Patent Publication Number: US-2023140102-A1

Title: Structural arrangement and method for counteracting a vertical moment of a strut-braced wing

Description:
FIELD 
     The present disclosure relates generally to aircraft structures and, more particularly, to a structural arrangement for counteracting a vertical moment generated by a strut-braced wing. 
     BACKGROUND 
     The use of struts to support the wings of an aircraft can significantly reduce the spanwise bending moment in the wings. Struts are typically attached to a lower portion of the fuselage, and extend up to the wings at an angle. Aircraft that operate at high cruise speeds typically have swept wings to reduce shock waves and wave drag. The aerodynamic performance of an aircraft can be improved by increasing the aspect ratio of the wings. 
     When struts are implemented on a swept-wing aircraft with high-aspect-ratio wings, the strut-fuselage joint (where the strut attaches to the fuselage) is located aft of the wing-fuselage joint (where the wing attaches to the fuselage). As a result of the aft offset of the strut-fuselage joint relative to the wing-fuselage joint, the lower portion of the struts are non-overlapped by the wings when the aircraft is viewed from above. The non-stacked or non-overlapping relation of the wings and struts reduces interference drag, which significantly improves the aerodynamic performance of the aircraft. 
     However, the aft offset of the strut-fuselage joint results in a relatively large moment about a vertical axis on the wings and struts. More specifically, the lifting force generated by each wing is reacted by tension load in the strut that supports the wing. Due to the aft offset of the strut-fuselage joint, the tension load in the strut induces a large bending moment about the vertical axis at the wing root and strut root, referred to as a vertical moment. The large vertical moment has the undesirable effect of urging the wings to pivot in an aft direction. 
     As can be seen, there exists a need in the art for a structural arrangement for a strut-braced, swept-wing aircraft that is capable of counteracting a large vertical moment in a structurally efficient manner. 
     SUMMARY 
     The above-noted needs associated with structural arrangements for strut-braced, swept-wing aircraft is addressed by the present disclosure, which includes an aircraft having a fuselage, and a pair of wings. Each wing is coupled to the fuselage at a wing-fuselage joint, and is supported by a strut coupled to the fuselage at a strut-fuselage joint and coupled to the wing at a strut-wing joint. The strut-fuselage joint is located below and at least partially aft of the wing-fuselage joint. The wing generates a lifting force when air passes over the wing. The lifting force induces a vertical moment about the wing-fuselage joint due to the location of the strut-fuselage joint below and at least partially aft of the wing-fuselage joint. The wing and/or the strut has a structural arrangement configured to counteract the vertical moment. 
     Also disclosed is an aircraft, comprising a fuselage, a wing, and a strut. The wing is coupled to the fuselage at a wing-fuselage joint, and has a wing trailing edge. The strut is coupled to the fuselage at a strut-fuselage joint and is coupled to the wing at a strut-wing joint. The strut-fuselage joint is located below and at least partially aft of the wing-fuselage joint. The strut has a strut leading edge, a portion of which is located aft of the wing trailing edge when the aircraft is viewed from a top-down perspective. The wing generates a lifting force when air passes over the wing. The lifting force induces a vertical moment about the wing-fuselage joint due to the location of the strut-fuselage joint below and at least partially aft of the wing-fuselage joint. At least one of the wing and the strut has a structural arrangement configured to counteract the vertical moment. 
     Additionally, disclosed is a method of enhancing the performance of an aircraft. The method includes generating a lifting force when air passes over a wing of the aircraft. The wing is coupled to a fuselage at a wing-fuselage joint, and is supported by a strut coupled to the fuselage at a strut-fuselage joint located below and at least partially aft of the wing-fuselage joint. The method additionally includes inducing a vertical moment about the wing-fuselage joint in response to the lifting force. The method also includes counteracting the vertical moment using a structural arrangement of at least one of the wing and the strut. 
     The features, functions and advantages that have been discussed can be achieved independently in various examples of the present disclosure or may be combined in yet other examples, further details of which can be seen with reference to the following description and drawings below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features of the present disclosure will become more apparent upon reference to the drawings wherein like numbers refer to like parts throughout and wherein: 
         FIG.  1    is a top perspective view of an example of a strut-braced, swept-wing aircraft; 
         FIG.  2    is a bottom perspective view of the aircraft of  FIG.  1   ; 
         FIG.  3    is a front view of the aircraft of  FIG.  1   ; 
         FIG.  4    is a side view of the aircraft of  FIG.  1   ; 
         FIG.  5    is a front view of one-half of the aircraft of  FIG.  1   , illustrating a wing of the aircraft coupled to the fuselage at a wing-fuselage joint, and further illustrating a strut coupled to the fuselage at a strut-fuselage joint, and coupled to the wing at a strut-wing joint; 
         FIG.  6    is a top view of the aircraft of  FIG.  5   , and illustrating the strut-fuselage joint located aft of the wing-fuselage joint; 
         FIG.  7    is a diagrammatic sectional view of a vertically stacked configuration of a wing and a strut; 
         FIG.  8    is a diagrammatic sectional view taken along line  8 - 8  of  FIG.  6   , and illustrating an unstacked configuration of a wing and strut; 
         FIG.  9    is a top-aft perspective view of a portion of the aircraft of  FIG.  6   , and illustrating a wing axis extending from the wing-fuselage joint to the strut-wing joint, and a strut axis extending from the strut-fuselage joint to the strut-wing joint, and further illustrating a distributed air pressure representative of lifting force generated by the wing; 
         FIG.  10    is a top view of the aircraft of  FIG.  9   ; 
         FIG.  11    is a front view of the aircraft of  FIG.  9     
         FIG.  12    is a side view of the aircraft of  FIG.  9   ; 
         FIG.  13    is a schematic diagram of the wing and the strut in the same orientation as the top-aft perspective view of  FIG.  9   ; 
         FIG.  14    is a schematic diagram of the wing and the strut in the same orientation as the top view of  FIG.  10   ; 
         FIG.  15    is a schematic diagram of the wing and the strut in the same orientation as the front view of  FIG.  11   ; 
         FIG.  16    is a schematic diagram of the wing and the strut in the same orientation as the side view of  FIG.  12   ; 
         FIG.  17    is a schematic diagram of the wing and the strut of  FIG.  9   , and showing a vertical load vector at the strut-wing joint representing the above-mentioned vertical lifting force distributed over the wing (e.g.,  FIG.  9   ), and also showing reactions respectively at the wing-fuselage joint and the strut-fuselage joint, and further showing a vertical moment resulting from the lifting force about the wing-fuselage joint due to the location of the strut-fuselage joint aft of the wing-fuselage joint; 
         FIG.  18    is a schematic diagram of the wing and the strut of  FIG.  14   , and showing the reaction forces and the vertical moment of  FIG.  17   ; 
         FIG.  19    is a schematic diagram of the wing and the strut of  FIG.  15   , and showing the reaction forces and the vertical moment of  FIG.  17   ; 
         FIG.  20    is a schematic diagram of the wing and the strut of  FIG.  60   , and showing the reaction forces and the vertical moment of  FIG.  17   ; 
         FIG.  21    is a top-aft perspective view schematic diagram of the wing and the strut, and showing the strut as a cantilevered beam fixedly coupled to the fuselage at the strut-fuselage joint; 
         FIG.  22    is a top view schematic diagram of the wing and the strut of  FIG.  21   ; 
         FIG.  23    is a schematic diagram of the wing and the strut of  FIG.  21   , and showing the vertical load vector at the strut-wing joint representing the lifting force distributed over the wing, and the reaction forces respectively at the wing-fuselage joint and the strut-fuselage joint, and the vertical moment reacted by the strut configured as a cantilevered beam; 
         FIG.  24    is a top view schematic diagram of  FIG.  23    showing the reaction forces and the vertical moment; 
         FIG.  25    is a top-aft perspective view schematic diagram of the wing and the strut, and showing the wing as a cantilevered beam fixedly coupled to the fuselage at the wing-fuselage joint; 
         FIG.  26    is a top view schematic diagram of the wing and the strut of  FIG.  25   ; 
         FIG.  27    is a schematic diagram of the wing and the strut of  FIG.  25   , and showing the lifting force at the strut-wing joint, and the reaction forces respectively at the wing-fuselage joint and the strut-fuselage joint, and the vertical moment reacted by the wing configured as a cantilevered beam; 
         FIG.  28    is a top view schematic diagram of  FIG.  27    showing the reaction forces and the vertical moment; 
         FIG.  29    is a top-aft perspective view schematic diagram of the wing and the strut showing both the wing and the strut as cantilevered beams, each fixedly coupled to the fuselage; 
         FIG.  30    is a top view schematic diagram of  FIG.  29   ; 
         FIG.  31    is a schematic diagram of the wing and the strut of  FIG.  29   , and showing the vertical load vector at the strut-wing joint representing the distributed air pressure (e.g.,  FIG.  9   ) over the wing area, and additionally showing the reaction forces respectively at the wing-fuselage joint and the strut-fuselage joint, and the vertical moment resisted by the wing at the wing-fuselage joint, and the vertical moment resisted by the strut at the strut-fuselage joint; 
         FIG.  32    is a top view diagram of  FIG.  31   , showing the reaction forces and the vertical moments reacted at the wing-fuselage joint and the strut-fuselage joint; 
         FIG.  33    is a top-aft perspective view of the aircraft, and illustrating a strut A-frame structure comprising a strut front spar and a strut rear spar, and defining a lower tetrahedral structure, and also showing the above-mentioned vertical load vector representing the lifting force distributed over the wing; 
         FIG.  34    is a top view of the aircraft of  FIG.  33   ; 
         FIG.  35    is a schematic diagram of the wing and the strut of  FIG.  33   , and showing the strut configured as a strut A-frame structure in which the strut spar inboard ends of the strut front spar and the strut rear spar are spaced apart from each other; 
         FIG.  36    is a top view schematic diagram of  FIG.  35   ; 
         FIG.  37    is a schematic diagram of the wing and the strut of  FIG.  35   , and showing the lifting force at the strut-wing joint, and the reaction forces at the wing-fuselage joint, and at the strut-fuselage joint; 
         FIG.  38    is a top view schematic diagram of  FIG.  37   ; 
         FIG.  39    is a magnified top view of a portion of the schematic diagram of  FIG.  37   , showing the reaction forces at the wing-fuselage joint, and at the strut-fuselage joint; 
         FIG.  40    shows the reaction forces of  FIG.  39   , and further illustrates the reaction forces at an inboard end connector coupling the strut front spar and the strut rear spar to the fuselage; 
         FIG.  41    is a chart of the reaction forces at the strut front and rear attach points for four different arrangements of the strut having different attach point spacings; 
         FIG.  42    is a top view of the strut having a tapered shape; 
         FIG.  43    is a sectional view taken along line  43 - 43  of  FIG.  42   , illustrating an airfoil shape of the strut containing the strut front spar and the strut rear spar; 
         FIG.  44    is a plot of the aerodynamic penalty and the structural penalty as a function of the aft offset between the strut-fuselage joint and the wing-fuselage joint shown in  FIG.  46    for the lower tetrahedron structure defined by the wing axis and the strut A-frame structure; 
         FIG.  45    is a plot of the structural benefit as a function of the attach point spacing between the strut front spar and the strut rear spar at the strut-fuselage joint for the lower tetrahedron structure of  FIG.  46   ; 
         FIG.  46    is a schematic diagram of the wing and the strut A-frame structure, forming a lower tetrahedron structure; 
         FIG.  47    is a top-aft perspective view of the aircraft, and illustrating the wing having wing A-frame structure, and defining an upper tetrahedron structure; 
         FIG.  48    is a top view of the aircraft of  FIG.  47   ; 
         FIG.  49    is a schematic diagram of the wing and the strut of  FIG.  47    and illustrating the wing A-frame structure comprising a wing front member and a wing rear member; 
         FIG.  50    is a top view schematic diagram of  FIG.  49   ; 
         FIG.  51    is a top-aft perspective view of the aircraft, and showing the wing having a wing A-frame structure, and the strut having a strut A-frame structure, and defining a pyramid configuration; 
         FIG.  52    is a top view of the aircraft of  FIG.  51   ; 
         FIG.  53    is a top-aft schematic diagram of the pyramid configuration of  FIG.  51   ; 
