Abstract:
An aircraft wing ( 104 ) comprises a rear spar ( 108 ), a first skin ( 110 ), a second skin ( 112 ) overhanging and converging to an opening ( 114 ) of width (A), a support structure ( 200 ) comprising a bracket ( 202 ) engaging the spar ( 108 ) and skins ( 110, 112 ) and a rib ( 216 ) engaging the bracket ( 202 ) via a rib attachment portion ( 218 ) with a dimension (C) less than dimension (A).

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a structure for mounting aircraft control surfaces. More specifically, the present invention relates to a cantilever rib for mounting a flap from a rear spar of a wing. 
       BACKGROUND OF THE INVENTION 
       [0002]    Control surfaces are used on aircraft to influence the passage of fluid over various flight surfaces such as wings. Flaps, for example, are a type of control surface which are mounted to the rear of a wing and can be rotated with respect to the wing trailing edge to change the shape of the aerofoil profile of the wing assembly as a whole. This helps prevent wing stall at low speeds (e.g. during landing) when the flaps are fully deployed, and increases efficiency of the wing at high speeds (e.g. during cruise) when the flaps are stowed. Slats are another type of control surface positioned at the leading edge of the wing. 
         [0003]    Both immovable and movable components (e.g. control surfaces such as flaps) need to be securely mounted to the aircraft. Flaps, for example, can be mounted to the wings of the aircraft in a variety of ways, for example via an underslung beam attached to the underside of the aircraft wing, or via a cantilever rib mounted directly to, and projecting perpendicularly from, a rear spar of the wing. 
         [0004]    Cantilever ribs are attached to the rear spar of an aircraft wing and are generally bolted directly to the wing skin overhanging the spar and to the spar itself. The wing skin overhanging at both the upper and lower surfaces of the wing trailing edge and the upper and lower skin surfaces tends to converge. As such the vertical distance between the upper and lower skin at the trailing edges is somewhat less than the distance between the skins proximate the spar, i.e. the position at which the rib needs to be attached. Consequently, the rib cannot fit between the skins without them being spread. 
         [0005]    As cantilever ribs are prone to damage (due to their exposed position on the aircraft), they need to be replaced frequently. On metal skinned aircraft this has been achieved by spreading the skins to increase the distance between their trailing edges. 
         [0006]    Metal components can be repeatedly deformed in this manner as they generally have a high yield strength and will return to their original shape once released. 
         [0007]    Composite (e.g. carbon reinforced plastic) components, which are now starting to be used for aircraft wing structures are more prone to damage following significant and/or repeated deformation such as spreading. As such, replacement of cantilever ribs in aircraft wings of this type is problematic. 
         [0008]    It is an aim of the invention to provide an improved aircraft structure. 
       SUMMARY OF THE INVENTION 
       [0009]    According to a first aspect of the invention there is provided an aircraft control surface support structure comprising a wing spar, a first panel overhanging a first side of the spar and a second panel overhanging a second side of the spar opposite the first side, in which the first and second panels converge to a first opening having a first width between respective edges of the first and second panels, the structure further comprising a bracket engaging the spar and the first and second panels proximate the spar such that the bracket is retained relative to the spar, and a rib comprising a rib mounting portion having a mounting means removably engaged with the bracket, which mounting portion has a first dimension sized to be equal to or less than the first width to permit passage of the first portion through the first opening to engage and disengage the bracket without rotation of the rib. 
         [0010]    Advantageously, the rib can therefore be replaced without deformation of the panels or skin of the aircraft wing. 
         [0011]    The bracket may be unitary. Alternatively the bracket may comprise a pair of sub brackets, the first sub bracket engaging the spar and the first panel and the second sub bracket engaging the spar and second panel. 
         [0012]    Preferably the structure comprises a further bracket, the bracket and the further bracket being positioned to define a receiving formation for the mounting portion. 
