ASSEMBLY FOR WARPING OF AN AERODYNAMIC STRUCTURE

Abstract

A spar assembly for an aircraft wing extends between an upper cover and a lower cover and includes linkages spaced consecutively along the length of the spar assembly, each linkage extending from an upper pivot, to a lower pivot, thereby joining upper and lower attachment structures of the spar assembly together. Each linkage includes a pair of fixed-length links pivotably connected at one end about a center pivot and pivotably connected at respective other ends. The spar assembly includes a drive bar connected to the center pivot of each of the linkages, and an actuator arranged to move the drive bar along the length of the spar assembly. When the actuator moves the drive bar along the length of the spar structure, the links in each pair of links are rotated relative to each other about the center pivot, thereby moving the upper and lower covers and warping the wing.

Claims

1. An aircraft wing comprising: an upper cover; a lower cover; and a spar assembly extending between the upper cover and the lower cover, wherein the spar assembly comprises: an upper attachment structure connected to the upper cover, a lower attachment structure connected to the lower cover; and a multiplicity of linkages spaced along a length of the spar assembly, each of the linkages extending from an upper pivot on the upper attachment structure, to a lower pivot on the lower attachment structure, thereby joining the upper and lower attachment structures together, wherein each of the linkages is adjustable to alter a distance between the upper and lower pivots, thereby enabling the wing to be warped.

2. The wing according to claim 1, wherein each of the linkages comprises: a first link connected, at one end, to the upper pivot; and a second link connected, at one end, to the lower pivot; wherein the first and second links are pivotably connected together at a third pivot; and wherein each linkage is adjustable, by adjusting a position of the third pivot, to alter the distance between the upper and lower pivots.

3. The wing according to claim 2, wherein the spar assembly comprises a drive bar connected to the third pivot of each of the multiplicity of linkages, and the wing comprises an actuator arranged to move the drive bar, such that the actuator can simultaneously adjust the position of the multiplicity of third pivots.

4. The wing according to claim 2, wherein each linkage is adjustable, by adjusting the position of the third pivot within a range of positions, and wherein the range of positions includes a position in which the first, second and third pivots are substantially in line.

5. The wing according to claim 2, wherein each pair of first and second links is associated with a third link, the third link extending from the lower pivot to a fourth pivot, the fourth pivot being on the upper attachment structure.

6. The wing according to claim 5, wherein the fourth pivot is coincident with an upper pivot of an adjacent linkage.

7. A wing according to claim 1, wherein the spar assembly is a first spar assembly located along a relatively forward or rearward part of the upper and lower covers, and the wing further comprises a second spar assembly, located along another of the forward or rearward part of the covers.

8. A spar assembly for use as the spar assembly according to claim 1.

9. An aircraft comprising the aircraft wing according to claim 1.

10. A method of warping a wing on an aircraft, the method comprising: actuating a multiplicity of linkages in a spar assembly from a first configuration to a second configuration, each linkage extending from an upper pivot on an upper attachment structure of the spar assembly, to a lower pivot on a lower attachment structure of the spar assembly, thereby joining the upper and lower attachment structures together, whereby in the first configuration, the first and second pivots are at a first spacing from each other, and in the second configuration the first and second pivots are at a second, different, spacing from each other, thereby warping the wing.

11. The method according to claim 10, wherein each linkage comprises a first link connected, at one end, to the upper pivot and a second link connected, at one end, to the lower pivot, wherein the first and second links are pivotably connected together at a third pivot; and wherein to move from the first configuration to the second configuration, a position of the third pivot is adjusted, so as to alter spacing between the upper and lower pivots.

12. A spar assembly for extending between an upper cover and a lower cover on an aircraft wing, the spar assembly comprising: an upper attachment structure for connecting to the upper cover; a lower attachment structure for connecting to the lower cover; and a multiplicity of linkages spaced consecutively along a length of the spar assembly, each of the linkages extending from an upper pivot on the upper attachment structure, to a lower pivot on the lower attachment structure, thereby joining the upper and lower attachment structures together, wherein each of the linkages comprises: a pair of fixed-length links, substantially in-line with one another, and pivotably connected together at one end about a center pivot and pivotably connected to the upper and lower attachment structures at their respective other ends, and wherein the spar assembly further comprises a drive bar connected to the center pivot of each of the multiplicity of linkages, and an actuator arranged to move the drive bar along the length of the spar assembly, such that when the actuator moves the drive bar along the length of the spar structure, the links in each pair of links are rotated relative to each other about the center pivot, away from thereby altering a longitudinal offset between the upper and lower attachment structures.

