Aircraft wing with wing tip device

Abstract

An aircraft wing assembly including: a wing having a wing box structure with an upper wing cover and a lower wing cover, and a wing tip device attached to the outboard end of the wing, the wing tip device including an upper cover and a lower cover, wherein a gap between opposing edges of the wing tip device lower cover and the lower wing cover is at least 5 mm, a seal assembly aerodynamically seals the gap, wherein the seal assembly includes a bridging component on an interior side of the gap, and a seal which fills the gap and is supported by the bridging component.

Claims

1. An aircraft wing assembly comprising: a wing having a wing box structure including an upper wing cover and a lower wing cover; a wing tip device attached to an outboard end of the wing, the wing tip device including an upper cover and a lower cover, wherein a gap between opposing edges of the wing tip device lower cover and the lower wing cover is at least 5 mm; and a seal assembly configured to aerodynamically seal the gap, wherein the seal assembly includes a bridging portion extending across an interior side of the gap to bridge the gap, and a seal portion which projects from the bridging portion to fill the gap, wherein the bridging portion comprises an inboard flange which extends inboard of the edge of the lower wing cover and an outboard flange which extends outboard of the edge of the wing tip device lower cover; wherein the seal assembly includes a retaining portion fixed to the seal portion and extending across an exterior side of the gap to retain the seal portion within the gap, and wherein at least a part of the retaining portion comprises a stiffer material than the seal portion.

2. The aircraft wing assembly according to claim 1 wherein the seal assembly is self-retaining.

3. The aircraft wing assembly according to claim 1, wherein the inboard flange abuts an interior surface of the lower wing cover, and the outboard flange abuts an interior surface of the wing tip device lower cover.

4. The aircraft wing assembly according to claim 3, wherein the seal portion abuts the edge of the wing tip device lower cover, and at least a portion of the bridging portion and the seal portion are formed as a single component.

5. The aircraft wing assembly according to claim 4 wherein the outboard flange of the bridging portion and the seal portion are formed as a single component.

6. The aircraft wing assembly according to claim 1, wherein the retaining portion comprises an inboard flange which abuts an exterior surface of the lower wing cover, and an outboard flange which abuts an exterior surface of the wing tip device lower cover.

7. The aircraft wing assembly according to claim 1 wherein a side face of the seal assembly that is adjacent to an end face of the lower wing cover has a different thickness to a side face of the seal assembly that is adjacent to an end face of the wing tip device lower cover.

8. The aircraft wing assembly according to claim 1 wherein at least one of the inboard and outboard flanges of the bridging portion has a ramped surface abutting a corresponding ramped surface of the lower wing cover or wingtip device lower cover respectively.

9. The aircraft wing assembly according to claim 1, wherein the gap is at least 10 mm.

10. The aircraft wing assembly according to claim 1, wherein the wing tip device is attached to the outboard end of the wing by a joint, which includes a pinned lug joint.

11. The aircraft wing assembly according to claim 10, wherein the joint further includes a tension joint between abutting components.

12. The aircraft wing assembly according to claim 11, wherein, within the joint, the tension joint is disposed nearest the upper wing cover and the pinned lug joint is disposed nearest the lower wing cover.

13. The aircraft wing assembly according to claim 1, wherein the wing tip device includes an essentially planar winglet and a curved transition region arranged between the wing and the winglet.

14. The aircraft wing assembly according to claim 1, wherein the transition region has a curvature of increasing local dihedral in the outboard direction.

15. The aircraft wing assembly according to claim 1, wherein the wing tip device is removable.

16. An aircraft including the wing assembly of claim 1.

17. The aircraft wing assembly according to claim 1, wherein at least a part of the bridging portion comprises stiffer material than the seal portion.

18. A method of attaching a wing tip device to an outboard end of an aircraft wing, the wing having a wing box structure including an upper wing cover and a lower wing cover, and the wing tip device having an upper cover and a lower cover, the method comprising: bringing the wing tip device and the wing together; joining the wing tip device to the outboard end of the wing, wherein a gap between opposing edges of the wing tip device lower cover and the lower wing cover is at least 5 mm at completion of the joint; and installing a seal assembly to aerodynamically seal the gap, wherein the seal assembly includes a bridging portion arranged to extend across an interior side of the gap to bridge the gap, and a seal portion projecting from the bridging portion to fill the gap, wherein the bridging portion comprises an inboard flange arranged to extend inboard of the edge of the lower wing cover and an outboard flange arranged to extend outboard of the edge of the wing tip device lower cover, wherein the seal assembly includes a retaining portion fixed to the seal portion and arranged to extend across an exterior side of the gap to retain the seal portion within the gap, and the step of installing the seal assembly includes sliding the seal assembly along the gap with the bridging portion at the interior side of the gap, the seal portion within the gap and the retaining portion at the exterior side of the gap, and wherein at least a part of the retaining portion comprises a stiffer material than the seal portion.