         [0013]    According to a second aspect of the invention there is provided an aircraft comprising a support structure according to the first aspect of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    An example structure will now be described with reference to the accompanying figures in which: 
           [0015]      FIG. 1  is a plan view of an aircraft, 
           [0016]      FIGS. 2   a  and  2   b  are side section views of a part of an aircraft along line II-II in  FIG. 1 , 
           [0017]      FIG. 3   a  is a side section view of a part of a first aircraft structure in accordance with the present invention, 
           [0018]      FIG. 3   b  is a plan section view of the structure of  FIG. 3   a,    
           [0019]      FIG. 3   c  is a side section view of the structure of  FIG. 3   a  during a replacement operation, 
           [0020]      FIG. 3   d  is a plan section view of the structure of  FIG. 3   a  during a replacement operation, 
           [0021]      FIG. 4   a  is a side section view of a part of a second aircraft structure in accordance with the present invention, 
           [0022]      FIG. 4   b  is a plan section view of the structure of  FIG. 4   a,    
           [0023]      FIG. 4   c  is a side section view of the structure of  FIG. 4   a  during a replacement operation, 
           [0024]      FIG. 4   d  is a plan section view of the structure of  FIG. 4   a  during a replacement operation, and, 
           [0025]      FIGS. 4   e  and  4   f  are perspective views of the aircraft structure of  FIG. 4   a.    
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0026]    Referring to  FIG. 1 , a passenger aircraft  100  comprises a fuselage  102  and wings  104 . The aircraft  100  defines a main longitudinal axis  101  parallel to the line of flight L. Each wing comprises at least one flap  106  which can be selectively deployed or stowed as known in the art. 
         [0027]    Referring to  FIGS. 2   a  and  2   b , each wing  104  comprises a rear spar  108  in addition to an upper skin  110  and a lower skin  112 . The upper and lower skins  110 ,  112  overhang the rear spar  108  and converge to an opening  114  of height A. The height A is defined as the vertical distance between the skin rear edges. It will be noted that at the point at which the skins  110 ,  112  meet the spar  108  they are distance B apart, where B is greater than A (due to the convergence of the skins). 
         [0028]    A cantilever rib  116  is mounted to the rear spar  108  and skins  110 ,  112  to mount the flap  106  (shown in  FIG. 1 ) about a pivot axis X. The cantilever rib  116  is unitary and comprises a downwardly depending arm  118  at a first end of which the pivot axis X is defined. At a second end of the arm  118  an attachment structure  120  is defined comprising a pair of horizontal flanges  122 ,  124  and a vertical flange  126 . The attachment structure  120  is shaped to nestle between the skins  110 ,  112  and the spar  108  with the horizontal flanges  122 ,  124  bolted to the skins  110 ,  112  respectively and the vertical flange  126  bolted to the spar  108 . 
         [0029]    It will be noted therefore that the vertical flange  126  is approximately equal to B in height in order to securely fit between the skins  110 ,  112 . Referring to  FIG. 2   b  the skins  110 ,  112  have to be spread in directions Y and Z respectively in order to open the opening  114  to a height equal to B in order to remove the rib  116  in removal direction R. 
         [0030]    The rib  116  is an interchangeable component and has to be frequently replaced in use due to wear and/or damage and as such the skins  110 ,  112  have to be repeatedly deformed. This is a problem as repeated deformation can cause damage to the skins  110 ,  112  and if they are plastically deformed this may affect the aerodynamic characteristics of the wing  104 . This is a serious problem if the skins  110 ,  112  are composite as composites generally have a lower yield stress than metals and are less easy to deform back to their original shape should they be damaged. 
         [0031]      FIGS. 3   a  to  3   d  show a cantilever rib structure  200  in accordance with the present invention. Aircraft components common with  FIGS. 1 to 2   d  are numbered identically. 
