What happened
On March 29, 2022, an Airbus A320-214, registration CC-BAS, was operating a scheduled passenger flight from Pereira to Cartagena via Rionegro, Colombia. During the approach to Rionegro (SKRG) on its previous leg, the crew encountered a nose wheel steering (NWS) fault. Following maintenance procedures under the Minimum Equipment List (MEL), the crew disconnected the NWS system, which left the nose wheel without cockpit-controlled directional steering, requiring the use of differential braking and engine thrust for ground maneuvering.
During the subsequent takeoff from Rionegero, the aircraft experienced intense vibrations during acceleration. After rotation, the crew received an ECAM alert for a landing gear shock absorber fault, accompanied by a strong smell of burning rubber. The crew discovered that a nose tire had burst. The pilots declared a MAYDAY and returned to Rionegro for an emergency landing. Upon touchdown on runway 01, the nose wheel was positioned at a 90-degree angle to the longitudinal axis of the aircraft. This impact caused the remaining nose tire to burst and detach from the rim, leading to significant metal-to-pavement abrasion. The aircraft eventually came to a stop approximately 1,984 meters from the initial contact point. There were no fatalities and no injuries among the 153 occupants.
The investigation
The GRIAA investigation focused on the electrical discrepancy within the Brake Steering Control Unit (BSCU) and the physical state of the nose landing gear. Investigators examined the relationship between the BSCU and the Rotary Variable Differential Transformers (RVDT) 3GC and 4GC. The technical analysis revealed a voltage monitoring discrepancy caused by a transient electrical discontinuity in the secondary voltages sent by the RVDT 3GC. Furthermore, the investigation reviewed the maintenance decision to defer the NWS system under the MEL and the crew's ability to monitor the nose wheel angle during taxiing using asymmetric thrust.
Findings
- The primary cause was the execution of a takeoff with the nose wheels turned 90 degrees to the left, which caused structural damage to the nose landing gear during the takeoff roll and exacerbated the damage during the emergency landing.
- A technical failure involving a voltage discrepancy between the BSCU and the RVDT sensors contributed to the initial steering fault.
- The decision to operate under the MEL allowed for the disconnection of the NWS, which prevented the crew from verifying the nose wheel's steering angle during taxiing.
- The crew was unable to effectively monitor the permissible steering angle limits while relying on differential braking and asymmetric thrust for ground control.