Aircraft structural fitting

Abstract

A method of installing a first aircraft structure 101 onto a second aircraft structure 102 uses a movable joint 10 which allows relative movement between the two structures in at least a first degree of freedom to position them, the joint contains a curable substance 50, such as epoxy resin, which is cured to prevent movement of the joint and fix the structures relative to one another. The joint may be a ball joint having a socket 22 which is attached to the first structure, and a ball stud 32 attached to the second structure, allowing relative movement in six degrees of freedom before curing. The ball and socket may have a textured surface in contact with the resin which may coat the surface of the socket and the ball or be added after alignment. An external heat source may be used to cure the resin, or it may cure in a certain period of time. The structures may be a landing gear leg fairing and a landing gear leg, the positioning before curing allowing alignment of the fairing with an external surface of the aircraft when the leg in in a retracted position.

Description

TECHNICAL FIELD

[0001] The present invention relates to devices for attachment of aircraft structures, and methods of installing aircraft structures. B ACKGROUND

[0002] It is known that it is necessary to install aircraft structures securely and with accurate alignment relative to other aircraft structures. For example, secure and accurate installation of fairings is important for safety and achieving favorable aerodynamics. The installation process is typically time-consuming because it can involve multiple, iterative stages of alignment and adjusting fittings such as spools and studs in order to secure a fairing in a position which respects gap tolerances between the fairing and neighbouring aircraft structures, for example.

[0003] It is desirable to provide an improved device for attachment and installation of aircraft structures and a new method for attachment and installation of aircraft structures. SUMMARY

[0004] A first aspect of the present invention provides a fitting for alignment and attachment of a first aircraft structure to a second aircraft structure. The fitting comprises a first portion, a second portion and a joint. The first portion is attachable to the first aircraft structure, the second portion is attachable to the second aircraft structure, and the joint connects the first portion to the second portion. A curable substance is configured to be provided in at least a portion of the joint. The joint and curable substance are configured such that the fitting is arrangeable in a first state wherein the joint allows the first portion to be moved relative to the second portion such that when the first portion is attached to the first aircraft structure and the second portion is attached to the second aircraft structure, the first aircraft structure can be aligned relative to the second aircraft structure, and a second state in which the curable substance is cured such that movement of the first portion relative to the second portion is prevented. In this way, alignment of the first aircraft structure is fixed relative to the second aircraft structure.

[0005] The first aircraft structure and the second aircraft structure, in being attached together by such a fitting, can thereby be straightforwardly aligned until a desired position of the first aircraft structure relative to the second aircraft structure is determined. This can be a position which, for example, results in a particular separation between the first aircraft structure and a second aircraft structure. Once in the desired position, the curable substance can be cured to effectively lock or seize the joint of the fitting, as movement of the first portion relative to the second portion is prevented. This can hold the first aircraft structure in the desired position relative to the second aircraft structure. The straightforward installation avoids the need to mechanically adjust individual spools or studs to fasten or fix the aircraft structure in a desired position, and instead an engineer installing the first aircraft structure can straightforwardly cure the curable substance. This can decrease the installation time, for example, which simplifies the manufacture of an aircraft comprising the first and second aircraft structures. Furthermore, physically fastening convention fittings has a risk of disrupting the alignment of the first aircraft structure relative to the second aircraft structure, which can further lengthen an installation operation as the disrupted alignment is corrected. The relatively passive process of curing the curable substance can reduce a risk of disrupting the alignment.

[0006] The joint of the fitting can permit movement in just a first degree of freedom, for example, or may permit movement in multiple degrees of freedom, and can be selected based on the environment in which the first aircraft structure is being installed to the second aircraft structure. For example, the first aircraft structure may only require rotation relative to the second aircraft structure, or may only require translation along a particular axis relative to the second aircraft structure. Optionally, the joint is a ball-joint configured to, in the first state, allow for relative movement of the first portion and the second portion in at least three degrees of freedom, wherein the first portion comprises a socket of the ball-joint and the second portion comprises a ball-stud of the ball joint, and wherein the ball-stud is arrangeable within the socket. The ball-joint, in permitting at least three degrees of freedom, allows for more flexible alignment of the first aircraft structure such that an optimal desired position can be found.

