The cargo flight departed Newark at 17:33 for a flight to Chicago, Denver, Burbank and San Francisco. At 19:31 the flight reported over Cleveland, Ohio, at the cruising altitude of 4,000 feet, stating that there was extreme turbulence approximately five miles east of the Cleveland Airport. At 20:13 the flight reported over Mansfield, Ohio. The crew stated that they had changed course to the south to avoid thunderstorms, and intended to proceed to Columbus, Ohio, in accordance with visual flight rules. After having been cleared to land at Columbus, the flight crew stated, “We are declaring an emergency. Our rudder is locked, and I don’t think we will have any directional control on the ground.” After touchdown on runway 23 power was immediately applied and the aircraft took off. The crew then informed the tower that they wished to land directly into the wind, and were accordingly cleared to land on runway 18. After touchdown power was again applied and the flight took off again. When the flight reached a point 2 1/2 miles east of the field in its left circle of the field, it was observed to spin to the ground. PROBABLE CAUSE: “The Board determines that the probable cause of this accident was the in-flight failure of the fuselage carry-in structure beneath the fin, due to extreme turbulence.”