What happened
On 26 September 2016, a Gulfstream G200, registration EC-KBC, was performing a domestic passenger flight from Madrid-Barajas to Barcelona-El Prat. The flight crew, consisting of two pilots, landed the aircraft on runway 25R at approximately 111 knots.
During the landing roll, as the crew applied the brakes, the aircraft suddenly began to veer to the left. The captain took control of the aircraft to correct the heading; however, the aircraft failed to respond effectively to the corrective inputs. Unable to maintain the runway centerline, the pilot allowed the aircraft to depart the side of the runway. The aircraft eventually came to a stop on a patch of sand between exits R3 and R4. There were no injuries to the two passengers or the two crew members, and the aircraft sustained no damage other than the nose gear.
The investigation
The CIAIAC examined the flight data recorder (DFDR) and cockpit voice recorder (CVR) to reconstruct the sequence of events. The investigation analyzed the aircraft's braking and steering systems, including the thrust reversers, rudder, and nose wheel steering. Investigators also reviewed maintenance records, the aircraft's hydraulic system, and the environmental conditions at the time of the incident.
Data revealed that three seconds after the activation of the thrust reversers, a momentary increase in left brake pressure occurred (428 psi) compared to the right brake (162 psi), which coincided with the sudden change in heading. While the crew attempted to apply asymmetric braking to the right to correct the path, the investigation found that the rudder had lost aerodynamic effectiveness because the aircraft's speed had dropped below 80 knots.
Findings
- The primary cause of the excursion was the inability to maintain the runway centerline due to differential braking, which triggered the initial deviation.
- A momentary application of the left brake caused a sudden change in direction.
- The crew's corrective rudder and braking inputs were ineffective in restoring the aircraft's heading.
- The rudder had no aerodynamic steering effect at the time of the correction because the indicated airspeed was below 80 knots.
- The aircraft's systems, including the brakes, thrust reversers, and nose wheel steering, did not exhibit any mechanical malfunctions.
- The investigation could not definitively determine why the aircraft's systems were unable to respond to the crew's corrective efforts.