Aircraft landing gear, suspension mechanism and aircraft

Abstract

The invention relates to an aircraft landing gear (14) having a suspension mechanism (20) with a four-bar linkage arrangement (54) comprising four links (60, 62, 64, 66) that rigidly extend between respective four pivots (70, 72, 74, 76). A lower link (64) of the four-link device (54) supports the front and rear wheels (22, 24) and is movable between an extended position and a shortened position with respect to the upper link (60). The shock absorber (56) urges the four-bar linkage device (54) toward the extended position. The length of the upper link (60) of the four-bar link arrangement (54) is adjustable. The invention also relates to a suspension mechanism and an aircraft.

Description

Field of the Invention

[0001] The present disclosure relates to the field of aircraft landing gear. The present disclosure relates in particular but not exclusively to aircraft landing gear, suspension mechanisms, and aircraft including such landing gear. Background Art

[0002] In many aircraft, the main landing gear is attached to the fuselage of the aircraft and can be stowed in a cavity in the wing. In such aircraft, the need to stow in the wing means that each main landing gear must be positioned close to its respective wing and (when stowed) must be narrow enough to fit within the available space inside the wing. However, all other things being equal, wings with a high aspect ratio (i.e., wings with a longer wingspan but a shorter chord) allow the aircraft to fly more efficiently and thus use less fuel. Wings with a high aspect ratio have less space available for accommodating the landing gear. In addition, increasing the wingspan of the aircraft moves the center of gravity of the aircraft rearward, because increasing the length of the (swept-back) wing moves more weight rearward.

[0003] Thus, there is a point where the wing and the landing gear impose conflicting constraints on the design of the aircraft - the need for the landing gear to fit within the wing when stowed and the need for the center of gravity of the aircraft to remain forward of the main landing gear may prevent the aspect ratio of the wing from reaching an ideal height. Similarly, the need to fit the landing gear into a narrow wing may mean that less than ideal landing gear (e.g., less than ideal in terms of weight, complexity, cost, ride comfort, or braking performance) must be used.

[0004] By way of illustration, one attempt to achieve an optimal balance between these conflicting constraints is to use a main landing gear in which the main leg in the form of an oleo strut is slightly swept-back. This swept-back arrangement positions the wheels of the landing gear further to the rear, which in turn means that the center of gravity of the aircraft can be further to the rear. Additionally, a swept-back landing gear can to some extent match the swept-back shape of the wing, thus allowing the landing gear to fit into a narrower space. However, if the angle of sweep of the oleo strut is too large, then its shock-absorbing performance is affected - the oleo strut is not well aligned with the direction of the weight of the aircraft, it acts as a stiffer spring, so provides a poorer ride quality, and when the weight of the aircraft changes (e.g., when passengers board), it may tend to stick and then slide significantly. Thus, there is an effective maximum angle for the oleo strut, which places a limit on the aspect ratio of the wing.

[0005] The present invention seeks to alleviate one or more of the above problems. Alternatively or additionally, the present invention seeks to provide an improved or alternative landing gear, suspension mechanism, or aircraft. Summary of the Invention

[0006] According to a first aspect of the present invention, there is provided an aircraft landing gear, the aircraft landing gear including a suspension mechanism having a four-bar linkage and a shock absorber, wherein, in the case where the landing gear is in the deployed configuration:

[0007] The four-bar linkage includes an upper link rigidly extending from an upper front pivot to an upper rear pivot, a lower link rigidly extending from a lower front pivot to a lower rear pivot, a front link rigidly extending from the upper front pivot to the lower front pivot, and a rear link rigidly extending from the upper rear pivot to the lower rear pivot;

[0008] The lower link has a front wheel support and a rear wheel support, each wheel support being arranged to support one or more wheels;

[0009] The four-bar linkage is movable between an extended position and a retracted position, and the upper link and the lower link are closer together when the four-bar linkage is in the retracted position compared to when the four-bar linkage is in the extended position;

[0010] The shock absorber is arranged to push the four-bar linkage away from the retracted position and push the four-bar linkage towards the extended position; and

[0011] The length of the upper link is adjustable to change the distance between the upper front pivot and the upper rear pivot.

[0012] The adjustable length of the upper link can allow the position of the four-bar linkage to adapt to different situations, for example allowing the landing gear to adopt a form more suitable for retraction for cruising, and a form more suitable for providing shock absorption, ride comfort, etc. during taxiing, takeoff, and landing. The adjustability of the upper link may be particularly beneficial because this link may carry a smaller load than other links, such as the front link and the rear link, which may impose less stress on the mechanism capable of adjusting it. Alternatively or additionally, it may be beneficial to extend control lines (such as electrical wiring and / or hydraulic pipes) to the upper link for the purpose of adjusting it, rather than to another link that may require a longer length and / or may be more vulnerable to debris and / or impacts in the air.

[0013] The use of a four-bar linkage can allow the suspension mechanism to move under load in a manner beneficial to the performance of the aircraft when on the ground. For example, the four-bar linkage can keep the lower link substantially horizontal (e.g., substantially parallel to the ground) throughout the entire movement range of the suspension mechanism, thereby keeping the wheels supported by the front wheel support and the wheels supported by the rear support in good contact with the ground when the aircraft takes off or lands.

[0014] The term "suspension mechanism" is intended to have its ordinary meaning. In cases where further definition is considered necessary, although understood by a person skilled in the art, the suspension mechanism can be considered as a mechanism configured to bear the weight of the aircraft on the ground while allowing limited relative movement of the wheels with respect to the aircraft to absorb shocks. The suspension mechanism can be damped, for example, using one or more hydraulic dampers or electromagnetic dampers, or the suspension mechanism can be undamped.

