What happened
On March 8, 2023, an airBaltic Airbus A220-300, registration YL-AAP, was performing a scheduled flight from Paris Charles de Gaulle to Riga International Airport. During the landing roll on runway 18, the aircraft began to deviate to the right of the centerline and started skidding.
As the aircraft decelerated, the pilot attempted to maintain directional control using rudder inputs and later by advancing the throttles above idle to prevent drifting downwind. However, the aircraft continued to yaw and drift toward the right side of the runway. The pilot eventually applied heavy manual braking, which caused the wheels to lock. The aircraft subsequently slid uncontrollably, with the nose landing gear leaving the paved surface and coming to a stop approximately 11 meters from the runway edge near taxiway J. There were no injuries to the 89 passengers or the crew.
The investigation
The TAIIB examined flight data recorder (FDR) and cockpit voice recorder (CVR) data, aircraft maintenance records, meteorological reports, and airport runway condition reports. The investigation focused on the interaction between the aircraft' braking systems and the contaminated runway surface. Investigators analyzed the performance of the anti-skid protection and the brake control system (BCS) during the ground roll, specifically looking at how the difference in wheel rotation speed and ground speed affected the aircraft's stability.
Findings
- The runway surface was contaminated with snow and ice, with conditions changing rapidly due to the weather.
- The deficiencies in the operation of the aircraft brake control system prevented effective anti-skid protection.
- A significant difference in friction coefficients across the runway surface likely contributed to the skidding.
- The anti-skid protection deactivated because the difference between the wheel rotation speed and the aircraft's ground speed triggered a system response that led to wheel blocking.
- The pilot's attempt to use manual braking, while intended to correct the direction, ultimately contributed to the wheels locking and the subsequent loss of control.
- There were inaccuracies in the assessment of the runway condition by airport personnel during the period of rapidly changing meteorology.
Safety action
- The TAIIB issued a recommendation to the Riga International Airport operator to review training programs for runway surface assessment, especially during adverse weather, and to consider additional measurement technologies to reduce human error.
- A recommendation was issued to Airbus Canada Limited Partnership to finalize enhancements to the Brake Control System to improve anti-skid performance on contaminated surfaces and prevent the deactivation of anti-skid protection.