This January 2010 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.
Aircraft: Czech Sportcruiser. Injuries: 2 Minor. Location: La Quinta, Calif. Aircraft damage: Substantial.
What reportedly happened: Prior to the flight the pilot conducted a preflight inspection, which included taking samples of fuel from the fuel sump drains. No contamination was found. While en route to his destination, the pilot decided to switch the fuel supply to come from the left tank rather than the right, in an effort to remedy a slight fuel imbalance. Shortly after changing the tank selection, the engine lost all power. The pilot was unable to restart the engine and initiated a forced landing in a field.
During the post-accident examination, investigators observed a small amount of water originating from the engine inlet fuel line at the firewall. The engine-driven fuel pump contained residual water. In addition, the carburetors were examined and disassembled; a white paste-like and flaky substance was noted within both carburetor float bowls. One carburetor float bowl contained about two ounces of a milky white liquid, which tested positive for water. The engine was installed on an engine test stand and run at various rpm settings before being shut off using the mixture control lever.
Probable cause: A loss of engine power during cruise flight due to water contamination in the fuel.
For more information: NTSB.gov. NTSB Identification: WPR10LA119.