Narrative:

Aircraft Y was en route to dfw at FL280 established on J6 wbound. Aircraft X was 12-15 NM north of aircraft Y at FL310 direct bwg, also en route to dfw. Aircraft X was experiencing moderate chop at FL310 and requested descent to FL280. I descended aircraft X to what I thought was FL290. I entered FL280 into the computer as the 'assigned' altitude and intended to enter the 'temporary altitude' of FL290. I went on and performed several other control functions. While aircraft X was descending, I turned the aircraft to a 180 degree heading attempting to put aircraft X and aircraft Y in-trail to dfw at FL280. I issued traffic to aircraft X and explained what I was doing. I did not recognize the discrepancy until conflict-alert activated. I'm not exactly sure what could be done to prevent similar sits in the future. The only correlation I can think of is that I was typing FL280 into the machine while I was issuing the clearance. My brain thought FL290, but my mouth said what I was typing FL280. Supplemental information from acn 419487: the MD80 (aircraft X) was inadvertently cleared to FL280, instead of the intended FL290. Traffic (MD90 aircraft Y) was at FL280. The MD80 (aircraft X) lost separation with the MD90 (aircraft Y).

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Original NASA ASRS Text

Title: MD80 REQUESTS DSCNT TO FL280 DUE TO WX. THE CTLR INPUTS FL290 INTO COMPUTER DATABASE BUT VERBALLY CLRS MD80 TO FL280, IN CONFLICT WITH MD90.

Narrative: ACFT Y WAS ENRTE TO DFW AT FL280 ESTABLISHED ON J6 WBOUND. ACFT X WAS 12-15 NM N OF ACFT Y AT FL310 DIRECT BWG, ALSO ENRTE TO DFW. ACFT X WAS EXPERIENCING MODERATE CHOP AT FL310 AND REQUESTED DSCNT TO FL280. I DSNDED ACFT X TO WHAT I THOUGHT WAS FL290. I ENTERED FL280 INTO THE COMPUTER AS THE 'ASSIGNED' ALT AND INTENDED TO ENTER THE 'TEMPORARY ALT' OF FL290. I WENT ON AND PERFORMED SEVERAL OTHER CTL FUNCTIONS. WHILE ACFT X WAS DSNDING, I TURNED THE ACFT TO A 180 DEG HDG ATTEMPTING TO PUT ACFT X AND ACFT Y IN-TRAIL TO DFW AT FL280. I ISSUED TFC TO ACFT X AND EXPLAINED WHAT I WAS DOING. I DID NOT RECOGNIZE THE DISCREPANCY UNTIL CONFLICT-ALERT ACTIVATED. I'M NOT EXACTLY SURE WHAT COULD BE DONE TO PREVENT SIMILAR SITS IN THE FUTURE. THE ONLY CORRELATION I CAN THINK OF IS THAT I WAS TYPING FL280 INTO THE MACHINE WHILE I WAS ISSUING THE CLRNC. MY BRAIN THOUGHT FL290, BUT MY MOUTH SAID WHAT I WAS TYPING FL280. SUPPLEMENTAL INFO FROM ACN 419487: THE MD80 (ACFT X) WAS INADVERTENTLY CLRED TO FL280, INSTEAD OF THE INTENDED FL290. TFC (MD90 ACFT Y) WAS AT FL280. THE MD80 (ACFT X) LOST SEPARATION WITH THE MD90 (ACFT Y).

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.