[0015] A link rigidly extending between two pivots as referred to herein shall be understood to mean that the link extends between these two pivots and at least the portion of the link extending between the pivots is rigid. The term "rigid" is intended to have its ordinary meaning. In cases where further definition is considered necessary, although understood by a person skilled in the art, a link can be considered rigid if it does not deform significantly during use (e.g., during the movement of a four-bar linkage between an extended position and a retracted position during takeoff and landing).

[0016] To avoid ambiguity, references to "front" link, "rear" link, "upper" link, and "lower" link are used to denote the general position of the link as a whole, and more specifically, the general position of the portions of these links extending between the relevant pivots. This does not imply that different links cannot overlap each other in different directions, nor does it imply that any particular link reaches further in a particular direction than any other link. For example, an upper link can have a portion extending further forward than a front link, and / or a portion of a lower link can extend above an upper link. Although understood by a person skilled in the art, in cases where further definition is required, in a four-bar linkage, the front link can be regarded as the link having the most forward midpoint among the four links between its corresponding pivots. Similarly, the upper link can be considered as the link having the furthest vertically upward midpoint between its pivots, and so on.

[0017] Each wheel support can be, for example, an axle, a hole in the axle, or a mounting feature for engaging with complementary mounting features of the axle.

[0018] The shock absorber can be, for example, a spring hydraulic damper, a gas spring, a coil spring assembly, or an oil pressure strut.

[0019] The length of the upper link can be adjusted using, for example, a lead screw mechanism, a ball screw mechanism, or a hydraulic cylinder.

[0020] The shape of each of the links can generally be elongate. As an alternative, a part or all of a non-elongate body can form one or more of the links.

[0021] The pivots can be arranged parallel to each other to restrict the movement of the four-bar linkage. For example, the pivots can constrain the four-bar linkage to move within a plane.

[0022] It should be understood that the "retracted position" and "extended position" mentioned herein should not be construed as limiting. Any suitable pair of positions can be the retracted position and the extended position, as long as the upper link and the lower link are closer together in the "retracted position" than in the "extended position".

[0023] The movement of the four-bar linkage from the extended position to the retracted position can cause the front link and the rear link to pivot rearward relative to the upper link.

[0024] Thus, when the landing gear is under load (e.g., when an aircraft including the landing gear is resting on its wheels), the lower link (and thus the wheel) can be positioned further rearward. This can allow the center of gravity of the aircraft to be further rearward, which in turn can allow the use of wings with a higher aspect ratio (for example).

[0025] The landing gear can be configured such that an increase in the length of the upper link causes the rear wheel support to lower relative to the front wheel support.

[0026] In an aircraft including a landing gear, the center of gravity of the aircraft may be in front of the wheel supported by the rear wheel support but behind the wheel supported by the rear wheel support. In such an aircraft, increasing the length of the upper link to lower the rear wheel support relative to the front wheel support can be particularly beneficial, as this can ensure that the rear wheel touches the ground first during landing, thereby avoiding any tendency for the aircraft to tilt backward during touchdown.

[0027] As an alternative, the landing gear can be configured such that an increase in the length of the upper link causes the front wheel support to lower relative to the rear wheel support. As another alternative, the landing gear can be configured such that an increase in the length of the upper link does not cause any change in the height of the wheel supports relative to each other.

[0028] The landing gear can also include a main leg that extends from a proximal mounting point configured to attach to the aircraft to a distal mounting point attached to the four-bar linkage.

[0029] The main leg can provide a greater vertical height to the landing gear, which in turn can provide a greater ground clearance for the aircraft including the landing gear. Compared to an aircraft with a shorter landing gear, the greater ground clearance can allow the aircraft to take off and / or land at a steeper angle.

[0030] As an alternative, the four-bar linkage can be configured to attach directly to the body of the aircraft (such as the fuselage or wing), or the landing gear can include another structure configured to attach the four-bar linkage to the body.

[0031] The main leg can be rigid. Alternatively, the main leg can be capable of elastic deformation (e.g., in the manner of a hydraulic strut).

[0032] The distal mounting point of the main leg can be attached at or near the pivot of the four-bar linkage.

[0033] For example, the distal mounting point of the main leg can be attached at or near the upper rear pivot.

[0034] As an alternative, the distal mounting point of the main leg can be attached to any other suitable point on the four-bar linkage, such as at a position approximately centered between the two pivots of one of the linkages (such as the upper linkage) in the linkage.

[0035] The distal mounting point of the main leg can be pivotally attached to the four-bar linkage.

[0036] This can provide the four-bar linkage with a favorable degree of freedom of movement relative to the main leg.

[0037] As an alternative, the distal mounting point of the main leg can be rigidly attached to one of the linkages (such as the upper linkage) of the four-bar linkage.

[0038] If the distal mounting point of the main leg is attached at or near the pivot of the four-bar linkage and is pivotally attached to the four-bar linkage, then one of the pivots (such as the upper rear pivot) of the four-bar linkage can also pivotally connect the main leg to the four-bar linkage.

[0039] One of the upper front pivot and the upper rear pivot can pivotally attach the main leg to the upper linkage of the four-bar linkage, and the landing gear can further include an auxiliary linkage that extends between the main leg and the other of the upper front pivot and the upper rear pivot.

[0040] The auxiliary linkage can provide a movable structural support for the upper linkage, for example, when adjusting the length of the upper linkage, keeping the upper linkage in a desired orientation compliant with respect to the main leg.

