What happened
On December 18, 2020, a Cessna A188B agricultural aircraft, registration PT-WKN, departed from the Usina Floresta landing strip in Santa Helena de Goiás, Brazil. The flight was intended to be a repositioning flight to the General Leite de Castro Aerodrome in Rio Verde for maintenance. Shortly after takeoff, the aircraft experienced a sudden loss of engine power. The pilot was forced to perform an emergency landing in a nearby sugarcane field. While the aircraft sustained substantial damage, the pilot emerged from the crash uninjured.
The investigation
CENIPA investigators examined the engine, specifically a Continental IO-520-E, and the fuel system. The investigation focused on the implications of the aircraft's modification to operate on ethanol (hydrated ethyl alcohol). The aircraft held a valid Special Flight Authorization (AEV) for this purpose.
During the technical analysis, investigators found that the fuel distributor exhibited severe corrosion caused by ethanol use, and aluminum hydroxide gel was present inside the distributor body. Furthermore, the fuel pump showed significant internal corrosion and an obstructed jet, which caused fluctuations in fuel pressure and flow during functional testing. Additionally, a fuel pressure hose leading to the instrument panel was found to be improperly tightened, lacking the necessary torque.
Findings
- The primary cause of the power loss was the fluctuation in fuel pressure and flow caused by a chemical reaction between the ethanol and the aluminum components within the fuel pump jet.
- Inadequate aircraft maintenance and inadequate management supervision were the contributing factors to the accident.
- The operator had not sufficiently addressed the recommendations regarding material compatibility with ethanol, specifically concerning the corrosive effects on engine components.