[0007] Optionally, the socket and the ball-stud are configured to, in the first state, cooperate to permit relative movement of the first portion and the second portion in six degrees of freedom. By allowing for translation of the ball-stud within the socket, for example, alignment can occur in additional degrees of freedom, which can allow for more flexible alignment of the first aircraft structure than an optimal desired position can be found. That is, the ball-stud can be translated in x, y, and z directions within the socket, and can be tilted in yaw and pitch directions, and rotated in a roll direction, to thereby allow movement in six degrees of freedom.

[0008] Optionally, the curable substance is configured to coat at least some of a surface of the socket and at least some of a surface of the ball stud. The curable substance can be provided internally within the ball-joint, which can improve strength of the fitting in the second state. In some examples the curable substance coats substantially the entirety of an internal surface of the socket and the exterior surface of the ball stud such that, in the second state, the socket adheres to the ball stud at substantially all locations within the ball-joint. This can increase the maximal load-bearing strength of the fitting in the second state, and can improve the ability of the fitting to resist loads in different directions.

[0009] Optionally, at least one of the ball-stud and the socket comprises a textured surface configured to be in contact with the curable substance. The textured surface can improve adhesion of the curable substance with the respective component, such that the overall strength of the fitting when in the second state is improved. Additionally or alternatively, the ball-stud may be generally spherical in dimensions but more specifically be a polyhedron, comprising a plurality of facets and edges which help provide resistance against movement or rotation of the joint when the curable substance has been cured. For example, the ball-stud could comprise a icosahedral structure. Similarly, the internal surface of the socket may comprise facets and edges which also help the curable substance adhere and provide resistance against rotation or movement of the joint. Whilst the textured surface may in some examples just comprise, for example, relatively small-scale texture such as a coarse surface, in other examples it may comprise larger features such as dimples or cavities in the surface of the ball-stud or socket which also help strengthen the fitting by similarly providing regions for the curable substance to bond to

[0010] Optionally, the curable substance is curable by an external heat source. This allows the curable substance to be straightforwardly and selectively cured by an operator, for example. The curable substance may be curable above a predetermined threshold temperature which is unlikely to be reached without application of the external heat source, for example. Additionally, heat may not need to be directly applied to the curable substance, but instead may be applied to a nearby portion of the fitting, first aircraft structure or second aircraft structure, for example, and the heat conducted to the curable substance. This can further simplify the installation process compared with, for example, requiring the fitting to be directly physically accessible to the operator in order to fix a structure in position.

[0011] Optionally, the curable substance is configured to cure within a predeterminable, or predetermined, time period. The predetermined time period can be a time period in which the curable substance goes from providing no holding strength, such as in the first state, to having a holding strength sufficient to hold the first aircraft structure in alignment relative to the second aircraft structure. The holding strength may continue to strengthen over a second time period, but nevertheless the predetermined time period is suitable for the purpose of an installation procedure. The predetermined time period can be brought about by initiating a chemical reaction which results in the curable substance curing over a predetermined time period, for example. Such a chemical reaction may involve application of a second substance to the curable substance, for example. Introduction of heat to the curable substance may also or additionally help initiate the aforementioned curing process. The predetermined time period can be relatively short, for example less than 10 minute, or ideally less than 5 minutes, to minimise an installation time of the aircraft structures.

[0012] Optionally, at least a portion of the joint is configured to receive the curable substance from an external source after the first portion is aligned relative to the second portion. In this way, the first aircraft structure can be aligned relative to the second aircraft structure such that a desired installation alignment is reached, and then the curable substance provided and subsequently cured in order to prevent further movement of the first and second portion of the fitting. This may allow the alignment of the first portion relative to the second portion to be more accurately performed as it can reduce a risk that the cured substance affects the alignment process by, for example, partially curing during the alignment process. The external source may be a syringe or dispenser, for example, or an applicator such as a brush.

[0013] A second aspect of the present invention provides an aircraft structure comprising the fitting of the first aspect.

[0014] Optionally, the aircraft structure comprises a plurality of fittings. A plurality of fittings can improve the overall holding strength of the first aircraft structure to the second aircraft structure. The plurality of fittings may be substantially identical, within manufacture tolerances, or may have a range of designs, such as a mixture of fittings according to the first aspect.