         FIG.  54    is a top schematic diagram of the pyramid configuration of  FIG.  51   ; 
         FIG.  55    is a front view of one-half of the aircraft; 
         FIG.  56    are plots of structural weight due to wing bending moment, as a function of wing span, for a typical cantilevered wing and for a strut-based wing; 
         FIG.  57    is a plot of structural weight due to vertical moment, as a function of wing span; 
       Figure the  58  shows the cut of  FIG.  56    superimposed on the plot of  FIG.  57   ; 
         FIG.  59    is a top view of the aircraft showing the strut spar leading edge located aft of the wing trailing edge; 
         FIG.  60    is a schematic diagram of a strut A-frame structure; 
         FIG.  61    is a sectional view taken along line  61 - 61  of  FIG.  60   , showing an attach point spacing between a strut front attach point aligned with the strut front spar, and a strut rear attach point aligned with the strut rear spar; 
         FIG.  62    is a diagram of the strut bending moment as a function of strut length from the strut-fuselage joint to the strut-wing joint; 
         FIG.  63    is a schematic diagram of a strut A-frame structure in which the strut front attach point and strut rear attach point are located respectively forward and aft of the strut inboard ends of the strut front spar and the strut rear spar; 
         FIG.  64    is a sectional view taken along line  64 - 64  of  FIG.  63   , showing the increased attach point spacing between the strut front attach point and the strut rear attach point; 
         FIG.  65    is a schematic diagram of an example of a strut having a kink in the strut front spar and the strut rear spar as a means to increase the attach point spacing between the strut front attach point and the strut rear attach point; 
         FIG.  66    is a sectional view taken along line  66 - 66  of  FIG.  65   , showing a kink plate interconnecting a strut spar inboard section of each of the strut front spar and the strut rear spar; 
         FIG.  67    is a schematic diagram of an example of a strut having a strut leading edge and a strut trailing edge defining the strut leading edge and the strut trailing edge of the strut; 
         FIG.  68    is a sectional view taken along line  68 - 68  of  FIG.  67   , showing the strut leading edge member and the strut trailing edge member for counteracting the vertical moment at the strut-fuselage joint; 
         FIG.  69    is a schematic diagram of an example of a strut in which the strut front spar and the strut rear spar each have a curved shape complementary to the curved shape of the strut leading edge and the strut trailing edge; 
         FIG.  70    is a sectional view taken along line  70 - 70  of  FIG.  69   , and illustrating an example of the strut front spar and the strut rear spar each having a channel-shaped cross-section; 
         FIG.  71    is a magnified view of the portion of the strut identified by reference numeral  71  of  FIG.  70   , and illustrating reinforcing fibers embedded within or bonded to the strut front spar and extending along a lengthwise direction of the strut front spar; 
         FIG.  72    is a schematic diagram of an example of a strut having a strut front fitting and a strut rear fitting for increasing the attach point spacing between the strut front attach point and the strut rear attach point; 
         FIG.  73    is a sectional view taken along line  73 - 73  of  FIG.  72   , and illustrating the strut front fitting and the strut rear fitting respectively coupled to the strut front spar and the strut rear spar; 
         FIG.  74    is a schematic diagram of an example of a strut having skin stiffeners coupled to a strut upper skin panel and a strut lower skin panel; 
         FIG.  75    is a sectional view taken along line  75 - 75  of  FIG.  74   , and showing the strut front fitting and the strut rear fitting respectively coupled to the spar web of the strut front spar and the strut rear spar; 
         FIG.  76    is a magnified view of the portion of the strut identified by reference numeral  76  of  FIG.  72   , illustrating an example of the strut front fitting nested within an upper cap, a lower cap, and a spar web of the strut front spar; 
         FIG.  77    is a schematic diagram of an example of a strut having a lug plate interconnecting the strut front spar and the strut rear spar; 
         FIG.  78    is a sectional view taken along line  78 - 78  of  FIG.  74   , and illustrating the lug plate interconnected to the strut front spar and the strut rear spar, and further illustrating strut lugs protruding from the lug plate for coupling to the fuselage at the strut-fuselage joint; 
         FIG.  79    is a magnified view of the portion of the strut identified by reference numeral  79  of  FIG.  78   , and illustrating the lug plate coupled to the strut front spar via a plurality of angle brackets; 
         FIG.  80    is a schematic view of an example of a pinned joint coupling the strut to the fuselage or to a pylon (not shown) connected to the fuselage; 
         FIG.  81    is a front view of an example of the aircraft showing a buckling mode of the strut attached to the fuselage via the pinned joint of  FIG.  80   ; 
         FIG.  82    is a schematic view of an example of a fixed joint coupling the strut to the fuselage; 
         FIG.  83    is a front view of the aircraft showing the buckling mode of the strut attached to the fuselage via the fixed joint of  FIG.  82   ; 
         FIG.  84    is a magnified view of the portion of the pinned joint identified by reference numeral  84  of  FIG.  81   , and illustrating a plurality of strut lugs rotatably coupled to a plurality of fuselage lugs via pins at the strut-fuselage joint; 
         FIG.  85    is a top view of the strut-fuselage joint of  FIG.  84   ; 
         FIG.  86    is a top view of an example of the pinned-joint of  FIG.  84   , and illustrating a net tension load exerted on the strut as a result of a lifting force generated by the wing; 
         FIG.  87    is an axial load profile of the tension load on the strut lugs at the strut front attach point and the strut rear attach point; 
         FIG.  88    shows the pinned-joint of the strut of  FIG.  84   , and illustrating a strut moment exerted on the strut as a result of the lifting force generated by the wing; 
         FIG.  89    is a moment profile of the moment at the strut front attach point and the strut rear attach point; 
         FIG.  90    is a top view of an example of a pinned joint showing additional angle brackets coupling the lug plate to the strut front spar to accommodate the increased axial load and moment at the strut front attach point; 
         FIG.  91    is a magnified view of the portion of the fixed joint identified by reference numeral  91  of  FIG.  83   , and illustrating a plurality of mechanical fasteners coupling a strut end plate to the fuselage; 
         FIG.  92    is a top view of the fixed joint of  FIG.  91    illustrating the reaction moment at the strut-fuselage joint; 
         FIG.  93    is a front view of an example of the aircraft having a jury strut extending between the strut and the wing proximate the strut-wing joint; 
         FIG.  94    is a magnified view of the portion of the strut-wing joint of  FIG.  93   , and illustrating a pinned connection coupling strut lugs of the strut to the wing lugs of the wing; 
         FIG.  95    is a top-down view taken along line  95 - 95  of  FIG.  94   , and illustrating the strut-wing joint comprising a plurality of strut lugs coupled to a front spar plate and a rear spar plate respectively of the strut front spar and the strut rear spar; 
         FIG.  96    is a front view of an example of the front spar plate and the rear spar plate coupled to the strut front spar and the strut rear spar; 
         FIG.  97    is a top view of the front spar plate and the rear spar plate coupled to the strut front spar and the strut rear spar; 
         FIG.  98    is a front view of the front spar plate coupled to the strut front spar via angle brackets; 
         FIG.  99    is a top-down view of the front spar plate and the strut front spar; 
         FIG.  100    is a front view of the strut front spar having a spar slot for receiving the front spar plate; 
         FIG.  101    is a sectional view taken along line  101 - 101  of  FIG.  97   , illustrating the coupling of the front spar plate to the strut front spar via angle brackets; 
         FIG.  102    is a front view of the rear spar plate coupled to the strut rear spar via angle brackets; 
         FIG.  103    is a top-down view of the rear spar plate and the strut rear spar; 
         FIG.  104    is a front view of the strut rear spar having a spar slot for receiving the rear spar plate; 
         FIG.  105    is a sectional view taken along line  105 - 105  of  FIG.  102   , illustrating the coupling of the rear spar plate to the strut rear spar via angle brackets; 
         FIG.  106    is a front view of an example of the strut-wing joint having a spar plate doubler for distributing the axial load from the strut front spar and strut rear spar respectively to the front spar plate and the rear spar plate; 
         FIG.  107    is a top view of the strut-wing joint of  FIG.  106   ; 
         FIG.  108    is a front view of the strut front spar having a spar slot for receiving the spar doubler plate of  FIG.  106   ; 
         FIG.  109    is a front view of the aircraft showing the buckling of the strut, and the stabilization provided by the jury strut; 
         FIG.  110    is a view of the strut taken along line  110 - 110  of  FIG.  109   , and illustrating the jury strut attached to the strut proximate the strut front spar; 
         FIG.  111    is a diagrammatic view of the strut showing the reaction force provided by the jury strut acting at the strut front spar to resist buckling of the spar; 
         FIG.  112    is a view of an example of a strut in which the jury strut extends between the strut front spar and the strut rear spar; 
         FIG.  113    is a diagrammatic view of the strut showing improved torsional buckling load-carrying capability of the strut, as a result of the jury strut extending between the strut front spar and the strut rear spar; 
         FIG.  114    is a front view of the aircraft showing the wings attached to the fuselage at the wing-fuselage joint and illustrating each wing having a wing upper skin panel and a wing lower skin panel; 
         FIG.  115    is a top-down view of the wing-fuselage joint taken along line  115 - 115  of  FIG.  114   , and illustrating each wing having a wing box comprised of a wing upper skin panel, a wing lower skin panel, a wing front spar, and a wing rear spar, and coupled to a wing shear plate; 
         FIG.  116    is a front view of the wing-fuselage joint of  FIG.  115   , showing the pinned joint for interconnecting the wing shear plate respectively of each wing; 
         FIG.  117    is a flowchart of operations included in a method of enhancing the operation of an aircraft by counteracting vertical moment induced by lifting force generated by the wings. 
     
    
    
     DETAILED DESCRIPTION 
     Disclosed versions will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all of the disclosed versions are shown. Indeed, several different versions may be provided and should not be construed as limited to the versions set forth herein. Rather, these versions are provided so that this disclosure will be thorough and fully convey the scope of the disclosure to those skilled in the art. 
     This specification includes references to “one version” or “a version.” Instances of the phrases “one version” or “a version” do not necessarily refer to the same version. Similarly, this specification includes references to “one example” or “an example.” Instances of the phrases “one example” or “an example” do not necessarily refer to the same example. Particular features, structures, or characteristics may be combined in any suitable manner consistent with this disclosure. 
     As used herein, “comprising” is an open-ended term, and as used in the claims, this term does not foreclose additional structures or steps. 
     As used herein, “configured to” means various parts or components may be described or claimed as “configured to” perform a task or tasks. In such contexts, “configured to” is used to connote structure by indicating that the parts or components include structure that performs those task or tasks during operation. As such, the parts or components can be said to be configured to perform the task even when the specified part or component is not currently operational (e.g., is not on). 
     As used herein, an element or step recited in the singular and preceded by the word “a” or “an” should be understood as not necessarily excluding the plural of the elements or steps. 
     As used herein, the phrase “at least one of,” when used with a list of items, means different combinations of one or more of the listed items may be used, and only one of each item in the list may be needed. In other words, “at least one of” means any combination of items and number of items may be used from the list, but not all of the items in the list are required. The item may be a particular object, a thing, or a category. 
     Referring now to the drawings which illustrate preferred and various examples of the disclosure, shown in  FIGS.  1 - 6    is a strut-braced, high-wing aircraft  100 . The aircraft  100  has a fuselage  102  having a fuselage upper portion  104  and a fuselage lower portion  106 . The fuselage  102  has a nose and a tail section, and a longitudinal axis  126  ( FIG.  4   ) extending between the nose and the tail section. In the example shown, the tail section includes a vertical tail  122  and a pair of horizontal tails  124  mounted on top of the vertical tail  122 . However, the vertical tail  122  and horizontal tails  124  may be arranged in alternative configurations. 
