DOC AIRBUS | AMM A320FMAIN STRUCTURE - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
1. General
The center fuselage main-structure includes:
** ON A/C NOT FOR ALL The center fuselage main-structure includes:
- the wing center box which makes the wing-to-fuselage joint and is installed in the lower center-fuselage shell,
- the belly fairing structure installed on the lower exterior of the fuselage shell,
- skin panels which make the outer skin of the fuselage shell,
- frames which are the stiffeners around the fuselage shell,
- stringers and skin stiffeners to make the skin stronger,
- floor and pressure-limit structures. The floor structure makes the passenger compartment floor above the wing center box and the main-landing gear bay pressure limit-zone. The pressure limit structure makes a diaphragm between the upper (pressurized) and lower (unpressurized) areas of the center fuselage,
- seat tracks for the installation of the passenger compartment seats.
2. Description
A. Wing Center Box
The primary components of the wing center box include:
The primary components of the wing center box include:
Wing Center Box - Component Location- two root ribs, one left and one right. The root ribs give external attach points and internal structural strength to FR37 thru FR41,
- two spars, one front and one rear. Two primary fuselage frames interface with the spars to make the wing-to-fuselage joint. FR36 is connected to the front spar and FR42 is connected to the rear spar. (The front spar is also a pressure bulkhead in the pressure limit zone).
- two skin panels, one top and one bottom. The top skin panel is part of the pressure limit-zone structure. The bottom skin panel is closed by the belly fairing structure.
The box is made stronger by internal truss ribs. The truss ribs are installed along the length of the inner structure and extend between the front and rear spars. The complete wing center box-assembly reacts to wing bending moment. It transmits external wing shear and torsion into the fuselage. Some is transmitted through the root ribs, but most transmits through the two spars and primary frames, FR36 and FR42. Two triangular holes in the rear spar give hand access into the wing center box-structure. You can get access to the holes forward of the main landing-gear bay. Light-alloy panels close the holes. An integral fuel tank (option) can be installed in the wing center box-structure.
B. Belly Fairing
The belly fairing is installed on the exterior of the lower center fuselage. The structure is an extension to the fuselage and gives easy access to the air conditioning and hydraulic services equipment Ref. Task 53-35-00.
The belly fairing is installed on the exterior of the lower center fuselage. The structure is an extension to the fuselage and gives easy access to the air conditioning and hydraulic services equipment Ref. Task 53-35-00.
C. Center Fuselage
The center fuselage is constructed of:
The center fuselage is constructed of:
- frames which give the shape and rigidity to the semi-monocoque structure,
- skin panels preformed to the contour of the fuselage and riveted to the frames to make the fuselage shell,
- stringers and skin stiffeners to make the fuselage skin stronger,
- floor structures to hold the passenger compartment floor above the pressure limit zone.
(1) Frames
Frames are the circular stiffeners around the fuselage shell. All but the two primary wing box frames are made of aluminum-alloy sections. The top part of each frame is formed from sheet and the lower part is machined from plate. The two wing box frames, FR36 and FR42, are machined from forgings. Clips, with cutouts for stringers, are riveted between the frames and the skin panels. The center fuselage is constructed of the following frames:
Frames are the circular stiffeners around the fuselage shell. All but the two primary wing box frames are made of aluminum-alloy sections. The top part of each frame is formed from sheet and the lower part is machined from plate. The two wing box frames, FR36 and FR42, are machined from forgings. Clips, with cutouts for stringers, are riveted between the frames and the skin panels. The center fuselage is constructed of the following frames:
- FR35. A full ring frame which makes the joint between the forward and center fuselage. The forward pressure limit bulkhead is installed in the lower part of this frame. The keel beam also connects to the bottom of the frame,
- FR36. This is the forward primary frame of the wing-to-fuselage joint and is part of the wing box assembly. The frame is made of two forged sections which are machined and installed back-to-back. The longer of the two sections extends to STGR1; the shorter section extends to STGR18. The frame is connected to the wing-box front spar,
- FR37 thru FR41. Five frames which are connected to the left and right external attach points of the wing box root-ribs. FR38 and FR39, FR40 and FR41 are installed at irregular distances to the other center section frames. These frames give the structural strength to the two emergency exit openings found above the wing on each side,
- FR42. This is the rear primary frame of the wing-to-fuselage joint and is part of the wing box assembly. The frame, almost the same as FR36, is two forged sections which are machined and installed back-to-back. The longer of the two sections extends to STGR1; the shorter section extends to STGR11. The frame is connected to the wing box rear spar,
- FR43 thru FR45. These frames go around the shell and connect with the side box assemblies (left and right) and extend into the main landing-gear bay. Two slanting frames connect with the frame ends on each side to shape and strengthen the landing-gear wheel openings,
- FR46. The rear pressure-limit bulkhead is installed in the lower part of this frame. The bulkhead completes the pressure limit zone of the center fuselage and makes the rear wall of the main landing-gear bay. The bulkhead slopes to the rear at the bottom to give the necessary wheel retraction area in the main landing-gear bay. The keel beam connects to the bottom of the frame,
- FR47. A full ring frame which makes the joint between the center and rear fuselage sections.
