Patent Publication Number: US-2022234716-A1

Title: Connector to Connect a Center Wing Box to a Bulkhead of an Aircraft

Description:
RELATED APPLICATIONS 
     This application claims priority from U.S. Provisional App. No. 63/142,173, filed 27 Jan. 2021, the disclosure of which is incorporated by reference herein in its entirety. 
    
    
     TECHNOLOGICAL FIELD 
     The present disclosure relates generally to the field of aircraft and, particularly, to a connector that connects a center wing box to a bulkhead. 
     BACKGROUND 
     The structural features of an aircraft include a fuselage that includes the structural core of the aircraft and a wing assembly that forms and supports the wings. The wing assembly includes wing boxes that are the primary load carrying structure of the wings and a center wing box. The center wing box is connected to each of the wing boxes and is located in the fuselage between the wing boxes. 
     The center wing box experiences stresses such as tension, compression, shear and torsion due to aerodynamic forces from the wings while in flight, and due to the weight of the wings themselves and from the fuel contained within the wings when the aircraft is on the ground. The center wing box supports the wing boxes and transmits the forces from the wings to the fuselage. 
     Prior designs include the center wing box rigidly connected to the forward fuselage. The rigid connection may induce very high loads due to the difference in relative displacement between the two structures (this phenomenon is less critical at the upper wing connection but very critical at the lower wing connection). To accommodate for these forces, the prior designs include additional structural elements, such as titanium forgings including an underwing longeron to carry these large loads. However, these additional structures are expensive and also add weight to the aircraft that reduces the efficiency. These additional structures have experienced premature fatigue cracking that require rework and/or replacement. Further, these structures can be located within the aircraft in positions that are difficult to access. This makes replacement more difficult and requires greater amounts of time that keep the aircraft out of service. 
     Further, the structural features provide for some aircraft to be manufactured in a modular fashion. Different sections of the aircraft can be manufactured separately and then brought together and assembled. For example, the wing assembly can be manufactured separately from the fuselage. During the assembly process, a mostly complete nose to tail fuselage is lowered onto a complete tip to tip wing and then connected together. This can enable high production rates and save factory space and assembly costs. This modular approach requires a design that provides for connecting the wing assembly to the fuselage. 
     SUMMARY 
     One aspect is directed to a connector to connect a center wing box to a bulkhead of an aircraft. The connector comprises a panel comprising a first edge positioned at the center wing box, an opposing second edge positioned at the bulkhead, and a central section. A first flexible seal extends across the panel and provides for relative movement between the first edge and the central section. A second flexible seal extends across the panel and provides for relative movement between the second edge and the central section. 
     In another aspect, the first flexible seal is spaced apart on the panel from the second flexible seal. 
     In another aspect, each of the first flexible seal and the second flexible seal are constructed from a flexible membrane material. 
     In another aspect, the panel comprises a first flange that comprises the first edge and an opposing inner edge with the inner edge connected to the first flexible seal, a second flange that comprises the second edge and an opposing inner edge with the inner edge connected to the second flexible seal, and the central section connected to inner edges of each of the first flexible seal and the second flexible seal. 
     In another aspect, a first support comprising a plurality of first stiffener arms is attached to the center wing box and the central section with the first stiffener arms configured to prevent interference with the first flexible seal, and a second support comprising a plurality of second stiffener arms attached to the bulkhead and the central section with the second stiffener arms configured to prevent interference with the second flexible seal. 
     In another aspect, the first and second stiffener arms are aligned in pairs along a length of the panel with the first and second stiffener arms of each of the pairs positioned in an overlapping configuration on opposing sides of the panel. 
     In another aspect, lug and clevis joints with pins pivotally connect the first stiffener arms to the center wing box and pivotally connect the second stiffener arms to the bulkhead. 
     In another aspect, the lug and clevis joints provide for movement of the first stiffener arms relative to the center wing box and the second stiffener arms relative to the bulkhead. 
     In another aspect, closeout panels are positioned on lateral sides of the panel with the closeout panels comprising pressure panels aligned at opposing angular orientations relative to the panel to structurally connect the panel to the fuselage. 
