Narrative:

Aircraft X was westbound; level at 16;000. Air carrier Y was north westbound on the TYGER6 arrival to mci; descending to 17;000. I had leveled aircraft X to allow air carrier Y to descend through aircraft X using vertical separation. I issued traffic to each aircraft and instructed each to report the other aircraft in sight. Aircraft X reported air carrier Y in sight. I instructed aircraft X to maintain visual separation from air carrier Y and to climb and maintain FL220. I then advised air carrier Y that aircraft X had him/her in sight; would maintain visual separation; and instructed the aircraft to descend and maintain 12;000. Air carrier Y had been descending at approximately 2;500-3;000 FPM. During his climb to 16;000; I noticed updates of 300 to 500 feet on aircraft X; suggesting a rate of climb of 1;500 to 2;500 FPM. I failed to notice occasional updates of nearly 1000 feet; which made his average rate of climb much higher. In retrospect; this was apparent from his total time to climb to 16;000. After I issued clearance to FL220; aircraft X climbed at a very high rate. The first two hits showed a change of altitude of 1;200 and 900 feet; respectively. That suggests a climb rate of about 5;000 feet per minute. The rate of descent of air carrier Y continued to vary between 2000 and 3000 FPM. As a result; aircraft X and air carrier Y lost separation above FL180 for two radar hits. The closest point appears to have been 3.5 NM and 500 feet. Both radar hits with less than standard separation occurred between FL180 and FL190. Recommendation; my original intent was to allow air carrier Y to descend through aircraft X. Because aircraft X was the first to report the other aircraft in sight; I issued the climb to aircraft X while air carrier Y was at too high of an altitude to ensure that the aircraft passed each other below class a airspace. This was a misapplication of the visual separation rule that was a result of my failure to consider the performance characteristics of the aircraft involved. I was working this position to achieve my required currency and had been on position for approximately 2.5 hours when this event occurred.

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Original NASA ASRS Text

Title: ZKC controller experienced an operational error when misjudging climb/descent rates that resulted in the misapplication of visual separation standards in Class A airspace.

Narrative: Aircraft X was westbound; level at 16;000. Air Carrier Y was north westbound on the TYGER6 arrival to MCI; descending to 17;000. I had leveled Aircraft X to allow Air Carrier Y to descend through Aircraft X using vertical separation. I issued traffic to each aircraft and instructed each to report the other aircraft in sight. Aircraft X reported Air Carrier Y in sight. I instructed Aircraft X to maintain visual separation from Air Carrier Y and to climb and maintain FL220. I then advised Air Carrier Y that Aircraft X had him/her in sight; would maintain visual separation; and instructed the aircraft to descend and maintain 12;000. Air Carrier Y had been descending at approximately 2;500-3;000 FPM. During his climb to 16;000; I noticed updates of 300 to 500 feet on Aircraft X; suggesting a rate of climb of 1;500 to 2;500 FPM. I failed to notice occasional updates of nearly 1000 feet; which made his average rate of climb much higher. In retrospect; this was apparent from his total time to climb to 16;000. After I issued clearance to FL220; Aircraft X climbed at a very high rate. The first two hits showed a change of altitude of 1;200 and 900 feet; respectively. That suggests a climb rate of about 5;000 feet per minute. The rate of descent of Air Carrier Y continued to vary between 2000 and 3000 FPM. As a result; Aircraft X and Air Carrier Y lost separation above FL180 for two RADAR hits. The closest point appears to have been 3.5 NM and 500 feet. Both RADAR hits with less than standard separation occurred between FL180 and FL190. Recommendation; my original intent was to allow Air Carrier Y to descend through Aircraft X. Because Aircraft X was the first to report the other aircraft in sight; I issued the climb to Aircraft X while Air Carrier Y was at too high of an altitude to ensure that the aircraft passed each other below Class A airspace. This was a misapplication of the visual separation rule that was a result of my failure to consider the performance characteristics of the aircraft involved. I was working this position to achieve my required currency and had been on position for approximately 2.5 hours when this event occurred.

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.