The pilot reported that he returned from a local flight and was practicing touch-and-go landings at the airport in Upland, California.
During the second takeoff, as the Sonex gained altitude, the engine began to gradually lose power.
Unable to return to the runway, he initiated a precautionary landing to a strip of gravel perpendicular to the runway. During the landing, the right wing was substantially damaged.
The pilot reported that he did not believe there was problem with the engine, but that the problem was with the fuel-to-air mixture caused by the fuel pressure regulator not keeping a continuous constant pressure that led to the gradual loss of engine power.
Probable Cause: A gradual loss of engine power during takeoff due to the pressure regulator not keeping continuous fuel pressure which led to a precautionary off airport landing and collision with terrain.
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This April 2020 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.