Accident Summary
During a demonstration flight, an ultralight vehicle made a pass down the runway and turned downwind at an altitude between 400 and 500 feet. Witnesses reported hearing a loud bang or crack and observed the wings of the vehicle fold. The ultralight subsequently entered a spiral descent and crashed into a canal.
Investigation Findings
Examination of the wreckage revealed that the wing had folded downward. Compression buckling was present at the wing center section. Additionally, the Mylar skin was found separated from the top and bottom of the wing center section at the bonded attachment areas. Although witnesses believed the wings had folded upward, the investigation confirmed that the failure occurred in a negative mode (downward direction).
Manufacturer Statement
According to the manufacturer, loss of the Mylar skin on the top of the wing would result in an aft shift of the center of pressure, causing the vehicle to pitch forward.
Aftermath
Following this occurrence, the Mylar material on Mitchell A-10 vehicles was replaced with Ceconite covering, which was riveted in place with aluminum battens. Additionally, although the prototype had balance weights, they had been removed from production models to eliminate weight.