What happened
On December 5, 2022, a Boeing 737-8AS was performing a stabilized CAT-II ILS autoland at Dortmund Airport. The aircraft touched down in the middle of the touchdown zone on runway 06. Although the crew had calculated the required landing distance based on the latest available weather information and the reported Runway Condition Code (RWYCC), the aircraft could not be brought to a halt within the paved runway surface. The aircraft eventually came to a stop on the cleared area (clearway) located behind the end of runway 06.
There were no injuries to the crew, and the aircraft sustained no damage during the event.
The investigation
The BFU investigation focused on the discrepancy between the reported runway condition and the actual state of the pavement at the time of landing. Investigators analyzed flight data from the Digital Flight Data Recorder (DFDR) and reviewed the runway condition reports provided to the crew. The investigation also examined the runway assessment procedures used by the airport operator and the landing performance calculations performed by the crew using the Boeing Onboard Performance Tool (OPT).
Findings
- The crew performed a stabilized autoland using the most recent weather reports available to them.
- The landing distance required (LDR) was calculated to be within the available landing distance (LDA) based on the reported RWYCC of 5/5/5, which indicated the runway was not contaminated.
- Continuous precipitation occurred between the time of the runway assessment and the aircraft's touchdown, resulting in a surface covered in wet snow.
- This accumulation of wet snow led to reduced braking effectiveness of the main landing gear wheels.
- The runway condition reported by the air traffic controller eight minutes prior to landing likely did not reflect the actual state of the runway at the moment of touchdown.