Abstract:
A method for assembling a main wing having an upper skin and plurality of spars is disclosed. The front spar and rear spar are fastened to a back surface of the upper skin using an adhesive agent without using rivets, whereby the front surface of the upper skin becomes smooth.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an improved method for assembling a main wing made of an aluminum alloy. 
       BACKGROUND OF THE INVENTION 
       [0002]    A main wing made of aluminum alloys used in aircraft is composed of separately manufactured outer plates, beams, and ribs, and the wing is assembled by fastening these parts with rivets. However, when the abovementioned parts are fastened with rivets, there is an unavoidable increase in the number of assembly processes due to rivet hole forming work and rivet driving work, a concentration of stress in the rivet holes, and a drop in the smoothness of the wing surface at the rivet head parts. 
         [0003]    Accordingly, a method in which the main wing is joined by welding has been proposed in U.S. Pat. No. 6,116,539 as a method for solving such problems. This main wing is shown in  FIG. 12  hereof. 
         [0004]    Referring to  FIG. 12 , the aircraft forward wing structure  100  comprises a wing upper surface box structure  101 , a wing lower surface box structure  102 , and an intermediate spar  103 . The wing upper surface box structure  101 , wing lower surface box structure  102 , and an intermediate spar  103  are respectively joined by laser welding. As a result, the problem of rivet fastening is solved. 
         [0005]    Since the abovementioned laser welding is performed on materials made of an aluminum alloy, welding defects such as solidification cracks, blow holes, and the like are generated in the welded parts, and there is a danger that the mechanical strength in the welded parts will drop. 
       SUMMARY OF THE INVENTION 
       [0006]    It is an object of the present invention to provide a method for assembling a main wing made of an aluminum alloy which can ameliorate the increase in the number of assembly processes, concentration of stress, and drop in the smoothness of the wing surface caused by rivet-fastening, as well as the drop in mechanical strength caused by the generation of defects due to welding. 
         [0007]    According to the present invention, there is provided a method for assembling a main wing made of an aluminum allow, which comprises the steps of: positioning an upper skin of a wing skin on a bonding cart on the basis of a first reference part disposed on a forming surface of the bonding cart; positioning and fastening a plurality of spars via an adhesive agent on the upper skin on the basis of a second reference part disposed on the bonding cart; covering at least bonding sites of the upper skin and each of the spars with a backing film; and adhesively joining the upper skin and the spars by pressurizing and heating the bonding sites inside an autoclave, removing the air from the inside of the backing film, and curing the adhesive agent. 
         [0008]    Since the upper skin and the plurality of spars are thus joined by an adhesive agent, rivet-fastening becomes unnecessary, and the number of assembly processes can be reduced. Furthermore, the concentration of stress does not occur, the wing surface smoothness is improved so that the resistance of the aircraft body is reduced, and the air power performance is improved. 
         [0009]    Moreover, welding defects such as solidification cracks, blow holes, and the like occurring in conventional welding are not generated, and the mechanical strength can be improved, thus making it possible to manufacture a highly reliable main wing made of an aluminum alloy. 
         [0010]    Preferably, the method further comprises the steps of separating an upper skin assembly, which is composed of the bonded upper skin and the plurality of spars, from the bonding cart after the adhesive agent has cured; positioning the upper skin assembly on an assembly jig on the basis of a third reference part disposed on the assembly jig; rivet-fastening the upper skin assembly and a plurality of ribs after the ribs are disposed in predetermined positions on the upper skin assembly; and rivet-fastening the upper skin assembly and lower skin after the lower skin of the wing skin has been disposed in a predetermined position with respect to the upper skin assembly to which the ribs have been riveted. 
         [0011]    Since the lower skin and the plurality of ribs are fastened by rivets to the upper skin assembly, the upper skin assembly and lower skin are strongly fastened, and the rigidity of the main wing can be improved. 