[0041] The shock absorber can extend between the proximal mounting point attached to the main leg and the distal mounting point attached to the four-bar linkage.

[0042] In the case where both the four-bar linkage and the shock absorber are supported by the main leg, the suspension mechanism can be operable without the main leg moving. This can reduce the impact load applied to the main leg, which in turn can allow the proximal mounting point of the main leg to be advantageously compact, simple, and / or lightweight. Alternatively or additionally, it can allow the landing gear to be folded using an advantageously compact, simple, and / or lightweight mechanism for retraction.

[0043] The proximal mounting point of the shock absorber can be pivotally attached to the main leg.

[0044] The distal mounting point of the shock absorber can be attached at or near the pivot of the four-bar linkage device.

[0045] For example, the distal mounting point of the shock absorber can be attached at or near the lower rear pivot.

[0046] As an alternative, the distal mounting point of the shock absorber can be attached to any other suitable point on the four-bar linkage device, such as a position approximately at the center between the two pivots of one of the linkages (such as the lower linkage) in the linkage.

[0047] The distal mounting point of the shock absorber can be pivotally attached to the four-bar linkage device.

[0048] This can provide a favorable degree of freedom of movement for the four-bar linkage device relative to the shock absorber.

[0049] As an alternative, the distal mounting point of the main leg can be slidably attached to or rigidly attached to one of the linkages (such as the lower linkage) of the four-bar linkage device.

[0050] If the distal mounting point of the shock absorber is attached at or near the pivot of the four-bar linkage device and is pivotally attached to the four-bar linkage device, one of the pivots (such as the lower rear pivot) of the four-bar linkage device can also pivotally connect the shock absorber to the four-bar linkage device.

[0051] The main leg can define an elongated recess or cavity that extends along the longitudinal axis of the main leg and houses wiring and / or hydraulic pipes therein.

[0052] The wiring and / or pipes passing through the elongated recess or cavity can advantageously protect the wiring and / or pipes from impact or shock by debris in the air. Alternatively or additionally, it can also reduce the overall diameter of the main leg compared to an arrangement where the wiring and / or pipes pass along the outside of the main leg.

[0053] The groove or cavity can be open, for example, in the form of a groove. Alternatively, the cavity can be circumferentially enclosed by the main leg.

[0054] In the case where the landing gear is in the deployed configuration, the main leg and the shock absorber can be positioned within the main leg plane.

[0055] Positioning the main leg and the shock absorber in a plane can make the landing gear more aerodynamic when in the deployed position (for example, if the plane is aligned parallel to the airflow direction). Alternatively or additionally, it can also make the landing gear more compact in a specific direction, which can make it easier to retract.

[0056] The main leg plane can be regarded as the plane containing the longitudinal axes of the main leg and the shock absorber.

[0057] When the landing gear is in the deployed configuration, the upper link, the lower link, the front link, and the rear link can cooperate to define a link plane.

[0058] All the links of the four-bar linkage being located in a plane can make the landing gear more aerodynamic when in the deployed position (e.g., if the plane is aligned parallel to the airflow direction). Alternatively or additionally, it can also make the landing gear more compact in a particular direction, which can make it easier to retract.

[0059] Alternatively or additionally, all the links being located in a plane can allow the movement of the four-bar linkage to be more easily maintained within that plane, which can allow the movement of the wheel supported by the wheel support of the lower link to be advantageously kept stable.

[0060] When the landing gear is in the deployed configuration, the main leg can be substantially located in the link plane.

[0061] When the main leg and the four-bar linkage have a common plane, the landing gear can be more aerodynamic when deployed, and / or can be more compact in a particular direction, and thus even easier to retract.

[0062] As an alternative, the main leg can extend parallel to the link plane. As another alternative, the main leg can extend at an angle to the link plane.

[0063] When the landing gear is in the deployed configuration, the shock absorber can be substantially located in the link plane.

[0064] When the shock absorber and the four-bar linkage have a common plane, the landing gear can be more aerodynamic when deployed, and / or can be more compact in a particular direction, and thus even easier to retract.

[0065] As an alternative, the shock absorber can extend parallel to the link plane. As another alternative, the shock absorber can extend at an angle to the link plane.

[0066] The front wheel support can be located at or near the lower front pivot.

[0067] This can allow the kinematics of the suspension mechanism to be relatively simple and / or predictable, where the front wheel support moves in substantially the same manner as the lower front pivot. This can make the performance of the suspension mechanism more predictable and / or controllable.

[0068] Alternatively or additionally, the front wheel support being located in this position can reduce the effect of the pivoting of the lower link about the lower front pivot on the wheel attached to the front wheel support. In some arrangements, the smaller movement of the wheel may be beneficial to the performance of the suspension mechanism, as described later.

[0069] The rear wheel support can be positioned behind the lower rear pivot.

[0070] With the rear wheel support so positioned, a relatively small upward rotation of the lower link (e.g., due to adjustment of the upper link length) may cause a relatively large downward movement of the rear wheel support. This can be beneficial if it is desired for the wheel supported by the rear wheel support to be the last to leave the ground during takeoff and / or the first to contact the ground during landing, such as may occur if the center of gravity of the aircraft is located on or behind the wheel supported by the front wheel support.

[0071] Alternatively or additionally, positioning the rear wheel support behind the lower rear pivot can allow the landing gear to extend further rearward from any given mounting point on the aircraft. This in turn can allow the center of gravity of the aircraft to be located in a more rearward position (e.g., due to high aspect ratio wings).