[0015] The configuration of the plurality of fittings, such as their relative orientations and positions with respect to each other and / or the aircraft structure, can allow for weight of the aircraft structure to be distributed across the fittings according to a desired load distribution. For example, the load distribution could be that each fitting of the plurality of fittings bears an approximately equal allocation of the total weight of the aircraft structure, for example. This can improve the quality of the installation such that a need for maintenance of the fittings and / or aircraft structure is reduced, and prolong an operational lifespan of each fitting, for example.

[0016] Additionally or alternatively, the configuration of the plurality of fittings can be arranged to provide greater freedom of alignment in a first alignment direction relative to a second alignment direction, by effectively restraining the total degrees of freedom afforded to alignment of the aircraft structure, for example. This can be useful where there are a first set of tolerances with respect to the first alignment direction and a second set of tolerances with respect to the second alignment direction, wherein a set of tolerances can be a minimum or maximum separation between the aircraft structure and a neighbouring aircraft structure, for example. The first set of tolerances may be larger in magnitude than the second set of tolerances, and so it is desirable to restrict movement in the second alignment direction, for example, to reduce a likelihood that the second set of tolerances is not adhered to during installation of the aircraft structure.

[0017] Additionally, for aircraft structures are attached to surrounding aircraft structures by a plurality of conventional fittings, a sequence of fastening operations, such as tightening, may be undertaken, such that no individual fitting is overly-tightened relative to the rest of the plurality of fittings. In the present invention, it is straightforward to install the aircraft structure by simultaneously or near-simultaneously curing the curable substance provided in each joint, which thereby reduces a likelihood that the overall alignment of the aircraft structure is disrupted.

[0018] Optionally, the aircraft structure is a fairing. Fairings are typically provided externally to the aircraft and require precise and potentially complex alignment for aerodynamic performance. A fairing provided with such a fitting can be more straightforwardly installed, which can reduce a manufacture time for an aircraft.

[0019] Optionally, the fairing is a landing gear leg fairing. The landing gear leg fairing is required to move between positions as the landing gear is moved between deployed and stowed configurations. The landing gear leg fairing can be particularly complex to install as alignment with the surrounding aircraft structures can have a relatively high degree of variability compared with other aircraft structures. Installation of the landing gear leg fairing can require the landing gear leg fairing to be repeatedly moved between deployed and stowed configurations. Providing fittings according to the first aspect can thereby simplify the installation of the landing gear leg fairing, which can reduce a manufacture time for an aircraft.

[0020] In some examples, the curable substance is provided already disposed within the joint of the fitting, such as already coating a portion of a ball-joint prior to attachment to the first or second aircraft structures. In other examples, the curable substance is added at a later time, such as once an alignment process has been performed. In yet further examples, a first quantity of curable substance is already provided in the joint, and a second quantity of curable substance is provided at a later time, such as once an alignment process has been performed, to further strengthen the fixing effect provided by the first quantity of cured curable substance.

[0021] Accordingly, the joint of the fitting may permit movement in the first degree of freedom more easily during an alignment process, for example. Once the first aircraft structure is aligned relative to the second aircraft structure, the curable substance can be applied and cured to prevent movement of the first aircraft structure and the second aircraft structure. This can allow for the use of curable substances which might, if provided in the joint during the alignment process, be detrimental to the alignment process, but provide particularly strong fixation once cured, for example.

[0022] According to a third aspect there is an aircraft comprising the fitting according to the first aspect, or an aircraft structure according to the second aspect. Such an aircraft can be manufactured more quickly due to the simplified installation process described above.

[0023] According to a fourth aspect there is a method of installing a first aircraft structure to a second aircraft structure. The first aircraft structure is attached to the second aircraft structure by a movable joint allowing movement of the first aircraft structure relative to the second aircraft structure in at least a first degree of freedom, the movable joint comprising a curable substance configured to, when cured, prevent movement of the joint. The method comprises: positioning the first aircraft structure relative to the second aircraft structure in the at least first degree of freedom, and curing the curable substance such that the first aircraft structure is fixed relative to the second aircraft structure.

