Method of joining wing skin to structural element of aircraft wing

Abstract

A method of joining a wing skin to a structural element of an aircraft wing is disclosed. A positioning through hole extending along a path between a first side portion of the structural element and a second side portion of the structural element is formed in the structural element. A spark protection cap is attached to the first side of the structural element to cover the opening of the positioning through hole. A portion of the wing skin is positioned on the second side of the structural element. A fastening through-hole having a larger diameter than the positioning through-hole is formed through both the wing skin and the structural element and along a path of the positioning through-hole. Fasteners are inserted into the fastening through-holes and secure the structural element to the wing skin, the ends of the fasteners being covered by the spark shield.

Description

Technical Field

[0001] The present invention relates to aircraft wings and, more particularly, to a method for assembling an aircraft wing. Background Art

[0002] In the assembly of aircraft wings, fasteners are installed to attach the wing skin to structural elements of the wing, such as ribs and spars.

[0003] Some wing designs prevent access to the interior of the wing structure during assembly, and therefore require installation to be performed primarily from the outside of the wing structure, which is known as "single-sided" assembly. In this assembly method, the wing skin can be removed after drilling to clean off shavings, or the drilled holes can be deflashed before being reattached and fastened to the wing's structural elements. However, these additional steps can increase the production time of the wing. Some assembly methods are known as "one-way" assembly, in which the wing skin is not removed once fastened to the structural elements, eliminating the need for subsequent cleaning or deflashing steps, thereby reducing production time. If both one-sided and one-way assembly techniques are employed, all installation steps can be performed from the outside of the wing structure, and no subsequent steps are required. However, in this method, fasteners that can be installed and fastened from one side must be used, which are known as one-sided fasteners.

[0004] It is also known that fasteners in aircraft wings often require additional sealing, such as by providing spark protection caps applied to the wing's structural elements to cover the interior portion of the fasteners, thereby providing lightning protection, fuel containment, and corrosion resistance. In particular, fuel tank fasteners require safety-compliant protection to isolate potential ignition sources, such as lightning strikes, from the fuel tank. However, in the case of one-sided assembly, in which the caps are applied to the wing's structural elements before drilling, this additional sealing requires precise positioning of both the spark protection caps and the fastener-receiving through-holes to ensure that the holes in the spark protection caps are "broken" and that the trailing side of the fasteners is positioned within the caps when the fasteners are inserted through the fastener through-holes. Furthermore, due to the one-sided approach, these protective components may not be adjustable after the fasteners are installed.

[0005] It would therefore be desirable to provide an improved method for assembling aircraft wings that allows for the precise, single-sided installation of single-sided fasteners with the necessary spark protection caps while also reducing production time. Summary of the Invention

[0006] A first aspect of the present invention provides a method for attaching a wing skin to a structural element of an aircraft wing. The method comprises: forming a locating through-hole in the structural element, the locating through-hole extending along a path between a first side of the structural element and a second side of the structural element; attaching a spark arrester cap to the first side of the structural element, the spark arrester cap covering an opening of the locating through-hole; locating a portion of the wing skin on the second side of the structural element; forming a fastening through-hole having a larger diameter than the locating through-hole through both the wing skin and the structural element and along the path of the locating through-hole, such that the fastening through-hole includes a first opening in the wing skin and a second opening in the structural element and covered by the spark arrester cap; and inserting a fastener into the fastening through-hole and securing the structural element to the wing skin, the end of the fastener being covered by the spark arrester cap.

[0007] The method facilitates precise, one-sided installation of fasteners for securing the wing skin to the structural elements of the wing, wherein the fasteners are covered by spark protection caps, ensuring that the fasteners meet safety standards. The method does not require additional stages, such as cleaning or deburring the fastener through-holes, and thus the installation process can be relatively quick compared to two-sided installation or installation procedures involving drilling holes followed by removal of the wing skin.