     The aircraft  100  includes a pair of wings  200 , and a pair of engines  120  suspended from the wings  200 . However, the engines may be mounted at alternative locations on the aircraft  100 . For example, the engines  120  may be mounted on the fuselage  102 , such as on an aft portion (not shown) of the fuselage  102 . Each wing  200  has a wing leading edge  214 , a wing trailing edge  216 , a wing root  202 , and a wingtip  210 . The wingspan of the aircraft  100  is measured between the wingtips  210 . Each wing root  202  is coupled to the fuselage  102  at a wing-fuselage joint  204  at the fuselage upper portion  104 . In the example shown, the wing-fuselage joint  204  for each wing  200  is covered by a wing root fairing  206 . Each wing  200  is swept aftwardly, and each wing  200  is a high-aspect-ratio wing, having a relatively long span and a relatively short chord. In the example shown, each wing  200  is swept at an angle of up to 25 degrees relative to a lateral axis (not shown), which is perpendicular to the longitudinal axis  126  ( FIG.  4   ). In other examples, each wing  200  may be swept at an angle of between 10-25 degrees. 
     In  FIG.  5   , each wing  200  has less than 10 degrees of anhedral, such that each wing  200  is slightly downwardly angled. However, in other examples, the wings  200  may have no anhedral, or the wings  200  may have dihedral, wherein the wings  200  are angled upwardly. In the example shown, the aircraft  100  is configured for transonic airspeeds, wherein the aircraft  100  may have a free stream Mach number of between 0.7-1.0. However, the presently-disclosed structural arrangements may be implemented on aircraft configured for subsonic speeds, and/or on aircraft configured for supersonic speeds. 
     Referring still to  FIGS.  1 - 6   , on each side of the aircraft  100  is a strut  300 . Each strut  300  has a strut leading edge  314 , a strut trailing edge  316 , a strut root  302 , and a strut outboard end  310 . The strut root  302  is coupled to the fuselage  102  at a strut-fuselage joint  304  at the fuselage lower portion  106 . In the example shown, the aircraft  100  includes a fuselage stub  108  protruding laterally from each side of the fuselage  102 . The strut root  302  is coupled to the fuselage stub  108  at the strut-fuselage joint  304 . The strut-fuselage joint  304  is covered by a strut root fairing  308 . 
     Each strut  300  extends at an upward angle from the strut-fuselage joint  304 , and is coupled to the wing  200  at a strut-wing joint  306 . Although not shown, the strut-wing joint  306  may be covered by a strut-wing-joint fairing. In the example shown, each strut-wing joint  306  is located at a distance of 40-70 percent of the distance from the wing root  202  to the wingtip  210 . 
     Notably, each strut-fuselage joint  304  is located at least partially aft of the wing-fuselage joint  204  when the aircraft  100  is viewed from the side, as shown in  FIG.  12   , or when viewed from the top, as shown in  FIG.  6   . When viewed from a top-down perspective (e.g.,  FIG.  6  or  10   ), the wing  200  and the strut  300  may be described as having a vertically unstacked arrangement, as opposed to a stacked arrangement (not shown) in which the wing  200  is vertically stacked directly above the strut  300 .  FIG.  7    is a schematic sectional view of an example of a wing  200  and a strut  300  in a vertically stacked arrangement.  FIG.  8    is a schematic sectional view taken along line  8 - 8  of  FIG.  6   , illustrating an unstacked arrangement of the wing  200  and strut  300 . As a result of the unstacked arrangement, when the aircraft  100  is viewed from a top-down perspective, at least a portion of the strut leading edge  314  is aft of the wing trailing edge  216 . More specifically, at locations proximate the strut root  302 , the strut leading edge  314  is located aft of the wing trailing edge  216 . In the present disclosure, the strut-fuselage joint  304  is defined as being located aft of the wing-fuselage joint  204  if the strut leading edge  314  at the strut root  302  is located aft of the wing front spar  220  at the wing root  202 , although the aerodynamics are unfavorable if the strut leading edge  314  is located forward of the wing trailing edge  216 . 
     Advantageously, the unstacked arrangement of the wing-fuselage joint  204  and the strut-fuselage joint  304  allows each strut  300  (at least an inboard portion of the strut  300 —e.g.,  FIG.  6   ) to contribute to lift and thereby enhance aircraft performance, while reducing loading on the wing  200 . In contrast, for a vertically stacked arrangement (not shown) of the wing-fuselage joint  204  and strut-fuselage joint  304 , low-pressure flow coming off each strut  300  acts on the underside of the wing  200 , reducing pressure and diminishing the lift contribution of the wing  200 . An additional benefit of the unstacked arrangement is a reduction in drag that would otherwise occur in the stacked arrangement due to strong shocks from high local flow Mach numbers caused by flow interference between the strut  300  and the wing  200 . 
     Referring to  FIGS.  9 - 12   , shown respectively are perspective, top, front, and side views of a portion (e.g., one-half) of the aircraft  100  of  FIGS.  1 - 6   . Shown in each view is a wing axis  212  extending between the wing-fuselage joint  204  and the strut-wing joint  306 . Also shown is a strut axis  312  extending between the strut-fuselage joint  304  and the strut-wing joint  306 . The wing  200  generates a lifting force  600 , which is distributed along the wingspan. The lifting force  600  is the vertical force supporting the mass of the aircraft  100  during flight, and is generated by the wing  200  when air passes over the wing  200 . 
     Referring to  FIGS.  13 - 15   , shown are schematic diagrams respectively corresponding to  FIGS.  9 - 12   .  FIGS.  13 - 15    schematically illustrate the wing  200  and the wing axis  212 , and the strut  300  and the strut axis  312 . Also shown in  FIGS.  13 - 15    and subsequent schematic diagrams is a reference coordinate system  128 , to aid in identifying the orientation of each drawing figure. In addition, the wing-fuselage joint  204  is identified by reference character A, the strut-wing joint  306  is identified by reference character B, and the strut-fuselage joint  304  is identified by reference character C. Furthermore, shown is wing-joint/strut-joint axis  250  extending the wing-fuselage joint  204  and the strut-fuselage joint  304 . 
     Referring to  FIGS.  17 - 20   , shown are schematic diagrams respectively similar to  FIGS.  13 - 16   , but without the aircraft  100 .  FIGS.  17 ,  19  and  20    schematically illustrate the lifting force  600  applied to the strut-wing joint  306 . The lifting force  600  is shown as a vertical load vector at the strut-wing joint  306 , and represents the typical summation of spanwise distribution of lift along the wingspan that is carried by the strut  300 , as shown in  FIGS.  9 ,  11  and  12   . A typically smaller portion of the wing spanwise distribution of lift is also transmitted by the wing  200  to the wing-fuselage joint  204 , and which does not contribute to a vertical moment M z  caused by the unstacked arrangement of the wing  200  and strut  300 . 
     As described herein, the vertical moment M z  is due to the aft offset of the strut-fuselage joint relative to the wing-fuselage joint  204 , and is a relatively large moment about a substantially vertical axis on the wings  200  and struts  300 . As mentioned above, the lifting force generated by each wing  200  is reacted by tension load in the strut  300  that supports the wing  200 . Due to the aft offset of the strut-fuselage joint, the tension load in the strut  300  induces the vertical moment M z  about a substantially vertical axis (i.e., parallel to the Z axis of the reference court system  128 ) at the wing root  202  and strut root  302 . Also shown in  FIGS.  17 - 20    are reaction forces  608  at the wing-fuselage joint  204  and at the strut-fuselage joint  304 , and which area also in response to the lifting force  600 . As can be seen, the wing  200  is under compression load  604 , and the strut  300  is under tension load. The reaction force  608  at the wing-fuselage joint  204  is compression, and the reaction force  608  at the strut-fuselage joint  304  is tension. 
     As mentioned above, the reaction forces  608  include the vertical moment M z , which is induced by the lifting force  600  about the wing-fuselage joint  204 . The vertical moment M z  is due to the location of the strut-fuselage joint  304  at least partially aft of the wing-fuselage joint  204  (e.g., see  FIG.  18   ). Stated another way, the vertical moment M z  is created as a result of the non-parallel relationship between the wing axis  212  and the strut axis  312  (e.g., see  FIG.  20   ) when the aircraft  100  is viewed from a top-down direction. The vertical moment M z  tends to urge the wing  200  to pivot about the wing root  202  in an aftward direction. The vertical moment M z  is in addition to the moment (not shown) generated by engine thrust, and in addition to moment (not shown) generated by aerodynamic drag on the wing  200 , the engine  120 , and the strut  300 , and/or in addition to yawing moments (not shown). Typically (e.g., for commercial airliners), the vertical moments resulting from engine thrust, aerodynamic drag, and yawing moments are much smaller than the vertical moment M z  created by the angle between the wing  200  and the strut  300  (e.g.,  FIG.  18   ). Also shown in  FIGS.  17 - 18    is a reaction force  608  (i.e., parallel to the Y axis of the reference court system  128 ) in the fore-aft direction (i.e., shear load into the fuselage  102 ). The reaction force  608  in the fore-aft direction is also a result of the location of the strut-fuselage joint  304  below and at least partially aft of the wing-fuselage joint  204 . 
     In the present disclosure, the aircraft  100  is configured such that the wing  200  and/or the strut  300  on each side of the aircraft  100  has a structural arrangement configured to counteract or resist the vertical moment M z . The structural arrangement of the wing  200  and/or the strut  300  prevents the vertical moment M z  from pivoting the wing  200  in an aftward direction, at least to an extent causing plastic deformation of the structural members of the aircraft  100 . The below discussion describes various examples of structural arrangements of the wing  200  and/or the strut  300  for counteracting the vertical moment M z . 
     Referring to  FIGS.  21 - 22   , shown are schematic diagrams respectively similar to  FIGS.  17 - 18   , and illustrating an example of a structural arrangement of a strut  300  configured as a cantilevered beam  320  for resisting the vertical moment M z  induced by the lifting force  600 . The cantilevered beam  320  of the strut  300  is non-rotatably or fixedly coupled to the fuselage  102  via a fixed joint  388  at the strut-fuselage joint  304 , and is configured to carry tension and bending load to counteract the vertical moment M z  induced by the lifting force  600 . For the moment M y  (not shown) about a horizontal axis parallel to the Y axis at the strut-fuselage joint  304 , the strut  300  can be either fixedly coupled or pivotably coupled to the fuselage  102 .  FIGS.  23 - 24    show the bending (i.e., exaggerated for illustration purposes) of the cantilevered beam  320  of the strut  300  in response to the lifting force  600 . Also shown is the wing  200  under compression load  604 , and the reaction force  608  (i.e., pure axial load, and no bending load) at the wing-fuselage joint  204 . In addition, shown is the strut  300  (i.e., the cantilevered beam  320 ) in bending, and the reaction force  608  at the strut-fuselage joint  304 , comprising tension in combination with bending moment from the vertical moment M z,s . Additionally, shown is a reaction force  608  in the fore-aft direction (i.e., shear load, parallel to the Y axis) at the strut-fuselage joint  304 . Configuring the strut  300  as a cantilevered beam  320  for resisting the vertical moment M z,s  may favor an arrangement in which the strut  300  has a relatively large chord at the strut root  302 . 
     Referring to  FIGS.  25 - 26   , shown are schematic diagrams respectively similar to  FIGS.  17 - 18   , and illustrating an example of a structural arrangement of a wing  200  configured as a cantilevered beam  320  for resisting the vertical moment M z  induced by the lifting force  600 . In such an arrangement, for the vertical moment M z,w , the cantilevered beam  320  of the wing  200  is non-rotatably or fixedly coupled via a fixed joint  388  to the fuselage  102 , and is configured to carry compression and bending.  FIGS.  27 - 28    show exaggerated bending of the cantilevered beam  320  of the wing  200  in response to the lifting force  600 . The reaction forces  608  in  FIGS.  27 - 28    are similar to the reaction forces  608  described above for  FIGS.  23 - 24   , with the exception that the wing  200  is in bending, and the strut  300  is under tension load  602 . The reaction forces  608  at the strut-fuselage joint  304  comprise pure tension, and no bending load. The reaction forces  608  at the wing-fuselage joint  204  comprise compression in combination with the above-mentioned vertical moment M z,w . In addition, a reaction force  608  in the fore-aft direction (i.e., parallel to the Y axis) is induced at the wing-fuselage joint  204 . 
