A Sun Express Germany Boeing 737-800, registration D-ASXO performing flight XG-3264 from Varna (Bulgaria) to Stuttgart (Germany), landed on Stuttgart's runway 25 and slowed to about 35 knots over ground at about 11:23L (09:23Z). While turning off the last high speed turn off taxiway I the aircraft could not follow the turn and went into the grass between runway, taxiways I and K coming to a stop within the runway protected area. There were no injuries, the aircraft received minor if any damage.
The airport was estimated to remain closed for about 4 hours.
On Nov 23rd 2016 Germany's BFU released their July Bulletin reporting that the captain (34, ATPL, 7,550 hours total, 7,360 hours on type) was pilot flying, the first officer (40, ATPL, 4,170 hours total, 72 hours on type) was pilot monitoring. Tower cleared the flight to land on runway 25 reporting winds from 190 degrees at 4 knots. The aircraft touched down in the landing zone with a speed of about 150 KIAS (landing mass 59 tons), immediately after touch down speed brakes and thrust reversers were deployed, the brakes pressure increased to about 1000 psi. The aircraft began to turn off the runway onto taxiway I at 61 KIAS, already on the taxiway the brakes pressure increased to the maximum of 3000 psi, the aircraft went off the edge of the taxiway at 23 knots and came to a stop with all gear off the paved surface of the taxiway.
The BFU reported the captain told in a post flight interview a larger puddle of water was in the area between runway and turn off. The aircraft crossed the runway edge with a speed of about 30 knots, directional control was lost when the aircraft went through the puddle.
ON Aug 27th 2020 the BFU released their final factual report without analysis or conclusions.
The BFU summarized the sequence of events (all times in local time):
At about 1119:231 hrs during approach to Stuttgart, the co-pilot established contact with the tower controller. At 1121:19 hrs the crew received landing clearance [Call sign], India approved, wind 190 degrees, 4 knots, runway 25 cleared to land with the addition to leave runway 25 via taxiway I and wait ahead of taxiway S. There was no taxi clearance to taxi on to the apron.
The aircraft touched down within the touchdown zone of runway 25 with a ground speed of about 150 kt and a landing mass of approximately 59 t. Immediately after touchdown thrust reverser and speed brakes were activated. The landing gear brakes were controlled by the auto brake system. The FDR data showed as to when individual systems were activated and deactivated. Speed brakes, thrust reverser and auto brake system were deactivated at a ground speed of about 92 kt.
In the following time span of about 12 s the wheel brakes were not activated. Aircraft speed decreased from about 92 kt to about 82 kt.
Brake pressure increased to approximately 1,000 psi as the aircraft was abreast of taxiway H with a taxi speed of about 82 kt. Then the aircraft turned from runway 25 on to taxiway I with a taxi speed of about 61 kt.
On taxiway I brake pressure increased to the maximum of 3,000 psi. At 1123:41 hrs, the aircraft left taxiway I towards the left with a speed of about 23 kt and came to a stop in the grass. At 1136 hrs, the operations control officer and a paramedic entered the aircraft via a scaling ladder. The passengers disembarked via service door 1R and mobile stairs. Airport buses took the passengers to the terminal.
During a BFU interview, the PIC stated that a larger water puddle had existed in the transition area between runway 25 and taxiway I. According to his statement, the aircraft had had a taxi speed of 30 kt at most during the turn from runway 25 on to taxiway I and due to the water no longer been controllable in its moving direction. Braking action had been low.
The co-pilot stated that he had not paid attention to the taxi speed because he had been busy with operating activities.
The BFU described the weather:
According to the METAR of 0850 hrs, a thunderstorm with rain passed the area of the airport.
Figure 2 shows the operating areas covered with puddles shortly after the
occurrence. The photo was taken from the cockpit immediately after the aircraft had come to a stop.
With respect to the Cockpit Voice recorder the BFU reported:
The data of the occurrence flight the FDR had recorded was downloaded, analysed and stored by the BFU laboratory. The CVR had recorded 4 very short audio sequences. The examination of the CVR showed no technical deficiencies and download of the files occurred without problems. The CVR had recorded a Log file.
According to the manufacturer it is proof that audio tracks had been deleted. It was possible to restore the deleted files.
The restored CVR audio tracks showed that the flight crew conducted an approach briefing, discussed the aircraft landing configuration and completed the checklists corresponding with the respective flight phase.
Due to the thunderstorm cells in the vicinity of the airport possible alternate routes for a possible go-around procedure were discussed. The wet runway was also part of a briefing.
Related NOTAM:
A4375/16 - RWY 07/25 CLSD DUE TO ACFT ACCIDENT. 31 JUL 10:33 2016 UNTIL 31 JUL 13:15 2016. CREATED: 31 JUL 10:34 2016