Manufacturing a rib for an aircraft wing

Abstract

A method of manufacturing a rib 130 for an aircraft wing by providing a web and depositing layers of material on the web to form at least one stiffening structure 134 on the web. The stiffening struct

Description

TECHNICAL FIELD

[0001] The present invention relates to a method of manufacturing a rib of an aircraft wing. B ACKGROUND

[0002] Aircraft wing boxes are typically manufactured by forming a sub-structure by assembling components - for example, including ribs and spars - and then mounting preformed wing skins on the sub-structure.

[0003] In the overall assembly, there are generally upper and lower wing skins which extend between front and rear spars. The ribs are typically provided in the wing box of an aircraft to provide support for the upper and lower wing skins by being attached to each of them, as well as extending between the spars.

[0004] Known ribs comprise a web which is disposed between a series of rib feet associated with the upper wing skin and a series of rib feet associated with the lower wing skin. The rib feet may, in use, be attached to other components of the aircraft wing box, such as stringers.

[0005] Highly-1oaded ribs in particular must support large load inputs to the wing caused by out-of-plane loads including lateral loads which can induce bending moments and stresses on the wings, and torsional loads which can create twisting moments along the span of the wing, causing the wing to twist or warp. These effects can influence the handling characteristics of the aircraft.

[0006] Generally, a known rib is machined from a solid, cuboidal, unitary block of metal material, known as a billet. SUMMARY

[0007] A first aspect of the present invention provides a method of manufacturing a rib for an aircraft wing, the method comprising: providing a web; and depositing layers of material on the web to form a stiffening structure on the web.

[0008] Machining ribs from billets requires that any increase to the size of a rib requires a larger billet. However, as will be appreciated, this increase in size corresponds to a larger volume of waste material which does not comprise the final rib. Although some of this material may be recycled for the manufacture of smaller parts, it would be preferable to reduce the volume of material which is considered waste in order to reduce the costs of the billets.

[0009] The incorporation of stiffening structures such as projected members on a surface of the web may increase the strength of the overall rib. The term “projected” refers to being extended from a surface. Specifically, such stiffening structures reduce the tendency of the rib to buckle under compression by improving the resistance of the rib to compressive forces.

[0010] The first aspect advantageously provides a method by which at least part of the rib may be formed by additive manufacturing rather than subtractive manufacturing techniques such as milling. Hence, substantially all of the deposited material comprises part of the final rib and there is comparatively little to no waste material. In configurations where the web is pre-formed in a process which does not comprise additive manufacturing, the web may provide a substrate on which the stiffening structures may be formed by additive manufacturing. Advantageously, this does not require a separate joining step.

[0011] The term “subtractive manufacturing” refers to any manufacturing process that involves the removal of material from a solid workpiece to achieve the shape of the final product. This includes, but is not limited, to processes such as cutting, drilling, milling, turning, and grinding.

[0012] The term “additive manufacturing” refers to any manufacturing process that involves the addition of material, layer by layer. Additive manufacturing builds up the final product.

[0013] For steps requiring the deposition of material, the material deposited may comprise molten metal. For example, the material may be deposited by a direct energy deposition process. In a direct energy deposition process, a high-energy heat source, such as a laser or an electron beam, is directed onto a substrate using a deposition head. The high-energy heat source melts and fuses a feedstock, creating a solid layer. The deposition head and the high-energy heat source are moved to build up the component in layers.

[0014] The direct energy deposition process may comprise a powder-fed feedstock. A powder-fed feedstock is generally in the form of small particles or powder. This powder material is typically composed of metals, alloys, ceramics, or other materials suitable for direct energy deposition. Powder feedstocks present several advantages such as being useable with a broad variety of materials. Such feedstocks are also capable of depositing a mixture of multiple materials, which makes it possible to manufacture components with specific or graded properties.

[0015] In some configurations, the direct energy deposition process may comprise a wire-fed stockfeed. A wire-fed feedstock is generally in the form of solid wire comprising the desired material of manufacture. Wire feedstocks offer simplified handling processes with reduced a minimised risk of contamination.