(2) Frames
Frames are the circular stiffeners around the fuselage shell. All but the two primary wing box frames are made of aluminum-alloy sections. The top part of each frame is formed from sheet and the lower part is machined from plate. The two wing box frames, FR36 and FR42, are machined from forgings. Clips, with cutouts for stringers, are riveted between the frames and the skin panels. The center fuselage is constructed of the following frames:
Frames are the circular stiffeners around the fuselage shell. All but the two primary wing box frames are made of aluminum-alloy sections. The top part of each frame is formed from sheet and the lower part is machined from plate. The two wing box frames, FR36 and FR42, are machined from forgings. Clips, with cutouts for stringers, are riveted between the frames and the skin panels. The center fuselage is constructed of the following frames:
- FR35.8. A full ring frame which makes the joint between the forward and center fuselage. The forward pressure limit bulkhead is installed in the lower part of this frame. The keel beam also connects to the bottom of the frame,
- FR36. This is the forward primary frame of the wing-to-fuselage joint and is part of the wing box assembly. The frame is made of two forged sections which are machined and installed back-to-back. The longer of the two sections extends to STGR1; the shorter section extends to STGR18. The frame is connected to the wing-box front spar,
- FR37 thru FR41. Five frames which are connected to the left and right external attach points of the wing box root-ribs. These frames add to the structural strength of the center fuselage above the wing on each side,
- FR42. This is the rear primary frame of the wing-to-fuselage joint and is part of the wing box assembly. The frame, almost the same as FR36, is two forged sections which are machined and installed back-to-back. The longer of the two sections extends to STGR1; the shorter section extends to STGR11. The frame is connected to the wing box rear spar,
- FR43 thru FR45. These frames go around the shell and connect with the side box assemblies (left and right) and extend into the main landing-gear bay. Two slanting frames connect with the frame ends on each side to shape and strengthen the landing-gear wheel openings,
- FR46. The rear pressure-limit bulkhead is installed in the lower part of this frame. The bulkhead completes the pressure limit zone of the center fuselage and makes the rear wall of the main landing-gear bay. The bulkhead slopes to the rear at the bottom to give the necessary wheel retraction area in the main landing-gear bay. The keel beam connects to the bottom of the frame,
- FR47. A full ring frame which makes the joint between the center and rear fuselage sections.
(3) Frames
Frames are the circular stiffeners around the fuselage shell. All but the two primary wing box frames are made of aluminum-alloy sections. The top part of each frame is formed from sheet and the lower part is machined from plate. The two wing box frames, FR36 and FR42, are machined from forgings. Clips, with cutouts for stringers, are riveted between the frames and the skin panels. The center fuselage is constructed of the following frames:
Frames are the circular stiffeners around the fuselage shell. All but the two primary wing box frames are made of aluminum-alloy sections. The top part of each frame is formed from sheet and the lower part is machined from plate. The two wing box frames, FR36 and FR42, are machined from forgings. Clips, with cutouts for stringers, are riveted between the frames and the skin panels. The center fuselage is constructed of the following frames:
- FR35. A full ring frame which makes the joint between the forward and center fuselage. The forward pressure limit bulkhead is installed in the lower part of this frame. The keel beam also connects to the bottom of the frame,
- FR36. This is the forward primary frame of the wing-to-fuselage joint and is part of the wing box assembly. The frame is made of two forged sections which are machined and installed back-to-back. The longer of the two sections extends to STGR1; the shorter section extends to STGR18. The frame is connected to the wing-box front spar,
- FR37 thru FR41. Five frames which are connected to the left and right external attach points of the wing box root-ribs. These frames add to the structural strength of the center fuselage and emergency exit opening installed above the wing on each side,
- FR42. This is the rear primary frame of the wing-to-fuselage joint and is part of the wing box assembly. The frame, almost the same as FR36, is two forged sections which are machined and installed back-to-back. The longer of the two sections extends to STGR1; the shorter section extends to STGR11. The frame is connected to the wing box rear spar,
- FR43 thru FR45. These frames go around the shell and connect with the side box assemblies (left and right) and extend into the main landing-gear bay. Two slanting frames connect with the frame ends on each side to shape and strengthen the landing-gear wheel openings,
- FR46. The rear pressure-limit bulkhead is installed in the lower part of this frame. The bulkhead completes the pressure limit zone of the center fuselage and makes the rear wall of the main landing-gear bay. The bulkhead slopes to the rear at the bottom to give the necessary wheel retraction area in the main landing-gear bay. The keel beam connects to the bottom of the frame,
- FR47/51. A full ring frame which makes the joint between the center and rear fuselage sections.
