Narrative:

Airplane #1 (aircraft X) on mustang 5 SID, restr to 10000 ft. Airplane #2 (aircraft Y) arriving from southeast via J92, descending to 11000 ft, heading 340 degrees after fmg. Aircraft #1 was turned to 330 degrees to join J92 nwbound. Aircraft #2 questioned instruction, I repeated it. At that point, pilot said 'I think you have 2 air carrier XXX on this frequency.' I then realized that both the departure and arrival data blocks were identical. In 24 yrs of ATC, I have never had 2 identical call signs in my sector. I was always told it was not possible, or that 'dupe idents' would show up somehow. Our new ARTS iie system and the NAS system permitted this to happen. I did get a 'departure message' in the data block of aircraft #1, and tower did a departure message via fdio, resulting in 'duplicate flight active,' which is the same response received when the data block is slew acknowledged by departure. I called for assistance and one aircraft was designated air carrier XXX-a. The surprise upon realizing the problem was profound. Though the closest point of approach was not a factor, this situation was potentially very serious. My workload at the time was medium (6 or 7 on frequency). I think recent computer changes have lost some of the built-in safeguards previously installed. All controllers should be warned of this dangerous possibility. Callback conversation with reporter revealed the following information: the reporter verified the incident took place. His concern is that the new ARTS iie system has lost a very important safeguard that was in place prior to this new build. The reporter was in the process of further facility investigation with management to attempt resolution.

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Original NASA ASRS Text

Title: TRACON APCH CTLR BECOMES AWARE, AS THE RESULT OF AN ACFT COMMENT, THAT 2 ACFT ARE TAGGED AND BEING RADAR TRACKED WITH THE SAME CALL SIGN.

Narrative: AIRPLANE #1 (ACFT X) ON MUSTANG 5 SID, RESTR TO 10000 FT. AIRPLANE #2 (ACFT Y) ARRIVING FROM SE VIA J92, DSNDING TO 11000 FT, HDG 340 DEGS AFTER FMG. ACFT #1 WAS TURNED TO 330 DEGS TO JOIN J92 NWBOUND. ACFT #2 QUESTIONED INSTRUCTION, I REPEATED IT. AT THAT POINT, PLT SAID 'I THINK YOU HAVE 2 ACR XXX ON THIS FREQ.' I THEN REALIZED THAT BOTH THE DEP AND ARR DATA BLOCKS WERE IDENTICAL. IN 24 YRS OF ATC, I HAVE NEVER HAD 2 IDENTICAL CALL SIGNS IN MY SECTOR. I WAS ALWAYS TOLD IT WAS NOT POSSIBLE, OR THAT 'DUPE IDENTS' WOULD SHOW UP SOMEHOW. OUR NEW ARTS IIE SYS AND THE NAS SYS PERMITTED THIS TO HAPPEN. I DID GET A 'DEP MESSAGE' IN THE DATA BLOCK OF ACFT #1, AND TWR DID A DEP MESSAGE VIA FDIO, RESULTING IN 'DUPLICATE FLT ACTIVE,' WHICH IS THE SAME RESPONSE RECEIVED WHEN THE DATA BLOCK IS SLEW ACKNOWLEDGED BY DEP. I CALLED FOR ASSISTANCE AND ONE ACFT WAS DESIGNATED ACR XXX-A. THE SURPRISE UPON REALIZING THE PROB WAS PROFOUND. THOUGH THE CLOSEST POINT OF APCH WAS NOT A FACTOR, THIS SIT WAS POTENTIALLY VERY SERIOUS. MY WORKLOAD AT THE TIME WAS MEDIUM (6 OR 7 ON FREQ). I THINK RECENT COMPUTER CHANGES HAVE LOST SOME OF THE BUILT-IN SAFEGUARDS PREVIOUSLY INSTALLED. ALL CTLRS SHOULD BE WARNED OF THIS DANGEROUS POSSIBILITY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR VERIFIED THE INCIDENT TOOK PLACE. HIS CONCERN IS THAT THE NEW ARTS IIE SYS HAS LOST A VERY IMPORTANT SAFEGUARD THAT WAS IN PLACE PRIOR TO THIS NEW BUILD. THE RPTR WAS IN THE PROCESS OF FURTHER FACILITY INVESTIGATION WITH MGMNT TO ATTEMPT RESOLUTION.

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.