Aircraft landing gear assembly

Abstract

An aircraft landing gear assembly (10) includes structural members (12, 14) coupled via a coupling, the structural members including a bearing (22). The bearing includes a body (24) defining a first bearing surface (B1) disposed to contact a first opposing face of the coupling. The first bearing surface is formed by a first tubular layer (23) of a fiber-reinforced polymer of a first type, having an axis and containing synthetic fibers of a first type, and the synthetic fibers of the first type are wound around and along the axis of the bearing. The bearing body further comprises a second tubular layer (30) of a second type of fiber reinforced polymer containing a second type of synthetic fibers wound around and along the axis of the bearing.

Description

[0001] This application is a divisional application of the patent application for invention entitled "Airplane landing gear assembly" with applicant being Safran Landing Systems UK Limited, filed on 31 March 2017, application number 201710208345.X. TECHNICAL FIELD

[0002] The present invention relates to an airplane landing gear assembly and an airplane comprising one or more such airplane landing gears, and also to a method of forming a bearing of an airplane landing gear assembly and a method of forming or maintaining an airplane landing gear assembly. BACKGROUND

[0003] An airplane landing gear assembly can comprise structural members coupled via a coupling or joint comprising one or more bearings. For example, the members can be movably coupled via a pin joint. The pin joint can generally comprise a plurality of bearings, each located between the pin and one of the structural members.

[0004] An airplane landing gear joint can be designed to withstand static pressures in excess of 400 MPa. The static pressure arises due to the first and second structural members acting on the joint while the airplane is on the ground; for example, during taxiing, the lug of a side stay link acts on a common pin joint, wherein the pin joint is subjected to multi-directional loading.

[0005] An airplane landing gear assembly joint can also be designed to withstand dynamic pressures of around 150 MPa, which arise due to movement between the structural members; for example, during articulation of the landing gear between deployed and stowed conditions.

[0006] The airplane landing gear assembly joint is typically greased periodically to maintain a low coefficient of friction at the bearing surfaces, to control the amount of wear and to remove contaminants. An integral grease channel can be provided within one or more of the structural members to enable grease to be introduced to the bearing surfaces during a service operation.

[0007] However, the inventors have recognised that a grease channel can result in increased complexity of the joint. The grease channel can also result in increased stress to define a region of weakness in the pin joint. Furthermore, a service engineer can neglect the joint during servicing, resulting in increased friction and wear. Different types of grease can also be introduced to the joint, resulting in a loss of lubrication performance. The grease can also migrate under sustained loading, resulting in regions where lubricant is lacking.

[0008] The inventors have also recognised that the mass of known landing gear assemblies can be reduced. SUMMARY

[0009] According to a first aspect of the application, there is provided an aircraft landing gear assembly comprising a first structural member coupled to a second structural member via a mechanical coupling, the mechanical coupling comprising a bearing comprising a tubular body defining a first bearing surface arranged to contact a first opposing surface of the coupling, and the first bearing surface being defined by a first tubular layer of a first type of fibre reinforced polymer, the first tubular layer having an axis and containing a first type of synthetic fibre wound around and along the axis of the bearing, the bearing body further comprising a second tubular layer of a second type of fibre reinforced polymer, the second tubular layer containing a second type of synthetic fibre wound around and along the axis of the bearing, wherein one of the first and second fibre reinforced polymers has a greater compressive strength characteristic than the other, and / or wherein one of the first and second fibre reinforced polymers has a greater self-lubricating characteristic than the other. Such an arrangement can be such that the fibre reinforced polymer having the greatest compressive strength characteristic has the lowest self-lubricating characteristic compared to the other.

[0010] Although the use of polymers for self-lubricating bearings is known, the polymer bearings known to the inventors are in the form of sintered powder materials and lubrication is provided by the use of a thin layer of PTFE, for example less than 1 mm. Such bearings are designed for use in low load joints arranged to withstand static pressures of around 120 MPa and with limited rotation. Thus, these known bearings are not suitable for use in aircraft landing gear assemblies, where the bearings can experience static pressures in excess of 400 MPa, taking into account impact loads. The inventors have surprisingly found that the polymer bearings described herein can withstand static pressures in excess of 600 MPa, and in some cases in excess of 750 MPa when used as a tubular bearing in a landing gear assembly. The landing gear assemblies according to embodiments of the application can result in a significant weight reduction compared to known landing gear assemblies. The self-lubricating properties of the first bearing layer also enable the omission of grease channels. The inventors have also found that the composite filament wound layer bearings described herein are surprisingly resistant to the working environment within a landing gear coupling joint. The bearings can suitably stretch to flex with the structural members, which can reduce internal stresses within the coupling compared to at least some known bearings. The bearings also have good misalignment resistance and higher fracture resistance compared to at least some known bearings.

