Comair B734 at Johannesburg on Jul 27th 2012, cleared to cross runway despite runway occupied for takeoff
Last Update: August 23, 2012 / 14:16:26 GMT/Zulu time
A South African Airways Boeing 737-800, registration ZS-SJS performing flight SA-327 from Johannesburg to Cape Town (South Africa) with 124 passengers and 6 crew, had been cleared for takeoff from runway 21R while still taxiing on taxiway A and was entering the runway via taxiway N.
When MN-102 reported on Tower West frequency about one minute after takeoff clearance to SA-327 had been transmitted, the controller cleared the aircraft to cross runway 21R. When the aircraft reached the holding line L at runway 21R, the stop bars were still turned on. The crew queried the stop bars, tower turned them off and the aircraft began to taxi past the hold short line.
In the meantime SA-327 had aligned with the runway center line and was beginning its takeoff roll.
The west controller realised his error at that point, cancelled the takeoff clearance and instructed SA-327 to stop immediately. The aircraft had acclerated to about 80 knots indicated airspeed when the crew rejected takeoff and brought the aircraft to a safe stop. The controller apologised, instructed SA-327 to vacate the runway to the right and return to the holding point.
SA-327 successfully departed on their second takeoff run and reached Cape Town without further incident for a safe landing.
The crew MN-102 first heard of the presence of SA-327 when the controller cancelled the takeoff clearance. The aircraft safely crossed runway 21R and reached the apron.
South Africa's Civil Aviation Authority (SACAA) released their final report concluding the probable cause of the serious incident was:
Rejected takeoff due to runway incursion.
Error caused by ATC when giving instructions to one aircraft to cross the active runway after takeoff clearance was given to another aircraft, using the same runway.
The SACAA reported that a student air traffic controller under the supervision of an instructor air traffic controller was at duty at Tower West at the time of the incident. Both student and instructor had taken their positions 20 minutes prior to the incident and were immediately relieved from duty following the incident.
The student controller had been involved in two other incidents in February and March 2010 while undergoing training for approach control. As a result air traffic services had suspended his training on approach, but permitted his training as tower controller to continue.
Weather conditions at the time of the occurrence were "severe clear" at temperatures around 16 degrees C.
SA-327 had been issued takeoff clearance while taxiing on taxiway A still 1445 meters from taxiway N, the aircraft needed 127 seconds until it reached the runway following the takeoff clearance and immediately began their takeoff roll.
MN-102 reported on west frequency 51 seconds after the takeoff clearance and was cleared to cross runway 21R 73 seconds after the takeoff. The aircraft was 200 meters from the holding point L at that time and needed 103 seconds until reaching the holding point. The crew stopped seeing the stop bars still active, refused to cross the runway with the stop bars active and queried the tower, upon receiving that query the tower controller realised he had not turned off the stop bars when issuing the crossing clearance and just turned the stop bars off. MN-102 then continued to cross the runway.
SA-327 was not paying particular attention to the radio communication between tower and MN-102, they had realised the aircraft was holding short of the runway and thought, the flight was waiting for departure clearance. They did not expect any other traffic would use the runway after they had received takeoff clearance.
The SACAA further analysed that the sequence of events showed the controllers were not in control of the situation and continued: "It is the opinion of the investigator that the reason could be because of their behaviour displayed in the tower, which was complacency and over-confident. The result was inattention which is probably due to the undemanding environment as seen by the workload at the time. There was no threat of anything going wrong, which heightened a false sense of security within them. By the time that the threat of runway incursion was detected, it was almost too late because both aircraft were already on course to a collision on the runway." and later: "A disaster was imminent, that of having the two aircraft colliding, probably with the result of having a considerable number of occupants fatally or seriously injured." SA-327 had reached a speed between 80 and 90 knots, below V1, when the takeoff was rejected.
The SACAA further analysed with regards to the performance of the student controller and logs from his training: "The instructors had identified the problem to be the inability of the student to do the following; Â“sequence for rotation of strips, crossing cards, and stop bars co-ordination,Â” which were identified in the investigation as factors that contributed to the incident. It is the opinion of the investigator that the student was having a problem adapting to the ATC operational requirements of FAJS. During the few weeks when he was doing practical training in the tower, week after week the same result of poor performance was noted. The student was not improving on the identified items until the incident occurred."
This article is published under license from Avherald.com. © of text by Avherald.com.
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