LEADING EDGE STRUCTURE FOR A FLOW CONTROL SYSTEM OF AN AIRCRAFT

Abstract

A leading edge structure (1) for a flow control system of an aircraft (101) including a double-walled leading edge panel (3) with a first side portion (11) extending to a first attachment end (17), a second side portion (13) extending to a second attachment end (19), an inner wall element (21) facing a plenum (7), an outer wall element (23) facing ambient flow (25), and a core assembly (97). The outer wall element (23) includes micro pores (31) and the inner wall element (21) includes openings (33) which form a fluid connection from ambient flow, through the core assembly (97) and to the plenum (7). The thickness of the outer wall element is reduced due to the first attachment end (17) and/or at the second attachment end (19) attached to the inner wall element (21) by both bonding and fasteners (85, 87, 89, 91).

Claims

1. A leading edge structure for a flow control system of an aircraft comprising: a double-walled leading edge panel that surrounds the a plenum in a curved manner, the plenum extending in a span direction of the leading edge structure; wherein the double-walled leading edge panel has a first side portion extending from a leading edge point to a first attachment end, wherein the double-walled leading edge panel has a second side portion opposite the first side portion, extending from the leading edge point to a second attachment end, wherein the double-walled leading edge panel comprises an inner wall element facing the plenum and an outer wall element for contact with an ambient flow, wherein between the inner and outer wall elements the double-walled leading edge panel comprises a core assembly, wherein the outer wall element comprises a plurality of micro pores forming a fluid connection between the core assembly and the ambient flow, and wherein the inner wall element comprises openings forming a fluid connection between the core assembly and the plenum, and wherein at the first attachment end and/or at the second attachment end the outer wall element is attached to the inner wall element by both bonding and fasteners.

2. The leading edge structure according to claim 1, wherein at the first attachment end and/or at the second attachment end the outer wall element rests against the inner wall element along a common contact plane.

3. The leading edge structure according to claim 2, wherein at the first attachment end and/or at the second attachment end between the outer wall element and the inner wall element a bonding layer is provided extending within the contact plane.

4. The leading edge structure according to claim 3, wherein the bonding layer is made of film adhesive.

5. The leading edge structure according to claim 3, wherein the bonding layer has a thickness in a range of 0.1 mm to 0.2 mm.

6. The leading edge structure according to claim 3, wherein the bonding layer has a peeling strength of at least 150 N/mm.

7. The leading edge structure according to claim 1, wherein at the first attachment end and/or at the second attachment end a plurality of fasteners extend through both the outer wall element and the inner wall element.

8. The leading edge structure according to claim 1, wherein the outer wall element extends from the first attachment end to the second attachment end.

9. The leading edge structure according to claim 1, wherein the core assembly comprises a plurality of elongate stiffeners spaced apart from one another, so that between each pair of adjacent stiffeners a hollow chamber is formed between the inner and outer wall elements, wherein the plurality of micro pores form a fluid connection between the hollow chambers and the ambient flow, and wherein the openings form a fluid connection between the hollow chambers and the plenum.

10. The leading edge structure according to claim 1, wherein the outer wall element forms a first end edge at the first attachment end and a second end edge at the second attachment end.

11. The leading edge structure according to claim 10, wherein the first end edge and/or the second end edge are parallel to at least one of the stiffeners.

12. The leading edge structure according to claim 1, wherein the outer wall element comprises a main wall portion and a first wall extension and/or a second wall extension, wherein the main wall portion includes the leading edge point, wherein the first wall extension includes the first attachment end, and wherein the second wall extension includes the second attachment end.

13. The leading edge structure according to claim 12, wherein the first wall extension is connected to the main wall portion via a first welding seam, and/or wherein the second wall extension is connected to the main wall portion via a second welding seam.

14. The leading edge structure according to claim 13, wherein the first welding seam and/or the second welding seam are dressed to form a smooth transition between the main wall portion and the first wall extension and/or between the main wall portion and the second wall extension.

15. The leading edge structure according to claim 13, wherein the first welding seam is attached directly to the inner wall element, and/or wherein the second welding seam is attached directly to the inner wall element.

16. The leading edge structure according to claim 13, wherein the micro pores are present in the main wall portion and are distributed from the leading edge point to the first welding seam and/or to the second welding seam.