[0011] The second type of polymer can have a greater compressive strength characteristic than the first type of polymer, and / or the first type of polymer can have a greater self-lubricating characteristic than the second type of polymer. Such an arrangement can be particularly useful in an aircraft landing gear pin joint, where the bearing takes the form of a bushing statically fitted into a lug hole and arranged to dynamically carry a conventional pivot pin within a bore of the bearing.

[0012] The first type of polymer can include an epoxy, resin or thermoset material and can house dry lubricant particles that are exposed as the bearing wears. The first type of synthetic fiber can include continuous fibers such as carbon, aramid, glass, PTFE, polyester or combinations thereof.

[0013] The second type of polymer can include an epoxy, resin or thermoset material. Preferably, the first and second types of polymer are matched for consolidation purposes. The first type of synthetic fiber can include continuous fibers such as carbon, aramid, glass, PTFE, polyester or combinations thereof.

[0014] Preferably, the relatively self-lubricating layer of the bearing includes dry lubricant particles such as graphite contained in an epoxy, and a continuous woven mixture of PTFE fibers and carbon fibers. Preferably, the relatively high strength layer includes glass fibers contained in an epoxy. This combination has been found to be particularly effective in handling static pressures in excess of 600 MPa and for landing gear linkages or joints.

[0015] The bearing body can define a second bearing surface disposed to contact a second opposing face of the linkage, the body separating the first bearing surface from the second bearing surface such that a thickness of the tubular bearing body is defined between the first bearing surface and the second bearing surface, wherein the thickness of the first layer is less than one quarter of the overall thickness of the tubular bearing body.

[0016] The bearing body can include a third tubular layer of a third type of fiber reinforced polymer containing a third type of synthetic fiber wound around the second tube. The second type of polymer can have a greater compressive strength characteristic than the third type of polymer, and the third type of polymer can have a greater self-lubricating characteristic than the second type of polymer. The third type can be the same as the first type in both cases.

[0017] The first tube can be solid to define a solid pin-like bearing. In these embodiments, the inner tube can be formed of a relatively strong fiber reinforced polymer, while the outer tube can be formed of a relatively self-lubricating fiber reinforced polymer.

[0018] The linkage can be disposed to movably couple the first structural member to the second structural member such that the first opposing face of the linkage moves relative to the first bearing surface.

[0019] The first bearing surface and the first opposing face can each be circular in cross-section such that the linkage is disposed to allow the first structural member to rotate relative to the second structural member about an axis of the bearing.

[0020] The coupling can comprise a pin mounted within a bore formed through the first and second structural members to define a pin joint, the bearing being disposed between the pin (on one hand) and one or more of the first and second components (on the other hand), the pin defining a first opposing face of the coupling.

[0021] The bearing can comprise a radial flange at one end, the radial flange comprising a radially extending layer of fibre-reinforced polymer having an axis and containing synthetic fibres wound radially about the axis of the bearing.

[0022] The landing gear assembly can comprise a plurality of bearings as defined above, each bearing having a respective bearing surface in contact with a respective opposing face of the coupling.

[0023] According to a second aspect of the application, there is provided an aircraft comprising one or more aircraft landing gear assemblies according to the first aspect.

[0024] According to a third aspect of the application, there is provided a method of forming a bearing for use in an aircraft landing gear assembly, the method comprising:

[0025] forming a first tubular layer of a first type of fibre-reinforced polymer having an axis and containing a first type of synthetic fibre wound about and along the axis of the bearing;

[0026] forming a second tubular layer of a second type of fibre-reinforced polymer containing a second type of synthetic fibre wound about and along an outer surface of the first tubular layer; and

[0027] causing the first and second layers to cure to form a consolidated tubular body.

[0028] Optional features of the first aspect apply in a similar manner to the method of the third aspect; for example, one of the first and second fibre-reinforced polymers can have a greater compressive strength property than the other, and / or one of the first and second fibre-reinforced polymers can have a greater self-lubricating property than the other.

