What happened
During the landing roll phase of flight, the nose gear of the aircraft settled onto the runway, at which point the plane experienced a sharp veer to the right. Despite the crew's attempt to apply the left brake, the aircraft failed to correct its course. The plane subsequently skidded off the runway and collided with a runway marker. This impact caused the nose landing gear to collapse and resulted in structural damage to the fuselage.
Findings
Investigations determined that the steering actuator had failed, leading to a complete loss of hydraulic fluid from the steering system. The steering actuator assembly, part number 1501-4, had recorded 5,938.0 hours of operation since its last overhaul or repair.
Metallurgical analysis of the nose gear steering actuator cylinder identified that the failure was caused by fatigue cracking. This cracking originated from an abrupt machining transition located between the 45-degree thread ring chamfer and the straight wall of the cylinder. While engineering drawings suggested a continuous radius at the site of the fracture, the documentation lacked clarity regarding the intended transition between the internal threads of the nut and the adjacent radius.