On 16 August 2001, a Boeing 737-500 being operated by Continental Airlines on a scheduled passenger flight from Cleveland OH to Dallas Fort Worth TX and a Boeing 737-300 being operated on a scheduled passenger flight from Dallas Fort Worth to Oakland CA almost collided in normal day visibility when the just-landed aircraft crossed the runway on which the departing aircraft was taking off. The latter was able to get airborne just in time to pass over the taxiing aircraft but returned to land because a suspected - and subsequently confirmed - tail strike sustained during the avoidance manoeuvre.
The National Transportation Safety Board (USA) (NTSB) carried out an Investigation. It was established that the Delta Boeing 737 had been cleared for take off from runway 18L about 30 seconds before the same controller cleared the just-landed Continental 737, which had just landed on runway 18R and taken the high speed exit E6 onto taxiway ‘WM’, to cross same runway without stopping. The Captains of both aircraft, who were also the designated PF in both cases, recognised the high risk of collision and took evasive action. The Captain of the taxiing aircraft had increased thrust in an attempt to clear the runway more quickly – but was unable to clear the runway in time. The Captain of the Delta aircraft had rotated more rapidly and earlier than planned in order to just fly over the crossing aircraft. The departing aircraft subsequently returned to land because of a suspected tail strike during the high rate rotation. Examination of this aircraft plane subsequently confirmed that damage to the aircraft skin on the underside of the tail had been sustained.
It was found that, five minutes prior to the event, the West TWR and GND positions had been combined on the instructions of the controller in charge who was also operating the flight data position. Shortly after this, a National Air Traffic Controllers Association representative had entered the TWR cabin and begun having a meeting with the controller-in-charge. However, it then quickly became clear that it was becoming too busy to continue with the combined position and the just-relieved GND controller who was still present moved back to his workstation to de-combine the positions. Just over a minute later, and before this had taken effect, the radar targets of the two aircraft merged at the runway 18L/ ‘WM’ intersection.
KDFW Airport Diagram, click on diagram to enlarge
The incident controller subsequently advised that he did not scan the runway before clearing the taxiing aircraft to cross. The Investigation noted that at the time of the incident, the applicable entry in the FAA Air Traffic Control Handbook said that the TWR controller “has primary responsibility for operations conducted on the active runway and must control the use of those runways" and also that TWR controllers “shall visually scan runways to the maximum extent possible."
Weather conditions at the time were good with a recorded visibility of 16km and the surface wind almost calm. The Flight Data Recorder (FDR) of the Delta 737 was successfully downloaded and showed that the pitch attitude of the aircraft as it became airborne had reached just over 20°.
The Probable Cause of the incident was formally determined as:
The local controller clearing the taxiing aircraft to cross the runway in front of the aircraft on takeoff roll.
Three Contributing factors were identified as:
- the local controller's failure to follow FAA procedures and directives to visually scan the runway prior to issuing the crossing clearance,
- the local controller’s excessive workload, and
- the tower supervisor's inadequate supervision.
The Final Reports FTW01IA183A and FTW01IA183B of the Investigation were adopted on 30 May 2003. No Safety Recommendations were issued.