Narrative:

I had taken a handoff from wooly sector with VFR aircraft Y when he was 9-10 miles to the northwest of bwi. When he checked in I told him to proceed direct to [our hospital] and that there were going to be departures off of runway 28. I had quite a few departures that were lined up at the end of the runway. I had departed a few B737 and they had been climbing well and over where aircraft Y would be crossing the extended center line of runway 28. After clearing aircraft X for takeoff I called traffic to aircraft Y when aircraft X was rolling midfield to be safe. Aircraft Y said that they were looking for the traffic. I saw that aircraft X was not climbing like the previous departures. After aircraft X was airborne I then told him the traffic and he also said that he was looking. I saw the traffic outside and saw that they were getting closer and they both did not have [each other] in sight. I continued to call the traffic to both aircraft giving them updates on their current location. After doing another traffic call aircraft Y said that they had seem them. At that point aircraft Y was still at 2500-2600 feet and aircraft X was around 2100. I observed aircraft X turning north to advert away from the traffic. Aircraft X then said that they were turning back on course and that they had a resolution advisory (RA); and he was still climbing. At that point they were past each other and were no longer a factor. I told aircraft X to contact potomac. Aircraft Y continued south bound towards his destination and was handed off back to pct.be more aware of aircraft performance.

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Original NASA ASRS Text

Title: BWI Controller and airline pilot report of a NMAC. Controller thought climb rate would be better for the air carrier based on previous departures. Once the pilot acquired the aircraft visually; a turned was made to avoid it.

Narrative: I had taken a handoff from Wooly Sector with VFR Aircraft Y when he was 9-10 miles to the NW of BWI. When he checked in I told him to proceed direct to [our hospital] and that there were going to be departures off of runway 28. I had quite a few departures that were lined up at the end of the runway. I had departed a few B737 and they had been climbing well and over where Aircraft Y would be crossing the extended center line of runway 28. After clearing Aircraft X for takeoff I called traffic to Aircraft Y when Aircraft X was rolling midfield to be safe. Aircraft Y said that they were looking for the traffic. I saw that Aircraft X was not climbing like the previous departures. After Aircraft X was airborne I then told him the traffic and he also said that he was looking. I saw the traffic outside and saw that they were getting closer and they both did not have [each other] in sight. I continued to call the traffic to both aircraft giving them updates on their current location. After doing another traffic call Aircraft Y said that they had seem them. At that point Aircraft Y was still at 2500-2600 feet and Aircraft X was around 2100. I observed Aircraft X turning north to advert away from the traffic. Aircraft X then said that they were turning back on course and that they had a Resolution Advisory (RA); and he was still climbing. At that point they were past each other and were no longer a factor. I told Aircraft X to contact Potomac. Aircraft Y continued south bound towards his destination and was handed off back to PCT.Be more aware of aircraft performance.

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.