17. A vertical tail plane configured for an aircraft comprising a vertical tail plane box including a first lateral panel with a first attachment portion and an opposite second lateral panel with a second attachment portion, a leading edge structure including: a plenum extending in a span direction of the vertical tail plane; a double-walled leading edge panel at least partially surrounding the plenum, wherein the double-walled leading edge panel includes: an inner wall element facing the plenum; an outer wall element configure to be in contact with an ambient flow over the vertical tail plane, and a core assembly between the inner wall element and the outer wall element; micro-pores in the outer wall element and openings in the inner wall element, wherein air from the ambient flow flows through the micro-pores, the core assembly, the openings and into the plenum; a first side portion of the double-walled leading edge extends from a leading edge point to a first attachment end; and a second side portion of the double-walled leading edge is opposite the first side portion, and extends from the leading edge point to a second attachment end, wherein at the first attachment end and/or at the second attachment end attaches to the inner wall element by both bonding and fasteners; wherein the first attachment end is attached to the first attachment portion, and the second attachment end is attached to the second attachment portion, wherein the first side portion of the leading edge panel forms a continuous flow surface with the first lateral panel of the vertical tail plane box, and the second side portion of the leading edge panel forms a continuous flow surface with the second lateral panel of the vertical tail plane box.

18. The vertical tail plane according to claim 17, wherein the first attachment end is attached to the first attachment portion by a first front line of fasteners extending through the main wall portion, and by a first rear line of fasteners extending through the first wall extension, so that the first welding seam extends between the first front line of fasteners and the first rear line of fasteners, and/or wherein the second attachment end is attached to the second attachment portion by a second front line of fasteners extending through the main wall portion, and by a second rear line of fasteners extending through the second wall extension, so that the second welding seam extends between the second front line of fasteners and the second rear line of fasteners.

19. The vertical tail plane according to claim 18, wherein the first front line of fasteners and/or the second front line of fasteners extend through a back wall connecting the first attachment end to the second attachment end of the leading edge panel, to attach the back wall to the leading edge panel, and/or wherein the first rear line of fasteners extend through the first attachment portion of the vertical tail plane box to attach the vertical tail plane box to the leading edge panel and/or the second rear line of fasteners extend through the second attachment portion of the vertical tail plane box to attach the vertical tail plane box to the leading edge panel.

20. An aircraft comprising a leading edge structure according to claim 1.

Description

SUMMARY OF DRAWINGS

[0043] Embodiments of the invention are illustrated in the drawings which are:

[0044] FIG. 1 is a perspective view of an aircraft,

[0045] FIG. 2 is a perspective cut open view of an embodiment of a leading edge structure according to an embodiment of the invention,

[0046] FIG. 3 is a cross sectional view across the span direction of the leading edge structure shown in FIG. 2,

[0047] FIG. 4 is a detailed view of the second attachment end of the leading edge structure shown in FIG. 3,

[0048] FIG. 5 is a detailed view of a hollow chamber of the leading edge structure shown in FIG. 3,

[0049] FIG. 6 is a detailed view of another hollow chamber of the leading edge structure shown in FIG. 3, wherein the inner wall element has an opening formed as a throttle hole,

[0050] FIG. 7 is an exploded view of the leading edge structure shown in FIG. 3,

[0051] FIG. 8 is a perspective view of the outer wall element of the leading edge structure shown in FIG. 7, indicating the first and second welding seams,

[0052] FIG. 9 is a side view of a vertical tail plane for an aircraft comprising the leading edge structure shown in FIG. 2,

[0053] FIG. 10 is a detailed perspective view of a connection duct of the vertical tail plane shown in FIG. 9, and

[0054] FIG. 11 is another perspective view of the connection duct shown in FIG. 10.

DETAILED DESCRIPTION

[0055] In FIG. 1 an aircraft 101 according to an embodiment of the present invention is shown. The aircraft comprises a fuselage 103, wings 105, a horizontal tail plane 107, and a vertical tail plane 109 according to an embodiment of the invention. The vertical tail plane 109 is shown in more detail in FIG. 9. The vertical tail plane 109 comprises a leading edge structure 1 according to an embodiment of the invention. Various embodiments of the leading edge structure 1 are shown in more detail in FIGS. 2 to 8.

