MODULAR LANDING GEAR

Abstract

A modular aircraft landing gear assembly is disclosed having a modular landing gear bracket, connectable to an aircraft via a hinge portion, a lever for carrying a wheel, and a linkage assembly for transmitting ground loads via a spring and/or a shock absorber. The bracket comprises structure which redundant when used on an aircraft of a first type but which is necessary for use of the same type of bracket on a different type of aircraft. The modular landing gear assembly may thus provide a design platform from which landing gear assemblies can be readily designed and manufactured for use on different types of aircraft with faster and/or easier redesign and/or recertification of the aircraft landing gear assembly for such subsequently designed types of aircraft.

Description

BACKGROUND OF THE INVENTION

The present disclosure relates to an aircraft landing gear assembly and a method of manufacturing a landing gear assembly. More particularly, but not exclusively, this invention concerns a modular aircraft landing gear assembly.

A conventional landing gear assembly comprises a primary landing gear leg having a hydraulic shock absorber (an oleo strut) which, when deployed, extends vertically, or close to vertical, from the aircraft body or wing to the wheels on the ground. The majority of the vertical loads are transmitted from the wheels into the aircraft via the leg. The single leg typically carries two, four or six wheels. A landing gear assembly for one type of aircraft is typically unsuitable for use with an aircraft having a significantly higher maximum take-off weight (MTOW). Thus, if it is desired to take an existing aircraft design and modify it to have a significantly higher maximum take-off weight, significant redesign work would typically be required of the landing gear assemblies. The total number of wheels the aircraft needs may have to increase. Given that the conventional landing gear configurations are difficult to adapt for use with an odd number of wheels, and given that there are typically an even number of main landing gear legs (disposed symmetrically about the longitudinal vertical mid-plane of the aircraft), increasing the MTOW of an aircraft by a certain amount will cause the number of wheels to increase by four, causing a significant jump in mass for what might be a relatively modest jump in passenger/cargo capacity for the aircraft design. An alternative approach would be to provide for an additional two-wheel main landing gear at the aircraft centreline, but such a solution also adds significant mass.

Also, redesigning landing gear for use on an aircraft so that the newly designed aircraft has an extended wing tip, as might be required for better aerodynamic performance for example, is difficult to achieve with the conflicting requirements that may arise for a wing mounted landing gear. The shape of the wing may require the wheels to be located significantly behind (aft) the rear spar of the wing via which the landing gear is mounted. However, the oleo strut may need to be arranged to transmit loads in a direction that is substantially parallel with its axis, thus preventing the oleo strut from being angled too far beyond vertical (typically being angled at 6 degrees or less).

When designing or redesigning a landing gear assembly for an aircraft, conventional wisdom is to seek to keep the mass of the landing gear assembly as low as practically possible.

The present invention seeks to mitigate one or more of the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved aircraft landing gear assembly. Alternatively or additionally, the present invention seeks to provide a design platform from which multiple different landing gear assemblies may be readily designed and/or manufactured.

SUMMARY OF THE INVENTION

The present invention provides according to an aspect of the invention a modular aircraft landing gear assembly, wherein the modular aircraft landing gear assembly comprises a modular landing gear bracket, which in use is connected to the aircraft via a hinge, for example, for rotating the aircraft landing gear assembly between a deployed position and a stowed position. The bracket is arranged to carry one or more wheels, preferably at least two. A lever, which in use carries at least one wheel, is rotatably mounted to the bracket. The axis of rotation of the lever may for example be parallel (or close to parallel) to the axis of a wheel carried by the lever in use. The modular aircraft landing gear assembly also includes a linkage assembly, which may for example be pivotally mounted the bracket, which linkage assembly in use transmits at least some of the ground load via at least one of a spring and a shock absorber. The structure of the bracket itself may be substantially rigid, for example thus providing negligible shock absorption or resilience (springiness). The modular landing gear bracket also comprises redundant structure, which is surplus to requirements for operation of the aircraft on which the aircraft landing gear assembly is to be used. The redundant structure may for example comprise one or more of an additional mounting point, for example for a part or portion of a linkage assembly to be mounted on the bracket when the same design (or substantially the same design) of bracket is used on a differently sized aircraft. Such a redundant or additional mounting point of the bracket may be associated with load carrying mass of the bracket (e.g. for transmitting at least some of the ground load from the wheels into the aircraft) which could also be considered as redundant. The redundant structure may, for this or other reasons, include additional mass.

Thus, in accordance with embodiments of the invention, there is provided a modular aircraft landing gear assembly, which can be reused on different types of aircraft (for example, having a longer fuselage and/or a different MTOW) without the need for significant redesign of the aircraft landing gear assembly for the subsequently designed aircraft. The certification of the aircraft landing gear assembly for the subsequently designed aircraft may also be made simpler and/or quicker.

The bracket may be shaped such that it extends from a hinge portion to a first mounting point, for receiving a ground load from one or more wheels, in use. Such a hinge portion may be configured for mounting the bracket for rotation relative to a landing gear bay. The modular landing gear bracket may include a second mounting point at a fore location of the hinge portion and a third mounting point at an aft location of the hinge portion. The bracket may have two mounting points only on the hinge portion for mounting for rotation relative to the aircraft. Each mounting point on the hinge portion may in use be associated with a pintle.

The bracket may thus be configured so that the ground load received at the first mounting point is, in use, transferred into aircraft structure (e.g. into the wing, fuselage, or other main structure of the aircraft) via the second mounting point and the third mounting point. In the fore-to-aft direction, the second mounting point may be the first mounting point for mounting the bracket relative to the landing gear bay via the hinge portion, and the third mounting point may be the last.

The bracket may include structure for receiving a second aircraft wheel, such a structure for example being the same lever as that which carries the first wheel. Such a structure may for example be a further lever, for example similar to the lever carrying the first wheel. When two levers are provided, they may be mounted to the bracket at the same mounting point. One of the levers may be positioned behind the other, in the fore-aft direction. The linkage assembly may be pivotally mounted via a fourth mounting point of the bracket. The linkage assembly may be modular in design, for example in that different configurations of linkage assemblies may be used in relation to the same design of bracket, to adapt the bracket for use for different purposes (e.g. on different designs of aircraft).

The modular aircraft landing gear assembly may be configured for a two-wheel configuration. In such a case, the redundant structure may facilitate reconfiguring the modular aircraft landing gear assembly for use with more wheels, for example with a three-wheel configuration or four-wheel configuration. The two-wheel configuration may be one in which the first and the second wheels are in line with each other (e.g. a tandem configuration).

The lever may have a first end which is rotatably mounted to the bracket at the first mounting point and a second end for receiving a first aircraft wheel. The second end of the first lever may be positioned forward of the first end. When a second lever is provided, it may have a first end which is rotatably mounted to the bracket (for example at, or near, the first mounting point) and a second end, positioned rearward of the first end, for receiving the second aircraft wheel. The second lever may carry a trailing wheel. (Of course, when there is only one lever—i.e. a single first lever—the first lever may be arranged such that it carries a trailing wheel. (The first lever may have a first end which is rotatably mounted to the bracket and a second end, positioned rearward of the first end, for receiving a wheel.) It may be that the aircraft wheel of the first lever is, in use with the aircraft on the ground, located to one side in an outboard direction of the mid-plane of the bracket (and/or for example to one side in the outboard direction of the first lever). It may be that the second lever is configured to receive the second aircraft wheel so that it is positioned in-line with the first wheel (for example also in an offset and/or outboard position). It may be that the first and second levers are arranged to carry between them two wheels in a diagonal arrangement, such that in use with the aircraft on the ground, the aircraft wheel of one of the first and second levers is located to one side in an outboard direction of the mid-plane of the bracket and the other aircraft wheel (i.e. of the other of the first and second levers) is located to the opposite side of the bracket (i.e. to one side in an inboard direction of the mid-plane of the bracket). In embodiments of the invention, the use of a bracket and two wheels in a tandem arrangement or in a diagonal arrangement, the wheels being offset from the bracket, can enable an efficient geometry for stowage of the aircraft landing gear assembly in a landing gear bay of the aircraft. A diagonal arrangement may have an advantage in that the first and second levers may be able to have the same shape as a result of the rotational symmetry of the levers and associated wheels on the landing gear.

The redundant structure of the bracket may be provided to enable the bracket to carry three wheels, for example two being arranged in diablo configuration (e.g. arranged to rotate about a common axis) and one being arranged either forward of or behind the two wheels. There may be two levers for this purpose. For example, one of the first lever and the second lever is configured to be able to carry two wheels in a diablo configuration, and the other of the first lever and the second lever is configured to be able to carry a single wheel. It may be that the single wheel is positioned, when viewed in the direction of travel on the ground, in between the two wheels of the diablo configuration. It may be that the single wheel is positioned in-line with the bracket. It may be that the two wheels of the diablo configuration are positioned such that one wheel is outboard of the lever and the other wheel is inboard of the lever.