13. An aerodynamic structure comprising: a first cover; a second cover; and a shear-resisting assembly extending between the first cover and the second cover, wherein the shear-resisting assembly comprises: first attachment structure connected to the first cover; a second attachment structure connected to the second cover; and a multiplicity of linkages spaced along a length of the shear-resisting assembly, each of the linkages extending from a first pivot on the first attachment structure, to a second pivot on the second attachment structure, thereby joining the first and second attachment structures together, wherein each of the linkages is adjustable to alter a distance between the first and second pivots, thereby enabling the aerodynamic structure to be warped.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Embodiments of the disclosure herein will now be described by way of example only with reference to the accompanying schematic drawings of which:

[0032] FIG. 1 shows an aircraft having a wing with a spar assembly according to a first embodiment of the disclosure herein;

[0033] FIG. 2 shows a schematic view of the outer part of the wing of the aircraft in FIG. 1, showing the difference between the wing in an unwarped and a warped configuration;

[0034] FIG. 3 shows a partial cut-way view of part of the outer wing in the aircraft of FIG. 1;

[0035] FIG. 4a shows a frontal view of part of the front spar-assembly in the aircraft of FIG. 1, when the assembly is in the unwarped configuration;

[0036] FIG. 4b shows the part of the front spar-assembly in FIG. 4a, when the assembly is in the warped configuration;

[0037] FIG. 5 shows a close up view of a third pivot in one of the linkages in FIG. 4b, and the forces acting on the pivot; and

[0038] FIG. 6 is a graphic showing the warping of part of the wing in the warped configuration.

DETAILED DESCRIPTION

[0039] FIG. 1 shows an aircraft 1 having a fuselage 3, wings 5 and empennage 7. In the embodiment shown, the outer part of each wing 5 is lacking ailerons. Instead, each wing 5 comprises a spar assembly according to a first embodiment of the disclosure herein. The spar assembly is configured to warp the wing between an unwarped and a warped configuration, thereby enabling control of the aircraft flight. This wing warping will now be described in detail.

[0040] Referring first to FIG. 2, this shows a schematic view of the outer 20% of one of the wings 5 of the aircraft 1, showing the difference between the wing in the unwarped and the warped configurations. This part of the wing 5 can be divided into three notional sections arranged in series: a fixed root portion 5a (which extends back to the fuselagenot visible in FIG. 2), a warping section 5b outboard of the fixed root, and a static twist section 5c outboard of the warping section 5b. Each section is a continuation of the adjacent section (i.e. continuations of the leading edge, trailing edge and upper and lower surfaces) and does not comprise any discrete control surface such as an aileron.

[0041] FIG. 2 illustrates the change in aerofoil orientation between the unwarped configuration (aerofoils labelled 9a and shown in light-coloured lines) and the warped configuration (aerofoils labelled 9b and shown in dark coloured lines). It can be seen from comparing the aerofoil sections at different positions along the wing, that within the warping section 5b, the aerofoil orientations 9b in the warped configuration diverge from those of the unwarped aerofoil orientation 9a. By warping the outer part of the wing 5 in this manner, the lift distribution on the wing is changed, and the flight of the aircraft 1 may be controlled without the use of ailerons or other discrete control surfaces.

[0042] The spar assembly that is used to effect the above-mentioned warping is shown in, and is now described with reference to, FIGS. 3-6.

