ALTDEV ALT OVERSHOT IN DSCNT. CLRNC INTERP READBACK HEARBACK PROB.

Narrative

ZAU; ON FREQ 132.22; INSTRUCTED OUR ACFT TO DSND TO FL350; 'EXPEDITE THROUGH FL370' ON A HDG OF 330 DEGS FOR THE DSCNT. IN ORDER TO INCREASE OUR NORMAL RATE OF DSCNT; AS REQUESTED BY THE CTLR; I MANUALLY INTERVENED ON THE MCP IAS/MACH WINDOW TO INCREASE OUR NORMAL DSCNT SPD; THEREBY INCREASING THE ACFT'S RATE OF DSCNT. A SHORT TIME LATER; THE CTLR ASKED WHAT ALT WE WERE DSNDING THROUGH. THE CAPT REPLIED THAT WE WERE DSNDING THROUGH FL380. THE CTLR THEN IMMEDIATELY ISSUED A HDG CHANGE TO 290 DEGS. AT THIS TIME THE FREQ WAS VERY BUSY AND CONGESTED. THE CTLR WAS ISSUING NUMEROUS INSTRUCTIONS TO OUR ACFT AND OTHERS ON THE FREQ IN A VERY SHORT TIME PERIOD. THE CTLR THEN INSTRUCTED US TO; WHAT WE THOUGHT TO BE AT THAT TIME; A DSCNT TO FL290. THE CAPT ACKNOWLEDGED THE DSCNT ON THE RADIO AND I ENTERED 29000 INTO THE ALT WINDOW OF THE MCP. THE CAPT VERIFIED MY ENTRY AND ENTERED FL290 INTO THE CRZ ALT SPACE OF THE FMC CRZ PAGE. DSNDING THROUGH APPROX FL320 THE CTLR INSTRUCTED US TO CLB BACK TO FL350 AND TURN R TO A HDG OF 010 DEGS. THE CAPT INFORMED THE CTLR THAT OUR PREVIOUS CLRNC WAS TO DSND TO FL290. THE CTLR THEN TOLD US THAT HE HAD WANTED US TO TURN TO A HDG OF 290 DEGS; NOT DSND TO FL290; AND THEN INSTRUCTED US TO CONTINUE OUR TURN TO 030 DEGS.