Cessna 402/402C/B379 Businessliner/Utiliner
Air Traffic Control Fully Certified
Distraction; Situational Awareness
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance
Human Factors; Airspace Structure
I was working arrival combined RADAR positions. The traffic was light; while arrival was very busy. I was vectoring a sequence of about 8 aircraft when one of the last aircraft; Aircraft Z; asked me if I was showing two transponders active on his aircraft. He said that a previous Controller had told him they were picking up two tracks on him. I replied that everything looked normal and continued working. Shortly after; I heard the Conflict Alert (CA) going off and noticed that Aircraft Z was now showing two transponders that were resulting in the CA. I advised him of the issue and continued working. A minute or two later; still working the busy sequence; I heard the Conflict Alert again and immediately looked to Aircraft Z; and again; the CA was a result of his dual transponders. At about this time someone else in the room who was watching commented 'Is that really happening?' and I replied 'It's just a second transponder onboard; the pilot is aware of the issue.' Then the person said 'No; I mean over there; pointing!' At the exact same time as Aircraft Z's CA was going off; a second CA had begun to sound for two IFR aircraft in my airspace merging at 070. It was Aircraft Y indicating 110 or 120 knots followed about a mile away by Aircraft X indicating around 170 knots. Upon being made aware of the situation I told Aircraft X to turn left immediately and issued traffic. I also issued traffic to Aircraft Y. Closest proximity was 0.6 miles; same altitude. This was a busy arrival sequence; likely the busiest that I have personally worked in years. I allowed myself to succumb to tunnel vision; and focused mainly on the arrival airspace; which is 50 miles away from the bulk of my airspace. I should have requested help from the watch supervisor; either a split or a coordinator; but the situation in AR airspace escalated so quickly I didn't have any time to do so.
TRACON Controller described a conflict event when failing to note a developing conflict in part of his airspace after being distracted by a 'CA self conflict; two transponders on one aircraft' event in another area.