         [0012]    Desirably, the method further comprises holding the plurality of spars by fastening a beam pressing jig to the upper parts of the plurality of spars when the spars are positioned on and fastened to the upper skin. Accordingly, since the plurality of spars is held by this beam pressing jig, the bonding sites between the upper skin and plurality of spars are pressurized and heated, and deformation of the plurality of spars is suppressed until the adhesive agent is cured. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0013]    Certain preferred embodiments of the present invention will be described in detail below, by way of example only, with reference to the accompanying drawings, in which: 
           [0014]      FIG. 1  is a sectional view showing an aircraft main wing assembled by a method according to the present embodiment; 
           [0015]      FIGS. 2A and 2B  are schematic views showing the adhesive pretreatment of an upper skin and a rear spar; 
           [0016]      FIGS. 3A and 3B  are schematic views showing the positioning of the upper skin; 
           [0017]      FIGS. 4A through 4C  are schematic views showing the positioning of the front spar and rear spar; 
           [0018]      FIGS. 5A through 5C  are schematic views showing a state in which the front spar and rear spar are held; 
           [0019]      FIGS. 6A through 6D  are schematic views showing the front spar and rear spar in a simplified representation; 
           [0020]      FIG. 7  is a sectional view showing a state in which the areas around the bonding sites of the upper skin and the front spar and rear spar are covered by a backing film; 
           [0021]      FIG. 8  is a perspective view showing a state in which the upper skin, front spar and rear spar are placed in a autoclave and pressurized/heated for each bonding cart; 
           [0022]      FIGS. 9A through 9C  are schematic views showing a state in which the wing upper structure is positioned on the forming surface of an assembly jig; 
           [0023]      FIGS. 10A through 10C  are schematic views showing a state in which a rib is mounted inside a wing upper structure; 
           [0024]      FIG. 11  is a flow chart showing the assembly procedure for the main wing structure; and 
           [0025]      FIG. 12  is a schematic view showing a conventional aircraft main wing. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    Reference is first made to  FIG. 1  showing in cross-section an aircraft main wing structure  10  assembled in accordance with the present invention. Arrowed FRONT indicates a front direction of the aircraft. 
         [0027]    The main wing structure  1  shown in  FIG. 1  comprises an upper skin (wing upper surface structure)  11 , a lower skin (wing lower surface structure)  16 , and a front spar  12  and rear spar  13  which are interposed between the upper skin  11  and lower skin  16 . The front spar  12  and rear spar  13  are joined to the abovementioned upper skin  11  by bonding, and function as intermediate beams in the span direction of the wing (front-back direction of the plane of the page). 
         [0028]    A plurality of ribs  14  (only one is shown in the drawings) is fastened by rivets to the abovementioned upper skin  11 , front spar  12  and rear spar  13 . 
         [0029]    The abovementioned lower skin  16  is fastened by rivets to the abovementioned front spar  12 , rear spar  13  and of ribs  14 . 
         [0030]    In the drawings, the portions indicated by thick lines are bonding sites  18 ,  18  where the front spar  12  and rear spar  13  are bonded to the upper skin  11 . 
         [0031]    For aerodynamic reasons, a highly precise smoothness is required in the upper surface of the upper skin  11 . Accordingly, in the present invention, the front spar  12  and rear spar  13  are bonded to the upper skin  11  instead of being fastened by rivets, so that a highly precise smoothness is obtained. 
         [0032]    A plurality of stringers  11   a  that extend in the wing span direction, as well as a plurality of attachment parts  11   b  that are lined up at intervals in the wing span direction so as to connect these stringers  11   a , are integrally formed on the lower surface of the upper skin  11 . 
         [0033]    The front spar  12  is a member that is substantially C-shaped in cross section, and comprises a web  12   a , flanges  12   b  and  12   c  that are integrally disposed on the upper and lower ends of this web  12   a , and a plurality of attachment parts  12   d  which are integrally formed so that these parts are lined up at intervals in the wing span direction in order to connect the web  12   a  and flanges  12   b ,  12   c . Furthermore,  12   e  is an interior hole used to lighten the weight, which is formed in the web  12   a.    
