LAX83FU001

The ultralight was on a demonstration flt. Reportedly, the plt made a pass down the rwy, then had turned downwind at 400 to 500 ft, when witnesses heard a loud bang or crack & saw the wings of the vehicle fold. The ultralight then entered a spiral & crashed in a canal. An exam revealed that the wing had folded downward. Compression buckling had occurred at the wing center section. Also, the mylar skin was found separated from the top & bottom of the wing center section at the bonded attach areas. According to the manufacturer, loss of the mylar skin on the top of the wing would result in an aft shift in the center of pressure & cause the vehicle to pitch forward. Witnesses thought that the wings had folded upward, but the investigation verified that they failed in a negative mode. After this occurrence, the mylar material on the mitchell A-10 vehicles was replaced with ceconite covering & was riveted in place with aluminum battens. Although the prototype had balance wts, they had been removed from production models to eliminate wt.