The Curtiss C-46 was loaded to about 20 pounds under the maximum allowable gross weight of 48000 pounds for the cargo flight to Wilmington. Weather was 2300 feet overcast, visibility 10 miles in light snow, temperature 26deg F. and wind 250deg at 4 knots. About 2-3 inches of snow were swept from the wings and the underlying layer of rough crusted ice was de-iced using an 8 to 1 mixture of ethyline glycol. At 06:08 the plane took off from runway 21L and climbed to 200 feet following a longer than usual takeoff run. When power was reduced, the plane started vibrating and altitude was lost. The aircraft contacted the ground again 2050 feet past the end of the runway and slid for 448 feet before coming to rest in an upright position. It appeared that a layer of about 3 mm ice was still on the wings. PROBABLE CAUSE: “A loss of lift during takeoff, resulting from airframe icing caused by inadequate de-icing and pre-flight inspection.”