Cessna 402C N594DM accident near Mercury, Nevada

Probable cause

A loss of power to both engines resulting from a fitting failure and leak at the right fuel selector valve that allowed fuel from the right tank to be lost overboard, and that then introduced air into the left engine's fuel lines during an attempted cross-feed operation.

NTSB analysis

During the flight, the right fuel gauge indicated a decreasing amount of fuel while the left fuel gauge was constant. The pilot attempted to cross-feed fuel from the left tank and he set the auxiliary pumps to LOW. He saw no indication on the fuel gauge of a decrease in the left tank, and the right tank gauge continued to show a decrease in fuel. The right engine lost power; he secured the engine and feathered the propeller. Shortly thereafter, the left engine lost power. Air traffic control provided vectors to the nearest airport and the pilot managed to glide to the airport, landing gear-up on the runway. A Federal Aviation Administration inspector responded to the accident site and found 12 ounces of fuel in the right fuel tank. The left fuel tank had ruptured with significant fuel staining evidenced on the ground under the left wing. An inspection of the airplane's fuel system revealed a leak at the flexible rubber fuel hose/hose clamp at the right fuel valve. No anomalies were found in the fuel system for the left engine. The fuel system has left and right main fuel tanks in wet wings that supply their respective engines in normal flight. An auxiliary fuel pump, located outside the tank in line between the tank and the fuel selector valve, provides fuel pressure for priming during engine start and to purge fuel vapor from the lines when necessary. In the event of an engine-driven fuel pump failure, the auxiliary pumps can provide adequate fuel for engine operation. The engine-driven fuel pumps are the main pumps for the system and draw fuel by suction from the tanks through the fuel valves. Two fuel selector handles in the cockpit move the fuel valves in the wings and have positions for each main tank, cross feed, and off. During normal flight, the left selector valve is positioned to the left tank and feeds the left engine, while the right selector valve is positioned to the right tank and feeds the right engine. Fuel may be cross-fed from either main tank to the engine(s) by positioning both selector valves to the desired fuel tank. With a fitting leak on one valve, a cross-feed selection for both engines could introduce air into the operating engine's fuel lines. An "OFF" position on each valve can be selected by pushing a center button on the selector, which would stop fuel to the corresponding engine-driven fuel pump.

Text from the NTSB. Open the NTSB docket for LAX08LA073 for the full record.