(4) Skin Panels
Five primary skin panels and four lower side panels make the center fuselage skin. The five primary panels extend the length of the center fuselage and include:
Five primary skin panels and four lower side panels make the center fuselage skin. The five primary panels extend the length of the center fuselage and include:
- one top panel which extends across the width of the shell from STGR6 left to STGR6 right. The panel edges overlap the side panel edges and the panels are then riveted together,
- two side panels, a top and middle on each side. The top side panel extends from STGR6 to STGR18 and includes eight passenger cabin windows and two emergency exit openings. The middle side panel includes the bottom part of both emergency exit openings. The panel extends from STGR18 and attaches to the wing root cruciform-fitting and forward and rear lower side panels. The top side panel lower edges overlap the middle side-panel edges and are then riveted together at STGR18. Both side panel edges have a recess so that their outer faces are in line with each other when riveted together.
The top panel and the top and middle side panels are chemically milled. Stringers are riveted to them on the inner surface to make them stronger. Two lower side panels, a forward and a rear panel on each side, complete the center fuselage skin. They include: - a forward lower side panel, left and right, installed in front of the wing center box between FR35 and FR36. Each panel, complete with stringers on the outer face, is chemically milled. The panel contains openings for systems interface between the fuselage and the wing leading edge. You can get access to both forward lower side panels from behind the belly fairing structure,
- a rear lower side-panel, left and right. The panels surround the wheel openings of the main landing-gear bay aft of the wing centerbox structure. They are installed between FR42 and FR47 and span between the middle side panel and keel beam structure. Two slanting frames (connected together at one end to make an inverted V-shape) support and strengthen each panel at the edges of the wheel opening. The panels are chemically milled and stringers are riveted on their outer face. You can get access to both rear lower side panels from behind the belly fairing structure.
(5) Stringers and Skin Stiffeners
(a) The stringers are the longitudinal stiffeners of the fuselage shell. They are made of aluminum-alloy Z-section which are formed or machined. They are riveted between the frames and the skin panels.
(b) The skin stiffeners make the skin stronger. They are riveted to the skin in areas of high stress (fuselage section and skin panel joints, cabin windows, emergency exits and door openings). Skin stiffeners are chemically milled or machined from forgings.
(6) Skin Panels
Five primary skin panels and four lower side panels make the center fuselage skin. The five primary panels extend the length of the center fuselage and include:
Five primary skin panels and four lower side panels make the center fuselage skin. The five primary panels extend the length of the center fuselage and include:
- one top panel which extends across the width of the shell from STGR6 left to STGR6 right. The panel edges overlap the side panel edges and the panels are then riveted together,
- two side panels, a top and middle on each side. The top side panel extends from STGR6 to STGR18 and includes ten passenger cabin windows. The middle side panel extends from STGR18 and attaches to the wing root cruciform-fitting and forward and rear lower side panels. The top side panel lower edges overlap the middle side-panel edges and are then riveted together at STGR18. Both side panel edges have a recess so that their outer faces are in line with each other when riveted together.
The top panel and the top and middle side panels are chemically milled. Stringers are riveted to them on the inner surface to make them stronger. Two lower side panels, a forward and a rear panel on each side, complete the center fuselage skin. They include: - a forward lower side panel, left and right, installed in front of the wing center box between FR35.8 and FR36. Each panel, complete with stringers on the outer face, is chemically milled. The panel contains openings for systems interface between the fuselage and the wing leading edge. You can get access to both forward lower side panels from behind the belly fairing structure,
- a rear lower side-panel, left and right. The panels surround the wheel openings of the main landing-gear bay aft of the wing centerbox structure. They are installed between FR42 and FR47 and span between the middle side panel and keel beam structure. Two slanting frames (connected together at one end to make an inverted V-shape) support and strengthen each panel at the edges of the wheel opening. The panels are chemically milled and stringers are riveted on their outer face. You can get access to both rear lower side panels from behind the belly fairing structure.
