Introduction
On a routine flight, a pilot departed from his home airport with approximately 50 gallons of fuel in each fuel tank. After climbing to 7,000 ft and proceeding toward his destination, he switched from the right fuel tank to the left fuel tank about halfway through the journey. Immediately after the switch, the engine began to sputter and lost power.
Accident Sequence
The pilot attempted to restore engine power by switching back to the right fuel tank, but there was no change. He then tried various power settings, adjusted the mixture to full rich, and switched tanks again, but the engine did not regain power. The pilot notified air traffic control (ATC) of the engine problem and requested to land at the nearest airport. ATC cleared him to land and instructed him to contact the control tower. However, the pilot advised the controller that he could not reach the airport and would land in the water. During the water landing, the airplane came to a sudden stop. The pilot and his passenger egressed, and the airplane sank.
Investigation
An annual inspection had been completed approximately two months prior to the accident. Test flights associated with the annual inspection were conducted with the fuel selector set to the right fuel tank; this was the first time the pilot had selected the left fuel tank since before the inspection. The airplane was equipped with an engine monitor capable of recording engine parameters. Examination of the data revealed that around the time of the power loss, exhaust gas temperature and cylinder head temperature rapidly decreased on all cylinders, along with a rapid decrease in turbine inlet temperature, indicating fuel starvation.
Examination of the wreckage found no evidence of preimpact failures or malfunctions of the airplane or engine that would have precluded normal operation. During fuel system examination, the fuel selector was found in the RIGHT fuel tank position, and low-pressure air confirmed it was correctly positioned. However, when the fuel selector was moved to the LEFT fuel tank position, continuity could not be established with low-pressure air.
Fuel System Examination
Further investigation revealed that a fuel selector valve labeled "FERRY TANK" was installed in the left fuel line between the factory-installed fuel selector and the left fuel tank. The ferry tank fuel selector was observed in the ON position, which blocked continuity from the left fuel tank to the engine. Continuity could only be established when the ferry tank fuel selector was in the OFF position. No continuity could be established from the ferry tank fuel line attached to the ferry tank's fuel selector.
The ferry tank fuel selector valve was mounted between the pilot and copilot seats on the forward side of the main wing spar, in the area where the pilot and copilot would normally enter and exit the cockpit. This location made the selector handle susceptible to inadvertent kicking or movement by a person or object. No guard was installed over the ferry tank fuel selector valve, nor was the selector valve handle safety wired in the OFF position to deactivate the valve, even though a ferry tank was not installed.
Review of the airplane's history revealed that about three years before the accident, the airplane had been used for an around-the-world flight by the pilot, and a ferry tank had been installed prior to that flight. A review of maintenance records did not reveal any logbook entries or associated paperwork for the ferry tank installation or removal, except for a copy of a one-page fuel system schematic from the maintenance manual with a handwritten annotation ("Tank") and hand-drawn lines added in blue ink. Federal Aviation Administration records showed no record of a FAA Form 337 (Major Repair or Alteration) or a supplemental type certificate for the ferry tank installation or fuel system modification.
Probable Cause
The official probable cause was the inadvertent activation of the unguarded ferry tank fuel selector valve, which resulted in fuel starvation and a total loss of engine power.