Narrative:

I was training a cpc/it on local control; and he had aircraft Y depart 17L; and then slotted aircraft X into departure position; with the aircraft Z on about a 3 mile close in visual approach. Aircraft Z checked in at about 2.5 mile final (due to a missed frequency change; I was told later) and I know he was caught off guard by the arrival; thinking that it was still on the downwind versus being on a really close in base leg; but instead of fixing the arrival; which I was anticipating; he told the arrival to continue; and then launched aircraft X; with aircraft Y just off of the departure end. We turned aircraft Y to a diverging heading with plenty of time to spare; but that did not help us with the wake turbulence separation requirements. We ended up with 2.5 miles of lateral separation on the two departures. I believe this was caused by a reflex on the trainee's part that he was in the heat of the moment and knew he had enough separation with his departures. As a cpc from another facility; he is used to using the standard separation standards between these types of aircraft; and he reverted to that mindset when he realized he was in a tight spot. At sdf however; we have wake turbulence recategorization separation standards; which allow us to run large and heavy aircraft closer together; but we have to have more separation with the small aircraft and anything else. This; along with the very quick nature of the event; and slower reaction time on my part; were all contributing factors to this event. After the operation; I and my trainee discussed all of the options we should have employed to prevent this situation; such as not slotting the second departure; or using visual separation; coordinating for another runway for the arrival to land; etc.I would love to see the wake recat standards allow for the benefit of the closer heavy separation requirements; along with keeping the same standards for smalls as we used to have; that would be a benefit to all facilities; nationwide; not just facilities that have a majority of heavy aircraft.

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Original NASA ASRS Text

Title: SDF Local Control Instructor reports of incident where he let the Developmental depart an aircraft too close to a previous departure because of aircraft on short final.

Narrative: I was training a CPC/IT on Local Control; and he had Aircraft Y depart 17L; and then slotted Aircraft X into departure position; with the Aircraft Z on about a 3 mile close in visual approach. Aircraft Z checked in at about 2.5 mile final (due to a missed frequency change; I was told later) and I know he was caught off guard by the arrival; thinking that it was still on the downwind versus being on a really close in base leg; but instead of fixing the arrival; which I was anticipating; he told the arrival to continue; and then launched Aircraft X; with Aircraft Y just off of the departure end. We turned Aircraft Y to a diverging heading with plenty of time to spare; but that did not help us with the wake turbulence separation requirements. We ended up with 2.5 miles of lateral separation on the two departures. I believe this was caused by a reflex on the trainee's part that he was in the heat of the moment and knew he had enough separation with his departures. As a CPC from another facility; he is used to using the standard separation standards between these types of aircraft; and he reverted to that mindset when he realized he was in a tight spot. At SDF however; we have Wake Turbulence Recategorization Separation Standards; which allow us to run large and heavy aircraft closer together; but we have to have more separation with the small aircraft and anything else. This; along with the very quick nature of the event; and slower reaction time on my part; were all contributing factors to this event. After the operation; I and my trainee discussed all of the options we should have employed to prevent this situation; such as not slotting the second departure; or using visual separation; coordinating for another runway for the arrival to land; etc.I would love to see the Wake Recat standards allow for the benefit of the closer heavy separation requirements; along with keeping the same standards for smalls as we used to have; that would be a benefit to all facilities; nationwide; not just facilities that have a majority of heavy aircraft.

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.