What happened
On December 18, 2013, an EMB-202 aircraft, registration PT-USM, was performing agricultural spraying operations over a soybean plantation near Tapurah, Mato Grosso. While the pilot was recovering from the third spray pass, the left wing detached from the aircraft's structure, folding upward at a 90-degree angle. This sudden structural failure caused the aircraft to roll sharply to the left, leading to a collision with trees and the ground in a densely forested area. The pilot sustained minor injuries, but the aircraft suffered substantial damage.
The investigation
CENIPA investigators examined the wreckage and the aircraft's maintenance history. The investigation revealed that the aircraft had previously been involved in an accident in 2008. While there were no official records of wing spar repairs following that 2008 event, physical evidence suggested the wing spar had been disassembled and improperly reassembled. Specifically, investigators found inverted bolts on the right wing and incorrect torque applied to the spar flange fasteners.
Furthermore, the investigation noted that during the most recent annual maintenance inspection (IAM) in October 2013, the required visual inspection for cracks and corrosion in the wing junction area was not formally signed off by the mechanic or the inspector. Advanced corrosion was discovered in the inspection area during post-accident examinations, suggesting that the recent inspection may not have been performed with sufficient rigor.