What happened
On 27 July 2010, a high-stakes situation unfolded at OR Tambo International Airport involving two Boeing 737 aircraft. The first aircraft, ZS-SJS, a B73 and 800 operated by South African Airways, was preparing for departure to Cape Town. After receiving takeoff clearance, the flight crew began their takeoff roll on Runway 21R.
Simultaneously, another aircraft, ZS-OAO, a B737-400 operated by Comair, was taxiing toward the same runway after landing from Cape Town. The crew of ZS-OAO had been instructed to cross Runway 21R via taxiway Lima. As the takeoff roll for ZS-SJS reached approximately 101 knots, air traffic controllers realized that the two aircraft were on a collision course. The Tower West controller issued an urgent command to abort the takeoff. The crew of ZS-SJS immediately executed a rejected takeoff, vacating the runway onto taxiway Echo. No injuries were reported among the 130 occupants on ZS-SJS or the 123 occupants on ZS-OAO, and no damage occurred to either aircraft.
The investigation
An investigation by the SACAA AIID focused on the sequence of clearances provided by the Tower West controllers. The inquiry examined the actions of both the instructor controller and a student controller who was undergoing on-the-job training. The investigation revealed that the student controller had been struggling with runway crossing procedures and coordination, having previously received poor performance grades in related tasks.
Investigators also looked into the technical aspects of the taxiway, noting that the crew of ZS-OAO had initially been halted by active stopbars, which they had to alert the controller to deactivate. The investigation also noted that the controller failed to follow standard station instructions regarding the activation of the crash alarm during the aborted takeoff.
Findings
- The primary cause of the incident was a rejected takeoff due to a runway incursion.
- Air traffic controllers issued conflicting instructions, clearing one aircraft to cross the active runway while simultaneously granting takeoff clearance to another aircraft using the same runway.
- Both aircraft were cleared too early; ZS-SJS was cleared for takeoff while still taxiing toward the intersection, and ZS-OAO was cleared to cross while still some distance from the holding point.
- A lack of situational awareness and controller complacency, driven by a low-workload environment, prevented the immediate detection of the error.
- The student controller's inability to effectively manage the coordination of stopbars and crossing cards contributed to the breakdown in safety.
Safety action
- Implementation of mandatory, recurrent proficiency training for all controllers using high-fidelity simulators to reduce runway incursions.
- Enhancement of training regarding runway crossing instructions and procedures for both airlines and air traffic services.
- Revision of Station Standard Instructions to include Air Traffic Control Resource Management (ATCRM) for coordinated sectors.
- Development of new guidance for controllers regarding minimum time intervals and distances required before issuing takeoff or crossing clearances.