19. The method according to claim 18 wherein the wing tip device is rotated with respect to the wing.

20. The method according to claim 18, wherein the step of joining the wing tip device to the outboard end of the wing includes forming a pinned lug joint.

21. The method according to claim 20 wherein the wing tip device is rotated with respect to the wing.

22. The method according to claim 18 wherein the inboard flange abuts an interior surface of the lower wing cover, and the outboard flange abuts an interior surface of the wing tip device lower cover, wherein the seal portion abuts the edge of the wing tip device lower cover, and at least a portion of the bridging portion and the seal portion are formed as a single component.

23. The method according to claim 22 wherein the outboard flange of the bridging portion and the seal portion are funned as a single component.

24. The method according to claim 18, wherein at least a part of the bridging portion comprises stiffer material than the seal portion.

25. An aircraft wing assembly comprising: a wing having a wing box structure including an upper wing cover and a lower wing cover; a wing tip device attached to an outboard end of the wing, the wing tip device including an upper cover and a lower cover, wherein a gap between opposing edges of the wing tip device lower cover and the lower wing cover is at least 5 mm; and a seal assembly configured to aerodynamically seal the gap, wherein the seal assembly includes a bridging portion extending across an interior side of the gap to bridge the gap, and a seal portion which projects from the bridging portion to fill the gap, wherein the bridging portion comprises an inboard flange which extends inboard of the edge of the lower wing cover and an outboard flange which extends outboard of the edge of the wing tip device lower cover, wherein at least a part of the bridging portion comprises stiffer material than the seal portion.

26. A method of attaching a wing tip device to an outboard end of an aircraft wing, the wing having a wing box structure including an upper wing cover and a lower wing cover, and the wing tip device having an upper cover and a lower cover, the method comprising: bringing the wing tip device and the wing together; joining the wing tip device to the outboard end of the wing, wherein a gap between opposing edges of the wing tip device lower cover and the lower wing cover is at least 5 mm at completion of the joint; and installing a seal assembly to aerodynamically seal the gap, wherein the seal assembly includes a bridging portion arranged to extend across an interior side of the gap to bridge the gap, and a seal portion projecting from the bridging portion to fill the gap, wherein the bridging portion comprises an inboard flange arranged to extend inboard of the edge of the lower wing cover and an outboard flange arranged to extend outboard of the edge of the wing tip device lower cover, wherein at least a part of the bridging portion comprises stiffer material than the seal portion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

(2) FIG. 1 illustrates a view looking aft of an aircraft having a wing assembly including a wing tip device attached to the outboard end of the aircraft wing;

(3) FIG. 2 illustrates the outboard end of the aircraft wing assembly in detail;

(4) FIG. 3 illustrates a partial section view of a combined tension joint and pinned lug joint for attaching the wing tip device to the outboard end of the wing;

(5) FIG. 4 illustrates a cut away view of the wing box rib at the outboard end of the wing, which forms part of the combination joint illustrated in FIG. 3;

(6) FIG. 5 illustrates detail A of FIG. 3 showing a seal assembly for aerodynamically sealing the gap between opposing edges of the wing tip device lower cover and the lower wing cover, in which the seal assembly includes a bridging component and a seal comprising sealant material;

(7) FIG. 6 illustrates a three dimensional view of the bridging component of the seal assembly;

(8) FIG. 7 illustrates an alternative seal assembly including a seal strip received in a profile formed in an alternative bridging component and with sealant material in-fill;

(9) FIG. 8 shows a schematic view of an alternative seal assembly according to another embodiment of the invention;

(10) FIG. 9 shows an isometric view of the seal assembly of FIG. 8;

(11) FIG. 10 shows a top view of the seal assembly of FIGS. 8 and 9;

(12) FIG. 11 shows a side view of the seal assembly of FIGS. 8 and 9;

(13) FIGS. 12A and 12C show cross-sectional views taken at line A-A shown in FIG. 11; and

(14) FIG. 12B shows a cross-sectional view taken at lines B-B and C-C shown in FIG. 11.