[0043] FIG. 3 is a partial cut-way view of the warping section 5b in the wing 5 of the aircraft 1. The warping section 5b comprises an upper cover 11 and a lower cover 13. The upper and lower covers are joined by leading and trailing edge panels, but for the sake of clarity, these are not shown in FIG. 3. A front spar assembly 15 extends along the front edge of the covers and a rear spar assembly 17 extends along the rear edge of the covers. Ribs 19 extend fore-aft between the front and rear spars, and stringers 21 extending along the underside of the upper and lower wing covers 11, 13. The front and rear spar assemblies 15, 17 are substantially identical, so for brevity only the front spar assembly 15 is described herein in detail. It will be appreciated, of course, that features of the front spar assembly 15 can equally be applied to the rear spar assembly 17.

[0044] References herein to directions/orientations of the spar assembly are, unless otherwise specified, made in a local reference frame in which the longitudinal direction L extends along the spar assembly, the height H extends through the depth of the wing between the lower and upper covers, and the width W extends from front to back of the spar assembly. It will be appreciated that this is akin to a typical Cartesian reference frame for an aircraft, but oriented to take into account the sweep and/or dihedral of the wing 5.

[0045] FIG. 3 only shows the linkages in the spar assemblies schematically. However, FIG. 4a shows a frontal view of part of the front spar-assembly 15 in more detail. The spar assembly 15 extends between the upper cover 11 and the lower cover 13. An upper attachment structure 23 is attached to the underside of upper cover. On its opposing side, the attachment structure 23 comprises a series of lugs 25 protruding into the interior of the wing 5. A similar, lower, attachment structure 27 is attached to the underside of lower cover. On its inward side, the lower attachment structure 27 also comprises a series of lugs 29 protruding into the interior of the wing 5.

[0046] The spar assembly 15 comprises a multiplicity of linkages 31 spaced along the length L of the spar assembly 15. Each linkage comprises a first link 33 connected, at one end, to an upper pivot 33a on a respective lug 25 of the upper attachment structure 23; and a second link 35 connected, at one end, to a lower pivot 35a on a respective lug 29 of the lower attachment structure 27. These two links 33, 35 are also pivotably connected together at their opposing ends at a third pivot 37. In the configuration shown in FIG. 4a, it will be appreciated that the first and second links are substantially in-line with one anotherdiscussed in more detail below. The first and second links extend at approximately 45 degrees to the longitudinal direction.

[0047] Each linkage 31 also comprises a third link 39. The third link is oriented just below 90 degrees from the longitudinal axis and extends from the lower pivot 35a, to the upper pivot 33a of the adjacent linkage. The linkages 31 are thus arranged consecutively along the length of the spar assembly structure and share common pivot axes.

[0048] A straight drive bar 41 extends along the centerline of the linkages in a longitudinal direction along the spar assembly. The drive bar connects together all of the third (center) pivots joining the two links 33, 35 of each linkage. The drive bar 41 is also connected at one end to a linear actuator 43. In the unwarped configuration, shown in FIG. 4a, the actuator 43 is un-extended.

[0049] During flight, in the unwarped configuration, the spar assembly is primarily subjected to relative shear loadings between the upper and lower covers. For example, the upper cover tends to be urged inboard (to the left in FIG. 4a) and the lower cover tends to be urged outboard (to the right in FIG. 4b). Each of the links 33 and 35 tend to therefore be in tension (or would be in compression under the opposite shear loading).

[0050] The third link 39 acts to brace the spar assembly structure and prevents the upper and lower attachment structures collapsing in towards each other.

[0051] Since the two links are in line and their centerline runs through the third pivot, tensile/compressive forces acting on the third pivot balance and substantially no load is transferred along the drive bar and into the actuator. The spar assembly of the first embodiment of the disclosure herein therefore enables flight loads to be readily reacted into the wing structure rather than necessarily requiring an actuator that can withstand such flight loads.

[0052] FIG. 4b shows the spar assembly of FIG. 4a but with the actuator 43 extended. When the actuator is extended, the third pivots 37 of the linkages 31 are all displaced in a longitudinal direction approximately 10 mm. This movement breaks the inline arrangement of the pair of links 33, 35 and they rotate relative to each other such that the included angle between the links is around 160 degrees. Since the links are of a fixed length, this movement necessarily moves the upper attachment structure longitudinally relative to the lower attachment structure, resulting in a reduction in the distance (longitudinal spacing) between the upper and lower pivots (i.e. an offset of the upper wing cover from the lower wing cover). For ease of comparison, FIG. 4b shows dashed vertical lines illustrating the location of the ends of the upper cover in the unwarped configuration in FIG. 4a.

