What happened
Following departure from the departure airfield with approximately 50 gallons of fuel in each tank, the pilot climbed to 7,000 feet. While mid-way to the destination, the pilot attempted to switch the fuel source from the right tank to the left tank. This action was immediately followed by engine sputtering and a loss of power. Despite attempts to restore power by switching back to the right tank, adjusting the mixture to full rich, and testing various power settings, the engine failed to recover.
After notifying air traffic control of the engine issues and requesting an emergency landing at the nearest airport, the pilot informed the controller that the aircraft would be unable to reach the runway and would instead land in the water. The aircraft impacted the water and came to a sudden stop. The pilot and one passenger successfully exited the aircraft before it sank. There were 0 fatalities.
Findings
Data from the onboard engine monitor showed a rapid decrease in exhaust gas temperature, cylinder head temperature, and turbine inlet temperature across all cylinders, suggesting the engine was being starved of fuel. While the fuel selector was found in the right tank position following the accident, testing with low-pressure air revealed that fuel flow was blocked when the selector was moved to the left tank position.
Investigators discovered that a fuel selector valve, intended for a ferry tank, had been installed in the left fuel line between the factory selector and the left tank. This valve was found in the ON position, which obstructed the fuel path. The valve was located near the forward wing spar where the cockpit handles are accessed, making it susceptible to being accidentally moved by a person or object. Notably, the valve lacked a protective guard or safety wiring to keep it in the OFF position. Records indicated that while a ferry tank had been used for a global flight three years prior, there was no official documentation, such as an FAA Form 337, regarding the installation or removal of the ferry tank system.