DETAILED DESCRIPTION OF EMBODIMENT(S)

(15) FIG. 1 illustrates a commercial jet aircraft including a wing assembly having a wing tip device 1 attached to the outboard end of a wing 2.

(16) FIG. 2 illustrates the outboard end of the wing assembly in detail. The wing tip device 1 is substantially as described in WO2008/061739A, the contents of which are incorporated herein by reference. The wing tip device 1 generally comprises a substantially planar winglet 3 and a transition region 4 arranged between the wing 2 and the winglet 3. The transition region 4 has a curvature of local dihedral that increases from a low angle, or an angle of approximately zero, at or near the outboard end of the wing 2 and increases in the outboard direction. The winglet 3 extends upwardly from the transition region 4 and is inclined with respect to the vertical plane. In one example, the wing tip device 1 is approximately 2.5 meters tall and weighs approximately 120 kgs. The wing tip device 1 is used to reduce the induced drag on the wing leading to improved fuel efficiency and reduced carbon emissions.

(17) The aircraft wing 2 has a conventional wing box structure including a front spar, a rear spar, a plurality of ribs extending in a chordwise direction between the front and rear spars, and upper and lower wing covers which are attached to the front and rear spars and to the ribs.

(18) FIG. 3 illustrates a partial section view of a combination joint 5 used to attach the wing tip device 1 to the outboard end of the wing 2. The outboard end of the wing 2 includes an outboard wing rib 6 extending between the upper wing cover 7 and the lower wing cover 8. The outboard wing rib 6 has a generally C-shaped cross section. The transition region 4 of the wing tip device 1 includes an upper tip device cover 9 and a lower tip device cover 10. The wing tip device 1 further includes a plurality of ribs and the inboard rib 11 is shown in FIG. 3. The inboard rib 11 has a generally C-shaped cross section and is arranged back-to-back with the outboard wing rib 6. The ribs 6, 11 each have a substantially vertical web with oppositely facing upper and lower flanges.

(19) The combination joint 5 includes the outboard wing rib 6, the inboard wing tip device rib 11, an upper tension joint 12 and a lower pinned lug joint 13. The tension joint 12 comprises abutting surfaces of the ribs 6, 11 and a plurality of tension fittings 14. As best shown in FIG. 4, the tension joint 12 includes tension fittings 14 arranged spaced generally chordwise across the joint. Each tension fitting includes a tension bolt and a barrel nut. Each tension bolt is disposed within a through hole formed in the ribs 6, 11.

(20) The pinned lug joint 13 is disposed nearest the lower wing cover 8 offset below the horizontal centre line of the joint 5. The pinned lug joint 13 includes groups of lugs on both the wing side of the joint and on the wing tip device side of the joint. The groups of lugs on each side of the joint 13 are oppositely facing (inboard/outboard). Each lug includes a lug hole and a pin passes through the aligned lug holes of each of the groups of lugs. The pinned lug joint 13 effectively transfers the bending, yaw and shear loads generated by the wing tip device 1 into the wing 2 during flight.

(21) The wingtip device 1 is taller, heavier and generates significantly higher bending and yaw moments than conventional wingtip devices, e.g. a wingtip fence. The combination joint 5 is capable of transferring these higher bending and yaw moments, at the same time as the shear loading, over a relatively small area (less than 0.1 m2) available at the outboard end of the wing tip 2 for attaching the wing tip device 1.

(22) The use of a pinned lug joint 13 within the combination joint 5 is unusual for joining back-to-back ribs within an aerofoil structure but has been found to be highly efficient for transferring the higher bending and yaw moments generated by the wingtip device 1. However, the use of a pinned lug joint introduces difficulties during installation and removal of the wing tip device 1 from the outboard end of the wing 2. There is a risk that in moving the relatively larger and heavier wing tip device 1 into position with respect to the outboard end of the wing 2 there is the possibility of overshoot as the sets of lugs 15, 16, prior to pinning may, overshoot beyond the position where their respective lug holes come into alignment for insertion of the pins 17. This overshoot could be problematic as the lower wing cover 8 and the wing tip device lower cover 10 could clash causing damage to one or other of these components. Moreover, it may in fact be desirable to rotate the wing tip device 1 with respect to the wing 2 by a small angle (less than 5) during installation of the wing tip device 1 for ease of constructing the pinned lug joints 13.