[0008] As used herein, a "positioning through-hole" refers to an initial through-hole that indicates the location for attaching the spark arrester. During the assembly process, it is expected that the positioning through-hole will be removed or effectively widened during the formation of subsequent fastening through-holes. As used herein, a "fastening through-hole" refers to a through-hole sized such that a blind fastener can be received therein and engage with a surface adjacent to the through-hole to fasten the surfaces together.

[0009] As used herein, "forming" a through-hole refers to any process for forming a through-hole, such as drilling and / or cutting. As referred to herein, a fastening through-hole formed "along the path of" a positioning through-hole means that the fastening through-hole is formed at approximately the same location and in approximately the same orientation as the positioning through-hole. The fastening through-hole does not necessarily have to be perfectly parallel to the positioning through-hole; those skilled in the art will appreciate that the relative angle at which the fastening through-hole passes through the structural element can vary, but nonetheless, the fastening through-hole can have a first opening in the wing skin and a second opening within the spark arrester. For example, depending on the diameter of the fastening through-hole relative to the positioning through-hole, the thickness of the structural element, and the inner diameter of the spark arrester, the fastening through-hole can be aligned, for example, within 45 degrees, within 20 degrees, within 5 degrees, or within 1 degree of the positioning through-hole. Thus, the fastening through-hole can be considered to be formed at least partially through the positioning through-hole, with the fastening through-hole at least partially, and in some examples, completely, overlapping the positioning through-hole. In some examples, the positioning through-hole is centrally located relative to a subsequently formed fastening through-hole, and the fastening through-hole is formed substantially parallel to the positioning through-hole so as to completely overlap with the positioning through-hole.

[0010] A spark arrester is a cap having a body with an internal cavity that typically forms a sealed cavity around the end of a fastener protruding from a structural member. The volume of gas enclosed by the cavity provides spark suppression and contains sparks and plasma outgassing that can occur between the structural member and the metal fastener during, for example, a lightning strike. In some examples, components of the spark arrester are formed from additional insulating material to aid in this spark suppression. For example, the spark arrester may alternatively be referred to as a lightning strike cap.

[0011] When forming a positioning hole in a structural element, the spark arrester can be precisely positioned on the structural element by, for example, using the positioning hole as a guide mark. This can reduce uncertainty in the position of the spark arrester, which can be beneficial when installing single-sided fasteners. The positioning hole can be formed during machining of the structural element and can therefore be formed with very high precision relative to the desired position.

[0012] Because the locating holes are in known positions relative to the structural component, the spark arrester can be precisely positioned relative to the structural component, and thus the fastening holes can be precisely formed relative to the spark arrester. The fastening holes can "clear" the locating holes. As used herein, "clearing" the locating holes means drilling through, along, or sufficiently close to the path of the locating holes, thereby removing the surfaces that bound the locating holes and thereby removing the locating holes. In this sense, the locating holes can be understood to have been replaced by or expanded by the fastening holes to form the fastening holes.

[0013] When the spark protection cap is positioned to cover the opening of the positioning through-hole and subsequently the opening of the fastening through-hole, the fastener is thereby covered by the spark protection cap on the structural member side when inserted into the fastening through-hole. In other words, the trailing end portion of the fastener, i.e., the portion of the fastener exposed from the second opening of the fastening through-hole, is covered by the spark protection cap. This can allow the fastener to comply with safety standards and allow it to be used, for example, in or near a fuel tank. In addition, the spark protection cap can also accommodate chips generated when forming the fastening through-hole and help remove the chips, and prevent the chips from being deposited on other parts of the wing interior. This can be contrasted with a method of forming the fastening through-hole before attaching the spark protection cap, in which a larger amount of chips may be generated while drilling the hole and a more rigorous or time-consuming cleaning process may be required to remove the chips because there is no cap to contain the chips.

[0014] Furthermore, when the positioning holes are formed before the fastening holes are formed, a certain amount of material is removed from the structural element during the formation of the positioning holes. This can reduce the amount of material generated as chips during the formation of the fastening holes, thereby further improving the installation process. The presence of the positioning holes can also reduce the difficulty of forming the fastening holes, for example by reducing the load placed on the machining tool during the formation of the fastening holes.

