What happened
On May 06, 2016, at approximately 1200 Pacific daylight time, an ANTONOV AN2, registration N2AN, was conducting a familiarization flight from Cable Airport in Upland, California, toward San Bernardino International Airport. While entering the crosswind for runway 24, the pilot engaged the carburetor heat and switched the fuel tank selector to the right tank. Immediately following these actions, the engine suffered a total loss of power.
Despite multiple restart attempts, the engine remained inoperative. Unable to reach the airport, the pilot executed a forced landing in a small field within a residential area. During the approach, the aircraft struck a power line. Upon touchdown, the airplane nosed over and came to rest inverted. The impact caused substantial damage to the wings and fuselage. The pilot and the single passenger were not injured.
The investigation
NTSB investigators examined the fuel system and discovered approximately 16 ounces of water. This water was located in the lower gascolator, the fine fuel filter, and the fuel line leading to the carburetor inlet. Additionally, corrosion, water, and rust were found on a brass screen at the carburetor inlet and two carburetor fuel bowl thumb screens.
Maintenance records indicated that the aircraft inspection checklist required washing the carburetor and main fuel filter every 50 hours, and cleaning or replacing the fine fuel filter every 100 hours. The fine fuel filter is located on the left side of the firewall and is not easily accessible or drainable during a standard preflight inspection. The mechanic responsible for the most recent inspection stated that the fine fuel filter was not drained or checked. The last documented cleaning of the fuel filters occurred in September 2012.