         [0034]    The rear spar  13  has the same shape as the front spar  12 , and comprises a web  13   a , flanges  13   b  and  13   c  that are integrally disposed on the upper and lower ends of this web  13   a , and a plurality of attachment parts  13   d  which are integrally formed so that these parts are lined up at intervals in the wing span direction in order to connect the web  13   a  and flanges  13   b  and  13   c . Furthermore, an interior hole  13   e  is formed in the web  13   a  in order to lighten the weight. 
         [0035]    Each of the abovementioned plurality of ribs  14  comprises an upper attachment part  14   a  used for attachment to the attachment parts  11   b  of the upper skin  11  by a plurality of rivets  21 , a front attachment part  14   b  which is used for attachment to the attachment parts  12   d  of the front spar  12  by a plurality of rivets  22 , a rear attachment part  14   c  which is used for attachment to the attachment parts  13   d  of the rear spar  13  by a plurality of rivets  23 , and a lower flange  14   d  which is used for attachment to the lower skin  16  by a plurality of rivets  24 . Furthermore,  14   e  indicates cut-outs which are formed in order to avoid the stringers  11   a  of the upper skin  11 , and  14   f  indicates interior holes used to lighten the weight. 
         [0036]    The lower skin  16  is fastened by rivets  24  to the flange  12   c  of the front spar  12 , the flange  13   c  of the rear spar  13 , and the lower flanges  14   d  of the ribs  14 . 
         [0037]    The assembly method for the main wing structure  1  described above will be described with reference to  FIGS. 2 through 11 . 
         [0038]      FIGS. 2A and 2B  show the bonding pretreatment of the upper skin  11  and rear spar  13 . 
         [0039]    In  FIGS. 2A and 2B , as a pretreatment used to change the respective surfaces of the aluminum alloy upper skin  11 , front spar  12  ( FIG. 1 ), and rear spar  13  into a state that is suited for boning, fine indentations and projections are formed in the surfaces by, for example, a sulfuric acid-chromic acid etching treatment or anodic oxidation treatment (a so-called anodizing treatment, such treatments include a chromic acid anodic oxidation treatment and a phosphoric acid anodic oxidation treatment). 
         [0040]    Following this pretreatment, masking is applied to the outer surface of the upper skin  11 , and the lower surface of the upper skin  11  and the entire front spar  12  and rear spar  13  are spray-coated with an adhesive primer. 
         [0041]    The adhesive primer promotes the adhesion of the adhesive agent to the surface provided with indentations and projections, and is used to heighten the adhesive strength. For example, an epoxy primer is suitable. Furthermore, in the main wing structure, besides an adhesive primer, an anti-rust primer and a fuel tank primer (used to prevent corrosion by the fuel) are used. 
         [0042]      FIGS. 3A and 3B  show the positioning of the upper skin  11 . 
         [0043]    In  FIG. 3A , the upper skin  11  is placed on the forming surface  31   a  of the bonding cart  31  with the lower surface facing upward, and the upper skin  11  is positioned using a plurality of positioning pins  32  and a plurality of positioning projections  33  constituting a first reference part disposed on the forming surface  31   a . Furthermore,  11   d  indicates the wing root end part of the upper skin  11 , and  11   e  indicates the wing tip end part of the upper skin  11 . 
         [0044]      FIG. 3B  shows a state in which the wing root end part  11   d  of the upper skin  11  has been positioned. 
         [0045]    The wing root end part  11   d  has positioned parts  11   f ,  11   f . Respective positioning holes  11   g  are formed in these positioned parts  11   f ,  11   f . Positioning pins  32 ,  32  are fit into these positioning holes  11   g ,  11   g , and the front and rear ends of the upper skin  11  are positioned by the positioning projections  33 ,  33 . 
