The center fuselage section is found between FS403.22 and FS621.78. The center fuselage section includes the wheel bin and the passenger compartment section which has the over-wing emergency exit.

The center fuselage section is assembled from external sheet metal skins and is made stronger with longerons, stringers, machined and formed frames. The full circumference of the fuselage is pressurized other than the wing-to-fuselage connection (pressure floor area) and the wheel wells.

The center fuselage floor is found in the cabin between FS406.00 and FS629.64. The floor support structure is made from lateral and longitudinal beams which are connected to each other. The lateral beams attach to the fuselage frames at WL80.00 and to aluminum-alloy floor posts, at LBL13.23 and RBL13.23. The longitudinal floor beams are installed at LBL13.50, LBL26.25, RBL13.50 and RBL26.25. These floor beams also hold the seat tracks.

The pressure floor structure is between FS486.00 and FS629.64. There are no floor posts in the pressure floor section. The pressure floor is made stronger with floor supports from FS486.00 to FS635.65 at LBL4.50, LBL20.00, RBL4.50, and RBL20.00.

There are two Main Landing Gear (MLG) wheel bins (left and right) installed in the MLG bay below the center fuselage pressure floor. The MLG wheel bins are for storage of the MLG wheels while the aircraft is airborne. They also prevent damage to other equipment that is installed in the MLG bay if there is a tire burst.

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

The center fuselage has thirteen frames and two wing spar frames installed between FS403.22 and FS621.78 above the floor level. These frames are made of sheet metal sections. The top and side frame sections connect at STGR 6L and 6R. They also connect with the frame sections of the lower skin panel at STGR16L and STGR16R between FS403.22 and FS486.00. The frames between FS486.00 and FS621.78 connect with the pressure floor structure at STGR16L and STGR16R.

The wing front-spar frame is found at FS501.00 and is made in three parts. It is made from machined aluminum alloy and the three parts are attached together with joints. The wing front-spar frame has lugs which attach the wing to the fuselage.

The wing rear-spar frame is found at FS587.03 and is made in three parts. It is made from machined aluminum alloy and the three parts are attached together with joints. The wing rear-spar frame has lugs which attach the wing to the fuselage. The pressure floor extends from the forward pressure bulkhead at FS486.00 to the aft pressure bulkhead at FS635.65. It is made from a sheet metal pressure skin made stronger with eight floor beams, extended in a longitudinal direction. The floor beams are made from an I-section extrusion.

The forward pressure bulkhead at FS486.00 is the aft end of the forward floor structure below WL80.00. This bulkhead also seals the forward end of the center fuselage pressure floor below WL80.00. The forward pressure bulkhead is made from seven machined sections. It also includes a machined avionics adapter and four plates, attached with rivets, which hold connectors from many aircraft systems.

The aft pressure bulkhead at FS635.65 seals the aft end of the center fuselage pressure floor below WL80.00. This bulkhead is also the forward end of the aft equipment compartment. The top area of the bulkhead is made from machined sections. The bottom area of this bulkhead is made from a sheet metal web which is made stronger with stringers. The bottom area also includes four plates, attached with rivets, which hold connectors from many aircraft systems.

The floor support structure between FS403.22 and FS486.00 has five lateral beams and four longitudinal beams. The lateral beams are attached to the fuselage frames at STGR16L and 16R and to floor posts. The floor posts are made from extruded aluminum alloy. The lateral beams are made from formed aluminum-alloy sheet. The longitudinal beams are made from extruded aluminum-alloy. The longitudinal beams are also used to hold the seat rails.

There is an over-wing emergency exit installed on the right side of the fuselage. The surround structure is made stronger with machined frames and lintels. The exit is a plug type door which is resistant only to pressure in the passenger compartment.

There are twelve passenger compartment windows in the center fuselage section, six on the left side and six on the right side. On the right side, one window is in the over-wing emergency exit. The forward keel beam is made from two machined sections, and it extends from FS454.00 to FS501.02. The forward keel beam is connected to the bottom of the fuselage structure and gives support to the wings. It is connected to the wings at its aft end.

The aft keel beam is made from two machined sections and two plates made from aluminum sheets. The aft keel beam's forward end is at FS586.67 and it extends to the aft fuselage at FS688.45. The aft keel beam gives support to the wings, and is connected to the wings at its forward end.