[0056] In FIGS. 2 and 3 an embodiment of a leading edge structure 1 for a flow control system of an aircraft according to the present invention is shown. The leading edge structure 1 comprises a double-walled leading edge panel 3 and a back wall 5.

[0057] The leading edge panel 1 surrounds a plenum 7 in a curved manner, wherein the plenum 7 extends in a span direction 9. The leading edge panel 3 has a first side portion 11 and an opposite second side portion 13. The first side portion 11 extends from a leading edge point 15 to a first attachment end 17. The second side portion 13 extends from the leading edge point 15 to a second attachment end 19, as shown in FIG. 4.

[0058] The back wall 5 is formed as a membrane of CFRP material and connects the first attachment end 17 to the second attachment end 19 of the leading edge panel 3. In such a way, the back wall 5 encloses the plenum 7 together with the leading edge panel 3 on a side opposite the leading edge point 15.

[0059] The leading edge panel 3 comprises an inner wall element 21 facing the plenum 7 and an outer wall element 23 in contact with an ambient flow 25. Between the inner and outer wall elements 21, 23 the leading edge panel 3 comprises a core assembly 97 comprising a plurality of elongate stiffeners 27 spaced apart from one another, so that between each pair of adjacent stiffeners 27 a hollow chamber 29 is left open between the inner and outer wall elements 21, 23, as shown in FIG. 5. The stiffeners 27 extend in the span direction 9 in parallel to the leading edge point 15 and in parallel to one another.

[0060] The outer wall element 23 comprises a plurality of micro pores 31 forming a fluid connection between the hollow chambers 29 and the ambient flow 25. The inner wall element 21 comprises openings 33 forming a fluid connection between the hollow chambers 29 and the plenum 7. At some of the hollow chambers 29, the openings 33 are formed as throttle holes 35 having a predefined diameter 37 adapted for a predefined mass flow rate through the throttle holes 35 in order to achieve a predefined fluid pressure in the hollow chambers 29, as it is shown in FIG. 6. However, at others of the hollow chambers 29, the openings 33 are formed to allow a random mass flow rate and are not adapted to control the fluid pressure in the hollow chambers 29, as it is the case in the hollow chamber 29 shown in FIG. 5.

[0061] The stiffeners 27 are formed integrally with the inner wall element 21. The inner wall element 21 is formed of a Carbon Fiber Reinforced Plastic (CFRP). The stiffeners 27 have a solid trapezoid-shaped cross section and are formed as sandwich structures 39. Each sandwich structure 39 comprises a core element 41 enveloped on opposite sides by first and second separate layers 43a, 43b of CFRP of the inner wall element 21, wherein one layer 43a encloses the core element 41 on the side facing the plenum 7, while the other layer 43b encloses the trapezoid surface of the core element 41 on the side facing the outer wall element 23 by an omega-shape curse. The core elements 41 are formed of a foam material.

[0062] As shown in FIG. 2, a plurality of support ribs 45 are attached to the inner wall element 21 in such a way that they face the plenum 7 and extend perpendicular to the stiffeners 27 and to the span direction 9 along the inner wall element 21. The support ribs 45 are formed integrally with the inner wall element 21 and are also formed of a CFRP material.

[0063] The outer wall element 23 is formed as a titanium sheet and comprises multiple sections 47a, 47b, 47c arranged subsequently in a chord direction 49. The porosity varies from one section 47a to another section 47b, 47c in terms of the pore pitch, wherein the pore pitch increases from the leading edge point 15 downstream.

[0064] As shown in FIGS. 4, 7 and 8, the outer wall element 23 extends from the first attachment end 17 to the second attachment end 19. The outer wall element 23 forms a first end edge 51 at the first attachment end 17 and a second end edge 53 at the second attachment end 19. The first end edge 51 and the second end edge 53 extend in parallel to the leading edge 54 and are formed to extend along or rest against a vertical tail plane box 55 of the associated vertical tail plane 109. This means, the outer wall element 23 extends as far as the inner wall element 21 at the first attachment end 17 and at the second attachment end 19. The first end edge 51 and the second end edge extend 53 in parallel to the stiffeners 27. This means, the end edges 51, 53 extend in span direction 9.