[0072] As an alternative, the rear wheel support can be positioned at the lower rear pivot. As another alternative, the rear wheel support can be positioned in front of the lower rear pivot.

[0073] The lower rear pivot can be located approximately at the center position between the front wheel support and the rear wheel support.

[0074] This can advantageously keep the movement of the front wheel support and the rear wheel support, and thus the movement of the wheels attached thereto, stable during pivoting of the lower link about the lower rear pivot. In contrast, in an arrangement where one wheel support is located quite far from the lower rear pivot, since the effect of leverage is different according to the wheel support being discussed, disturbing one wheel will produce a different effect compared to disturbing the other wheel in the same way.

[0075] The landing gear can move between a deployed configuration and a stowed configuration.

[0076] By stowing the landing gear when not needed (e.g., during cruise), an aircraft including the landing gear can be more aerodynamic.

[0077] The landing gear can be configured to rotate between the deployed configuration and the stowed configuration. As an alternative, the landing gear can be configured to move between the stowed configuration and the deployed configuration only by translation (e.g., vertical extension / retraction).

[0078] Alternatively or additionally, the landing gear can also be configured to fold when moving from the deployed configuration to the stowed configuration and deploy when moving from the stowed configuration to the deployed configuration. This can allow the landing gear to take a more compact form when stowed, thus saving space.

[0079] According to a second aspect of the present invention, there is provided an aircraft landing gear, which includes a suspension mechanism. The suspension mechanism includes a biasing member and a linkage device. The linkage device includes four rigid elongated members connected to each other by pivots to form a quadrilateral member, with one of the pivots at each corner, wherein:

[0080] One of the rigid elongated members forms the bottom of the quadrilateral member and has a front wheel mounting point and a rear wheel mounting point;

[0081] One of the rigid members forms the top of the quadrilateral member;

[0082] The suspension mechanism has a high configuration and a low configuration. When the suspension mechanism is in the low configuration, the rigid members forming the top and bottom of the quadrilateral member are closer together compared to when the suspension mechanism is in the high configuration;

[0083] The biasing member biases the suspension mechanism towards the high configuration; and

[0084] The length of the rigid elongated member forming the top of the quadrilateral member is adjustable to change the distance between two of the pivots.

[0085] The adjustable length of the rigid elongated member forming the top of the quadrilateral member can allow the shape of the quadrilateral member and thus the configuration of the suspension mechanism to adapt to different situations. For example, it can allow the landing gear to adopt a form more suitable for retraction for cruising, as well as a form more suitable for providing shock absorption, ride comfort, etc. during taxiing, takeoff, and landing.

[0086] Using a quadrilateral member with a pivot at each corner can allow the suspension mechanism to move in a way that is beneficial to the performance of the aircraft under load when on the ground. For example, the quadrilateral member can keep the link forming the bottom of the quadrilateral member substantially horizontal (e.g., substantially parallel to the ground) throughout the entire movement range of the suspension mechanism, so that the wheels supported by the front wheel mounting point and the rear wheel mounting point maintain good contact with the ground when the aircraft takes off or lands.

[0087] According to a third aspect of the present invention, there is provided a suspension mechanism for an aircraft landing gear according to the first or second aspect of the present invention.

[0088] Such a suspension mechanism can be used to provide one or more of the above advantages for the landing gear.

[0089] According to a fourth aspect of the present invention, there is provided an aircraft including an aircraft landing gear according to the first or second aspect of the present invention.

[0090] The aircraft may include a landing gear according to the first or second aspect of the present invention as a main landing gear. Alternatively or additionally, the aircraft may include a landing gear according to the first or second aspect of the present invention as a nose landing gear.

[0091] The aircraft may be a fixed-wing aircraft, such as a commercial airliner. As an alternative, the aircraft may be a rotary-wing aircraft.

[0092] The landing gear according to the first or second aspect of the present invention may be mounted to, for example, the fuselage of the aircraft and / or the wing of the aircraft.

[0093] In the case where the landing gear is in the stowed configuration, at least a portion of the landing gear may be received within a cavity in the wing of the aircraft.

[0094] This may further improve the aerodynamic performance of the aircraft.

[0095] Alternatively or additionally, in the case where the landing gear is in the stowed configuration, at least a portion of the landing gear may be received within a cavity in the fuselage of the aircraft.

[0096] Alternatively or additionally, in the case where the landing gear is in the stowed configuration, at least a portion of the landing gear may be received within a discrete housing, such as a housing mounted to the wing and / or the fuselage of the aircraft.

[0097] The shock absorber may define a longitudinal axis, and the landing gear may be arranged such that, when in the deployed configuration, the longitudinal axis of the shock absorber is prevented from reaching an angle of less than 70 degrees, such as less than 75 degrees or less than 80 degrees, relative to a plane containing the pitch axis and the roll axis of the aircraft.

[0098] In the case where the shock absorber is thus held substantially vertically (when the aircraft is horizontal), it can advantageously be closely aligned with the direction in which the weight of the aircraft acts. This, in turn, can improve the response of the shock absorber (and thus the response of the entire suspension mechanism).

[0099] The landing gear may be arranged such that the lower link remains substantially parallel to a plane containing the pitch axis and the roll axis of the aircraft throughout the movement of the four-bar linkage between the extended position and the retracted position.

