About 30 minutes after takeoff the aircraft was observed by witnesses to be heading in an easterly direction at about 500 feet above ground level. It was then seen to turn left, head north and commence a gradual descent. The witnesses then reported that another left turn was commenced and both wings folded back. The aircraft entered a steep descent before impacting with the ground. An inspection of the aircraft revealed that the left wing front drag cable had failed, due to fatigue and overload, at the forward end near to the attachment point. The failure of this cable resulted in the wings folding. The manufacturer of the aircraft had published a technical bulletin some seven months prior to the accident recommending that owners replace all the wires on their aircraft and fit a double drag brace system. The owner pilot of this aircraft was aware of the recommendation but had not made the nesessary modifications.