What happened
On May 13, 2014, a Cessna 210N, registration PT-WHT, was performing a transport flight from Fazenda Rio Azul to Sinop, Mato Grosso, carrying a pilot and three passengers. During the landing roll on runway 21 at Sinop Airport (SWSI), the nose landing gear suddenly retracted. This caused the forward lower fuselage to make contact with the runway, dragging along the pavement until the aircraft came to a complete stop. The impact caused the propeller blades to strike the ground. All four occupants escaped the aircraft without injury, though the aircraft sustained damage to the propeller, engine, and landing gear.
The investigation
CENIPA investigators examined the nose gear actuator (PN 9882020-1) and sent it to the Aeronautics and Space Institute (DCTA) for laboratory analysis. The investigation revealed that the actuator had undergone unauthorized maintenance. Visual and stereoscopic examinations identified a fracture in a welded joint. The metallurgical analysis showed that the welding process was inefficient, characterized by voids and cracks that extended from the weld into the base metal. Additionally, investigators found evidence of improper surface preparation, including coarse sanding marks and corrosion due to a lack of surface protection. There were no records in the aircraft's logs indicating that this specific component had been installed or that any maintenance had been performed on it.
Findings
- The primary cause of the gear collapse was the failure of the nose gear actuator due to an unauthorized and defective weld.
- The welding process was poorly executed, creating structural vulnerabilities through voids and cracks.
- Inadequate maintenance supervision failed to detect the unauthorized repair on the component.
- The component was not a life-limited part, and its installation was not documented in the aircraft's maintenance logs.