Narrative:

I was working local control south. An MD11 was holding in position; runway xxr. A lear was on approximately on a 7 mile final; runway xxr indicating 220 KIAS. Another air carrier was on departure roll; runway xxl; and an A319 was lining up and waiting; runway xxl; and had reported the previous departure in sight. I was applying visual separation. When the lear checked in; I cleared him to land and advised him there would be a departure prior to his arrival. Upon reaching 5 miles; I asked the lear if they were at final approach speed; and that traffic was holding in position; a heavy MD11; will depart prior to your arrival; caution wake turbulence. I received an answer in the affirmative. I would have instructed the lear to maintain slowest practical speed; but he appeared to be just inside of 5 miles. When the A319 was cleared for take off; he was told to maintain visual separation from the previous departure and to expedite. The A319 acknowledged. At this time; the lear was approximately 2.5-3 miles out. Given the heavy MD11 was known to take longer to roll than normal aircraft; I asked him if he had the A319 departing xxl in sight. When he replied in the affirmative; I applied visual separation; advised him to not overtake the aircraft; and cleared him for take off at a point early than I normally would comfortably clear him for take off due to the lear still indicating 210 KIAS at 2 mile final. The MD11 advised he would not overtake the A319 and began departure roll. At this point; the A319 was ahead of the MD11 at the departure end. The MD11 rotated early and it appeared all was working according to plan. The MD11 was on a flight plan that would take him due east and the A319 was on a flight plan that would eventually diverge south; meaning the MD11 would have to cross the flight path of the A319 at some point. When the A319 tagged up; I noticed he was indicating 160 KIAS on departure. When the MD11 tagged up; I noticed he was indicating 180 KIAS. Upon realizing this; I instructed the A319 to maintain maximum forward speed and switched him to departure. The MD11 was still behind the A319. The MD11 then indicated that it looked like he was overtaking an aircraft departing runway 8 which was a mistake on his part because there was no departure off of runway 8; it was the A319 he was overtaking. He asked if this was okay and I promptly replied negative and to not overtake that aircraft; the A319 he was maintaining visual separation from. He acknowledged and even appeared to veer slightly to the south in order to avoid an overtake. At no point did the MD11 overtake the A319 looking out the window; nor on the radar display to my knowledge. When everything appeared to have been worked out; I switched the MD11 to departure. I apologized to the departure controller for the squeeze and advised him that I was stopping departures until the situation was worked out. However; I was unaware there was a NORDO aircraft in the departure path of the MD11 and the A319 approximately 15 miles off the departure end; which didn't leave much room for the departure controller to work out the situation; so departures were stopped by approach due to the NORDO aircraft; not due to the MD11 and A319 situation; as initially thought.a discussion was held with the supervisor and other controllers as to better outs; such as coordinating a heading; or holding the MD11 in position and sending the lear around. Although legal; it was ultimately an unsafe situation where wake turbulence separation may have been lost had the MD11 overtaken the A319. Another option would have been to land the lear on runway xxl and give a little more room behind the A319 with the MD11 departing on xxr. This definitely was a lesson learned that aircraft don't always perform as they normally perform. A319's will normally climb out at 180 KIAS increasing while the heavy MD11's will climb out at 150/160 KIAS.

Related reports:

Google
 

Original NASA ASRS Text

Title: Tower Controller described a near loss of separation between two successive departures; complicated by a NORDO adding to the developing situation.

Narrative: I was working Local Control South. An MD11 was holding in position; Runway XXR. A Lear was on approximately on a 7 mile final; Runway XXR indicating 220 KIAS. Another Air Carrier was on departure roll; Runway XXL; and an A319 was lining up and waiting; Runway XXL; and had reported the previous departure in sight. I was applying visual separation. When the Lear checked in; I cleared him to land and advised him there would be a departure prior to his arrival. Upon reaching 5 miles; I asked the Lear if they were at final approach speed; and that traffic was holding in position; a heavy MD11; will depart prior to your arrival; caution wake turbulence. I received an answer in the affirmative. I would have instructed the Lear to maintain slowest practical speed; but he appeared to be just inside of 5 miles. When the A319 was cleared for take off; he was told to maintain Visual Separation from the previous departure and to expedite. The A319 acknowledged. At this time; the Lear was approximately 2.5-3 miles out. Given the heavy MD11 was known to take longer to roll than normal aircraft; I asked him if he had the A319 departing XXL in sight. When he replied in the affirmative; I applied Visual Separation; advised him to NOT overtake the aircraft; and cleared him for take off at a point early than I normally would comfortably clear him for take off due to the Lear still indicating 210 KIAS at 2 mile final. The MD11 advised he would NOT overtake the A319 and began departure roll. At this point; the A319 was ahead of the MD11 at the departure end. The MD11 rotated early and it appeared all was working according to plan. The MD11 was on a Flight Plan that would take him due east and the A319 was on a Flight Plan that would eventually diverge south; meaning the MD11 would have to cross the flight path of the A319 at some point. When the A319 tagged up; I noticed he was indicating 160 KIAS on departure. When the MD11 tagged up; I noticed he was indicating 180 KIAS. Upon realizing this; I instructed the A319 to maintain maximum forward speed and switched him to departure. The MD11 was still behind the A319. The MD11 then indicated that it looked like he was overtaking an aircraft departing Runway 8 which was a mistake on his part because there was no departure off of Runway 8; it was the A319 he was overtaking. He asked if this was okay and I promptly replied negative and to NOT overtake that aircraft; the A319 he was maintaining visual separation from. He acknowledged and even appeared to veer slightly to the south in order to avoid an overtake. At no point did the MD11 overtake the A319 looking out the window; nor on the RADAR display to my knowledge. When everything appeared to have been worked out; I switched the MD11 to Departure. I apologized to the Departure Controller for the squeeze and advised him that I was stopping departures until the situation was worked out. However; I was unaware there was a NORDO aircraft in the departure path of the MD11 AND the A319 approximately 15 miles off the departure end; which didn't leave much room for the Departure Controller to work out the situation; so departures were stopped by Approach due to the NORDO aircraft; not due to the MD11 and A319 situation; as initially thought.A discussion was held with the supervisor and other controllers as to better outs; such as coordinating a heading; or holding the MD11 in position and sending the Lear around. Although legal; it was ultimately an unsafe situation where wake turbulence separation may have been lost had the MD11 overtaken the A319. Another option would have been to land the Lear on Runway XXL and give a little more room behind the A319 with the MD11 departing on XXR. This definitely was a lesson learned that aircraft don't always perform as they normally perform. A319's will normally climb out at 180 KIAS increasing while the Heavy MD11's will climb out at 150/160 KIAS.

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.