GB2572161A

GB2572161A - An aircraft landing gear

Info

Publication number: GB2572161A
Application number: GB1804442.0A
Authority: GB
Inventors: Siegel Romain; Didey Arnaud
Original assignee: Airbus Operations Ltd
Current assignee: Airbus Operations Ltd
Priority date: 2018-03-20
Filing date: 2018-03-20
Publication date: 2019-09-25
Anticipated expiration: 2038-03-20
Also published as: GB2572161B; GB201804442D0

Abstract

The invention provides an aircraft landing gear 102 comprising a landing gear leg 104, with an upper end for mounting to an aircraft, a bogie frame 107 pivotally mounted towards a lower end of the landing gear leg, and at least one wheel axle 108, 109 mounted on the bogie frame, each carrying one or more wheels 111, 112, 113, 114, mounted for rotation about the wheel axle, wherein one or more wheels 112 of the landing gear is provided with a drive system 131 for driving the wheel to rotate about its axle, wherein one or more wheels 111, 113, 114 of the landing gear is provided with a brake system 120 for applying a braking torque to retard rotation of the wheel about its axle, and wherein at least one wheel 111, 112, 113, 114 of the landing gear is provided with only one of a drive system and a brake system. The wheel or wheels comprising a brake system 120 may be larger than the wheel or wheels comprising a drive system 131.

Description

[0002] The present invention concerns aircraft landing gear. More particularly, but not exclusively, this invention concerns an aircraft landing gear, the landing gear comprising a landing gear leg, with an upper end for mounting to an aircraft, a bogie frame pivotally mounted towards a lower end of the landing gear leg, and at least one wheel axle mounted on the bogie frame, the one or more wheel axles each carrying one or more wheels, mounted for rotation about the wheel axle, wherein one or more wheels of the landing gear is provided with a drive system for driving the wheel to rotate about its axle and wherein one or more wheels of the landing gear is provided with a brake system for applying a braking torque to retard rotation of the wheel about its axle. The invention also concerns an aircraft.

[0003] US 2015/301531 describes a landing gear arrangement of an aircraft with two bogies; one each side of a longitudinal axis of the aircraft. Each bogie has an actuator arranged to brake and/or drive one or more wheels. The bogies may have 4 wheels or 6 wheels. The actuator is not shown however, it is described as being capable of acting on one or more of the wheels to accelerate or decelerate the bogies. The actuator may be a brake actuator which applies a clamping force to a stack of carbon brake disks (stators and rotors) to transfer a braking torque to the one or more wheels. Alternatively, or in addition, the actuator may comprise a motor operable to apply a driving force to the one or more wheels.

[0004] There is limited flexibility in relation to the bogie configuration in this arrangement. For example, the actuator described can either provide a brake facility, a drive facility or both. And it can provide that (or those) facilities to one or more wheels. However, there is no disclosure of having different facilities provided to different wheels in the bogie. This means that the configuration of the bogie is limited and may not be able to be configured to ideally cope with a required or desired braking or driving demand.

[0005] The present invention seeks to mitigate the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved aircraft landing gear and aircraft.

SUMMARY OF THE INVENTION [0006] The present invention provides, according to a first aspect, an aircraft landing gear, the landing gear comprising a landing gear leg, with an upper end for mounting to an aircraft, a bogie frame pivotally mounted towards a lower end of the landing gear leg, and at least one wheel axle mounted on the bogie frame, the one or more wheel axles each carrying one or more wheels, mounted for rotation about the wheel axle, wherein one or more wheels of the landing gear is provided with a drive system for driving the wheel to rotate about its axle, wherein one or more wheels of the landing gear is provided with a brake system for applying a braking torque to retard rotation of the wheel about its axle, and wherein at least one wheel of the landing gear is provided with only one of a drive system and a brake system.

[0007] This arrangement allows for a flexible landing gear configuration, for example where there may be different wheels of the landing gear provided with different brake/drive functionality. This allows the landing gear to be configured to ideally cope with a required or desired braking or driving demand.

[0008] For example, one wheel may be used solely for driving, where the other wheels (for example 3 wheels in a 4 wheel landing gear) may be used solely for braking.

