2010-08 · NASA ASRS report 904334
SDF Controllers described a loss of separation event occurring shortly after final positions were decombined; the controller working the combined positions electing to retain the conflicting traffic on his/her frequency.
I was working FR1/FR2. In the decombination briefing I gave up the East Final (FR2) and kept the West Final (FR1). The traffic portion of the decombination briefing included a B757 on visual approach for Runway 35R at 3;000 FT already talking to the Tower; with the SH33 on a base leg heading of 255 degrees at 4;000 FT; setting him up to follow the B757. The SH33 did not yet have the traffic in sight to follow him. The A306 was on the final for Runway 35L at 4;000 FT; cleared on the ILS Approach. The positions were decombined at this point; and I failed to realize that SH33 needed to be switched to the East Final Frequency. I went back to working the rest of my aircraft on the west side. The East Final Controller asked me if SH33 was turning to join the localizer for 35R; and it was then that I realized my mistake. The SH33 was at the same altitude as the A306; and even though his heading was such that he would pass behind the A306; there would not have been appropriate wake turbulence separation with the small behind the large. I called the traffic to the SH33; who had the A306 in sight and maintained visual separation; and then cleared him on the visual approach to Runway 35R. I then called the traffic to A306; who had the SH33 in sight and maintained visual separation on their respective final approach course. I should have ensured that the frequency change was completed after the briefing that would have saved all the trouble of this incident. I would like to point out that the Collision Alert alarm never did go off; [which] would also have drawn my attention to the developing situation.
I had just opened the East Final RADAR position (FR2) from being combined at the West Final RADAR (FR1) position. The B757 was on FR1 localizer while the SH33 was on a vector from the east. The Controller at FR1 asked me to take a point out on SH33 since he was within 6 miles of the localizer for the east runway. There was no sense trying to switch SH33 frequency that close to needing a turn. As the SH33 got closer to the A306 at 12 o'clock and 4 miles; I alerted the Controller at FR1. That Controller then addressed another aircraft rather than SH33. I could only assume he had not heard me; so I alerted him again. He immediately issued a turn to the SH33 and pointed out traffic. The SH33 reported the B757 in sight and was instructed to maintain visual separation. By that time; it appeared the separation had been lost. Recommendation; this occurred within minutes of decombining the Final RADAR positions. Had the Controller on FR1 switched the SH33 to me to work; rather than a point out; that would have been the only aircraft I was talking to. The Controller on FR1 was talking to approximately 6 aircraft at the time. I believe that that FR1 Controller simply got distracted by other aircraft on his frequency and forgot to turn and/or descend the SH33.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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