         [0032]    The structure  200  comprises a first bracket  202  and a second bracket  204 . The brackets  202 ,  204  are identical, although oppositely orientated and as such only the bracket  202  will be described in detail. The bracket  202  is generally prismatic, L shaped in cross section and comprises top and bottom flanges  206 ,  208  respectively. The L-shaped section comprises a rear flange  210  and a projecting flange  212  each making a leg of the “L”. 
         [0033]    The flanges  206 ,  208 ,  210  each define bores (not shown) for receiving bolts for attachment to the wing  104  as will be described below. The flange  212  defines bores  214  for receiving bolts as will be described below. 
         [0034]    The structure comprises a cantilever rib  216  formed from a plate comprising stiffening ribs (not shown). The rib  216  comprises an attachment region  218  defining a plurality of bores  220 . 
         [0035]    The brackets  202 ,  204  are bolted to the spar  108  and the skins  110 ,  112  to retain the brackets  202 ,  204  relative thereto. The brackets  202 ,  204  are positioned with a rib receiving gap  222  defined therebetween. The brackets  202 ,  204  only need to be installed once (they are not interchangeable) and as such may be installed at the same time as the wing  104  is assembled, thus eliminating the need to spread the skins  110 ,  112  at all. Alternatively, the brackets  202 ,  204  may be retrofitted by spreading the skins  110 ,  112  but as the brackets  202 ,  204  will not need to be removed the skins  110 ,  112  will only need to be spread once. 
         [0036]    Once the brackets  202 ,  204  are installed, the attachment region  218  of the rib  216  is inserted into the gap  222  and the rib  216  is bolted in place through bores  214 ,  220 . The rib  216  can be replaced by removing the bolts and removing the rib  216  in direction R. It will be noted that the height of the attachment portion of the rib, C, is equal to or less than the height A of the gap  114 . Therefore the rib  216  can be easily removed from the gap  114  and replaced without the skins  110 ,  112  being spread. 
         [0037]      FIGS. 4   a  to  4   f  show a cantilever rib structure  300  in accordance with the present invention. Aircraft components common with  FIGS. 1 to 2   d  are numbered identically. 
         [0038]    Structure  300  is similar to the rib structure  200 . Only the differences will be described. The structure  300  comprises a first component bracket  302  and a second component bracket  304 . The brackets  302 ,  304  are identical, although oppositely orientated and as such only the bracket  302  will be described in detail. 
         [0039]    The component bracket  302  comprises a first sub bracket  306  and a second sub bracket  308 . The sub brackets represent the end sections of the bracket  202  (i.e. as if a centre portion of the bracket  202  had been removed). They each define bores  309 . 
         [0040]    A cantilever rib  310  is similar to the cantilever rib  216  with the exception that a cut-out  312  is provided in an attachment region  314 . The attachment region  314  therefore comprises two lugs  316 ,  318  each with bores defined therethrough for the attachment of the rib  310  to the component bracket  302 . 
         [0041]    Advantageously, the component brackets  302 ,  304  can be installed to the assembled wing  104  without having to spread the skins  110 ,  112 . 
         [0042]    Referring to  FIGS. 4   e  and  4   d  the arrangement of the brackets  302 ,  304  can be seen in more detail. The rib  310  comprises stiffening ribs  320   
         [0043]    Variations of the above embodiment fall within the scope of the present invention. 
         [0044]    The bracket may comprise a single component to which the rib attaches on one side only. 
         [0045]    The bracket may be positioned to mount a component (e.g. a control surface) to a leading edge of a wing. 
         [0046]    The component bracket may comprise a further sub bracket disposed between the two sub brackets  306 ,  308 . 
         [0047]    The brackets  202 ,  204  may be orientated with their projecting flanges  212  projecting non-perpendicularly from the spar  108  to allow the rib  216  to project at any desired angle when installed. For example, the rib  216  may be installed to project parallel to the line of flight L of the aircraft  100  thus reducing the drag produced by the rib&#39;s projection from the outer mean line (OML) of the aircraft.