AIRCRAFT STRUCTURAL COMPONENT FOR LAMINAR FLOW

Description

[0001] The present invention relates to an aircraft structure component for laminar flow, such as a wing, a slat, a droop nose, a Krueger flap, a horizontal tail plane, a vertical tail plane, a wing tip, an engine nacelle, or parts of the same. Further aspects of the invention relate to an aircraft comprising such an aircraft structure component as well as a method for producing such an aircraft structure component.

[0002] US2018 / 134374A1 discloses an aircraft structure component for laminar flow.

[0003] The aircraft structure component has an outer skin with an aerodynamic surface. The aerodynamic surface is referred to as the outer surface of the aircraft structure component that is in contact with the aerodynamic flow circulating around the aircraft structure component. The aerodynamic surface has a leading edge portion and a downstream portion. The leading edge portion is directed towards the incoming flow during flight of the associated aircraft, and is adapted for a laminar flow circulating along said leading edge portion. The downstream portion is located adjacently downstream from the leading edge portion with respect to the incoming flow. The downstream portion of the aerodynamic surface comprises a paint layer that is not present in the leading edge portion. As an alternative to the paint layer a foil layer might be provided in the downstream portion. Although hereinafter it is referred to a paint layer only, the present specification also applies to a foil layer instead of a paint layer. The foil layer is attached to the downstream portion of the aerodynamic surface, preferably by an adhesive. The leading edge portion can be entirely unpainted or can have some sort of paint or lacquer, while in any case the paint layer referred to in here that is present in the downstream portion does not extend over the leading edge portion. In such a way, a border line is formed between the leading edge portion of the aerodynamic surface and the downstream portion by the beginning paint layer. Further, the outer skin comprises an attachment surface to which the paint layer or the foil layer is attached.

[0004] Similar aircraft structure components are known from the prior art. It has been found advantages, in particular due to erosion of the paint in the leading edge portion, to apply the paint layer only in the downstream portion of the aerodynamic surface while omitting the paint layer in the leading edge portion upstream from the downstream portion. This is usually done by a foil or a cover covering the leading edge portion when the aerodynamic surface is painted, so that the paint layer is present only in the downstream portion but not in the leading edge portion after the cover is removed. However, this procedure leaves the border line in the form of a thickness jump at the aerodynamic surface between the unpainted leading edge portion and the painted downstream portion, such that the border line forms an edge line. Such a thickness jump increases the aerodynamic drag of the aircraft structure component, as it negatively influences the laminar flow present at the leading edge portion. Also, such a thickness jump may lead to erosion of the beginning paint layer in the downstream portion.

[0005] Accordingly, the object of the present invention is to provide an aircraft structure component that allows for a reduced aerodynamic drag and reduced erosion of the paint layer.

[0006] This object is achieved in that the attachment surface of the outer skin is lowered, i.e. extends on a lower level, relative to the leading edge portion of the aerodynamic surface, so that a level difference between the downstream portion of the aerodynamic surface formed by the paint layer or the foil layer attached to the lowered attachment surface and the leading edge portion of the aerodynamic surface is minimized, i.e. eliminated or at least reduced. By such a lowered attachment surface and the resulting minimized level difference between the downstream portion of the aerodynamic surface formed by the paint layer or foil layer attached to the lowered attachment surface on the one hand and the leading edge portion of the aerodynamic surface on the other hand, aerodynamic drag caused by the edge or thickness jump formed by the beginning paint layer along the border line can be reduced and erosion of the paint layer along the border line can be reduces, too.

[0007] According to a preferred embodiment, the attachment surface of the outer skin is lowered relative to the leading edge portion of the aerodynamic surface essentially by the thickness of the paint layer or the foil layer attached to the attachment surface, so that the downstream portion of the aerodynamic surface formed by the paint layer or the foil layer attached to the lowered attachment surface is essentially flush with, i.e. extends on the same level as, the leading edge portion of the aerodynamic surface. In such a way, the level difference between the downstream portion of the aerodynamic surface formed by the paint layer or foil layer attached to the lowered attachment surface and the leading edge portion of the aerodynamic surface is eliminated, so that the aerodynamic drag and erosion of the paint layer along the border line can be minimized.

