Narrative:

Aircraft X was being vectored by the previous controller north of omaha eppley airport to stay clear of numerous arrivals into omaha. I took the position amidst a fairly complex scenario involving BE99's; both IFR and VFR; a mooney that needed to go south by southeast to mle; and I believe even a jet or two. There was a C208 inbound to oma and also a very slow C150 on an IFR flight plan over-flying the general area northwest bound from council bluffs (cbf). After I took the position; the controller being relieved stayed on to watch and make sure I had the picture. He was a big help in making sure I had the flick; and stayed well past the required 2 minutes. At one point; air carrier Y inbound from the northwest called the field in sight. He had been given a discretionary descent to 30. Once it was appropriate; and separation was ensured from preceding traffic; I cleared him for the approach. At about the same time; the relieved controller told me that it looked good to turn aircraft X off his 270 degree heading back to mle; on course; which was approximately a 170 heading. He was still at 6000. It sounded good to me; and I turned him on course; believing that he would pass well behind air carrier Y; who was descending through 5700 feet when I cleared him. (I think). At one point; I saw that that was not going to work; and I wouldn't have the required separation; so I turned aircraft X back to the right to a 230 heading. He acknowledged the turn. I was watching the situation; and it didn't seem he was taking the turn; so I issued it again; and again he read it back. This time he started the turn... Slowly. When I issued the turn the first time; he was approximately 5 miles from the BE99 (air carrier Y). By the time he started his turn after acknowledging a second time; he was approximately 4 miles away. At this point; the supervisor on duty asked me what was going on with aircraft X and air carrier Y. I told him I was on top of it and had issued a turn to the mooney. At this point the only thing I could do was watch; as the mooney made his turn. The closest I ever saw the 2 targets was 2.89 miles; and approximately 600 feet vertical separation. I believe I had the required separation; because by the time I lost 3 miles; the mooney was diverged at least 30-40 degrees and vectored behind air carrier Y. Recommendation; we have had issues with air carrier Y pilots of late. They are kind of wild; in that you never know what to expect from them. They seem to fly by the seat of their pants; and often get frustrated by being made number 2 or 3. They often offer to cancel IFR believing it will improve their number in the sequence. When I cleared air carrier Y for the visual approach; he seemed to slow his descent rate dramatically. Or it just could have been my perception. Either way; I should have used my own judgment before issuing a turn direct mle for aircraft X instead of relying on another controllers opinion. Also; I should have paid more attention to the descent rate of air carrier Y. I could have gotten on the pilot and made sure he continued his descent. Good supervision and relief briefings are important as well; but I don't believe they were a factor here.

Related reports:

Google
 

Original NASA ASRS Text

Title: R90 controller experienced a proximity event when turning a departure on course; at the suggestion of the relieved controller; only to note a cut off situation with another aircraft was developing.

Narrative: Aircraft X was being vectored by the previous controller north of Omaha Eppley airport to stay clear of numerous arrivals into Omaha. I took the position amidst a fairly complex scenario involving BE99's; both IFR and VFR; a Mooney that needed to go south by southeast to MLE; and I believe even a jet or two. There was a C208 inbound to OMA and also a very slow C150 on an IFR flight plan over-flying the general area northwest bound from Council Bluffs (CBF). After I took the position; the Controller being relieved stayed on to watch and make sure I had the picture. He was a big help in making sure I had the flick; and stayed well past the required 2 minutes. At one point; Air Carrier Y inbound from the northwest called the field in sight. He had been given a discretionary descent to 30. Once it was appropriate; and separation was ensured from preceding traffic; I cleared him for the approach. At about the same time; the relieved Controller told me that it looked good to turn Aircraft X off his 270 degree heading back to MLE; on course; which was approximately a 170 heading. He was still at 6000. It sounded good to me; and I turned him on course; believing that he would pass well behind Air Carrier Y; who was descending through 5700 feet when I cleared him. (I think). At one point; I saw that that was not going to work; and I wouldn't have the required separation; so I turned Aircraft X back to the right to a 230 heading. He acknowledged the turn. I was watching the situation; and it didn't seem he was taking the turn; so I issued it again; and again he read it back. This time he started the turn... slowly. When I issued the turn the first time; he was approximately 5 miles from the BE99 (Air Carrier Y). By the time he started his turn after acknowledging a second time; he was approximately 4 miles away. At this point; the Supervisor on duty asked me what was going on with Aircraft X and Air Carrier Y. I told him I was on top of it and had issued a turn to the Mooney. At this point the only thing I could do was watch; as the Mooney made his turn. The closest I ever saw the 2 targets was 2.89 miles; and approximately 600 feet vertical separation. I believe I had the required separation; because by the time I lost 3 miles; the Mooney was diverged at least 30-40 degrees and vectored behind Air Carrier Y. Recommendation; we have had issues with Air Carrier Y pilots of late. They are kind of wild; in that you never know what to expect from them. They seem to fly by the seat of their pants; and often get frustrated by being made number 2 or 3. They often offer to cancel IFR believing it will improve their number in the sequence. When I cleared Air Carrier Y for the visual approach; he seemed to slow his descent rate dramatically. Or it just could have been my perception. Either way; I should have used my own judgment before issuing a turn direct MLE for Aircraft X instead of relying on another controllers opinion. Also; I should have paid more attention to the descent rate of Air Carrier Y. I could have gotten on the pilot and made sure he continued his descent. Good supervision and relief briefings are important as well; but I don't believe they were a factor here.

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.