Narrative:

Small aircraft X 130 sebound overflying csg and cpr Y northbound from tlh direct arnco landing mge. I had 5 aircraft holding at lgc to land atl and small aircraft X overflt. Cpr Y was given clearance to 140 and told to expedite, and I explained my intent was to get him underneath the holding pattern at lgc. I was vectoring 2 of the arrs out of holding and told an air carrier, who was heading 230, cleared direct lgc. He made a left turn to lgc in lieu of a right turn and he was at 140 and quickly becoming traffic for cpr Y. I looked at the data block on small aircraft X and followed the leader line to the target and established his position as northwest of csg. I went to cpr Y, who was out of about 170, and descended him to 110 and told him to expedite. The conflict alert went off with cpr Y out of 142 descending 3 1/2 mi nne of small aircraft X. I told cpr Y to maintain 140 and fly heading 060 degrees. It was too late. I had offset data blocks on all aircraft 2 lengths in lieu of standard 1 length. When I located small aircraft X I followed the data block line to the wrong target, but was unaware of my error until the conflict alert activated.

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Original NASA ASRS Text

Title: CPR Y DSCNT TO OCCUPIED ALT HAD LTSS FROM SMA X. SYS ERROR.

Narrative: SMA X 130 SEBOUND OVERFLYING CSG AND CPR Y NBOUND FROM TLH DIRECT ARNCO LNDG MGE. I HAD 5 ACFT HOLDING AT LGC TO LAND ATL AND SMA X OVERFLT. CPR Y WAS GIVEN CLRNC TO 140 AND TOLD TO EXPEDITE, AND I EXPLAINED MY INTENT WAS TO GET HIM UNDERNEATH THE HOLDING PATTERN AT LGC. I WAS VECTORING 2 OF THE ARRS OUT OF HOLDING AND TOLD AN ACR, WHO WAS HDG 230, CLRED DIRECT LGC. HE MADE A L TURN TO LGC IN LIEU OF A R TURN AND HE WAS AT 140 AND QUICKLY BECOMING TFC FOR CPR Y. I LOOKED AT THE DATA BLOCK ON SMA X AND FOLLOWED THE LEADER LINE TO THE TARGET AND ESTABLISHED HIS POS AS NW OF CSG. I WENT TO CPR Y, WHO WAS OUT OF ABOUT 170, AND DSNDED HIM TO 110 AND TOLD HIM TO EXPEDITE. THE CONFLICT ALERT WENT OFF WITH CPR Y OUT OF 142 DSNDING 3 1/2 MI NNE OF SMA X. I TOLD CPR Y TO MAINTAIN 140 AND FLY HDG 060 DEGS. IT WAS TOO LATE. I HAD OFFSET DATA BLOCKS ON ALL ACFT 2 LENGTHS IN LIEU OF STANDARD 1 LENGTH. WHEN I LOCATED SMA X I FOLLOWED THE DATA BLOCK LINE TO THE WRONG TARGET, BUT WAS UNAWARE OF MY ERROR UNTIL THE CONFLICT ALERT ACTIVATED.

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.