[0024] Optionally, curing the curable substance comprises applying heat to the curable substance. As described in relation to the fitting of the first aspect, this can allow the first aircraft structure to be fixed in position and alignment relative to the second aircraft structure without requiring direct physical access to fittings connecting the first aircraft structure to the second aircraft structure. The heat under which a curing process of the curable substance occurs can be sufficiently high that curing only occurs when an operator desires it to, and curing may not occur in response to an ambient temperature of a surrounding environment, for example. Application of heat to the curable substance may involve use of a warm-air heat gun, for example, or direction of electromagnetic waves such as infrared radiation towards the curable substance. In other examples, the curable substance may be cured in exposure to ultraviolet radiation, for example.

[0025] Optionally, the first aircraft structure is a landing gear leg fairing, and the second aircraft structure is a landing gear leg, and positioning the first aircraft structure relative to the second aircraft structure in the at least first degree of freedom comprises aligning the landing gear leg fairing with an external surface of the aircraft when the landing gear leg is in a retracted position. When the landing gear leg is in a retracted position, it may be difficult for the operator to access conventional fittings which are located internally with respect to the aircraft, but they may align the landing gear leg fairing from an external position to ensure the fairing is flush with surrounding external surfaces of the aircraft. However, with the present method, the curing can occur without direct involvement of the operator, and so the issue of accessing the internal fittings is avoided or reduced, for example. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0027] Figures la, lb show a schematic view of a fitting according to an embodiment of the present invention;

[0028] Figure 2a, 2b show a schematic view of a landing gear comprising the fitting of Figures la, lb;

[0029] Figures 3 and 4 show a flowchart illustrating methods for installation of aircraft structures according to embodiments of the present invention; and

[0030] Figure 5 shows a schematic view of an aircraft comprising a fitting according to an embodiment of the present invention. DETAILED DESCRIPTION

[0031] Figures la and lb show an example of a fitting 10 according to an embodiment of the present invention.

[0032] The fitting 10 is for attachment of a first aircraft structure 101 to a second aircraft structure 102. During an installation process in which the first aircraft structure 101 is attached to the second aircraft structure 102, the fitting 10 allows for the first aircraft structure 101 to be attached to and aligned relative to the second aircraft structure 102. Once a preferred alignment of the first aircraft structure 101 is achieved relative to the second aircraft structure 102, the fitting 10 is operable, in a manner which will be described hereafter, to prevent further movement of the first aircraft structure 101 to the second aircraft structure 102. The first aircraft structure 101 is thereby attached to the second aircraft structure 102 in the preferred alignment.

[0033] The fitting 10 comprises a first portion 20, a second portion 30 and a joint 40 which connects the first portion 20 to the second portion 30.

[0034] The joint 40, in this example, is a ball-joint. The first portion 20 comprises a socket 22 of the ball-joint which comprises an opening 23. The second portion 30 comprises a ball-stud 32 of the ball-joint. The ball-stud 32 has been inserted through the opening 23 and is retained within the socket 22 such that the first portion 20 is connected to the second portion 30, and such that the first portion 20 is reorientable relative to the second portion 30, and equally the second portion 30 is reorientable relative to the first portion 20. In the present example, the reorientation can occur in three degrees of freedom: for example, the first portion 20 may be tilted (indicated by yaw direction X, left-right on the page and pitch direction Z, into / out of the page) and rotated (indicated by roll arrow R) relative to the second portion 20. In forming the ball-joint 40, the ballstud 32 may, for example, be insertable through the opening 23 in a first orientation and subsequently reoriented into a second orientation wherein the opening 23 is too small for the ball-stud to be retrieved. Alternatively or additionally, for example, the socket 22 may be dismantlable into two or more portions and assemblable around the ball-stud 32 to form the ball-joint 40. It will be more generally appreciated that the joint is not limited to such examples.

[0035] When the ball-stud 32 is disposed within the socket 22, an interior surface 24 of the socket 22 forms an interface with an exterior surface of the ball-stud 32. A curable substance 50 forms a layer which coats the interior surface 24 of the socket 22. In this example, the curable substance 50 coats substantially the entire interior surface 24 of the socket 22, but as will be described later, other configurations of the curable substance 50 are possible. For example, the exterior surface 34 of the ball-stud 32 may also, or alternatively, be coated with the curable substance 50.

