Narrative:

Aircraft X was one of three aircraft southbound (others were aircraft Y going to lax or somewhere else in southern california; and aircraft Z going to las.) the aircraft X and aircraft Y were on the same route and the aircraft Z was slowly diverging to the west. Aircraft X and aircraft Y were both filed for FL370. Aircraft Z was filed at FL390. Aircraft Y was stopped at FL350 due to all three aircraft being tied. Aircraft X was at FL370. I had evaluated their routing to see if there was a way to split the aircraft X and aircraft Y up to get the aircraft Z to their requested altitude; but due to military airspace in use further along their route it was not a good choice and I was going to just leave the aircraft Z at FL350 (same route; all filed TAS were within 10 KTS of each other.) then the aircraft X requested FL390 to try and get out of the light chop. This would then open FL370 to the aircraft Z; so I put a j-ring on the aircraft Y (who was at FL390) to see if he had diverged enough yet. I asked the aircraft their mach numbers and when I saw that I had enough room; I assigned mach numbers and climbed the aircraft X to FL390. Unfortunately; aircraft west (same carrier as aircraft X) was northbound into this mix at FL380. His data block was overlapped a bit and even though I had been moving data blocks around to keep them apart; I missed seeing aircraft west as traffic. Only a little bit after issuing the climb; I realized the aircraft west was northbound and traffic at FL380. The mode C of the aircraft X and aircraft Z had earlier been criss-crossed and I probably hesitated a beat trying to figure out what I was looking at; but then realized I had issued a bad clearance. I re cleared aircraft X to go back down and maintain FL370. I put FL370 into the data block as a 'hard' (assigned) altitude and hoped for the best. He had gotten to FL372 and so the data block switched to show him level. On one sweep (which turned out to be the closest point laterally for the two aircraft X and west aircraft) the data block indicated FL373; and then back to FL370. The conflict alert never went off. I figured they must have remained okay with the required separation (there were a lot of data blocks and position symbols;leader lines and vector lines in there) but then the aircraft west said that he had gone over traffic that was only 600 ft underneath him. The southbound aircraft X said something like that as well. I never noticed if the uret was indicating a 'red' alert on the aircraft when I originally cleared aircraft X to climb. To be frank; when one-manning a sector; I rarely look at or use the uret at all unless I am doing some kind of coordination. After aircraft west said that he had only 600 ft of separation I turned to the flm (flight line manager) and called him over to inform him of the situation. I was then relieved and wound up in the quality assurance office where they did their thing and informed me that it was a category 'B' error and a standard investigation would follow. Recommendation; I can't believe I'm saying this; but I think we need to bring back strips. I was a big proponent of uret but the problem with it is that it encourages controllers and supervisors to one-man sectors more often. During this event I was not terribly busy; but just busy enough that in the days of paper flight strips I probably would have had a d-side. And having a d-side would have most likely prevented this from happening; because it would have doubled the number of people keeping watch. A d-side would not have been cognitively 'locked in' on the three south bounders situation like I was. Even if I had been alone; had I been using strips I would have had more chance of not committing this error. When we had strips; my operating practice was to place a check mark alongside the altitude when an aircraft checked on the frequency. It has been shown that physically touching a strip/strip holder helps to better cement the informationinto your mind; that would have helped me remember that there was a northbound aircraft at FL380. New-school controllers overly rely upon uret; to the point of having errors because they don't look enough at the actual situation if uret indicates that it's okay. They don't judge the situation for themselves. Old-school guys like me ignore uret; even when it's probably giving them information that would help (I assume that in my instance uret was indicating a 'red' alert) because too often they see it indicating errors that aren't really there (false positives); and missing situations that it purports to catch (also a problem because if you're relying on it to tell you what's wrong; and it misses things; then you're not looking for it). Unless/until uret is truly integrated with or becomes a more reliable conflict alert solution; it actually makes things worse; not better. Also; if at all possible; the radar conflict alert (not the uret version) needs to incorporate not just mode C information; but should be predictive (like uret is) based on what's in the data block. The southbound aircraft (aircraft X) delayed the start of his climb a little bit; staying at FL370; which led to the radar conflict alert not going off at all. Had it gone off based on the data block information with a normal amount of time; I probably could have reacted in sufficient time to resolve the situation.

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Original NASA ASRS Text

Title: ZSE Controller experienced a loss of separation when failing to note a northbound aircraft that was in conflict with three southbound aircraft; some in the process of changing altitudes; reporting indicating the use of strips may have prevented this event.