[0100] In the case where the lower link is thus held substantially horizontal (when the aircraft is horizontal), the front wheel support and the rear wheel support can be maintained at substantially the same height above the ground. Thus, the wheels supported thereby can be positioned at approximately the same height at landing, such that they touch the ground at approximately the same time during landing, and / or each wheel can bear a relatively equal proportion of the weight of the aircraft (as opposed to if one of the wheel supports were significantly lower, in which case the wheel supported thereby might bear an excessive proportion of the weight).

[0101] It will be understood, of course, that features described in connection with one aspect of the present invention may be incorporated into other aspects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0102] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

[0103] Figure 1 A perspective view of an aircraft according to a first embodiment of the present invention is shown;

[0104] Figure 2 Shows Figure 1 A rear perspective view of the landing gear of the aircraft of

[0105] Figure 3 Shows Figure 2 A side view of the landing gear of , in which the four-bar linkage of the landing gear is in the extended position;

[0106] Figure 4 Shows Figure 2 and Figure 3 A side view of the landing gear of , in which the four-bar linkage is in the retracted position; and

[0107] Figure 5 Shows Figures 2 to 4 A side view of the landing gear of , in which the length of the upper link of the four-bar linkage has been increased. DETAILED DESCRIPTION

[0108] Figure 1 An aircraft 2 according to an embodiment of the present invention is shown. The aircraft 2 has a fuselage 4, a tail fin 6 and two wings 8. Each wing 8 extends from the fuselage 4 in the spanwise direction and terminates at an upward wing tip 10. Each wing 8 supports an engine 12 midway along its span length. These components of the aircraft have a conventional design and are of little relevance to the present invention and will therefore not be described in detail.

[0109] The aircraft 2 has three landing gears, which are not visible in Figure 1 since each of these three landing gears is in a stowed configuration. In the present embodiment, the aircraft 2 has a nose landing gear located on the lower side portion of the fuselage 4 at the front of the aircraft, and two main landing gears located on the lower side portions of the respective wings 8 between the engines 12 of the wings 8 and the fuselage 4. The nose landing gear has a conventional design and is not important for the present invention and will therefore not be described in detail.

[0110] Figure 2 One of the main landing gears 14 of the aircraft 2 in the deployed configuration is shown. More specifically, Figure 2The main landing gear 14 on the left side is shown. The main landing gear on the right side is substantially a mirror image of the main landing gear 14 on the left side. Now with reference to Figure 1 reference Figure 2 , the landing gear 14 has a main leg 16 that extends generally downward from a proximal mounting point 18 (when the landing gear 14 is in the deployed configuration). The main leg 16 supports a suspension mechanism 20, which in turn supports two front wheels 22 and two rear wheels 24.

[0111] The landing gear 14 also has a front inner side strut 26 and a rear inner side strut 28 that extend between pivotable joints on the main leg 16 and the internal structure (not shown) of the wing 8. The side struts 26, 28 provide structural support for the main leg 16, particularly to stabilize the main leg 16 against lateral and drag loads. Each side strut 26, 28 has a hinge joint 30 around its center to assist in retraction as described below.

[0112] The proximal mounting point 18 of the main leg 16 has a set of three protrusions 32, each of the three protrusions 32 having a circular hole 34. The holes 34 are aligned with each other and positioned to receive an axis (not visible) provided in the internal structure of the wing 8 to attach the landing gear 14 to the aircraft 2. Near the proximal mounting point 18, the main leg 16 has an elongated cavity 36, the purpose of which will be discussed later.

[0113] The proximal mounting point 18 also has a projection 38 that extends between two of the protrusions 32 and is pivotally connected to a retraction actuator 40 in the form of a hydraulic cylinder. The retraction actuator 40 is arranged to move the landing gear 14 between a retracted configuration and a deployed configuration. To move the landing gear 14 from the deployed configuration (as shown in Figure 2 and Figure 3 ) to the retracted configuration, the retraction actuator 40 is extended to push the projection 38 of the main leg 16, causing it to rotate (counterclockwise when viewed from the perspective of Figure 2 ). The side struts 26, 28 of the landing gear 14 fold at their respective hinge joints 30 to allow the main leg 16 to rotate inward. Continued extension of the retraction actuator 40 rotates the landing gear into a cavity (not visible) in the lower side portion of the wing 8. To move the landing gear 14 from the retracted configuration to the deployed configuration, the retraction actuator 40 retracts, and the above process is reversed.

[0114] Figure 3 The landing gear 14 is shown from the side (more specifically, the left side), from which more details of the main leg 16 and the suspension mechanism 20 can be determined. It is noted that in this view, one of the front wheels 22 has been removed, as have the folding side struts 26, 28, the projection 38, and the retraction actuator 40. Now with reference to Figure 1 referenceFigure 2 and Figure 3 , the main leg 16 extends from the proximal mounting point 18 to the distal mounting point 42, and the distal mounting point is provided by a pair of protrusions 44 (one of the pair of protrusions 44 is visible in Figure 3 ). The main leg 16 has a tubular member 46 extending between the proximal mounting point 18 and the distal mounting point 42, and a boss 48 supported by three struts 50, with a pair of webs 52 between the struts 50.