[0036] The curable substance 50 is curable such that, generally, before being cured, the curable substance 50 exists in a relatively fluid state, and the ball-stud 32 is reorientable within the socket 22. A curable substance may be understood as a material that undergoes a chemical or physical transformation to harden or solidify, thereby providing a bond between surfaces or elements to which it is applied. As the curable substance 50 is cured, the curable substance 50 adheres to the ball-stud 32 and the socket 22 and becomes relatively less fluid. Once the curable substance 50 is cured, the ball-stud 32 and socket 22 are fixed in position and are therefore no longer reorientable. A curing process of the curable substance 50, which causes the curable substance 50 to go from a relatively fluid state to a fixed state, can be initiated or accelerated by a variety of mechanisms, depending on the precise chemical composition of the curable substance 50. For example, application of heat may initiate the curing process. In other examples, application of a second substance such as a catalyst, or further substances, to the curable substance 50 may initiate the curing process. In yet further examples, the use of electromagnetic radiation, such as ultraviolet radiation, may initiate a curing process. Specific examples include resin-based substance, such as epoxy resins. Some epoxy resins can be cured by mixing with a curing agent and, in some examples, exposing the mixture to heat. Other specific examples include acrylic adhesive, which may be cured by means of UV light. In some examples, the curing is an irreversible reaction, wherein the cured state can be considered a relatively permanent state. In other examples, the curing is a reversible reaction, such that the substance in its cured form can be reverted to uncured form through a process or processes. In some examples where the curing is a reversible reaction, a first process may cure the curable substance, and a second, different process may revert the cured substance from its cured form to its uncured form, for example. In some examples, a thermoplastic material may be used as the curable substance. In some examples, for example where the curable substance is a thermoplastic material, the substance may be in a relatively fluid state when heated, and when cold exist in a hardened or solidified cured state.

[0037] The first portion 20 is attachable to the first aircraft structure 101. In this example, the first portion 20 comprises a plate 26, and fasteners 28 for securing the first portion 20 to the first aircraft structure 101. The plate 26 is connected to the socket 22 by a stem 25. The plate 26 distributes a support force from the first portion 20 across the first aircraft structure 101. The plate 26 may have a shape which conforms to a shape of the first aircraft structure 101, to attach the first portion thereby more securely to the first aircraft structure 28. The skilled person will appreciate that the manner in which the first portion 20 is attached to the first aircraft structure 101 is immaterial to the present disclosure. The second portion 30 is attachable to the second aircraft structure 102 in a similar manner, with corresponding plate 36 and fasteners 38 and a stem 35 connecting the socket 32 to the plate 36. Similarly, the precise nature of how the second portion 30 is attachable to the second aircraft structure 102 is similarly immaterial to the present disclosure.

[0038] In use, the first aircraft structure 101 is attached to the first portion 20 of the fitting 10 and the second aircraft structure 102 is attached to the second portion 30 of the fitting 10. The curable substance 50 is relatively fluid, and so the first aircraft structure 101 is reorientable relative to the second aircraft structure 102. With the first aircraft structure 101 in a desired orientation relative to the second aircraft structure 102, the curing process of the curable substance 50 can be initiated. This fixes the first aircraft structure 101 in position relative to the second aircraft structure 102. In Figure lb, the curable substance 60 has been cured and so the fitting 10 holds the second aircraft structure 102 at a fixed orientation relative to the first aircraft structure 101.

[0039] In other examples which can be readily explained in view of Figures la and lb, the curable substance 50 is not initially provided within the joint 10. Instead, the curable substance 50 may be introduced at a later point during the alignment process. For example, once a desired alignment between the first aircraft structure 101 and the second aircraft structure 102 is reached, the curable substance 50 may be added to the joint 10 by, for example, injection of the curable substance 50 into the joint 10. For example, the socket 22 may comprise a through-hole which allows the curable substance 50 to be applied to an external surface of the socket 22 and permeate from the external surface of the socket 22 to the internal surface of the socket 22 via the through-hole, in order to adhere the ball-stud 32 with the socket 22. Additionally or alternatively, the curable substance 50 could be applied into and / or around the opening 23 to permeate through to the internal surface of the socket 22.

