What happened
On 28 May 2006, an Airbus A3 .320, registration EC-JDK, operated by Vueling, was climbing through FL325 en route from Barcelona to Santiago de Compostela. While flying on airway UN-725, the aircraft encountered intense turbulence that caused it to bank sharply to the right. Although the autopilot attempted to compensate, the intensity of the motion caused the aircraft to bank significantly, reaching angles of up to 49 degrees to the right and 33 degrees to the left.
As the aircraft's stability was compromised, the crew disengaged the autopilot and took manual control. During the encounter, the aircraft experienced rapid fluctuations in pitch and altitude, eventually descending to FL303. The violent motions resulted in seven minor injuries among the passengers and flight attendants.
The investigation
The CIAIAC investigation examined flight data recorder (DFDR) and cockpit voice recorder (CVR) information, as well as maintenance records and crew training history. The analysis focused on the aircraft's flight control inputs, the aerodynamic impact of the turbulence, and the crew's adherence to established procedures for severe turbulence and dual sidestick inputs.
Investigators also reviewed the flight path of preceding traffic to determine the source of the disturbance. Following the incident, the aircraft underwent specialized inspections in Zurich to ensure that the high lateral acceleration loads, which reached +0.47g, had not caused structural damage. These inspections confirmed the aircraft was airworthy.
Findings
- The primary cause of the turbulence was the wake turbulence from a preceding Airbus A340-300, which was flying on the same airway approximately 10.13 NM ahead of the aircraft.
- The crew's response to the turbulence exacerbated the situation; specifically, the pilots provided simultaneous, opposing sidestick inputs and utilized the rudder in a manner inconsistent with standard procedures.
- The crew failed to strictly follow severe turbulence procedures by retarding the throttles and disconnecting the autothrust, which caused the airspeed to drop below the recommended level for such conditions.
- The aircraft's flight control system and structural integrity remained within design limits despite the high lateral loads.