[0015] In particular, this method can be contrasted with assembly methods in which both the wing skin and the structural element are drilled with through-holes prior to assembly. For example, in some known assembly methods, during the pre-assembly phase, a common through-hole is drilled into both the structural element and the wing skin, formed by a single drilling operation. This through-hole is then used to insert fasteners to attach the structural element to the wing skin. Subsequently, the structural element and wing skin are separated so that, for example, a spark guard can be attached to the structural element. However, there is a risk that the through-holes may become misaligned when the structural element and wing skin are rejoined for fastening during wing assembly, for example, due to slight changes in the shape of the structural element during attachment to the rest of the wing structure. In the present invention, however, the wing cover is drilled only at the locations where it is fastened to the structural element, which eliminates or otherwise reduces the risk of through-hole misalignment. Furthermore, and in any case, since the wing skin may only need to be aligned with the structural element once rather than twice, overall assembly time can be reduced.

[0016] Optionally, attaching the spark shield includes placing a temporary fastener within the positioning through-hole. The temporary fastener is configured to secure the spark shield to the structural element. In this way, the spark shield can be precisely aligned using the positioning through-hole as a guide and held in place during attachment of the spark shield to the structural element. This can improve the installation accuracy of the spark shield. For example, during attachment to the structural element, the application of adhesive may cause the spark shield to move or otherwise reposition. The temporary fastener can resist or prevent such movement, facilitating attachment of the spark shield to the desired position. In addition, the temporary fastener can exert a force on the spark shield to assist in attaching the spark shield to the structural element. For example, the temporary fastener can exert a force on the spark shield that serves to press the spark shield against the structural element and thereby increase the strength of the adhesive bond between the spark shield and the structural element. This force can also resist the lifting force that may be imparted by injecting adhesive into the cap. The temporary fastener can also be referred to as a positioning tool.

[0017] Optionally, the temporary fastener is threaded, and the spark arrester includes a corresponding threaded receiving portion configured to receive the threaded portion of the temporary fastener. In this manner, the temporary fastener can be directly installed and subsequently removed by screwing in and out, for example, once the spark arrester is attached to the structural element.

[0018] Optionally, the temporary fastener is an expandable temporary fastener and the spark shield includes a surface that is arranged so that when the temporary fastener is inserted into the spark shield, the temporary fastener expands and engages with the surface to prevent removal from the spark shield. Such expandable temporary fasteners may be referred to as Cleco or Cleko fasteners. Typically, such fasteners include a flexible flange portion or some other expansion portion that contracts when inserted through the locating through hole, but opens once through to create a cross-section that is too large relative to the locating through hole and thereby prevents removal from the locating through hole. In this way, the temporary fastener can be installed quickly, which, for example, can increase the production speed of the wing.

[0019] Optionally, the spark arrester includes a gasket positioned within the inner cavity.

[0020] Optionally, the washer is formed from an electrically insulating material. This can further enhance the performance of the spark arrester in preventing or reducing the flow of electrical current that might otherwise present an ignition risk, for example. This can further enhance the spark suppression effect of the spark arrester.

[0021] Alternatively, the surface that engages with the temporary fastener is a washer.For example, the temporary fastener can be screwed into through the opening of the washer and engage with the face of the washer.

[0022] Optionally, the spark shield includes a portion configured to receive an adhesive for attaching the spark shield to the structural element, and wherein attaching the spark shield to the first side of the structural element includes providing the adhesive and curing the adhesive. When adhesive is used, physical modifications to the structural element or the spark shield can be reduced, for example, by eliminating or reducing the need to drill additional holes and provide additional fasteners to attach the spark shield to the structural element. This can further reduce the time required or the number of stages required to install the spark shield. The spark shield, when including a portion configured to receive the adhesive, can limit the spread of adhesive within the interior of the aircraft and within the interior of the shield, which can, for example, provide a cleaner installation.

[0023] Optionally, the portion is a skirt provided along the periphery of the spark protection cap base, the skirt being configured so that adhesive supplied to the skirt can be confined within the skirt and does not enter the interior of the cap, where the adhesive entering the interior of the cap may impair the cap's lightning protection performance.

