What happened
On January 22, 2021, at approximately 11:50 UTC, an EMB-202A agricultural aircraft, registration PT-UTU, was performing pesticide application duties over a rural area in Leme, São Paulo. The aircraft, operated by Aeromaj Aviação Agrícal Ltda, was flying in favorable meteorological conditions when the pilot experienced a sudden engine failure.
According to the pilot, the event began with an audible "bang," immediately followed by significant vibration, a loss of engine power, low oil pressure, and high oil temperature. Recognizing the critical nature of the failure, the pilot executed an emergency landing in a nearby sugarcane plantation. The aircraft sustained substantial damage, but the pilot emerged from the wreckage uninjured.
The investigation
CENIPA investigators examined the Lycoming IO-540-K1J5 engine to determine the cause of the power loss. The inspection revealed ruptures in the engine block, specifically near cylinder #6, and widespread oil leakage. While the combustion chamber, valves, and lubrication system showed no signs of overheating or operational discrepancies, investigators found a significant amount of metal debris (shavings) in both the primary and main oil filters, as well as within the engine crankcase. The oil pump was also found to be seized.
Laboratory analysis of the connecting rod from cylinder #6 showed that the rod cap bolts had ruptured and the rod head was deformed. However, the severity of the subsequent impacts caused plastic deformation in the broken components, which likely masked the original failure mechanism. Investigators noted that the engine had undergone a major overhaul in March 2019 following a previous ground collision.
Findings
- The engine failure was directly linked to the failure of the cylinder #6 connecting rod.
- The specific mechanism that caused the initial failure of the rod cap bolts and the rod head remains undetermined due to impact-related masking.
- Two hypotheses were considered: improper torque applied to the bolts during maintenance (leading to accelerated fatigue) or a manufacturing/handling defect in the bolts that introduced micro-cracks.
- The pilot was fully qualified, with valid medical certification and appropriate agricultural flight ratings.
- The aircraft was within weight and balance limits and had valid airworthiness documentation.