[0016] The web may be provided by depositing layers of material on a substrate. Thus, the web may be provided by means of an additive manufacturing process. For example, the web may be provided by means of a direct energy deposition process. The web and the at least one stiffening structure may be formed as part of a same deposition process.

[0017] In other configurations, the web may be provided by known, subtractive manufacturing processes. For example, the web may be milled from a billet. The web may subsequently be used as a substrate as layers of material may be deposited on the web to form the at least one stiffening structure.

[0018] The web may comprise a first surface on one side and a second surface on an opposing side. The first surface may be planar. The second surface may be planar. A planar surface refers to a surface which defines a substantially flat plane. In configurations where both the first and the second surface of the web are planar, the first surface and the second surface may be parallel to one another.

[0019] The method may comprise forming at least one stiffening structure on the first surface. The at least one stiffening structure may comprise a plurality of stiffening structures.

[0020] The provision of a plurality of stiffening structures may yield a rib with a greater stiffness. Furthermore, the plurality of stiffening structures can be distributed along the first surface or the second surface of the web to provide more uniform mechanical properties to the rib.

[0021] The method may comprise forming at least one of the plurality of stiffening structures on the first surface and forming at least one of the plurality of stiffening structures on the second surface. The plurality of stiffening structures may comprise a first plurality of stiffening structures and a second plurality of stiffening structures. In such configurations, the method may comprise: forming the first plurality of stiffening structures on the first surface; and forming the second plurality of stiffening structures on the second surface.

[0022] When forming a highly loaded wing rib, it may be preferable to provide stiffeners on both surfaces of the rib. In such instances, billets of doubled volume may be required and thus there can be as much as double the waste material. Additionally, it can be time consuming to manually reposition a workpiece in order to machine the opposing surface of the rib. To mitigate this, such ribs are often formed by the production of two separate ribs which are subsequently fastened together. Such a step can present the disadvantage of protracted manufacturing by requiring a further process. It will also be appreciated that the resulting rib is also made heavier by the incorporation of fasteners.

[0023] A longitudinal axis of the rib extends between a first axial end of the web and a second axial end of the web. In configurations where both the first and the second surface of the web are planar, the longitudinal axis of the rib may be defined through the web, parallel to the first surface and second surface.

[0024] At least one foot may be provided to the rib. The at least one foot may extend from the first axial end of the web. The at least one foot may extend at an angle which is oblique or transverse to the first surface or the second surface of the web. Specifically, the at least one foot may extend from the web at an angle which is non-parallel to the first surface or the second surface of the web.

[0025] The at least one foot may be provided by forming layers of material on the web, at the first axial end or the second axial end.

[0026] The web may comprise at least one foot extending from the second axial end of the web, at an angle which is oblique or transverse to the first or second surface of the web. That is, the web may comprise at least one foot extending from the second axial end of the web, at an angle which is non-parallel to the first or second surface of the web.

[0027] A plurality of feet may be provided to the rib. The plurality of feet may extend from the first axial end of the web or the second axial end of the web. In such configurations, the cross-section of the rib comprises an “L” or a “T” cross-section. In some embodiments, the plurality of feet may extend from each of the first axial end of the web and the second axial end of the web. In such configurations, the cross section of the rib comprises an “I” cross-section.

[0028] The rib may be formed as a unitary component. A “unitary component” refers to a component which comprises a single body without requiring separate steps of joining or fastening. This may reduce the weight of the rib and may reduce stress concentrations which may be introduced by joints or fasteners.

[0029] The at least one stiffening structure may extend in a horizontal direction. The horizontal direction is substantially parallel to the spanwise direction. The at least one stiffening structure may extend in a vertical direction. The at least one stiffening structure may extend in a diagonal direction.

[0030] In configurations with a plurality of stiffening structures, stiffening structures extending in different directions may connect at a junction. A pocket may be defined between a plurality of stiffening structures. The term “pocket” refers to a compartment defined by boundaries, the boundaries being defined by the stiffening structures. The pocket may be configured to accommodate components or systems of the aircraft. The stiffening structures may define a plurality of pockets. The plurality of pockets may comprise a first plurality of pockets and a second plurality of pockets. In such configurations, the first plurality of pockets may be defined on the first surface of the web; and the second plurality of pockets may be defined on the second surface of the web.

