Incident Involving a Airbus 340-642 (SAS) due to Pilot’s Spatial Disorientation Near Clariden, Switzerland

On November 6, 2018 near Clariden, Switzerland, a Airbus 340-642 (South African Airways) was involved in a serious incident during a commercial flight from Johannesburg, South Africa, to Frankfurt, Germany, with 259 persons on board. The aircraft, while in cruise flight at Flight Level (FL) 380, experienced a sudden change in high-altitude wind conditions, leading to an overspeed condition. This prompted the Pilot in Command (PIC) to deactivate the autopilot and manually control the aircraft, resulting in several activations of the stall warning as the aircraft climbed and then descended to stabilize at FL 340.

Photo of a South African Airways Airbus A340-642 flying over the Clariden mountains in Switzerland.

Investigative findings highlighted several critical issues during the incident. The unexpected wind direction change during cruise flight was not anticipated by the crew, causing the aircraft to exceed its maximum operating speed. The flight crew did not follow the established overspeed recovery procedure. The PIC, in an attempt to manage the situation, incorrectly applied the Overspeed Emergency Bulletin (OEB) No. 49, leading to the deactivation of two of the three Air Data Inertial Reference Units (ADIRUs) and the Autothrust system. This resulted in the aircraft being temporarily controlled under Alternate Law, a less protective flight control mode. The PIC's control inputs were not sufficient to stabilize the flight attitude promptly, and the crew's overall cooperation and procedure implementation during the overspeed and stall recovery were flawed.

The Airbus A340 involved was well-maintained and certified for commercial passenger transport. The aircraft, manufactured in 2003, had accumulated significant operating hours and flights without reported defects in its flight control system. The flight crew, consisting of the PIC and two co-pilots, were experienced and well-rested, with the crew having undergone rest periods as per the flight safety guidelines.

A depiction of view of the Clariden mountains in Switzerland from the inside of the cockpit of a South African Airways Airbus A340-642. This perspective offers a breathtaking panorama of the Alpine landscape as seen from the pilot's viewpoint at 38,000 feet.

Fortunately, there were no injuries to the crew or passengers, and no damage to the aircraft was reported following the incident. The Airbus A340's advanced control systems, including the fly-by-wire system with high angle of attack and high-speed protections, played a crucial role in managing the situation. These systems, however, were impacted by the crew's actions and the aircraft's temporary operation in Alternate Law.

Amelia™

Amelia™ provides Flight Envelope for the aircraft and Health Envelope for the pilot that is an add-on, integrating in a non-intrusive fashion to the avionics. Spatial disorientation meant that the PIC was not able to recognize the flight attitude and played an important role in the incident. The Flight Data Recorder (FDR) data prove that the fluctuation of wind speed caused by mountain waves and their influence on the aircraft resulted in longitudinal deceleration or acceleration. Using acceleration sensor data, Gravito-Intertial Force (GIF) was calculated. It is a force which affects the human equilibrium organ and is experienced by pilots as pitch-up or pitch-down movement.

View of the Clariden mountains in Switzerland from the cockpit of a South African Airways Airbus A340-642.

Amelia™ is enabled by a novel 3D holographic interface to the Flight Envelope, an intuitive way to gauge aircraft’s operating parameters including the attitude. Amelia™ Flight Envelope would have alerted the pilot about the autopilot flight attitude especially when the PIC disabled the autopilot, which was compensating for altitude loss in the downdraft. Amelia™’ 3D holographic interface would have clearly indicated that there was a difference between the PIC’s observed pitch angle and the actual pitch angle. This would have made the PIC realize that he was experiencing spatial disorientation.

A depiction of cockpit of the South African Airways Airbus A340-642, along with the two pilots and an expansive view of the Clariden mountains through the cockpit windows.

References

German Federal Bureau of Aircraft Accident Investigation BFU18-1626-FX

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