Light Transport
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 4.0
Situational Awareness
ATC Issue All Types; Conflict NMAC; Deviation / Discrepancy - Procedural Published Material / Policy
Procedure; Human Factors; Company Policy
I assigned Aircraft X heading 330; altitude 2500 feet on a modified base turn for a Visual Approach ahead of Aircraft Y who was being vectored for the straight-in ILS at 3000 feet. Aircraft X did not have the field in sight as he was approaching the final approach course. I told him there was a change of plans and reiterated the heading and altitude as he crossed the final approach course; and I prepared to vector him for re-sequence. Meanwhile I cleared Aircraft Y for the ILS approach. I've replayed this event multiple times and it seems to confirm exactly what I was attempting to do. At the last point prior to Aircraft X crossing over the localizer and Aircraft Y's flight path there was 4 miles separation. At the first definitive point after flight paths had crossed; 3.68 miles separation existed. Course divergence was 110 degrees. As a result; eventually lateral separation diminished to about 1.5nm at its closest. Aircraft X was not vectored again until lateral separation was established. To me this was textbook 7110.65 5-5-7 Passing or Diverging. My facility Quality Assurance office has determined this is a loss of separation and NMAC. A traffic call may have been warranted.
ZSU Controller reported a loss of separation and an NMAC even though they complied with the rules in the FAAH 7110.65.