[0115] The suspension mechanism 20 has a four-bar linkage 54 and a shock absorber 56. In this embodiment, the shock absorber 56 is in the form of a hydraulic strut. The four-bar linkage consists of an upper link 60, a rear link 62, a lower link 64, and a front link 66. The upper link 60, the rear link 62, the lower link 64, and the front link 66 are connected together by an upper front pivot 70, an upper rear pivot 72, a lower rear pivot 74, and a lower front pivot 76. The upper link 60 extends between the upper front pivot 70 and the upper rear pivot 72, the rear link 62 extends between the upper rear pivot 72 and the lower rear pivot 74, the lower link 64 extends between the lower rear pivot 74 and the lower front pivot 76, and the front link 66 extends between the lower front pivot 76 and the upper front pivot 70. In other words, the upper front pivot 70 pivotally connects the front link 66 and the upper link 60, the upper rear pivot pivotally connects the upper link 60 and the rear link 62, the lower rear pivot 74 pivotally connects the rear link 62 and the lower link 64, and the lower front pivot pivotally connects the lower link 64 and the front link 66. Each of the links 60, 62, 64, 66 is substantially rigid and thus extends rigidly between its respective pivots 70, 72, 74, 76.

[0116] The front link 66 and the rear link 62 are each composed of a pair of parallel arms, and one of the pair of parallel arms can be seen from the perspective of Figure 3 . The lower link 64 is in the form of a generally cylindrical beam and includes a front wheel support 78 and a rear wheel support 80, and each of the front wheel support 78 and the rear wheel support 80 is in the form of a fixed shaft. The front wheel support 78 rotatably supports the front wheel 22, and the rear wheel support 80 rotatably supports the rear wheel 24. The upper link 60 of this embodiment is in the form of a hydraulic cylinder with a locking function. The locking function makes the cylinder 60 rigid, thereby preventing the axial force applied thereto from causing the cylinder to retract (retract in the case of axial compression) or extend (extend in the case of axial tension).

[0117] The distal mounting point 42 of the main leg 16 is attached to the four-bar linkage 54 at the upper rear pivot 72, more specifically pivotally attached to the four-bar linkage 54. Thus, the upper rear pivot 72 pivotally connects the main leg 16 to the upper link 60 and the rear link 62, and also pivotally connects the upper link 60 to the rear link 62. The main leg 16 is also connected to the four-bar linkage 54 by an auxiliary link 82 that extends between the upper front pivot 70 and a pivot joint 84 on the tubular member 46 of the main leg 16. The auxiliary link 82 is pivotally connected to the upper link 60 by the upper front pivot 70. Thus, the upper front pivot 70 pivotally connects the auxiliary link 82 to the upper link 60 (and effectively pivotally connects the auxiliary link 82 to the front link 66), and also pivotally connects the upper link 60 to the front link 66.

[0118] As described above, the main leg 16 has an elongated cavity 36. The elongated cavity 36 is a completely enclosed cavity that extends along the longitudinal axis of the main leg 16 through the tubular member 46 and terminates at an outlet (not visible) near the distal mounting point 42. Hydraulic lines (not visible) for supplying a hydraulic cylinder forming the upper link 60 extend along the elongated cavity 36, as does the wiring for an electronic wheel speed sensor (not visible).

[0119] The shock absorber 56 of the suspension mechanism 20 extends from a proximal mounting point 86 that is pivotally attached to a boss 48 of the main arm 16 to a distal mounting point 88 that is pivotally connected to a projection 90 of the lower link 64 at a position adjacent to the lower rear link 74. In this embodiment, the main arm 16 and the shock absorber 56 are located in the same plane, which is referred to herein as the main arm plane.

[0120] The links 60, 62, 64, 66 of the four-bar linkage 54 are all located in the same plane, which is referred to herein as the link plane. In the present embodiment, the main arm plane and the link plane are coplanar, forming a single plane. However, in other embodiments, the main arm plane and the link plane (if present) may be parallel to each other or angled with respect to each other. As Figure 2 shown, positioning the main arm 16, the four-bar linkage 54, and the shock absorber 56 in the same plane gives the landing gear 14 a particularly slender profile when viewed from the front / back. This not only gives the landing gear 14 relatively aerodynamic characteristics but also allows it to be received in a relatively shallow cavity in the wing 8.

[0121] Figure 2 and Figure 3 shows the landing gear with the four-bar linkage 54 in the extended position. The four-bar linkage 54 is capable of moving between an extended position and a retracted position. The landing gear 14 is shown in Figure 4 with the four-bar linkage 54 in the retracted position, and will now be described in connection withFigures 1 to 3 Refer to Figure 4 for reference.

[0122] When the four-bar linkage 54 is in the retracted position, the upper link 60 and the lower link 64 are closer together than when the four-bar linkage 54 is in the extended position. When the four-bar linkage 54 moves from the extended position to the retracted position, the front link 66 pivots rearwardly about the upper front pivot 70 relative to the upper link 60, the rear link 62 pivots forwardly about the upper rear pivot 72 relative to the upper link 60, and the lower link 64 swings rearwardly and upwardly relative to the upper link 60 together with the lower front pivot 76 and the lower rear pivot 74. However, it should be understood that this description applies when the main leg 16 and the upper link 60 are taken as the reference system. Similarly, it can be said that when the four-bar linkage 54 moves from the extended position to the retracted position, the front link 66 pivots forwardly about the lower front pivot 76 relative to the lower link 64, the rear link 62 pivots forwardly about the lower rear pivot 74 relative to the lower link 64, and the upper link swings downwardly and forwardly relative to the lower link 64 together with the upper front pivot 70 and the upper rear pivot 72.

[0123] The shock absorber 56 pushes the four-bar linkage 54 away from the retracted position to the extended position. When the four-bar linkage 54 is in the retracted position (or actually in any position between the extended position and the retracted position), the shock absorber 54 is compressed between the boss 48 and the lower rear pivot 74. The restoring force from the shock absorber 54 biases the boss 48 and the lower rear pivot 74 apart, thereby biasing the four-bar linkage to the extended position. However, when the aircraft 2 is on the ground, a portion of its weight acts through the landing gear 14, forcing the four-bar linkage to overcome the bias of the shock absorber 54 and reach the retracted position. In the case of an impact load, such as when hitting a bump during the first landing or taxiing, the four-bar linkage 54 can be further compressed to a position beyond the retracted position, but the restoring force of the shock absorber 54 will then return the landing gear to the retracted position.