[0009] For example, two wheels may be used solely for driving, where the other wheels (for example 2 wheels in a 4 wheel landing gear) may be used solely for braking.

[0010] For example, two wheels may be used solely for braking, where the other wheels (for example 2 wheels in a 4 wheel landing gear) may be used braking and driving.

[0011] Importantly, in all the claimed embodiments, the landing gear is able to provide a braking function and a driving function amongst its wheels. However, there is at least one wheel that only provides one of these functions.

[0012] This is differentiated from US 2015/301531, where the actuator for a landing gear is either a braking actuator, a driving actuator or both. It can be used to brake and/or drive one or more wheels. However, the remaining wheels would not be driven or braked. [0013] For example, in US 2015/301531, there may be an arrangement where the actuator is both a brake and a drive actuator, and it is used on, say, first, second and third wheels of four wheels. In this arrangement, the fourth wheel would not be braked or driven. Hence, there is no wheel of the landing gear that is provided with only one of a drive system and a brake system, as required by the invention.

[0014] As another example, there may be an arrangement in US 2015/301531 where the actuator is a brake actuator, and it is used on, say, first and second wheels of four wheels. In this arrangement, the third and fourth wheel would not be braked or driven. Hence, there is no wheel of the landing gear that is provided with a drive system for driving the wheel to rotate about its axle, as required by the invention.

[0015] As a final example, there may be an arrangement in US 2015/301531 where the actuator is a drive actuator, and it is used on, say, first and second wheels of four wheels. In this arrangement, the third and fourth wheel would not be braked or driven. Hence, there is no wheel of the landing gear that is provided with a brake system for applying a braking torque to retard rotation of the wheel about its axle, as required by the invention.

[0016] It is noted that the invention relates to a bogie landing gear with a bogie frame pivotally mounted towards a lower end of the landing gear leg, and at least one wheel axle mounted on the bogie frame. In other words, the wheel axle(s) is able to pivot in relation to the landing gear leg. For example, the main landing gear of an A3 80 is a bogie landing gear.

[0017] The alternative to a bogie landing gear is a diablo landing gear, where the one or more wheel axles (generally only one wheel axle) is not able to pivot in relation to the landing gear leg.

[0018] Preferably, all the wheels of the landing gear are provided with at least one of a brake system and a drive system. This helps to provide adequate braking and/or driving function for the landing gear. Alternatively, there may be one or more wheels that is not provided with either a driving system or a braking system. The brake system may comprise a heat sink arrangement.

[0019] Preferably, at least one wheel is provided with only a drive system. In other words, this at least one wheel is not provided with a brake system. This means that the one or more wheels can be dedicated to driving the aircraft and provide adequate driving functionality for the landing gear. The one or more wheels can be designed and configured (e.g. weight and space optimisation) for efficient drive functionality without having to be compromised by also providing a brake functionality. Importantly, it is noted that often, a wheel providing brake functionality requires the brake system to be provided within the hub of the wheel. This prevents that space from being used for a drive system, for example. This would not be the case for a wheel that is provided with only a drive system and so that drive system may be provided, at least partially, within the hub of the wheel.

[0020] Preferably, at least one wheel is provided with only a brake system. In other words, this at least one wheel is not provided with a drive system. This means that the one or more wheels can be dedicated to braking the aircraft and provide adequate braking functionality for the landing gear. The one or more wheels can be designed and configured (e.g. weight and space optimisation) for efficient brake functionality without having to be compromised by also providing a drive functionality. Importantly, it is noted that often, a wheel providing drive functionality requires the drive system to be provided within the hub of the wheel. This prevents that space from being used for a brake system, for example. This would not be the case for a wheel that is provided with only a brake system and so that brake system may be provided, at least partially, within the hub of the wheel.

[0021] Preferably, at least two wheels of the landing gear are provided with only one of a drive system and a brake system. This means that these more than one wheels can be dedicated to their sole (brake or drive) function and can be designed for efficiency of providing that function.

