What happened
On November 17, 2019, a Petrel 912i, registration LV-FWL, was conducting a flight instruction mission departing from La Puntilla Aerodrome in Mendoza, Argentina. Approximately 30 minutes into the flight, the engine experienced a significant loss of power. The instructor attempted to follow emergency procedures, but as the power loss persisted, an emergency landing was executed in a plowed field.
While the pilot managed to land the aircraft parallel to the furrows of the field, the nose wheel collapsed after crossing a deep furrow, causing the aircraft to capsize. The incident resulted in substantial damage to the propeller, engine, and nose gear, though there were no injuries to the crew.
The investigation
The investigation examined the fuel used in the aircraft, which was sourced from the local aeroclub's tanker. Laboratory analysis of fuel samples recovered from the aircraft revealed that the engine was operating on automotive-grade gasoline (nafta súper).
Investigators noted that while Argentine regulations have historically prohibited the use of automotive fuel in aviation, the specific ethanol content in the fuel used was a critical factor. The investigation also examined the fuel filter, which contained a significant amount of compacted white fine dust, though the origin of this material remained undetermined.
Findings
- The aircraft was operating with automotive gasoline containing a 12% ethanol content.
- The Rotax engine manufacturer specifies a maximum allowable ethanol content of 10% for automotive fuel blends.
- The increased ethanol concentration likely caused vapor lock, a phenomenon where fuel vaporizes within the fuel lines, interrupting the flow of liquid fuel to the carburetors.
- Existing regulatory guidance from the National Civil Aviation Administration (ANAC) regarding the prohibition of automotive fuel was found to be outdated relative to current bioethanol mandates in Argentina.
Safety action
To address the identified risks, the JST recommended that the National Civil Aviation Administration (ANAC) re-evaluate the scope of its current fuel prohibitions. Specifically, the authority should assess which certified engines are compatible with current fuel blends and issue updated advisory circulars to ensure pilots and operators are informed of the risks associated with using high-ethanol automotive fuels.