[0029] The tubular layers of fibre-reinforced polymer can each be formed in a conventional manner; for example, a filament winding process in which a bundle of fibres pre-impregnated with uncured polymer is wound about a tool such as a mandrel or a pre-wound inner layer of fibre-reinforced polymer.

[0030] The method can comprise:

[0031] forming a radial flange on the bearing by machining a portion of the second tubular layer to leave a radial flange; and

[0032] Optionally a layer of self-lubricating material is bonded to the axial surface of the flange.

[0033] The method can include forming a radial flange and bonding the radial flange to the axial end face of the tubular body, the radial flange being larger in cross-section than the tubular body.

[0034] According to a fourth aspect of the application, there is provided a method of forming or maintaining an aircraft landing gear assembly, the landing gear assembly comprising a first structural member coupled to a second structural member via a mechanical coupling, the mechanical coupling comprising a bearing, the bearing defining a first bearing surface arranged to contact a first opposing surface of the coupling, the method comprising:

[0035] Optionally removing a worn bearing from the mechanical coupling; and

[0036] Fitting a bearing to the coupling, the bearing defining a first bearing surface arranged to contact a first opposing surface of the coupling, and the first bearing surface being defined by a first tubular layer of a first type of fibre-reinforced polymer, the first tubular layer having an axis and containing a first type of synthetic fibre wound around and along the axis of the bearing, the bearing further comprising a second tubular layer of a second type of fibre-reinforced polymer, the second tubular layer containing a second type of synthetic fibre wound around and along the axis of the bearing, wherein one of the first and second fibre-reinforced polymers has a greater compressive strength characteristic than the other, and / or wherein one of the first and second fibre-reinforced polymers has a greater self-lubricating characteristic than the other. BRIEF DESCRIPTION OF DRAWINGS

[0037] Preferred embodiments of the application will now be described with reference to the accompanying drawings, in which:

[0038] Figure 1 is a partial cross-sectional view of a prior art landing gear assembly;

[0039] Figure 2 is a partial cross-sectional view of a landing gear assembly according to an embodiment of the application;

[0040] Figure 3 is a cross-sectional view of the bearing of Figure 2

[0041] Figure 4a and 4b is a cross-sectional view of a method of assembling a bearing of a landing gear assembly according to another embodiment of the application;

[0042] Figure 5a and 5b is a cross-sectional view of the method of assembling according to another embodiment of the application. DETAILED DESCRIPTION ​

[0043] Figure 1 A portion of a conventional landing gear assembly 100 is shown in which a first structural member 12 is pivotally coupled to a second structural member 14 via a pin joint. The first and second structural members 12, 14 terminate in lugs having pairs of arms 12a, 12b, 14a, 14b that define a space therebetween that is sized to receive first and second arms 14a, 14b of a lug defined at an end of the second structural member 14. Each arm 12a, 12b, 14a, 14b includes a hole such that when the lugs are aligned, a pin 16 can be received by each hole to pivotally couple the first structural member 12 to the second structural member 14. The first and second structural members 12, 14 can be, for example, main fitting attachment lugs through which a main fitting is pivotally coupled to a fuselage, a side stay link, a torque link, a lock link, a shortening link, a bogie pivot pin, an actuator attachment, and the like.

[0044] Each lug hole is provided with a plain bearing 18 having a body 18a that extends generally parallel with respect to a longitudinal axis A of the pin 16 to lie between the lug and the pin 16 to support the pin 16 in use. The axis A can also describe an axis of the bearing 18. Thus, the body 18a of each bearing 18 defines a bearing surface that cooperates with a bearing opposite surface of the pin 16 in use. The length of each bearing body 18a can be defined by the width of the lug arms 12a, 12b, 14a, 14b at the lug hole; an example length of a typical body 18a is between 20 mm and 100 mm.

[0045] Each bearing 18 also has a radial flange 18b that resists lateral loading to limit axial travel of the bearing 18 through the lug hole and by which the bearing 18 can be attached to the lug.

[0046] The pin joint 16 is designed to withstand operational loads due to static pressures across each bearing body 18a of at least 300 MPa, and in some cases pressures in excess of about 400 MPa. The joint can also be designed to withstand dynamic pressures of about 150 MPa as the landing gear members move between conditions. As such, the bearings 18 are generally formed of aluminum bronze or stainless steel.

