.

Narrative: I HAD JUST SAT DOWN TO WORK THE ARR PUSH INTO PHOENIX FROM THE W COAST; AND HAD SEVERAL ITEMS TO DO AS WELL AS SEVERAL CLRNCS TO ISSUE. THERE WERE ABOUT 10 IFR ACFT AND 4 VFR ACFT ON FREQ. I HAD A MIL ACFT X THAT WAS REQUESTING A DEST CHANGE IN PHOENIX'S AIRSPACE; AND SEVERAL IFR JETS INBOUND TO PHOENIX. THERE WAS AN ASSISTANT CTLR TRAINEE THAT WAS RECEIVING OJT ON THE D-SIDE OF THE SECTOR I WAS WORKING. WHEN THE ERROR OCCURRED; HE AND HIS INSTRUCTOR WERE ONLINE; BUT WERE TALKING ABOUT THE MIL CHANGE IN DEST. THE 2 ACFT THAT BECAME IN CONFLICT WERE X AND Y. ACFT Y WAS TRAVELING WBOUND AT 10000 FT. ACFT X WAS INBOUND TO PHOENIX AT 11000 FT. I ISSUED ACFT X A 100 DEG HDG TO JOIN THE BLH4 ARR. PER THE ARR; ACFT X NEEDS TO BE AT 10000 FT MSL BY PHOENIX BOUNDARY. I ISSUED ACFT X A DSCNT TO 10000 FT BECAUSE I HAD A LOT OF OTHER THINGS GOING ON AND I WANTED TO GET HIM OUT OF THE WAY OF THE JET TFC INBOUND TO PHOENIX. (THE JETS DSND TO 11000 FT.) AT THE TIME; I HAD SEVERAL DATA BLOCKS IN THE VICINITY OF ABC INTXN. ALTHOUGH THERE WAS NO DATA BLOCK OVERLAP; A VFR DATA BLOCK WAS COVERING THE TAG OF ACFT Y. AFTER ISSUING THE DSCNT CLRNC TO ACFT X; I GAVE A CLRNC TO ACFT Y FOR HIS CHANGE IN DEST. HE READ BACK PART OF THE CLRNC AND THEN STATED I WAS BROKEN AND COULD I REPEAT AFTER BLH VOR. WHILE I REISSUED ACFT Y HIS CLRNC; ACFT X WAS DSNDING TO 10000 FT. I DID NOT HAVE A J-RING (OR HALO) ON EITHER ACFT X OR ACFT Y; AND SO I DID NOT SEE WHEN I LOST SEPARATION. CONFLICT ALERT ACTIVATED AFTER THEY WERE LESS THAN 5 NM APART; AND THAT'S WHEN I TOOK EVASIVE ACTION TO SEPARATE THE 2 ACFT. I ISSUED BOTH ACFT 40 DEG TURNS; AND THEN ONCE THEY WERE SEPARATED BY MORE THAN 5 NM I TURNED THEM BACK ON COURSE. THE 2 ACFT CAME WITHIN 3.82 NM OF ONE ANOTHER. I OVERLOOKED ACFT Y AS HE WAS TRAVELING WBOUND DUE TO 1) HIS TARGET BEING COVERED BY ANOTHER DATA BLOCK; 2) THE COMPLEXITY OF THE TFC ON THE SCOPE; AND 3) BY BEING IN A HURRY IN WANTING TO GET THE ACFT X DOWN TO 10000 FT AND OUT OF THE WAY.

Data retrieved from NASA's ASRS site as of May 2009 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.