[0065] The outer wall element 23 comprises a main wall portion 59 as well as a first wall extension 61 and a second wall extension 63. The main wall portion 59 includes the leading edge point 15. The first wall extension 61 includes the first attachment end 17 and the first end edge 51. The second wall extension 63 includes the second attachment end 19 and the second end edge 53. As shown in FIGS. 7 and 8, the first wall extension 61 is connected to the main wall portion 59 via a straight first welding seam 67. Additionally, the second wall extension 63 is connected to the main wall portion 59 via a straight second welding seam 69. First and second welding seams 67, 69 are butt-welding seams formed by laser welding. The first welding seam 67 and the second welding seam 69 are dressed at the outer flow surface 71 to form a smooth transition between the main wall portion 59 and the first wall extension 61 and between the main wall portion 59 and the second wall extension 63.

[0066] As shown in FIG. 4, the first welding seam 67 and the entire first wall extension 61 are bonded directly and planar to the inner wall element 21 with no core assembly 97 in between. Additionally, the second welding seam 69 and the entire second wall extension 63 are bonded directly and planar to the inner wall element 21 with no core assembly 97 in between. A bonding layer 98 extends directly between the inner and outer wall elements 21, 23 within a contact plane 99 at the first and second attachment ends 17, 19. No micro pores 31 are present in the first and second wall extensions 61, 63. As indicated in FIG. 7, the micro pores 31 are present only in the main wall portion 59 and are distributed from the leading edge point 15 to the first welding seam 67 and to the second welding seam 69 with a minimum distance from the welding seams 67, 69.

[0067] As also shown in FIG. 4, at the first attachment end 17 and at the second attachment end 19 the outer wall element 23 is additionally attached to the inner wall element 21 by fasteners 85, 87, 89, 91, i.e. bolts, rivets or lockbolts, so that at the first and second attachment ends 17, 19 the outer wall element 23 is attached to the inner wall element 21 by both bonding layer 98 and fasteners 85, 87, 89, 91. At the first attachment end 17 and at the second attachment end 19 the outer wall element 23 rests against the inner wall element 21 along the common contact plane 99 in an overlapping and planar manner, wherein within the contact plane 99 the bonding layer 98 is provided. The bonding layer 98 is made of film adhesive, has a thickness of between 0.1 and 0.2 mm, and has a peeling strength in the range above 150 N/mm.

[0068] FIGS. 9 to 11 show a vertical tail plane 109 for an aircraft 101 according to the invention. The vertical tail plane 109 comprises a vertical tail plane box 55 and a leading edge structure 1 as described before. The vertical tail plane box 55 has a first lateral panel 75 with a first attachment portion 77 and an opposite second lateral panel 79 with a second attachment portion 81. The first attachment end 17 of the leading edge panel 3 is attached to the first attachment portion 77 such that the first end edge 51 extends along the first attachment portion 77, and the second attachment end 19 of the leading edge panel 3 is attached to the second attachment portion 81 such that the second end edge 53 extends along the second attachment portion 81. The first side portion 11 of the leading edge panel 3 forms a continuous flow surface 71 with the first lateral panel 75 of the vertical tail plane box 55, and the second side portion 13 of the leading edge panel 3 forms a continuous flow surface with the second lateral panel 79 of the vertical tail plane box 55. The plenum 7 is in fluid connection with an air outlet 83 for causing a vacuum in the plenum 7 to draw air from the ambient flow 25 through the micro pores 31 and the hollow chambers 29 into the plenum 7.

[0069] As shown in FIGS. 4 and 8, the first attachment end 17 is attached to the first attachment portion 77 by a first front line of fasteners 85 extending through the main wall portion 59, and by a first rear line of fasteners 87 extending through the first wall extension 61, so that the first welding seam 67 extends between the first front line of fasteners 85 and the first rear line of fasteners 87. Additionally, the second attachment end 19 is attached to the second attachment portion 81 by a second front line of fasteners 89 extending through the main wall portion 59, and by a second rear line of fasteners 91 extending through the second wall extension 63, so that the second welding seam 69 extends between the second front line of fasteners 89 and the second rear line of fasteners 91. The fasteners 85, 87, 89, 91 can be e.g. bolts, lockbolts, rivets.

