Tower Controller providing OJT described a loss of separation between two subsequent departures during a rarely used traffic flow.
Synopsis
Tower Controller providing OJT described a loss of separation between two subsequent departures during a rarely used traffic flow.
Narrative
Airport was East Traffic; a configuration used 3 to 5 times a year. I was conducting OJT on the Local One position. We had been working for some time; had several departures and working on where the marks were to obtain standard separation. By this point in the session; the developmental was consistently hitting the 3; 4 and 5 mile marks. An A319 on a SID departure was cleared for take off Runway XXL. When the A319 was 3/4 down the runway and airborne; a B757 on a different SID departure was cleared for take off on Runway XXL [a different runway]. When the A319 was switched to Departure; I did notice he seemed to be climbing out rather slowly. I kept this information in the back of my mind so I could watch the separation between the A319 and the B757 when the B757 would tag up. Just as the B757 got airborne; I heard the Traffic Manager call out that the B757 needed to call company. I turned to find the Traffic Manager and tell him that the B757 was airborne. I instructed the developmental to pass the message for the B757 to call company and to contact Departure. I forgot to look at the spacing as I had planned. Unfortunately; the B757 climbed out more rapidly than expected; combined with the A319's slower than anticipated climb out resulted in a loss of separation. Try not to push the developmental too early in training and under abnormal circumstances. Evaluate plans for future 'outs;' such as coordinate a different heading; apply visual separation; etc. Do not allow distractions to keep me from my first priority of separating the aircraft!
Second reporter narrative
[I was] training on Local Control 1; first time training on East traffic. I had been clearing departures for take off at the same point throughout my training session and didn't anticipate the A319 to be that slow in his climb out. Similarly; I didn't anticipate the B757 to climb out that quickly. Initially it appeared to me that I had separation and I anticipated the Departure Controller to turn the B757 earlier than he did. Be more aware of the aircraft types in play - their destination as well. Go the extra mile to ensure separation even if it might be overkill; for example; I should have obtained visual with the B757 or coordinated a turn with departure to obtain the 15 degrees. If I had taken the extra step to ensure the separation I wouldn't be writing this; and as it turned out; I needed it because separation was lost. Or how about this: wait an extra 10 seconds to clear the B757 for take off. There was no need to push in this situation.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.