The center fuselage is found between FS574.50 and FS781.00. The center fuselage section includes the wheel well and center cabin section which has the over-wing emergency exit. The center fuselage is assembled from external sheet metal skins, stiffened with longerons, stringers and machined and formed frames.

The skins are made from machined aluminum alloy. They attach to the frames and the stringers which add stiffness to the structure. The stringers are T-shaped and square-capped to add stiffness and they attach to the frames. The frames have the cutouts to get access to the stringers.

The front spar frame is made in three parts. It is made from machined aluminum alloy and attached together with the splices. The front spar frame attaches with the front bulkhead of the center wing box.

The rear spar frame is made in three parts. It is made from machined aluminum alloy and attached together with the splices. The rear spar frame attaches with the rear bulkhead of the center wing box.

The pressure bulkhead at FS781.00 seals the aft end of the passenger compartment above WL71.50. This bulkhead is also the aft end of the main landing gear bay below WL71.50. The bulkhead is made of frames and webs. The top area of the frame is assembled from machined section and built with sheet metal angles. The left and right side sections are machined and are connected with the end splices. The frame sections have the cutouts to permit access to the
stringers. The webs are made stronger with stiffeners which are attached to the adjacent skins, the stringers, and the floor structure.

There are nine frames installed between FS574.50 and FS781.00. These frames are made of machined sections and built-up sheet metal sections (top, left and right sections). The top and two sides sheet metal frame sections are connected with the end splices at the stringer 5, and they are connected with the machined frame segments at the part of the stringer 14. The frames have the cutouts to permit access to the stringers. These frames do not include the edges and the center frames at the emergency exit cutout.

There is a Type III over-wing emergency exit door installed on the right side of the fuselage, between FS620.50 and FS643.70. The provisions are made to install a second over-wing emergency exit door at the same location on the left side of the aircraft. This door is a plug type door which is resistant only to the pressure in the passenger compartment.

There are twelve windows in the center fuselage section, between FS574.50 and FS781.00, six on the left side and six on the right side. On the right side, one window is in the emergency door.

The windows are resistant to the aircraft pressure load only, and they keep the shear strength function to a limit.

The longeron is installed at each side of the fuselage at the intersection of the pressure floor with the fuselage. The longeron is a Z-shape machined member. The side beam has a cabin blowout cutout for the pressure decompression protection.

The keel beam has four extruded sections and four skin plates assembled in a box-shape structure. The keel beam has five machined inner ribs to add stiffness to the box section. The keel beam extends to the full length of the MLG bay and attaches the wing box at FS719.30 and the bulkhead at FS781.00 with the machined fittings. The joint at FS781.00 is the interface with the aft fuselage.

The center fuselage pressure floor extends from FS719.30 to FS781.00 and attaches the longeron at the left and right sides of the fuselage at WL67.00. The pressure floor is made stronger with the floor beams extended in a longitudinal direction. The floor beams are made from an H-section extrusion. The floor beams at BL9.00 and BL27.00 make splices at FS788.88 where they interface with the aft fuselage.

The floor panels are made of a composite honeycomb structure. The floor panels give access to the structure and to the equipment installed below WL71.50.

The structure of the support of the over-wing and belly fairing is made from ribs, channels and angles. The fairing is attached to the structure with fasteners. The belly fairing support structure also supplies attachment for the fittings of the inner door stop of the landing gear.

The main landing-gear wheel bin is a four-piece assembly which has three panels to shape the bottom and a one piece cap. The panels and the cap are attached to the structure with the quick-release fasteners. The wheel bin is made of the multi-layered composite kevlar that uses epoxy resin cured at 250°F. The wheel bin is made of a composite of kevlar resistant to a tire burst and prevents the damage to the equipment that is installed in the main landing-gear
bay. The wheel bin is held on the sheet metal brackets with quick-release fasteners for easy removal.