[0022] More preferably, all of the wheels of the landing gear are provided with only one of a drive system and a brake system. This means that all of the wheels of the landing gear can be dedicated to their sole (brake or drive) function and can be designed for efficiency of providing that function.

[0023] Preferably, a first wheel of the landing gear is provided with only a drive system and a second wheel of the landing gear is provided with only a brake system. This means that the first wheel of the landing gear can be dedicated to its sole (drive) function and can be designed for efficiency of providing that function. At the same time, the second wheel of the landing gear can be dedicated to its sole (brake) function and can be designed for efficiency of providing that function.

[0024] Preferably, the number of wheels of the landing gear provided with a brake system is the same or exceeds the number of wheels of the landing gear provided with a drive system. It is noted that often, the required or desired brake and drive functionality requires a larger number of wheels to be used for braking than are used for driving.

[0025] Preferably, the number of wheels of the landing gear provided with only a brake system is the same or exceeds the number of wheels of the landing gear provided with only a drive system. It is noted that often, the required or desired brake and drive functionality requires a larger number of wheels to be used only for braking than are used only for driving.

[0026] Preferably, one or more wheels of the landing gear that is provided with a brake system has a size that exceeds the size of one or more wheels of the landing gear that is provided with a drive system. This enables the one or more wheels that are provided with a brake system (i.e. that provide brake functionality) are able to provide an increased braking capacity/power due to the wheel being larger. The one or more wheels provided with a brake system may have a larger diameter and/or a larger width.

[0027] More preferably, one or more wheels of the landing gear that is provided with only a brake system has a size that exceeds the size of one or more wheels of the landing gear that is provided with only a drive system. This enables the one or more wheels that are provided with only a brake system (i.e. that only provide brake functionality) are able to provide an increased braking capacity/power due to the wheel being larger. The one or more wheels provided with only a brake system may have a larger diameter and/or a larger width.

[0028] Preferably, the one or more wheels of the landing gear that is provided with a brake system is located aft of the landing gear leg, the rolling direction of the wheels defining the fore/aft direction. This enables the larger wheels to be at the back of the landing gear, which might improve stability. In addition, the rear wheels may land first (prior to the front wheels), especially if they are larger, and this allows them to be used to brake the aircraft first. Alternatively, the one or more wheels of the landing gear that is provided with a brake system is located fore of the landing gear leg, the rolling direction of the wheels defining the fore/aft direction. This enables the larger wheels to be at the front of the landing gear.

[0029] Preferably, one or more wheels of the landing gear is provided with both a drive system and a brake system. This enables one or more of the landing gear wheels to be used to provide both functions. Hence, whilst the design of this (or these) wheel(s) may not have been optimised for each function on its own, it may be designed to still provide both functions efficiently and allowing the landing gear, as a whole, to provide the required or desired capacity of both functions.

[0030] One or more drive systems of the landing gear may comprise a direct or geared drive mechanism. A geared drive mechanism may be more compact.

[0031] More preferably, one or more drive systems of the landing gear comprises a drive mechanism (at least partially) mounted within a hub of its wheel. This provides a compact arrangement that may not interfere with the retraction and/or stowage of the landing gear.

[0032] Alternatively, one or more drive systems of the landing gear comprises a drive mechanism mounted (at least partially) out of the hub of its wheel. This may enable easier inspection of the drive system. The drive mechanism may be driveable by a motor, the motor also being arranged to drive at least one other drive mechanism of the landing gear, such that the motor is arranged to drive rotation of at least two wheels of the landing gear. This allows a single motor to drive two wheels and so reduce the overall mass and/or volume of the drive systems on the landing gear.

[0033] More preferably, the at least two wheels are located on the same side of the landing gear leg as each other, either fore or aft of the landing gear leg, or left or right of the landing gear leg, the rolling direction of the wheels defining the fore/aft direction. This provides for efficient connection to the motor.

[0034] Preferably, one or more brake systems of the aircraft landing gear is mounted (at least partially) mounted within a hub of its wheel. This provides a compact arrangement that may not interfere with the retraction and/or stowage of the landing gear.