[0070] The first front line of fasteners and/or the second front line of fasteners may extend through a back wall connecting the first attachment end to the second attachment end of the leading edge panel, to attach the back wall to the leading edge panel. A flange of the back wall may rest against an inner surface of the inner wall element in an overlapping manner. Additionally or alternatively, the first rear line of fasteners extend through the first attachment portion of the vertical tail plane box to attach the vertical tail plane box to the leading edge panel. The first attachment portion may rest against the inner surface of the inner wall element in an overlapping manner. Additionally or alternatively, the second rear line of fasteners extend through the second attachment portion of the vertical tail plane box to attach the vertical tail plane box to the leading edge panel. The second attachment portion may rest against the inner surface of the inner wall element in an overlapping manner. In such a way, the back wall and/or the vertical tail plane box can be attached to the leading edge panel by the same fasteners used to attach the inner and outer wall element to one another.

[0071] As shown in FIG. 4, the first front line of fasteners 85 and the second front line of fasteners 89 extend through the back wall 5 connecting the first attachment end 17 to the second attachment end 19 of the leading edge panel 3, to attach the back wall 5 to the leading edge panel 3. A flange 100 of the back wall 5 rests against an inner surface of the inner wall element 21 in an overlapping manner. Additionally, the first rear line of fasteners 87 extend through the first attachment portion 77 of the vertical tail plane box 55 to attach the vertical tail plane box 55 to the leading edge panel 3. The first attachment portion 77 rests against the inner surface of the inner wall element 21 in an overlapping manner. Additionally, the second rear line of fasteners 91 extend through the second attachment portion 81 of the vertical tail plane box 55 to attach the vertical tail plane box 55 to the leading edge panel 3. The second attachment portion 81 rests against the inner surface of the inner wall element 21 in an overlapping manner.

[0072] As shown in FIGS. 10 and 11, the vertical tail plane 109 further comprises a connection duct 93 connecting a lower end 95 of the plenum 7 to the air outlet 83. In addition to the air outlet flap 83 the plenum 7 might also be in fluid connection with an air inlet (not shown) for causing an overpressure in the plenum 7 to blow out air from the plenum 7 through the hollow chambers 29 and the micro pores 31 to the ambient flow 25.

[0073] The leading edge structure 1 shown in FIGS. 2 to 8 can be manufactured by a method including the following steps: The inner wall element 21 and the core assembly 97 is produced, wherein the stiffeners 27 and the inner wall element 21 are formed together as an integral part by a Resin Transfer Molding (RTM) process in a common RTM step. Also the support ribs 45 are formed as an integral part together with the inner wall element 21 and the stiffeners 27 by an RTM process. Further, the outer wall element 23 is produced. Then, the outer wall element 23 is bonded to the core assembly 97 and to the inner wall element 21, wherein the outer wall element 23 is bonded against the stiffeners 27 and against the inner wall element 21 at the first and second attachment ends 17, 19.

[0074] The outer wall element 23 is produced comprising the following steps: The main wall portion 59 is provided, which is formed by a titanium sheet of 1.25 m width and 1 mm thickness. The first wall extension 61 and the second wall extension 63 are provided in the form of titanium sheets of 0.125 m width each and 1 mm thickness. Then, the main wall portion 59 is butt-welded to the first wall extension 61 to form the first welding seam 67, and to the second wall extension 63 to form the second welding seam 69, by laser welding. The first welding seam 67 and the second welding seam 69 are subsequently dressed at the outer flow surface 71 to form a smooth transition between the main wall portion 59 and the first wall extension 61 and between the main wall portion 59 and the second wall extension 63.

[0075] By the leading edge structure 1 according to the present invention as described above, the bonding layer 98 inhibits a buckling of the outer wall element 23 at the first and second attachment ends 17, 19, thereby essentially decreasing the pull out loads of the fasteners 85, 87, 89, 91, which in turn allows to minimize the thickness of the outer wall element 23. A minimum thickness of the outer wall element 23 saves weight and simplifies introduction of the micro pores 31 into the outer wall element 23.

[0076] While at least one exemplary 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” 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.