Page:Civil Aeronautics Board accident investigation report, National Airlines Flight 2511.pdf/4

 to the missing area were irregular and extensively deformed. Five adjacent pieces of flooring from this area were recovered from the main wreckage area. All of the floor carpeting between the seat tracks was recovered except for a portion corresponding to the missing flooring on the right side forward of the front spar.

The carpeting immediately forward and aft of the missing area was cut and torn in numerous places and upon x-ray examination was found to contain numerous foreign objects which included pieces of .025 inch wire, rivets, and rubber-backed nylon material similar to that used in the manufacture of an airline type flight bag. Manganese dioxide deposits were also found on this carpeting.

Eight heavy electrical cables are contained in three conduits which connect the right wing junction box in the hydraulic compartment to the main junction box in the cockpit and which run through the area of the missing portion of the fuselage and adjacent to the missing portion of the floor. These cables were severely damaged and had numerous separations and cuts, and the conduits were found to be separated in numerous places.

All of the interior furnishings of the lavatory area of the fuselage were examined for foreign deposits or debris or for evidence of any unusual conditions. Particular emphasis was placed on the area just forward of the wing since this appeared to be the focal point of the fuselage disintegration. Numerous tiny pieces of wire approximately .025 inch in diameter and necked down at each end were found scattered throughout this area. Deposits of sodium carbonate, sodium nitrate, and complex mixtures of sodium-sulfur compounds were found in the air vent in the hatrack section from the right side of the cabin in the area of the focal force of the initial disintegration.

One of the triple seats which was installed in the right side of the passenger cabin, and which was recovered at the main crash site exhibited damage which was somewhat different than that found on most of the other seats. This seat was severely damaged and had numerous bends, failures, and buckling of its structure. Also evident were areas of both heavy and light pitting of the structure and there were numerous small indentations and some large ones. One of the seat belts was missing and portions of the upholstery material were missing with the material adjacent to the missing portions showing a shredded appearance. Some of the seat webbing material was torn and cut; however, most was missing. The bottom of this seat assembly was splattered with a black substance which was identified as manganese dioxide.

Many articles and portions of the fuselage or interior furnishings from this area were collected and submitted for laboratory examination for evidence of explosive residue or foreign object damage, and numerous particles of wood, wire, metal particles, and other objects found to have penetrated various of the interior furnishings in the cabin in the area surrounding the initial airframe failure were subjected to laboratory examination.

Extensive damage was initially observed in the wing center section and fuselage hydraulic compartment area, however, the reconstruction of this area showed no failure or malfunction which could be considered as a causal factor of this accident.

Two pieces of the hydraulic compartment center wing structure were recovered