[0031] A capacity of the pocket is defined by dimensions of the stiffening structures by which the boundaries of the pocket are defined. Specifically, the depth of the stiffening structures corresponds to the volume of the associated pocket.

[0032] A maximum depth of the stiffening structures, and thus the pockets, may be at least 50mm, for example.

[0033] Stiffening structures of greater depth generally provide the rib with a greater resistance to compressive forces, but may also increase the size of the billet required when using subtractive manufacturing techniques.

[0034] Additionally, a rib having stiffening structures with greater depths corresponds to more resistance to bending or deformation under load. This can help the rib, and thus the wing, to maintain shape and structural integrity. A maximum thickness of the at least one stiffening structure may be at least 1 mm. In other embodiments, the maximum thickness of the at least one stiffening structure may be at least 10 mm.

[0035] With typical subtractive manufacturing techniques, the dimensions of the final rib are constrained by at least two considerations. Firstly, when using conventional subtractive manufacturing techniques such as milling, the drill bit can only penetrate down to a maximum axial depth of cut. This is largely constrained by the dimensions of the drill bit itself. Overall axial length of the drill bit constrains the maximum axial depth of cut. Further, the radius of the drill bit constrains the depth of cut as cutting forces are distributed across the cutting edges of the tool. The maximum force occurs at the centre of the radius, and therefore an increased radius corresponds to a greater possible depth of cut as the forces are less concentrated. However, increasing the radius of the drill bit also reduces the precision of the corresponding cuts. The depth of the billet is also constrained by cost, as acquiring increasing large billets can be impractical. If intending to form especially deep stiffening structures, the billet may present an increased cost while also requiring a larger drill bit.

[0036] Thus, by using additive manufacturing techniques, the depth of the stiffening structures is neither constrained by the dimensions of a starting workpiece, such as a billet, nor by any physical parameters of the tools used to make it. This makes it possible to form deeper stiffening structures and thus produce ribs which are more resistant to compressive or tensile forces.

[0037] A second aspect of the present invention provides a rib formed by the method according to the first aspect of the present invention.

[0038] A third aspect of the present invention provides an aircraft wing comprising the rib according to the second aspect of the present invention.

[0039] A fourth aspect of the present invention provides an aircraft comprising the aircraft wing according to the third aspect of the present invention.

[0040] Optional features of aspects of the present invention may be equally applied to other aspects of the present invention, where appropriate. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0042] Figure 1 shows a schematic illustration of an aircraft;

[0043] Figure 2 shows a schematic illustration of an aircraft wingbox;

[0044] Figure 3 shows a schematic illustration of a rib manufactured with an example method; and

[0045] Figure 4 shows a flow diagram of an example method. DETAILED DESCRIPTION

[0046] Figure 1 shows an aircraft 1. The aircraft comprises a pair of wings 10 which are attached to and extend from a fuselage 20. The wings 10 comprise several internal structural features, as detailed further with reference to Figures 2 and 3.

[0047] Figure 2 shows a schematic illustration of a wingbox 100 of one of the wings 10 of the aircraft comprising several spars 110 and a series of ribs 130. The wingbox 100 is a structural framework designed to provide an associated wing, for example, either of the wings 10, with shape and rigidity.

[0048] The wingbox 100 comprises a leading edge 101 and a trailing edge 102. The leading edge 101 comprises a surface which faces into the oncoming airflow as the aircraft 1 moves forward. Thus, the leading edge 101 is the foremost part of the wing 10 during flight. The trailing edge 102 is the rear edge and is the part of the wing where the airflow recombines after passing over the curved surface of the wing. Control surfaces, such as ailerons, flaps, and trailing-edge flaps, are generally located at or proximal to the trailing edge 102.