[0035] Preferably, the one or more wheels that is provided with both a drive system and a brake system has a drive system that comprises a drive mechanism mounted (at least partially) out of the hub of its wheel, the drive mechanism being driveable by a motor, the motor also being arranged to drive at least one other drive mechanism of the landing gear, such that the motor is arranged to drive rotation of at least two wheels of the landing gear, and a brake system that is mounted (at least partially) within a hub of its wheel.

[0036] More preferably, the at least two wheels are located on the same side of the landing gear leg as each other, either fore or aft of the landing gear leg, or left or right of the landing gear leg, the rolling direction of the wheels defining the fore/aft direction. This provides for efficient connection to the motor.

[0037] Even more preferably, the at least two wheels are located aft of the landing gear leg. This allows the drive systems to be more protected from the environment during use.

[0038] One or more drive systems of the aircraft landing gear may be electrically or hydraulically actuated.

[0039] One or more brake systems of the aircraft landing gear may be electrically or hydraulically actuated.

[0040] Preferably, one or more drive systems of the aircraft landing gear is capable of driving its wheel in a forwards or a backwards direction. In other words, the drive system may be able to drive the aircraft forwards, or in reverse, or both.

- 8 [0041] Preferably, one or more brake systems of the aircraft landing gear is capable of retarding forwards or backwards rotation of its wheel. In other words, the brake system may be able to retard the aircraft when it is moving forwards, or in reverse, or both.

[0042] The aircraft landing gear may be a main landing gear or a nose landing gear. [0043] Preferably, the aircraft landing gear is a main landing gear.

[0044] Preferably, the landing gear has (at least) two wheel axles with (at least) two wheels mounted on each axle, such that the landing gear has (at least) four wheels.

[0045] More preferably, the bogie frame extends in a fore/aft direction, and the (at least) two wheel axles extend sideways from the bogie frame, one being a front axle, fore of the landing gear leg, and one being a rear axle, aft of the landing gear leg, the rolling direction of the wheel defining the fore/aft direction.

[0046] Preferably, the bogie frame extends substantially perpendicular to the landing gear leg. Preferably, the one or more wheel axles extend perpendicular to the bogie frame. Preferably, the one or more wheel axles extend perpendicular to the landing gear leg.

[0047] According to a second aspect of the invention there is also provided an aircraft comprising the landing gear as described above.

[0048] More preferably, the aircraft comprises two landing gears as described above, wherein the two landing gears are mounted on the aircraft in an aligned manner either side of a longitudinal axis of the aircraft, and wherein the arrangement of the provision of drive and/or brake systems for the wheels of the two landing gears is symmetrical about the longitudinal axis of the aircraft.

[0049] 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 [0050] Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which:

[0051] Figure 1 shows a plan cutaway view of two landing gears according to a first embodiment of the invention;

[0052] Figure 2 shows a plan cutaway view of two landing gears according to a second embodiment of the invention;

[0053] Figure 3 shows a plan cutaway view of two landing gears according to a third embodiment of the invention;

[0054] Figure 4 shows a side view of one of the landing gears of Figure 3;

[0055] Figure 5 shows a plan cutaway view of two landing gears according to a fourth embodiment of the invention;

[0056] Figure 6 shows a plan cutaway view of two landing gears according to a fifth embodiment of the invention; and [0057] Figure 7 shows a schematic side view of an aircraft including a landing gear according to any of the above embodiments.

DETAILED DESCRIPTION [0058] Figure 1 shows a plan cutaway view of two main landing gears according to a first embodiment of the invention. There is a left main landing gear 102 and a right main landing gear 103, both arranged symmetrically about a longitudinal axis of an aircraft upon which they are mounted. A forwards arrow 101 is shown, on that longitudinal axis, indicating the forwards direction of the aircraft.

[0059] The left main landing gear 102 will now be described.

[0060] The left main landing gear 102 comprises a landing gear leg 104, located centrally in the landing gear. This left main landing gear leg 104 is mounted to an underside of a left hand side of an undercarriage on an aircraft fuselage. It should be noted that the right main landing gear 103 is similar to the left main landing gear, with the various different wheel configurations of the right main landing gear being a mirror image (about the longitudinal axis of the aircraft) of the left main landing gear 102. The right main landing gear leg is mounted to the underside of a right hand side of the undercarriage on the aircraft fuselage.

