What happened
On July 31, 2016, a Boeing 737-800 operated by a German airline arrived at Stuttgart Airport from Varna, Bulgaria. The flight, carrying 188 passengers and 6 crew members, approached runway 25 using the Instrument Landing System (ILS) amidst scattered thunderstorm activity and rain.
Upon landing, the crew activated the thrust reversers, speed brakes, and the autobrake system. Flight data recorder analysis showed that these systems were deactivated once the aircraft's ground speed dropped to approximately 92 knots. As the aircraft transitioned from the runway to taxiway I, it maintained a speed of approximately 61 knots. However, while traversing taxiway I, the aircraft began to veer left. At 11:23:41 local time, the aircraft left the paved surface of the taxiway and came to a stop in a grassy area. There were no injuries among the passengers or crew, though the aircraft sustained light damage.
The investigation
The BFU investigation focused on the aircraft's deceleration and steering during the landing roll and taxiway transition. Investigators analyzed data from the Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR). The FDR confirmed the sequence of system activations and the specific moment the aircraft departed the taxiway centerline. The CVR revealed that the crew had briefed the landing configuration and discussed potential diversion routes due to the nearby thunderstorms, and had specifically noted the wet runway conditions during their briefing.
During interviews, the pilot flying reported that a large puddle of water was present in the transition area between runway 25 and taxiway I. He stated that the aircraft became uncontrollable in its direction of travel due to the water, resulting in significantly reduced braking effectiveness. The copilot noted that he had not been monitoring the ground speed during this period because he was occupied with other operational tasks.
Findings
- The primary cause of the excursion was loss of directional control caused by a large puddle of water located in the transition area between the runway and taxiway I.
- The presence of heavy rain and thunderstorm activity had created standing water on the movement area.
- The copilot was distracted by other operational duties and was not monitoring the aircraft's ground speed during the transition.