     One aspect is directed to a connector to connect a center wing box to a bulkhead of an aircraft. The connector comprises a panel sized to extend across a gap formed between the center wing box and the bulkhead. The panel comprises: a central section sized to extend across the gap with the central section comprising a first edge and an opposing second edge; a first flange pivotally connected to the first edge at a first flexible seal with the first flange configured to be connected to the center wing box; a second flange pivotally connected to the second edge at a second flexible seal with the second flange configured to be connected to the bulkhead; a first support mounted to the center wing box and to a first side of the central section; and a second support mounted to the bulkhead and to a second side of the central section. 
     In another aspect, each of the first flexible seal and the second flexible seal extend across an entire width of the panel. 
     In another aspect, the first support comprises a plurality of stiffener arms spaced apart across the width of the panel with each of the stiffener arms comprising a first end configured to be connected to the center wing box and an opposing second end positioned at and connected to the central section. 
     In another aspect, the first support is configured to prevent interference with the first flexible seal and the second support is configured to prevent interference with the second flexible seal. 
     In another aspect, each of the first flexible seal and the second flexible seal are straight and are aligned parallel. 
     One aspect is directed to a method of connecting a center wing box to a bulkhead of an aircraft. The method comprises: attaching a first flange of a panel to the center wing box; attaching a second flange of the panel to the bulkhead; positioning a central section of the panel along a gap formed between the center wing box and the bulkhead; aligning a first flexible seal that connects the first flange to the central section along the center wing box; and aligning a second flexible seal that connects the second flange to the central section along the bulkhead. 
     In another aspect, the method further comprises aligning the central section at a downward angle with the first flange positioned vertically above second flange. 
     In another aspect, the method further comprises attaching a plurality of first stiffener arms across a width of the panel with each of the first stiffener arms mounted to the center wing box and the central section, and attaching a plurality of second stiffener arms across the width of the panel with each of the second stiffener arms mounted to the bulkhead and the central section. 
     In another aspect, the method further comprises attaching the first stiffener arms to a first side of the panel and the second stiffener arms to an opposing second side of the panel. 
     In another aspect, the method further comprises attaching the first stiffener arms and the second stiffener arms to the central section without interfering with the first flexible seal and the second flexible seal. 
     In another aspect, attaching the second flange of the panel to the bulkhead comprises attaching the second flange to an upper chord of the bulkhead. 
     In another aspect, the method further comprises attaching the first flange to an upper panel of the center wing box. 
     The features, functions and advantages that have been discussed can be achieved independently in various aspects or may be combined in yet other aspects, further details of which can be seen with reference to the following description and the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an aircraft. 
         FIG. 2  is a side schematic view of a fuselage of an aircraft. 
         FIG. 3  is a partial perspective view of a connector that connects a center wing box to a bulkhead of an aircraft. 
         FIG. 4  is schematic diagram of a panel for connecting a center wing box to a bulkhead of an aircraft. 
         FIG. 5  is a schematic side view of a panel connecting a center wing box to a bulkhead of an aircraft. 
         FIG. 6  is a perspective view of first supports connected to a panel and to a center wing box of an aircraft. 
         FIG. 7  is a perspective view of second supports connected to a panel and to a bulkhead of an aircraft. 
         FIG. 8  is a perspective view of paired first and second supports with the panel removed from the drawing for clarity. 
         FIG. 9  is a flowchart diagram of a method of connecting a center wing box to a bulkhead of an aircraft. 
         FIG. 10  is a flowchart diagram of a method of connecting a center wing box to a bulkhead of an aircraft. 
     
    
    
     DETAILED DESCRIPTION 
     As seen in  FIG. 1 , an aircraft  100  includes a fuselage  101  with a nose  109  and a tail  108 . A wing assembly  102  is connected to the fuselage  101 . The wing assembly  102  includes a center wing box  80  and outer wing boxes  89 . The center wing box  80  is positioned within the fuselage  101  and is connected to and supports the outer wing boxes  89 . The center wing box  80  includes a front spar  82  and a rear spar  84 . 