[0040] Such a configuration, in which the curable substance 50 is introduced during or after an alignment process, may simplify or allow for a more accurate alignment process, for example, by removing mechanical impacts of the curable substance 50 on the alignment process, such as friction between the ball-stud and the socket, for example. This can allow use of curable substances 50 which are more viscous and might otherwise hinder the alignment process should they be provided at the joint prior to the alignment process, for example. Providing the curable substance 50 after an alignment process has taken place can allow for curable substances 50 with a stronger adhesive effect to be used, therefore.

[0041] Because the curable substance 50 is provided once a desired alignment between the first aircraft structure 101 and the second aircraft structure 102 is reached, the curable substance 50 could be cured upon exposure to air, for example, which could provide a convenient method of initiating the curing process without requiring additional equipment.

[0042] It will be appreciated that, in general, the fitting 10 can be considered to have a first state in which relative movement of the first portion relative to the second portion is permitted, and a second state in which the first portion is fixed relative to the second portion. Curing the curable substance 50 transitions the fitting 10 from the first state to the second state.

[0043] Figures 2a and 2b illustrate the fitting 10 used in the installation of a landing gear leg fairing to a landing gear 500, in which the fitting 10 is contemplated to be particularly useful for reasons described shortly. In the example of Figures 2a and 2b, the first aircraft structure 101 is a landing gear leg fairing and the second aircraft structure 102 is a landing gear leg. The landing gear leg fairing 101 is attached to the landing gear leg 102 by a plurality of fittings 10 according to the present invention.

[0044] Figure 2a illustrates the landing gear 500 in a stowed configuration, in which the landing gear leg 102 is retained within the aircraft, and Figure 2b illustrates the landing gear 500 in a deployed position in which the landing gear leg 102 extends below the aircraft, such as that used for take-off or landing, for example.

[0045] In the stowed configuration of Figure 2a, it is preferrable for the landing gear leg fairing 101 to be flush relative to a fuselage skin 120 of the aircraft and a main door 122 of the landing gear 500 to help ensure good aerodynamic performance. However, in deploying the landing gear 500 to arrive at the deployed configuration of Figure 2b, the landing gear leg fairing must move relative to the fuselage skin 120 and the main door 122, and so it will be appreciated that correct positioning of and adequate spacing between the landing gear leg fairing 101, fuselage skin 120 and main door 122 is needed in order to permit movement between the deployed configuration and stowed configuration.

[0046] As described previously, the landing gear leg fairing 101 is attached to the landing gear leg 102 by a plurality of fittings 10 according to the present invention.

[0047] With each of the plurality of fittings 10 in the first state, the landing gear leg fairing 101 can be aligned relative to the landing gear leg 102. This may involve moving the landing gear 500 between stowed and deployed configurations to check the positioning and spacing of the landing gear leg fairing 101 with the fuselage skin 120 and main door 122. The plurality of fittings 10 may be arranged such that each performs a particular alignment function. For example, a first fitting of the plurality of fittings 10 may be primarily responsible for alignment of the landing gear leg fairing 101 with the fuselage skin 120, whereas a second fitting of the plurality of fittings 10 may be primarily responsible for alignment of the landing gear leg fairing 101 with the main door 122, for example. That is, the second fitting 10 may be located more closely to main door 122 in the stowed position and so the arrangement of the second fitting can be considered to be more important in ensuring positioning and alignment of the landing gear leg fairing 101 with the main door 122, for example.

[0048] Whilst the plurality of fittings 10 are schematically portrayed as identical balljoints, the plurality of fittings 10 can be different to each other and need not have the same configuration as each other.

[0049] Figures 3 and 4 illustrates methods of installing a first aircraft structure to a second aircraft structure using the fitting according to the present invention.

[0050] At item S101 of Figure 3, the first aircraft structure is connected to the second aircraft structure by a fitting according to the present invention. As described previously, attachment of the fitting to the first and second aircraft structure can be by known methods of attachment such as fasteners or adhesives. In some examples, the first portion of the fitting is attached to the first aircraft structure independently from the second portion of the fitting being attached to the second aircraft structure, and the first portion is then combined with the second portion in order to form the joint and connect the first aircraft structure to the second aircraft structure, for example. In other examples, the first portion is attached to the second portion via the joint, and the first portion is attached to the first aircraft structure. The second portion, already attached to the first aircraft structure via the joint, is then attached to the second aircraft structure. In some examples, prior to the first portion being connected to the second portion, the curable substance is provided to at least one of the portions.

