Narrative:

I was working the local and ground positions; combined at the time. I received a transmission from aircraft X; who stated he was cleared for a visual approach to runway 18. At the time he was at about a 15 mile final for runway 18 and still at 10;000ft MSL. I gave aircraft X landing clearance at that time. About 3-5 miles later; I noticed aircraft X was not descending very well and advised him that 'south' turns are approved for his descent.' also about this same time the radar controller called me and said aircraft X was approved to circle to runway 24R if needed for his descent. I advised aircraft X; he did not appear to be able to make his descent from his present position and offered him runway 24R; which he accepted. I then told aircraft X to circle to runway 24R; runway 24R cleared to land. Also at this time I had aircraft Y taxiing to runway 24R for departure; who was given a release time from flow control. He reached the runway and was holding short of runway 24R. Aircraft X made it to about a 2-1/2 to 3 mile final but still not making his descent for the runway. At this point the pilot requested a left 360 degree turn to make the rest of his descent for landing. I approved the 360 degree turn. I anticipated aircraft X to make a 1-2 mile wide turn and re-establish on his final approach at about a 4-5 mile point from the runway. At this point there was additional traffic inbound for runway 24R that was being sequenced behind aircraft X for landing; so I cleared aircraft Y for an immediate takeoff; and gave him the reason for his immediate takeoff clearance as traffic turning onto a 4 mile final. Aircraft Y accepted the immediate takeoff and taxied onto the runway for departure. Aircraft X was now turning final and was staying a lot closer to the airport for his turn; and making a tighter turn than I had anticipated. Aircraft X was about a 2 to 2-1/2 mile final when aircraft Y began the takeoff roll. The separation requirement for an arrival and departure on the same runway; as in this situation; is the departing aircraft must be 6;000ft down the runway and airborne before the arriving aircraft crosses the runway threshold. I believed at this time the proper separation was going to be maintained in this situation. Aircraft Y was now greater than 6;000 feet down runway 24R on his takeoff roll; and started his rotation; with his nose-gear off the ground. Aircraft X was crossing the threshold for runway 24R at this time as well. I do not think that aircraft Y's rear landing gear were off the ground at the time aircraft X crossed the runway threshold; which violated the 'airborne' portion of the runway separation rule. Recommendation; I do not know why aircraft X was still at 10;000 ft MSL so close to his landing runway; but his high altitude was definitely a factor to set this event in motion. My recommendation to fix this situation in the future is for the radar controller to keep control of an aircraft in this situation so that he has the option to vector the aircraft to help him descend. This allows the pilot to have a safer rate of descent and speed for his approach; and also gives more radar options to both the controllers and the pilot. Also; I should have recognized the developing situation quicker and realized it was not going to work. I should have canceled aircraft Y's takeoff clearance and told aircraft X to go around. This would have both; prevented the runway separation error; and would have given aircraft X more time to have better control and speed of his aircraft for landing. I also believe that my low level of experience may have had a minor effect on the situation. I have never seen this situation before in any OJT; training; or work ive done after being certified. I believed that aircraft X was going to make a wider turn than he did; and I think never seeing an air carrier make a 360 degree turn or struggle with making descent contributed to my belief that proper separation was goingto be maintained.

Google
 

Original NASA ASRS Text

Title: DAY local controller experienced a loss of separation between an arrival and a departure when the departure was not 'airborne' as the arrival crossed the runway threshold; low experience level was listed as one causal factor.

Narrative: I was working the Local and Ground positions; combined at the time. I received a transmission from Aircraft X; who stated he was cleared for a visual approach to Runway 18. At the time he was at about a 15 mile final for Runway 18 and still at 10;000ft MSL. I gave Aircraft X landing clearance at that time. About 3-5 miles later; I noticed Aircraft X was not descending very well and advised him that 'S' turns are approved for his descent.' Also about this same time the RADAR controller called me and said Aircraft X was approved to circle to Runway 24R if needed for his descent. I advised Aircraft X; he did not appear to be able to make his descent from his present position and offered him Runway 24R; which he accepted. I then told Aircraft X to circle to Runway 24R; Runway 24R cleared to land. Also at this time I had Aircraft Y taxiing to Runway 24R for departure; who was given a release time from flow control. He reached the runway and was holding short of Runway 24R. Aircraft X made it to about a 2-1/2 to 3 mile final but still not making his descent for the runway. At this point the pilot requested a left 360 degree turn to make the rest of his descent for landing. I approved the 360 degree turn. I anticipated Aircraft X to make a 1-2 mile wide turn and re-establish on his final approach at about a 4-5 mile point from the runway. At this point there was additional traffic inbound for Runway 24R that was being sequenced behind Aircraft X for landing; so I cleared Aircraft Y for an immediate takeoff; and gave him the reason for his immediate takeoff clearance as traffic turning onto a 4 mile final. Aircraft Y accepted the immediate takeoff and taxied onto the runway for departure. Aircraft X was now turning final and was staying a lot closer to the airport for his turn; and making a tighter turn than I had anticipated. Aircraft X was about a 2 to 2-1/2 mile final when Aircraft Y began the takeoff roll. The separation requirement for an arrival and departure on the same runway; as in this situation; is the departing aircraft must be 6;000ft down the runway and airborne before the arriving aircraft crosses the runway threshold. I believed at this time the proper separation was going to be maintained in this situation. Aircraft Y was now greater than 6;000 feet down Runway 24R on his takeoff roll; and started his rotation; with his nose-gear off the ground. Aircraft X was crossing the threshold for Runway 24R at this time as well. I do not think that Aircraft Y's rear landing gear were off the ground at the time Aircraft X crossed the runway threshold; which violated the 'airborne' portion of the runway separation rule. Recommendation; I do not know why Aircraft X was still at 10;000 ft MSL so close to his landing runway; but his high altitude was definitely a factor to set this event in motion. My recommendation to fix this situation in the future is for the RADAR controller to keep control of an aircraft in this situation so that he has the option to vector the aircraft to help him descend. This allows the pilot to have a safer rate of descent and speed for his approach; and also gives more RADAR options to both the controllers and the pilot. Also; I should have recognized the developing situation quicker and realized it was not going to work. I should have canceled Aircraft Y's takeoff clearance and told Aircraft X to go around. This would have both; prevented the runway separation error; and would have given Aircraft X more time to have better control and speed of his aircraft for landing. I also believe that my low level of experience may have had a minor effect on the situation. I have never seen this situation before in any OJT; training; or work Ive done after being certified. I believed that Aircraft X was going to make a wider turn than he did; and I think never seeing an air carrier make a 360 degree turn or struggle with making descent contributed to my belief that proper separation was goingto be maintained.

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.