What happened
On January 29, 2023, at approximately 13:30 UTC, a Neiva EMB-202 aircraft, registration PT-URB, was performing an agricultural spraying mission over a soybean plantation near Marcelândia, Mato Grosso. The aircraft departed from the Fazenda Tupã landing strip with one pilot on board.
While flying over a densely forested area, the engine experienced a gradual loss of power. In an attempt to manage the emergency, the pilot jettisoned the chemical load and executed a forced landing into the soybean crop. The aircraft struck the ground and overturned, resulting in substantial damage to the airframe. The pilot sustained minor injuries and was the sole occupant of the aircraft.
The investigation
CENIPA investigators examined the engine, components, and maintenance records of the PT-URB. The investigation included bench testing of the fuel injection servo and laboratory analysis of the engine oil.
Technical tests revealed that the fuel injection servo was delivering fuel at rates below the manufacturer's minimum requirements when operating with a rich mixture setting. Furthermore, laboratory analysis of the engine oil conducted by the National Agency of Petroleum, Natural Gas and Biofuels (ANP) found that the lubricant's kinematic viscosity was significantly lower than the standard range for aviation oils (9.85 cSt compared to the required 10-30 cSt). The analysis also detected ester, indicating that the oil had been contaminated with vegetable oil.
During the engine disassembly, investigators found evidence of carbonization on the piston heads, sediment accumulation, and non-uniform coloring on the piston skirts. Additionally, marks characteristic of pre-ignition were identified.
Findings
- The engine was operating with a fuel flow below the minimum specified limits.
- The engine oil was contaminated with vegetable oil and was sub-additivated.
- Improper engine oil replenishment with unauthorized fluids likely caused reduced lubrication efficiency, increased operating temperatures, and pre-ignition.
- The engine was unable to deliver its full rated power due to these combined factors, increasing the risk of power loss.
- Maintenance of the aircraft contributed to the occurrence.