[0024] Optionally, the diameter of the locating holes is less than half the diameter of the fastening holes. A temporary fastener smaller than half the inner diameter of the spark arrester can be used. By reducing the size of the locating holes relative to the fastening holes, any misalignment in the fastening holes is more likely to "clear" the locating holes by completely overlapping them.

[0025] Optionally, the diameter of the positioning through-hole is less than one quarter of the diameter of the fastening through-hole. A temporary fastener smaller than half the inner diameter of the spark protection cap may be used.

[0026] Optionally, the diameter of the fastening through-hole is greater than three-quarters of the inner diameter of the spark arrester. In other words, the spark arrester can be sufficiently large to accommodate the fastener, but not so large as to reduce the overall size of the spark arrester. This can reduce the weight of an aircraft wing, for example, particularly when expanded to include multiple spark arresters.

[0027] In an example, the diameter of the locating through hole is one of 2 mm, 2.4 mm, 2.8 mm, or 3.2 mm. In an example using a fractional-inch drill system, the diameter of the locating through hole is one of 5 / 64 inch, 3 / 32 inch, 7 / 64 inch, or 1 / 8 inch. Similarly, temporary fasteners of substantially the same size can be used. In an example, a fastener with a diameter of 1 / 4 inch is used. In a specific example, a locating through hole with a diameter of 3 / 32 inch and a fastening through hole with a diameter of 1 / 4 inch are used.

[0028] Optionally, the structural element is a rib or a spar of an aircraft wing.

[0029] Optionally, the structural element forms part of a fuel tank, and the spark arrester is disposed within the fuel tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0031] Figure 1 shows a schematic diagram of a wing skin attached to a structural element of an aircraft wing according to an example;

[0032] Figures 2a to 2e A schematic diagram showing steps of a method for attaching a wing skin to a structural element of an aircraft wing according to an example;

[0033] Figure 3 Shown for Figures 2a to 2e a schematic diagram of a temporary fastener according to a first example used in the method;

[0034] Figure 4 Shown for Figures 2a to 2e a schematic diagram of a temporary fastener according to a second example used in the method;

[0035] Figure 5 A schematic diagram illustrating formation of a fastening through-hole according to an example is shown. DETAILED DESCRIPTION

[0036] Figure 1 The components of the wing structure 50 of an aircraft 10 are schematically illustrated. A wing skin 100, alternatively referred to as a wing cover, is attached to a structural element 200 of the wing, such as a rib or spar. Generally, the structural element 200 defines the overall shape of the aircraft wing 50 and supports the wing skin 100, allowing it to remain smooth and generate the appropriate aerodynamic forces required for flight. Attaching the wing skin 100 to the structural element 200 requires drilling holes in the wing skin 100 and the structural element 200 so that fasteners can attach the wing skin 100 and the structural element 200 together.

[0037] Figures 2a to 2e A method for attaching a wing skin 100 to a structural element 200 according to an embodiment is schematically illustrated. Each figure is a cross-sectional view illustrating the structural element 200 at various stages of the method.

[0038] exist Figure 2a, a locating through-hole 400 has been drilled through the structural element 200. The locating through-hole 400 is formed through the structural element such that a first opening 401 of the locating through-hole 400 is located on a first side 201 of the structural element 200 and a second opening 402 of the locating through-hole 400 is located on a second side 202 of the structural element 200, the first side 201 of the structural element 200 being opposite the second side 202 of the structural element 200. In the assembled wing, the first side 201 of the structural element 200 is the inner surface of the aircraft wing 50, while the second side 202 of the structural element 200 faces toward the exterior of the aircraft wing 50 relative to the first side 201.

[0039] In this example, the positioning holes 400 are formed by a 2.4 mm drill bit or a 3 / 32 inch drill bit. The positioning holes 400 can be formed during machining of the structural element 200, which can achieve high accuracy, such as high accuracy within 0.1 mm of the expected or target position. Figure 2d The fastening hole formed therein has a narrower diameter than the positioning through hole 400 .