In relation to a three-wheel configuration, there may be a linkage assembly (or assemblies) and associated spring(s) and/or shock absorber(s) for the two wheels which is/are bigger, stiffer and/or have more parts than a linkage assembly (or assemblies) and associated spring(s) and/or shock absorber(s) for the single wheel. There may be a linkage assembly (or assemblies) and associated spring(s) and/or shock absorber(s) for a three-wheel configuration which is/are bigger, stiffer and/or have more parts (for example, an extra linkage assembly) than a linkage assembly (or assemblies) and associated spring(s) and/or shock absorber(s) for a two-wheel configuration. The bracket may be so designed that substantially the same design of bracket is able to be used both with a two-wheel configuration and also a three-wheel (or more) configuration with little or no modifications to the shape and/or size of the bracket. It may be that modifications (of any significant type for example) are only necessary in relation to the number, size and/or configuration of the link assembly/assemblies, the spring(s) and/or shock absorber(s). There may be a respective shock absorber associated with each respective wheel.

One or more parts of such linkage assembly/assemblies provided for the three-wheel configuration may be absent from the modular aircraft landing gear assembly, when used for carrying two wheels.

The ability of the modular aircraft landing gear assembly to be converted between a two-wheel configuration and a three-wheel configuration, allows (in a much easier way) a smaller step-wise change in the total number of wheels (and therefore the additional weight provided by the extra wheels and associated parts and structure) than is possible with conventional landing gear design practices which typically rely on each main landing gear (MLG) having an even number of wheels. Such a possibility allows a more efficient step-wise change in mass, for example from a single aisle lightweight aircraft with two 2-wheel MLGs to a longer and heavier variant with two 3-wheel MLGs. Such a possibility might alternatively/additionally allow for a lighter and/or shorter variant as between a long-range heavy aircraft having two 4-wheel MLGs to a lighter variant having two 3-wheel MLGs.

The modular aircraft landing gear assembly may include a balance arm, for example rotatably mounted on the bracket (e.g. via a middle pivot point) for receiving load from both a fore lever carrying one or more wheels and an aft lever carrying one or more wheels. The arm may for example have a fore end pivot point connected to the first lever via one or more link members which transmit loads received from the first lever and/or the arm may have an aft end pivot point connected to the second lever via one or more link members which transmit loads received from the second lever. The balance arm may have a middle pivot point which is offset from the position midway between the fore end pivot point and the aft end pivot point. Having a balance arm, offset in this manner, may allow differently sized loads to be better distributed by the wheels and/or bracket and/or into the aircraft. The middle pivot point may be positioned closer to whichever of the fore and aft pivot points transmit the greater ground loads and/or are associated with the lever which carries the greater number of wheels. It may be that there is one lever that is configured to transmit significantly greater ground loads than the other. It may be that in use one lever transmits significantly greater ground loads than the other, but the two levers have a similar load bearing capacity, such that at least one of the levers has redundant mass, in use. In embodiments of the invention, the balance arm is associated with (connected to, possibly via one or more links) a compliant device, such as a shock absorber or dampener.

As mentioned above, the modular aircraft landing gear assembly may include one or more shock absorbers. The one or more shock absorbers may be the principal means by which dampening of the landing gear wheels is provided. There may be a single principal shock absorber provided per lever (on which the wheel(s) are mounted). There may be a first shock absorber which transmits loads from the first lever, for example without any intervening structure that functions as a spring or shock absorber. There may be one or more link members (for example of the linkage assembly) which are linked to the first shock absorber such that, in use, the link member(s) transmit(s) loads from the first lever. There may be a second shock absorber which transmits loads from the second lever, for example without any intervening structure that functions as a spring or shock absorber. There may be one or more link members (for example of the linkage assembly) which are linked to the second shock absorber such that, in use, the link member(s) transmit(s) loads from the second lever. One of the first and second shock absorbers may be a low pressure shock absorber. One (e.g. the other) of the first and second shock absorbers may be a high pressure shock absorber. The modular aircraft landing gear assembly may therefore include two or more shock absorbers, which collectively function as a multi-stage shock absorber system as a result of the differently pressured shock absorbers. There may be advantages in being able to segregate the high and low pressure stages of such a shock absorber system by providing them by means of separate shock absorbers. In embodiments of the invention, high and low pressure shock absorbers are linked via a balance arm.

It within the scope of the present invention for a variant of the bracket, or for the bracket of the aircraft landing gear assembly of the invention, to be raked at an angle to the vertical. The provision of a linking assembly may assist in the provision of a raked bracket. The linking assembly may allow a non-vertical, or angled shock absorber for example. The raked nature of the bracket may be such that, in use, when the aircraft is static and on the ground the first mounting point on the bracket (at which a lever is mounted) is located aft of the third mounting point (an aft mounting point of the hinge portion of the bracket, possibly the mounting point of the hinge portion that is furthest aft). The raked nature of the bracket may be such that, in use, when the aircraft is static and on the ground, the rake angle of the bracket is eight degrees or higher (e.g. greater than ten degrees). In certain embodiments, the rake angle of the bracket is defined by the angle to the vertical of the notional line extending from the first mounting point to the rearmost mounting point of the hinge portion (e.g. which may be the third mounting point). Having a design platform that allows for a raked bracket in this way enables embodiments of the invention with advantageous geometries for the use on an aircraft with wings having extended wingtips.

The linkage assembly may comprise a loading point which is movable relative to the hinge portion of the bracket. The loading point may for example receive ground loads from a lever carrying a wheel, when in use. The linkage assembly may comprise a spring system. The spring system may be configured to apply a resilient biasing force acting against the ground loads. The spring system may be configured to apply a resilient biasing force so that, during application of an increasing load, the spring rate of the spring system changes in dependence on the load being transmitted. The spring rate of the spring system may change from a first spring rate to a second spring rate, for example, the second spring rate being less than the first spring rate. As the applied load (e.g. from ground loads) against the resilient biasing force of the spring system is further increased, the spring rate of the spring system may change from the second spring rate to a third spring rate, the third spring rate being greater than the second spring rate, for example. The spring system may comprise a first spring element and a second spring element. A spring rate of the second spring element may be less than a spring rate of the first spring element. The loading point of the linkage assembly may be connected to the second spring element via the first spring element. The first spring element may be rotationally mounted to the bracket at the fourth mounting point mentioned above. The bracket may have a stop (which may be integrally formed, or provided on detachably mounted structure) that is configured to limit rotation of the linkage assembly beyond the stop. The second spring element may be configured to apply a preload. The bracket may have first and second stops configured to limit an angular range of rotation of the linkage assembly. The first spring element may comprise a leaf spring. The second spring element may comprise a leaf spring.

The modular landing gear bracket may include a fifth mounting point, for example, for the mounting of a further linkage assembly. Such a further linkage assembly may be positioned either fore or aft of the linkage assembly pivotally mounted via the fourth mounting point.

The bracket may carry substantially all of the vertical ground loads (or at least 80% of them) from its associated wheels into the aircraft. Some side loads, torsion loads, shear loads or the like may be carried by structure that is additional to the bracket. The bracket may have two principal load paths, comprising a fore load path and an aft load path. The bracket may be provided in the form of a frame structure. The frame structure may be an open frame. The main structure of the bracket may be provided by two, preferably similarly shaped, parts (e.g. plates), for example being in the form of two parallel spaced apart plates.

The landing gear assembly of the present invention may, or may not, be provided with one or more wheels mounted on the landing gear.

The present invention also provides a kit of parts for assembling the modular aircraft landing gear assembly according to any aspect of the invention as described or claimed herein. The kit may comprise one or more of the above mentioned modular landing gear brackets. The kit may comprise one or more of the above mentioned levers. The kit may comprise one or more of the above mentioned link assemblies. The kit may comprise one or more of a link member, the above mentioned spring or spring systems and the above mentioned shock absorber(s) for forming a linkage assembly.

The present invention also provides an aircraft including a modular aircraft landing gear assembly according to any aspect of the invention as described or claimed herein. The aircraft may be a single aisle aircraft. The aircraft may be a long range aircraft, having a range of more than 3,000 miles for example. The aircraft may be a passenger aircraft, for example an aircraft configured to carry more than 50 passengers, for example more than 100 passengers, possibly at least 200 passengers For the purposes of the present specification the term commercial passenger aircraft also covers aircraft of an equivalent size configured for cargo and/or used on a non-commercial basis. The aircraft may have a maximum take-off weight (MTOW) of at least 20 tonnes, optionally at least 40 tonnes, and possibly 50 tonnes or more. The aircraft may have an operating empty weight of at least 20 tonnes, optionally at least 30 tonnes, and possibly about 40 tonnes or more. The length of the aircraft is preferably greater than 25 m, and may be greater than 30 m. The length of the aircraft may be greater than 40 m.