     Referring to  FIGS.  29 - 32   , shown is an example of a structural arrangement in which both the wing  200  and the strut  300  are configured as cantilevered beams  320  for counteracting the vertical moment M z  induced by the lifting force  600 . The strut  300  and the wing  200  share in resisting the vertical moment M z . More specifically, the portion of the vertical moment M z,w  counteracted by the wing  200 , in combination with the portion of the vertical moment M z,s  counteracted by the strut  300 , is equivalent to the total magnitude of the vertical moment M z  for the unstacked arrangement of the wing  200  and strut  300 . The loads in the wing  200  and strut  300 , and the reaction forces  608  at the wing-fuselage joint  204  and the strut-fuselage joint  304 , are similar to the above-described corresponding loads and reaction forces  608  in  FIGS.  21 - 28   . 
     In one example of the arrangement shown in  FIGS.  29 - 32   , the strut  300  is configured to counteract more than 50 percent of the vertical moment M z , and the wing  200  is configured to counteract a remaining portion of the vertical moment M. The apportionment of vertical moment M z  between the wing  200  and the strut  300  may be based in part on the amount of upward load on the wing  200  carried by the strut  300 . In this regard, the relative stiffness (i.e., in the horizontal direction) of the wing  200  and the strut  300  measured at the strut-wing joint  306  may dictate the distribution of the vertical moment M z . In one example, the wing  200  (and the wing-fuselage joint  204 ) may be configured to counteract  69  percent (e.g., 65-75 percent) of the vertical moment M z , and the strut  300  (and the strut-fuselage joint  304 ) may be configured to counteract 31 percent (i.e., or a remaining portion) of the vertical moment M z . 
     Advantageously, configuring the strut  300  and the wing  200  such that each carries a portion of the vertical moment M z  allows for a reduction in the structural mass of the wing-fuselage joint  204  and the strut-fuselage joint  304 , since neither joint is required to carry 100 percent of the vertical moment M z . In addition, such an arrangement provides structural redundancy. For example, if the wing-fuselage joint  204  and the strut-fuselage joint  304  are each designed to carry 50 percent of the vertical moment Mz, then if one of the joints is ineffective, the remaining joint can carry the vertical moment M z  due to a built-in safety factor typical of structural design. Thus, a degree of fail-safety is provided for an arrangement in which the vertical moment M z  is shared between the wing  200  and the strut  300  in approximately equal proportions. 
     Referring to  FIGS.  33 - 45   , shown are structural arrangements in which the strut  300  is configured to carry the entirety of the vertical moment M z  induced by the lifting force  600 . In the example of  FIG.  33 - 45   , the structural arrangement is based on the concept that the structural efficiency and stiffness of the strut  300  increases as the strut chord increases. In the examples shown, the strut  300  is configured as an strut A-frame structure  322  having a strut front spar  326  and a strut rear spar  328 . The combination of the wing  200  (i.e., the wing axis  212 ) and the strut A-frame structure  322  (i.e., the strut front spar  326  and the strut rear spar  328 ) defines a lower tetrahedron configuration  324 . 
     In  FIGS.  33 - 45   , the strut front spar  326  and the strut rear spar  328  each have a strut spar inboard end  408  and a strut spar outboard end  410 . Reference character D represents the location of the strut front attach point  400  ( FIG.  35   ), and reference character E represents the location of the strut rear attach point  402  ( FIG.  35   ). As mentioned above, reference character C represents the strut-fuselage joint  304 . The strut spar outboard ends  410  ( FIG.  35   ) of the strut front spar  326  and strut rear spar  328  converge at the strut-wing joint  306 . The strut front spar  326  and the strut rear spar  328  are respectively configured to carry tension load  602  ( FIG.  37   ) and compression load  604  ( FIG.  37   ) in response to the vertical moment M z  induced by the lifting force  600 . The strut spar inboard ends  408  are spaced apart from each other at the strut-fuselage joint  304 , and are configured to transfer tension load  602  and compression load  604  into the fuselage  102  at a strut front attach point  400  and a strut rear attach point  402 . 
       FIGS.  37 - 38    illustrate the loads and reaction forces  608  on the wing  200  and the strut  300  as a result of the lifting force  600  at the strut-wing joint  306 . As can be seen, the wing  200  is subjected to compression load  604 , and the reaction force  608  at the wing-fuselage joint  204  is compression. The strut front spar  326  is subjected to tension load  602 , and the reaction force  608  at the strut front attach point  400  is tension. The strut rear spar  328  is typically subjected to compression load  604 , and the reaction force  608  at the strut rear attach point  402  is compression. 
       FIGS.  39 - 40    are magnified top-down views showing the strut-fuselage joint  304 , and the resolution of the reaction forces  608  at the strut front attach point  400  and the strut rear attach point  402  into reaction forces  608  in the lateral direction (i.e., tension and compression, oriented perpendicular to the longitudinal axis  126 ) and reaction forces  608  (i.e., shear load) in the fore-aft direction (i.e., parallel to the longitudinal axis  126 ). 
       FIG.  41    is a chart of the reaction forces  608  at the strut front and rear attach points  400 ,  402  due to tension load T and vertical moment M z  for four different configurations of the strut  300 . As shown in the chart, each of the four strut  300  configurations has a different attach point spacing between the strut front attach point  400  (reference character D) and the strut rear attach point  402  (reference character E). The difference in attach point spacing (“DE”—e.g.,  FIGS.  61  and  64   ) may be due to different angular spacings of the strut front spar  326  and the strut rear spar  328  and/or due to different configurations of the strut root  302 . 
     In  FIG.  41   , the magnitude of the reaction forces  608  is represented by the length of the arrows. Although the reaction forces  608  due to the tension load T are of the same magnitude for each of the four strut configurations, the reaction forces  608  due to the vertical moment M z  are significantly different. For example, for the strut configuration on the extreme left-hand side of the chart, the attach point spacing between the strut front and rear attach points  400 ,  402  is the smallest of the four configurations, and which results in relatively large magnitude reaction forces  608  at the strut front and rear attach points  400 ,  402 . In contrast, for the strut configuration on the extreme right-hand side of the chart, the attach point spacing is the largest of the four strut configurations, and which results in relatively small reaction forces  608  at the strut front and rear attach points  400 ,  402 . 
     Referring still to  FIG.  41   , the chart shows the summation of the reaction forces  608  due to the tension load T and the vertical moment M z  for each of the four strut configurations. In general, the chart shows that the structural efficiency and bending stiffness of the strut  300  increases as the attach point spacing (“DE”) increases between the strut front attach point  400  and the strut rear attach point  402 . Increased structural efficiency represents reduced reaction forces at D and E due to the vertical moment M z  at the strut front attach point  400  and the strut rear attach point  402 , which translates into reduced structural mass of the aircraft  100 .  FIG.  41    also shows that the reaction force  608  at the rear strut attach point  402  can be compression, tension, or even zero, depending upon the attach point spacing. 
     Referring back to  FIG.  40   , shown is an example of a strut A-frame structure  322  having an inboard end connector  330  interconnecting the strut spar inboard end  408  of the strut front spar  326  with the strut spar inboard end  408  of the strut rear spar  328 . The inboard end connector  330  is configured to transfer shear load into the fuselage  102  at the strut-fuselage joint  304 . The shear load (i.e., parallel to the Y axis) is a reaction force  608  to the tension load  602  and the compression load  604  respectively carried by the strut front spar  326  ( FIG.  38   ) and the strut rear spar  328  ( FIG.  38   ). 
     In  FIG.  40   , the inboard end connector  330  is shown coupled to the fuselage  102  at a single location for transferring the shear load as a single reaction force  608  into the fuselage  102 . The inboard end connector  330  is either a separate connector beam (not shown), or the inboard end connector  330  is integrated into the structure of the fuselage  102  portion between the strut spar inboard end  408  of the strut front spar  326  and the strut spar inboard end  408  of the strut rear spar  328 . Although  FIG.  40    shows the inboard end connector  330  coupled to the fuselage  102  at a single location approximately midway between the strut front attach point  400  and strut rear attach point  402 , the inboard end connector  330  allows the reaction force  608  (i.e., the shear reaction) to be transferred into the fuselage  102  at any location between the strut front attach point  400  and the strut rear attach point  402 . Alternatively, the shear load can be distributed along the entire length of the inboard end connector  330 . 
     Referring to  FIGS.  42 - 43   , shown is an example of the strut  300  having a strut front spar  326  and a strut rear spar  328  encapsulated within the airfoil shape of the strut  300 . As shown in  FIG.  43   , the airfoil shape is defined by a strut upper skin panel  358  and a strut lower skin panel  360 . The strut  300  includes a strut leading edge  314  and a strut trailing edge  316 , each extending from the strut root  302  at the strut-fuselage joint  304 , to the strut outboard end  310  at the strut-wing joint  306 . The strut leading edge  314  and the strut trailing edge  316  define a tapered shape for the strut  300 . Advantageously, the tapered shape of the strut  300  is complementary to the strut A-frame structure  322  of the strut front spar  326  and the strut rear spar  328 . The aerodynamic properties of the strut A-frame structure  322  are favorable, in that a progressively smaller strut chord near the strut-wing joint  306  minimizes interference drag between the strut  300  and the wing  200 . Furthermore, the relatively large strut chord at the strut-fuselage joint  304  enables the strut  300  to handle a large portion (e.g., an entirety) of the vertical moment M z  induced by the lifting force  600 . 
     Referring to  FIGS.  44 - 46   , shown in  FIGS.  44 - 45    are plots of the aerodynamic penalty  342 , structural penalty  340 , and structural benefit  344  as a function of the geometry of the lower tetrahedron configuration  324  of  FIG.  46   . As described above, the lower tetrahedron configuration  324  of  FIG.  46    is defined by the wing axis  212 , and by the strut A-frame structure  322 , as shown in  FIGS.  31 - 38   . In  FIG.  46   , reference character O is at the same longitudinal location as the wing-fuselage joint  204 , and reference character C represents the longitudinal location of the strut-fuselage joint  304 . As mentioned above, reference character D represents the longitudinal location of the strut front attach point  400 , and reference character E represents the longitudinal location of the strut rear attach point  402 . Reference character C represents the strut-fuselage joint  304 , and in  FIG.  46   , reference character C may be described as being located at the midpoint between the strut front attach point  400  (D) and the strut rear attach point  402  (E). 
       FIG.  44    is a moment diagram  620  illustrating a direct proportional relationship between distance OC and the magnitude of the vertical moment M z . As can be seen, the structural penalty  340  (i.e., aircraft weight) increases as distance OC increases.  FIG.  44    also illustrates the decrease in aerodynamic penalty  342  (e.g., decreased interference drag) that occurs with an increase in distance OC.  FIG.  45    is a plot of structural benefit  344  as a function of the attach point spacing (“DE”) between the strut front spar  326  and the strut rear spar  328 . As can be seen, the structural benefit  344  (i.e., reduction in aircraft weight) increases as the distance DE increases. In addition,  FIG.  45    illustrates that distance DE is directly proportional to the ability of the strut  300  to resist the vertical moment M z . The larger the distance DE, the greater the ability of the strut  300  to resist the vertical moment M z . 
     Referring to  FIGS.  44 - 47   , shown are examples of an aircraft  100  in which the wing  200  includes a wing-A-frame structure  252 . The wing A-frame structure  252  extends from the wing-fuselage joint  204  at least to the strut-wing joint  306 . The wing A-frame structure  252  includes a wing front member  260  and a wing rear member  262 . The wing front member  260  and the wing rear member  262  may be alternatives to, or in addition to, the primary load-carrying structures of the wing  200 , which typically comprises a wing front spar  220  ( FIG.  6   ) and a wing rear spar  222  ( FIG.  6   ). 