       FIG. 2  illustrates a side schematic view of the fuselage  101  with the outer wing box  89  removed for clarity. The fuselage  101  includes an elongated shape and extends between the tail  108  and nose  109 . In one example as illustrated in  FIG. 2 , the fuselage  101  is divided into an upper section  110  and a lower section  111 . The upper section  110  includes a cabin area  106  with a floor  104 . The upper section  110  includes various components to provide for transporting passengers, such as but not limited to seats, overhead storage, lavatories, and various other amenities. 
     The lower section  111  is positioned below the floor  104  of the upper section  110 . The lower section  111  includes a forward cargo deck  112  for holding cargo on either the right or left side of the fuselage  101 . A main landing gear wheel well  113  is positioned in a rear section of the fuselage  101  and a lower aft hold  114  that includes an aft cargo hold or deck is positioned aft of the main landing gear wheel well  113 . 
     A bulkhead  90  is located aft of the forward cargo deck  112 . The bulkhead  90  extends upward a limited distance from the lower portion of the fuselage  101 . In one example, a top chord of the bulkhead  90  is positioned vertically below the floor  104 . The center wing box  80  is located aft of and spaced away from the bulkhead  90 . A connector  10  connects the center wing box  80  to a bulkhead  90 . The bulkhead  90  offset from the center wing box  80  facilitates the assembly process when the aircraft  100  is manufactured in separate assemblies. This offset positioning facilitates rapid wing to body join when a mostly complete fuselage  101  is lowered onto a fully complete wing assembly  102 . This supports a higher rate of production than would be available in other designs. 
     In the illustrated embodiment, the aircraft  100  is a commercial aircraft with the upper section  110  configured for passengers and flight crew and the lower section  111  configured for cargo storage and aircraft equipment/structural components. The design with a connector  10  that connects the center wing box  80  to the bulkhead  90  is also applicable in various other aircraft  100 , including but not limited to various commercial and non-commercial aircraft. These aircraft  100  can include the same or different configurations for storing cargo and/or passengers. 
       FIG. 3  illustrates a forward section of the center wing box  80  positioned in proximity to the bulkhead  90 . The center wing box  80  includes an upper panel  81  and a front spar  82 . Beams  83  can extend along the upper panel  81  across a width of the fuselage  101 . The bulkhead  90  is positioned forward from the front spar  82  of the center wing box  80 . The bulkhead  90  includes panels  91  with a curved shape that conform to the substantially rounded sectional shape of the fuselage  101 . A deck  92  forms a chord that extends across the fuselage  101 . In one example, both the panels  91  of the bulkhead  90  and the front spar  82  of the center wing box  80  are aligned substantially vertically within the fuselage  101 . In other examples, one or more of the panels  91  and front spar  82  are aligned at non-vertical angles. 
     A gap  120  is formed between the center wing box  80  and the bulkhead  90 . The size of the gap  120  can vary depending upon the designs of the fuselage  101  and/or wing assembly  102 . The connector  10  extends across the gap  120  and connects to each of the center wing box  80  and the bulkhead  90 . The connector  10  is attached to the center wing box  80  and the bulkhead  90  to allow specific directions of relative motion between the wing assembly  102  and the fuselage  101 . 
     The connector  10  decouples some interaction between the wing assembly  102  and fuselage  101  that occurs during various flight, ground, and/or thermal conditions thereby relieving stresses on the aircraft  100  due to the difference in relative displacement between the two structures, while at the same time the connector  10  allows the wing assembly  102  and the fuselage  101  to support internal pressure loads and allows the wing assembly  102  to support fuselage  101  loads. The connector  10  also enables a rapid connection of the wing assembly  102  and fuselage  101  during assembly. The connector  10  accommodates the gap  120  formed between the center wing box  80  and the bulkhead  90 . 