         [0046]      FIGS. 4A ,  4 B and  4 C show a state in which the front spar  12  and rear spar  13  have been positioned. 
         [0047]    In  FIG. 4A , an epoxy adhesive film is pasted as an adhesive agent onto the bonding surfaces of the front spar  12  and rear spar  13 ; as is shown in  FIG. 4A , this assembly is placed on the forming surface of the bonding cart while the front spar  12  and rear spar  13  are positioned on the front end and rear end of the upper skin  11  shown in  FIG. 3B  by the plurality of positioning pins and the plurality of positioning projections  33 . 
         [0048]    A thermosetting adhesive agent such as an epoxy agent, phenol agent, resorcinol agent or the like is desirable as an adhesive agent, since such agents show little creep (i.e., minute slipping between the bonding sites) under a heavy load, and are resistant to heat, water, oil (including gasoline) and the like. 
         [0049]    Besides an adhesive agent that is pasted on, such as the film-form adhesive agent described above, it would also be possible to use an adhesive agent that is applied as a coating, such as a paste-form adhesive agent. 
         [0050]      FIG. 4B  shows a state in which the wing root end parts of the front spar  12  and rear spar  13  have been positioned. 
         [0051]    Specifically, positioning parts  12   f ,  13   f  are formed on one end of each of the two parts, i.e., front spar  12  and rear spar  13 , positioning holes  12   g ,  13   g  are respectively formed in these positioning parts  12   f ,  13   f , and positioning pins  36 ,  36  respectively disposed on upright plates  35 ,  35  on the bonding cart  31  are fit into these positioning holes  12   g ,  13   g.    
         [0052]      FIG. 4C  shows a state in which the wing tip end parts of the front spar  12  and rear spar  13  have been positioned. 
         [0053]    Specifically, positioned parts  12   h ,  13   h  are formed on the other ends of the front spar  12  and rear spar  13 , positioning holes  12   j ,  13   j  are respectively formed in these positioned parts  12   h ,  13   h , and positioning pins  38 ,  38  disposed on the forming surface  31   a  of the bonding cart  31  are fit into these positioning holes  12   j ,  13   j.    
         [0054]    The abovementioned positioning pins  36 ,  38  constitute a second reference part that is used to position the abovementioned front spar  12  and rear spar  13  on the abovementioned bonding cart  31 . 
         [0055]      FIGS. 5A ,  5 B and  5 C show a state in which the front spar  12  and rear spar  13  are held. 
         [0056]    In  FIG. 5A , a beam pressing jig  41  is placed on and fastened to the front spar  12  and rear spar  13 . This is done in order to suppress deformation of the front spar  12  and rear spar  13  during the pressing ad heating of the bonding sites between the upper skin  11  and the front spar  12  and rear spar  13 . 
         [0057]    The beam pressing jig  41  comprises a long part  43  which extends in the wing span direction, a plurality of cross members  44 ,  45 ,  46 ,  47 , and  48  which are attached so as to cross this long part  43 , and a plurality of resin pads  51  which are attached to the lower parts of the end parts of the abovementioned cross members  44  through  48  in order to contact the flanges  12   b ,  13   b  of the front spar  12  and rear spar  13 . 
         [0058]      FIGS. 5B and 5C  show a state in which the beam pressing jig  41  is fastened to the front spar  12 . Specifically, the respective pads  51  of the beam pressing jig  41  are fastened to the flange  12   b  of the front spar  12  by fastening members  53 . 
         [0059]    As is shown in  FIG. 5C , the fastening member  53  comprises a C-shaped fitting  55 , one end part  55   a  of which is engaged with the upper surface of the pad  51 , and a bolt member  56  which is screw-engaged with the other end part  55   b  of this C-shaped fitting, and whose upper end part is caused to contact the undersurface of the flange  12   b  of the front spar  12 . 
