The center wing box structure is made of a primary frame with skin panels on the top and bottom. The center wing box structure is sealed between the front and rear bulkheads and the root rib at BL47.610. This compartment is sealed for the integral fuel tank of the center wing box.

The top and bottom skin panels are made from aluminum alloy plate. These skin panels have two access panels for the servicing of the fuel and hydraulic systems. These access panels are made from laminated graphite.

The front bulkhead is a one-piece assembly. The front bulkhead has top and bottom angle spar caps attached to a web to make the vertical and horizontal members stronger. An angle and a plate separate the front bulkhead from the outer wings at BL47.61.

The rear bulkhead is made from aluminum alloy and made stronger with stiffeners and caps. The rear bulkhead is a support for the attachment fittings for the main landing gear (MLG) side brace. A tension fitting, an angle, and a plate separate the rear bulkhead from the outer wings at BL47.61.

The keel beam assembly transmits the forward and aft wing loads to the fuselage structure. This assembly is installed at the center line of the center wing box. It is attached to the front bulkhead at FS574.50, the rear bulkhead at FS719.30, and the fuselage frame at FS781.00. The assembly has four angle beams and webs made stronger with stiffeners. They give the contour to the center wing-box skin panel with the structure. They are attached to the top panel with the shear ties and the top chord, and to the bottom panel with the shear ties.

The intermediate ribs are the truss structure and have top and bottom chords. They are attached to the skin panels with the shear ties. They give the contour to the center wing-box skin panels. They are attached to the front bulkhead and the rear bulkhead with the shear panels.

The root ribs are made from the top and bottom chord, forward of the vertical beam. They give the contour to the center wing-box skin panel and are baffles in the wing fuel tank. The root ribs are installed at BL47.610 and they are attached to the outer wing at the top and bottom with fittings.

The skin panels have three areas along the span for the top and bottom surfaces. The top skin panels are made from aluminum alloy plate and are made stronger with integrated stringers. The bottom skin panels are made from aluminum alloy plate. The stringers are attached on the bottom skin panels. These skin panels have two access panels for the servicing of the fuel and hydraulic systems.These access panels are made from laminated graphite.

The MLG side stay attachment fittings are made from aluminum alloy. They are installed on the rear bulkhead of the center wing box.