What happened
On September 7, 2011, an EMB-2/2 aircraft, registration PT-UPB, was performing a ferry flight from Pinhão to Itaberaba, Bahia, for agricultural purposes. Approximately one hour and 20 minutes into the flight, the engine experienced a loss of power. The pilot attempted an emergency landing in an open field at Fazenda Pedregulho, in the municipality of Conceição do Coité. During the landing maneuver, the aircraft struck a protective fence, resulting in substantial damage to the airframe. The pilot was uninjured.
The investigation
CENIPA investigators found that the operator had initiated repairs at the accident site without the presence of investigators. During these unauthorized repairs, three fuel injectors were found to be obstructed. Investigators also noted that the fuel tanks had been replaced with tanks labeled for AVGAS, despite the aircraft being certified to operate with Hydrated Fuel Ethanol (AEHC).
Laboratory analysis of the fuel revealed that the ethanol used did not meet ANP specifications, showing high electrical conductivity, which suggests high corrosivity, and improper specific mass and alcohol content, indicating significant water and impurity contamination. This contamination likely led to the formation of a gelatinous substance that clogged the injectors. Furthermore, the investigation identified the use of a non-specification fuel filter (a bogus part) that differed significantly from the manufacturer's requirements in material, shape, and filtration capacity.
Discrepancies were also found in the aircraft's maintenance records. There was a significant mismatch between the total hours recorded on the engine tachometer (2806.2 hours) and the hours documented in the aircraft's logbooks (924.2 hours). Additionally, the aircraft's maintenance program appeared compromised, as there were no records justifying a previous engine overhaul that had occurred well before the manufacturer's recommended interval.
Findings
- Inadequate fuel quality and the use of non-compliant ethanol caused engine component corrosion and injector blockage.
- Use of an unapproved, non-specification fuel filter.
- Deficiencies in the aircraft maintenance program and lack of proper oversight.
- Discrepancies in aircraft hour tracking between the tachometer and official documentation.
- Inadequate management supervision regarding maintenance and fuel testing protocols.