Cessna 172L N7869G accident near El Monte, California

Probable cause

A total loss of engine power due to contaminated fuel.

NTSB analysis

The pilot was conducting a night cross-country flight when, about 35 miles from the destination airport, the engine lost total power. The pilot diverted to a nearby airport but overshot the runway during the forced landing and impacted a drainage culvert parallel to the runway as well as a fence, resulting in substantial damage to the fuselage and left-wing spar.

A combination of blue-colored fuel, consistent with 100LL aviation fuel, and yellow-colored fuel, consistent in odor and color with fouled automotive fuel, was recovered from the airplane’s fuel tanks. Samples from both fuels tested negative for water contamination. Continuity of the fuel system was established from the main fuel tanks to the carburetor. An external fuel tank was attached to the fuel supply line, and the engine was subsequently started and operated through various power settings for about five minutes with no anomalies.

Although the airplane was equipped with a supplemental type certificate that permitted the use of automotive fuel, the owner stated that he only used aviation fuel. It is likely that some of the fouled fuel entered the fuel delivery system and did not support combustion, which resulted in a total loss of engine power; however, the source of the automotive fuel could not be determined. The pilot refueled the airplane with 100LL aviation fuel before departing on the flight, and the manager from that airport reported no anomalies with the fuel supply or delivery system. The pilot did not provide any information regarding his preflight inspection of the airplane before departure.

Text from the NTSB. Open the NTSB docket for WPR25LA004 for the full record.