Narrative: Aircraft X was one of three aircraft southbound (others were Aircraft Y going to LAX or somewhere else in Southern California; and Aircraft Z going to LAS.) The Aircraft X and Aircraft Y were on the same route and the Aircraft Z was slowly diverging to the west. Aircraft X and Aircraft Y were both filed for FL370. Aircraft Z was filed at FL390. Aircraft Y was stopped at FL350 due to all three aircraft being tied. Aircraft X was at FL370. I had evaluated their routing to see if there was a way to split the Aircraft X and Aircraft Y up to get the Aircraft Z to their requested altitude; but due to military airspace in use further along their route it was not a good choice and I was going to just leave the Aircraft Z at FL350 (same route; all filed TAS were within 10 KTS of each other.) Then the Aircraft X requested FL390 to try and get out of the light chop. This would then open FL370 to the Aircraft Z; so I put a J-ring on the Aircraft Y (who was at FL390) to see if he had diverged enough yet. I asked the aircraft their mach numbers and when I saw that I had enough room; I assigned mach numbers and climbed the Aircraft X to FL390. Unfortunately; Aircraft W (Same carrier as Aircraft X) was northbound into this mix at FL380. His data block was overlapped a bit and even though I had been moving data blocks around to keep them apart; I missed seeing Aircraft W as traffic. Only a little bit after issuing the climb; I realized the Aircraft W was northbound and traffic at FL380. The mode C of the Aircraft X and Aircraft Z had earlier been criss-crossed and I probably hesitated a beat trying to figure out what I was looking at; but then realized I had issued a bad clearance. I re cleared Aircraft X to go back down and maintain FL370. I put FL370 into the data block as a 'hard' (assigned) altitude and hoped for the best. He had gotten to FL372 and so the data block switched to show him level. On one sweep (which turned out to be the closest point laterally for the two Aircraft X and W aircraft) the data block indicated FL373; and then back to FL370. The conflict alert never went off. I figured they must have remained okay with the required separation (there were a lot of data blocks and position symbols;leader lines and vector lines in there) but then the Aircraft W said that he had gone over traffic that was only 600 FT underneath him. The southbound Aircraft X said something like that as well. I never noticed if the URET was indicating a 'red' alert on the aircraft when I originally cleared Aircraft X to climb. To be frank; when one-manning a sector; I rarely look at or use the URET at all unless I am doing some kind of coordination. After Aircraft W said that he had only 600 FT of separation I turned to the FLM (Flight Line Manager) and called him over to inform him of the situation. I was then relieved and wound up in the Quality Assurance office where they did their thing and informed me that it was a category 'B' error and a standard investigation would follow. Recommendation; I can't believe I'm saying this; but I think we need to bring back strips. I was a big proponent of URET but the problem with it is that it encourages controllers and supervisors to one-man sectors more often. During this event I was not terribly busy; but just busy enough that in the days of paper flight strips I probably would have had a D-side. And having a D-side would have most likely prevented this from happening; because it would have doubled the number of people keeping watch. A D-side would not have been cognitively 'locked in' on the three south bounders situation like I was. Even if I had been alone; had I been using strips I would have had more chance of not committing this error. When we had strips; my operating practice was to place a check mark alongside the altitude when an aircraft checked on the frequency. It has been shown that physically touching a strip/strip holder helps to better cement the informationinto your mind; that would have helped me remember that there was a northbound aircraft at FL380. New-school controllers overly rely upon URET; to the point of having errors because they don't look enough at the actual situation if URET indicates that it's okay. They don't judge the situation for themselves. Old-school guys like me ignore URET; even when it's probably giving them information that would help (I assume that in my instance URET was indicating a 'red' alert) because too often they see it indicating errors that aren't really there (false positives); and missing situations that it purports to catch (also a problem because if you're relying on it to tell you what's wrong; and it misses things; then you're not looking for it). Unless/until URET is truly integrated with or becomes a more reliable conflict alert solution; it actually makes things worse; not better. Also; if at all possible; the RADAR conflict alert (not the URET version) needs to incorporate not just mode C information; but should be predictive (like URET is) based on what's in the data block. The southbound aircraft (Aircraft X) delayed the start of his climb a little bit; staying at FL370; which led to the RADAR conflict alert NOT going off at all. Had it gone off based on the data block information with a normal amount of time; I probably could have reacted in sufficient time to resolve the situation.

Data retrieved from NASA's ASRS site as of April 2012 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.