What happened
On 21 March 2019, a Sri Lankan Airlines Airbus A320, registration 4R-ABN, was completing a scheduled passenger flight from Colombo to Singapore Changi Airport. During the landing phase on Runway 02L, the aircraft encountered heavy rain and a significant crosswind.
As the aircraft descended, the pilot flying disengaged the autopilot at approximately 190 feet above ground level. Immediately following this, the aircraft began a progressive deviation to the right of the runway centerline. Despite the pilot attempting to correct the roll and rudder position, the aircraft touched down to the right of the centerline. During the subsequent landing roll, the aircraft skidded toward the right edge of the runway, striking and breaking a runway edge light near taxiway W7. The crew eventually managed to steer the aircraft back to the center of the runway and exited via Taxiway W4 without further incident.
The investigation
The investigation examined flight data from the aircraft's Digital Aircraft Condition Monitoring System Recorder (DAR). The analysis revealed that a gust of wind occurred during the flare, which, combined with right-hand roll inputs from the pilot, contributed to the lateral drift.
Investigators also looked into the use of the Nose Wheel Steering (NWS) tiller. At a groundspeed of approximately 110 knots, the pilot attempted to use the tiller to steer the aircraft back to the centerline. However, the investigation established that the NWS tiller is inhibited at speeds above 80 knots, meaning the input was ineffective for directional control at that velocity.
Findings
- The aircraft's deviation was caused by the cumulative effect of right roll inputs and an increasing left crosswind.
- The flight crew failed to execute a go-around despite the approach becoming destabilized.
- The pilot attempted to use the NWS tiller at a speed where the system was non-functional.
- The crew did not file an occurrence report, which meant the damaged light remained a potential foreign object debris (FOD) hazard until discovered six hours later.
Safety action
The Civil Aviation Authority of Sri Lanka mandated that the operator provide additional training for the involved pilots regarding landings in wet and low-visibility conditions. Furthermore, the operator was required to review training policies to improve the Pilot Monitoring's ability to identify and call for a go-around during unstable approaches.