         [0060]    The bolt member  56  comprises a bolt main body  57 , a handle  58  which is attached to the lower part of this bolt main body  57 , and a contact member  57   a  which is attached to the upper end of the bolt main body  57 . When the handle  58  is turned, the bolt main body  57  is caused to move upward with respect to the other end part  55   b  of the C-shaped member  55 . Accordingly, the pad  51  and flange  12   b  are fastened by the first end part  55   a  of the C-shaped member  55  and the contact member  57   a  of the bolt member  56 , and the beam pressing jig  41  is fastened to the front spar  12 . On the side of the rear spar  13  as well, the beam pressing jig  41  is fastened by the fastening member  53  in the same manner as described above. 
         [0061]      FIGS. 6A through 6D  show the front spar  12  and rear spar  13  in a simplified representation. 
         [0062]    In  FIG. 6A , the adhesive agent is cured in a process of pressing and heating the bonding sites described later in a state in which the beam pressing jig  41  indicated by an imaginary line is fastened to the front spar  12  and rear spar  13 . Subsequently, almost no deformation occurs in the front spar  12  or rear spar  13  even in a state in which the beam pressing jig  41  is removed. 
         [0063]    As is shown in  FIG. 6B , almost no falling over (deformation) occurs in the front spar  12  or rear spar  13  even in a state in which the beam pressing jig  41  indicated by an imaginary line is removed from the front spar  12  and rear spar  13 . 
         [0064]      FIG. 6C  shows a state following the curing of the adhesive agent in a pressing and heating process performed in a state in which the beam pressing jig  41  ( FIG. 6A ) is not fastened to the front spar  12  or rear spar  13 . An undulation (deformation) is generated in the front spar  12  and rear spar  13 . 
         [0065]    As is shown in  FIG. 6D , in the front spar  12  and rear spar  13 , the sides of the respective flanges  12   b  and  13   b  have fallen over toward the inside. 
         [0066]      FIG. 7  shows a sectional view of a state in which the areas around the bonding sites between the upper skin  11  and front spar  12  and rear spar  13  are covered by a backing film. 
         [0067]    The areas around the bonding sites between the upper skin  11  and the front spar  12  and rear spar  13  are covered in the order described by a release film (not shown) which is a film that controls the amount of resin outflow, a bleeder cloth (not shown) which is a glass cloth that takes up the excess adhesive agent, and a breather cloth (not shown) which is a ventilating material used during vacuum pressure reduction. This is then sealed by being covered with a backing film  61 . 
         [0068]    In regard to  63 , the air inside the backing film  61  is taken up by a pressure reduction pipe  63 . In other words, air on the inside is removed and the pressure is reduced by the pressure reduction pipe  63 , so that pressure can be applied to the bonding sites between the upper skin  11  and the front spar  12  and rear spar  13 . 
         [0069]    As is shown in  FIG. 8 , the beam pressing jig  41  and the upper skin  11 , front spar  12  and rear spar  13  in which the bonding sites are covered by the backing film  61  ( FIG. 7 ) are placed inside an autoclave  65  together with the bonding cart  31 , and are pressed and heated; a pressure reduction is also performed inside the backing film  61  shown in  FIG. 7 , and the adhesive agent is cured. 
         [0070]    The heating temperature in this case (temperature of the bonding sites) is 120 to 180° C., the pressure is 2.8 to 3.2 kg/cm 2 , the curing time is 1 hour, the temperature elevation rate inside the autoclave  65  is 0.2 to 6.0° C./minute, and the pressure inside the backing film is −1.0 kg/cm 2 . A stable adhesive strength can be obtained by using these curing conditions. 
         [0071]    If the heating temperature is less than 120° C., the adhesive agent is unreacted, and curing tends not to proceed. If the heating temperature exceeds 180° C., the adhesive agent deteriorates. 
         [0072]    If the pressure is less than 2.8 kg/cm 2 , gaps tend to be generated between the upper skin  11  and the front spar  12  and rear spar  13 . If the pressure exceeds 3.2 kg/cm 2 , the adhesive agent flows out from between the upper skin  11  and the front spar  12  and rear spar  13 , and the thickness of the adhesive agent cannot be ensured. 
