Shortly after takeoff the aircraft was seen to turn to the left. The bank to the left increased progressively and shortly after, the aircraft turned on its back and crashed. PROBABLE CAUSE: “It was decided that the unusual path of the aircraft immediately following the take-off, was due to the blocking of the ailerons to the left at an angle of approximately 10deg. It was determined on the basis of analysis that the probable cause of the blocking was the unclamping of a link cheek of the upper rear chain of the co-pilot’s control column, as a result of which the chain slipped off the sprocket and jammed against the internal boss of the pin which locks the ailerons in the neutral position. More broadly, the investigation brought to light the difficulty of setting and inspecting the chains inside the dual control columns. This difficulty is directly attributable to the design, and may cause certain chains which have not been properly studied in relation to the type of service for which they are intended, to become unclamped by torsion during maintenance and setting work.”