There is also a method of manufacturing a landing gear assembly as defined in the claims and/or as described in further detail below. The method may include designing both (a) a first aircraft landing gear assembly for a first aircraft, and (b) a second aircraft landing gear assembly for a second aircraft. The first aircraft may have a fuselage of a first length and the second aircraft may have a fuselage of a second longer length, for example longer by at least 5 m and possibly by at least 10 m. The first aircraft may have a first MTOW and the second aircraft may have second higher MTOW, for example higher by at least 5 tonnes, and possibly higher by at least 10 tonnes. It may be that the first aircraft landing gear assembly is either a two-wheel tandem landing gear assembly or a two-wheel diablo landing gear assembly. It may be that the second aircraft landing gear assembly has one more wheel than the first aircraft landing gear assembly (i.e. a step from two to three, or a step from three to four wheels per MLG). There may be features or mass of the first aircraft landing gear assembly that are redundant for the purpose of operation of the first aircraft but which are used as features or mass of the second aircraft landing gear assembly. Such redundant features and/or redundant mass as are provided on the first aircraft landing gear assembly may have a combined mass that is greater than 0.1% of the total mass (possibly greater than 0.5%, and possibly greater than 1%) of the first aircraft landing gear assembly (excluding the wheels, brakes, and brake systems). Such redundant features and/or redundant mass as are provided on the first aircraft landing gear assembly may have a combined mass that is greater than 1 Kg, possibly greater than 5 Kg, and optionally greater than 10 Kg. The first aircraft may be a single aisle aircraft. The second aircraft may be a long range aircraft. The second aircraft landing gear assembly may have a different topology/geometry in relation to how the wheels are mounted on the landing gear. For example, it may be that the first aircraft landing gear assembly is a two-wheel tandem landing gear assembly and the second is a two-wheel diablo landing gear assembly. It may be that the first aircraft landing gear assembly is a two-wheel diablo landing gear assembly and the second is a two-wheel tandem landing gear assembly. It may be that the second aircraft landing gear assembly has three or more wheels, whereas the first aircraft landing gear assembly has only two. The first aircraft landing gear assembly may comprise a modular load-bearing frame, modular load-bearing bracket or the like. It will be appreciated that one of the first and second aircraft landing gear assemblies may be a design modification of the other, in that there need not be any wholescale redesign of the earlier design in the creation of the later design. For example, one of the first and second aircraft landing gear assemblies may be a design modification of the other utilising a common generic design model. The common generic design model may utilise the same modular load-bearing frame, modular load-bearing bracket or the like. The common generic design model may utilise the same separation of locations of the mounting points of the aircraft landing gear to the aircraft. It may be that the load-bearing frame of the second aircraft has the same geometry as the load-bearing frame of the first aircraft but is scaled up. It may be that the load-bearing frame of the second aircraft has the same shape (and, for example, also the same overall size) as the load-bearing frame of the first aircraft but is strengthened by use of extra mass in the structure of the load-bearing frame.

It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of the invention may incorporate any of the features described with reference to the apparatus of the invention and vice versa.

DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which:

FIG. 1 is a perspective view of part of an aircraft showing a modular aircraft landing gear assembly according to an embodiment of the invention;

FIG. 2 is a sectional side view of the aircraft landing gear assembly of FIG. 1;

FIG. 3 is a side view of an aircraft which may incorporate a landing gear assembly of an embodiment of the invention;

FIG. 4 is a perspective view of part of an aircraft showing a modular aircraft landing gear assembly according to a further embodiment of the invention, in which the wheels are offset to one side;

FIG. 5 is a perspective view of part of an aircraft showing a modular aircraft landing gear assembly for a three-wheel configuration according to an embodiment of the invention,

FIG. 6 is a sectional side view of the aircraft landing gear assembly of FIG. 5;

FIG. 7 is a sectional side view of an aircraft showing a modular aircraft landing gear assembly according to a further embodiment of the invention using a shock absorber and an associated offset balance arm;

FIG. 8 is a sectional side view of an aircraft showing a modular aircraft landing gear assembly according to a further embodiment of the invention using segregated high-pressure and low-pressure shock absorber in combination;

FIG. 9 is a sectional side view of an aircraft showing a modular aircraft landing gear assembly according to a further embodiment in which a raked bracket is used;

FIG. 10 is a perspective view of a modification to the embodiment shown in FIG. 1;

FIG. 11 is a perspective view of a further modification to the embodiment shown in FIG. 1; and

FIG. 12 shows a flowchart of the steps of a method of manufacturing an aircraft landing gear assembly according to an embodiment of the invention.

DETAILED DESCRIPTION

FIGS. 1 and 2 show schematically an aircraft landing gear assembly 10 suitable for use on an aircraft 12 (such as that also shown in FIG. 3). The fore direction is shown in FIG. 1 with the arrow labelled F. The aircraft landing gear assembly comprises a bracket and spring assembly arrangement for transmitting ground loads, which has various potential design advantages as compared to prior landing gear assemblies which transmit the majority of ground loads utilising a single elongate landing gear leg with an integrated shock absorber (referred to in the art often as an oleo landing gear design). The bracket acts as the main fitting for the aircraft landing gear assembly.

The landing gear assembly of FIG. 1 includes a bracket 14 extending from a hinge portion 18 to a first mounting point 20 for mounting one or more wheels 22 via one or more pivoting levers 16. The hinge portion 18 allows for mounting of the bracket 14 for rotation relative to a landing gear bay, so that the landing gear assembly 10 may move between a stowed position (in the landing gear bay) to a deployed position (for landing, taxiing and take-off), as shown in FIGS. 1 and 2. In the deployed position, the first mounting point 20 receives ground loads from the wheels 22 when the aircraft's weight is supported on the ground. There may also be a side-stay assembly (not shown) for reacting lateral loads on the landing gear which transmit loads into the aircraft at a further location. It will be noted that the perspective views in the Figures show different details from that shown in the side views. For example, FIG. 2 shows a hinge tube 19, not shown in FIG. 1, which passes loads from the bracket into the aircraft structure 12 via two outer mounting points (not labelled in FIG. 1).

The bracket 14 has a second mounting point 24 at a fore location of the hinge portion 18 and a third mounting point 26 at an aft location of the hinge portion, for mounting of the bracket 14 to aircraft structure, in this case to the fuselage of the aircraft. In FIG. 1, it will be seen that there are two further locations, one forward of the second mounting point 24 and one aft of the third mounting point 26, for mounting of the bracket 14 to aircraft structure, there thus being four locations in total. It will also be seen from FIG. 1 that the bracket 14 comprises two parallel spaced-apart plates, each having a (very generally) triangular shape (the base of the triangle corresponding to the hinge portion and the first mounting point 20 being at or close to apex of the triangle, opposite the base).

With reference to FIG. 2, there are two levers 16, each being rotatably mounted at one end to the bracket 14 at the first mounting point 20 and each receiving an aircraft wheel 22 at the opposite end. Each lever 16 is associated with a spring assembly 130, which may be considered as being, or forming part of, an independent modular suspension system for the wheel(s) carried by the lever with which the spring assembly 130 is associated. The wheel 22 is mounted for rotation about an axis 30. The lever 16 rigidly connects between three points: the first mounting point 20, the wheel axis 30, and an end 135b of a linkage 135 (the other end 135a of which pivotally connects to an end of a first spring element 131 which forms part of the spring assembly 130, as is explained in further detail below). In use, the load from the wheel 22 is applied to a loading point 120 via the lever 16 and the linkage 135.

The spring assembly 130 may comprise one or more spring elements, the number being chosen in dependence on the requirements of the landing gear/aircraft. One or more shock absorbers, dampeners or other means for dissipating motion are incorporated into the spring assembly or suspension system to absorb or dampen shock impulses applied to the spring assembly or suspension system in use.

