What aircraft was involved and where did it happen?

The accident on 2003-03-21 involved a aircraft, registration HB-JAJ, at Zürich Flughafen (LSZH), ZH, CH.

What was the probable cause of the accident?

The incident was caused by the crew of the Boeing 747-357 performing an unauthorized takeoff after misinterpreting a clearance intended for another aircraft, compounded by the controllers' failure to detect an incorrect readback.

Runway Incursion at Zurich Airport Involving Two Aircraft

A Boeing 747 and an Embraer 145 nearly collided on the ground at Zurich Airport after a takeoff clearance for one aircraft was misperceived as authorization for the other.

What happened

On the evening of March 21, 2003, at Zurich Airport, a serious air traffic incident occurred involving a South African Airways Boeing 747-357, registration ZS-SKA, and a Swiss Embraer RJ145LU, registration HB-JAJ.

As the Boeing 747-357 prepared for its flight to Johannesburg, the crew was taxiing via taxiway Echo. While the aircraft was positioned on runway 16, the Aerodrome Control (ADC) controller issued a takeoff clearance to the Swiss Embraer RJ145LU, which was positioned on runway 28. The crew of the ZS-SKA misinterpreted this transmission as authorization for their own departure from runway 16. Consequently, the Boeing 747-357 began its takeoff roll.

Simultaneously, the HB-JAJ initiated its takeoff from runway 28. The two aircraft approached the intersection of runways 16 and 28, coming within approximately 900 meters of each other. The Embraer RJ14 5LU crossed the intersection at an altitude of roughly 50 feet, while the Boeing 747-357 passed through the same point approximately 16 seconds later during its takeoff roll. There were no fatalities or injuries.

The investigation

The investigation focused on the radio communications and the visibility of the aircraft to both crews and controllers. Investigators found that the Boeing 747-357 crew had completed their takeoff checks and were expecting a clearance, which likely contributed to the misinterpretation of the instruction intended for the other aircraft.

Analysis of the audio recordings revealed that the ZS-SKA crew performed a readback that included the incorrect runway number, stating "cleared for take off 16, SAA275." However, the controllers at the Aerodrome Control and Ground Control positions initially believed they had heard a correct readback from the HB-JAJ. It was later discovered that the HB-JAJ readback was not captured on the recording, while the ZS-SKA readback was present but obscured by significant background noise and a distinct accent.

Furthermore, the investigation established that the Traffic Collision Avoidance Systems (TCAS) on both aircraft were unable to provide warnings. The Embraer RJ145LU's system is designed to suppress traffic advisories at altitudes below 380 feet, and the Boeing 747-357's system suppresses advisories below 1,000 feet, rendering the technology ineffective for detecting ground-based or low-altitude threats during takeoff.

Findings

The primary cause was the unauthorized takeoff of the Boeing 747-357 on runway 16 without receiving a valid clearance.
The crew of the ZS-SKA failed to recognize that the takeoff authorization was intended for a different aircraft on a different runway.
Air traffic controllers failed to notice that the ZS-SKA had read back an incorrect runway designation.
The similarity in callsign numbering (both involving "75.") and the crew's expectation of a clearance likely contributed to the confusion.
Background noise and heavy accents on the radio frequency hindered clear communication and recognition of the error.

Safety action

The Federal Office of Civil Aviation (FOCA) should ensure that flight crews are provided with additional supplementary information, such as specific departure sequences, when taxi clearances are issued for multiple runways simultaneously to enhance situational awareness.