What happened
On November 13, 2012, a FAIRCHILD SA-226-TC, registration EC-JYC, operated by Zorex, was performing a ferry flight from Pamplona to Huesca. The aircraft had previously completed a passenger transport flight earlier that morning. During the takeoff roll on runway 05R at San Javier Airport, the aircraft began to veer to the left.
The pilot flying reached a speed of approximately 60 kt before releasing the nose wheel steering (NWS) button. Shortly after this release, the aircraft deviated from the centerline, crossing the edge of an access taxiway. The crew attempted to abort the takeoff at approximately 70 kt, with the captain applying asymmetric reverse thrust and braking to regain control. The aircraft eventually came to a stop near the intersection of the runway and the taxiway. The two crew members escaped without injury, though the aircraft sustained important damage, including propeller damage and a fuel leak caused by a wing impact.
The investigation
The investigation focused on the cause of the uncommanded left turn and the condition of the aircraft's nose wheel steering system. Investigators examined tracks left on the runway, which showed the front gear wheels skidding and the track width narrowing significantly during the deviation.
Maintenance records and physical inspections were conducted on the NWS system. While the system functioned normally during ground tests in both dry and wet conditions, investigators noted that the electrical wiring for the NWS actuators lacked adequate protection against moisture. The crew also reported that they had experienced irregular NWS operation during a flight the previous day but had not reported the issue to maintenance.
Findings
- The exact cause of the NWS malfunction could not be determined as it was not reproducible during testing.
- The lack of adequate protection for electrical wiring against moisture was identified as a potential factor, especially given the wet runway conditions at the time of the accident.
- The crew's use of asymmetric reverse thrust was a critical factor in limiting the extent of the runway excursion.
- The crew had failed to report a previously observed NWS anomaly to the maintenance department.
- The aircraft's operational structure, with geographically dispersed personnel, hindered effective communication between flight crews and maintenance technicians.