What happened
On January 24, 2017, at approximately 19:45 UTC, a Cessna A-188B, registration PR-LKA, was performing an agricultural spraying mission near Fazenda Mateira in Caçu, Goiás. Shortly after departing from a landing strip on the farm, the pilot experienced a partial loss of engine power. The aircraft remained at an altitude of approximately three meters above the crops and traveled about 1,000 meters from the opposite end of the runway before performing a forced landing in a plowed field. The impact caused the aircraft to nose over, resulting in substantial damage to the airframe. The pilot was able to exit the aircraft uninjured.
The investigation
CENIPA investigators examined the engine and fuel systems to determine the cause of the power loss. While the fuel itself met required standards, the investigation revealed significant internal issues within the fuel delivery system. Analysis of the engine showed that half of the fuel injectors were obstructed by debris. This debris was identified as corrosion products resulting from the direct contact of aluminum components with ethanol fuel.
Specifically, the fuel distributor was found to lack the surface treatment required by the manufacturer for ethanol compatibility, triggering an oxidation reaction. Furthermore, the mechanical fuel pump was found to be nearly inoperable; testing showed a pressure of only 4 psi, far below the required 55 psi. Investigators discovered corrosion on the pump's relief valve and noted an attempt to reseat the valve's ball rather than replacing the pump body as recommended. Additionally, the investigation found that the aircraft's takeoff weight was approximately 1,726 kg, which exceeded the maximum takeoff weight of 1,498 kg listed in its Certificate of Airworthiness.
Findings
- Fuel system failure caused by corrosion and obstruction of fuel injectors.
- Use of ethanol fuel in aluminum components that lacked the necessary manufacturer-specified surface treatment.
- Inadequate maintenance practices, including the failure to replace corroded fuel lines and an improper attempt to repair the fuel pump.
- Overweight takeoff, with the aircraft exceeding its maximum takeoff weight by approximately 228 kg.
- Inadequate flight planning and operational decision-making regarding weight and performance.