     At the wing-fuselage joint  204 , the wing front member  260  has a wing front attach point  236 , which is identified by reference character G. The wing rear member  262  has a wing rear attach point  238 , which is identified by reference character H. As mentioned earlier, the strut-wing joint  306  is identified by reference character B, and the strut-fuselage joint  304  is identified by reference character C. The combination of the wing front member  260 , the wing rear member  262 , and the strut  300  form an upper tetrahedron configuration  268 . 
     In  FIGS.  47 - 50   , the wing front member  260  and the wing rear member  262  each have a wing member inboard end  264  and a wing member outboard end  266 . The wing member inboard end  264  of the wing front member  260 , and the wing member inboard end  264  of the wing rear member  262 , are spaced apart from each other at the wing-fuselage joint  204 . The wing member outboard end  266  of the wing front member  260  and the wing member outboard end  266  of the wing rear member  262  converge proximate the strut-wing joint  306 . 
       FIGS.  49 - 50    illustrate the loads on the wing front member  260 , wing rear member  262 , and strut  300 , and the reaction forces  608  at the wing-fuselage joint  204  and the strut-fuselage joint  304 . The wing front member  260  and the wing rear member  262  are respectively sized and configured to respectively carry at least a portion of the tension load  602  and the compression load  604 , to thereby counteract the vertical moment M z  induced by the lifting force  600 . In some examples, the wing A-frame structure  252  may be configured to carry an entirety of the vertical moment M z  induced by the lifting force  600 . The structural efficiency of the wing  200  in resisting the vertical moment M z  is improved as the spacing increases between the wing front attach point  236  and the wing rear attach point  238 . To avoid interference of the wing front and rear members  260 ,  262  with the wing front and rear spars  220 ,  222  ( FIG.  6   ), or with the wing fuel tanks (not shown), the wing front member  260  and wing rear member  262  may each be provided as two separate members (not shown), with one member located proximate the upper surface of the wing  200 , and the other member located proximate the lower surface of the wing  200 . 
     Referring to  FIGS.  51 - 54   , shown is an example of a double tetrahedron configuration in which the wing  200  has a wing A-frame structure  252 , and the strut  300  has a strut A-frame structure  322 . The loads and reaction forces  608  associated with the wing A-frame structure  252  and the strut A-frame structure  322  are similar to the loads and reaction forces  608  described above. The structural efficiency of the double tetrahedron configuration increases as the distance between the wing front and rear attach points  236 ,  238  (e.g., reference characters G and H) increases, and/or as the distances between the strut front and rear attach points  400 ,  402  (e.g., reference characters D and E) increases. 
     Referring to  FIGS.  55 - 58   , shown in  FIG.  56    is a plot of the conceptual weight  622  of a wing  200  vs. wingspan, for two different wing configurations. The area under the phantom line represents the weight of a typical cantilevered wing  624 . The area under the solid line represents the weight of a strut-braced-wing  626 , similar to the wing  200  of  FIG.  55   . The weight of each wing  200  is the structural mass required to react the wing bending moment due primarily to aerodynamic loading on the wing  200 . The dashed line represents a cut-off for the weight of the wing  200  due to a minimum gauge limitation  628 , which recognizes that even at a bending moment near zero, the wing structural elements cannot have zero thickness and/or zero cross-sectional area. 
     As can be seen in  FIG.  56   , the shape of the plot for the strut-braced-wing  626  is significantly different than the shape of the plot for the typical cantilevered wing  624 . For example, the strut-braced-wing  626  has an up-bending moment at the wing root  202  that is very small, and may even be negative, depending on the wing configuration. For most of the wing  200  between the wing root  202  and the strut-wing joint  306 , the vertical bending moment is small. The crossed-hatched area in  FIG.  56    represents the structural weight savings achieved with the strut-braced-wing  626  of  FIG.  55   . 
       FIG.  57    is a plot of conceptual weight  630  vs. wingspan for the vertical moment M z  reacted by the wing  200 . Due to the aft offset of the strut-fuselage joint  304  relative to the wing-fuselage joint  204 , the vertical moment M z  can be relatively large, resulting in correspondingly large wing weight (i.e., structural mass) to carry the vertical moment M z . 
       FIG.  58    is a combination of the plots of  FIGS.  56  and  57   . The structural mass required to carry the vertical moment M z  detracts from the weight savings that would otherwise be achieved from using the strut-braced wing  200 . The remaining weight savings is represented by the cross-hatched area between the curve of the typical cantilevered wing  624 , and the curve of the strut-braced-wing  626 . As a result, a larger portion of the vertical moment M z  is preferably carried by the strut  300  rather than the wing  200 , such that the weight savings of the strut-braced wing  200  can be preserved. 
     Referring to  FIGS.  59 - 64   , shown in  FIG.  59    is a top-down view of a portion of the aircraft  100  illustrating an example of a strut A-frame structure  322 .  FIGS.  60 - 61    show an example of the strut  300  for which the strut front attach point  400  and the strut rear attach point  402  are at the same longitudinal location as the inboard ends of the strut front spar  326  and strut rear spar  328 . In this regard, the attach point spacing (“DE”) is dictated by the spacing between the inboard ends of the strut front spar  326  and the strut rear spar  328 .  FIG.  61    shows the relatively large reaction forces  608  at the strut front attach point  400  and strut rear attach point  402 .  FIG.  62    is a plot of the bending moment M s  of the strut  300  (i.e., due the vertical moment) as a function of strut length, illustrating that the highest bending moment occurs at the strut root  302 . 
       FIGS.  63 - 64    illustrate an example of a strut A-frame structure  322  in which the strut front attach point  400  is located forward of the strut front spar  326  and aft of the strut leading edge  314 , and the strut rear attach point  402  is located aft of the strut rear spar  328  and forward of the strut trailing edge  316 , thereby increasing the attach point spacing. As mentioned above, increasing the attach point spacing results in a decrease in loads at the strut-fuselage joint  304 . In this regard, the magnitude of the reaction forces  608  at the strut front and rear attach points  400 ,  402  in  FIG.  63    is lower than the magnitude of the reaction forces  608  in  FIG.  60   . The arrangement shown in  FIG.  63 - 64    takes advantage of the volume of space within the strut leading edge portion and within the strut trailing edge portion, to thereby reduce the size and/or structural mass of the strut-fuselage joint  304  as a result of the reduced magnitude of the reaction forces  608 . 
       FIGS.  65 - 92    represent different configurations of the strut  300  for decreasing the magnitude of the reaction forces  608  at the strut-fuselage joint  304 .  FIGS.  65 - 66    represent an arrangement in which the strut front spar  326  and the strut rear spar  328  are each contiguous from the strut-fuselage joint  304  to the strut-wing joint  306 , and each have at least one kink  414  located proximate the strut-fuselage joint  304 . In the example shown, the strut front spar  326  and the strut rear spar  328  each have a single kink  414  dividing the strut spar  326 ,  328  into a strut spar inboard section  416  and a strut spar outboard section  418 . However, the strut  300  may be provided in an arrangement (not shown) wherein each strut spar  326 ,  328  has multiple kinks  414 . At each kink  414 , a kick load (not shown) is generated due to the non-alignment of the spar sections  416 ,  418 . The upper and lower strut skin panels  358 ,  360  and/or other structural members (not shown) may be configured to react the kick loads. 
     In  FIGS.  65 - 66   , the strut spar inboard section  416  of the strut front spar  326  is angled forwardly relative to the strut spar outboard section  418  of the strut front spar  326 , and the strut spar inboard section  416  of the strut rear spar  328  is angled aftwardly relative to the strut spar outboard section  418  of the strut front spar  326 , to thereby increase the distance between the strut spar inboard ends  408 . In the strut  300  includes a kink connector beam  422  extending between and interconnecting the kinks  414  respectively of the strut front spar  326  and the strut rear spar  328 . In addition, the strut  300  includes an inboard end connector  330  connecting the strut spar inboard ends  408  of the strut spar inboard sections  416  of the strut front spar  326  and the strut rear spar  328 . The inboard end connector  330  is configured to transfer shear load from the strut  300  to the fuselage  102 , as described above. 
     Referring still to  FIGS.  65 - 66   , the strut  300  may alternatively or additionally include a kink plate  420  extending between and interconnecting the strut spar inboard section  416  of the strut front spar  326  to the strut spar inboard section  416  of the strut rear spar  328 . As shown in  FIG.  66   , the kink plate  420  is located at the neutral axis of the strut front spar  326  and the strut rear spar  328 . Although not shown, the strut front spar  326  and the strut rear spar  328  may each include spar slots  370  (e.g.,  FIG.  79   ) for receiving the kink plate  420 . The kink plate  420  is configured to facilitate load transfer into the fuselage  102 . 
     Alternatively or additionally, the strut  300  includes a pair of diagonal members  424 , each extending from one of the strut spar inboard ends  408  of one of the strut spars  326 ,  326 , to the kink  414  of the other one of the strut spars  326 ,  326 , as shown in  FIG.  62   . The pair of diagonal members  424  are respectively configured to transfer tension load  602  and compression load  604 . The diagonal members  424  can be rods configured to resist axial load, as the diagonal members  424  are not subjected to bending. In  FIG.  65   , the diagonal members  424  are shown crossing each other. However in other examples, one diagonal member  424  may be located on an upper surface of the kink plate  420 , and the other diagonal member  424  may be located a lower surface of the kink plate  420 . 
     Referring to  FIGS.  67 - 68   , shown is a further example of a strut A-frame structure  322  comprising a strut leading edge member  426  and a strut trailing edge member  428  respectively defining the strut leading edge  314  and the strut trailing edge  316  of the strut  300 . The strut leading edge member  426  and the strut trailing edge member  428  are interconnected by a strut upper skin panel  358  and a strut lower skin panel  360 , and the strut leading edge member  426  and strut trailing edge member  428  each have a strut member inboard end  430  and a strut member outboard end  432 . As shown in  FIGS.  67 - 68   , the strut member inboard ends  430  of the strut leading edge member  426  and strut trailing edge member  428  are spaced apart from each other proximate the strut-fuselage joint  304 . The strut member outboard ends  432  converge at the strut-wing joint  306 . The strut leading edge member  426  and the strut trailing edge member  428  are respectively sized and configured to carry tension load and compression load resulting from the vertical moment M z  induced by the lifting force  600 . 
     The strut leading edge member  426  and the strut trailing edge member  428  are configured respectively such that the strut leading edge  314  and the strut trailing edge  316  are each concavely curved when the aircraft  100  is viewed from a top-down perspective. The curved shape of the strut leading edge member  426  and strut trailing edge member  428  increases the distance between the strut member inboard ends  430 , relative to the distance between the strut member inboard ends  430  if the strut leading edge member  426  and the strut trailing edge member  428  were straight. In addition, the curvature of the strut leading edge  314  minimizes the amount of overlap between the strut leading edge  314  and the wing trailing edge  216  when the aircraft  100  is viewed from a top-down perspective, as shown in  FIG.  59   . 
     The strut leading edge member  426  and the strut trailing edge member  428  may be formed of a durable material for damage resistance during the service life of the aircraft  100 , such as damage during ground operations, or in-flight damage from bird strikes or erosion, such as from hail or debris. In one example, the strut  300  leading and trailing edge members may be machined from a metallic material such as aluminum, steel, or titanium. The strut upper skin panel  358  and the strut lower skin panel  360  function as shear webs for transferring shear load as the strut  300  is subjected to bending load from the vertical moment M z . The strut leading edge and trailing edge members  426 ,  428  and the strut upper and lower skin panels  358 ,  360  may be interconnected in a manner to avoid steps, jumps, or discontinuities in the outer surfaces, particularly near the strut leading edge  314 , to promote laminar flow over the strut  300 . The interior of the strut  300  may include material or structural members to improve buckling load capability. Due to the continuous curvature in the strut leading and trailing edge members  426 ,  428  of  FIG.  67   , instead of a concentrated kick load in the kinked strut spar configuration of  FIG.  65   , the kick load in  FIG.  67    would be distributed along the length of the strut leading and trailing edge members  426 ,  428 . As mentioned above, structure (not shown) would be provided between the strut leading and trailing edge members  426 ,  428  to carry such distributed kick loads. 