[0049] The wingbox 100 further comprises a wing root 103 and a wing tip 104. The wing root 103 is the innermost part of the aircraft wing, where the wing attaches to the fuselage (not shown) of the aircraft. The wing tip 104 the outermost part of the aircraft wing, located at the far end of the span of the wing. A lateral axis L extends between the wing root 103 and the wing tip 104. The lateral axis L defines a spanwise direction. The spanwise direction is generally perpendicular to a longitudinal axis of the aircraft 1, which is the axis that runs from a nose of the aircraft 1 to a tail thereof. It is also perpendicular to a chord line of the wing, which is an axis that extends between the leading edge 101 and the trailing edge 102.

[0050] Figure 2 shows that, within the wingbox 100, a plurality of spars 110 extend perpendicular to the spanwise direction. Though depicted with a pair of spars 110, the wingbox 100 may otherwise comprise a single spar. In some configurations, the wingbox 100 may alternatively comprise three or more spars. The spars 110 comprise horizontal structural beams oriented parallel to the spanwise direction. The spars 110 generally extend between the wing root 103 and the wing tip 104. The function of the spars 110 is to distribute lift and bending moments along the span of the wing, and thus they are configured to withstand both tension and compression loads.

[0051] The structural framework within the wingbox 100 is enclosed by wing skins 120. The wing skins generally comprise an upper wing skin 121 and a lower wing skin 122.

[0052] The upper wing skin 121 comprises the outermost surface of the wing that faces the top of the aircraft 1 during flight. As a wing ordinarily comprises a cambered upper aerofoil surface, the upper wing skin 121 typically comprises a corresponding curvature. In flight conditions, the upper wing skin 121 is exposed to a higher airflow velocity than the lower wing skin 122. This results in increased shear stresses on the upper wing skin 121 which require it to have an increased shear strength. Flight conditions also exert loads which pull the material of the upper wing skin 121 apart. This is in conjunction with the compressive loads exerted on the upper wing skin 121 when lift deflects the wing upwards. In order to withstand these conditions, the upper wing skin 121 must have adequate tensile strength and compressive strength.

[0053] Meanwhile, the lower wing skin 122 comprises the outermost surface of the wing that faces the bottom of the aircraft during flight. The lower skin 122 ordinarily comprises a less pronounced curvature compared to the upper wing skin. In flight conditions, the lower wing skin 122 is exposed to a higher air pressure than the upper wing skin 121. Due to the weight of the wing causing the wing to deflect downwards, the lower skin 122 requires sufficient compressive strength to withstand these forces.

[0054] As noted above, the wingbox 100 comprises ribs 130. As shown in Figure 2, each of the plurality of ribs 130 extend perpendicular to the spanwise direction. That is, each of the plurality of ribs 130 extend between the leading edge 101 and the trailing edge 102 of the wing. The provision of the plurality of ribs 130 to the wingbox 100 serves several functions. The plurality of ribs 130 define the aerofoil geometry of the wing and therefore provide the frame for the junction of the wing skins 120. Because of this, the wing skins 120 may be attached to the ribs 130 using fasteners or adhesive bonding.

[0055] The ribs 130 comprise streamlined cross-sections as they define the geometry of the aerofoil. Hence, the ribs 130 define the leading edge 101 and the trailing edge 102 of the wing. As can be seen in Figure 2, the leading edge 101 is rounded or curved in shape. This curvature is designed to smoothly guide the incoming air over the upper skin 121 of the wing. Meanwhile, the trailing edge 102 is straighter, and less curved, than the leading edge 101.

[0056] Figure 3 illustrates an enlarged view of one of the plurality of ribs 130. The rib 130 comprises a web 131. The web 131 defines a central portion of the rib 130 and provides rigidity to the overall structure of the rib 130. In the example of Figure 3, the rib 130 is formed from 7010 aluminium. The rib 130 is typically constructed from strong but lightweight materials, such as metal alloys. Light metal alloys in particular may present advantageous mechanical properties.

[0057] To further reduce weight without compromising structural integrity, the web may comprise lightening holes 132. Defining apertures through the web 131, the lightening holes 132 serve two purposes. Firstly, they significantly reduce the overall weight of the rib 130, which contributes to the overall weight savings and fuel efficiency of the aircraft. Second, these lightening holes 132 enhance the resistance of the rib 130 to bending and torsional forces, as they effectively distribute the stresses across the remaining material. The placement and size of the lightening holes 132 are determined to achieve a balance between weight reduction and structural performance.

