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).