ANC97LA036
ANC97LA036

On March 22, 1997, about 1225 Alaska standard time, an experimental homebuilt David Williams Kitfox, N9KF, crashed during a forced landing about 6 miles northeast of Wasilla, Alaska. The airplane was being operated as a visual flight rules (VFR) local area personal flight when the accident occurred. The airplane, registered to and operated by the pilot, received substantial damage. The certificated commercial pilot, the sole occupant, received minor injuries. Visual meteorological conditions prevailed.

The pilot reported in a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), on March 24, 1997, at 0850, that he was departing a private airstrip next to Wolf Lake, Alaska. The pilot departed from runway 6 after performing a stop-and-go. The airplane climbed to about 200 feet above the ground and the pilot heard a loud popping sound. The engine quit running and he made a turn toward a nearby road, about 1/4 mile northeast of the airstrip. The pilot made an emergency landing on the road, but the right wing struck a tree during the landing roll.

The pilot indicated the engine is a modified 98 horsepower Subaru engine that is produced by NSI Propulsion Systems, Arlington, Washington. The engine had accrued about 60 hours since being installed by the pilot. The propeller is not directly bolted to the crankshaft of the engine. The design utilizes a reduction gearbox between the crankshaft and the propeller. The design allows the propeller to free-wheel when not being powered by the engine.

Fuel pressure for starting a cold engine, is provided by an electric fuel pump which supplies fuel to a throttle body fuel injection system. The fuel pump is electrically powered via an electrical jumper wire from the battery bus to the pump. The pilot reported a postaccident examination of the engine revealed a broken electrical jumper wire. He also indicated there is not sufficient fuel flow without the fuel pump, to prevent an excessively lean mixture when the engine is operating at full power. The pilot indicated a lean mixture condition was confirmed by his examination of the spark plugs, which exhibited a clean and white appearance.

The engine manufacturer reported the throttle body only requires 1/2 psi of fuel pressure to operate. Fuel pressure, due to gravity flow from wing mounted fuel tanks, is sufficient to allow the engine to operate at a minimum of 75 percent power. In addition to gravity feed, the fuel system receives a slight pressurization while in flight from vent lines incorporated in the fuel tank caps. The manufacturer indicated as long as fuel flow is not interrupted, the engine will operate with, or without the fuel pump. They also indicated the popping sound described by the pilot, has been associated with an engine quitting due to an interruption of the fuel supply.

The engine manufacturer's handling instructions, section 6.6 "In-flight Engine Stop", states, in part: If ever you are faced with an in-flight engine stoppage, make sure the fuel selector is in the correct position and that the tank it is turned to does in fact have fuel. Check that the master power switch, ignition and fuel pump are all on and that no breakers have popped. Push the mixture control to the full rich position. Put the throttle in a half open position and push the starter button.

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