What happened
On September 14, 2019, a Tecnam P92 Eaglet, registration LV-S058, was conducting a private recreational flight departing from Cañuelas Aerodrome in Buenos Aires. After approximately 30 minutes of flight in visual meteorological conditions, the aircraft's engine suddenly stopped while in cruise flight. The pilot attempted to restart the engine without success and subsequently performed an emergency landing in a rural area of San Vicente. During the landing sequence, the aircraft struck the terrain on its nose gear, causing the gear to detach and resulting in damage to the engine cowlings. The pilot exited the aircraft on his own and sustained no injuries.
The investigation
The investigation examined the aircraft's fuel system, the quality of the fuel used, and the technical documentation provided by the manufacturer. Investigators analyzed fuel samples from both tanks. The left tank contained approximately 0.5 liters, while the right tank held roughly 3 and 0 liters. Laboratory analysis revealed that the fuel used was automotive-grade fuel (Grade 3) rather than aviation fuel, and it contained a high concentration of suspended solids, specifically silica.
Furthermore, the investigation scrutinized the design of the fuel tank opening valves. It was noted that the valves for the two tanks utilized an inverted mechanical logic; moving the valve in one direction opened the tank, while the same movement on the opposite side closed the tank. The investigation also reviewed the aircraft's illustrated parts catalog, finding inconsistencies in language use (English and Italian) and a lack of specific part numbers for certain components.
Findings
- The engine failure was likely caused by an interruption in the fuel supply.
- The fuel selector valve for the right tank was found to be in the closed position at the time of the engine failure.
- The inverted operational logic of the fuel tank valves created a significant operational risk, as it could induce human error by prompting the pilot to inadvertently close the fuel supply.
- The aircraft was operating with automotive-grade fuel, which is prohibited by Argentine civil aviation regulations (ANAC 224/2010) due to high bioethanol content and potential for engine issues.
- The aircraft's parts catalog lacked unique part numbers for certain components and used mixed languages, which could complicate maintenance and part replacement.