[0040] In addition, if Figure 2a As shown in FIG, the spark protection cap 300 can be positioned to cover the opening of the positioning hole 400. The spark protection cap 300 can be positioned using the positioning hole 400 as a guide. The spark protection cap 300 includes a body having an inner cavity. A skirt 310 surrounds the periphery of the body and has an inlet 312 for delivering adhesive to the skirt 310.

[0041] exist Figure 2b In the embodiment shown, the spark protection cap 300 is already attached or attached to the structural element 200. In this example, to attach the spark protection cap 300, the skirt 310 of the spark protection cap 300 is filled with adhesive via the inlet 312 and cured to attach the spark protection cap 300 to the structural element 200. The adhesive may be, for example, a polysulfide sealant or a polythioether sealant. The adhesive may also be used to seal the interior of the spark protection cap 300 from the interior of the aircraft wing 50 surrounding the spark protection cap 300. This is one example of how the spark protection cap 300 may be attached to the structural element 200. In some examples, for example, the spark protection cap 300 may come with the adhesive already disposed within the cap 300, and the operator may simply initiate the curing process of the adhesive. In other examples, attaching the spark protection cap 300 to the structural element 200 may include providing additional mechanical fasteners, or integrated fasteners formed and distributed between the structural element 200 and the spark protection cap 300 , which enable attachment of the structural element 200 and the spark protection cap 300 .

[0042] exist Figure 2cIn the embodiment shown, the wing skin 100 is positioned on the second side 202 of the structural element 200 and covers the positioning hole 400. In other words, the structural element 200 is located between the wing skin 100 and the spark protection cap 300. The second opening 402 of the positioning hole 400 can be used as a visual guide to help correctly position the wing skin 100 relative to the structural element 200 and the spark protection cap 300.

[0043] exist Figure 2d A fastening through-hole 500 is formed in the wing skin 100. The fastening through-hole 500 is used to receive a fastener 600 that fastens the wing skin 100 to the structural element 200. The fastening through-hole 500 is formed by drilling a hole from the wing skin 100 through the structural element 200 along the path of the positioning through-hole 400 using a drill 70. The fastening through-hole 500 follows the path of the positioning through-hole 400, thereby leading to the interior of the spark shield 300. The diameter of the fastening through-hole 400 is larger than the diameter of the positioning through-hole 400, generally matching the diameter of the fastener 600 inserted through the fastening through-hole 500. For example, the fastener 600 can be a fastener with a diameter of 1 / 4 inch (6.35 mm), and the fastening through-hole 500 has an equal diameter. Forming the fastening through hole 500 along the path of the locating through hole 400 effectively enlarges the locating through hole 400, or in another sense removes the locating through hole 400 by replacing the locating through hole 400 with the larger fastening through hole 500. After forming the fastening through hole 500 and removing the drill 70, the swarf can be cleaned from the fastening through hole 500.

[0044] exist Figure 2e , the fastener 600 is inserted into the fastening through hole 500 . The wing skin 100 is fastened or fixed to the structural element 200 by the fastener 600 .

[0045] Fastener 600 is a single-sided fastener and can be tightened from the side of the wing skin, outside the aircraft, without requiring access to the interior of the aircraft for tightening. Fastener 600 may be, for example, a blind rivet or a blind bolt. Single-sided fastener 600 can be activated by, for example, rotating an internally threaded portion having a bulbous nose portion 602 formed at the trailing end of fastener 600, i.e., on the wing structure side 200 of fastener 600. The wing structure 200 and wing skin 100 are clamped between bulbous nose portion 602 and a head portion 604 located on the wing skin side of the fastener, thereby fastening the wing structure 200 to the wing skin 100. Single-sided fastener 600 may include a frangible portion that is operable to rotate the single-sided fastener during tightening, but that can be removed, for example, once installed.