[0008] According to a further preferred embodiment, the downstream portion of the aerodynamic surface comprises a first downstream portion part and a second downstream portion part provided on opposite sides from the leading edge portion, so that there is a first border line part between the leading edge portion and the first downstream portion part, and a second border line part between the leading edge portion and the second downstream portion part. In such a way, the invention can be applied to both sides of the leading edge portion and drag and erosion can be reduced on both sides of the leading edge portion, i.e. upper and lower side of e.g. a wing, slat or horizontal tail plain, or left and right side of e.g. a vertical tail plane.

[0009] According to a preferred embodiment, the aircraft structure component is formed as a leading edge high lift component, such as a slat, a Krueger flap, or a droop nose. This relates to a very advantageous application of the invention.

[0010] According to a preferred embodiment, the aircraft structure component is formed as a wing leading edge component. This relates to another very advantageous application of the invention.

[0011] According to a preferred embodiment, the aircraft structure component is formed as a vertical tail plane leading edge component. This relates to another very advantageous application of the invention.

[0012] According to a preferred embodiment, the aircraft structure component is formed as a horizontal tail plane leading edge component. This relates to another very advantageous application of the invention.

[0013] According to a preferred embodiment, the aircraft structure component is formed as a wing tip component. This relates to another very advantageous application of the invention.

[0014] According to a preferred embodiment, the aircraft structure component is formed as a nacelle leading edge component. This relates to another very advantageous application of the invention.

[0015] A further aspect of the present invention relates to an aircraft comprising the aircraft structure component according to any of the embodiments described above. The features and effects described above in connection with the aircraft structure component apply vis-à-vis also with respect to the aircraft.

[0016] A further aspect of the present invention relates to a method for producing an aircraft structure component according to any of the embodiment described above. The method comprises the following steps: First, an aircraft structure component having an outer skin with an aerodynamic surface is provided. The aerodynamic surface has a leading edge portion and a downstream portion adjacently downstream from the leading edge portion. The outer skin in the area of the downstream portion comprises an attachment surface adapted for a paint layer or a foil layer to be attached to. Then, the attachment surface of the outer skin is lowered relative to the leading edge portion of the aerodynamic surface. Then, a paint layer or a foil layer is applied to the lowered attachment surface, preferably such that a level difference between the downstream portion of the aerodynamic surface formed by the paint layer or the foil layer attached to the lowered attachment surface and the leading edge portion of the aerodynamic surface is minimized. This relates to a simple and efficient method to produce an aircraft structure component for laminar flow. The features and effects described above in connection with the aircraft structure component apply vis-à-vis also with respect to the method.

[0017] According to a preferred embodiment, the attachment surface of the outer skin is lowered relative to the leading edge portion of the aerodynamic surface essentially by the thickness of the paint layer or the foil layer applied to the attachment surface, so that the downstream portion of the aerodynamic surface formed by the paint layer or the foil layer attached to the lowered attachment surface is essentially flush with, i.e. extends on the same level as, the leading edge portion of the aerodynamic surface. In such a way, the level difference between the downstream portion of the aerodynamic surface formed by the paint layer or foil layer attached to the lowered attachment surface and the leading edge portion of the aerodynamic surface is eliminated, so that the aerodynamic drag and erosion of the paint layer along the border line can be minimized.

[0018] According to a preferred embodiment, lowering the attachment surface is carried out by ablation. In such a way, the attachment surface can be lowered efficiently without deforming the outer skin.

[0019] In particular, it is preferred that lowering the attachment surface is carried out by chemical ablation. This allows a very efficient and precise ablation.

[0020] Alternatively, it is preferred that lowering the attachment surface is carried out by machining. This also allows a very efficient and precise ablation.

[0021] Preferred embodiments of the present invention are described hereinafter in more detail by means of a drawing. The drawing shows in Fig. 1a top view of an aircraft including aircraft structure components according to the present invention in the form of slats, Fig. 2a schematic cross-sectional view of an aircraft structure component according to the invention as used in the aircraft shown in Fig. 1, and Fig. 3a schematic cross-sectional view of an aircraft structure component according to the prior art.

[0022] In Fig. 1 an embodiment of an aircraft 10 according to the present invention is shown. The aircraft 10 comprises a fuselage 20, wings 30 including wing tips 40 and leading edge high lift components in the form of slats 50, a vertical tail plane 60, a horizontal tail plane 70, and nacelles 80.

[0023] In Fig. 2 an embodiment of an aircraft structure component 1 for laminar flow according to the invention is shown, in the present embodiment a slat 50 as used in the aircraft 10 shown in Fig. 1. In Fig. 3 a corresponding prior art aircraft structure component 1' is shown.