     The connector  10  includes a panel  20  that is connected to each of the center wing box  80  and bulkhead  90  and that spans across the gap  120 .  FIG. 4  schematically illustrates the panel  20  that includes a first flange  24  with a first edge  21 , a second flange  25  with a second edge  22 , and an intermediate central section  23 . The panel  20  includes a length L measured between the first and second edges  21 ,  22 , and a width W measured between opposing lateral edges. The panel  20  includes a length L to extend along the gap  120  with the first edge  21  connected to the center wing box  80  and the second edge  22  connected to the bulkhead  90 . The panel  20  also includes a first flexible seal  30  that extends across the width W and that provides for relative movement between the first edge  21  of the first flange  24  and the central section  23 . A second flexible seal  40  that extends across the width W and provides for relative movement between the second edge  22  of the second flange  25  and the central section  23 . 
       FIG. 5  schematically illustrates the connection of the first and second flexible seals  30 ,  40 . Each of the first and second flexible seals  30 ,  40  are formed by a silicone rubber strip sized to extend across the width W of the panel  20 . In one example, each of the first and second flexible seals  30 ,  40  are straight and aligned parallel to one another. The first flexible seal  30  overlaps with and is connected to the first flange  24  and the central section  23 . The second flexible seal  40  overlaps with and is connected to the second flange  25  and the central section  23 . Fasteners  130  connect the first and second flexible seals  30 ,  40  respectively to the central section  23  and the first and second flanges  24 ,  25 . Fasteners  130  further connect the first flange  24  to the center wing box  80  and the second flange  25  to the bulkhead  90 . Fasteners  130  can include but are not limited to rivets, screw, and bolts. The flexible seals  30 ,  40  can be constructed from a variety of different materials, including but not limited to silicone rubber, vinyl, nitrile, latex, and combinations thereof. 
     In one example as illustrated in  FIG. 5 , the first and second flexible seals  30 ,  40  are attached to an upper surface respectively of the central section  23  and the first and second flanges  24 ,  25 . In other examples, one or more of the first and second flexible seals  30 ,  40  are attached to a lower surface of the central section  23  and the first and second flanges  24 ,  25 . 
     In another example, the central section  23  is spaced away from the first flange  24  by a gap. The flexible seal  30  spans the gap and is connected to each of the central section  23  and the first flange  24 . In another example, the central section  23  is spaced away from the second flange  25  and the second flexible seal  40  spans the gap and connects to each of the central section  23  and the second flange  25 . 
     In one example as illustrated in  FIG. 5 , the central section  23  overlaps with the first flange  24  at the first flexible seal  30 . The first flange  24  and the central section  23  abut together and slide across one another during relative movement between the first flange  24  and the central section  23 . In one example, the overlapping sections of the central section  23  and the first and second flanges  24 ,  25  are flat to facilitate relative movement. The first flexible seal  30  is positioned on a top edge of the first flange  24  and the central section  23  at the overlapping area. Similarly, the central section  23  overlaps with the second flange  25  at the second flexible seal  40 . The central section  23  abuts against and slides across the second flange  25  during the relative movement. The second flexible seal  40  is positioned over the overlapping area. 
     The central section  23 , the first flange  24 , the second flange  25  are each rigid and can be constructed from a variety of materials. Materials include but are not limited to aluminum, steel, titanium, and fiber reinforced composite or metallic material, such as a carbon fiber reinforced polymer (CFRP) material. Fiber reinforced composite materials additionally or alternatively may be described as, or referred to as, fiber reinforced polymers, or plastics. As used herein, a fiber reinforced composite material should be understood to include at least an epoxy or other polymer or binding material together with fibers, such as (but not limited to) carbon fibers, glass fibers, boron fibers, para-aramid (e.g., Kevlar®) fibers, and/or other fibers. The use of carbon fiber materials provides for lower corrosion and fatigue cracking when compared to metallic materials. The carbon fiber materials are also able to be exposed to moisture that can accumulate in this area of the aircraft  100  and lead to corrosion in other materials. Further, carbon fiber is better able to handle the significant cyclic loading that occurs during operation of the aircraft  100 . Carbon fiber is also less likely to have fatigue cracking. Further, the location of the connector  10  makes it difficult to access after the aircraft  100  is assembled thus design concerns that minimize issues are appreciated. The central section  23  and flanges  24 ,  25  can have the same or different constructions. 