(23) Accordingly, a larger than normal gap, g, is provided between opposing edges 18, 19 of the lower wing cover 8 and the wing tip device lower cover 10. This gap, g, is at least 5 mm wide and is preferably at least 10 mm wide but is generally less than 20 mm wide. This contrasts with a gap of approximately 2 mm which is found between the upper wing cover 7 and the wing tip device upper cover 9. For aerodynamic performance reasons, the gap, g, is required to be sealed after joining the wing tip device 1 to the wing 2.

(24) As best shown in FIG. 5, a seal assembly 20 is provided for aerodynamically sealing the gap, g, between the lower wing cover 8 and the wing tip device lower cover 10. The seal assembly 20 includes a bridging component 21 on an interior side of the gap, g, and a seal 22 which fills the gap, g, and is supported by the bridging component 21. The bridging component 21 has a generally T-shaped profile and includes an upright flange 23 adjacent the edge 19 of the wing tip device lower cover 10, an outboard flange 24 abutting the interior surface of the wing tip device lower cover 10, and an inboard flange 25 which extends to contact the interior surface of the lower wing cover 8. A three dimensional view of the generally T-shaped bridging component 21 is shown in FIG. 6. The bridging component 21 includes several cut outs along its length to accommodate various parts of the combination joint 5, depending on specific design requirements.

(25) The inboard flange 25 of the bridging component 21 includes a taper in the outboard direction so as to provide a relatively flexible contact edge with the interior surface of the lower wing cover 8. This accommodates tolerance in the thickness of the lower wing cover 8 and the wing tip device lower cover 10. The bridging component 10 is however substantially rigid to ensure the integrity of the seal assembly 20. The bridging component 21 may be made of rubber material, or any other suitable material.

(26) The seal 22 may be a curable aero sealant of conventional type. The cured sealant of the seal 22 is supported by the bridging component 21. The bridging component 21 is fixed to the wing tip device lower cover 10 prior to installation of the wingtip device 1 at the outboard end of the wing 2. Once the wingtip device 1 has been installed and joined to the outboard end of the wing 2 the seal 22 is formed so as to infill the cavity bounded by the bridging component 21 and the edge 18 of the lower wing cover 8 so as to complete the seal assembly 20. The volume of sealant material required to form the seal 22 may be such that successive beads of sealant material may need to be applied and cured prior to application of the subsequent layer of sealant material. The seal 22 may be formed so as to completely seal the gap, g, and provide a substantially flush outer aerodynamic surface between the outer surfaces of the lower wing cover 8 and the wingtip device lower cover 10.

(27) FIG. 7 illustrates an alternative seal assembly 20 in which the bridging component 21 includes a profile 26 which receives a seal strip 27. The seal strip 27 has a mating profile for cooperating with the profile 26. Aero sealant 28 is then applied to infill the remaining gaps around the seal strip 27 to complete the seal 22. The seal assembly shown in FIG. 7 is particularly advantageous where the gap, g, between the lower wing cover 8 and the wingtip device lower cover is large. The bridging component 21 may be fixed to the wing tip device lower cover 10 prior to installation of the wing tip device 1 on the outboard end of the wing 2 in the same manner as described above with reference to FIG. 5. The seal strip 27, which may be made of a rubber material or any other suitable material, can then be run along the profile 26 prior to infilling with the aero sealant 28. The reduced volume of aero sealant 28 in the embodiment shown in FIG. 7 may avoid any shrinkage issues which may be apparent with larger volumes of aero sealant and may reduce the time to cure.

(28) FIGS. 8-12 illustrate another alternative seal assembly 20. The seal assembly 20 includes a central seal portion 29 sandwiched between a bridging portion 21 and a retaining portion 30. The seal portion 29 has a generally rectangular cross-section and is sized so that it substantially fills the gap, g. It is formed in this embodiment from rubber reinforced with fabric, so that it is inherently flexible yet damage resistant and resilient.