[0061] The left main landing gear 102 comprises a bogie frame 107 pivotally mounted to a lower end of the leg 104. The leg 104 extends substantially vertically downwards (into the page as shown in Figure 1). The bogie frame 107 extends fore and aft of the leg 104 (up and down the page as shown in Figure 1). Mounted towards a front end of the bogie frame 107 is a front axle 108 extending perpendicular to the bogie frame (left and right across the page as shown in Figure 1). Mounted towards a rear end of the bogie frame 107 is a rear axle 109 extending perpendicular to the bogie frame (left and right across the page as shown in Figure 1). The bogie frame 107 is pivotally mounted to the leg 104 so as to pivot within the plane of the frame in the view of Figure 1. In other words, so that the front and rear axles 108, 109 move up and down or “pitch and dip” (i.e. in and out of the page as shown in Figure 1). The bogie frame 107 may be provided with a bogie pitch trimmer/actuator (not shown) to orientate the bogie frame accordingly to the pitch ratio of the aircraft. Alternatively, the bogie frame 107 may not have an actuator to control its pitch and it may simply pitch or dip depending on the aircraft geometry and centre of gravity when in the air and on the ground.

[0062] Each axle carries two wheels; one wheel on a left side of the axle and one wheel on a right side of the axle. Therefore, the landing gear 102 has 4 wheels. These are: a front left wheel 111, a front right wheel 112, a rear left wheel 113 and a rear right wheel 114. Each wheel comprises a hub 115 and a tyre 116 surrounding the hub 115 (shown on wheel 111).

[0063] Each wheel is provided with a certain brake or drive functionality, as follows:

[0064] The front left wheel 111, rear left wheel 113 and rear right wheel 114 are each provided with only a brake system 120 (shown on rear left wheel 113). The brake systems 120 each comprise a brake actuator 121 (mounted outside the wheel hub) and a brake mechanism 122 (mounted within the wheel hub). The brake mechanism comprises a stack of carbon brake disks (stators and rotors) to transfer a braking torque to the one or more wheels. The rotors are attached to the wheel and the stators are attached to the wheel axle. When it is wished to brake the aircraft, the brake disks are compressed together to create friction and retard the wheel rotating about the axle. The number of stators/rotors depends on the space constraints and the energy needed to stop the aircraft. [0065] The front right wheel 112 is provided with only a drive system 130. The drive system is a geared drive system 131 comprising a gear 133 (mounted within the wheel hub) and a motor 132 to drive the gear 133 (the motor being mounted partially in and partially out of the wheel hub). The drive system 131 overall is mounted substantially within the wheel hub 115. The drive system 131 may be similar to the geared drive system disclosed in US-2016-0039519-Al.

[0066] This arrangement of both main landing gears provides six wheels dedicated to just braking and two wheels dedicated to just driving. This provides a large amount of braking redundancy/capacity.

[0067] Figure 2 shows a plan cutaway view of two main landing gears according to a second embodiment of the invention. The second embodiment is similar to the first embodiment and the same reference numerals are used to refer to like elements, with the replacement of a preceding “1” with a “2”. Only the differences from the first embodiment will now be described.

[0068] Each wheel is provided with a certain brake or drive functionality, as follows: [0069] The front right wheel 212 and rear right wheel 214 are each provided with only a brake system 220 (shown on front right wheel 212).

[0070] The front left wheel 211 and rear right wheel 213 are each provided with only a drive system 230. The drive system 230 is a direct drive system 234. The drive system 234 is mounted within the wheel hub 215. Direct drive systems, such as 234, are well known in the art. For example, the direct drive system 234 may comprises a motor directly connected to the wheel hub 215.

[0071] This arrangement of both main landing gears provides four wheels dedicated to just braking and four wheel dedicated to just driving. This provides a large amount of driving redundancy/capacity.