[0046] Depending on the precise design of the fastener 600, fastening the wing skin 100 to the structural element 200 may occur, for example, as part of, or at least partially, the insertion of the fastener 600 into the fastening through-hole 500. For example, the fastener 600 may be threaded, and thus, inserting the fastener 600 into the fastening through-hole 500 may involve rotation of the fastener 600, which also serves, for example, to at least partially secure the structural element 200 to the wing skin 100. In other examples, the fastener 600 may be fully inserted into the fastening through-hole 500 before fastening the wing skin 100 to the structural element 200. For example, the end of the fastener 600 on the side of the structural element 200 is received within the spark protection cap 300, thereby protecting the interior of the aircraft wing 50 from spark risks.

[0047] Figure 3 and Figure 4 Temporary fasteners 700a, 700b are inserted through the locating holes 400 and used to temporarily secure the spark protection cap 300 to the structural element 200 before adhesive or other fastening means permanently secure the spark protection cap 300 to the structural element 200.

[0048] exist Figure 3 In the example shown, a threaded temporary fastener 700a is illustrated. The threaded temporary fastener 700a has a head 710a and a threaded body 704. The spark protection cap 300 has a threaded receiving portion 314 at the distal end of the spark protection cap 300, furthest from the opening of the positioning through-hole 400 and the structural element 200. The inner diameter of the threaded receiving portion 314 matches the diameter of the threaded body 704 of the threaded temporary fastener 700a. The threaded temporary fastener 700a has sufficient length so that the threaded body 704 can be received by the threaded receiving portion 314 of the spark protection cap 300 when inserted into the positioning through-hole 400. The threaded body 704 of the threaded temporary fastener 700a, in combination with the head 710a of the threaded temporary fastener 700a, can apply force to the spark protection cap 300, forcing the spark protection cap 300 into stronger contact with the structural element 200. This may help the structural element 200 adhere to the spark arrester cap 300 and prevent misalignment of the spark arrester cap 300 , for example due to accidental movement.

[0049] exist Figure 4 In the example of , an expandable temporary fastener 700b is used, such as a Clayco fastener. This serves the same purpose as Figure 3The expandable temporary fastener 700b functions similarly to the threaded temporary fastener 700a. The expandable temporary fastener 700b includes a flared flange portion 720 that can expand and contract, thereby allowing insertion through the positioning through-hole 400 when contracted, but preventing or inhibiting removal through the positioning through-hole 400 when expanded. Once the spark protection cap 300 is permanently attached to the structural element 200 via adhesive or the like, the head 710b of the snap-lock pin-type temporary fastener 700b can facilitate removal of the temporary fastener. For example, removal of the temporary fastener 700b may involve shearing off the flared flange portion 720.

[0050] exist Figure 4 In the example shown, a washer 318 is disposed within the spark protection cap 300 to allow the flared flange portion 720 to engage with the washer 318 located near the base of the spark protection cap 300. However, in other examples, the function of the washer 318 may be facilitated by another surface of the spark protection cap 300, such as the flared flange portion 720 directly engaging a portion of the base of the spark protection cap 300. More generally, it will be understood that this surface is positioned so that it engages the temporary fastener 700 when the temporary fastener is withdrawn from the through-hole. The washer 318 may be formed of an electrically insulating material to enhance the spark resistance of the spark protection cap 300. The washer 318 may have a metal core, for example, a metal core with an insulating or dielectric coating, such as ceramic or paint.

[0051] The fastening through-holes 500 are typically positioned by references provided on the wing skin and the wing fixture in order to align the positioning through-holes 400 with the fastening through-holes 500 , but during manufacturing, an offset may be introduced between the positioning through-holes 400 and the fastening through-holes 500 . Figure 5 The schematic diagram illustrates a situation in which, due to the blind nature of the installation process, the drill 70 aligned along the index axis F, and the resulting fastening through-hole 500, is misaligned with the positioning through-hole 400 aligned along the index axis P. However, because the diameter of the positioning through-hole 400 is smaller than that of the fastening through-hole 500, the fastening through-hole 500 can still completely overlap with the positioning through-hole 400, thereby eliminating the positioning through-hole 400. In this sense, minimizing the size of the positioning through-hole 400 allows for the provision of a temporary fastener 700 to temporarily secure the spark protection cap 300 to the structural element 200, while also allowing for easy removal of the temporary fastener 700 during the formation of the fastening through-hole 500. If a larger through-hole were used in place of the positioning through-hole 400, there is a risk that the diameter of the fastening through-hole 500 would not completely overlap with the diameter of the positioning through-hole 400, potentially resulting in a non-circular hole. For example, a fastener 600 placed in such a non-circular hole could become unstable.

