What happened
On July 17, 2016, a Neiva EMB-202A, registration PT-UUW, was conducting agricultural spraying operations in a banana plantation near Cajati, São Paulo. The aircraft, operated by Banaer Pulverização Agrícola Ltda., had departed from a landing strip at Fazenda Eldorado to apply pesticides in rugged terrain. During the eighth takeoff of the day, while the aircraft was at an altitude of approximately 150 feet, the pilot experienced a loud noise from the engine followed by smoke entering the cockpit.
Recognizing a significant loss of power, the pilot immediately jettisoned the remaining 400 liters of pesticide payload and executed a forced landing in a nearby field. Although the aircraft sustained substantial damage, the pilot escaped the wreckage uninjured.
The investigation
CENIPA investigators examined the Lycoming IO-540-K1J5 engine to determine the cause of the power loss. While the engine did not suffer severe damage from the impact of the forced landing, investigators discovered that cylinder number 4 had completely detached from the engine flange. An inspection of the remaining cylinders (numbers 1, 2, 3, 5, and 6) revealed that the mounting studs were all tightened to a torque exceeding the manufacturer's specifications.
The investigation focused on the failure of the studs on cylinder number 4, which had all snapped. Analysis determined that the breakage occurred due to fatigue. Because no evidence of corrosion or physical damage was found on the studs, investigators concluded that the fatigue was caused by overtorquing the studs during a previous maintenance overhaul performed in November 2015.
Findings
- The engine power loss was caused by the detachment of cylinder number 4 during flight.
- The detachment resulted from the breakage of the cylinder studs due to a fatigue mechanism.
- The fatigue was induced by excessive torque applied to the studs during a maintenance overhaul.
- All other engine cylinders exhibited evidence of overtorquing on their respective studs.
- The pilot was fully qualified, with valid medical and agricultural ratings, and the aircraft was within weight and balance limits.
Safety action
CENIPA issued recommendations to the National Civil Aviation Agency (ANAC) to:
- Audit the maintenance processes of the organization responsible for the engine overhaul to ensure compliance with safety and quality management systems.
- Disseminate the findings of this investigation to engine maintainers working on Lycoming IO-540-K1J5 engines, emphasizing strict adherence to manufacturer torque specifications for cylinder studs.