(7) Stringers and Skin Stiffeners
(a) The stringers are the longitudinal stiffeners of the fuselage shell. They are made of aluminum-alloy Z-section which are formed or machined. They are riveted between the frames and the skin panels.
(b) The skin stiffeners make the skin stronger. They are riveted to the skin in areas of high stress (fuselage section and skin panel joints, cabin windows, emergency exits and door openings). Skin stiffeners are chemically milled or machined from forgings.
(8) Skin Panels
Five primary skin panels and four lower side panels make the center fuselage skin. The five primary panels extend the length of the center fuselage and include:
Five primary skin panels and four lower side panels make the center fuselage skin. The five primary panels extend the length of the center fuselage and include:
- one top panel which extends across the width of the shell from STGR6 left to STGR6 right. The panel edges overlap the side panel edges and the panels are then riveted together,
- two side panels, a top and middle on each side. The top side panel extends from STGR6 to STGR18 and includes nine passenger cabin windows and the emergency exit opening. The middle side panel includes the bottom part of the emergency exit opening. The panel extends from STGR18 and attaches to the wing root cruciform-fitting and forward and rear lower side panels. The top side panel lower edges overlap the middle side-panel edges and are then riveted together at STGR18. Both side panel edges have a recess so that their outer faces are in line with each other when riveted together.
The top panel and the top and middle side panels are chemically milled. Stringers are riveted to them on the inner surface to make them stronger. Two lower side panels, a forward and a rear panel on each side, complete the center fuselage skin. They include: - a forward lower side panel, left and right, installed in front of the wing center box between FR35 and FR36. Each panel, complete with stringers on the outer face, is chemically milled. The panel contains openings for systems interface between the fuselage and the wing leading edge. You can get access to both forward lower side panels from behind the belly fairing structure,
- a rear lower side-panel, left and right. The panels surround the wheel openings of the main landing-gear bay aft of the wing centerbox structure. They are installed between FR42 and FR47/51 and span between the middle side panel and keel beam structure. Two slanting frames (connected together at one end to make an inverted V-shape) support and strengthen each panel at the edges of the wheel opening. The panels are chemically milled and stringers are riveted on their outer face. You can get access to both rear lower side panels from behind the belly fairing structure.
(9) Stringers and Skin Stiffeners
(a) The stringers are the longitudinal stiffeners of the fuselage shell. They are made of aluminum-alloy Z-section which are formed or machined. They are riveted between the frames and the skin panels.
(b) The skin stiffeners make the skin stronger. They are riveted to the skin in areas of high stress (fuselage section and skin panel joints, cabin windows, emergency exits and door openings). Skin stiffeners are chemically milled or machined from forgings.
(10) Floor Structure
The passenger compartment is a pressurized zone. The area below the passenger compartment floor-structure is unpressurized. The floor pressure limit-zone consists of the top-skin panel of the wing center-box and two adjacent diaphragms. The diaphragms forward of the wing box connect with a pressure bulkhead installed in the lower part of FR35. The rear diaphragm (which is also the top panel of the main landing-gear bay) connects with the pressure bulkhead at FR46. Longitudinal beams extend the length of the center fuselage and hold the passenger compartment floor above the pressure limit structure. The forward beam section is supported between a crossbeam installed at FR35 and the wing center box. The rear beam section is supported between the wing box and a crossbeam installed at FR47. Support struts are attached to the crossbeams at each end. Seat and floor support tracks are installed on the longitudinal beams and screws attach floor panels to the track structure. You can remove the floor panels for maintenance work, or to replace them. The longitudinal beams, crossbeams, support-struts, seat-tracks and floor support tracks are made of aluminum alloy. They are either extruded or milled. The floor panels are made of honeycomb core which is bonded between Glassfiber Reinforced Plastic (GFRP)
The passenger compartment is a pressurized zone. The area below the passenger compartment floor-structure is unpressurized. The floor pressure limit-zone consists of the top-skin panel of the wing center-box and two adjacent diaphragms. The diaphragms forward of the wing box connect with a pressure bulkhead installed in the lower part of FR35. The rear diaphragm (which is also the top panel of the main landing-gear bay) connects with the pressure bulkhead at FR46. Longitudinal beams extend the length of the center fuselage and hold the passenger compartment floor above the pressure limit structure. The forward beam section is supported between a crossbeam installed at FR35 and the wing center box. The rear beam section is supported between the wing box and a crossbeam installed at FR47. Support struts are attached to the crossbeams at each end. Seat and floor support tracks are installed on the longitudinal beams and screws attach floor panels to the track structure. You can remove the floor panels for maintenance work, or to replace them. The longitudinal beams, crossbeams, support-struts, seat-tracks and floor support tracks are made of aluminum alloy. They are either extruded or milled. The floor panels are made of honeycomb core which is bonded between Glassfiber Reinforced Plastic (GFRP)