[0024] The aircraft structure component 1 according to the invention (Fig. 2) and the aircraft structure component 1' according to the prior art (Fig. 3) both have an outer skin 3, 3' with an aerodynamic surface 5, 5' adapted to be in contact with an air flow. The aerodynamic surface 5, 5' has a leading edge portion 7, 7' that is directed towards the incoming flow 9, 9' of an associated aircraft 10, 10' during flight and that is, thus, adapted for a laminar flow. The aerodynamic surface 5, 5' further has a downstream portion 11, 11' adjacently downstream from the leading edge portion 7, 7' with respect to the incoming flow 9, 9'. The downstream portion 11, 11' of the aerodynamic surface 5, 5' comprises a paint layer 13, 13' that is not present in the unpainted leading edge portion 7, 7', so that a border line 15, 15' is present between the leading edge portion 7, 7' and the downstream portion 11, 11' by the beginning paint layer 13, 13', wherein the border line 15, 15' extends transverse the incoming flow 9, 9'. Further, the outer skin 3, 3' comprises an attachment surface 17, 17' to which the paint layer 13, 13' is attached.

[0025] In the aircraft structure component 1' according to the prior art as shown in Fig. 3, the attachment surface 17' forms a continuation of and thus extends at the same level of the leading edge portion 7' of the aerodynamic surface 5', so that the border line 15' with the beginning paint layer 13' is in the form of a thickness jump that might cause drag and erosion of the paint layer 13'.

[0026] In contrast thereto, in the aircraft structure component 1 according to the invention as shown in Fig. 2, the attachment surface 17 of the outer skin 3 is lowered, i.e. extends on a lower level, relative to the leading edge portion 7 of the aerodynamic surface 5, so that a level difference between the downstream portion 11 of the aerodynamic surface 5 formed by the paint layer 13 attached to the lowered attachment surface 17 and the leading edge portion 7 of the aerodynamic surface 5 is minimized. Specifically, the attachment surface 17 is lowered relative to the leading edge portion 7 of the aerodynamic surface 5 by the thickness of the paint layer 13 attached to the attachment surface 17, so that the downstream portion 11 of the aerodynamic surface 5 formed by the paint layer 13 attached to the lowered attachment surface 17 is flush with and extends on the same level as the leading edge portion 7 of the aerodynamic surface 5.

[0027] As also shown in Fig. 2, the downstream portion 11 of the aerodynamic surface 5 comprises a first downstream portion part 11a and a second downstream portion part 11b provided on opposite sides from the leading edge portion 7, so that there is a first border line part 15a between the leading edge portion 7 and the first downstream portion part 11a, and a second border line part 15b between the leading edge portion 7 and the second downstream portion part 11b.

[0028] The aircraft structure components 1 as shown in Fig. 2 can be produces in the following manner: First, an aircraft structure component 1 having an outer skin 3 with an aerodynamic surface 5 is provided, wherein the aerodynamic surface 5 has a leading edge portion 7 and a downstream portion 11 adjacently downstream from the leading edge portion 7 with respect to the incoming flow 9, and wherein the outer skin 3 in the area of the downstream portion 11 comprises an attachment surface 17 adapted for a paint layer 13 to be attached to. Subsequently, the attachment surface 17 of the outer skin 3 is lowered relative to the leading edge portion 7 of the aerodynamic surface 5. Finally, a paint layer 13 is applied to the lowered attachment surface 17, such that a level difference between the downstream portion 11 of the aerodynamic surface 5 formed by the paint layer 13 attached to the lowered attachment surface 17 and the leading edge portion 7 of the aerodynamic surface 5 is minimized. Specifically, the attachment surface 17 is lowered relative to the leading edge portion 7 of the aerodynamic surface 5 by the thickness of the paint layer 13 applied to the attachment surface 17, so that the downstream portion 11 of the aerodynamic surface 17 formed by the paint layer 13 attached to the lowered attachment surface 17 is flush with and extends on the same level as the leading edge portion 7 of the aerodynamic surface 5. Lowering of the attachment surface 17 in the present embodiment is carried out by chemical ablation.