[0047] Grease channels 20 are provided in at least some of the structural members 14a, 14b to enable grease lubricant or the like to be introduced to the bearing surfaces during servicing operations. However, the inventors have recognised that the grease channels 20 can result in increased joint complexity. The grease channels 20 can also result in increased stress to define a region of weakness in the pin joint. Furthermore, a servicing engineer can neglect the joint during servicing, resulting in increased friction and wear. Different types of grease can also be introduced to the joint, resulting in a loss of lubrication performance.

[0048] Figure 2 A portion of a landing gear assembly 10 according to an embodiment of the application is shown. The landing gear assembly 10 is similar to Figure 1 the landing gear assembly 100 of

[0049] With additional reference to Figure 3 the tubular bearings 22 each have a generally cylindrical tubular body 24 and an optional radial flange 26. In other embodiments, the tubular body 24 can have a different cross-sectional profile; for example, a rectangular profile.

[0050] The internal bore defining the tubular body 24 defines a first bearing surface Bl that is arranged in use to support Figure 2 the pin 16. The external cylindrical surface of the tubular body 24 defines a second bearing surface B2 that is arranged in use to statically engage with the lug bore surface such that the bearing 22 is retained within the lug bore, for example by means of an interference fit. The bearing surfaces Bl and B2 are parallel; however, in other embodiments, the bearing can comprise non-parallel sides, for example a tapered or spherical bearing. The distance between the bearing surfaces Bl, B2 defines a thickness TB of the tubular body 24. The bearing thickness TB can be, for example, between 4mm and 25mm.

[0051] The tubular body 24 can be formed from concentric pairs of fibre-reinforced polymer tubes 28, 30. The inner tube 28 is formed from a tubular layer of a first type of fibre-reinforced polymer having an axis A and containing a first type of synthetic fibre wound around and along the axis A of the bearing 22. The outer tube 30 is formed from a tubular layer of a second type of fibre-reinforced polymer containing a second type of synthetic fibre wound around the first tube 28. The second type of polymer can have a greater compressive strength characteristic than the first type of polymer, and the first type of polymer can have a greater self-lubricating property than the second type of polymer. The skilled person will be able to measure the compressive strength and lubricating properties of a given bearing by routine experimentation. The inner tube 28 can have, for example, a uniform thickness of between 1 and 3mm, while the outer tube has, for example, a uniform thickness of up to 20mm.

[0052] The first type of polymer can comprise an epoxy resin, a resin or a thermoset material, and can contain dry lubricant particles that are held within the polymer and released as the bearing wears. The first type of synthetic fibre can comprise continuous fibres, for example carbon, aramid, glass, PTFE, polyester or combinations thereof.

[0053] The second type of polymer can include an epoxy, a resin, or a thermoset. Preferably, the first and second types of polymer are matched for consolidation purposes. The first type of synthetic fiber can include continuous fibers such as carbon, aramid, glass, PTFE, polyester, or combinations thereof.

[0054] The fibers within each layer 28, 30 can be coated with uncured polymer in a conventional manner and wound around the axis A of the bearing, for example, using a mandrel, extending in a helical manner axially along the tubular length of the bearing 22. The number of axially oriented layers disposed in this manner can determine the thickness of the bearing layer. The fibers can be woven at an angle between 30 and 75 degrees relative to the longitudinal axis A, and in some examples at 45 degrees. Once two or more layers of tubing 28, 30 have been formed, the bearing body can be cured in a conventional manner, for example, with heat treatment.

[0055] Preferably, the relatively self-lubricating layer includes a continuous weave of PTFE fibers and carbon fibers with epoxy-containing dry lubricant particles such as graphite, and preferably the relatively higher strength layer includes glass fibers with epoxy, as this combination has been found to be particularly effective in handling static pressures in excess of 600 MPa and providing self-lubrication for the joint.

[0056] In one particular example, the fiber-reinforced polymer material of the body 24 can be a material such as GAR-MAX®, preferably high-strength GAR-MAX® produced by GGB Bearing Technology. Alternatively, Fibre-Lube (TM) produced by Daemar Inc. can be used.

