Narrative:

Working arrival sectors combined during evening arrival push. Very busy with multiple IFR inbounds as well as VFR advisory services. I did not notice the conflict between aircraft X and the VFR target until the conflict alert sounded. I issued a traffic alert; although it was late and I mixed up the appropriate order of the phraseology. It was all I could do at that point. Nuw approach later called for a point-out on a VFR target that I believed was involved in this occurrence; so I asked the controller for the call sign and they identified the aircraft as aircraft Y. I asked the nuw controller to pass along that the aircraft had flown outbound along an active approach course for bfi and that such actions are not necessarily the safest way to operate. Falcon indicated the closest proximity between aircraft X and the first VFR target was 0.46 miles laterally and 600 feet vertically. As aircraft X continued down the localizer the next VFR target which the conflict alert sounded for passed within 0.44 NM laterally and 700 feet vertically. Aircraft X spent at least 4 miles of the last 11 miles the aircraft flew in a conflict alert status with a target nearby.something needs to change. The VFR aircraft are transiting a very narrow; busy corridor of airspace and are doing so without any communication with ATC. It is simply unsafe. The VFR aircraft in this area at the very least need to be in communication with ATC so that we can assign; as necessary; altitude restrictions ensuring the safety of all the aircraft involved. The solutions are not hard and while they are potentially more restrictive to VFR aircraft the bottom line is that what happens day in and day out in that airspace as it exists and operates now will eventually result in a very bad accident.

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Original NASA ASRS Text

Title: S46 TRACON Controller reported an aircraft on final approach for BFI conflicted with VFR aircraft transiting the approach course not in communication with ATC.

Narrative: Working arrival sectors combined during evening arrival push. Very busy with multiple IFR inbounds as well as VFR advisory services. I did not notice the conflict between Aircraft X and the VFR target until the Conflict Alert sounded. I issued a traffic alert; although it was late and I mixed up the appropriate order of the phraseology. It was all I could do at that point. NUW approach later called for a point-out on a VFR target that I believed was involved in this occurrence; so I asked the controller for the call sign and they identified the aircraft as Aircraft Y. I asked the NUW controller to pass along that the aircraft had flown outbound along an active approach course for BFI and that such actions are not necessarily the safest way to operate. FALCON indicated the closest proximity between Aircraft X and the first VFR target was 0.46 miles laterally and 600 feet vertically. As Aircraft X continued down the localizer the next VFR target which the Conflict Alert sounded for passed within 0.44 NM laterally and 700 feet vertically. Aircraft X spent at least 4 miles of the last 11 miles the aircraft flew in a Conflict Alert status with a target nearby.Something needs to change. The VFR aircraft are transiting a very narrow; busy corridor of airspace and are doing so without any communication with ATC. It is simply unsafe. The VFR aircraft in this area at the very least need to be in communication with ATC so that we can assign; as necessary; altitude restrictions ensuring the safety of all the aircraft involved. The solutions are not hard and while they are potentially more restrictive to VFR aircraft the bottom line is that what happens day in and day out in that airspace as it exists and operates now will eventually result in a very bad accident.

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.