What happened
On January 8, 2010, a Boeing 737-800 operating a scheduled flight from Nuremberg to Düsseldorf experienced a runway excursion during its takeoff roll. The aircraft, carrying 125 passengers and six crew members, was operating under winter conditions characterized by continuous snowfall and a temperature of -5°C. The runway surface was covered with approximately 2 mm of snow, and the reported braking action was medium.
As the aircraft was taxiing onto runway 10, the crew performed a rolling takeoff without stopping. During the initial phase of the takeoff roll, the aircraft was not yet aligned with the runway centerline. The crew increased engine thrust from approximately 21% to 43% N1 while the aircraft was still navigating a turn. This increase in power, combined with the slippery, snow-covered surface, caused the aircraft to drift left of the centerline. Although the crew attempted to correct the heading using nose wheel steering, the increasing speed and lateral acceleration made the aircraft difficult to stabilize. Eventually, the aircraft overran the right edge of the runway at approximately 17 kt, coming to a stop in the unpaved area about 5 meters from the runway edge. There were no fatalities or injuries, though the aircraft and surrounding property sustained minor damage.
The investigation
The BFU investigation examined flight data recorder (DFDR) and cockpit voice recorder (CVCR) parameters, as well as maintenance and operational procedures. Investigators analyzed the engine performance, noting that the left engine maintained slightly higher N1 values than the right engine during the acceleration phase. The investigation also reviewed the airline's Operations Manual (OM/B) and the Flight Crew Operating Manual (FCOM) regarding takeoff procedures in icing conditions. The BFU specifically looked into the requirements for a static engine run-up when engine anti-ice is required due to temperatures below 3°C.
Findings
- The primary cause of the excursion was the increased speed during the takeoff roll on a snow-covered runway.
- The crew failed to perform a rolling takeoff according to the airline's OM/B, as the aircraft was not properly aligned with the runway centerline and the nose wheel steering was not neutral during the power increase.
- The required static engine run-up procedure was not performed, despite the necessity of engine anti-ice due to the freezing temperatures.
- A slight thrust imbalance between the left and right engines contributed to the directional instability.
- The continuous snowfall prevented the runway from being completely cleared of snow, maintaining a slippery surface despite active snow removal efforts.