[0058] The rib 130 further comprises a plurality of feet 133. Located at an upper and / or lower extent of the rib 130, the feet 133 comprise extensions which interface with other components of the wing structure. For example, the feet 133 may connect the rib 130 to the spars 110 or wing skins 120. The rib feet 133 facilitate a secure connection to the spars 110 or wing skins 120 and, through this connection, distribute the aerodynamic and structural loads from the wing skins 120 and ribs 130 to the wing spars 110 during flight.

[0059] In Figure 3, the web 131 comprises a plurality of stiffening structures 134. The stiffening structures 134 comprise projected members on a surface of the web 131. Thus, the ribs extend from the surface on which they are arranged. The plurality of stiffening structures 134 on the web 131 enhance the strength, rigidity of the rib 130. Thus, the rib 130 better withstands various aerodynamic and structural loads experienced during flight. The stiffening structures 134 are formed along the surface of the web 131, extending from the surface in the spanwise direction. Thus, the stiffening structures 134 extend along the lateral axis L of the wing. The stiffening structures 134 prevent buckling or flexing of the web 131 under loads during flight conditions, which can be advantageous for maintaining overall shape and structural integrity of the wing.

[0060] In addition to preventing deformation under load, stiffening structures also contribute to the resistance of the rib 130 to torsional forces and twisting by distributing stresses evenly across the surface of the web 131. As shown in Figure 3, the stiffening structures 134 may vary in shape, size, and placement. For example, some of the stiffening structures 134 extend in a horizontal direction. The horizontal direction, in-situ (as in Figure 2), is substantially parallel to the spanwise direction. That is, the horizontal direction in relation to the rib 130 extends between the leading edge 101 and the trailing edge 102. Further, some of the stiffening structures 134 extend in a vertical direction. The vertical direction, in-situ, extends between the upper wing skin 121 and the lower wing skin 122. Some of the stiffening structures 134 may extend in a diagonal direction. The term diagonal refers to any angle which is oblique relative to the vertical direction or the horizontal direction.

[0061] Stiffening structures 134 extending in different directions define junctions 136 where they connect. As shown in Figure 3, stiffening structures 134 extending in different directions bound pockets 135. In this context, the term “pocket” refers to a compartment defined by boundaries. Thus, the pockets 135 are defined by the junctions formed by the stiffening structures 134 extending in different directions. The pockets 135 may be used to accommodate components or systems of the aircraft. The capacity of each pocket 135 is defined by the depth of the stiffening structures 134 by which it is bounded. Deeper stiffening structures 134 may therefore define pockets 135 of greater volume.

[0062] The rib 130 comprises a first surface 137 and a second surface 138. In the configuration of Figure 3, both the first surface 137 and the second surface 138 are substantially planar. As can be seen, the stiffening structures 134 are arranged on both the first and the second surfaces 137, 138 of the web 130.

[0063] Stiffening structures 134 formed from a method described with reference to Figure 4 may advantageously allow the manufacture of pockets 135 with greater volume. This in turn allows for the accommodation of more components, or larger components.

[0064] The stiffening structures of known ribs may be formed by machining processes. Generally, the stiffening structures may be machined as part of the web. As known ribs are machined from a solid billet, this approach is limited when manufacturing thicker stiffening structures.

[0065] Alternatively, the stiffening structure of other known ribs may be formed in separate machining processes to the associated webs in order to reduce the waste material from the initial billet. These stiffening structures are subsequently joined, typically by fastening, adhesive, or welding to the associated webs. This can be suboptimal as fasteners, adhesive, and welding can introduce stress concentrations where forces are localised. These stress concentrations can lead to material fatigue and structural failure over time. Further, fastenings, adhesive, and welding increase the total weight of the rib.

[0066] Aircraft wings are designed to withstand significant aerodynamic loads, including moments due to lift and weight which may cause the tips of the wings to bend significantly upwards or downwards. The components of the wingbox 100 must therefore be configured to accommodate these forces.

