What happened
On May 25, 2015, a Scandinavian Airlines Boeing 737-800, registration LN-RCZ, landed at Oslo Airport, Gardermoen, under challenging weather conditions involving rain and thunderstorms. At the time, the western runway (01L) was undergoing resurfacing, which had shortened the usable landing distance from 3,600 meters to 1,928 meters. The final 300 meters of the runway consisted of a concrete surface that was noted as being slippery when wet.
Despite the aircraft maintaining a stable approach, the crew encountered significant difficulty decelerating after touchdown. The aircraft failed to stop within the paved surface and exited the runway at the northern end, eventually coming to a halt approximately 50 meters inside the Runway End Safety Area (RESA). The impact with runway light fixtures caused minor damage to an engine cowling and one of the main wheels, but there were no injuries to the 178 passengers or the crew.
The investigation
The Norwegian Safety Investigation Authority (NSIA) examined the runway conditions, the aircraft's performance, and the decision-making processes of both the flight crew and air traffic services. The investigation focused on why the aircraft was unable to stop on the available distance and why the landing configuration chosen by the crew was insufficient for the environmental factors present.
Investigators analyzed the runway's friction levels, noting that the concrete section had low texture, which likely contributed to hydroplaning. They also reviewed the air traffic control logs, which showed that the runway direction had not been changed to mitigate the effects of a developing tailwind, and examined the airline's internal procedures regarding landing calculations on shortened runways.
Findings
Several critical factors contributed to the runway excursion:
- Inadequate landing configuration: The captain selected a landing configuration using flaps 30 and autobrake 3 based on previous experience. However, calculations using the Onboard Performance Tool (OPT) would have shown that this configuration required 1,887 meters of distance, exceeding the available 1,628 meters.
- Delayed use of thrust reversers: The crew did not apply full thrust reverser power until 22 seconds after landing, missing the most critical phase for deceleration.
- Environmental risks: The runway surface was highly slippery due to the smooth concrete texture and heavy rain. Furthermore, the aircraft landed with a tailwind of approximately 6 knots, which had been communicated to the crew by the tower but was not acted upon.
- Operational oversight: Airport authorities and air traffic services had not sufficiently assessed the combined risk of a shortened runway, a slippery concrete patch, and tailwind conditions during the resurfacing project. The existing NOTAM provided limited decision support for pilots.