     Referring to  FIGS.  69 - 71   , shown is an example of a strut  300  in which the strut front spar  326  and the strut rear spar  328  each have a channel-shaped cross-section comprised of an upper cap  350  and a lower cap  352  interconnected by a spar web  354 , although other cross-sectional shapes may be implemented. The strut front spar  326  and the strut rear spar  328  may be formed of fiber-reinforced polymer matrix material (i.e., composite material, such as graphite-epoxy). The strut front spar  326  and/or the strut rear spar  328  include reinforcing fibers  356  extending continuously from the strut root  302  to the strut outboard end  310 . The reinforcing fibers  356  increase the load-carrying capability of the strut spars  326 ,  328 . Each reinforcing fiber  356  is comprised of a bundle of filaments. The filaments may be formed of any one of a variety of materials including, but not limited to, polymeric material (e.g., carbon fibers) or non-polymeric material such as metallic fibers. In one example, the filaments may be formed of a lightweight and stiff material, such as boron, to increase the tension-load carrying capability of the strut front spar  326 . An alternative material may be used for improving the compression load carrying capability of the strut rear spar  328 . In some embodiments, the reinforcing fibers  356  are embedded within the material of the strut front spar  326  and/or the strut rear spar  328 . In other embodiments, the reinforcing fibers  356  may be bonded or attached by other means to the strut front spar  326  and/or the strut rear spar  328 . As mentioned above, the strut front spar  326  and/or the strut rear spar  328  are not limited to a channel-shaped cross-section as shown, but may be provided in alternative cross-sectional shapes, such as an I-shaped cross section. 
     Referring to  FIGS.  72 - 73   , shown is a still further example of a strut A-frame structure  322  comprising a strut front fitting  434  and a strut rear fitting  436 . The strut front fitting  434  extends forward of (i.e., toward the strut leading edge  314 ) the strut front spar  326 . The strut front fitting  434  is coupled to the strut front spar  326  proximate the strut root  302 , and is configured to distribute load from the strut front spar  326  into the fuselage  102  at the strut front attach point  400  of the strut-fuselage joint  304 . The strut rear fitting  436  extends aft of (i.e., toward the strut trailing edge  316 ) the strut rear spar  328 . The strut rear fitting  436  is coupled to the strut rear spar  328  proximate the strut root  302 , and is configured to distribute load from the strut rear spar  328  into the fuselage  102  at the strut rear attach point  402  of the strut-fuselage joint  304 . By increasing the spacing between the strut front attach point  400  and strut rear attach point  402 , the strut front fitting  434  and the strut rear fitting  436  increase the structural efficiency of the strut-fuselage joint  304 , thereby reducing the magnitude of the reaction forces  608  (e.g.,  FIG.  63   ), which translates into reduced structural mass of the strut-fuselage joint  304 . 
     In  FIGS.  72 - 73   , the strut front fitting  434  and the strut rear fitting  436  are each configured as plates. In the example shown, the plates are located at the neutral axis of the strut front spar  326  and the strut rear spar  328 . The strut front fitting  434  and the strut rear fitting  436  may be bonded, mechanically fastened, welded, or integrally machined respectively with the strut front spar  326  and the strut rear spar  328 . The strut front spar  326  and the strut rear spar  328  are straight in  FIG.  72   . However, in other examples not shown, the strut front spar  326  and strut rear spar  328  may be kinked similar to the strut front and rear spars  326 ,  328  of  FIG.  65   . 
     Referring to  FIGS.  74 - 76   , shown is an arrangement for attaching the strut front fitting  434  and strut rear fitting  436  respectively to the strut front spar  326  and strut rear spar  328 . The strut front spar  326  and the strut rear spar  328  each have the above-described channel-shaped cross-section. However, the strut front spar  326  and strut rear spar  328  may have an alternative cross-sectional shape, such as an I-beam cross-sectional shape (not shown). The strut rear spar  328 , the strut upper skin panel  358 , and the strut lower skin panel  360  collectively form a strut box, which provides bending stiffness and torsional stiffness for the strut  300 . The strut front fitting  434  extends vertically between, and interconnects, the upper cap  350  and the lower cap  352  of the strut front spar  326 . The strut rear fitting  436  extends vertically between, and interconnects, the upper cap  350  and the lower cap  352  of the strut rear spar  328 . 
     In  FIGS.  74 - 76   , the strut front fitting  434  and the strut rear fitting  436  have a cross-sectional shape that is complementary to the cross-sectional shape respectively of the strut front spar  326  and strut rear spar  328 , which improves the transfer of tension load  602  and compression load  604  respectively from the strut front spar  326  and strut rear spar  328  into the strut-fuselage joint  304  ( FIG.  59   ). The strut front fitting  434  and the strut rear fitting  436  may be adhesively bonded and/or mechanically fastened respectively to the strut front spar  326  and strut rear spar  328 . The strut upper skin panel  358  and the strut lower skin panel  360  may optionally be stiffened by skin stiffeners  362  on an interior side of the strut  300 . In the example shown, each skin stiffener  362  has a T-shaped cross-section. However, the skin stiffeners  362  may have other cross-sectional shapes (e.g., a Z-shaped or hat-shaped cross section). The skin stiffeners  362  may be adhesively bonded and/or mechanically fastened to the strut upper skin panel  358  and the strut lower skin panel  360 . In another configuration, instead of skin stiffeners, one or more full-depth spars (not shown) may be installed, with each full-depth spar extending between the strut upper and lower skin panels  358 ,  360 . 
     Referring to  FIGS.  77 - 79   , shown is an example of a strut A-frame structure  322  in which the strut spar inboard end  408  of the strut front spar  326  and the strut rear spar  328  has a spar slot  370  formed in the spar web  354  at the strut root  302  end. Each spar slot  370  extends along the neutral axis of the respective strut front spar  326  and strut rear spar  328 . The strut A-frame structure  322  includes a lug plate  372  (i.e., a shear plate) inserted within the spar slot  370  in the strut front spar  326  and the strut rear spar  328 . The lug plate  372  interconnects the strut front spar  326  and the strut rear spar  328 . As shown in  FIGS.  77 - 78   , the lug plate  372  extends forward of the strut front spar  326 , and extends aft of the strut rear spar  328 , thereby providing increased spacing between the strut front attach point  400  and strut rear attach point  402 . 
     In  FIGS.  77 - 79   , the lug plate  372  is coupled (e.g., via mechanical fasteners  382 ) to the strut front spar  326  and strut rear spar  328  via a plurality of angle brackets  374 . The strut A-frame structure  322  further includes a plurality of strut lugs  376  extending in an inboard direction from the lug plate  372 . As shown in  FIGS.  77 - 78   , a plurality of strut lugs  376  are located forward of the strut spar inboard end  408  of the strut front spar  326 , and a plurality of strut lugs  376  are located aft of the strut spar inboard end  408  of the strut rear spar  328 . The strut lugs  376  are parallel to each other, and are spaced apart complementary to the spacing of a plurality of fuselage lugs  110  (e.g.,  FIG.  80   ) protruding from the fuselage  102 . 
     Referring to  FIGS.  80 - 81   , shown is an example of a pinned joint  386  for coupling a strut  300  to the fuselage  102 . As mentioned above, the fuselage  102  has a plurality of parallel and spaced apart fuselage lugs  110  protruding in an outboard direction at the strut front attach point  400  ( FIG.  77   ) and at the strut rear attach point  402  ( FIG.  77   ). The strut lugs  376  are coupled to the fuselage lugs  110  via one or more pins  384 . For example, a pin  384  may be installed at the strut front attach point  400  and a pin  384  may be installed at the strut rear attach point  402 . Alternatively, a single common pin  384  may extend through the strut lugs  376  and fuselage lugs  110  of the strut front attach point  400  and strut rear attach point  402 . In another example, the one or more pins  384  may each be configured in a coaxial pin arrangement (not shown) consisting of an inner pin within an outer pin, for fail-safety. 
     In  FIGS.  80 - 81   , the one or more pins  384  allow rotation or pivoting of the strut  300  about an axis parallel to the longitudinal axis  126  ( FIG.  4   ) of the aircraft  100 . The pinned joint  386  allows the strut  300  to pivot slightly in an upward and downward direction during changes in loading on the wing  200  (e.g., during takeoff, maneuvering, turbulence, landing, etc.), thereby reducing or eliminating bending loads at the strut-fuselage joint  304 . In contrast,  FIGS.  82 - 83    show an example of a fixed joint  388  for fixedly or non-rotatably coupling the strut  300  to the fuselage  102 , as described in greater detail below. As shown in  FIGS.  81  and  83   , the pinned joint  386  allows for larger amount of buckling  610  ( FIG.  81   ) of the strut  300 , relative to the magnitude of buckling  610  ( FIG.  83   ) of the strut  300  attached to the fuselage  102  via the fixed joint  388 . In this regard, the fixed joint  388  provides higher bucking load capability for the strut  300  relative to the pinned joint  386 . In addition, the fixed joint  388  may provide greater resistance to lateral torsional buckling of the strut  300 , as described below. 
     Referring to  FIGS.  84 - 85   , shown is an example of a pinned joint  386  coupling the strut  300  to the fuselage  102 . The strut  300  has the strut A-frame structure  322  described above and shown in  FIGS.  77 - 79   . In this regard, the strut A-frame structure  322  includes the above-described lug plate  372  that interconnects the strut front spar  326  and the strut rear spar  328 . The lug plate  372  extends through the spar slot  370  ( FIG.  79   ) formed in the inboard end of the strut front spar  326  and strut rear spar  328 . Angle brackets  374  are used for mechanically fastening the lug plate  372  to the strut front spar  326  and the strut rear spar  328 . 
     The lug plate  372  includes a plurality of the above-described strut lugs  376 , which are located forward of the strut front attach point  400 , and aft of the strut rear attach point  402 . The strut lugs  376  may be integrally formed (e.g., machined) with the lug plate  372 , or the strut lugs  376  may separate components that are attached (e.g., mechanically fastened, welded) to the lug plate  372 . As shown in  FIG.  84   , the strut  300  includes a lug bracket  378  at the inboard edge of the lug plate  372 . The lug bracket  378  is shown oriented substantially vertical, or normal to the strut axis  312  and the strut chord. In addition, the lug bracket  378  extends parallel to the joint rotational axis defined by the pin  384 . The lug bracket  378  stabilizes the strut lugs  376 , and facilitates the transfer of load from the lug plate  372  into the strut lugs  376 . The lug plate  372 , lug plate  372 , and strut lugs  376  transfer into the fuselage  102  tension load  602  from the strut front spar  326 , and compression load  604  from the strut rear spar  328 . In addition, the lug plate  372  and strut lugs  376  facilitate the transfer of shear load between the strut  300  and the fuselage  102 . 
     Referring to  FIGS.  86 - 89   , shown in  FIG.  86    is an example of net tension load  602  (i.e., pure axial load) applied by the strut  300  at the strut-fuselage joint  304 , as a result of the vertical moment M z  induced by the lifting force  600  ( FIG.  37   ) at the strut-wing joint  306 .  FIG.  88    shows the vertical moment M z  on the strut  300  as a result of the lifting force  600 . For most flight conditions, the ratio of the vertical moment M z  to the axial load will be generally constant.  FIG.  87    is an axial load profile  396  of the tension load  602  on the plurality of strut lugs  376  at the strut front attach point  400 , and at the strut rear attach point  402 . As can be seen, the most highly loaded strut lugs  376  at each attach point  400 ,  402  are those that are located in the middle of the plurality of strut lugs  376 . 
       FIG.  89    is a moment profile  398  of the moment at the strut front attach point  400  and at the strut rear attach point  402 . As can be seen, the moment generally peaks at the extreme ends of the strut-fuselage joint  304  (i.e., at the forward end, and at the aft end). The configuration of the strut lugs  376  at the strut front attach point  400  and strut rear attach point  402  can be tailored to achieve substantially uniform loads in the strut lugs  376  and fuselage lugs  110 , thereby providing an opportunity for increasing the structural efficiency of the strut-fuselage joint  304 , which may translate to reduce structural mass of the aircraft  100 . 