(29) The bridging portion 21 comprises an outboard flange 21a which extends outboard from, and is formed integrally with, the seal portion 29. The outboard flange 21a has a generally triangular shaped cross-section, with a sloped face which abuts a sloping chamfered interior face of the wing tip lower cover 10 (see FIG. 8). The outboard flange 21a is formed from the same reinforced rubber material as the seal portion 29.

(30) Along a majority of the length of the seal assembly 20, but not at regions at the ends thereof (see FIGS. 11 and 12A-C), the bridging portion 21 also comprises an inboard flange 21b which extends inboard from the seal portion 29. The inboard flange 21b comprises a thin strip of glass fibre-reinforced composite material which is bonded to the seal member 29 so as to leave an overhanging region which forms the flange. As best seen in FIG. 8, the inboard flange 21b abuts an interior face of the lower wing cover 8. The strip of composite material which forms the inboard flange 21b serves both to increase the overall rigidity of the seal assembly 20, and to enhance the ability of the bridging portion 21 to retain the seal portion 29 within the gap, g.

(31) The retaining portion 30 comprises a thin strip of glass fibre-reinforced composite material which is fixed to the seal portion so as to overhang in both the inboard and outboard directions. The inboard overhang forms an inboard flange 30b which abuts an exterior surface of the lower wing cover 8, while the outboard overhang forms an outboard flange 30a which abuts an exterior surface of the wing tip device lower cover 10 (see FIG. 8). Like the inboard flange 21b of the bridging portion 21, the composite retaining portion 30 serves to increase the overall rigidity of the seal assembly 20, and thus to help retain the seal portion 29 within the gap, g.

(32) The bridging portion 21 and the retaining portion 30 thus act to retain the seal portion 29 in a position in which it fills the gap, g, as shown in FIG. 8.

(33) During installation the elongate seal assembly 20 is slid along the gap so that the seal portion 29 slides within the gap, the bridging portion 21 slides along an interior side of the gap, and the retaining portion 30 slides along an exterior side of the gap. Thus, one single process step of sliding the seal assembly 20 into its final position ensures that the seal portion 29, bridging portion 21 and retaining portion 30 are also in their final positions.

(34) A particular advantage of the embodiment of FIGS. 8-12 is that the seal assembly 20 is self-retaining, with there being no requirement to fix the bridging portion 21 or retaining portion 30 to the lower wing cover 8 or wing tip device lower cover 10 in order to retain the seal assembly 20 in place.

(35) The embodiments of the seal assembly described above are particularly advantageous over other means for sealing the gap, g, between the lower wing cover and the wing tip device lower cover. In particular, the seal assemblies described above provide benefits of low material and installation costs and ease of repair whilst providing a flush outer aerodynamic surface, ease of installation of the wing tip device 1 and protection for the wing tip device 1 during installation. Comparative seal assembly options are briefly described below.

(36) In a first comparative example, a seal assembly may include a profiled seal strip. The profiled seal strip is easy to manufacture and install but the profile may provide an undesirable aerodynamic step in the lower wing surface.

(37) In a second comparative example, a seal assembly may include a P-seal fixed with a retainer to the interior surface of the wing tip device lower cover. A disadvantage of the P-seal is that it can only be replaced by removing the wing tip device from the wing. Installation of the P-seal and potential adjustment of its position may be enhanced by providing a ramp on the interior surface of the wing tip device lower cover towards the gap. However, the ramped surface would increase the complexity of the wing tip device lower cover.

(38) In a third comparative example, the outer surface of the wing tip device lower cover may include a ramp towards the gap to accommodate a generally wedge shaped thin sealing plate, which may be fastened to the wing tip device lower cover. The increased manufacturing complexity of forming the ramp in the outer surface of the wing tip device lower cover may be disadvantageous.

(39) A fourth comparative example provides for machining the outer surface of the wing tip device lower cover so as to provide a rebate for receiving a P-seal and retainer, which may be affixed to the wing tip device lower cover. The post manufacture machining operation for producing the rebate in the outer surface of the wingtip device lower cover may be disadvantageous.

(40) In a fifth comparative example, the wing tip device lower cover may include a joggle adjacent the gap. A P-seal and retainer may be affixed to the outer surface of the joggle. However, the joggle at the inboard edge of the wing tip device lower cover may provide manufacturing difficulties if it conflicts with joggles formed at the leading and trailing edges of the winged device lower cover that may be provided for attachment of leading and trailing edge structures.

(41) Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.