[0057] The optional radial flange 26 has a first axial surface defining a third bearing surface B3 and a second axial surface defining a fourth bearing surface B4. The bearing surfaces B3 and B4 are parallel in this example, but need not be. As shown in FIG. 1, the first layer 28 is formed by winding an axial layer 28a of fibers around the mandrel 27. The fibers can be coated with uncured polymer in a conventional manner and wound around the mandrel 27, extending in a helical manner axially along the tubular length of the mandrel 27. The number of axially oriented layers 28a disposed in this manner can determine the thickness of the first layer 28. Figure 4a and 4b Once the second layer 30 has been wound around the first layer 28 and cured on the first layer, the flange 26 can be formed by machining the cylindrical portion P of the second layer 30 to leave the radially extending flange 26a. An axial layer 32 of a self-lubricating material such as PTFE bearing tape can be applied to the outer surface of the flange 26a to define the fourth bearing surface B4. Alternatively, as shown in FIG. 2, the flange 26 can be formed by machining the cylindrical portion P of the second layer 30 to leave the radially extending flange 26a, and then applying an axial layer 32 of a self-lubricating material such as PTFE bearing tape to the inner surface of the flange 26a to define the third bearing surface B3. Figure 5a and 5bAs shown in FIG. 1, the flange 26 can be formed as a single piece 34 of any suitable material that can be formed in the shape of a washer and chemically bonded at 36 to the body 24 to form the bearing. Further, the flange piece 34 can be provided with an axial layer 32 of self-lubricating material to define the fourth bearing surface B4. In all embodiments, the flange can be provided such that a space or chamber is created where the bearing surfaces B1 and B4 would otherwise meet, thereby preventing direct contact between the second layer 30 and the opposing face of the dynamic link.

[0058] The bearing according to embodiments of the application can include a third tube (not shown) wrapped around the second tube to define the second bearing surface, the third tube formed of a tubular layer of a third type of fiber-reinforced polymer containing synthetic fibers of a third type wrapped around the second tube 30. The second type of polymer can have a greater compressive strength characteristic than the third type of polymer, and the third type of polymer can have a greater self-lubricating characteristic than the second type of polymer. The third type can be the same as the first type in both cases. Further, in any embodiment, the innermost tube can be solid to define a pin-like bearing. In these embodiments, it can be that the inner tube will be formed of a relatively strong fiber-reinforced polymer, while the outer tube will be formed of a relatively self-lubricating fiber-reinforced polymer.

[0059] For example, it will be apparent from Figure 2 It will be apparent from the foregoing that a landing gear assembly according to embodiments of the application can have a plurality of bearings as defined herein, each bearing having one or more respective bearing surfaces in dynamic or static contact with a respective opposing face of a link member. The opposing face of the link member can be provided by a surface of a structural element, pin, or other link member, or by a bearing or bearing component such as a race of a roller bearing.

[0060] An aircraft landing gear assembly according to embodiments of the application including self-lubricating polymer bearings as described above allows for easier design and analysis of structural members and can significantly reduce the weight of an aircraft landing gear assembly. These bearings can be applied to new landing gears, and can also be retrofitted to in-service landing gears during maintenance, repair, and overhaul.

[0061] It should be noted that the above-mentioned embodiments illustrate rather than limit the application, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the application as defined by the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word 'comprising' does not exclude the presence of elements or steps other than those listed in any claim or specification. The word 'a' or 'an' preceding an element does not exclude the presence of a plurality of such elements. The application can be implemented by means of both hardware and software, and any combination thereof. In a device claim enumerating several means, the enumerated means can be considered selective of the specified means alone et vice versa; listing a combination of means in a device claim is not to be interpreted as requiring that all combinations are to be implemented.

Claims

1. An aircraft landing gear assembly comprising a first structural member (12) coupled to a second structural member (14) via a mechanical coupling (16), the mechanical coupling (16) comprising a bearing (22), wherein, The bearing (22) defines a first bearing surface (B1) arranged to contact a first opposing surface of the coupling, the first bearing surface (B1) being defined by a first tubular layer (28) of a first type of fibre-reinforced polymer, the first tubular layer having an axis (A) and containing a first type of synthetic fibre wound around and along the axis (A) of the first tubular layer, the bearing further comprising a second tubular layer (30) of a second type of fibre-reinforced polymer containing a second type of synthetic fibre wound around and along the axis (A) of the first tubular layer, characterised in that one of the first and second fibre-reinforced polymers has a greater compressive load capacity than the other, and the other of the first and second fibre-reinforced polymers contains dry lubricant particles to improve its self-lubricating properties compared to the other.

2. The aircraft landing gear assembly of Claim 1, wherein, The first type of polymer comprises an epoxy resin, resin or thermoset material, and / or the second type of polymer comprises an epoxy resin, resin or thermoset material.

