What happened
On January 11, 2010, an EMB-202A aircraft, registration PT-UTM, was performing agricultural spraying operations over a soybean plantation at Fazenda Sonho Verde in Primavera do Leste, Mato Grosso. During the second pass of the mission, approximately 15 minutes into the flight, the engine experienced a progressive loss of power. The pilot attempted to compensate by advancing the throttle, but receiving no response, jettisoned the spray load. The aircraft lost altitude and struck a contour line before sliding approximately 10 meters along the ground. The pilot escaped the wreckage uninjured, though the aircraft sustained severe damage to the propeller blades, engine, left landing gear, and spraying equipment.
The investigation
CENIPA investigators examined the engine and the fuel used during the operation. Post-accident disassembly of the engine revealed significant internal discrepancies, including heavy carbon deposits on the intake and exhaust valves, as well as the piston heads, and wear on the tappets and camshaft lobes. Testing of the fuel system components revealed impurities within the fuel injection and distribution units, which restricted fuel flow to the injectors.
Chemical analysis of the ethanol by the National Agency of Petroleum, Natural Gas and Biofuels (ANP) and specialized laboratories confirmed that the fuel was out of specification and contaminated with agricultural pesticides. Investigators also noted that the engine had undergone an unscheduled overhaul roughly 276 flight hours prior to the accident due to similar symptoms of power loss and metal shavings in the oil. The investigation focused on the fuel handling process, which involved manual refueling from drums using containers transported by truck and poured through a funnel.
Findings
- The primary cause of the engine failure was the use of contaminated ethanol containing agrochemicals.
- The presence of pesticides and non-specification ethanol led to heavy carbon buildup, causing valve sticking, low compression in cylinders #2 and #4, and potential pre-ignition or detonation.
- Impurities in the fuel created a gelatinous substance that restricted fuel flow to the injectors, preventing the engine from maintaining required power.
- The fuel handling process—involving manual transfer from drums to containers and then to the aircraft—was inadequate and allowed for contamination, likely via containers previously used for agrochemicals.
- The engine's previous unscheduled overhaul had identified similar issues, suggesting the degradation was a continuous process caused by the ongoing use of contaminated fuel.