Narrative:

While working local control north; landing RWY9L on east flow; I encountered a situation where aircraft X was catching up to aircraft Y that had been previously cleared to land. The separation between those 2 aircraft decreased to about 2 miles and I still was not talking to aircraft X. While focused on that; a different aircraft; aircraft Z called my frequency on about a 7 or 8 mile final; which would put them close to schaumburg airport. I advised aircraft Z to 'continue' not realizing that he was about to inquire about the VFR target below them and about a mile in front of them. When they pointed out the target to me I exchanged a brief traffic call but aircraft Z was already responding to an RA. I asked them to advise when they could continue the approach. The VFR target mode C displayed 2200/2300 feet while aircraft Z was level at 3000 feet. Aircraft Z said that their TCAS showed the VFR target only 300 feet below them and climbing. As this all was happening; I still had yet to rectify the two aircraft that were inside the FAF with reduced separation. Everyone continued and landed without incident. There is a chronic problem of C90 jamming arrivals on visual approaches and giving less than the adequate amount of spacing on final. What made this an even bigger issue was the fact that I was not talking to aircraft X who was getting too close to aircraft Y; so my focus was on working from the airport and out on my final. I don't know why aircraft Z was on my frequency; outside of my airspace; without all conflicts being resolved in C90 airspace. I don't fault the TRACON too much regarding this because the airspace allows runway 9L arrivals down to 3000 feet with VFR aircraft coming off of schaumburg airport directly below the 9L final. This is an airspace issue.C90 could do a better job of providing spacing on final that doesn't require the use of unsafe s-turns or rapid reductions/accelerations of airspeed. It seems that C90 believes that our 'yes' in the visual separation box allows them to jam all of their arrivals and leaves it up to us to 'make it work'.

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Original NASA ASRS Text

Title: A VFR aircraft climbed into ORD Class B without a clearance. An arriving aircraft reported a TCAS alert with the traffic.

Narrative: While working Local Control North; landing RWY9L on East Flow; I encountered a situation where Aircraft X was catching up to Aircraft Y that had been previously cleared to land. The separation between those 2 aircraft decreased to about 2 miles and I still was not talking to Aircraft X. While focused on that; a different aircraft; Aircraft Z called my frequency on about a 7 or 8 mile final; which would put them close to Schaumburg Airport. I advised Aircraft Z to 'continue' not realizing that he was about to inquire about the VFR target below them and about a mile in front of them. When they pointed out the target to me I exchanged a brief traffic call but Aircraft Z was already responding to an RA. I asked them to advise when they could continue the approach. The VFR target Mode C displayed 2200/2300 feet while Aircraft Z was level at 3000 feet. Aircraft Z said that their TCAS showed the VFR target only 300 feet below them and climbing. As this all was happening; I still had yet to rectify the two aircraft that were inside the FAF with reduced separation. Everyone continued and landed without incident. There is a chronic problem of C90 jamming arrivals on visual approaches and giving less than the adequate amount of spacing on final. What made this an even bigger issue was the fact that I was not talking to Aircraft X who was getting too close to Aircraft Y; so my focus was on working from the airport and out on my final. I don't know why Aircraft Z was on my frequency; outside of my airspace; without all conflicts being resolved in C90 airspace. I don't fault the TRACON too much regarding this because the airspace allows Runway 9L arrivals down to 3000 feet with VFR aircraft coming off of Schaumburg Airport directly below the 9L final. This is an airspace issue.C90 could do a better job of providing spacing on final that doesn't require the use of unsafe S-turns or rapid reductions/accelerations of airspeed. It seems that C90 believes that our 'Yes' in the visual separation box allows them to jam all of their arrivals and leaves it up to us to 'make it work'.

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.