What happened
On February 4, 2020, an Embraer EMB-201A, registration PT-UED, operated by São Bento Aviação Agrícola LTDA, departed from the Santo Ângelo Aerodrome (SBNM) in Rio Grande do Sul for a local test flight. The flight was intended to verify the engine's performance following recent maintenance work.
During the flight, the pilot noticed the aircraft was failing to gain sufficient airspeed. As the aircraft entered the final approach for landing, the engine ceased operation. Despite the pilot's attempt to restart the engine by activating the electric fuel pump, the power loss continued. The pilot subsequently performed a forced landing in a nearby plantation. The aircraft sustained substantial damage, but the pilot emerged uninjured.
The investigation
CENIPA investigators examined the engine, a Lycoming IO-540-K1J5D that had been converted for use with ethanol. While the lubrication and ignition systems showed no signs of contamination or failure, the investigation identified significant discrepancies in the fuel and ignition settings.
Testing revealed that the engine was operating with an excessively rich air-fuel mixture. This was attributed to the use of an automotive electric fuel pump, which lacked a pressure regulator. This pump operated at 4 bar, significantly exceeding the 2.41 bar required for ideal operation, leading to an oversupply of fuel to the injectors. Additionally, the investigation found that the magneto ignition advance was set to 35° BTDC, whereas the identification plate specified 20° BTDC. This advanced timing caused the combustion to begin too early, resulting in a loss of useful engine power.
Findings
- Inadequate maintenance services, specifically regarding improper engine adjustments and the use of an uncertified automotive part without established technical parameters for the aircraft.
- Inadequate management supervision, which allowed the aircraft to be released for flight despite these technical discrepancies.
- The use of an automotive fuel pump that provided excessive pressure to the fuel system.
- Incorrect ignition timing settings on the magneto.