[0052] Those skilled in the art will be familiar with the use of commonly used standard metric drill bit sizes and fractional inch drill bit sizes, as well as drill bit sizes in any other specific system. The examples described herein may, for example, use a 2 mm, 2.4 mm, 2.8 mm, or 3.2 mm drill bit when forming a pilot hole, which, as those skilled in the art will understand, corresponds approximately to a 5 / 64 inch, 3 / 32 inch, 7 / 64 inch, or 1 / 8 inch drill bit, respectively, in the fractional inch drill bit system. These sizes are provided as examples only, and those skilled in the art will understand that other diameters may be used.

[0053] It should be noted that the term "or" used herein should be interpreted as meaning "and / or" unless explicitly stated otherwise.

Claims

1. A method of attaching a wing skin to a structural element of an aircraft wing, the method comprising: forming a positioning through-hole in a structural element, the positioning through-hole extending along a path between a first side portion of the structural element and a second side portion of the structural element; attaching a spark protection cap to the first side portion of the structural element, the spark protection cap covering the opening of the positioning through hole; positioning a portion of the wing skin on the second side of the structural element; forming a fastening through-hole having a diameter larger than that of the positioning through-hole and passing through both the wing skin and the structural element and along the path of the positioning through-hole, such that the fastening through-hole comprises: a first opening located in the wing skin, and a second opening located in the structural element and covered by the spark arrester cap; as well as A fastener is inserted into the fastening through-hole and the structural element is fixed to the wing skin, with an end portion of the fastener being covered by the spark protection cap.

2. The method according to claim 1, wherein Attaching the spark protection cap includes providing a temporary fastener within the locating through-hole, the temporary fastener being configured to secure the spark protection cap to the structural element.

3. The method according to claim 2, wherein: The temporary fastener is threaded, and the spark arrester includes a corresponding threaded receiving portion configured to receive the threaded portion of the temporary fastener.

4. The method according to claim 2, wherein: The temporary fastener is a snap-lock pin type fastener, and the spark arrester cap includes a surface arranged such that when the temporary fastener is inserted into the spark arrester cap, the temporary fastener engages the surface to prevent removal from the spark arrester cap.

5. A method according to any preceding claim, wherein: The spark arrester includes a washer.

6. The method according to claim 5, wherein: The gasket is formed of an electrically insulating material.

7. The method according to claim 5 or 6 when dependent on claim 4, wherein The surface that engages the temporary fastener is the washer.

8. A method according to any preceding claim, wherein: The spark protection cap includes a portion configured to receive an adhesive for attaching the spark protection cap to the structural element, and wherein attaching the spark protection cap to the first side of the structural element includes providing the adhesive and curing the adhesive.

9. The method according to claim 8, wherein The portion is a skirt provided along a circumference of the spark protection cap, the skirt being configured such that adhesive provided to the skirt is confined within the skirt.

10. A method according to any preceding claim, wherein: The diameter of the positioning through hole is smaller than half of the diameter of the fastening through hole.

11. The method according to claim 10, wherein: The diameter of the positioning through hole is smaller than one quarter of the diameter of the fastening through hole.

12. The method according to claim 10 or 11, wherein: The diameter of the fastening through hole is greater than three quarters of the inner diameter of the spark protection cap.

13. A method according to any preceding claim, wherein: The structural element is a rib or a spar of the aircraft wing.

14. A method according to any preceding claim, wherein: The structural element forms a portion of a fuel tank, and the spark arrester is disposed within the fuel tank.

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