[0072] Figure 3 shows a plan cutaway view of two main landing gears according to a third embodiment of the invention. The third embodiment is similar to the first and second embodiments and the same reference numerals are used to refer to like elements, with the replacement of a preceding “1” or “2” with a “3”. Only the differences from the first or second embodiments will now be described.

[0073] Each wheel is provided with a certain brake or drive functionality, as follows:

[0074] The rear left wheel 313 and rear right wheel 314 are each provided with only a brake system 320.

[0075] The front left wheel 311 and front right wheel 312 are each provided with only a drive system 330. The drive system 330 is a geared drive system 331 comprising a gear 333 (mounted within the wheel hub) and a motor 332 to drive the gear 133 (the motor being mounted partially in and partially out of the wheel hub). The drive system 331 overall is mounted substantially within the wheel hub 315.

[0076] Figure 4 shows a side view of the left landing gear 302 of Figure 3. The left landing gear leg 304 comprises a upper sprung part 305 for mounting to the aircraft and a lower un-sprung part 306 that mounts the bogie frame 307. As can be seen in Figure 4, the front axle 308 is smaller than the rear axle 309. In addition, the front wheels 311 (and 312) are larger than the rear wheels 313 (and 314). The wheels 313, 314 are larger in terms of diameter and width (not shown).

[0077] This arrangement of both main landing gears provides six wheels dedicated to just braking and two wheels dedicated to just driving. This provides a large amount of braking redundancy/capacity.

[0078] Figure 5 shows a plan cutaway view of two main landing gears according to a fourth embodiment of the invention. The fourth embodiment is similar to the first, second and third embodiments and the same reference numerals are used to refer to like elements, with the replacement of a preceding “1”, “2” or “3” with a “4”. Only the differences from the first, second or third embodiments will now be described.

[0079] Each wheel is provided with a certain brake or drive functionality, as follows:

[0080] The front left wheel 411 and rear left wheel 413 are each provided with only a brake system 420.

[0081] The front right wheel 412 and rear right wheel 414 are each provided with a brake system 420. These two wheels 412, 414 are also provided with a drive system 430.

Each drive system 430 is a geared drive system 431 comprising a gear 433 (mounted so as to connect to the wheel hub and extend fore - from gear 433 a for the rear wheel 414 and aft - from gear 433b for the front wheel 412 - from the wheel hub). A shared motor 432 in line with the landing gear leg 404 is connected to both gears 433a, 433b and used to drive both gears 433a, 433b.

[0082] This arrangement of both main landing gears provides four wheels dedicated to just braking and four wheels for both braking and driving. This provides a large amount of braking redundancy/capacity as well as driving redundancy/capacity. The size of one or more wheels may be able to be reduced in such an arrangement, due to this redundancy.

[0083] Figure 6 shows a plan cutaway view of two main landing gears according to a fifth embodiment of the invention. The fifth embodiment is especially similar to the fourth embodiment and the same reference numerals are used to refer to like elements, with the replacement of a preceding “4” (or “1”,

or “3”) with a “5”

Only the differences from the fourth embodiment will now be described.

[0084] Each wheel is provided with a certain brake or drive functionality, as follows:

[0085] The front left wheel 511 and front right wheel 512 are each provided with only a brake system 520.

[0086] The rear left wheel 513 and rear right wheel 514 are each provided with a brake system 520. These two wheels 513, 514 are also provided with a drive system 530. Each drive system 530 is a geared drive system 531 comprising a gear 533 (mounted so as to connect to the wheel hub and extend right - from gear 533a for the left wheel 513 — and left - from gear 533b for the right wheel 412 - from the wheel hub). A shared motor 532 in line with the landing gear leg 504 is connected to both gears 533a, 533b and used to drive both gears 533a,b.

[0087] This arrangement of both main landing gears provides four wheels dedicated to just braking and four wheels for both braking and driving. This provides a large amount of braking redundancy/capacity as well as driving redundancy/capacity. The size of one or more wheels may be able to be reduced in such an arrangement, due to this redundancy. Having the drive systems 530 on the rear wheels allows the drive systems to be more protected from the environment during use.

