Narrative:

2 aircraft with the same call sign was the major cause of the problem, along with ATC's failure to notify the 2 involved aircraft of the similar call signs, and ATC's failure to note that the wrong aircraft responded to a descent clearance. We were air carrier X flight, the other aircraft was air carrier Y flight. Air carrier X replied to a clearance to descend and maintain FL230. We are not sure if air carrier Y also acknowledged the same clearance. When passing through FL236, we (the air carrier X) got a TCASII TA. The TCASII display was immediately brought up and the traffic was at 10 O'clock and 5 mi, 600 ft below. We then saw the aircraft visually. ATC then asked us to verify our altitude. We told them 'descending through FL236 for FL230.' ATC pointed out the traffic, instructed us to make a right turn, and climb to FL240. We complied with all the instructions. After contacting the center supervisor after we landed, we were told that the controller did not catch the fact that we responded to the descent clearance to FL230. We asked why we were not informed of similar call signs. Supervisor said controller just failed to inform us. We may have been able to detect the EMB120 sooner if we had the TCASII display on the screen. In the rj, the TCASII is on all the time, but the display has to be selected by the pilot, which then replaces our map screen. It would be a much better EFIS system if we were able to overlay the TCASII display on our map display. If this was possible, we would have seen the EMB120 sooner, and probably would have questioned ATC.

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Original NASA ASRS Text

Title: FLC OF A CANADAIR CL65 RESPONDED TO THE WRONG CALL SIGN AND PREMATURELY DSNDED. ARTCC RADAR CTLR INTERVENED AND STOPPED THEIR DSCNT AND INSTRUCTED THEM TO GO TURN AND GO BACK DOWN TO AN INTERMEDIATE ALT.

Narrative: 2 ACFT WITH THE SAME CALL SIGN WAS THE MAJOR CAUSE OF THE PROB, ALONG WITH ATC'S FAILURE TO NOTIFY THE 2 INVOLVED ACFT OF THE SIMILAR CALL SIGNS, AND ATC'S FAILURE TO NOTE THAT THE WRONG ACFT RESPONDED TO A DSCNT CLRNC. WE WERE ACR X FLT, THE OTHER ACFT WAS ACR Y FLT. ACR X REPLIED TO A CLRNC TO DSND AND MAINTAIN FL230. WE ARE NOT SURE IF ACR Y ALSO ACKNOWLEDGED THE SAME CLRNC. WHEN PASSING THROUGH FL236, WE (THE ACR X) GOT A TCASII TA. THE TCASII DISPLAY WAS IMMEDIATELY BROUGHT UP AND THE TFC WAS AT 10 O'CLOCK AND 5 MI, 600 FT BELOW. WE THEN SAW THE ACFT VISUALLY. ATC THEN ASKED US TO VERIFY OUR ALT. WE TOLD THEM 'DSNDING THROUGH FL236 FOR FL230.' ATC POINTED OUT THE TFC, INSTRUCTED US TO MAKE A R TURN, AND CLB TO FL240. WE COMPLIED WITH ALL THE INSTRUCTIONS. AFTER CONTACTING THE CTR SUPVR AFTER WE LANDED, WE WERE TOLD THAT THE CTLR DID NOT CATCH THE FACT THAT WE RESPONDED TO THE DSCNT CLRNC TO FL230. WE ASKED WHY WE WERE NOT INFORMED OF SIMILAR CALL SIGNS. SUPVR SAID CTLR JUST FAILED TO INFORM US. WE MAY HAVE BEEN ABLE TO DETECT THE EMB120 SOONER IF WE HAD THE TCASII DISPLAY ON THE SCREEN. IN THE RJ, THE TCASII IS ON ALL THE TIME, BUT THE DISPLAY HAS TO BE SELECTED BY THE PLT, WHICH THEN REPLACES OUR MAP SCREEN. IT WOULD BE A MUCH BETTER EFIS SYS IF WE WERE ABLE TO OVERLAY THE TCASII DISPLAY ON OUR MAP DISPLAY. IF THIS WAS POSSIBLE, WE WOULD HAVE SEEN THE EMB120 SOONER, AND PROBABLY WOULD HAVE QUESTIONED ATC.

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.