Date: 201211
Local time of day: 0001-0600
Location: SAV.Airport, GA
Aircraft: DA42 Twin Star
Operator: Personal
Operating under: Part 91
Flight plan: IFR
Flight phase: Initial Climb
Airspace: Class C SAV
ATC / advisory: TRACON SAV
Reporter organization: Government
Reporter function: Approach; Departure
Reporter qualification: Air Traffic Control Fully Certified
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
Result: General None Reported / Taken
Contributing factors: ATC Equipment / Nav Facility / Buildings
Primary problem: ATC Equipment / Nav Facility / Buildings

Narrative: I got a call saying ZJX would not assume Savannah airspace due to an overdue aircraft that could not be located. The caller stated they had not talked to the aircraft and he was instructed to conduct a ramp search. Meanwhile; he attempted an aircraft history search which was not working. He said there was no aircraft with the call sign worked by SAV however; earlier there had been a DA42 similar flight plan and type. The two controllers who had been working at the time were contacted and neither had issued any clearance or spoke to the aircraft. I called ZJX and they agreed to take the airspace. I got another call later indicating that the count operations aircraft locator did show that the DA42 had acquired and then dropped into 'coast' 10 miles east of SAV airport and then disappeared after a few minutes. I called ZJX and ask them to start an Alert on the DA42. ZJX Operations Manager in Charge (OMIC) said he had already done so when JAX Approach reported the aircraft overdue. He showed the track was never handed off to ZJX and that the aircraft call sign did not exist in the registry. Both positions were received with no contact with indicated on either position. I looked at the Normal Operating Procedures (NOP) and the beacon appeared approximately 10 miles east of SAV and tagged up as the DA42. The track was consistent with the duplicate beacon problems that we have been experiencing for several months. (180 degrees out along the opposite final; same distance and altitude; similar beacon code) There was a 'real' aircraft 10 miles west at 3;000 FT which was in that position: One aircraft Code XXXX; vs. the DA42 Code XXYX. This would indicate a more significant problem created by the duplicate beacons which needs to be elevated within Tech Ops. Apparently; if an assigned beacon code is displayed when the Mode S- ARTS creates a false target that aircraft will tag up and become active in the National Airspace System (NAS). This can be very confusing and time consuming for the controllers to handle while working live traffic. A flight plan pending anywhere in Savannah airspace could automatically acquire via the Mode S and ARTS based on erroneous information displayed on the scope. This would result in the 'DM' departure message being sent and the flight plan activated. This will require action on our part to fix a flight plan and divert attention from real aircraft. Furthermore; if this information is displayed to pilots via the TIS feature of the Mode S then other aircraft may see erroneous targets which may pose a threat and they may take action which may results in an unfavorable maneuver; TCAS RA event or pilot deviation. The situation with duplicate beacon codes being displayed has been on going for several months without solution. Tech Ops is aware of this problem and has been unable to solve it. A 'patch' was installed which was supposed to remedy the problem. This did not occur. This event could easily be repeated and aggravated by the same factors which occurred here. Tech Ops must have a subject matter expert look into this. We must have a final solution to this problem before another situation develops.




Synopsis: SAV Controller described an unsafe equipment condition with regard to an overdue aircraft and difficulty in trying to secure recorded information from existing the RADAR equipment because of duplicate beacon codes.