         [0073]    In cases where a large wing is bonded, thermal strain is generated in the temperature elevation process and temperature decrease process inside the autoclave  65 , and residual stress is generated in the bonding sites, thus causing cracking to occur. Accordingly, it is desirable to perform a heat treatment over a period of 4 to 8 hours as the curing time. 
         [0074]      FIGS. 9A ,  9 B and  9 C show a state in which the upper skin assembly (upper structure of the wing)  67  is positioned on the forming surface  71   a  of the assembly jig  71 . 
         [0075]    In  FIG. 9A , the upper skin  11 , front spar  12 , and rear spar  13  in which the curing of the bonding sites has been completed, and the beam pressing jig  41  ( FIG. 8 ), are removed from the autoclave  65  together with the bonding cart  31 , and the beam pressing jig  41  is removed from the upper skin assembly  67  comprising the upper skin  11 , front spar  12 , and rear spar  13 . Furthermore, the backing film  61  ( FIG. 7 ), release film, bleeder cloth, and breather cloth are stripped away, and the upper skin assembly  67  is placed and positioned on the forming surface  71   a  of the assembly jig  71 . 
         [0076]      FIG. 9B  shows the positioning of the wing tip side of the upper skin assembly  67  with respect to the assembly jig  71 . Specifically, positioned parts  12   h  and  13   h  formed on the wing tip sides of the front spar  12  and rear spar  13  are engaged with positioning pins  73 ,  73  disposed on the forming surface  71   a  of the assembly jig  71 . 
         [0077]      FIG. 9C  shows the positioning of the wing root side of the upper structure  67  of the wing with respect to the assembly jig  71 . Specifically, a positioning pipe frame  75  disposed on the bonding cart  31  ( FIG. 5 ) is left on the wing root ends of the front spar  12  and rear spar  13  ( FIG. 9B ), and positioning holes  75   a ,  75   a  (only one symbol  75   a  is shown) formed in the undersurface of this positioning pipe frame  75  are engaged with positioning pins  77 ,  77  disposed on the assembly jig  71 . 
         [0078]    The abovementioned positioning pins  73  and  77  constitute a third reference part that is used to position the upper skin assembly  67  on the assembly jig  71 . 
         [0079]      FIGS. 10A through 10C  show a state in which the ribs  14  are mounted inside the upper skin assembly  67 . 
         [0080]    As is shown in  FIG. 10A , the ribs  14  ( 14   k  indicates rivet holes formed beforehand) are inserted into the upper skin assembly  67  ( 11   k ,  12   k , and  13   k  indicate rivet holes formed beforehand). 
         [0081]    In  FIG. 10B , the ribs  14  are fastened to the upper skin assembly  67  by a plurality of rivets  21 ,  22 ,  23 . 
         [0082]    As is shown in  FIG. 10C , the lower skin  16  is finally fastened to the front spar  12 , rear spar  13 , and ribs  14  by a plurality of rivets  24 . With this, the assembly of the main wing structure  1  is completed. 
         [0083]    Next, the method for assembly the main wing structure  1  described above will be described with reference to the flow chart shown in  FIG. 11 . 
         [0084]    Step (hereafter abbreviated to “ST”)  01 : an anodizing treatment is performed as a surface treatment on the main wing assembly parts (upper skin, front spar, and rear spar). 
         [0085]    ST 02 : an adhesive primer is applied as a coating to the upper skin, front spar and rear spar. 
         [0086]    ST 03 : the upper skin is positioned on the bonding cart. 
         [0087]    ST 04 : a film-form adhesive agent is pasted to the front spar and rear spar. 
         [0088]    ST 05 : the front spar and rear spar are placed on the upper skin while being positioned. 
         [0089]    ST 06 : the beam pressing jig is fastened to the front spar and rear spar. 