[0124] It is noted that throughout the movement of the four-bar linkage 54 between the extended position and the retracted position, the upper link 60 and the lower link 64 remain substantially parallel to each other. Since the upper link 60 is positioned substantially parallel to the plane containing the pitch axis and the roll axis (not shown) of the aircraft 2, this has the effect of making the lower link 64 also substantially parallel to this plane. Since the front wheel 22 and the rear wheel 24 have the same diameter, this means that when the aircraft is flying horizontally, the two wheels will contact the ground with approximately the same force. For example, this can have advantages in terms of braking performance.

[0125] The structure and function of the landing gear 14 have been described above in terms of the configuration that the landing gear 14 is expected to be in when contacting the ground and during flight before or shortly after contacting the ground. However, the landing gear has another configuration that is entered by changing the length of the upper link 60 of the four-bar linkage 54. More specifically, in this embodiment, as Figure 5 shown, the length of the upper link 60 can be increased by extending the hydraulic cylinder.

[0126] Now in conjunction with Figures 1 to 4 referring to Figure 5 , increasing the length of the upper link 60 changes the shape of the four-bar linkage 54. More specifically, in this embodiment, the auxiliary link 82 actually tethers the upper front pivot 70 (and thus the front end portion of the upper link 60) to the pivot joint 84. Therefore, as the length of the upper link 60 increases, it pivots upward about the upper rear pivot 72. Since the lower link 64 is actually tethered to the upper link 60 by the front link 66 (and the rear link 62), the lower link 64 is also lifted upward. This has the effect of lowering the rear wheel 24 relative to the front wheel 22 (or, in other words, raising the front wheel 22 relative to the rear wheel 24).

[0127] It is worth noting that in this embodiment, although the lower link 64 remains substantially parallel to the upper link 60 regardless of its length, adjusting the length of the upper link 60 from Figures 2 to 4 the length shown to Figure 5 the length shown causes the upper link 60 and the lower link 64 to move such that the upper link 60 and the lower link 64 are no longer parallel to the plane including the pitch axis and the roll axis (not shown) of the aircraft 2.

[0128] In this embodiment, the purpose of increasing the length of the upper link 60 is to rotate the lower link 64 upward and thus reduce the overall front-to-rear length of the landing gear 14 (in this case, the front-to-rear length is determined by the horizontal distance between the front of the front wheel 22 and the rear of the rear wheel 24). This allows the landing gear 14 to be retracted into a narrower cavity in the wing 8 (which may be all the available space in a high aspect ratio wing).

[0129] Particularly noteworthy is that in this embodiment, the front wheel support 78 is positioned near the lower front pivot 76. With the front wheel support 78 so positioned, the vertical impact applied to the front wheel 22 by the ground only applies a small moment to cause the lower link 64 to rotate about the lower front pivot 76. Therefore, the rotation of the lower link 64 about the pivot 76 is relatively small (if any). Any such impact will generate a greater moment to cause the lower link 64 to rotate about the lower rear pivot 74. However, the rear wheel 24 in contact with the ground can more effectively counteract this moment, thereby weakening the impact of such shock on the entire aircraft 2.

[0130] It is also worth noting that the rear wheel support 80 is positioned behind the lower rear pivot 74, and in fact, the lower rear pivot 74 is generally positioned at the center between the front wheel support 78 and the rear wheel support 80. Since the distance between the lower rear pivot 74 and each of the wheel supports 78, 80 is substantially the same, the torque generated by the front wheel 22 is substantially the same as the torque generated by the rear wheel 24. Therefore, the suspension mechanism 20 can be more stable. On the contrary, for example, if the rear wheel support 80 is quite far from the lower rear pivot 74, then due to its additional leverage, the upward impact applied to the rear wheel 24 may cause the front wheel 22 to be pressed into the ground with a greater force. This may in turn cause the landing gear 14 to rebound, thereby having a negative impact on the riding comfort.

[0131] A final fact worth noting about the configuration of the present embodiment is that the landing gear is configured to hold the shock absorber 56 so as to prevent it from moving to a position where the angle of its longitudinal axis with respect to the plane containing the pitch axis and roll axis (not shown) of the aircraft is less than about 82 degrees. In other words, when the aircraft 2 is horizontal, the shock absorber 56 is generally held vertically. Therefore, the shock absorber 56 is relatively closely aligned with the direction in which the weight of the aircraft 2 acts.

[0132] In the above description, when referring to a whole or an element having known, obvious or foreseeable equivalents, such equivalents are incorporated herein as if separately set forth. The true scope of the present invention should be determined with reference to the claims, and the true scope of the present invention should be construed as including any such equivalents. The reader will also understand that the wholes or features described as preferred, advantageous, convenient, etc. of the present invention are optional and do not limit the scope of the independent claims. In addition, it should be understood that in some embodiments of the present invention, such optional wholes or features, although they may be beneficial, may not be desired and may therefore not be present in other embodiments.

[0133] Unless the context otherwise requires, the term "or" shall be construed as "and / or".