(11) Floor Structure
The passenger compartment is a pressurized zone. The area below the passenger compartment floor-structure is unpressurized. The floor pressure limit-zone consists of the top-skin panel of the wing center-box and two adjacent diaphragms. The diaphragms forward of the wing box connect with a pressure bulkhead installed in the lower part of FR35.8. The rear diaphragm (which is also the top panel of the main landing-gear bay) connects with the pressure bulkhead at FR46. Longitudinal beams extend the length of the center fuselage and hold the passenger compartment floor above the pressure limit structure. The forward beam section is supported between a crossbeam installed at FR35.8 and the wing center box. The rear beam section is supported between the wing box and a crossbeam installed at FR47. Support struts are attached to the crossbeams at each end. Seat and floor support tracks are installed on the longitudinal beams and screws attach floor panels to the track structure. You can remove the floor panels for maintenance work, or to replace them. The longitudinal beams, crossbeams, support-struts, seat-tracks and floor support tracks are made of aluminum alloy. They are either extruded or milled. The floor panels are made of honeycomb core which is bonded between Glassfiber Reinforced Plastic (GFRP)
The passenger compartment is a pressurized zone. The area below the passenger compartment floor-structure is unpressurized. The floor pressure limit-zone consists of the top-skin panel of the wing center-box and two adjacent diaphragms. The diaphragms forward of the wing box connect with a pressure bulkhead installed in the lower part of FR35.8. The rear diaphragm (which is also the top panel of the main landing-gear bay) connects with the pressure bulkhead at FR46. Longitudinal beams extend the length of the center fuselage and hold the passenger compartment floor above the pressure limit structure. The forward beam section is supported between a crossbeam installed at FR35.8 and the wing center box. The rear beam section is supported between the wing box and a crossbeam installed at FR47. Support struts are attached to the crossbeams at each end. Seat and floor support tracks are installed on the longitudinal beams and screws attach floor panels to the track structure. You can remove the floor panels for maintenance work, or to replace them. The longitudinal beams, crossbeams, support-struts, seat-tracks and floor support tracks are made of aluminum alloy. They are either extruded or milled. The floor panels are made of honeycomb core which is bonded between Glassfiber Reinforced Plastic (GFRP)
(12) Floor Structure
The passenger compartment is a pressurized zone. The area below the passenger compartment floor-structure is unpressurized. The floor pressure limit-zone consists of the top-skin panel of the wing center-box and two adjacent diaphragms. The diaphragms forward of the wing box connect with a pressure bulkhead installed in the lower part of FR35. The rear diaphragm (which is also the top panel of the main landing-gear bay) connects with the pressure bulkhead at FR46. Longitudinal beams extend the length of the center fuselage and hold the passenger compartment floor above the pressure limit structure. The forward beam section is supported between a crossbeam installed at FR35 and the wing center box. The rear beam section is supported between the wing box and a crossbeam installed at FR47/51. Support struts are attached to the crossbeams at each end. Seat and floor support tracks are installed on the longitudinal beams and screws attach floor panels to the track structure. You can remove the floor panels for maintenance work, or to replace them. The longitudinal beams, crossbeams, support-struts, seat-tracks and floor support tracks are made of aluminum alloy. They are either extruded or milled. The floor panels are made of honeycomb core which is bonded between Glassfiber Reinforced Plastic (GFRP)
The passenger compartment is a pressurized zone. The area below the passenger compartment floor-structure is unpressurized. The floor pressure limit-zone consists of the top-skin panel of the wing center-box and two adjacent diaphragms. The diaphragms forward of the wing box connect with a pressure bulkhead installed in the lower part of FR35. The rear diaphragm (which is also the top panel of the main landing-gear bay) connects with the pressure bulkhead at FR46. Longitudinal beams extend the length of the center fuselage and hold the passenger compartment floor above the pressure limit structure. The forward beam section is supported between a crossbeam installed at FR35 and the wing center box. The rear beam section is supported between the wing box and a crossbeam installed at FR47/51. Support struts are attached to the crossbeams at each end. Seat and floor support tracks are installed on the longitudinal beams and screws attach floor panels to the track structure. You can remove the floor panels for maintenance work, or to replace them. The longitudinal beams, crossbeams, support-struts, seat-tracks and floor support tracks are made of aluminum alloy. They are either extruded or milled. The floor panels are made of honeycomb core which is bonded between Glassfiber Reinforced Plastic (GFRP)