Accident Sequence
The pilots were conducting flight instructor training and practicing power-on and power-off aerodynamic stalls. During an uncoordinated stall, they performed a spin recovery, after which the engine lost power. The pilots were unable to restart the engine and forced landed the airplane on a road that featured a 90-degree turn. While exiting the turn, the left wheel went into the soft shoulder, causing the airplane to ground loop and strike a fence.
Previous Incidents
The engine had recently been overhauled, and the airframe was stored during that time. After the engine was reinstalled in the airframe, there were two previous occasions when the engine quit. On the first occasion, maintenance personnel increased the idle rpm. On the second occasion, they replaced the fuel servo, which had recently been overhauled with the engine.
Post-Accident Examination
Following the accident, the engine was run on the airframe, and no evidence of mechanical failure or malfunction was found. However, particle contamination was discovered in the fuel in the header tank. Additionally, the inverted fuel vent was found to be over 50 percent obstructed at an elbow fitting by a solid material that covered the inlet. During the examination, another particle fell out of the elbow. The shape of the particle conformed to the shape of the unobstructed portion of the elbow inlet and the edge of the obstruction.