     The panel  20  is positioned at a downward sloping angle with the first flange  24  that is connected to the center wing box  80  being vertically higher than the second flange  25  that is connected to the bulkhead  90 . The central section  23  is positioned at an angle α as illustrated in  FIG. 5 . The angled slope provides for moisture that accumulates in the area to run off of the connector  10 . 
     The connector  10  can also include first supports  60  that connect the panel  20  to the center wing box  80  and second supports  70  that connect the panel  20  the bulkhead  90 . The first supports  60  have a cantilevered structure and are connected to the center wing box  80  and extend outward and connect to and support the central section  23 . The second supports  70  also include a cantilevered structure and are connected to the bulkhead  90  and extend outward and are connected to the central section  23 . Both the first and second supports  60 ,  70  are configured to prevent interference with the first and second seals  30 ,  40 . 
     As illustrated in  FIG. 6 , each of the first supports  60  include an arm  61  that is connected to the central section  23  and a mount  64  that is connected to the center wing box  80  via overwing beams  83 . The arm  61  is mounted to the central section  23  away from the seal  30 . This positioning ensures that the arm  61  does not impede the movement of the panel  20  relative to the center wing box  80 . In one example, the arm  61  is positioned in proximity to the lower edge of the flexible seal  30 . The mount  64  is secured to the center wing box  80 . In one example as illustrated in  FIG. 6 , the mounts  64  are connected to overwing beams  83  that are spaced apart across the width of the center wing box  80 . In one example, the front edge of the beams  83  that secure the mounts  64  are aligned substantially perpendicular to the front spar  82 . A connector  62  secures the arm  61  to the mount  64 . The connector  62  provides for the arm  61  to pivot relative to the mount  64 . In one example, the connector  62  is a pin that extends through the arm  61  and mount  64 . In one example, a spherical bearing is included that provides for the relative movement between the arm  61  and the mount  64 . In one example, the end of the arm  61  is a clevis with a forked shape that extends on opposing sides of the mount  64 . The connector  62  extends through the clevis and the mount  64  and provides for the pivoting movement. 
     The second support  70  supports a lower section of the panel  20 . As illustrated in  FIG. 7 , each of the second supports  70  includes an arm  71  that is connected to the central section  23  and a mount  74  that is connected to the bulkhead  90 . The arm  71  and mount  74  are positioned away from the flexible seal  40  to ensure it does not impede the movement of the panel  20  relative to the bulkhead  90 . In one example as illustrated in  FIG. 7 , the mounts  74  are connected to the face of the bulkhead  90  that is positioned towards the center wing box  80 . A connector  72  secures the arm  71  to the mount  74  and provides for the arm  71  to pivot relative to the mount  74 . In one example, the connector  72  is a pin that extends through the arm  71  and mount  74 . In one example, a spherical bearing provides for additional relative movement between the arm  71  and the mount  74 . In one example, the end of the arm  71  is a clevis with a forked shape that extends on opposing sides of the mount  74 . The connector  72  extends through the clevis and the mount  74  and provides for the pivoting movement. 
     The first and second supports  60 ,  70  are positioned on opposite sides of the panel  20 . In one example, the first supports  60  are positioned on a top side of the panel  20  with the arms  61  attached to the first side of the central section  23 . The second supports  70  are positioned on a bottom side of the panel  20  with the arms  71  attached to the opposing second side of the central section  23 . 
     The first and second supports  60 ,  70  are connected to the panel  20  along the width W. The number and spacing of the first and second supports  60 ,  70  can vary. In one example, first and second supports  60 ,  70  are evenly spaced across the width of the panel  20 . In another example, one or both of the first supports  60  and the second supports  70  are randomly positioned across the width. In one example as illustrated in  FIG. 8 , the first and second supports  60 ,  70  are pair together in an overlapping orientation along the width. A first support  60  is attached to the first side of the panel  20  opposite from a second support  70  that is attached to the opposing second side of the panel  20  (the panel  20  is not illustrated in  FIG. 8  to show the relative positions of the first and second supports  60 ,  70 ). The first and second supports  60 ,  70  are aligned in pairs along the width of the panel  20 . In another example, one or more of the first and second supports  60 ,  70  are arranged in a non-overlapping orientation. 
