Narrative:

A DC10 departed off runway xxl on an initial heading of 210. An A300 departed runway xxl approximately 7 miles in trail on the same heading. Both aircraft were climbed to 13;000 ft. Due to noise abatement; both aircraft were left on the assigned heading. I recognized that DC10 was routed via ZZZ and that A300 was routed via ZZZ1. Since ZZZ1 was north of ZZZ; I elected to keep DC10 headed southwest bound until approximately 15 miles southwest of the airport before turning the aircraft direct ZZZ. This allowed me to turn A300 to a 060 heading when able direct ZZZ1 as soon as the aircraft cleared the noise abatement area. The aircraft were approximately 8-9 miles apart with routes that were divergent. I transferred DC10 to center. Shortly after this I noticed that A300 had made an extremely slow turn and was converging with DC10. The aircraft had also climbed rapidly and was at the same altitude as DC10. I asked A300 if he had the company traffic off his right side in sight. At this time the aircraft were approximately 6 miles laterally separated. The pilot took his time responding and I asked a second time. This time the pilot responded and said that he had the aircraft in sight and that he had wanted to make sure that he had the right aircraft in sight. He also said that he would maintain visual separation with the aircraft. I instructed the pilot to maintain visual separation from the other aircraft and he responded affirmatively. I waited until vertical separation was established and then transferred communication to center. Visual separation was established prior to loosing 3 miles lateral separation. Since the aircraft were not in trail at the time there was no requirement to have wake turbulence separation. In hind sight I should have kept DC10 on my frequency until I was sure that A300 had completed the turn direct ZZZ1. However; in my experience these aircraft should have never gotten closer than 5 miles. It appeared to me that the A300 was turning slower than normal and I just did not expect such a slow turn rate from the aircraft.

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Original NASA ASRS Text

Title: TRACON Controller described a near loss of separation event when transferring the two conflicting aircraft to the Center while visual separation was being conducted.

Narrative: A DC10 departed off Runway XXL on an initial heading of 210. An A300 departed Runway XXL approximately 7 miles in trail on the same heading. Both aircraft were climbed to 13;000 FT. Due to noise abatement; both aircraft were left on the assigned heading. I recognized that DC10 was routed via ZZZ and that A300 was routed via ZZZ1. Since ZZZ1 was north of ZZZ; I elected to keep DC10 headed southwest bound until approximately 15 miles southwest of the airport before turning the aircraft direct ZZZ. This allowed me to turn A300 to a 060 heading when able direct ZZZ1 as soon as the aircraft cleared the noise abatement area. The aircraft were approximately 8-9 miles apart with routes that were divergent. I transferred DC10 to Center. Shortly after this I noticed that A300 had made an extremely slow turn and was converging with DC10. The aircraft had also climbed rapidly and was at the same altitude as DC10. I asked A300 if he had the company traffic off his right side in sight. At this time the aircraft were approximately 6 miles laterally separated. The pilot took his time responding and I asked a second time. This time the pilot responded and said that he had the aircraft in sight and that he had wanted to make sure that he had the right aircraft in sight. He also said that he would maintain visual separation with the aircraft. I instructed the pilot to maintain visual separation from the other aircraft and he responded affirmatively. I waited until vertical separation was established and then transferred communication to Center. Visual separation was established prior to loosing 3 miles lateral separation. Since the aircraft were not in trail at the time there was no requirement to have wake turbulence separation. In hind sight I should have kept DC10 on my frequency until I was sure that A300 had completed the turn direct ZZZ1. However; in my experience these aircraft should have never gotten closer than 5 miles. It appeared to me that the A300 was turning slower than normal and I just did not expect such a slow turn rate from the aircraft.

Data retrieved from NASA's ASRS site as of April 2012 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.