Claims

1. An aircraft landing gear, comprising a suspension mechanism, wherein the suspension mechanism has a four-bar linkage and a shock absorber, wherein: With the landing gear in the deployed configuration: The four-bar linkage includes an upper link rigidly extending from an upper front pivot to an upper rear pivot, a lower link rigidly extending from a lower front pivot to a lower rear pivot, a front link rigidly extending from the upper front pivot to the lower front pivot, and a rear link rigidly extending from the upper rear pivot to the lower rear pivot; The lower link has a front wheel support and a rear wheel support, each wheel support being arranged to support one or more wheels; The four-bar linkage is movable between an extended position and a shortened position, wherein the upper link and the lower link are closer together when the four-bar linkage is in the shortened position than when the four-bar linkage is in the extended position; The shock absorber is arranged to urge the four-bar linkage away from the shortened position and to urge the four-bar linkage toward the extended position; and The length of the upper link is adjustable to change the distance between the upper front pivot and the upper rear pivot.

2. The aircraft landing gear according to claim 1, wherein: Movement of the four-bar linkage from the extended position to the shortened position causes the front and rear links to pivot rearwardly relative to the upper link.

3. The aircraft landing gear according to claim 1 or 2, wherein: The landing gear is configured such that an increase in the length of the upper link causes the rear wheel support to be lowered relative to the front wheel support.

4. An aircraft landing gear according to any one of claims 1 to 3, further comprising a main leg extending from a proximal mounting point configured for attachment to an aircraft to a distal mounting point to which the four-bar linkage is attached.

5. The aircraft landing gear according to claim 4, wherein: The distal mounting point of the main leg is attached to the four-bar linkage at or near a pivot.

6. An aircraft landing gear according to claim 4 or 5, wherein: The distal mounting point of the main leg is pivotally attached to the four-bar linkage.

7. An aircraft landing gear according to claim 6 when dependent on claim 5, wherein: One of the upper front pivot and the upper rear pivot pivotally attaches the main leg to the upper link of the four-bar linkage, and the landing gear further includes an auxiliary link extending between the main leg and the other of the upper front pivot and the upper rear pivot.

8. An aircraft landing gear according to any one of claims 4 to 7, wherein: The shock absorber extends between a proximal mounting point attached to the main leg and a distal mounting point attached to the four-bar linkage.

9. The aircraft landing gear according to claim 8, wherein: The distal mounting point of the shock absorber is attached to the four-bar linkage at or near a pivot.

10. The aircraft landing gear according to claim 9, wherein: The distal mounting point of the shock absorber is pivotably attached to the four-bar linkage.

11. An aircraft landing gear according to any one of claims 4 to 10, wherein: The main leg defines an elongated recess or cavity that extends along the longitudinal axis of the main leg and accommodates wiring and / or hydraulic conduits therein.

12. An aircraft landing gear according to any one of claims 4 to 11, wherein: With the landing gear in the deployed configuration, the main leg and the shock absorber are positioned in a main leg plane.

13. An aircraft landing gear according to any preceding claim, wherein: With the landing gear in the deployed configuration, the upper link, the lower link, the front link, and the rear link cooperate to define a link plane.

14. An aircraft landing gear according to claim 13 when dependent on any one of claims 4 to 12, wherein: With the landing gear in the deployed configuration, the main leg is positioned substantially in the link plane.

15. An aircraft landing gear according to claim 13 or 14, wherein: With the landing gear in the deployed configuration, the shock absorber is positioned substantially in the link plane.

16. An aircraft landing gear according to any preceding claim, wherein: The front wheel support is positioned at or near the lower front pivot.

17. An aircraft landing gear according to any preceding claim, wherein: The rear wheel support is positioned rearwardly of the lower rear pivot.

18. An aircraft landing gear according to claim 17 when dependent on claim 16, wherein: The lower rear pivot is positioned approximately centrally between the front and rear wheel supports.

19. An aircraft landing gear according to any preceding claim, wherein: The landing gear is movable between the deployed configuration and the stowed configuration.

20. An aircraft landing gear, the aircraft landing gear comprising a suspension mechanism, the suspension mechanism comprising a biasing member and a linkage, the linkage comprising four rigid elongated members connected to each other by pivots to form a quadrilateral, wherein each corner has one of the pivots, wherein: One of the rigid elongated members forms a base of the quadrilateral and has front and rear wheel mounting points; One of the rigid members forms the top of the quadrilateral; the suspension mechanism having a tall configuration and a short configuration, the rigid members forming the top and bottom of the quadrilateral being closer together when the suspension mechanism is in the short configuration than when the suspension mechanism is in the tall configuration; the biasing member biases the suspension mechanism toward the high configuration; as well as The length of the rigid elongate member forming the top of the quadrilateral is adjustable to vary the distance between two of the pivots.

21. A suspension mechanism for an aircraft landing gear according to any preceding claim.

22. An aircraft comprising an aircraft landing gear according to any one of claims 1 to 20.

23. An aircraft according to claim 22 when dependent on claim 19, wherein: With the landing gear in the stowed configuration, at least a portion of the landing gear is received within a cavity in a wing of the aircraft.

24. An aircraft according to claim 22 or 23, wherein: The shock absorber defines a longitudinal axis, and the landing gear is arranged to prevent the longitudinal axis of the shock absorber from reaching an angle of less than 75 degrees relative to a plane containing a pitch axis and a roll axis of the aircraft when in the deployed configuration.

25. An aircraft according to any one of claims 22 to 24, wherein: The landing gear is arranged to maintain the lower link substantially parallel to a plane containing the pitch and roll axes of the aircraft throughout movement of the four-bar linkage between the extended and shortened positions.

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