The nature of the bracket, the separate levers, the separate spring assemblies and associated linkages provides a design platform that facilitates the design of landing gear assemblies for different aircraft using a modular design approach. Many landing gear designs for modern passenger aircraft having a MTOW of more than, say, 20 tonnes feature retractable landing gear assemblies. Each landing gear assembly (according to such a prior art aircraft design) typically comprises a landing gear leg in the form of a hydraulic strut which is configured to support the majority of the vertical ground loads when the aircraft lands, takes-off or performs ground manoeuvres. (It will of course be appreciated that such vertical struts also react non-vertical loads in use too.) If a first aircraft is designed using a landing gear carrying a certain number of wheels, and that design of aircraft is utilised as the starting point for the design of a future aircraft having a different length and a different MTOW (for example by starting with stretching or shrinking the length only of the fuselage), it is often the case that a different number of wheels will be required of at least one of the landing gear assemblies and/or a differently sized hydraulic strut will be required. Reconfiguring the landing gear assembly to be suitable for a resized aircraft can thus involve a significant redesign of the landing gear assembly (or, effectively, a new design of landing gear assembly). If the same or similar landing gear assembly could be re-used, or reconfigured for a new purpose without requiring any fundamental design changes, then not only could the design process be speeded up, but also certification of the aircraft could be made easier and/or faster.

Designing a landing gear assembly using a modular aircraft landing gear assembly such as that shown in FIGS. 1 and 2, may result in one design of landing gear having redundant structure, which is however fully utilised in a different aircraft (for example, one having a longer fuselage or a higher MTOW). It may be that such redundant structure adds redundant mass in the landing gear assembly of one aircraft on which the bracket is used, but this may be relatively minor. Furthermore, any disadvantage associated with such modest increase in mass, can be more than offset by the potential advantages gained by the simplification of the redesign and/or recertification needed for the aircraft landing gear assembly for the subsequently designed aircraft. Costs associated with manufacturing may also be reduced, when utilising such a modular design. The bracket 14 of FIGS. 1 and 2 comprises redundant structure, which is surplus to requirements for operation of the aircraft on which the aircraft landing gear assembly is to be used. In this embodiment, there is redundant structure provided as a result of additional mounting points 28r on the bracket 14, such redundant mounting points being for a linkage assembly/spring assembly, which is not used on the aircraft shown but which could be utilised on a different set-up for a different aircraft to assist in the transmitting of some of the ground loads. The bracket 14 itself is larger (and therefore more massive) than required for the operation of the aircraft on which it is installed, so that it is also suitable for use on heavier aircraft or on a landing gear assembly which must be capable of sustaining higher ground loads.

The spring assembly 130 is similar to that disclosed in the embodiments of GB 2 568 742, the contents of which being incorporated by reference thereto. However, a brief explanation of the spring assembly 130 and other subject matter covered by GB 2 568 742 is also included in the description, which now follows.

Each spring assembly 130 includes first spring elements 131 and second spring elements 132. The first spring elements 131 form part of a linkage assembly transferring loads from the wheel 22 via its lever 16 into the bracket 14. The first spring elements 131 are mounted on the bracket at a fourth mounting point 28 of the bracket, permitting pivoting movement of the first spring elements 131 relative to the bracket.

The second spring element 132 is associated with a preload applicator 134 (described below). The spring assembly 130 comprises a loading point 120 for receiving ground load from the wheel(s) in use. The loading point 120 in this embodiment is at the joint between the linkage 135 and the first spring element 131. The loading point 120 is thus movable relative to the hinge portion 18. The spring assembly 130 is configured to apply a resilient biasing force to the loading point 120 to oppose movement of the loading point 120 relative to the hinge portion 18. In this embodiment, the loading point 120 is movable towards and away from the hinge portion 18, and the spring system or spring assembly 130 is configured to apply a resilient biasing force to the loading point 120 to oppose movement of the loading point 120 towards the hinge portion 18. During application of an increasing load to the loading point 120 against the resilient biasing force of the spring assembly 130, a spring rate of the spring assembly 130 changes from a first spring rate to a second spring rate, the second spring rate being less than the first spring rate. The first spring rate can therefore be a relatively moderate spring rate for getting load onto the wheel(s), which can help lessen or avoid skidding and to help improve braking drag. The second, lower spring rate can thereafter help provide a soft ride characteristic. In this embodiment, the movement of the loading point 120 is towards the hinge portion 18 during application of the increasing load to the loading point 120, such as during a landing procedure or event. In this embodiment, the spring assembly 130 is also configured so that, if the load applied to the loading point 120 against the resilient biasing force further increases, the spring rate of the spring assembly 130 changes from the second spring rate to a third spring rate, the third spring rate being greater than the second spring rate. This third spring rate can help to react loads in high-descent-rate landings, and/or may help to improve lateral stability when the aircraft to which the landing gear is mounted is taxiing or otherwise turning on the ground. The third spring rate may be substantially equal to the first spring rate in certain embodiments, and may be less than (or greater than) the first spring rate in others.

The spring elements 131 and 132 each comprise a leaf spring. Use of leaf springs can enable the spring assembly 130 to begin to compress as soon as a load is applied to the loading point 120. That is, the spring assembly 130 may be considered to have a zero, or substantially zero, break-out load. This can facilitate weight-on-wheels detection, such as to determine whether the landing gear 10 (and the aircraft 12 to which it is mounted) has landed.

In this embodiment, the first spring element 131 is coupled to the second spring element 132 via a link 133. A first end of the link 133 is pivotally coupled to the first spring element 131, and a second end of the link 133 is pivotally coupled to the second spring element 132. In other embodiments, the link 133 may be omitted. In some such embodiments, the first spring element 131 may be pivotally coupled directly to the second spring element 132. The spring elements themselves may be considered as links which form the overall linkage assembly.

The bracket 14 of this embodiment has a first stop 141 and a second stop 142, which together are configured to limit an angular range of rotation of the first spring element 131 about the mounting point 28. The first stop 141 limits rotation during the application of the increasing load to the loading point 120, whereas the second stop 142 limits rotation during removal or reduction of the load. One end of the second spring element 132 is rotationally mounted to the bracket 14 at a further mounting point 144.

The preload applicator 134 of the spring assembly 130 of this embodiment is provided for applying a preload to the second spring element 132 and thus apply a preload to the first spring element 131, to bias the first spring element 131 away from the first stop 141 of the bracket 14. Thus, when increasing load is applied to the loading point 120 from the wheel 22 rotational movement of the first spring element 131 is caused about the mounting point 28 in one rotational direction, whereas the preload biases the first spring element 131 to move in the opposite rotational direction.

For some designs of landing gear, the spring assembly 130 may comprise one first spring element 131 and plural second spring elements 132 (for example such that a combined spring rate of the plural second spring elements 132 is less than the spring rate of the first spring element 131). In still further embodiments, the spring assembly 130 may comprise plural first spring elements 131 and one second spring element 132 (for example, the spring rate of the second spring element 132 being less than the combined spring rate of the plural first spring elements 131).

The loads that are passed from the bracket and/or the hinge tube 19 into the aircraft are shown schematically by the vertical arrows 39, 40, 42, 43 at the top of FIG. 2. In other embodiments, the bracket 14 may be shaped to extend as far as the loading points indicated by arrows 40 and 42. In this embodiment, there are two tubular attachments 19, one each at the forward and aft attachment points. These tubular elements 19 are each connected in a rotational sense only (i.e. about the retraction axis) to the (smaller) bracket 14 (as shown in FIG. 1) by a rotatable coupling (not shown in FIG. 1) shown in FIG. 2 as an inverted “U” 45. The loads into the airframe structure are therefore via multiple (smaller) load paths, thus spreading the load more evenly into the aircraft fuselage. The loads transmitted from the mounting points 20 and 28 via the bracket 14 into the airframe (via the second and third mounting points 24, 26) are shown by the smaller “up” arrows 39, 43. The loads transmitted via the second spring elements 132 are transmitted via the fore and aft rotatable couplings 19 into the outer attachment points (as represented by the larger arrows 40, 42 in FIG. 2), and to some extent into the inner two load point (via points 24, 26).

As mentioned above, the embodiment shown in FIGS. 1 and 2 may be used as a modular aircraft landing gear assembly design platform, enabling the design and manufacture of different configuration of landing gear assemblies, each being configured for use on an aircraft type within a family of aircraft designs differing from one another, for example, by MTOW, length of aircraft, and/or load capacity. Such different designs/configurations of landing gear assemblies are illustrated in the accompanying Figures. Alternatively, any of those different designs/configurations of landing gear assemblies as illustrated in the other Figures may be used as the base design or platform from which other different designs/configurations of landing gear assemblies are created. Alternatively, a non-illustrated landing gear assembly may be used as the base design or platform from which the other different designs/configurations of landing gear assemblies are created.

FIG. 4 shows a landing gear assembly according to an embodiment similar to that shown in FIGS. 1 and 2. Like reference numerals are used for like parts, but adding 2000 to the numbers used in FIGS. 1 and 2. The main differences between the two embodiments will now be described. The landing gear 2010 has two levers 2016 each carrying one wheel 2022 on an axle that is located to one side, in an outboard direction, of the bracket 2014 (and also in a position located to one side, in an outboard direction, of the lever). The wheels 2022 are arranged in a tandem offset configuration. The profile of the landing gear assembly 2010 in the direction of flight is therefore relatively slim in the span-wise direction, and has a geometry and size that is able to make very good use of the space available when stowed. The landing gear bay can thus be made smaller and/or include space for other additional systems of parts of the aircraft. Such a configuration may be particularly suitable for a landing gear that is required to be stowed under the cabin floor.

