What happened
On February 22, 2013, an EMB-201A aircraft, registration PT-GZM, was performing an agricultural spraying mission over a soybean plantation near Chapada, Rio Grande do Sul. The aircraft departed from the Boderguini Base to apply fungicide. After clearing the local vegetation, the pilot initiated a steeper dive to begin the application process. During this maneuver, the left wing detached from the aircraft in flight. The loss of the wing caused an immediate loss of control, leading the aircraft to strike trees. The impact destroyed the aircraft and resulted in one fatality.
The investigation
CENIPA investigators examined the wreckage and identified that the left wing separation was caused by a structural failure. Analysis of the wing spar revealed that a fatigue crack had developed in the lower flange of the spar. This crack propagated through approximately 70% of the flange section, significantly reducing its mechanical strength and eventually leading to a final rupture due to overload.
Investigators also found evidence of improper maintenance practices. Specifically, the fifth hole in the lower flange of the left wing spar exhibited coarse scratches and deformations. These marks were likely caused by the forced insertion of a pin into the hole, a method of assembly that creates stress concentrations and facilitates the initiation of fatigue cracks. Furthermore, the investigation noted that the right wing spar showed early-stage fatigue cracks in a similar pattern, suggesting a developing failure in the opposite wing as well. There were also indications that the aircraft had undergone previous repairs that did not adhere to the manufacturer's specifications.
Findings
- Maintenance of the aircraft: The presence of coarse scratches and deformations in the wing spar flange, caused by the forced insertion of a pin, contributed to the fatigue process.
- Organizational factors: The operator's structure allowed the pilot to be responsible for both flight operations and the management of aircraft maintenance requirements, which may have compromised oversight.
- Structural vulnerability: The fatigue failure was exacerbated by improper assembly techniques and previous non-standard repairs.
Safety action
CENIPA issued recommendations to the National Civil Aviation Agency (ANAC) to reinforce the importance of compliance with Service Bulletin (BS) 200-057-A005 among both aircraft operators and maintenance workshops.