[0088] Figure 7 shows a schematic side view of an aircraft 1000 including a landing gear 1002 according to any of the above embodiments.

[0089] The aircraft 1000 comprises a nose landing gear 1001 and two main landing gears (left one 1002 shown in Figure 7). The left landing gear 1002 could be any of the left landing gears 102, 202, 302, 402, 502 of the above examples or alternatives. The right landing gear (not shown) would correspond to the corresponding right landing gear 103, 203, 303, 403, 503.

[0090] The left landing gear 1002 has a landing gear leg 1021 corresponding to any of legs 104, 204, 304, 404, 504, a bogie frame 1022 corresponding to any of bogie frames 107, 207, 307, 407, 507, a front axle 1023 corresponding to any of front axles 108, 208, 308, 408, 508 and a rear axle 1024 corresponding to any of rear axles 109, 209, 309, 409, 509.

[0091] 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.

[0092] In any of the above example embodiments, where possible, a direct drive system ‘34 may be replaced with a geared drive system ‘31 and vice versa. An exception to this is the fourth and fifth embodiments where a geared drive system is necessary to be able to drive two wheels with a single motor.

[0093] In any of the above example embodiments, the number of wheels in each landing gear may be six (e.g. on three axles, each with two wheels) or any other suitable number. For example, there may be only two wheels in a tandem arrangement such as on the main landing gear of a Sukhoi SU-34. As another example, there may be three wheels.

[0094] In any of the above example embodiments, the wheel or wheels chosen to carry the different functionality can be changed. For example, taking the first embodiment, the wheel provided with only the drive system 131 could alternatively be the front left wheel, the rear left wheel or the rear right wheel. For example, taking the second embodiment, the wheels provided with only the drive system 234 could alternatively be the right wheels. For example, taking the third embodiment, the wheels provided with only the drive system 331 could alternatively be the rear wheels. In this example, the front wheels may instead be larger than the rear wheels.

[0095] In any of the above example embodiments, one or more brake systems may be electrically or hydraulically actuated.

[0096] In any of the above example embodiments, one or more drive systems may be electrically or hydraulically actuated.

[0097] In any of the above example embodiments, one or more drive systems of the aircraft landing gear is capable of driving its wheel in a forwards and/or a backwards direction.

[0098] In any of the above example embodiments, one or more brake systems of the aircraft landing gear is capable of retarding forwards and/or backwards rotation of its wheel.

[0099] The above example embodiments relate to the configuration of the main landing gear. Of course, the invention may also be applicable to a nose landing gear.

[00100] 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.

[00101] It should be noted that throughout this specification, “or” should be interpreted as “and/or”.

Claims

1. An aircraft landing gear, the landing gear comprising:

- a landing gear leg, with an upper end for mounting to an aircraft,

- a bogie frame pivotally mounted towards a lower end of the landing gear leg, and

- at least one wheel axle mounted on the bogie frame, the one or more wheel axles each carrying one or more wheels, mounted for rotation about the wheel axle, wherein one or more wheels of the landing gear is provided with a drive system for driving the wheel to rotate about its axle, wherein one or more wheels of the landing gear is provided with a brake system for applying a braking torque to retard rotation of the wheel about its axle, and wherein at least one wheel of the landing gear is provided with only one of a drive system and a brake system.

2. An aircraft landing gear according to claim 1, wherein at least one wheel is provided with only a drive system.

3. An aircraft landing gear according to claim 1 or claim 2, wherein at least one wheel is provided with only a brake system.

4. An aircraft landing gear according to any preceding claim, wherein at least two wheels of the landing gear are provided with only one of a drive system and a brake system.

5. An aircraft landing gear according to claim 4, wherein all of the wheels of the landing gear are provided with only one of a drive system and a brake system.

6. An aircraft landing gear according to any preceding claim, wherein a first wheel of the landing gear is provided with only a drive system and a second wheel of the landing gear is provided with only a brake system.

7. An aircraft landing gear according to any preceding claim, wherein the number of wheels of the landing gear provided with a brake system is the same or exceeds the number of wheels of the landing gear provided with a drive system.

