Narrative:

Air carrier X was level at FL240 on the sweed. SWEED2 arrival into cincinnati airport inbound to sweed intersection from henderson VOR. Indianapolis center instructed our company identification and flight number to descend and maintain fl 200. The first officer read back the clearance with our company call and flight number preceeeding the assigned altitude of fl 200. The first officer dialed the altitude of fl 200 into the MCP panel and I acknowledged the assigned altitude, and began a vertical speed descent of 1000 FPM from fl 240 to fl 200. At fl 23.7 we received a TCASII TA of an aircraft 700 ft immediately below us and drifting to our right. This was followed immediately by a RA from the TCASII. I arrested the 1000 FPM vertical descent, and we leveled between fl 23500 and 23600. At this time indianapolis center asked us what our altitude was, and we responded. Indianapolis center advised us we were then to maintain fl 240. We advised the controller he had assigned us to dscnd and maintain fl 200. The controller responded that he had assigned fl 200 to another aircraft and advised to listen up as the call signs were nowhere similar. We advised him we read back our clearance, company name and flight number, and climbed back up to fl 240. Both the copilot and myself concur in our readback and clearance, and both concur that the ATC controller assigned our flight incorrect and conflicting altitude that was meant for another aircraft.

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Original NASA ASRS Text

Title: ACR X, WRONG CALLSIGN RESPONSE, UNAUTH DSCNT FROM ASSIGNED ALT, HAD LTSS FROM ACFT BELOW.

Narrative: ACR X WAS LEVEL AT FL240 ON THE SWEED. SWEED2 ARR INTO CINCINNATI ARPT INBOUND TO SWEED INTXN FROM HENDERSON VOR. INDIANAPOLIS CTR INSTRUCTED OUR COMPANY IDENTIFICATION AND FLT NUMBER TO DSND AND MAINTAIN FL 200. THE FO READ BACK THE CLRNC WITH OUR COMPANY CALL AND FLT NUMBER PRECEEEDING THE ASSIGNED ALT OF FL 200. THE FO DIALED THE ALT OF FL 200 INTO THE MCP PANEL AND I ACKNOWLEDGED THE ASSIGNED ALT, AND BEGAN A VERT SPD DSCNT OF 1000 FPM FROM FL 240 TO FL 200. AT FL 23.7 WE RECEIVED A TCASII TA OF AN ACFT 700 FT IMMEDIATELY BELOW US AND DRIFTING TO OUR R. THIS WAS FOLLOWED IMMEDIATELY BY A RA FROM THE TCASII. I ARRESTED THE 1000 FPM VERT DSCNT, AND WE LEVELED BTWN FL 23500 AND 23600. AT THIS TIME INDIANAPOLIS CTR ASKED US WHAT OUR ALT WAS, AND WE RESPONDED. INDIANAPOLIS CTR ADVISED US WE WERE THEN TO MAINTAIN FL 240. WE ADVISED THE CTLR HE HAD ASSIGNED US TO DSCND AND MAINTAIN FL 200. THE CTLR RESPONDED THAT HE HAD ASSIGNED FL 200 TO ANOTHER ACFT AND ADVISED TO LISTEN UP AS THE CALL SIGNS WERE NOWHERE SIMILAR. WE ADVISED HIM WE READ BACK OUR CLRNC, COMPANY NAME AND FLT NUMBER, AND CLBED BACK UP TO FL 240. BOTH THE COPLT AND MYSELF CONCUR IN OUR READBACK AND CLRNC, AND BOTH CONCUR THAT THE ATC CTLR ASSIGNED OUR FLT INCORRECT AND CONFLICTING ALT THAT WAS MEANT FOR ANOTHER ACFT.

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.