[0067] Figure 4 illustrates a method 200 for manufacturing one of the ribs 130.

[0068] According to a first step 201 of the method 200, the web 131 is provided. The web 131 may be formed by any appropriate means. Preferably, the web is provided by means of an additive manufacturing process. Such processes may include, but are not limited to: sintering techniques, jetting techniques, electron beam melting, selective laser melting, powder bed fusion and direct energy deposition. It will be understood, in one embodiment, that steps 202-204 can be used to inform the skilled reader as to how to form the web.

[0069] Once provided, the web 131 is subsequently used as a substrate for the formation of the stiffening structures 134. Layers of material are deposited on the web 131 to form the stiffening structures 134. For an additive manufacturing technique, a computer-aided design model is generally provided to an associated machine.

[0070] When performing the method using a direct energy deposition process, the web 131 may be heated to a specific temperature according to step 202. This step may help prevent thermal shock, which may occur when hot molten material is deposited onto a cold surface, potentially leading to cracking or poor bonding. Further, pre-heating promotes improved adhesion between the deposited material and the web 131, in turn improving the structural integrity of the final rib. Additionally, by bringing the web 131 to a raised temperature, it ensures that the material is within the ideal range for fusion and metallurgical compatibility.

[0071] In a direct energy deposition process, a deposition head is arranged over a build area. A machine for direct energy deposition (not shown) comprises several features including: a build platform on which a component may be formed; a deposition head for depositing material; a high-energy power source, such as a laser beam or an electron beam; and a feed, for receiving the material to be deposited. Direction energy deposition processes have high deposition rates which allows for quick fabrication of components. High-speed direct energy deposition processes may be conducted at up to 10 kilograms per hour of material or more, for example.

[0072] According to step 203, a feedstock is provided to the feed. The direct energy deposition process may comprise a powder-fed feedstock. In such configurations, the feed of the machine may comprise a reservoir configured to store the powder feed and supply it to the deposition head. In other configurations, the direct energy deposition process may comprise a wire-fed stockfeed. In such configurations, the feed of the machine may comprise a wire feeder configured to store the wire feed and supply it to the deposition head.

[0073] According to step 204, the deposition head then deposits material to form a feature. When forming the web 131, for example, the material is deposited onto a substrate. When forming the stiffening structures 134, the deposition head deposits material onto a first surface 137 of the web 131. To perform this step, material stored in the feed of the machine is supplied to the deposition head of the machine and heated by the high-energy power source such that the feedstock is rapidly melted. The path of the deposition head is generally specified by the computer-aided design model. As the material is deposited onto the substrate, it adheres to the substrate by fusion. The term “fusion” refers to the process of joining features together by melting and then solidifying one or each them into a single unitary component. When forming the stiffening structures 134, the material deposited on the web 131 adheres thereto. The adhesion during the process of direct energy deposition rib therefore advantageously forms the rib as a unitary component. Throughout the process, the temperature of the substrate may be controlled in order to manage thermal stress. The build platform may then be lowered to perform the same process for the next layer. Alternatively, the deposition head may be raised before performing the same process for the next layer.

[0074] In some processes, when forming stiffening structures, the method may comprise step 205. in this step, the web is repositioned and step 204 is repeated on a second surface 138 of the web 131. A rib provided with stiffening structures on both surfaces advantageously comprises more robust tensile and compressive strength properties. This can also be used to provide the rib 130 with pockets 135 defined on both the associated first and second surfaces 137, 138. Such a configuration is advantageous because, in use, it can increase the volume available for storing components.

[0075] With the method 200, the machine for direct energy deposition may comprise a 6-axis deposition head. A 6-axis deposition head refers to a tool with three linear axes for horizontal, vertical, and depth movements; as well as three rotational axes, which allows the tool to be rotated about each of the linear axes. Such a deposition head enables formation of more complex geometries and overhangs. An overhang refers to a feature which that extends beyond the structure by which it is supported to form an unsupported projection.