[0051] At item SI03 of Figure 3, the first aircraft structure is then positioned relative to the second aircraft structure. Such positioning could be performed solely by human operator, or by human operator in conjunction with robotic assistance, for example. This step may include performing checks such as measuring the spacing or alignment between the first aircraft structure and the second aircraft structure, or between at least one of the first and second aircraft structures and neighbouring aircraft structures, for example. Assessing the correct spacing or alignment may involve ensuring a value, such as an alignment angle, or separation distance, does not exceed a maximum threshold value, or is above a minimum value, or lies within a specific range, for example. Positioning the first aircraft structure relative to the second aircraft structure or the neighbouring aircraft structures may be an iterative process, for example, which utilises multiple stages of alignment before a preferred alignment is reached.

[0052] At item S105, the curable substance is cured once the first aircraft structure is in a desired alignment relative to the second aircraft structure. As described previously, the curing process can be by initiated and / or mediated by heating, radiation, or chemical means, for example. Curing the curable substance fixes the first aircraft structure relative to the second aircraft structure. In examples where the curable substance is cured particularly quickly, such as on the order of minutes, for example, a human operator may be able to hold the first aircraft structure in alignment with the second aircraft structure, or vice versa, as the curable substance cures, thereby negating the need for structural scaffolding which might perform a similar task, for example.

[0053] The method of Figure 4 is similar to that of Figure 3, but the joint does not need to comprise a curable substance prior to alignment. Instead, the curable substance is provided at a subsequent item, as described hereafter.

[0054] Items S201 and S203 proceed similarly to items SI01 and SI03, respectively, with the first aircraft structure being connected to the second aircraft structure and then the first aircraft structure being positioned relative to the second aircraft structure.

[0055] At item S205, a curable substance at the joint is provided. This can be applied locally to the joint by use of a syringe or similar tool, for example. Use of a distributor tool, such as a brush, may help ensure that the curable substance coats a sufficient portion of the joint in order to enable suitable adhesion between the two portions of the fitting such that their relative movement is prevented.

[0056] Item S207 proceeds similarly to item SI05, as the curable substance is cured to fix the first aircraft structure relative to the second aircraft structure.

[0057] The fitting 10 may be used in a temporary manner, or in conjunction with other fasteners, and the example methods of Figures 3 and 4 may instead form a partial stage of an installation process of a first aircraft structure, rather than represent an entire installation process.

[0058] For example, once the first aircraft structure is aligned with the second aircraft structure and the curable substance of the fitting 10 cured, thereby fixing the first aircraft structure relative to the second aircraft structure, the first aircraft structure can be held more securely in alignment with the second aircraft structure than compared with, for example, an operator or a scaffolding structure holding the first aircraft structure in place without the presence of the fitting 10. This can allow further components to be introduced to the first or second aircraft structure with a decreased risk of misaligning the first aircraft structure relative to the second aircraft structure. For example, further fasteners can be provided to increase strength of the connection between the first aircraft structure and the second aircraft structure, wherein without the fitting 10 installation of these further fasteners may risk misaligning the first aircraft structure relative to the second aircraft structure. For example, a screwing or torquing action to secure a fastener may risk misaligning the aircraft structures to which the fastener is attached.

[0059] In further examples, the fitting 10 itself is reinforced with additional components to strengthen the position already established by the cured curable substance. The curable substance is thereby used to establish an intermediate strength sufficient for installation purposes, but the fitting 10 is further enhanced after installation to improve strength sufficient for airworthiness, for example.

[0060] In further examples, the fitting 10 may subsequently be removed from the aircraft structure after provision of permanent fasteners, for example, but nevertheless the fitting 10 can be of benefit to the installation of the aircraft structure.

[0061] Figure 5 illustrates an aircraft 1000 according to an embodiment of the present invention. The aircraft 1000 comprises the fitting 10 and landing gear 500 described previously. The aircraft 1000 can be more quickly manufactured, due to the improved installation process described herein. Similarly, should maintenance be required, such as a replacement landing gear leg fairing be provided, the speed of such maintenance can be improved which can reduce downtime of the aircraft 1000, for example.

