What happened
On December 7, 2018, a Tecnam P92E, registration LV-S031, was conducting a local flight for pilot retraining near San Rafael, Mendoza. The flight, operated by Aeroclub San Rafael, included an instructor and a student pilot. During the execution of a simulated engine failure maneuver, the engine unexpectedly lost power and failed to respond when the crew attempted to apply power to climb.
Unable to maintain altitude, the crew performed an emergency landing in a field near Las Pared to the north of San Rafael. The aircraft struck the terrain, traveling approximately 60 meters before the nose gear detached and the aircraft overturned. While the crew escaped without injuries, the aircraft sustained significant damage to the engine and airframe, and the propeller was destroyed.
The investigation
The investigation focused on the engine's failure to respond during the transition from the simulated emergency to the recovery phase. Investigators examined the fuel system and the condition of the carburetors. While the mechanical fuel pump, spark plugs, and carburetor components were found to be in good working order, laboratory analysis of the fuel revealed that the aircraft was using automotive gasoline (mogas) rather than aviation-grade fuel.
Technical analysis of the right carburetor revealed a substantial amount of water and white oxide deposits at the base of the float bowl. These contaminants can interfere with the float's ability to maintain the proper fuel level, potentially leading to fuel starvation or power loss.
Findings
- The engine failure was triggered by contaminated fuel containing water and white oxide residues.
- The fuel used was automotive gasoline (mogas), which contains a higher ethanol content than permitted by the engine manufacturer.
- The use of automotive fuel with 12% ethanol increases the risk of vapor lock, a phenomenon where fuel turns to gas within the fuel lines, interrupting flow to the engine.
- The presence of water and oxidation in the right carburetor bowl likely compromised the fuel delivery system.