Narrative:

I was working a very busy departure rush out of slc, ut. Slc approach control gave me 2 aircraft departing southeast bound. The aircraft to the north was on a route which would take it further south than the aircraft to the south. I would have to cross these aircraft while climbing. This would enter slowing one aircraft's climb and 'laddering' it up. The aircraft to the north air carrier X was at a higher altitude to begin with so as I observed X leaving 19000 ft, I cleared air carrier Y to maintain that altitude. I did this until I observed air carrier X at FL230 and I cleared the xx to maintain FL230. Y was within the 5 mi circle of lateral space we are supposed to protect. I then realized that X had not received another altitude clearance and he was level at FL230, not climbing though FL230. I descend Y to FL220 and climbed X to FL290. The cause of the error was that I failed to remember what X was climbing too, partly because I was very busy at the time but also because I failed to update the computer data block to indicate X was stopped at FL230.

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Original NASA ASRS Text

Title: ACR Y CLB TO OCCUPIED ALT HAD LTSS FROM ACR X. SYS ERROR.

Narrative: I WAS WORKING A VERY BUSY DEP RUSH OUT OF SLC, UT. SLC APCH CTL GAVE ME 2 ACFT DEPARTING SE BOUND. THE ACFT TO THE N WAS ON A RTE WHICH WOULD TAKE IT FURTHER S THAN THE ACFT TO THE S. I WOULD HAVE TO CROSS THESE ACFT WHILE CLBING. THIS WOULD ENTER SLOWING ONE ACFT'S CLB AND 'LADDERING' IT UP. THE ACFT TO THE N ACR X WAS AT A HIGHER ALT TO BEGIN WITH SO AS I OBSERVED X LEAVING 19000 FT, I CLRED ACR Y TO MAINTAIN THAT ALT. I DID THIS UNTIL I OBSERVED ACR X AT FL230 AND I CLRED THE XX TO MAINTAIN FL230. Y WAS WITHIN THE 5 MI CIRCLE OF LATERAL SPACE WE ARE SUPPOSED TO PROTECT. I THEN REALIZED THAT X HAD NOT RECEIVED ANOTHER ALT CLRNC AND HE WAS LEVEL AT FL230, NOT CLBING THOUGH FL230. I DSND Y TO FL220 AND CLBED X TO FL290. THE CAUSE OF THE ERROR WAS THAT I FAILED TO REMEMBER WHAT X WAS CLBING TOO, PARTLY BECAUSE I WAS VERY BUSY AT THE TIME BUT ALSO BECAUSE I FAILED TO UPDATE THE COMPUTER DATA BLOCK TO INDICATE X WAS STOPPED AT FL230.

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.