Narrative:

Birmingham approach control airspace is situated at the edge of ZTL airspace. We interface directly with ZME and with 3 approach control facilities under ZME. ZTL sits between ZME and ZJX. ZME and ZJX share several beacon code banks. As a result of this sharing of beacon code banks, and our position abutting ZME airspace, it is possible for 2 aircraft assigned the same beacon code to be headed toward birmingham airspace at the same time. Recently, I received an automated handoff from ZTL on a track headed sbound toward birmingham airspace from ZME airspace. I accepted the handoff. However, the actual aircraft to which the track corresponded was northbound toward birmingham. In other words, the aircraft I was talking to was not the track I was working. As a result, I descended the actual aircraft into adjacent birmingham airspace without permission. This was able to happen because both of the aircraft were assigned the same beacon code. One beacon code was assigned by ZME and the other by ZJX. Since only 1 track may be assigned any 1 beacon code in any center's airspace, one of the tracks would have to be reassigned a new beacon code. But since the birmingham ASR-9 radar began tracking the target further out than we talk to the aircraft, a new beacon code was not assigned in time to prevent the automated track from tagging on the wrong aircraft. Since only 1 track in the birmingham stars database can be assigned any 1 beacon code, the radar will tag the first track it sees transmitting that particular beacon code, even if it is the wrong aircraft. This is a recurring problem.

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Original NASA ASRS Text

Title: BHM CTLR EXPRESSED CONCERN REGARDING STARS SOFTWARE AND DUPLICATE BEACON CODE ASSIGNMENTS TO ARR ACFT RESULTING IN AIRSPACE DEV.

Narrative: BIRMINGHAM APCH CTL AIRSPACE IS SITUATED AT THE EDGE OF ZTL AIRSPACE. WE INTERFACE DIRECTLY WITH ZME AND WITH 3 APCH CTL FACILITIES UNDER ZME. ZTL SITS BTWN ZME AND ZJX. ZME AND ZJX SHARE SEVERAL BEACON CODE BANKS. AS A RESULT OF THIS SHARING OF BEACON CODE BANKS, AND OUR POS ABUTTING ZME AIRSPACE, IT IS POSSIBLE FOR 2 ACFT ASSIGNED THE SAME BEACON CODE TO BE HEADED TOWARD BIRMINGHAM AIRSPACE AT THE SAME TIME. RECENTLY, I RECEIVED AN AUTOMATED HDOF FROM ZTL ON A TRACK HEADED SBOUND TOWARD BIRMINGHAM AIRSPACE FROM ZME AIRSPACE. I ACCEPTED THE HDOF. HOWEVER, THE ACTUAL ACFT TO WHICH THE TRACK CORRESPONDED WAS NBOUND TOWARD BIRMINGHAM. IN OTHER WORDS, THE ACFT I WAS TALKING TO WAS NOT THE TRACK I WAS WORKING. AS A RESULT, I DSNDED THE ACTUAL ACFT INTO ADJACENT BIRMINGHAM AIRSPACE WITHOUT PERMISSION. THIS WAS ABLE TO HAPPEN BECAUSE BOTH OF THE ACFT WERE ASSIGNED THE SAME BEACON CODE. ONE BEACON CODE WAS ASSIGNED BY ZME AND THE OTHER BY ZJX. SINCE ONLY 1 TRACK MAY BE ASSIGNED ANY 1 BEACON CODE IN ANY CTR'S AIRSPACE, ONE OF THE TRACKS WOULD HAVE TO BE REASSIGNED A NEW BEACON CODE. BUT SINCE THE BIRMINGHAM ASR-9 RADAR BEGAN TRACKING THE TARGET FURTHER OUT THAN WE TALK TO THE ACFT, A NEW BEACON CODE WAS NOT ASSIGNED IN TIME TO PREVENT THE AUTOMATED TRACK FROM TAGGING ON THE WRONG ACFT. SINCE ONLY 1 TRACK IN THE BIRMINGHAM STARS DATABASE CAN BE ASSIGNED ANY 1 BEACON CODE, THE RADAR WILL TAG THE FIRST TRACK IT SEES XMITTING THAT PARTICULAR BEACON CODE, EVEN IF IT IS THE WRONG ACFT. THIS IS A RECURRING PROB.

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.