[0029] By the aircraft structure component 1 according to the present invention including a lowered attachment surface 17 and the resulting minimized level difference between the downstream portion 11 of the aerodynamic surface 5 formed by the paint layer 13 attached to the lowered attachment surface 17 on the one hand and the leading edge portion 7 of the aerodynamic surface 5 on the other hand, aerodynamic drag caused by the edge or thickness jump formed by the beginning paint layer 13 along the border line 15 can be reduced and erosion of the paint layer 13 along the border line 15 can be reduces, too.

Claims

1. An aircraft structure component (1) for laminar flow, comprising an outer skin (3) having an aerodynamic surface (5), wherein the aerodynamic surface (5) has a leading edge portion (7) and a downstream portion (11) adjacently downstream from the leading edge portion (7), wherein the downstream portion (11) of the aerodynamic surface (5) comprises a paint layer (13) or a foil layer that is not present in the leading edge portion (7), so that a border line (15) is formed between the leading edge portion (7) and the downstream portion (11) by the beginning paint layer (13) or foil layer, wherein the outer skin (3) comprises an attachment surface (17) to which the paint layer (13) or the foil layer is attached, characterized in that the attachment surface (17) of the outer skin (3) is lowered relative to the leading edge portion (7) of the aerodynamic surface (5), so that a level difference between the downstream portion (11) of the aerodynamic surface (5) formed by the paint layer (13) or the foil layer attached to the lowered attachment surface (17) and the leading edge portion (7) of the aerodynamic surface (5) is minimized.

2. The aircraft structure component according to claim 1, wherein the attachment surface (17) of the outer skin (3) is lowered relative to the leading edge portion (7) of the aerodynamic surface (5) by the thickness of the paint layer (13) or the foil layer attached to the attachment surface (17), so that the downstream portion (11) of the aerodynamic surface (5) formed by the paint layer (13) or the foil layer attached to the lowered attachment surface (17) is flush with the leading edge portion (7) of the aerodynamic surface (5).

3. The aircraft structure component according to claim 1 or 2, wherein the downstream portion (11) of the aerodynamic surface (5) comprises a first downstream portion part (11a) and a second downstream portion part (11b) provided on opposite sides from the leading edge portion (7).

4. The aircraft structure component according to any of claims 1 to 3, wherein the aircraft structure component (1) is formed as a leading edge high lift component, such as a slat (50), a Krueger flap, or a droop nose.

5. The aircraft structure component according to any of claims 1 to 3, wherein the aircraft structure component (1) is formed as a wing leading edge component.

6. The aircraft structure component according to any of claims 1 to 3, wherein the aircraft structure component (1) is formed as a vertical tail plane leading edge component.

7. The aircraft structure component according to any of claims 1 to 3, wherein the aircraft structure component (1) is formed as a horizontal tail plane leading edge component.

8. The aircraft structure component according to any of claims 1 to 3, wherein the aircraft structure component (1) is formed as a wing tip component.

9. The aircraft structure component according to any of claims 1 to 3, wherein the aircraft structure component (1) is formed as a nacelle leading edge component.

10. An aircraft (10) comprising the aircraft structure component (1) according to any of claims 1 to 9.

11. A method for producing an aircraft structure component (1) according to any of claims 1 to 9, comprising the steps of: - Providing an aircraft structure component (1) having an outer skin (3) with an aerodynamic surface (5), wherein the aerodynamic surface (5) has a leading edge portion (7) and a downstream portion (11) adjacently downstream from the leading edge portion (7), and wherein the outer skin (3) in the area of the downstream portion (11) comprises an attachment surface (17) adapted for a paint layer (13) or a foil layer to be attached to; - lowering the attachment surface (17) of the outer skin (3) relative to the leading edge portion (7) of the aerodynamic surface (5), and - applying a paint layer (13) or a foil layer to the lowered attachment surface (17).

12. The method according to claim 11, wherein the attachment surface (17) of the outer skin (3) is lowered relative to the leading edge portion (7) of the aerodynamic surface (5) by the thickness of the paint layer (13) or the foil layer applied to the attachment surface (17), so that the downstream portion (11) of the aerodynamic surface (5) formed by the paint layer (13) or the foil layer attached to the lowered attachment surface (17) is flush with the leading edge portion (7) of the aerodynamic surface (5).

13. The method according to claim 11 or 12, wherein lowering the attachment surface (17) is carried out by ablation.

14. The method according to claim 13, wherein lowering the attachment surface (17) is carried out by chemical ablation.

15. The method according to claim 13, wherein lowering the attachment surface (17) is carried out by machining.