     Referring to  FIG.  90   , shown is an example of a strut A-frame structure  322  having a lug plate  372  and strut lugs  376  similar to the above-described arrangement shown in  FIGS.  84 - 85   . In  FIG.  90   , the lug plate  372  extends from the strut spar inboard end  408  a further distance outboard along the strut front spar  326  than the distance that the lug plate  372  extends along the strut rear spar  328 . Additional angle brackets  374  are included along the strut front spar  326  to facilitate the transfer of a higher tension load  602  from the strut front spar  326  into the lug plate  372 , relative to the tension load  602  in the strut front spar  326  of the arrangement shown in  FIGS.  84 - 85   . 
     Referring to  FIGS.  91 - 92   , shown is an example of a fixed joint  388  coupling a strut A-frame structure  322  to the fuselage  102 . The strut A-frame structure  322  includes a lug plate  372  coupled to the strut front spar  326  and strut rear spar  328  via angle brackets  374 , as described above. In addition, the strut A-frame structure  322  includes a strut end plate  380 . The strut end plate  380  is coupled to the strut spar inboard end  408  of the strut front spar  326  and the strut rear spar  328 . In the example shown, the strut end plate  380  extends across the edge of the lug plate  372 , and interconnects the strut front spar  326  and the strut rear spar  328 . The strut end plate  380  is attached (e.g., via mechanical fasteners  382 ) to the fuselage  102 , thereby non-rotatably coupling the strut spar  326 ,  328  to the fuselage  102 , such that the strut  300  is a cantilevered beam  320 , as shown in the above-described  FIGS.  21 - 24   . As mentioned above with regard to  FIG.  83   , non-rotatably coupling the strut spars  326 ,  328  to the fuselage  102  may improve the buckling load capability of the strut  300 , and may also suppress lateral-torsional buckling of the strut  300 , as described below. 
     Referring to  FIGS.  93 - 108   , shown is an example of a structural arrangement for attaching the strut  300  to the wing  200  at the strut-wing joint  306 , for the aircraft  100  of  FIG.  93   .  FIGS.  94 - 95    show the structural arrangement as a pinned joint  386  between the strut  300  and the wing  200 .  FIGS.  93 - 94    illustrate the pinned joint  386  in the assembled state.  FIGS.  98 - 108    illustrate the configuration of the individual components that make up the pinned joint  386 . 
     As shown in  FIGS.  94 - 97   , the strut outboard ends  310  of the strut front spar  326  and strut rear spar  328  respectively have a front spar plate  438  and a rear spar plate  440 . The front spar plate  438  and the rear spar plate  440  each extend in an outboard direction and overlap each other, and are coupled together via mechanical fasteners  382 . Advantageously, the arrangement of the front spar plate  438  and the rear spar plate  440  provides a means for resolving the tension load  602  in the strut front spar  326  and the compression load  604  in the strut rear spar  328  into axial tension and shear load between the strut  300  and the wing  200 . 
     As shown in  FIGS.  98 - 101   , the front spar plate  438  is inserted into a spar slot  370  formed along the neutral axis in the strut outboard end  310  of the strut front spar  326 .  FIGS.  102 - 105    show the rear spar plate  440  inserted into a spar slot  370  formed along the neutral axis in the strut outboard end  310  of the strut rear spar  328 .  FIGS.  106 - 108    show an example where a spar plate doubler  442  is included with the rear spar plate  440  to facilitate compression load transfer between the strut rear spar  328  and the rear spar plate  440 . Although not shown, a similar spar plate doubler  442  may be included with the front spar plate  438  to facilitate tension load transfer between the strut front spar  326  and the front spar plate  438 . Use of spar plate doublers  442  may reduce the diameter and/or quantity of mechanical fasteners  382 , due to the increased (i.e., double) shear capacity of the mechanical fasteners  382  as a result of adding the spar plate doubler  442 . 
     In  FIGS.  98 - 108   , angle brackets  374  are used for mechanically fastening the front spar plate  438  to the strut front spar  326 . Similarly, angle brackets  374  are used to couple the rear spar plate  440  to the strut rear spar  328 . However the front and rear spar plates  438 ,  440  may be respectively coupled to the strut front and rear spars  326 ,  328  in any one of a variety of means. For example, the front and rear spar plates  438 ,  440  may be integrally formed (e.g., machined) respectively with the strut front and rear spars  326 ,  328 . 
     As shown in  FIGS.  98 - 99   , the front spar plate  438  has a plurality of strut lugs  376  protruding in an outboard direction. Likewise,  FIGS.  102 - 105    show a plurality of strut lugs  376  protruding from the rear spar plate  440 . The strut lugs  376  of the front spar plate  438  and the rear spar plate  440  are generally vertically oriented. As shown in  FIGS.  94 - 95   , the strut lugs  376  are spaced apart from each other complementary to the spacing of the wing lugs  234 , which protrude in an inboard direction from the underside of the wing  200 . The wing lugs  234  may be directly or indirectly coupled to the wing front spar  220  (not shown) and/or the wing rear spar  222  (not shown). The strut lugs  376  are rotatably coupled to the wing lugs  234  via a pin  384 , which is oriented approximately parallel to the longitudinal axis  126 . The pin  384  allows for upward and downward pivoting of the strut  300  during changes in loading on the wing  200 . 
     Referring back to  FIGS.  94 - 95   , the strut-wing joint  306  further includes at least one drag link  444  for accommodating shear loads between the wing  200  and the strut  300 . In the example shown, the spar front plate is coupled to the wing  200  via a front drag link  444 . The front drag link  444  extends in a forward direction from a plate front portion of the front spar plate  438 . Similarly, the rear spar plate  440  is coupled to the wing  200  via a rear drag link  446 . The rear drag link  446  extends in an aft direction from a plate aft portion of the rear spar plate  440 . As mentioned above, the coupling of the front spar plate  438  to the rear spar plate  440  resolves the tension load  602  and compression load  604  respectively in the strut front spar  326  and strut rear spar  328  into tension load  602  in the wing lugs  234 , and compression and tension respectively in the front drag link  444  and rear drag link  446 . The pin  384  transfers axial load (e.g., tension load  602 ) between the strut lugs  376  and the wing lugs  234 . 
     Referring to  FIGS.  109 - 113   , shown are examples of a jury strut  500  that may be included with the strut-braced aircraft  100 . The jury strut  500  extends between the strut  300  and the wing  200 , and is included to suppress buckling  610  ( FIG.  109   ) of the strut  300  at high compression loads. When the aircraft  100  is viewed from the front as shown in  FIG.  109   , the jury strut  500  is oriented approximately (e.g., within 20 degrees) perpendicular to the strut  300 . The jury strut  500  is coupled to the strut  300  at a distance from the strut-fuselage joint  304  of approximately (e.g., within 30 percent) two-thirds of the distance between the strut-fuselage joint  304  and the strut-wing joint  306 . 
     As shown in  FIG.  110   , the jury strut  500  may be coupled to the strut  300  proximate the strut front spar  326 . Such an arrangement may allow for lateral pivoting movement of the strut  300 , as shown in  FIG.  108   . Because the strut rear spar  328  is in compression, it may have a tendency to buckle via lateral-torsional buckling.  FIGS.  112 - 113    illustrate an arrangement in which the jury strut  500  has a width that is at least as wide as the distance between the strut front spar  326  and the strut rear spar  328  at the location wherein the jury strut  500  is coupled to the strut  300 . As a result, the jury strut  500  couples both the strut front spar  326  and the strut rear spar  328  to the wing  200 , and thereby has the capability to suppress lateral-torsional buckling of the strut  300 . 
     Referring to  FIGS.  114 - 117   , shown is an example of a wing-wing joint  208  at the location where the wings  200  attach to the fuselage  102 . As shown in  FIGS.  115 - 116   , each wing  200  includes the above-mentioned wing front spar  220  and wing rear spar  222 . In addition, the wing  200  also has a wing upper skin panel  224  ( FIG.  13   ) and a wing lower skin panel  226  ( FIG.  13   ). The wing front spar  220 , the wing rear spar  222 , the wing upper skin panel  224 , and the wing lower skin panel  226  collectively form a wing box, which provides bending stiffness and torsional stiffness for the wings  200 . 
     The wing front spar  220  and the wing rear spar  222  of each wing  200  have a wing spar inboard end  230 . A spar slot  370  is formed in the wing spar inboard end  230  of the wing front spar  220  and the wing rear spar  222 . Each wing  200  further includes a wing shear plate  232  interconnecting the wing spar inboard ends  230  of the wing front spar  220  and the wing rear spar  222 . The wing shear plate  232  is received within the spar slots  370 , and is mechanically coupled to the wing front spar  220  and the wing rear spar  222  via angle brackets  374  or other suitable means. 
     In addition, each wing  200  includes one or more wing lugs  234  protruding in an inboard direction from the wing shear plate  232 . In the example shown, a plurality of wing lugs  234  are located forward of the wing front spar  220 , and a plurality of wing lugs  234  are located aft of the wing rear spar  222 . Coupled to the inboard edge of each wing shear plate  232  is a lug bracket  378  for interconnecting and mechanically stabilizing the wing lugs  234 . On each wing  200 , the lug bracket  378  is connected to the wing front spar  220  and the wing front spar  220  respectively at the wing front attach point  236  and at the wing rear attach point  238 . The wing lugs  234  of one wing  200  are spaced apart complementary to the wing lugs  234  of the opposite wing  200 . The wing lugs  234  of the opposing wings  200  are configured to be rotatably coupled via one or more pins  384 , similar to the pins described above for a pinned joint  386  configuration of the strut-fuselage joint  304 . In the example shown, the wing-wing joint  208  includes a separate pin  384  at the wing front attach point  236 , and a separate pin  384  at the wing rear attach point  238 . The pins  384  allow the wings  200  to pivot in response to various loading conditions, while resisting the tension load  602  in the wing front spars  220 , the compression load  604  in the wing rear spars  222 , and the vertical moment M z  resulting from the lifting force  600  on each wing  200 . 
     Referring to  FIG.  117   , shown is a method  700  of enhancing the performance of an aircraft  100  configured as shown in  FIGS.  1 - 116   . Step  702  of the method  700  includes generating, using a wing  200 , a lifting force  600  when air passes over the wing  200 . As described above, each wing  200  of the aircraft  100  is coupled to the fuselage  102  at a wing-fuselage joint  204 , and each wing  200  is supported by a strut  300  coupled to the fuselage  102  at a strut-fuselage joint  304  located below and at least partially aft of the wing-fuselage joint  204 , as shown in  FIGS.  10  and  12   , and described above. 
     Step  704  of the method  700  includes the wing-strut arrangement inducing a vertical moment M z  about the wing-fuselage joint  204  in response to the lifting force  600 . As described above, the lifting force  600  is generated as a result of air moving over the wing  200 . The vertical moment M z  is created due to the non-parallel relationship between the wing axis  212  and the strut axis  312  ( FIG.  20   ), and tends to urge the wing  200  to pivot in an aftward direction. 
     Step  706  of the method  700  includes counteracting the vertical moment M z  using the structural arrangement of the wing  200  and/or using the structural arrangement of the strut  300 . In some examples, counteracting the vertical moment M z  comprises counteracting a portion of the vertical moment M z  using the structural arrangement of the wing  200 , and counteracting a portion of the vertical moment M z  using the structural arrangement of the strut  300 . The combination of the vertical moment M z  counteracted by the wing  200  and the vertical moment M z  counteracted by the strut  300  is equivalent to the total magnitude of the vertical moment M z . 
     The above-described  FIGS.  29 - 32    illustrate a structural arrangement wherein the wing  200  and the strut  300  are each configured as a cantilevered beam  320  capable of resisting a portion of the vertical moment M z . In another example,  FIGS.  51 - 54    illustrate a structural arrangement wherein the wing  200  has a wing A-frame structure  252 , and the strut  300  has a strut A-frame structure  322 . The combination of the wing A-frame structure  252  and the strut A-frame structure  322  defines a double tetrahedron structure, and each of the wing A-frame structure  252  and the strut A-frame structure  322  is capable of resisting a portion of the vertical moment M z . 
