ZME CTLR OBSERVES E145 DSND THROUGH ASSIGNED ALT OF FL330 AND CONFLICT WITH ENRTE DC9 AT FL310.

Narrative

ACR X WAS ISSUED DSCNT TO FL330 FROM FL350. ACR Y WAS LEVEL FL310. ACR X ACKNOWLEDGED DSCNT TO FL330; BUT DSNDED LOWER. AROUND FL320; I ASKED ACR X TO VERIFY LEVEL FL330. HE SAID 'I THOUGHT YOU ISSUED FL300' AND I SAID 'NEGATIVE.' TO TRY AND ACHIEVE SEPARATION; I ISSUED FL280 TO ACR X AND CALLED HIS TFC. I CONTINUED THE DSCNT BECAUSE ACR X WAS RAPIDLY DSNDING AND I FELT IT WAS MORE DANGEROUS TO CLB BACK TO FL330. SUPPLEMENTAL INFO FROM ACN 506443: THE CTLR SAID WE HAD 'XING TFC AT 2 O'CLOCK POS; DSND TO FL330; EXPECT FL280 AFTER XING TFC.' I THOUGHT HE SAID FL300. I PUT FL300 IN THE ALT CONTROLLER. ZME CALLED AND SAID; 'ACR X; ARE YOU LEVELING FL330?' 'NO SIR; I THOUGHT YOU SAID FL300.' CTLR SAID 'NO; I SAID FL330. DSND TO FL280 IMMEDIATELY.' I SAID; 'ROGER FL280 IMMEDIATELY.' I SAW THE 2 O'CLOCK POS TFC; A DC9 OR MD80. I SAID; 'I HAVE THE TFC IN SIGHT.' I TOLD ZME WE WOULD LEVEL OFF AND CLB BACK TO FL330. TFC CROSSED UNDER ABOUT 1500 FT AND ALSO HE SAID THEY HAD US IN SIGHT. NO TCASII FACTOR OR EVASIVE ACTION. AFTER PASSING; CTLR SAID 'DSND TO FL280; CONTACT ZME.' FACTORS: LACK OF SLEEP; FATIGUE; BAD COMS; JUDGEMENT. SUPPLEMENTAL INFO FROM ACN 506440: THE FO PUT IN THE WRONG ALT AND I DID NOT CATCH THE ERROR. BECAME AWARE OF THE ERROR; WHEN CTR ASKED IF WE WERE LEVEL AT FL330.