Narrative:

Widebody transport X was southbound on J91 johnn otk leese 5 mco. When he crossed the ZTL ZJX boundary, I cleared him to cross 15 mi southeast of otk at and maintain FL270 (pilot discretion to make the restriction). Large transport Y was northbound cty-mcn at FL310 going to dtw. Widebody transport X had started his descent out of FL330 to FL270 about 20 mi north of otk. Large transport Y flight was about 20 mi south of otk. C/a didn't go off until they were 15 mi apart and widebody transport X was FL310, descending to FL270 I turned widebody transport X right to heading 200. By the time I cleared him and he read it back, it was too late to do anything with the large transport Y flight. I overlooked the widebody transport X descending into large transport Y until C/a went off. The only thing that bothers me is, we are given this tool to work with and to assist us (C/a), but it doesn't work 33 percent of the time. These 2 aircraft were basically head on. The alert didn't go off until widebody transport X was at FL310 and 15 mi apart. If the system was working properly, it should have went off the moment widebody transport X was 300' out of FL330, which would have left them about 35 mi apart. I could have easily avoided this error. I'm not blaming the system because I missed the situation. I'm saying if it is there for us to use as a tool and to assist us, then it should work at all times. Supplemental information from acn 93914. Widebody transport X was southbound cleared from FL330 to descent to cross 15 southeast of otk at FL270. Large transport Y was northbound at FL310. The controller failed to see the traffic and they passed approximately 2 mi apart at close to the same altitude. Traffic was light during the period. I was the supervisor in charge and I was questioned about staffing at the sector. I had 12 operating position to staff and 11 controllers, so one man sectors were necessary. However, in this case, staffing was apparently not a factor. An oversight by the controller.

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Original NASA ASRS Text

Title: ARTCC CTLR HAD LESS THAN STANDARD SEPARATION WHILE DESCENDING A WDB THROUGH ALT OF LGT. OPERATIONAL ERROR.

Narrative: WDB X WAS SBND ON J91 JOHNN OTK LEESE 5 MCO. WHEN HE CROSSED THE ZTL ZJX BOUNDARY, I CLRED HIM TO CROSS 15 MI SE OF OTK AT AND MAINTAIN FL270 (PLT DISCRETION TO MAKE THE RESTRICTION). LGT Y WAS NBOUND CTY-MCN AT FL310 GOING TO DTW. WDB X HAD STARTED HIS DSCNT OUT OF FL330 TO FL270 ABOUT 20 MI N OF OTK. LGT Y FLT WAS ABOUT 20 MI S OF OTK. C/A DIDN'T GO OFF UNTIL THEY WERE 15 MI APART AND WDB X WAS FL310, DSNDING TO FL270 I TURNED WDB X RIGHT TO HDG 200. BY THE TIME I CLRED HIM AND HE READ IT BACK, IT WAS TOO LATE TO DO ANYTHING WITH THE LGT Y FLT. I OVERLOOKED THE WDB X DSNDING INTO LGT Y UNTIL C/A WENT OFF. THE ONLY THING THAT BOTHERS ME IS, WE ARE GIVEN THIS TOOL TO WORK WITH AND TO ASSIST US (C/A), BUT IT DOESN'T WORK 33 PERCENT OF THE TIME. THESE 2 ACFT WERE BASICALLY HEAD ON. THE ALERT DIDN'T GO OFF UNTIL WDB X WAS AT FL310 AND 15 MI APART. IF THE SYS WAS WORKING PROPERLY, IT SHOULD HAVE WENT OFF THE MOMENT WDB X WAS 300' OUT OF FL330, WHICH WOULD HAVE LEFT THEM ABOUT 35 MI APART. I COULD HAVE EASILY AVOIDED THIS ERROR. I'M NOT BLAMING THE SYS BECAUSE I MISSED THE SITUATION. I'M SAYING IF IT IS THERE FOR US TO USE AS A TOOL AND TO ASSIST US, THEN IT SHOULD WORK AT ALL TIMES. SUPPLEMENTAL INFO FROM ACN 93914. WDB X WAS SBND CLRED FROM FL330 TO DSCNT TO CROSS 15 SE OF OTK AT FL270. LGT Y WAS NBOUND AT FL310. THE CTLR FAILED TO SEE THE TFC AND THEY PASSED APPROX 2 MI APART AT CLOSE TO THE SAME ALT. TFC WAS LIGHT DURING THE PERIOD. I WAS THE SUPVR IN CHARGE AND I WAS QUESTIONED ABOUT STAFFING AT THE SECTOR. I HAD 12 OPERATING POS TO STAFF AND 11 CTLRS, SO ONE MAN SECTORS WERE NECESSARY. HOWEVER, IN THIS CASE, STAFFING WAS APPARENTLY NOT A FACTOR. AN OVERSIGHT BY THE CTLR.

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.