         [0090]    ST 07 : the bonding sites are covered by a backing film or the like, and the bonding sites are sealed. 
         [0091]    ST 08 : the bonding sites are cured at a high temperature and high pressure inside an autoclave. 
         [0092]    ST 09 : the upper skin assembly removed from the autoclave is positioned on the assembly jig. 
         [0093]    ST 10 : a plurality of ribs is attached by rivets to the upper skin assembly. 
         [0094]    ST 11 : the lower skin is attached by rivets to the upper skin assembly and the plurality of ribs. 
         [0095]    As is shown in  FIGS. 2 through 10 , the present invention first of all comprises a first step of positioning the upper skin  11  on the bonding cart  31  on the basis of position pins  32 ,  32  and a plurality of positioning projections  33  used as reference parts which are disposed on the forming surface  31   a  of the bonding cart  31  used as a bonding jig, a second step of positioning and fastening the front spar  12  and rear spar  13  as a plurality of intermediate beams on the upper skin  11  via an adhesive agent on the basis of positioning pins  36 ,  36 ,  38 ,  38 , a third step of covering at least the bonding sites  18 ,  18  between the upper skin  11  and front spar  12  and rear spar  13  with a backing film  61 , and a fourth step of bonding the upper skin  11  and front spar  12  and rear spar  13  by pressing and heating the bonding sites  18 ,  18  inside an autoclave  65 , drawing the air out of the backing film  61 , and curing the adhesive agent. 
         [0096]    As a result, rivet fastening becomes unnecessary, so that the number of assembly processes such as rivet hole formation, rivet driving, and the like can be reduced. Furthermore, there is no concentration of stress, and the smoothness of the wing surfaces is improved, so that the drag of the aircraft can be reduced, and the aerodynamic performance can be improved. 
         [0097]    Moreover, welding defects such as solidification cracks, blow holes, and the like encountered in conventional welding do no occur, the mechanical strength can be improved, and a highly reliable aluminum alloy main wing can be manufactured. 
         [0098]    The present invention further includes a fifth step of separating the upper skin assembly  67  comprising the bonded upper skin  11 , front spar  12 , and rear spar  13  from the bonding cart  31  following the curing of the adhesive agent, a sixth step of positioning the upper skin assembly  67  on the assembly jig  71  on the basis of positioning pins  73 ,  73 ,  77 ,  77  disposed on the assembly jig  71 , a seventh step of disposing a plurality of ribs  14  in specified positions on this upper skin assembly  67 , and then fastening the upper skin assembly  67  and plurality of ribs  14  using rivets, and an eighth step of disposing the lower skin  16  in a specified position with respect to the upper skin assembly  67  to which the plurality of ribs  14  has been fastened by rivets, and then fastening the upper skin assembly  67  and ribs  14  to the lower skin  16  using rivets. 
         [0099]    As a result, since the lower skin  16  is fastened using rivets to the upper skin assembly  67 , the upper skin assembly  67  and lower skin  16  can be strongly fastened, and the rigidity of the main wing can be improved. 
         [0100]    In the present invention, when the abovementioned front spar  12  and rear spar  13  are positioned on and fastened to the abovementioned upper skin  11 , a beam pressing jig  41  is fastened to the upper parts of the front spar  12  and rear spar  13 , and the front spar  12  and rear spar  13  are held. 
         [0101]    As a result, deformation of the front spar  12  and rear spar  13  during the curing of the adhesive agent is prevented. 
         [0102]    In the present embodiment, two spars, i.e., the front spar  12  and rear spar  13  are disposed between the upper skin  11  and lower skin  16 , as shown in  FIG. 1 . However, the present invention is not limited to this. Another spar may be disposed between the front spar  12  and rear spar  13 , this spar may be adhesively bonded to the upper skin  11 , and this spar may be fastened to the lower skin  16  using rivets. 
         [0103]    Obviously, various minor changes and modifications of the present invention are possible in light of the above teaching. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.