Page:Civil Aeronautics Board accident investigation report, National Airlines Flight 2511.pdf/11

 The winds aloft existing at the time of the accident, which were in excess of 100 knots from the west-southwest at 18,000 feet and in excess of 85 knots between 18,000 and 12,000 feet, clearly explain why many small light pieces of the aircraft cabin wall were not found. These parts drifted east-northeast from the point of the initial explosion and fell into the ocean. This is also verified by the subsequent finding of a number of these missing parts which had washed up along the beach.

A lengthy and detailed study of the wreckage was conducted to determine the cause of the initial aircraft structural failure. The possibilities of several different failures was considered. These included: A fatigue failure of the cabin structure followed by explosive decompression; a propeller blade failure followed by cabin penetration and explosive decompression; the malfunction of the cabin pressurization system causing a structural failure; foreign object penetration; a lightning strike; fuel vapor explosion; oxygen bottle explosion; and the possibility of the detonation of an explosive substance within the aircraft.

The nature of the initial damage, the intensity of the force involved, and the location from which the force emanated, together with the check of the aircraft structure and its systems, eliminate the possibility of a fuel vapor explosion.

The study and analysis of the wreckage revealed information which in effect eliminated all of these possibilities except for the possibility of the detonation of an explosive substance within the aircraft.

The extreme force of the agent causing the initial cabin failure strongly indicates that a highly explosive substance was involved. The deformation of the structure surrounding the focal point of the damage was similar to that resulting from the detonation of a high explosive. The fragmentation of the cabin structure adjacent to the focal point of the structural failure also indicates that a high explosive was the causal agent.

The sodium carbonate, sodium nitrate, and complex mixtures of sodium-sulfur compounds found in the air vent of the passenger cabin are typical of the residues found after the detonation of dynamite. The presence of nitrate traces on a lifejacket in the Kure Beach area also substantiates the fact that an explosive substance was set off in the passenger cabin. Manganese dioxide is commonly found only in the black mix portion of a dry cell battery. This substance, found on one of the cabin windows, and on the triple passenger seat indicates the presence of a dry cell battery within the immediate explosive force area. The blast damage pattern seen in the cabin structure and to the passenger seats shows that the focal point of the explosion was beneath the triple seat next to the right cabin window of seat row No. 7

The nitrate traces found on the lifejacket and the presence in the air vent of the residues usually found after the explosion of dynamite in addition to the other facts set forth conclusively show that a dynamite explosion was set off in the passenger cabin.

It is the Board's conclusion that Flight 2511 proceeded in a normal manner