In an alternative embodiment to FIG. 4, the two wheels could be arranged on opposite sides of the bracket, one inboard and one outboard—in a diagonal arrangement. This may also enable the landing gear to be more efficiently shaped, for example, enabling a belly fairing under the landing gear when stowed to be smaller or better shaped.

Thus, the subject matter embodied by FIG. 4 and the above-described alternative may be described in more general terms as being an aircraft landing gear assembly comprising a, preferably modular, landing gear bracket, on which a first lever and a second lever are mounted, for receiving wheels mounted off-centre with respect to the bracket (preferably to one side of the bracket, e.g. one or both offset to one side in the outboard direction). There are various preferred features relating to this generalised subject matter which will now be described. The modular landing gear bracket extends from a hinge portion to a first mounting point, the first mounting point being for receiving a ground load from one or more wheels, in use. The hinge portion is configured for mounting the bracket for rotation relative to a landing gear bay. The bracket includes a second mounting point at a fore location of the hinge portion and a third mounting point at an aft location of the hinge portion. The bracket is configured so that the ground load received at the first mounting point is, in use, transferred into aircraft structure (for example wing or fuselage) via the second mounting point and the third mounting point. The first lever has a first end which is rotatably mounted to the bracket at the first mounting point and a second end, positioned forward of the first end, for receiving a first aircraft wheel. Similarly, the second lever has a first end which is rotatably mounted to the bracket at the first mounting point and a second end, positioned rearward of the first end, for receiving a second aircraft wheel. The second aircraft wheel may be positioned in-line with the first wheel. One of the first wheel and the second wheel may be received in a position located to one side in an outboard direction of the mid-plane of the bracket; and/or in a position located to one side in an outboard direction of the mid-plane of the second lever. The second aircraft wheel may be positioned on the opposite side of the bracket from the first wheel (e.g. one outboard and on inboard). The aircraft landing gear assembly may be configured to carry two wheels only.

FIGS. 5 and 6 shows a landing gear assembly according to an embodiment similar to that shown in FIGS. 1 and 2. Like reference numerals are used for like parts, but adding 3000 to the numbers used in FIGS. 1 and 2. The main differences between the two embodiments will now be described. The landing gear 3010 has two levers 3016 which between them carry three wheels 3022. In this embodiment, the fore wheel 3022f is mounted such that it is arranged centrally (in the span-wise direction) relative to the bracket. The centre plane of the wheel 3022f—such a plane having the wheel axis as its normal—is substantially coplanar with the corresponding centre plane of the bracket (or at least, the bracket 3014 and wheel 3022f are so arranged that the main load bearing structure of the bracket extends to either side of the centre plane of the wheel). The central mounting of this fore wheel 3022f is readily achieved as a result of the spaced apart parallel plates that form the bracket 3014. The aft wheels 3022a behind the fore wheel 3022f are in a diablo arrangement (axes lying on a common notional line), with one aft wheel 3022a being located to one side in an outboard direction of the bracket 3014 (and also in a position located to one side in an outboard direction of the lever 3016) and the other aft wheel 3022a being located to the other side (i.e. in an inboard direction) of the bracket 3014 (and also in a position located to one side in the inboard direction of the lever 3016).

A bigger spring assembly is associated with the two wheels than is provided for the single wheel (this need not be twice the size however). With reference to FIG. 6, the fore spring assembly 3130f associated with the single fore wheel 3022f has a first spring element 3131f in the form of a single leaf spring and a second spring element 3132f also in the form of a single leaf spring. The aft spring assembly 3130a associated with the dual wheels 3022a has two first spring elements 3131a in the form of two leaf springs arranged in parallel and a second spring element 3132a also in the form of two leaf springs arranged in parallel.

In an alternative embodiment, a separate spring assembly is associated with each of the three wheels (the two spring assemblies associated with the one lever may each be less massive and/or less resilient and/or each carry less load, than the single spring assembly associated with the other lever carrying only one wheel). For example, the two spring assemblies associated with the two wheels may be provided on opposite sides of the bracket, for example one assembly mounted on one plate on one side of the bracket and the other spring assembly being mounted on the other plate on the opposite side of the bracket.

It will be noted that the shape of the bracket 3014 is the same as the bracket 14 of FIGS. 1 and 2. In these respective embodiments, the same shape, size, and material is used. The multiple applications to which the same part (the bracket) can be used may lead to the part having redundant mass or other features when used in one application (greater redundant mass typically being viewed very negatively in aircraft design) but the part having the great benefit of forming part of a modular kit for landing gear design and manufacture. It will be seen that a mounting point and its associated hole (labelled 3028r in FIG. 6) is redundant. A comparison of the relative loads expected to be transmitted into the aircraft illustrated schematically by the arrows at the top of FIGS. 2 and 6 shows that the expected load 3040 at the far fore end of the hinge portion of the bracket 3014 of FIG. 6 is less than the expected load 3042 at the far aft end; whereas when compared to the spread of loads shown in FIG. 2, the relative loads 40, 42 at the far fore end and the far aft end are similar in magnitude. The mass and shape of the hinge portion of the bracket as compared between FIGS. 1 and 5 is very similar (optimally substantially the same).

The modular landing gear bracket thus facilitates the move from a two-wheel gear design gear to a three-wheel gear design, without a disproportionate increase in mass, without a disproportionate change in structure and without a disproportionate amount of redesign work required. The use of a three-wheel gear design is also one that is not common in the aircraft industry, it often being the case that aircraft manufactures favour (possibly as a prejudice in the art) adding wheels in pairs to landing gear assemblies if and when an aircraft is to be designed and manufactured using a previous aircraft design needing fewer wheels. Thus, the conventionally accepted practice of adding two wheels to the main landing gears when designing a new aircraft, that has a higher MTOW than the base-level design having two main landing gears each with only two wheels, can add a significant mass to the aircraft, in terms of the wheels, tyres and associated brakes alone (total mass of more than 250 Kg per wheel being typical). If two wheels are added (to make two main landing gears each with three wheels) rather than adding four wheels, there is the potential for a mass saving of more than 500 Kg, which would make a very large operational saving over the lifetime of the aircraft.

Thus, the subject matter embodied by FIG. 5 may be described in more general terms as being an aircraft landing gear assembly comprising a landing gear bracket, preferably a modular bracket, on which a first lever and a second lever are mounted, one for receiving two wheels in side-by-side configuration (e.g. in a diablo configuration) and the other for receiving a single wheel, thus providing a three-wheel landing gear assembly. There are various preferred features relating to this generalised subject matter which will now be described. The landing gear bracket may have a hinge portion, a first mounting point, a second mounting point, and a third mounting point in a manner similar to that described above in relation to the general subject matter embodied by FIG. 4. The single wheel may be positioned in-line with the bracket, for example so that the centre plane of the single wheel is substantially coplanar with the corresponding centre plane of the bracket and/or lies in the middle of the two centre planes of the wheels that are arranged side-by-side. One or more shock absorbers may be provided, for example there being greater shock absorbing capacity associated with the lever carrying two wheels than the shock absorbing capacity associated with the other lever carrying the single wheel. There may be more separate shock absorbers associated with the lever carrying two wheels than the number of shock absorbers associated with the other lever. A balance arm may be provided (see further explanation below) which may be mounted for rotation relative to the bracket for reacting, on one side of the arm, the loads from the fore wheel(s) and, on the other side of the arm, the loads from the aft wheel(s).

FIG. 7 shows a three-wheel landing gear assembly according to an embodiment similar to that shown in FIGS. 5 and 6 (and also to FIGS. 1 and 2). Like reference numerals are used for like parts, but adding 4000 to the numbers used in FIGS. 1 and 2. The main differences between the two three-wheel embodiments will now be described. The bracket 4014 is shorter in the fore-aft direction at its upper end, in that the hinge portion is shorter. The loads transmitted into the aircraft body are therefore more concentrated (in the fore-aft direction). In a variation of this embodiment, the hinge portion is the same length and the bracket 4014 has a substantially identical shape as in FIG. 1. The bracket 4014 also uses a shock absorber and linkage system 4050 instead of one or more spring assemblies. As such the structure providing the stops that interact with the spring system as shown in FIG. 1 (which stop structure may be modular—and separately removable—in any case) is not present in the embodiment of FIG. 7. The shock absorber and linkage system 4050 comprises a link 4052 pivotally mounted to the fore lever 4016f at one end and pivotally mounted at the other end to a fore end of the balance arm 4054 at a fore pivot point 4054f. A principal pivot point of the balance arm 4054 is pivotally mounted at a mounting point 4056 on the bracket near the middle of the bracket as viewed in FIG. 7. A shock absorber 4058, pivotally mounted to the aft lever 4016a at one end, is pivotally mounted at the other end to the aft end of balance arm 4054 (at an aft pivot point 4054a). Greater loads are expected at the aft end of the balance arm 4054 as a result of the loads transferred from the two aft wheels 4022a as compared to the loads expected at the fore end of the balance arm 4054 from the loads transferred from the single fore wheel 4022f. To better balance the moments on the balance arm it is mounted in an offset position such that point on the balance arm corresponding to the mounting point 4056 is positioned off-centre and closer to the aft mounting point 4054a on the balance arm. The loads on the wheels should therefore be more evenly distributed and the loads into the aircraft may be better distributed.

