Narrative:

I was working the roc sector 31 at the time of the incident. Previously, the buf sector backup system failed, and although there were no problems with the running of the buf sector, the technicians wanted to take buf sector down for an hour, roughly, to attempt to fix it. This resulted in 2 potentially busy sectors being merged into 1 large, busy sector. These sectors are never combined at that time of day during normal, wkday traffic. I was flashed a handoff on aircraft X landing roc. I was so busy at the time that the other controller had to call me on our boundary about the handoff. The data block indicated aircraft X was descending to 11000 ft, but the aircraft checked on level at FL190. I missed that, however, and issued an altimeter, thinking he was descending to 11000 ft cross buf at 11000 ft, the standard restr. Thus, in my mind, he was separated from aircraft Y -- a toronto lander -- descending over buf to 17000 ft. Buf was the confliction point. When I noticed aircraft X was still at FL190, I told him to start down to 11000 ft and hurry. However, by this time, aircraft Y had leveled at 17000 ft, and there was not enough time for even a fast descent by aircraft X to clear up the situation. I did not see the impending loss of separation until the conflict alert activated as aircraft X showed leaving 17900 ft. I tried to see if aircraft X could go back to FL180 but he was already leaving 17400 ft and looking for traffic. I turned both aircraft 30 degrees left, not to keep separation which had already been lost, but to keep the targets from merging. Neither pilot mentioned TCASII. Supplemental information from acn 620092: aircraft #1 was descending to FL190. Data block updated to 11000 ft. Handoff was initiated as aircraft #2 was nearing adjacent boundary, but 11000 ft was not issued. Multiple aircraft on my frequency. Aircraft #1 was approaching the adjacent sector boundary and showing handoff as being accepted, so I changed its frequency without issuing a descent clearance to cross buf VOR at 11000 ft which is the SOP. My actions of not ensuring that data block and issued clrncs of aircraft #1 were consistent contributed to a subsequent lack of separation. The importance of following through to ensure clrncs reflect flight data cannot be overstressed.

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Original NASA ASRS Text

Title: ZOB CTLR EXPERIENCED OPERROR OVER BUF VOR AT 17000 FT WHEN ONE ACR FLT WAS CLRED TO DSND THROUGH THE ALT OF ANOTHER ACR FLT.

Narrative: I WAS WORKING THE ROC SECTOR 31 AT THE TIME OF THE INCIDENT. PREVIOUSLY, THE BUF SECTOR BACKUP SYS FAILED, AND ALTHOUGH THERE WERE NO PROBS WITH THE RUNNING OF THE BUF SECTOR, THE TECHNICIANS WANTED TO TAKE BUF SECTOR DOWN FOR AN HR, ROUGHLY, TO ATTEMPT TO FIX IT. THIS RESULTED IN 2 POTENTIALLY BUSY SECTORS BEING MERGED INTO 1 LARGE, BUSY SECTOR. THESE SECTORS ARE NEVER COMBINED AT THAT TIME OF DAY DURING NORMAL, WKDAY TFC. I WAS FLASHED A HDOF ON ACFT X LNDG ROC. I WAS SO BUSY AT THE TIME THAT THE OTHER CTLR HAD TO CALL ME ON OUR BOUNDARY ABOUT THE HDOF. THE DATA BLOCK INDICATED ACFT X WAS DSNDING TO 11000 FT, BUT THE ACFT CHKED ON LEVEL AT FL190. I MISSED THAT, HOWEVER, AND ISSUED AN ALTIMETER, THINKING HE WAS DSNDING TO 11000 FT CROSS BUF AT 11000 FT, THE STANDARD RESTR. THUS, IN MY MIND, HE WAS SEPARATED FROM ACFT Y -- A TORONTO LANDER -- DSNDING OVER BUF TO 17000 FT. BUF WAS THE CONFLICTION POINT. WHEN I NOTICED ACFT X WAS STILL AT FL190, I TOLD HIM TO START DOWN TO 11000 FT AND HURRY. HOWEVER, BY THIS TIME, ACFT Y HAD LEVELED AT 17000 FT, AND THERE WAS NOT ENOUGH TIME FOR EVEN A FAST DSCNT BY ACFT X TO CLR UP THE SIT. I DID NOT SEE THE IMPENDING LOSS OF SEPARATION UNTIL THE CONFLICT ALERT ACTIVATED AS ACFT X SHOWED LEAVING 17900 FT. I TRIED TO SEE IF ACFT X COULD GO BACK TO FL180 BUT HE WAS ALREADY LEAVING 17400 FT AND LOOKING FOR TFC. I TURNED BOTH ACFT 30 DEGS L, NOT TO KEEP SEPARATION WHICH HAD ALREADY BEEN LOST, BUT TO KEEP THE TARGETS FROM MERGING. NEITHER PLT MENTIONED TCASII. SUPPLEMENTAL INFO FROM ACN 620092: ACFT #1 WAS DSNDING TO FL190. DATA BLOCK UPDATED TO 11000 FT. HDOF WAS INITIATED AS ACFT #2 WAS NEARING ADJACENT BOUNDARY, BUT 11000 FT WAS NOT ISSUED. MULTIPLE ACFT ON MY FREQ. ACFT #1 WAS APCHING THE ADJACENT SECTOR BOUNDARY AND SHOWING HDOF AS BEING ACCEPTED, SO I CHANGED ITS FREQ WITHOUT ISSUING A DSCNT CLRNC TO CROSS BUF VOR AT 11000 FT WHICH IS THE SOP. MY ACTIONS OF NOT ENSURING THAT DATA BLOCK AND ISSUED CLRNCS OF ACFT #1 WERE CONSISTENT CONTRIBUTED TO A SUBSEQUENT LACK OF SEPARATION. THE IMPORTANCE OF FOLLOWING THROUGH TO ENSURE CLRNCS REFLECT FLT DATA CANNOT BE OVERSTRESSED.

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.