Narrative:

Aircraft X level at 5000 assigned heading 200. Aircraft Y level at 4000 assigned heading 290. Aircraft approximately 2.5 NM lateral separation. Both pilots issued and acknowledged traffic calls. At the point that I believe the courses crossed; aircraft X was issued a descent clearance to 3000. Crossing course criteria established. Aircraft X was in front and was the faster aircraft (a twin jet compared to a single piston). Showed 2.5 miles for several sweeps after descent clearance was issued. It wasn't until a point that I would estimate to be a full 1-2 miles past the crossing point that finally showed no crossing courses. I was surprised it took the computer that long to go to no crossing courses. I imagine if the only official separation tool in hindsight is some type of snitch function out of the facility; the paperwork will show less than 3 miles and 1000 ft for approximately 15 seconds until no crossing courses was determined by the snitch.before tarp (traffic analysis and review program); a controller determined when crossing course minima was established. This is subjective really since most crossing courses have no fixes to determine the exact point when courses officially cross (unless you're crossing at a VOR or such fix). In today's world though; tarp determines this point as far as I know in hindsight and with technology we don't have access to in a live TRACON. Seems like that needs resolved somehow legally through natca?

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Original NASA ASRS Text

Title: Omaha TRACON Controller reported a problem with crossing course criteria and a possible loss of separation. The Controller did not like that the FAA has a tool to determine crossing course after the fact.

Narrative: Aircraft X level at 5000 assigned heading 200. Aircraft Y level at 4000 assigned heading 290. Aircraft approximately 2.5 NM lateral separation. Both pilots issued and acknowledged traffic calls. At the point that I believe the courses crossed; Aircraft X was issued a descent clearance to 3000. Crossing course criteria established. Aircraft X was in front and was the faster aircraft (a twin jet compared to a single piston). Showed 2.5 miles for several sweeps after descent clearance was issued. It wasn't until a point that I would estimate to be a full 1-2 miles past the crossing point that finally showed no crossing courses. I was surprised it took the computer that long to go to no crossing courses. I imagine if the only official separation tool in hindsight is some type of snitch function out of the facility; the paperwork will show less than 3 miles and 1000 ft for approximately 15 seconds until no crossing courses was determined by the snitch.Before TARP (Traffic Analysis and Review Program); a controller determined when crossing course minima was established. This is subjective really since most crossing courses have no fixes to determine the exact point when courses officially cross (unless you're crossing at a VOR or such fix). In today's world though; TARP determines this point as far as I know in hindsight and with technology we don't have access to in a live TRACON. Seems like that needs resolved somehow legally through NATCA?

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.