3. An aircraft landing gear assembly as claimed in any preceding claim, characterised in that, The first type of synthetic fibre and the second type of synthetic fibre are continuous fibres.

4. An aircraft landing gear assembly as claimed in any preceding claim, characterised in that, The bearing has a second bearing surface (B2) arranged to contact a second opposing surface of the coupling, the body separating the first bearing surface from the second bearing surface such that a thickness (TB) of the tubular body (24) of the bearing is defined between the first bearing surface (B1) and the second bearing surface (B2), wherein the thickness of the first layer is less than ¼ of the overall thickness of the bearing body.

5. An aircraft landing gear assembly as claimed in any preceding claim, characterised in that, The coupling is arranged to movably couple the first structural member (12) to the second structural member (14) such that the first opposing surface of the coupling moves relative to the first bearing surface (B1).

6. The aircraft landing gear assembly of claim 5, wherein, The first bearing surface (B1) and the first opposing surface are each circular in cross-section such that the coupling is arranged to allow the first structural member (12) to rotate relative to the second structural member (14) about the axis of the first tubular layer.

7. An aircraft landing gear assembly as claimed in claim 5 or claim 6, wherein, The coupling comprises a pin mounted within a bore formed through the first and second structural members to define a pin joint, the bearing being disposed between the pin and one or more of the first and second components on one side and the other, the pin defining the first opposing surface of the coupling.

8. An aircraft landing gear assembly as claimed in any preceding claim, characterised in that, The bearing comprises a radial flange (26) at one end.

9. An aircraft landing gear assembly as claimed in any preceding claim, characterised in that, A plurality of bearings as claimed in any preceding claim, each bearing having a respective bearing surface arranged to contact a respective opposing surface of the coupling.

10. An aircraft comprising one or more aircraft landing gear assemblies as claimed in any preceding claim.

11. A method of forming a bearing for an aircraft landing gear assembly, the method comprising: forming a first tubular layer (28) of a first type of fibre reinforced polymer, the first tubular layer having an axis and containing a first type of synthetic fibre, and the first type of synthetic fibre being wound around and along the axis of the first tubular layer; forming a second tubular layer (30) of a second type of fibre reinforced polymer, the second tubular layer containing a second type of synthetic fibre, and the second type of synthetic fibre being wound around and along the outer surface of the first tubular layer; and and causing the first and second layers to cure to form a consolidated tubular body, characterised in that one of the first and second fibre reinforced polymers has a greater compressive strength characteristic than the other, and in that the other of the first and second fibre reinforced polymers contains dry lubricant particles to provide it with a greater self-lubricating characteristic than the other.

12. The method of claim 11, wherein, comprising: forming a radial flange on the bearing by machining to remove a portion (P) of the second tubular layer to leave a radial flange; and optionally bonding a layer (32) of self-lubricating material to the axial surface of the flange.

13. The method of claim 11, wherein, comprising forming a radial flange (26) and bonding the radial flange to an axial end face of the tubular body.

14. A method of forming or maintaining an aircraft landing gear assembly, the landing gear assembly comprising a first structural member (12) coupled to a second structural member (14) via a mechanical coupling (16), the mechanical coupling comprising a bearing, wherein the bearing defines a first bearing surface (Bl) arranged to contact a first opposing surface of the coupling, the method comprising: furnishing a bearing to the coupling, the bearing defining a first bearing surface arranged to contact a first opposing surface of the coupling, the first bearing surface being defined by a first tubular layer (28) of a first type of fibre reinforced polymer, the first tubular layer having an axis (A) and containing a first type of synthetic fibre, the first type of synthetic fibre being wound around and along the axis (A) of the first tubular layer, the bearing further comprising a second tubular layer (30) of a second type of fibre reinforced polymer, the second tubular layer containing a second type of synthetic fibre wound around and along the axis (A) of the first tubular layer, characterised in that one of the first and second fibre reinforced polymers has a greater compressive strength characteristic than the other, and in that the other of the first and second fibre reinforced polymers contains dry lubricant particles to provide it with a greater self-lubricating characteristic than the other.

15. The method of claim 14, wherein, the method being a method of maintaining an aircraft landing gear, the method comprising the step of: removing a worn bearing from the mechanical coupling prior to the step of furnishing the bearing to the coupling.

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