8. An aircraft landing gear according to any preceding claim, wherein the number of wheels of the landing gear provided with only a brake system is the same or exceeds the number of wheels of the landing gear provided with only a drive system.

9. An aircraft landing gear according to any preceding claim, wherein one or more wheels of the landing gear that is provided with a brake system has a size that exceeds the size of one or more wheels of the landing gear that is provided with a drive system.

10. An aircraft landing gear according to claim 9, wherein one or more wheels of the landing gear that is provided with only a brake system has a size that exceeds the size of one or more wheels of the landing gear that is provided with only a drive system.

11. An aircraft landing gear according to claim 9 or claim 10, wherein the one or more wheels of the landing gear that is provided with a brake system is located aft of the landing gear leg, the rolling direction of the wheels defining the fore/aft direction.

12. An aircraft landing gear according to any preceding claim, wherein one or more wheels of the landing gear is provided with both a drive system and a brake system.

13. An aircraft landing gear according to any preceding claim, wherein one or more drive systems of the landing gear comprises a direct or geared drive mechanism.

14. An aircraft landing gear according to claim 13, wherein one or more drive systems of the landing gear comprises a drive mechanism, at least partially, mounted within a hub of its wheel.

15. An aircraft landing gear according to claim 13, wherein one or more drive systems of the landing gear comprises a drive mechanism mounted, at least partially, out of the hub of its wheel, the drive mechanism being driveable by a motor, the motor also being arranged to drive at least one other drive mechanism of the landing gear, such that the motor is arranged to drive rotation of at least two wheels of the landing gear.

16. An aircraft landing gear according to claim 15, wherein the at least two wheels are located on the same side of the landing gear leg as each other, either fore or aft of the landing gear leg, or left or right of the landing gear leg, the rolling direction of the wheels defining the fore/aft direction.

17. An aircraft landing gear according to any preceding claim, wherein one or more brake systems of the aircraft landing gear is mounted, at least partially, within a hub of its wheel.

18. An aircraft landing gear according to claim 12, wherein the one or more wheels that is provided with both a drive system and a brake system has a drive system according to claim 15 or 16 and a brake system according to claim 17.

19. An aircraft landing gear according to claim 18, wherein the at least two wheels are located on the same side of the landing gear leg as each other, either fore or aft of the landing gear leg, or left or right of the landing gear leg, the rolling direction of the wheels defining the fore/aft direction.

20. An aircraft landing gear according to any preceding claim, wherein one or more drive systems of the aircraft landing gear is electrically or hydraulically actuated.

21. An aircraft landing gear according to any preceding claim, wherein one or more brake systems of the aircraft landing gear is electrically or hydraulically actuated.

22. An aircraft landing gear according to any preceding claim, wherein one or more drive systems of the aircraft landing gear is capable of driving its wheel in a forwards or a backwards direction.

23. An aircraft landing gear according to any preceding claim, wherein one or more brake systems of the aircraft landing gear is capable of retarding forwards or backwards rotation of its wheel.

24. An aircraft landing gear according to any preceding claim, wherein the aircraft landing gear is a main landing gear or a nose landing gear.

25. An aircraft landing gear according to claim 24, wherein the aircraft landing gear is a main landing gear.

26. An aircraft landing gear according to any preceding claim, wherein the landing gear has at least two wheel axles with at least two wheels mounted on each axle, such that the landing gear has at least four wheels.

27. An aircraft landing gear according to claim 26, wherein the bogie frame extends in a fore/aft direction, and the at least two wheel axles extend sideways from the bogie frame, one being a front axle, fore of the landing gear leg, and one being a rear axle, aft of the landing gear leg, the rolling direction of the wheels defining the fore/aft direction.

28. An aircraft comprising the landing gear of any preceding claim.

29. An aircraft according to claim 28 wherein the aircraft comprises two landing gears according to any preceding claim, wherein the two landing gears are mounted on the aircraft in an aligned manner either side of a longitudinal axis of the aircraft, and

- 20 wherein the arrangement of the provision of drive and/or brake systems for the wheels of the two landing gears is symmetrical about the longitudinal axis of the aircraft.