     The first and second supports  60 ,  70  are attached respectively to the panel  20  in various manners, including but not limited to mechanical fasteners, adhesives, and combinations thereof. The first and second supports  60 ,  70  can be constructed of various materials, including but not limited to aluminum, titanium, and fiber reinforced composite materials. 
     Closeout panels  140  are positioned at each of the lateral sides of the panel  20 . The closeout panels  140  connect the panel  20  to the skin of the fuselage  101 .  FIGS. 7 and 8  illustrate closeout panels  140  positioned on the lateral sides of the panel  20 . The closeout panels  140  are formed by multiple pressure panels  141  each having a rigid shape. The closeout panels  140  include vertically-aligned pressure panels  141  that are connected together and also connected to one or more of the bulkhead  90  and the skin  115  of the fuselage  101 . A horizontally-aligned pressure panel  141  forms a floating panel that is loosely connected to the vertical pressure panels  141  and provides for relative movement with the vertical pressure panels  141 , wing  80 , and skin  115 . 
       FIG. 9  illustrates a method of connecting a center wing box  80  to a bulkhead  90  of an aircraft  100 . This method includes attaching a first flange  24  of a panel  20  to the center wing box  80  (block  200 ). A second flange  25  is attached to the bulkhead  90  (block  202 ). A central section  23  of the panel  20  is positioned along a gap  120  formed between the center wing box  80  and the bulkhead  90  (block  204 ). A first flexible seal  30  that connects the first flange  24  to the central section  23  is aligned along the center wing box  80  (block  206 ). A second flexible seal  40  that connects the second flange  25  to the central section  23  is aligned along the bulkhead  90  (block  208 ). 
       FIG. 10  illustrates another method of connecting a center wing box  80  to a bulkhead  90 . The method includes attaching the second flange  25  to the bulkhead  90  (block  300 ). The panel  20  is then positioned relative to the gap  120  (block  302 ). This includes positioning the second flexible seal  40  at the bulkhead  90 , the first flexible seal  30  at the center wing box  80 , and the central section  23  along the gap  120 . The first flange  24  is then attached to the center wing box  80  (block  304 ). 
     In the various methods, the order of the attachment and positioning can vary. For example, the first flange  24  can be connected to the center wing box  80  before or after the second flange  25  is attached to the bulkhead  90 . 
     Returning to  FIG. 2 , the connector  10  is part of the pressure vessel of the aircraft  100 . The pressure vessel includes the forward cargo deck  112  and cabin area  106 . Pressure under the wing assembly  102  and in the landing gear well  113  is at outside air pressure. The connector  10  further provides a shear capable load path to accommodate movement of the center wing box  80  relative to the bulkhead  90  and/or fuselage  101 . Further, the connector  10  allows for the wing assembly  102  to flex with respect to the fuselage  101 . The flexible nature of the connector  10  is lighter than an otherwise rigid structure that would resist the movement and would add weight to the aircraft  100 . 
     In one example, a single panel  20  extends across the width of the fuselage  101 . In other examples, two or more panels are combined to extend across the width. The different panels  20  can include the same or different shapes and when combined together the separate panels  20  extend across the fuselage  101 . 
     The connector  10  can be used on a variety of aircraft  100 . Aircraft  100  include but are not limited to manned aircraft, unmanned aircraft, manned spacecraft, unmanned spacecraft, manned rotorcraft, unmanned rotorcraft, satellites, rockets, missiles, and combinations thereof. 
     By the term “substantially” with reference to amounts or measurement values, it is meant that the recited characteristic, parameter, or value need not be achieved exactly. Rather, deviations or variations, including, for example, tolerances, measurement error, measurement accuracy limitations, and other factors known to those skilled in the art, may occur in amounts that do not preclude the effect that the characteristic was intended to provide. 
     The present invention may be carried out in other ways than those specifically set forth herein without departing from essential characteristics of the invention. The present embodiments are to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.