[0076] The use of additive manufacturing also enables the use of topology optimisation for the manufacture of the ribs. This is generally performed computationally and can result in structural features for the rib which are difficult to achieve with subtractive manufacturing techniques. These features include, but are not limited to, the inclusion of overhangs, lattices, honeycomb structures, hollow structures, internal channels and passageways, or nested parts. Such structures, when formed from subtractive manufacturing techniques, would result in significant waste material and prolonged production times.

[0077] It is to be noted that the term “or” as used herein is to be interpreted to mean “and / or”, unless expressly stated otherwise.

Claims

1. A method of manufacturing a rib for an aircraft wing, the method comprising: providing a web; anddepositing layers of material on the web to form at least one stiffening structure on the web.

2. The method of claim 1, wherein the material is deposited by a direct energy deposition process.

3. The method of claim 2, wherein the direct energy deposition process comprises a powder-fed feedstock.

4. The method of claim 2, wherein the direct energy deposition process comprises a wire-fed feedstock.

5. The method according to any preceding claim, wherein the web is provided by depositing layers of material on a substrate.

6. The method according to any preceding claim, wherein the web comprises a first surface on one side and a second surface on an opposing side; the method comprising forming the at least one stiffening structure on the first surface.

7. The method according to claim 6, wherein the at least one stiffening structure comprises a plurality of stiffening structures; the method comprising:forming at least one of the plurality of stiffening structures on the first surface; andforming at least one of the plurality of stiffening structures on the second surface.

8. The method of according to claim 7, wherein the plurality of stiffening structures comprises a first plurality of stiffening structures and a second plurality of stiffening structures, the method comprising:forming the first plurality of stiffening structures on the first surface; and forming the second plurality of stiffening structures on the second surface. .

9. The method according to any preceding claim, wherein the web defines a longitudinal axis extending between a first axial end thereof and a second axial end thereof; and the web comprises at least one foot extending from the first axial end of the web.

10. The method according to claim 9, wherein the web comprises a plurality of feet, wherein at least one of the plurality of feet extends from the first axial end of the web; and at least one of the plurality of feet extends from the second axial end of the web.

11. The method of any preceding claim, wherein the rib is formed as a unitary component.

12. The method of any preceding claim, wherein a maximum depth of the at least one stiffening structure is at least 50 mm.

13. A rib formed by the method of any preceding claim.

14. An aircraft wing comprising the rib of claim 13.

15. An aircraft comprising the aircraft wing of claim 14.Application No: GB2315873.6Examiner: Matthew LawsonClaims searched: 1-12Date of search: 1 March 2024Patents Act 1977: Search Report under Section 17Documents considered to be relevant:Category Relevant to claims Identity of document and passage or figure of particular relevance X 1-12 US 2021 / 0070419 Al (DECKER) - paragraphs [0024] &[0035] and figures 2A, 4A, 4B &4D. X 1-12 US 2016 / 0159464 Al (ALDERMAN) - paragraphs [0011] &[0027] and figures 2 &3. X 1 at least CN 111186140 A (UNIV) - paragraph [0001] and figure 2. X 1-5,9-12 US 2020 / 0216162 Al (GRAHAM) - paragraph [0072] and figure 4(c). X 1-12 US 2011 / 0147522 Al (WILLIAMS) - paragraphs [0029] &[0031 ] and figure 3. v A 1-12 International Journal of Advanced Manufacturing Technology, No. 123, 2022, R Dogea, "Additive manufacturing process design for complex aircraft components", pp. 4195-4211 X 1 at least Materials Science and Technology, Vol. 32, No. 7, 2016, SW Williams, "Wire + Arc Additive Manufacturing", pp 641-647 discussion on Figure 2d on page 642 and Figure 2d.Categories:v Au Document indicating lack of novelty or inventive step A Document indicating technological background and / or state of the art. Y Document indicating lack of inventive step if p Document published on or after the declared priority date but combined with one or more other documents of same category. before the filing date of this invention. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:The following online and other databases have been used in the preparation of this search reportWPI, EPODOC, Patent Fulltext, INSPECInternational Classification:Subclass Subgroup Valid From B64C 0003 / 18 01 / 01 / 2006 B33Y 0080 / 00 01 / 01 / 2015

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