[0053] In this configuration, the upper link 33 and the lower link 35 are in tension. The spar assembly of the first embodiment is beneficial in two ways in dealing with these loads: Firstly, since the spar assembly comprises a multiplicity of linkages, there is mechanical advantage (lever arm) between the pivot at which the actuator acts and the upper and lower attachment structures. This allows the actuator to be relatively low capacity (in comparison with there being no mechanical advantage and a need to act directly on the upper cover).

[0054] Secondly, the upper and lower links remain relatively close to their inline orientation. The majority of the flight loads transferred along the links are therefore still transferred directly into the wing structure. The component in a direction along the length of the drive bar (i.e. into the actuator) is relatively small. FIG. 5 shows a force diagram indicating the forces acting along the drive bar when the wing is experiencing flight loads in the warped configuration. In the example in FIG. 5, the flight loads are urging the upper cover inboard (to the left in FIG. 4b) and the lower cover is being urged outboard (to the right in FIG. 4b). The upper link and lower links 33, 35 are therefore under tension. In this example, the angles of the upper and lower links 33, 35 from the longitudinal direction are relatively similar, so the net force F.sub.DB acting in a direction along the drive bar is relatively low because angles and are of relatively similar magnitude. This enables use of a relatively low capacity actuator.

[0055] To warp the wing, the actuators 43 on the front and rear spar assemblies 15, 17 are actuated to move the links in the manner shown in FIG. 4b. The relative longitudinal movement between the upper and lower covers 11, 13 along the front and back of the wing can be tailored to create a twisting action about a twist axis of the wing, thereby warping the upper and lower covers to which the spar assemblies are attached.

[0056] As will be understood from FIGS. 4a and 4b and the explanation above, the spar assembly in the first embodiment is stiff when it is holding the wing in the unwarped configuration (FIG. 4a). The box beam (formed between the ribs, spar assemblies and covers) is a closed section and therefore of very high torsional stiffness. While the spar assembly is able to be actuated to warp the wing (see above), the spar assembly returns to a stiff structure once actuation has been completed and the box beam therefore retains it high torsional stiffness for flight loading.

[0057] FIG. 6 is a schematic showing the twist of the warping section 5b of the wing 5. The darker shading represents low displacement from the unwarped configuration, and the lighter shading represents higher displacement from the unwarped configuration. A twist of 9 degrees was obtained using an actuation force on the front and rear spar assemblies of 6 kN (when actuated without flight loads). An end-on view through A-A is also shown to illustrate the twist of the wing about a neutral twist axis.

[0058] Referring back to FIG. 2, the wing comprises a constant twist section 5c attached to the end of the warping section 5b in which the spar assemblies are present. The static section does not itself twist, but instead extends from the end of the warping action at the respective twist angle of that end. Likewise at the inner end, the warping section is attached to the fixed root portion, which effectively acts as a zero twist datum for the warping section. The spar assembly of the first embodiment of the disclosure herein is therefore only used along a relatively short section of the wing. It will be appreciated that in other embodiments, a spar assembly may be used along a longer or shorter length of the wing as appropriate.

[0059] While the disclosure herein has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the disclosure herein lends itself to many different variations not specifically illustrated herein. For example, the spar assembly may have a second actuator at the other end of the drive bar. The second actuator may be a back-up actuator in the event of failure of the primary actuator. The spar assembly may be a shear resisting assembly in another part of the aircraft, such as a rudder or elevator. In another embodiment, not shown, the first and second links are angled relative to one another in the unwarped configuration and move towards the in-line arrangement to warp the wing.

[0060] Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the disclosure herein, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the disclosure herein that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, while of possible benefit in some embodiments of the disclosure herein, may not be desirable, and may therefore be absent, in other embodiments.

[0061] While at least one example embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms comprise or comprising do not exclude other elements or steps, the terms a, an or one do not exclude a plural number, and the term or means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.