Narrative:

On dec/xa/99 at approximately PM43, I was working the radar position at sector 52/53 mpv/plb sector. Aircraft X, an MD80/right was southwest of slk VOR proceeding to yul via plb PLB2 arrival at FL330. Air carrier Y was southeast of slk VOR proceeding southwest via syr VOR at FL310. A third aircraft Z was at FL370 south of plb VOR inbound to yul. Both aircraft Z and air carrier X would arrive at plb VOR at the same time, so in order to provide spacing to yul, I issued air carrier X a clearance direct yul. This turn of at least 30 degrees left of his present course would take him away from the flight path of air carrier Y. Approximately 12 seconds later, I issued air carrier X a descent clearance to 11000 ft. I expected that air carrier X would start his turn as instructed and then begin his descent. I expected that the turn would provide the required separation. I then moved to the D side to check the strips since there was no D side (non radar position) available due to staffing. When I rechked the radar I observed the conflict and the conflict alert activated. Air carrier X data block indicated an altitude of FL328. I took immediate action to resolve the conflict by issuing a clearance to air carrier X to climb and maintain FL330.

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Original NASA ASRS Text

Title: AN ARTCC RADAR CTLR RPT ON A POTENTIAL CONFLICT AND A SYS ERROR WHEN HE LOST SEPARATION BTWN 2 ACR FLTS NEAR SLK, NY.

Narrative: ON DEC/XA/99 AT APPROX PM43, I WAS WORKING THE RADAR POS AT SECTOR 52/53 MPV/PLB SECTOR. ACFT X, AN MD80/R WAS SW OF SLK VOR PROCEEDING TO YUL VIA PLB PLB2 ARR AT FL330. ACR Y WAS SE OF SLK VOR PROCEEDING SW VIA SYR VOR AT FL310. A THIRD ACFT Z WAS AT FL370 S OF PLB VOR INBOUND TO YUL. BOTH ACFT Z AND ACR X WOULD ARRIVE AT PLB VOR AT THE SAME TIME, SO IN ORDER TO PROVIDE SPACING TO YUL, I ISSUED ACR X A CLRNC DIRECT YUL. THIS TURN OF AT LEAST 30 DEGS L OF HIS PRESENT COURSE WOULD TAKE HIM AWAY FROM THE FLT PATH OF ACR Y. APPROX 12 SECONDS LATER, I ISSUED ACR X A DSCNT CLRNC TO 11000 FT. I EXPECTED THAT ACR X WOULD START HIS TURN AS INSTRUCTED AND THEN BEGIN HIS DSCNT. I EXPECTED THAT THE TURN WOULD PROVIDE THE REQUIRED SEPARATION. I THEN MOVED TO THE D SIDE TO CHK THE STRIPS SINCE THERE WAS NO D SIDE (NON RADAR POS) AVAILABLE DUE TO STAFFING. WHEN I RECHKED THE RADAR I OBSERVED THE CONFLICT AND THE CONFLICT ALERT ACTIVATED. ACR X DATA BLOCK INDICATED AN ALT OF FL328. I TOOK IMMEDIATE ACTION TO RESOLVE THE CONFLICT BY ISSUING A CLRNC TO ACR X TO CLB AND MAINTAIN FL330.

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.