What happened
On January 6, 2017, a Neiva EMB-201A, registration PT-GUS, was performing an agricultural flight to apply fungicide to a rice plantation near Uruguaiana, Rio Grande do Sul. The aircraft departed from a landing strip located at Fazenda União.
Following the completion of the mission, the aircraft landed and was taxiing when the left main landing gear wheel detached. This failure was immediately followed by the breakage of the right landing gear. The loss of structural integrity caused the propeller spinner and blades to strike the ground, forcing the aircraft to rotate 90 degrees to the left. The aircraft sustained substantial damage, though the pilot escaped the incident uninjured.
The investigation
CENIPA investigators examined the wreckage and the left landing gear assembly. Laboratory analysis of the left axle performed by the Institute of Aeronautics and Space (IAE) revealed beach marks on the fracture surface, which are definitive indicators of metal fatigue.
Technical examination showed that the axle tube contained a stress concentrator caused by an abrupt change in section without a proper radius of curvature to minimize localized stress. This design flaw facilitated the nucleation and propagation of cracks through the fatigue mechanism. Investigators also noted that the landing area used for agricultural operations was in poor condition, characterized by numerous stones and undulations. The repetitive cyclic loads generated by the friction between the aircraft and the uneven terrain contributed to the fatigue of the axle.
Findings
- The primary cause of the failure was the rupture of the left landing gear axle due to fatigue.
- The presence of a stress concentrator on the axle facilitated the crack propagation.
- The precarious condition of the agricultural landing strip, featuring uneven terrain and stones, induced repetitive cyclic loads on the landing gear assembly.
- Inadequate flight planning by the pilot, who accepted operations in a high-risk area, contributed to the accident.
- Management failures within the operator, including inadequate operational supervision and a failure in risk management, allowed for marginal operations in substandard landing sites.
Safety action
CENIPA issued a recommendation to the National Civil Aviation Agency (ANAC) to work with the operator, Aeroarroz Aviação Agrícola Ltda., to improve their flight planning, management supervision, and risk management processes to enhance operational safety levels.