Thus, the subject matter embodied by FIG. 7 may be described in more general terms as being an aircraft landing gear assembly comprising an aircraft landing gear assembly comprising a landing gear bracket, preferably a modular bracket, on which a first lever and a second lever are mounted, one for receiving two wheels and the other for receiving a single wheel, thus providing a three-wheel landing gear assembly, wherein a balance arm is provided for reacting and/or transmitting the differing loads received from the wheels. The balance arm may, for example, be mounted for rotation about a point which is offset from the midway point between the point at which the fore wheel(s) loads are received at the arm and aft wheel(s) loads are received at the arm. It may be that the loads from the first and second levers are unequal loads, for example. There are various preferred features relating to this generalised subject matter which will now be described. The landing gear bracket may have a hinge portion, a first mounting point, a second mounting point, and a third mounting point in a manner similar to that described above in relation to the general subject matter embodied by FIG. 4. The arm has a fore end pivot point connected to a lever via one or more link members which transmit loads received from the lever. The arm has an aft end pivot point connected to a lever via one or more link members which transmit loads received from the lever. The two wheels on the one lever may be provided in a side-by-side configuration (e.g. in a diablo configuration). The first lever may have a first end which is rotatably mounted to the bracket at the first mounting point and a second end, positioned forward of the first end, for receiving an aircraft wheel. The second lever may have a first end which is rotatably mounted to the bracket (e.g. at the first mounting point) and a second end, positioned rearward of the first end, for receiving a second aircraft wheel.

FIG. 8 shows a landing gear assembly according to an embodiment similar to that shown in FIG. 7. Like reference numerals are used for like parts, but starting with a “5” not a “4” as in FIG. 7 (adding 5000 to the numbers used in FIGS. 1 and 2). The main differences will now be described. The landing gear carries four wheels 5022, with a similarly sized bracket 5014, but using an extra shock absorber. There are thus two shock absorbers: a fore shock absorber 5058f and an aft shock absorber 5058a, each pivotally mounted at opposite ends 5054a, 5054f of the balance arm 5054. In this embodiment, the balance arm is mounted at a centre point 5056 to the bracket 5014 which is located midway (or very close to midway) between the aft mounting point 5054a and the fore mounting point 5054f on the balance arm. The fore shock absorber 5058f is a high pressure shock absorber (transferring high load for a given effective surface area), whereas the aft shock absorber 5058a is a low pressure absorber. The linkage assembly comprising the two segregated and different shock absorbers, and the balance arm, is thus able to act as a two-stage shock absorbing system for the four wheels. In a variation of the embodiment, there are three wheels, and the two shock absorbers are both at substantially the same pressure, but the oleo area of the shock absorber associated with the single wheel is half that of the oleo area of the shock absorber associated with the dual wheels.

Thus, the subject matter embodied by FIG. 8 may be described in more general terms as being an aircraft landing gear assembly comprising an aircraft landing gear assembly comprising a landing gear bracket, preferably a modular bracket, on which first and second levers are mounted for receiving two or more wheels between them, a balance arm pivotally mounted on the bracket the balance arm being connected, via one or more link members and/or shock absorbers for example, for reacting and/or transmitting ground loads received from the wheels. There are various preferred features relating to this generalised subject matter which will now be described. The landing gear bracket may have a hinge portion, a first mounting point, a second mounting point, and a third mounting point in a manner similar to that described above in relation to the general subject matter embodied by FIG. 7. The balance arm is rotatably mounted on the bracket via a middle pivot point, the arm having a fore end pivot point connected to the first lever via one or more link members and an aft end pivot point connected to the second lever via one or more link members. One or more of the link members may comprise a shock absorber. The one or more link members connecting the first lever to the balance arm may comprise the first shock absorber (which therefore transmits loads received from the first lever). Similarly, the one or more link members connecting the aft end pivot point of the arm to the second lever may comprise the second shock absorber (which therefore transmit loads received from the second lever). The balance arm may thus be connected at either end to a respective shock absorber. One of the first and second shock absorbers is a low pressure shock absorber, the other being a high pressure shock absorber. (The terms low pressure shock absorber and high pressure shock absorber are relative and convey the meaning merely that the pressure of the low pressure shock absorber is lower than the pressure of high pressure shock absorber; rather than placing any absolute limits on the operating pressure of either the low pressure shock absorber or the high pressure shock absorber.)

FIG. 9 shows a landing gear assembly according to an embodiment similar to that shown in FIG. 7. Like reference numerals are used for like parts, but starting with a “6” not a “4” as in FIG. 7 (adding 6000 to the numbers used in FIGS. 1 and 2). The main differences will now be described. The landing gear 6010 carries two wheels 6022, with a raked bracket 6014 having a wing-mounted hinged portion 6018. Loads are transmitted into the wing from the bracket 6014 at two points. (It will be appreciated that there may be a side stay—not shown—additionally). The bracket 6014 has a shock absorber and linkage system 6050, but in reverse configuration with the link 6052 pivotally mounted to the aft lever 6016a at one end and pivotally mounted at the other end to the aft end of the balance arm 6054 at the aft pivot point 6054a. The shock absorber 6058 is pivotally mounted to the fore lever 6016f at one end and pivotally mounted at the other end to the fore end of balance arm 6054 (at the fore pivot point 6054f). The principal pivot point of the balance arm 6054 is centrally located relative to the aft pivot point 6054a and the fore pivot point 6054f. The principal pivot point of the balance arm 6054 is however located off-centre (to the aft side) of the bracket and also rearward of the aft mounting point 6026 of the hinge portion 6018 of the bracket 6014. The bracket is raked and thus has a trailing wheel configuration. The rake angle is, in this embodiment, defined as the angle to the vertical of the notional line that extends between the first mounting point 6020 on the bracket to the rearmost mounting point (the third mounting point 6026) on the bracket 6014. The rake angle shown in FIG. 9 according to this definition is greater than 15 degrees, and significantly greater than 6 degrees, which might be viewed as the maximum practical angle by which an oleo cylinder of a conventional landing gear leg could be raked. The embodiment of FIG. 9 may have particular application in relation to an aircraft having extended wing tips (e.g. for increased aerodynamic efficiency). Such wings have a mean aerodynamic chord which is longer, which has the effect of requiring the main landing gear wheels to shift aft, which means that the wheels end up further away from the rear spar (in the fore-aft direction). Utilising the lever assembly shown in FIG. 9 allows a shock absorber to be used at a greater range of angles to the vertical, thus allowing the landing gear assembly to have an effective rake angle that is much higher than previously possible with the convention landing gear designs. A variant of this embodiment is a 3 wheel option.

Thus, the subject matter embodied by FIG. 9 may be described in more general terms as being an aircraft wing landing gear assembly comprising a raked landing gear bracket, preferably a modular landing gear bracket, extending from a hinge portion to a point, at which one or more levers are mounted for carrying one or more wheels, and a link assembly including a shock absorber (optionally arranged when the wheels are deployed so that the shock absorber axis is at an angle that is greater than 8 degrees to the vertical) which, in use, transmits at least some of the ground loads from at least one of the levers into the bracket. There are various preferred features relating to this generalised subject matter which will now be described. The landing gear bracket may have a hinge portion, a first mounting point, a second mounting point, and a third mounting point in a manner similar to that described above in relation to the general subject matter embodied by FIG. 7. There may be a first lever having a first end which is rotatably mounted to the bracket at the first mounting point and a second end, positioned forward of the first end, for receiving a first aircraft wheel in a position outboard of the first lever; and a second lever having a first end which is rotatably mounted to the bracket at a mounting point (which may be the same as the first mounting point or which may be displaced therefrom) and a second end, positioned rearward of the first end, for receiving a second aircraft wheel. One or both of the first and second levers may carry two wheels. The bracket may be raked in that, in use, when the aircraft is static and on the ground the first mounting point is located aft of the third mounting point. Alternatively, or additionally, the bracket may be raked such that, in use, when the aircraft is static and on the ground the rake angle is eight degrees or higher (e.g. greater than ten degrees). The rake angle may be self-evident in the geometry of the bracket. If not, or alternatively, the rake angle may be defined by the angle to the vertical defined by the notional line extending from the first mounting point (or if there are multiple levers carrying wheels, the mean average position of their mounting points on the bracket) to the third mounting point (and/or if there are three of more mounting points at the hinge portion, the rearmost of those hinge portion mounting points). The shock absorber of the link assembly may be the largest (or equal largest) of the shock absorbers associated with the landing gear concerned.

