Narrative:

Aircraft X was on the shfty arrival to rsw and was descended to 4;000 feet; pilot reported coming within an estimated 300 feet of aircraft Y. At the time that this occurred I was occupied with other aircraft; so the report from aircraft X was received about 12 miles after the occurrence. I did observe a primary target that I believe was aircraft Y at the time of the report but I do not recall seeing the primary target at the time of the occurrence; primary targets can be difficult to notice and workload distracted me to some degree. The problem here; in my opinion; is this occurs very frequently in this area and may be filtered out in the controllers mind. Many controllers that I have spoken to have confessed that because of the frequency of false primary targets throughout the airspace they often find themselves taking primary targets less seriously than they should. Additionally; having a STAR that routes aircraft directly through a notamed area creates built in conflict. I have also learned since the occurrence that the aircraft Y pilot actually had a transponder onboard; squawking 1202 and mode C; this was however not seen by our radar nor the aircraft X pilots TCAS. A briefing item has already been disseminated to controllers here to use extreme caution for primary targets in the airspace; specifically in the notamed area; I think this will be helpful. I think the only other possible actions that could be taken would be 1.) moving the area where the non controlled aircraft operate. 2.) adjusting the radar to be more accurate as far as distinguishing between actual primary targets and false primary targets to avoid controllers possibly filtering out primary targets in their mind. 3.) request transponders on the non-controlled and learn why aircraft Y's transponder was not operating correctly. Not entirely sure how feasible any of these recommendations are.

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Original NASA ASRS Text

Title: RSW Controller reports that an air carrier had a NMAC with an aircraft that the Controller did not see on the radar.

Narrative: Aircraft X was on the SHFTY arrival to RSW and was descended to 4;000 feet; pilot reported coming within an estimated 300 feet of Aircraft Y. At the time that this occurred I was occupied with other aircraft; so the report from Aircraft X was received about 12 miles after the occurrence. I did observe a primary target that I believe was Aircraft Y at the time of the report but I do not recall seeing the primary target at the time of the occurrence; primary targets can be difficult to notice and workload distracted me to some degree. The problem here; in my opinion; is this occurs very frequently in this area and may be filtered out in the controllers mind. Many controllers that I have spoken to have confessed that because of the frequency of false primary targets throughout the airspace they often find themselves taking primary targets less seriously than they should. Additionally; having a STAR that routes aircraft directly through a NOTAMed area creates built in conflict. I have also learned since the occurrence that the Aircraft Y pilot actually had a transponder onboard; squawking 1202 and Mode C; this was however not seen by our radar nor the Aircraft X pilots TCAS. A briefing item has already been disseminated to controllers here to use extreme caution for primary targets in the airspace; specifically in the NOTAMed area; I think this will be helpful. I think the only other possible actions that could be taken would be 1.) Moving the area where the non controlled aircraft operate. 2.) Adjusting the radar to be more accurate as far as distinguishing between actual primary targets and false primary targets to avoid controllers possibly filtering out primary targets in their mind. 3.) Request transponders on the non-controlled and learn why Aircraft Y's transponder was not operating correctly. Not entirely sure how feasible any of these recommendations are.

Data retrieved from NASA's ASRS site 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.