What happened
On 16 January 2010, an Airbus A300-600, registration EP-IBB, was performing a takeoff from Stockholm Arlanda Airport. During the takeoff roll, the left engine suffered a sudden and rapid loss of thrust. Simultaneously, for a duration of approximately 1.5 seconds, the right engine was at full power. This sudden imbalance in thrust created a significant yawing moment.
As the aircraft attempted to maintain its centerline, the nose wheel was unable to generate sufficient friction against the contaminated runway surface to counteract the asymmetric forces. The aircraft began to veer from its path, and despite the crew's efforts to use the rudder and nose wheel steering, the aircraft eventually exited the runway.
The investigation
The Swedish Accident Investigation Authority (SHK) conducted a comprehensive technical and operational examination. The investigation included a detailed analysis of the Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR) to reconstruct the sequence of events. Investigators also performed simulator tests using an Airbus A300-600 training simulator to evaluate the aircraft's controllability on contaminated surfaces under asymmetric thrust conditions.
Technically, the investigation focused on the left engine, which had experienced a failure. Metallurgical examinations were conducted at specialized laboratories to inspect critical engine components. The investigation also reviewed the runway conditions at Arlanda on the morning of the incident, specifically looking at friction levels and the impact of the contaminated surface on directional control.
Findings
- The primary cause of the initial veer was the asymmetric thrust created when the left engine lost power while the right engine remained at full thrust for 1.5 seconds.
- The contaminated runway surface prevented the nose wheel from generating enough lateral force to counteract the yawing moment.
- The incident was further complicated by the unintended application of differential braking by the crew, which contributed to the yawing moment.
- The crew's inputs via the rudder and tiller were insufficient to prevent the aircraft from running off the runway given the combination of engine failure and reduced surface friction.