What happened
On April 20, 2011, an Airbus A320-211, registration EC-GRH, operated by Vueling, was performing a scheduled commercial flight from Barcelona to Seville. While cruising at flight level 350, the crew observed a Master Caution alert and an ECAM message indicating an ILS1 fault, accompanied by a temporary blanking of the commander's primary flight display (PFD). Shortly thereafter, a new warning regarding a nose wheel steering fault appeared.
During the final approach phase, as the landing gear was extended, a further warning regarding a landing gear shock absorber fault was triggered. This sequence of events resulted in the loss of the autopilot, autothrust, and flight director functions. According to the manufacturer' and airline's emergency procedures, the simultaneous occurrence of these specific faults suggested that the nose landing gear wheels might be rotated 90 degrees relative to the aircraft's longitudinal axis. This condition was visually confirmed by air traffic control during a low pass by the aircraft.
Despite the technical anomalies, the crew managed the approach to runway 27 with a 10-knot wind. The aircraft maintained the runway centerline and decelerated normally, coming to a stop near taxiway E3. There were no injuries among the 157 persons on board, and the aircraft sustained minimal damage.
The investigation
The CIAIAC investigation focused on the simultaneous occurrence of three independent technical failures. The investigation examined the aircraft's maintenance records, flight data from the SSFDR and CVR, and the crew's response to the emergency. Investigators analyzed the manufacturer's operational documentation to determine if adequate procedures existed for a landing under such conditions. The investigation also reviewed the physical state of the nose landing gear components and the steering control unit (BSCU) following the event.
Findings
- The incident was caused by the irreversible rotation of the nose landing gear wheels to a physical limit of 95 degrees relative to the longitudinal axis of the aircraft.
- Three independent failures occurred simultaneously, though the specific origin of the third failure could not be determined.
- The manufacturer's documentation lacked a specific procedure for landing when the nose wheels are suspected to be rotated 90 degrees.
- The crew's attempt to find a suitable procedure under pressure led to the consideration of conflicting actions that could have potentially worsened the situation had they been implemented.
Safety action
- The investigation issued a safety recommendation (REC 63/15) to Airbus SAS, requesting the development of a specific procedure for A320 aircraft to handle landings where the nose landing gear wheels are rotated 90 degrees or suspected to be so.