What happened
On December 13, 2016, an AT-502B agricultural aircraft, registration PR-AJF, was performing a pesticide spraying flight over the Caimbé I Farm in Primavera do Leste, Mato Grosso. The aircraft departed from a local landing area at approximately 19:00 UTC. About thirty minutes into the operation, the aircraft entered a steep descent and impacted the ground at a high angle and high energy. The impact caused the aircraft to be destroyed by the collision and subsequent fire. The pilot sustained fatal injuries.
The investigation
CENIPA investigators analyzed DGPS data and wreckage distribution to reconstruct the final moments of the flight. The investigation established that the aircraft was flying at 1-50 MPH (130kt CAS), which was 10 MPH above the established maneuvering speed (Va). The data showed that the pilot initiated an abrupt pitch-up maneuver, causing the aircraft to climb rapidly to 2,655 feet before the speed dropped to 81 MPH (70kt CAS) in just four seconds.
Physical examination of the wreckage revealed that the left horizontal stabilizer had detached in flight and was found 14 meters from the main wreckage site. Forensic analysis of the stabilizer assembly showed evidence of structural overload, including rivet loss and plastic deformation, consistent with excessive aerodynamic forces applied during the abrupt maneuver. The investigation also noted that the aircraft's flight logbook was destroyed by fire, making it impossible to verify the exact number of flight hours since the last inspection.
Findings
- The aircraft was operating above the recommended maneuvering speed (Va).
- An abrupt elevator command during a pitch-up maneuver caused a structural overload.
- The structural overload resulted in the in-flight detachment of the left horizontal stabilizer.
- The loss of the stabilizer caused an immediate loss of control and an unbalanced aerodynamic state.
- The pilot may have entered a stall condition while attempting to recover control due to the significant drop in airspeed.