Structures for the support of the over-wing fairings and forward wing-to-fuselage fairings are installed on the bottom of the center fuselage structure. The fairings are attached to the support structure with fasteners. Landing lights are installed on the support structure of the forward wing-to-fuselage fairings.

There are two main landing gear (MLG) wheel bins (left and right), and each one is made from an upper composite assembly and a lower composite assembly.

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The center fuselage floor includes:

Center Fuselage Floor-Panels

The center fuselage floor-panels are made from a graphite prepreg on a Nomex honeycomb sheet. There is a ply of glass fiber prepreg on the lower side for corrosion protection. The floor panels attach to the floor structure with screws and can be removed.

The floor panels for the center fuselage include the area from FS406.00 to FS629.64. The aft fuselage floor-panels extend to the remaining center fuselage floor-area from FS629.64 to FS635.65. The center fuselage floor-panels extend to the forward fuselage floor-area from FS392.00 to FS406.00. The floor panel area from FS406.00 to FS629.64 has three sections. The first section includes the area from FS406.00 to FS486.00. It has 5 floor panels which extend on the full length of that section. There is one center panel, two middle panels and two small panels. The middle panels are on the left and right outboard side of the center panel. The small panels are on the left and right outboard side of the middle panels.

The second section includes the area from FS486.00 to FS596.81. It has 5 floor panels which extend on the full length of that section. There is one center panel, two middle panels and two small panels. The middle panels are on the left and right outboard side of the center panel. The small panels are on the left and right outboard side of the middle panels.

The remaining section includes the area from FS596.81 to FS629.64. It has 3 floor panels which extend on the full length of that section. There is one center panel and two middle panels. The middle panels are on the left and right outboard side of the center panel. The left and right middle panels have cut parts. This is to keep a free area in the floor, on the outboard sides, for the installation of ducts, the lavatory and the sink drains.

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The wheel-bin assemblies are made from an upper composite assembly and a lower composite assembly.

The upper composite assembly is attached to the fuselage structure. The Main Landing Gear (MLG) Sensing Element is installed in the upper composite assembly. The sensing element wire goes through the upper composite assembly to a quick-disconnect electrical connector, installed inboard, in the MLG bay.

The lower composite assembly is attached to the upper composite assembly and to the fuselage structure with quick release fasteners. A brush assembly is attached to the opening of the lower composite assembly. When connected with the brush assembly on the door attached to the Main Gear Door, this makes an aerodynamic seal when the MLG is stowed. A flexible brush is used to make sure the main gear move freely. There is no requirement for the brush to touch the tires with the main gear retracted.

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Component Location Index
IDENT	DESCRIPTION	LOCATION	IPC REF
-	CENTER FUSELAGE FLOOR-PANEL	PANEL(S) 231ALF	53-31-01
-	CENTER FUSELAGE FLOOR-PANEL	PANEL(S) 231BLF	53-31-01
-	CENTER FUSELAGE FLOOR-PANEL	PANEL(S) 231CLF	53-31-01
-	CENTER FUSELAGE FLOOR-PANEL	PANEL(S) 231DLF	53-31-01
-	CENTER FUSELAGE FLOOR-PANEL	PANEL(S) 231ELF	53-31-01
-	CENTER FUSELAGE FLOOR-PANEL	PANEL(S) 231FLF	53-31-01
-	CENTER FUSELAGE FLOOR-PANEL	PANEL(S) 231GLF	53-31-01
-	CENTER FUSELAGE FLOOR-PANEL	PANEL(S) 231HLF	53-31-01
-	CENTER FUSELAGE FLOOR-PANEL	PANEL(S) 232ARF	53-31-01
-	CENTER FUSELAGE FLOOR-PANEL	PANEL(S) 232BRF	53-31-01
-	CENTER FUSELAGE FLOOR-PANEL	PANEL(S) 232CRF	53-31-01
-	CENTER FUSELAGE FLOOR-PANEL	PANEL(S) 232DRF	53-31-01
-	CENTER FUSELAGE FLOOR-PANEL	PANEL(S) 232ERF	53-31-01
-	LOWER WHEEL BIN (LH)	ZONE(S) 171BZ	53-32-01
-	LOWER WHEEL BIN (RH)	ZONE(S) 172BZ	53-32-01
-	TOP WHEEL BIN (LH)	ZONE(S) 171AZ	53-32-01
-	TOP WHEEL BIN (RH)	ZONE(S) 172AZ	53-32-01

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