Narrative:

E120 was not displayed on scope during relief briefing and not known as traffic. I assumed position and descended A318 and did not see any traffic as a factor. The limited data block was not seen; but there. The conflict alert alerted and brought up the E120 data block as traffic. I issued a turn to the A318 who then informed me he was responding to RA and climbing. The E120 was not briefed as traffic; nor did I observe the limited data block. The controller being relieved took over the d-side position since the E120 data block was never displayed on the scope during my briefing. I did not see the traffic. Supplemental information from acn 671290: a controller in training was assigned to the radar position that could not work the position by herself. I briefed her on the position and then moved to her assistant or d-side position. I had somehow inadvertently taken the data block off one of the affected aircraft (E120) off our scope after the next sector had accepted the handoff. When the radar person descended the A318; conflict alert activated and forced the data block of the E120 back on our scope. The r-side turned the A318 20 degrees to the right; but at point the aircraft were side-by-side with approximately 34 mi separation.

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Original NASA ASRS Text

Title: ZLA CTLRS EXPERIENCED OPERROR AT FL230 AS RELIEVING CTLR ISSUED DSCNT; NOT OBSERVING CONFLICTING TFC WITH LIMITED DATA BLOCK.

Narrative: E120 WAS NOT DISPLAYED ON SCOPE DURING RELIEF BRIEFING AND NOT KNOWN AS TFC. I ASSUMED POS AND DSNDED A318 AND DID NOT SEE ANY TFC AS A FACTOR. THE LIMITED DATA BLOCK WAS NOT SEEN; BUT THERE. THE CONFLICT ALERT ALERTED AND BROUGHT UP THE E120 DATA BLOCK AS TFC. I ISSUED A TURN TO THE A318 WHO THEN INFORMED ME HE WAS RESPONDING TO RA AND CLBING. THE E120 WAS NOT BRIEFED AS TFC; NOR DID I OBSERVE THE LIMITED DATA BLOCK. THE CTLR BEING RELIEVED TOOK OVER THE D-SIDE POS SINCE THE E120 DATA BLOCK WAS NEVER DISPLAYED ON THE SCOPE DURING MY BRIEFING. I DID NOT SEE THE TFC. SUPPLEMENTAL INFO FROM ACN 671290: A CTLR IN TRAINING WAS ASSIGNED TO THE RADAR POS THAT COULD NOT WORK THE POS BY HERSELF. I BRIEFED HER ON THE POS AND THEN MOVED TO HER ASSISTANT OR D-SIDE POS. I HAD SOMEHOW INADVERTENTLY TAKEN THE DATA BLOCK OFF ONE OF THE AFFECTED ACFT (E120) OFF OUR SCOPE AFTER THE NEXT SECTOR HAD ACCEPTED THE HDOF. WHEN THE RADAR PERSON DSNDED THE A318; CONFLICT ALERT ACTIVATED AND FORCED THE DATA BLOCK OF THE E120 BACK ON OUR SCOPE. THE R-SIDE TURNED THE A318 20 DEGS TO THE R; BUT AT POINT THE ACFT WERE SIDE-BY-SIDE WITH APPROX 34 MI SEPARATION.

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