Event
During the takeoff roll, light-colored smoke was observed trailing the aircraft. The pilot reported that at an altitude of 100 to 200 ft AGL, the engine lost partial power. He stated that he checked all controls and raised the landing gear. Witnesses reported that heavy smoke began trailing the aircraft at about that time, and the engine backfired and quit. The safety pilot then took control and attempted to return to the airport. Shortly thereafter, the aircraft stalled, descended out of control, and crashed at the edge of a lake.
Investigation
The reason for the initial power loss was not determined. After the accident, the electric boost pump was found in the HI position. The flight manual warned that the HI boost pump must not be used unless the engine-driven fuel pump had failed; otherwise, increased pressure from the HI boost pump would result in engine roughness; in some cases, engine combustion may cease. The engine operated normally in a test cell after the accident. When another engine was tested, loss of power occurred 3 to 5 seconds after the HI boost pump was activated. Additionally, a crack was found in the turbocharger inlet pipe, but duplication of this condition resulted in only a minor power loss.