Narrative:

I was working radar east and coordinating the final traffic with radar west. The weather was marginal with a ceiling of about 3;000 and visibility of 6-7 miles. Icing had been reported in different areas in our airspace for most of the morning. The majority of the traffic was on east and I was vectoring aircraft X as a practice GPS approach at ict. Radar west handed off aircraft Y; to me coming from the northwest landing at bec field; a satellite airport east of ict. I had 2-3 military aircraft in the IFR pattern at iab air force base and traffic doing a GPS runway 36 approach to bec. I turned aircraft X from the west to about a 070 heading and descended the aircraft from 4;000 to 3;000. Aircraft Y came over to me at 6;000 and I descended him to 5;000 on initial contact. When aircraft Y was about 5-7 miles northwest of aircraft X (southeast bound) he requested lower to get out of the ice. He didn't specify how much ice he was picking up but I wanted to get him down and so I descended aircraft Y to 4;000. At the time I did that I knew that aircraft X was in front of aircraft Y but I knew that I had descended aircraft X to 3;000 when I turned him to the 070 heading (modified base). What I didn't do was verify that aircraft X had followed my previous clearance to descend to 3;000. Aircraft X had turned to the 070 heading I assigned but he descended only to 3;600 from 4;000. I then went back to looking at my traffic on the east side and when my scan brought me back to aircraft Y and aircraft X I saw that aircraft X was still at 3;600 and aircraft Y was at 4;400 and about 2 miles apart and converging. At that time I knew they were too close and told aircraft Y to maintain 4;400. I understand that that altitude would not provide IFR separation but I just wanted to stop the descent so that the aircraft didn't get any closer together at that point. Aircraft Y responded with 'maintain 4;400' and 'I have the aircraft X in sight.' I then told aircraft Y to 'maintain visual separation from the aircraft X.' at the time I told aircraft Y to maintain visual separation the 2 aircraft were 800 vertical and 1-2 miles horizontally separated. Aircraft X didn't say anything about the other aircraft. Recommendation; there were a few things that led to this incident. I had almost all of the traffic on the east side and we were coordinating the final. The controller in charge asked if we should let radar west have the final but I declined; thinking that I wasn't that busy. It probably would have helped to have had radar west working the aircraft X because I would have had to look closer at the aircraft X's altitude before I descended the aircraft Y. As it was; I knew I descended aircraft X to 3;000 and that there had been enough time for aircraft X to get to 3;000; but he stopped at 3;600. The icing report gave me a sense of urgency that I needed to get aircraft Y down as soon as I could and I assumed that aircraft X was at 3;000 and didn't verify it. I should have verified the altitude. Much of my attention was on the sequencing of my aircraft on the east side and the two that were part of the incident were not as big of an issue in my mind because I assumed that I had them separated and so my defenses were down somewhat for them. Bottom line; I should have had radar west take the final and aircraft X and then should have verified everything before descending aircraft Y.

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Original NASA ASRS Text

Title: ICT TRACON Controller described a loss separation event involving several aircraft; the reporter indicated their urgency to descend the icing aircraft was a contributing factor.

Narrative: I was working RADAR East and coordinating the final traffic with RADAR West. The weather was marginal with a ceiling of about 3;000 and visibility of 6-7 miles. Icing had been reported in different areas in our airspace for most of the morning. The majority of the traffic was on East and I was vectoring Aircraft X as a practice GPS approach at ICT. RADAR West handed off Aircraft Y; to me coming from the northwest landing at BEC Field; a satellite airport east of ICT. I had 2-3 military aircraft in the IFR pattern at IAB Air Force Base and traffic doing a GPS Runway 36 approach to BEC. I turned Aircraft X from the west to about a 070 heading and descended the aircraft from 4;000 to 3;000. Aircraft Y came over to me at 6;000 and I descended him to 5;000 on initial contact. When Aircraft Y was about 5-7 miles northwest of Aircraft X (southeast bound) he requested lower to get out of the ice. He didn't specify how much ice he was picking up but I wanted to get him down and so I descended Aircraft Y to 4;000. At the time I did that I knew that Aircraft X was in front of Aircraft Y but I knew that I had descended Aircraft X to 3;000 when I turned him to the 070 heading (modified base). What I didn't do was verify that Aircraft X had followed my previous clearance to descend to 3;000. Aircraft X had turned to the 070 heading I assigned but he descended only to 3;600 from 4;000. I then went back to looking at my traffic on the east side and when my scan brought me back to Aircraft Y and Aircraft X I saw that Aircraft X was still at 3;600 and Aircraft Y was at 4;400 and about 2 miles apart and converging. At that time I knew they were too close and told Aircraft Y to maintain 4;400. I understand that that altitude would not provide IFR separation but I just wanted to stop the descent so that the aircraft didn't get any closer together at that point. Aircraft Y responded with 'maintain 4;400' and 'I have the Aircraft X in sight.' I then told Aircraft Y to 'maintain visual separation from the Aircraft X.' At the time I told Aircraft Y to maintain visual separation the 2 aircraft were 800 vertical and 1-2 miles horizontally separated. Aircraft X didn't say anything about the other aircraft. Recommendation; there were a few things that led to this incident. I had almost all of the traffic on the East side and we were coordinating the final. The CIC asked if we should let RADAR West have the final but I declined; thinking that I wasn't that busy. It probably would have helped to have had RADAR West working the Aircraft X because I would have had to look closer at the Aircraft X's altitude before I descended the Aircraft Y. As it was; I knew I descended Aircraft X to 3;000 and that there had been enough time for Aircraft X to get to 3;000; but he stopped at 3;600. The icing report gave me a sense of urgency that I needed to get Aircraft Y down as soon as I could and I assumed that Aircraft X was at 3;000 and didn't verify it. I should have verified the altitude. Much of my attention was on the sequencing of my aircraft on the east side and the two that were part of the incident were not as big of an issue in my mind because I assumed that I had them separated and so my defenses were down somewhat for them. Bottom line; I should have had RADAR West take the final and Aircraft X and then should have verified everything before descending Aircraft Y.

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.