[0062] The above embodiments are to be understood as an illustrative example of the invention. Further embodiments of the invention are envisaged:

[0063] The example of Figure lisa ball-joint. However, it will be appreciated that other joints which permit relative movement of two connected structure may be used. For example, a pin-joint, or hinge joint, which permits movement in one degree of freedom, may be used. A curable substance provided within the joint or applied to the joint once an alignment has been reached could then be cured to fix the joint in position. This can be useful where movement in only one degree of freedom is desired, for example.

[0064] In the example of Figure 1, the ball-joint is described as providing movement in three degrees of freedom corresponding to pitch, yaw, and roll of the first aircraft structure relative to the second aircraft structure. However, it will be appreciated that if the socket is sufficiently large relative to the ball-stud then additional movement may be possible, as the ball-stud can undergo x, y and z translations within the socket. The ball-joint can thereby allow six degrees-of-freedom, which may allow for fine adjustment of the first aircraft structure relative to the second aircraft structure, for example.

[0065] It will be understood that apparatus features of the present invention, such as those described in view of Figures la, lb, 2a, 2b can be incorporated into the methods of the present invention, such as those illustrated by Figures 3 and 4. Similarly, features described during explanation of the methods of the present invention can be incorporated into apparatus according to the present invention.

[0066] It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

[0067] 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 fitting for alignment and attachment of a first aircraft structure to a second aircraft structure, the fitting comprisinga first portion attachable to the first aircraft structure,a second portion attachable to the second aircraft structure, a joint connecting the first portion to the second portion, and a curable substance configured to be provided in at least a portion of the joint; wherein the joint and curable substance are configured such that the fitting is arrangeable ina first state wherein the joint allows the first portion to be moved relative to the second portion such that when the first portion is attached to the first aircraft structure and the second portion is attached to the second aircraft structure, the first aircraft structure can be aligned relative to the second aircraft structure, anda second state in which the curable substance is cured such that movement of the first portion relative to the second portion is prevented.

2. The fitting of claim 1, wherein the joint is a ball-joint configured to, in the first state, allow for relative movement of the first portion and the second portion in at least three degrees of freedom, wherein the first portion comprises a socket of the ball-joint and the second portion comprises a ball-stud of the ball joint, and wherein the ball-stud is arrangeable within the socket.

3. The fitting of claim 2, wherein the socket and the ball-stud are configured to, in the first state, cooperate to permit relative movement of the first portion and the second portion in six degrees of freedom.

4. The fitting of claim 2 or 3, wherein the curable substance is configured to coat at least some of a surface of the socket and at least some of a surface of the ball-stud.

5. The fitting of claim 4, wherein at least one of the ball-stud and the socket comprises a textured surface configured to be in contact with the curable substance.

6. The fitting of any previous claim, wherein the curable substance is curable by an external heat source.

7. The fitting of any previous claim, wherein the curable substance is configured to cure within a predeterminable time period.

8. The fitting of any previous claim, wherein the at least a portion of the joint is configured to receive the curable substance from an external source after the first portion is aligned relative to the second portion.

9. An aircraft structure comprising the fitting of any previous claim, the aircraft structure being the first aircraft structure or the second aircraft structure.

10. The aircraft structure of claim 9, comprising a plurality of fittings according to any previous claim.

11. The aircraft structure of claim 9 or 10, wherein the aircraft structure is a fairing.

12. The aircraft structure of claim 11, wherein the fairing is a landing gear leg fairing.

13. An aircraft comprising the fitting or the aircraft structure of any previous claim.

14. A method of installing a first aircraft structure, the first aircraft structure beingattached to a second aircraft structure by a movable joint allowing movement of the first aircraft structure relative to the second aircraft structure in at least a first degree of freedom, the movable joint comprising a curable substance configured to, when cured, prevent movement of the joint, the method comprising:positioning the first aircraft structure relative to the second aircraft structure in the at least first degree of freedom; andcuring the curable substance such that the first aircraft structure is fixed relative to the second aircraft structure.

15. The method of claim 14, wherein curing the curable substance comprises applying heat to the curable substance16. The method of claim 14 or 15 wherein the first aircraft structure is a landing gear leg fairing, and the second aircraft structure is a landing gear leg, and positioning the first aircraft structure relative to the second aircraft structure in the at least first degree of freedom comprises aligning the landing gear leg fairing with an external surface of the aircraft when the landing gear leg is in a retracted position.

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