     In some examples, step  706  comprises counteracting substantially equivalent portions (e.g., 50 percent) of the vertical moment M z  using the wing  200  and the strut  300 . In other examples, step  706  comprises counteracting more than 50 percent of the vertical moment M z  using the strut  300 , and counteracting a remaining portion of the vertical moment M z  using the wing  200 . Referring to the example of  FIGS.  21 - 24   , step  706  of counteracting the vertical moment M z  comprises carrying tension load  602  and bending load in the strut  300 , which is configured as a single cantilevered beam  320  fixedly coupled to the fuselage  102  at the strut-fuselage joint  304 . 
     Referring to  FIGS.  37 - 40   , step  706  of counteracting the vertical moment M z  comprises carrying tension load  602  and compression load  604  respectively in the strut front spar  326  and the strut rear spar  328  of the above-mentioned strut A-frame structure  322 . As described above, the strut front spar  326  and strut rear spar  328  each have a strut spar inboard end  408  and a strut spar outboard end  410 . The strut spar outboard ends  410  converge at the strut-wing joint  306 , and the strut spar inboard ends  408  are spaced apart from each other at the strut-fuselage joint  304 . Step  706  additionally includes transferring the tension load  602  and the compression load  604  into the fuselage  102  at the strut front attach point  400  and the strut rear attach point  402  of the strut-fuselage joint  304 . 
     Referring still to the arrangement shown in  FIGS.  37 - 40   , the method  700  further comprises reacting shear load at the strut-fuselage joint  304  (e.g., at the strut front attach point  400  and the strut rear attach point  402 ) using an inboard end connector  330  interconnecting the strut spar inboard ends  408 . As described above, the shear reaction results from the tension load  602  and the compression load  604  in the strut front spar  326  and the strut rear spar  328 . As shown schematically in  FIG.  40   , the step of transferring the shear reaction into the fuselage  102  comprises reacting the shear load at a single location along the inboard end connector  330 . 
     Referring to the arrangement of  FIGS.  42 - 43   , the steps of carrying the tension load  602  and carrying the compression load  604  comprise, carrying the tension load  602  and the compression load  604  respectively in the strut front spar  326  and the strut rear spar  328  of the strut  300  having a strut leading edge  314  and a strut trailing edge  316 . As shown in the figures, the strut front spar  326  and the strut rear spar  328  each extend from the strut root  302  at the strut-fuselage joint  304 , to the strut outboard end  310  at the strut-wing joint  306 . As described above, the strut leading edge  314  and the strut trailing edge  316  define a tapered shape of the strut  300  from the strut root  302  to the strut outboard end  310 . As shown in  FIG.  42   , the tapered shape is complementary to the A-frame structure of the strut front spar  326  and the strut rear spar  328 . At least a portion of the strut leading edge  314  is aft of a wing trailing edge  216  of the wing  200 . 
     Referring to the arrangement of  FIGS.  65 - 66   , the steps of carrying the tension load  602  and carrying the compression load  604  respectively comprise carrying the tension load  602  and the compression load  604  respectively in the strut front spar  326  and the strut rear spar  328 , each of which is contiguous, and each has at least one kink  414  dividing the strut front spar  326  and the strut rear spar  328  into a strut spar inboard section  416  and a strut spar outboard section  418 . As described above, the strut spar inboard section  416  of the strut front spar  326  is angled forwardly relative to the strut spar outboard section  418  of the strut front spar  326 , and the strut spar inboard section  416  of the strut rear spar  328  is angled aftwardly relative to the strut spar outboard section  418  of the strut front spar  326 , to thereby increase the distance between the strut spar inboard ends  408 . 
     Referring still to  FIGS.  65 - 66   , carrying the tension load  602  and carrying the compression load  604  respectively comprise distributing the tension load  602  and the compression load  604  respectively into the strut front attach point  400  and the strut rear attach point  402  using a kink connector beam  422 , a kink plate  420 , and/or a pair of diagonal members  424 . As shown and described above, the kink connector beam  422  extends between and interconnects the kinks  414  respectively of the strut front spar  326  and the strut rear spar  328 . The kink plate  420  extends between and interconnects the strut spar inboard section  416  of the strut front spar  326  to the strut spar inboard section  416  of the strut rear spar  328 . Each one of the diagonal members  424  extends from one of the strut spar inboard ends  408  of one of the strut spars  326 ,  328 , to the kink  414  of the remaining strut spar  326 ,  328 . 
     Referring to the arrangement of  FIGS.  72 - 73   , the method  700  may further include distributing the tension load  602  into the strut front attach point  400  using a strut front fitting  434  extending forward of, and coupled to, the strut front spar  326  proximate the strut root  302 . In addition, the method  700  may include distributing the compression load  604  into the strut rear attach point  402  using a strut rear fitting  436  extending aft of, and coupled to, the strut rear spar  328  proximate the strut root  302 . As described above, the steps of distributing the tension load  602  and distributing the compression load  604  are respectively performed by the strut front fitting  434  and the strut rear fitting  436  configured as plates. In the example of  FIG.  73   , the plates of the strut front fitting  434  and the strut rear fitting  436  are located at the neutral axis respectively of the strut front spar  326  and the strut rear spar  328 . 
     Referring to the arrangement of  FIGS.  74 - 76   , the steps of distributing the tension load  602  and distributing the compression load  604  are respectively performed by the strut front fitting  434  and the strut rear fitting  436  extending between and interconnecting the upper cap  350  and the lower cap  352  respectively of the strut front spar  326  and the strut rear spar  328 . As described above, the strut front spar  326  and the strut rear spar  328  each have a channel-shaped cross-section in which the upper cap  350  and the lower cap  352  are interconnected by a web. As shown in  FIG.  76   , the strut front fitting  434  is nested within the channel-shaped cross-section of the strut front spar  326 , and is mechanically fastened to the strut front spar  326 . The strut rear fitting  436  is coupled to the strut rear spar  328  in a similar manner. 
     For the arrangement of  FIGS.  74 - 76   , the method  700  further comprises distributing the tension load  602  into the strut front attach point  400 , and distributing the compression load  604  into the strut rear attach point  402 , using a lug plate  372  insertable within a spar slot  370  in the strut front spar  326  and the strut rear spar  328 . As described above, the lug plate  372  interconnects the strut front spar  326  and the strut rear spar  328 . To increase the spacing between the strut front attach point  400  and strut rear attach point  402 , the lug plate  372  extends forward of the strut front spar  326 , and aft of the strut rear spar  328 . The lug plate  372  has one or more strut lugs  376  located forward of the strut front spar  326 , and one or more strut lugs  376  located aft of the strut rear spar  328 . The strut lugs  376  are rotatably coupled, via one or more pins  384 , to a plurality of fuselage lugs  110  protruding from the fuselage  102  at the strut front attach point  400  and the strut rear attach point  402 , as shown in  FIGS.  84 - 85    and described above. 
     Referring to  FIGS.  67 - 68   , in an alternative structural arrangement of the strut A-frame structure  322 , step  706  of counteracting the vertical moment M z  comprises carrying tension load  602  and compression load  604  respectively in a strut leading edge member  426  and a strut trailing edge member  428  respectively defining the strut leading edge  314  and the strut trailing edge  316  of the strut  300 . As shown in the above-described  FIG.  68   , the strut leading edge member  426  and the strut trailing edge member  428  are interconnected by the strut upper skin panel  358  and the strut lower skin panel  360 . As shown in  FIG.  67   , the strut leading edge member  426  and the strut trailing edge member  428  each have a strut member inboard end  430  and a strut member outboard end  432 . The strut member inboard ends  430  are spaced apart from each other at the strut-fuselage joint  304 , and the strut member outboard ends  432  converge at the strut-wing joint  306 . Referring to  FIGS.  69 - 70    showing  200  a still further structural arrangement of the strut A-frame structure  322 , the steps of carrying the tension load  602  and carrying the compression load  604  respectively comprise carrying the tension load  602  and carrying the compression load  604  using reinforcing fibers  356  (e.g., boron fibers) extending continuously between the strut root  302  and the strut outboard end  310  of the strut front spar  326  and the strut rear spar  328 . 
     As an alternative to the pinned joint  386  of  FIGS.  84 - 85   , the steps of transferring the tension load  602  and transferring the compression load  604  respectively comprise transferring the tension load  602  and transferring the compression load  604  via a fixed joint  388 , coupling the strut  300  to the fuselage  102  at the strut front attach point  400  and the strut rear attach point  402 . Transferring the tension load  602  and transferring the compression load  604  are performed via a strut end plate  380 . As described above, the strut end plate  380  is coupled to the strut spar inboard end  408  of the strut front spar  326  or the strut rear spar  328 . In the example shown, the strut end plate  380  is attached to the fuselage  102  via mechanical fasteners  382 . 
     Referring to the example of the strut-wing joint  306  shown in  FIGS.  94 - 107   , the method  700  further comprises transferring the tension load  602  and the compression load  604  into the wing  200  using a front spar plate  438  and a rear spar plate  440  respectively extending from the strut front spar  326  and the strut rear spar  328 . As described above, the front spar plate  438  and rear spar plate  440  are coupled together in overlapping relation. The front spar plate  438  and the rear spar plate  440  each have one or more strut lugs  376  protruding in an outboard direction. The method  700  additionally includes resolving, via the front spar plate  438  and the rear spar plate  440 , the tension load  602  and the compression load  604  respectively in the strut front spar  326  and strut rear spar  328  into axial tension transmitted into a plurality of wing lugs  234 . As described above, the wing lugs  234  protrude in an inboard direction, and are rotatably coupled to the strut lugs  376  via a pin  384 . The resolution of the tension load  602  and compression load  604  respectively in the strut front spar  326  and strut rear spar  328  also includes transmitting shear between the wing  200  and strut  300  via at least one drag link. In the example shown, compression load  604  and tension load  602  are respectively transferred via the front drag link  444  and the rear drag link  446 . As shown in  FIG.  94   , the front drag link  444  and the rear drag link  446  are oriented in a forward-aft direction. The front drag link  444  and the rear drag link  446  couple the wing  200  respectively to the front spar plate  438  and the rear spar plate  440 . 
     Referring to  FIGS.  109 - 113   , the method  700  further comprises suppressing buckling of each strut  300  using a jury strut  500  extending between the strut  300  and the wing  200 . As described above, each jury strut  500  suppresses buckling of the strut  300  (i.e., the main strut) at high compression load. The step of suppressing the buckling of the strut  300  is performed with the jury strut  500  coupled to the strut  300  at a distance from the strut-fuselage joint  304  of approximately two-thirds of the distance between the strut-fuselage joint  304  and the strut-wing joint  306 . In some examples, suppressing the buckling of the strut  300  comprises suppressing lateral-torsional buckling of the strut  300  using the jury strut  500  having a jury strut  500  width that is at least as wide as the distance between the strut front spar  326  and the strut rear spar  328 . 
     Referring to  FIGS.  114 - 116   , the method  700  may comprise counteracting at least a portion of the vertical moment M z  using the wing  200 , by carrying tension load  602  and compression load  604  respectively in the wing front spar  220  and the wing rear spar  222 . As described above, the wing front spar  220  and the wing rear spar  222  each have a wing spar inboard end  230  at the wing-fuselage joint  204 . Each wing  200  includes a wing shear plate  232  interconnecting the wing spar inboard ends  230  of the wing front spar  220  and the wing rear spar  222 . The wing shear plates  232  each have protruding wing lugs  234  that are interconnected via a pinned joint  386  using one or more pins  384 . 
     Additional modifications and improvements of the present disclosure may be apparent to those of ordinary skill in the art. Thus, the particular combination of parts described and illustrated herein is intended to represent only certain examples of the present disclosure and is not intended to serve as limitations of alternative examples or devices within the spirit and scope of the disclosure.