Narrative:

Aircraft X departed and was assigned runway heading initially. Aircraft Y departed next and was given a turn off the ground to a 040 heading as the wind was strong out of the northwest and eastbound departures were climbing well over the adjacent runway conflict area. I ran aircraft X approximately 2 miles off of the departure end prior to turning them right to a 360 heading and shipping them to departure. They probably dragged about another mile west in the turn. Meanwhile aircraft Y turned extremely slow and slopped their turn out underneath aircraft X. I attempted to get aircraft Y to turn tighter or really do anything at all but they had left the frequency. I'm not sure how close they were but I'm sure I did not have IFR separation. Aircraft Y should have been easily inside aircraft X on the turn. I intentionally let aircraft X go out a little before I turned them so I didn't cut myself out.I had shipped aircraft X because I had; or thought I had aircraft Y still on my frequency and that I was applying visual separation. While I was trying to get aircraft Y to turn; the TRACON departure controller called and said aircraft Y had switched on his own and he was stopping him at 4000 ft. At this point aircraft X was right on top of him and I think I saw his altitude reading as 4600 ft with aircraft Y leveling at 4000 ft. The conflict alert may or may not have gone off but I don't think it did. I keep thinking about it and there may have been 'red on the scope' as the two targets were merging; perhaps right when the departure controller was calling. I am absolutely positive that the conflict alert aural alarm did not go off anywhere in the cab. As of the writing of this report I have not reviewed video or audio replay of this event and this narrative is an honest accounting of my recollection of the event.

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Original NASA ASRS Text

Title: ORD Tower Controller in training reported a loss of separation after an aircraft that had switched frequencies turned slower than anticipated.

Narrative: Aircraft X departed and was assigned runway heading initially. Aircraft Y departed next and was given a turn off the ground to a 040 heading as the wind was strong out of the Northwest and eastbound departures were climbing well over the adjacent runway conflict area. I ran Aircraft X approximately 2 miles off of the departure end prior to turning them right to a 360 heading and shipping them to departure. They probably dragged about another mile west in the turn. Meanwhile Aircraft Y turned extremely slow and slopped their turn out underneath Aircraft X. I attempted to get Aircraft Y to turn tighter or really do anything at all but they had left the frequency. I'm not sure how close they were but I'm sure I did not have IFR separation. Aircraft Y should have been easily inside Aircraft X on the turn. I intentionally let Aircraft X go out a little before I turned them so I didn't cut myself out.I had shipped Aircraft X because I had; or thought I had Aircraft Y still on my frequency and that I was applying visual separation. While I was trying to get Aircraft Y to turn; the TRACON Departure Controller called and said Aircraft Y had switched on his own and he was stopping him at 4000 ft. At this point Aircraft X was right on top of him and I think I saw his altitude reading as 4600 ft with Aircraft Y leveling at 4000 ft. The conflict alert may or may not have gone off but I don't think it did. I keep thinking about it and there may have been 'red on the scope' as the two targets were merging; perhaps right when the Departure Controller was calling. I am absolutely positive that the conflict alert aural alarm did not go off anywhere in the cab. As of the writing of this report I have not reviewed video or audio replay of this event and this narrative is an honest accounting of my recollection of the event.

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.