The experimental airplane experienced a propeller drive shaft failure and collided with the terrain during a forced landing at an airport. During the initial climb, about 300 to 400 feet above ground level, the engine surged and the airplane could not sustain lift. The engine was still producing power, but failed to distribute that power to the propeller. With a lemon grove directly ahead, the pilot opted to turn back to the runway to land. As he began a left turn toward the runway, the left wing impacted the dirt and the airplane "cartwheeled." Examinations revealed that the propeller hub had separated from the crankshaft. The tapered spacer, attached to crankshaft, had loosened. This instantaneous torque load to the crankshaft resulted in the propeller hub separating from the remaining taper, and the bolt unscrewing from the crankshaft.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:

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