FIG. 10 shows a variation of the embodiment shown in FIGS. 1 and 2. Like reference numerals are used for like parts, but starting with a “7” (adding 7000 to the numbers used in FIGS. 1 and 2). The main differences will now be described. The bracket 7014 has a shorter (in the longitudinal direction) hinge portion 7018. The bracket 7014 has, at its upper end as shown in FIG. 10) only two mounting points for mounting of the bracket 7014 to the aircraft structure 7012 and a single mounting point 7020 (the “first mounting point”) at its lower end. Thus, the second mounting point 7024 is at the front of the hinge portion 7018 and the third mounting point 7026 is at the rear of the hinge portion. The overall shape of the bracket is less triangular than the FIG. 1 embodiment, because the upper part of the bracket of FIG. 10 is shorter (in the longitudinal direction) without being very differently shaped from the bracket of FIG. 1 at its lower end.

FIG. 11 shows a different variation of the embodiment shown in FIGS. 1 and 2. Like reference numerals are used for like parts, but starting with an “8” (adding 8000 to the numbers used in FIGS. 1 and 2). The main differences will now be described. The hinge portion 8018 of the bracket 8014 is provided by two spaced apart tubular sections 8019, rather than a single tube as shown in FIG. 2, each tubular section 8019 being integrally formed as part of the bracket 8014. The bracket 8014 has, at its upper end as shown in FIG. 11) only two mounting points for mounting of the bracket 8014 to the aircraft structure 8012 and a single mounting point 8020 (the “first mounting point”) at its lower end. Thus, the second mounting point 8024 is at the front of the hinge portion 8018 and the third mounting point 8026 is at the rear of the hinge portion. It will be seen that the second and third mounting points 8024, 8026 are further apart in FIG. 11 than the corresponding points in FIG. 10.

It will be seen that the collection of the above-described embodiments, modifications thereof and similar non-illustrated embodiments, utilise a common design principle that not only deviates from the conventional structure and configuration of aircraft landing gear designs but also provides a common platform facilitating a method of designing and manufacturing a new landing gear making use of a modular design system. FIG. 10 shows a method (illustrated by flowchart 500) of manufacturing a landing gear assembly utilising such a design method. There is a step (box 501) of designing a first aircraft landing gear assembly for a first aircraft, the first aircraft having a fuselage of a first length and having a first MTOW. There is a step (box 502) of designing a second aircraft landing gear assembly for a second aircraft, the second aircraft having a fuselage of a second longer length and having a second higher MTOW. Step 501 may be conducted before, after, or in parallel with step 502 or overlap in part with step 502. The first aircraft landing gear assembly may for example be either a two-wheel tandem landing gear assembly or a two-wheel diablo landing gear assembly. The first aircraft landing gear assembly comprises a load-bearing frame (for example, a modular bracket as described herein) moveable between a deployed position and a stowed position. In the deployed position, the load-bearing frame may support the majority (e.g. 75% or substantially all) of the landing gear loads when the aircraft is stationary on the ground. The load-bearing frame has features and/or mass that is/are redundant for the purpose of operation of the first aircraft (e.g. redundant in the sense that their absence would not affect the valid certification of the aircraft for commercial operation). The second aircraft landing gear assembly comprises a similar (or identical) load-bearing frame also moveable between a deployed position and a stowed position. The steps 501, 502 are carried out such that the features or mass of the load-bearing frame of the first aircraft landing gear assembly that are redundant for the purpose of operation of the first aircraft are used as features or mass of the load-bearing frame of the second aircraft landing gear assembly that are utilised (and/or necessary) for the purpose of operation of the second aircraft (for example, necessary for effective and efficient operation of the second aircraft and/or necessary for certification or safety purposes). For example, the load-bearing frame may comprise redundant structure, which is surplus to requirements for operation of the aircraft on which the aircraft landing gear assembly is to be used, the redundant structure comprising one or more of an additional mounting point (e.g. for a linkage assembly as described above) and additional mass for transmitting loads. It will be understood that the load-bearing frame (or bracket) has redundant features that are redundant in a sense other than providing redundancy solely as a structural failsafe. There then follows a step (box 503) of making at least one of the first and second aircraft landing gear assemblies. Optionally, there is a step (box 504) of making the other of the first and second aircraft landing gear assemblies (possibly before, after, during and/or overlapping with step 503). It may be that the second aircraft landing gear assembly has a different topology/geometry of the wheel—frame arrangement. For example, it may be that the first aircraft landing gear assembly is a two-wheel tandem landing gear assembly and the second aircraft landing gear assembly is a two-wheel diablo landing gear assembly. Alternatively, it may be that the first aircraft landing gear assembly is a two-wheel diablo landing gear assembly and the second aircraft landing gear assembly is a two-wheel tandem landing gear assembly. As a further alternative, it may be that the second aircraft landing gear assembly has three or more wheels. There are various preferred features relating to this generalised subject matter which will now be described. The landing gear load-bearing frame may have a hinge portion, a first mounting point, a second mounting point, and/or a third mounting point in a manner similar to that described above in relation to the general subject matter embodied by FIG. 7. The landing gear may have features described with reference to the any of the previously described embodiments. It may be that one of the first and second aircraft landing gear assemblies is a design modification of the other. A design modification may be considered as a design which is based on the earlier design and uses the earlier design as the principal starting point for the new design (being a design modification). It may also be the case that each of the above mentioned first and second aircraft landing gear assemblies is a design modification in that both utilise a common generic design model. The common generic design model may be common/generic in the sense that the loading of the landing gear (principal load paths) are the same, at least for certain parts of the common design. The load-bearing frame/bracket may be the same shape and/or geometry and/or perform the same overall function. The common generic design model may be common/generic in the sense that embodiments of the common generic design model would be considered equivalent under the concept of the doctrine of equivalent under US patent law. Having a common generic design model when designing a new landing gear assembly may significantly speed up and simplify the design and then subsequent manufacture of the landing gear assembly such that even if a version of a new landing gear assembly designed with the common generic design model is slightly heavier than it might otherwise need to be, that is a price worth paying in view of the efficiencies gained elsewhere.

Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described.

In some embodiments, one or each of the first and second spring elements (e.g. parts 131, 132) may comprise a composite spring. By composite spring, it is meant a spring made from a combination of materials, such as metal and carbon. In some other embodiments, one or each of the first and second spring elements may be made from a single material, such as a single metal or metal alloy. In some embodiments, the first spring element could comprise a bell crank, with the first and second end portions forming the arms of the bell crank.

In other embodiments, the second spring element may be mounted or attached to the bracket in a non-pivotal manner For example, the second spring element may be clamped in position relative to the bracket.

In some embodiments, the second stop may be omitted. In those embodiments, rotation of the end portion of the first spring element about the mounting point (e.g. labelled 28) during removal or reduction of that load may be controlled or limited by the second spring element.

The hinge portion of the bracket may comprise further mounting points which, in use, transfer loads into the aircraft structure (e.g. wing or fuselage).

The landing gear of the above embodiments, may be a main landing gear which is body-mounted. In other embodiments, the landing gear may be a main landing gear that is wing-mounted. In a further variation, an aircraft may comprise two or more main landing gear that are each according to different embodiments of the present invention. The landing gear of the above embodiments, may be a nose landing gear.

The aircraft in which the landing gear is mounted may be different from that shown in FIG. 3.

The hinge portion of the landing gear may have only two attachment points/mounting points for hinging the landing gear relative to the aircraft. Each attachment point may be associated with a respective pintle.

When designing a bracket for use on a lighter aircraft and a heavier aircraft, one could choose to optimise the weight of the bracket for the lower weight variant, with the overall shape and geometry of mounting points being the same for the heavyweight variant, but with greater mass. This could lead to one-way interchangeability (changing a lightweight bracket for a heavyweight bracket would be permitted on a lower weight variant aircraft, but the lightweight bracket would not be permitted for use on the heavyweight variant aircraft). This could have some advantage for spares holding (e.g. it would be sufficient to stock only the heavyweight bracket as a spare).

Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments. The term ‘or’ shall be interpreted as ‘and/or’ unless the context requires otherwise.

Claims

1. A modular aircraft landing gear assembly, wherein the modular aircraft landing gear assembly comprises:

a modular landing gear bracket extending from a hinge portion to a first mounting point, the hinge portion being configured for mounting the bracket for rotation relative to a landing gear bay, and the first mounting point being for receiving a ground load from one or more wheels, in use, the modular landing gear bracket including a second mounting point at a fore location of the hinge portion and a third mounting point at an aft location of the hinge portion, the bracket being configured so that the ground load received at the first mounting point is, in use, transferred into aircraft structure via the second mounting point and the third mounting point,

a lever having a first end which is rotatably mounted to the bracket at the first mounting point and a second end for receiving a first aircraft wheel,

structure for receiving a second aircraft wheel,

a linkage assembly, the linkage assembly in use transmitting at least some of the ground load via at least one of a spring and a shock absorber,

wherein the modular landing gear bracket comprises redundant structure, which is surplus to requirements for operation of the aircraft on which the aircraft landing gear assembly is to be used, the redundant structure comprising one or more of an additional mounting point and additional mass for transmitting loads.

2. A modular aircraft landing gear assembly according to claim 1, wherein the modular aircraft landing gear assembly is configured for a two-wheel configuration, and wherein the redundant structure facilitates reconfiguring the modular aircraft landing gear assembly for use with more wheels.

3. A modular aircraft landing gear assembly according to claim 1, wherein

the structure for receiving a second aircraft wheel includes a second lever, which has a first end which is rotatably mounted to the bracket and a second end for receiving the second aircraft wheel, and

wherein one of the first and second levers is positioned behind the other in the fore-aft direction.

4. A modular aircraft landing gear assembly according to claim 3, wherein

the aircraft wheel of one of the first and second levers is, in use with the aircraft on the ground, located to one side in an outboard direction of the mid-plane of the bracket, and

the other of the first and second levers is configured to receive the second aircraft wheel so that it is either positioned in-line with the first wheel or located to one side in an inboard direction of the mid-plane of the bracket.

5. A modular aircraft landing gear assembly according to claim 3, wherein

the redundant structure of the bracket is provided to enable the bracket to carry three wheels, two being arranged in diablo configuration and one being arranged either forward of or behind the two wheels.

6. A modular aircraft landing gear assembly according to claim 1, the modular aircraft landing gear assembly further including a balance arm rotatably mounted on the bracket via a middle pivot point, the arm having a fore end pivot point connected to the first lever via one or more link members which transmit loads received from the first lever, the arm having an aft end pivot point connected to the second lever via one or more link members which transmit loads received from the second lever.

7. A modular aircraft landing gear assembly according to claim 6, wherein the middle pivot point of the balance arm is offset from the position midway between the fore end pivot point and the aft end pivot point.

8. A modular aircraft landing gear assembly according to claim 1, further including a first shock absorber which transmits loads from the first lever.

9. A modular aircraft landing gear assembly according to claim 8, further including a second shock absorber which transmits loads from the second lever.

10. A modular aircraft landing gear assembly according to claim 9, wherein one of the first and second shock absorbers is a low pressure shock absorber and the other of the first and second shock absorbers is a high pressure shock absorber.

11. A modular aircraft landing gear assembly according to claim 1, wherein the bracket is raked such that, in use, when the aircraft is static and on the ground the first mounting point is located aft of the third mounting point.

12. A modular aircraft landing gear assembly according to claim 1, wherein the linkage assembly comprises a loading point which is movable relative to the hinge portion of the bracket, the loading point in use receiving ground load from the first lever.

13. A modular aircraft landing gear assembly according to claim 1, wherein the linkage assembly comprises a spring system that is configured to apply a resilient biasing force acting against the ground loads so that, during application of an increasing load, the spring rate of the spring system changes in dependence on the load being transmitted.

14. A modular aircraft landing gear assembly according to claim 1, wherein

the linkage assembly is pivotally mounted via a fourth mounting point of the bracket, and

the modular landing gear bracket includes a fifth mounting point for the mounting of a further linkage assembly, to be positioned either fore or aft of the linkage assembly pivotally mounted via the fourth mounting point.

15. (canceled)

16. (canceled)

17. (canceled)

18. A method of manufacturing a landing gear assembly, wherein the method includes

designing both (a) a first aircraft landing gear assembly for a first aircraft, the first aircraft having a fuselage of a first length and having a first MTOW and (b) a second aircraft landing gear assembly for a second aircraft, the second aircraft having a fuselage of a second longer length and/or having a second higher MTOW,

the first aircraft landing gear assembly comprising a load-bearing frame moveable between a deployed position in which it supports the majority of the landing gear loads when the aircraft is stationary on the ground, and a stowed position,

the second aircraft landing gear assembly comprising a load-bearing frame moveable between a deployed position in which it supports the majority of the landing gear loads when the aircraft is stationary on the ground, and a stowed position, and

then making at least one of the first and second aircraft landing gear assemblies,

and wherein

(i) the load-bearing frame has features and/or mass that is/are redundant for the purpose of operation of the first aircraft, and the features or mass of the load-bearing frame of the first aircraft landing gear assembly that are redundant for the purpose of operation of the first aircraft are used as features or mass of the load-bearing frame of the second aircraft landing gear assembly that are utilised for the purpose of operation of the second aircraft,

and/or

(ii) the load-bearing frame of the second aircraft has the same geometry as the load-bearing frame of the first aircraft but is scaled up and/or the load-bearing frame of the second aircraft has the same shape as the load-bearing frame of the first aircraft but is strengthened by use of extra mass in the structure of the load-bearing frame.

19. (canceled)

20. An aircraft landing gear assembly comprising:

a modular landing gear bracket extending from a hinge portion to a first mounting point, the hinge portion being configured for mounting the bracket for rotation relative to a landing gear bay, and the first mounting point being for receiving a ground load from one or more wheels, in use,

the bracket including a second mounting point at a fore location of the hinge portion and a third mounting point at an aft location of the hinge portion, the bracket being configured so that the ground load received at the first mounting point is, in use, transferred into aircraft structure via the second mounting point and the third mounting point,

a first lever having a first end which is rotatably mounted to the bracket at the first mounting point and a second end, positioned forward of the first end, for receiving a first aircraft wheel, and

a second lever having a first end which is rotatably mounted to the bracket at the first mounting point and a second end, positioned rearward of the first end, for receiving a second aircraft wheel.

21. An aircraft landing gear assembly according to claim 20,

wherein

one of the first lever and the second lever is configured to carry two wheels in a diablo configuration, and

the other of the first lever and the second lever is configured to carry a single wheel.

22. An aircraft landing gear assembly according to claim 20, further comprising

a balance arm rotatably mounted on the bracket via a middle pivot point, the arm having a fore end pivot point connected to the first lever via one or more link members which transmit loads received from the first lever, the arm having an aft end pivot point connected to the second lever via one or more link members which transmit loads received from the second lever, and

the middle pivot point of the balance arm being offset from the position midway between the fore end pivot point and the aft end pivot point.

23. An aircraft landing gear assembly according to claim 20, further comprising

a balance arm rotatably mounted on the bracket via a middle pivot point, the arm having a fore end pivot point connected to the first lever via one or more link members include a first shock absorber,

the arm having an aft end pivot point connected to the second lever via one or more members comprising a second shock absorber which transmit loads received from the second lever,

one of the first and second shock absorbers being a low pressure shock absorber and the other of the first and second shock absorbers being a high pressure shock absorber.

24. An aircraft wing landing gear assembly according to claim 20, further comprising

a linkage assembly, the linkage assembly in use transmitting at least some of the ground load via at least one of a spring and a shock absorber,

wherein

the bracket is raked such that, in use, when the aircraft is static and on the ground the first mounting point is located aft of the third mounting point and/or defines a rake angle of eight degrees or higher.

25. An aircraft wing landing gear assembly according to claim 24, wherein the bracket is raked such that, in use, when the aircraft is static and on the ground the rake angle defined by the notional line extending from the first mounting point to the third mounting point is eight degrees or higher.

26. An aircraft wing landing gear assembly according to claim 24, wherein the second lever is rotatably mounted to the bracket at a further mounting point and the bracket is raked such that, in use, when the aircraft is static and on the ground the rake angle defined by the notional line extending from the midway point between the mounting points on the bracket of the first and second levers to the third mounting point is eight degrees or higher.

27. An aircraft landing gear assembly according to claim 20, wherein one of the first and second wheels being in a position located to one side in an outboard direction of the mid-plane of the bracket and the other of the first and second wheels either being in a position located to the one side in an inboard direction of the mid-plane of the bracket or in-line with the first wheel.