Aircraft landing gear shock absorber strut

Abstract

Aircraft landing strut 50 comprising: an outer cylinder 26 having a cylinder bore, the cylinder bore defining a chamber containing a mixable damping liquid and gas; a sliding tube 28 movable between compressed and extended positions, a tube bore in fluid communication with the cylinder bore to exchange damping liquid; an elongate metering pin 34 comprising an axial channel for passage of damping liquid as the sliding tube moves between extended and compressed positions; and a flow restricting plate 52 including: a first portion 52a having a first damping orifice DO wherein the pin axially moves as the sliding tube moves between extended and compressed positions to vary the free space cross sectional area of the first damping orifice controlling axial flow of the damping liquid J moving from the tube bore to the cylinder bore as the sliding tube moves from extended to compressed positions; and a second portion 52b having a second damping orifice DO2 for passage of damping liquid as the sliding tube moves from extended to compressed positions providing a second flow of liquid J2, wherein the second orifice directs the flow of liquid towards an axial channel of the pin to disrupt the flow.

Description

Background It is common for an aircraft landing gear assembly to include a main shock absorber strut having an upper end arranged to be pivotally coupled to the underside of the aircraft and a lower end coupled to a wheel and brake assembly. Such shock absorber struts can comprise an outer cylinder and a sliding tube arranged to telescope relative to the outer cylinder. The shock absorber strut can be compressed and extended as the sliding tube moves relative to the outer cylinder. The two portions are coupled together to define a chamber containing oil and a gas. As the shock absorber is compressed, oil within the chamber is forced through damping orifices and the gas is compressed, in order to dampen landing loads. The compressed gas serves as a spring to lengthen the shock absorber as applied external load decreases. Such telescopic landing gear can be provided with an elongate metering pin mounted on the sliding tube to move with it, inside the chamber. A mating damping orifice is provided within the chamber, often supported on an orifice support tube. As the sliding tube moves relative to the outer cylinder, a control portion of the metering pin moves through the damping orifice. Variation in the diameter or profile of the metering pin along the control portion varies the free space of the damping orifice through which oil can flow. Thus, the profile of the metering pin affects damping properties of the shock absorber based on shock absorber extension. EP3069994B1 and WO2021 / 019422 describe aircraft landing gear shock absorber struts including a metering pin. The present inventor has devised a new type of aircraft landing gear assembly that can have one of more of the following advantages relative to known aircraft landing gear assemblies: • improved load reaction of the landing gear upon rapid closure of the shock absorbing strut • improved damping • more consistent shock absorber characteristics over repeated landings or rough taxiing Summary According to a first aspect of the invention, there is provided an aircraft landing gear shock absorber strut comprising: an outer cylinder having an inner surface defining a cylinder bore extending into the outer cylinder from a first axial face of the outer cylinder, the cylinder bore defining an oleo-pneumatic chamber containing a damping liquid and a gas which can mix within the cylinder bore; a sliding tube including a first end portion movably mounted within the cylinder bore so as to be movable along the cylinder bore between a compressed position, in which a second end portion of the sliding tube disposed outside of the bore is relatively close to the first axial face of the outer cylinder, and an extended position, in which the second end portion of the sliding tube is relatively far from the first axial face of the outer cylinder, the sliding tube including a tube bore extending into the sliding tube from the first end portion, the tube bore being arranged in fluid communication with the cylinder bore to exchange the damping liquid with the cylinder bore; an elongate metering pin having a longitudinal axis and including an axial channel for passage of damping liquid as the sliding tube moves from the extended position towards the compressed position; and a flow restricting plate including: a first portion provided with a first damping orifice in which the metering pin is located and through which the metering pin axially moves as the sliding tube moves between the extended and compressed positions to vary the free space cross sectional area of the first damping orifice to control an axial flow of the damping liquid moving from the tube bore to the cylinder bore as the sliding tube moves from the extended position towards the compressed position; and a second portion provided with a second damping orifice for passage of damping liquid as the sliding tube moves from the extended position towards the compressed position to define a second flow of the damping liquid, wherein the second damping orifice is orientated to direct the second flow of damping liquid towards the axial channel of the metering pin to disrupt the axial flow of damping liquid. Optionally, the axis of the second damping orifice is at an angle of at least 15 degrees with respect to the axis of the first damping orifice, in some embodiments at an angle of at least 25 degrees, in some embodiments at an angle of at least 35 degrees and in some embodiments at an angle of at least 45 degrees. Optionally, the axis of the second damping orifice is at an angle of 15 degrees to 90 degrees with respect to the axis of the first damping orifice, in some embodiments at an angle of 25 degrees to 89 degrees, in some embodiments at an angle of 25 degrees to 85 degrees, in some embodiments at an angle of 35 degrees to 80 degrees and in some embodiments at an angle of 45 degrees to 70 degrees. Optionally, the flow restricting plate is defined by an end portion of an orifice support tube, the office support tube being coupled to the outer cylinder to maintain the flow restricting plate at a fixed distance from a second axial face of the outer cylinder, the orifice support tube having a sidewall provided with a plurality of fluid passage holes. Optionally, metering pin has a circular cross section and the axial channel has a base defined by a chord of the circular cross section, such that the axial channel has open sides to enable the second flow of damping liquid to disrupt the axial flow of damping liquid moving along the channel. Optionally, the first portion and the second portion of the flow restricting plate are parallel and the second orifice has an inlet and outlet of a first diameter and includes a central portion of reduced diameter with respect to the inlet and outlet. Optionally, the second portion of the flow restricting plate is non-parallel with respect to the first portion and the axis of the second orifice is normal with respect to the second portion. Alternatively, the axis of the second orifice can be non-normal with respect to the surface plane of the second portion. Optionally, the shock absorber strut further comprises a baffle plate including a plurality of axial fluid passages and positioned in a fixed relationship with respect to the flow restricting plate such that the axial flow of damping liquid strikes the baffle plate once disrupted by the second flow of damping liquid. Optionally, the orifice support tube comprises a curved surface positioned in a fixed relationship with respect to the flow restricting plate such that the axial flow of damping liquid strikes the curved surface once disrupted by the second flow of damping liquid, the curved surface being curved away from the axis of the metering pin to diffuse the disrupted axial flow of damping liquid. Optionally, the curved surface directs the disrupted axial flow of damping liquid to a fluid passage hole through the orifice support tube. Optionally, the curved surface is defined as a vane. Optionally, the vane is defined by a tube. Optionally, the tube widens away from the metering pin to reduce the velocity of the fluid flow and / or includes projections extending into the tube in order to dissipate the fluid jet energy in turbulence. Optionally, the flow restricting plate includes one or more further portions each provided with a further damping orifice for passage of damping liquid as the sliding tube moves from the extended position towards the compressed position to define a further flow of the damping liquid, each further damping orifice being orientated to direct the further flow of damping liquid towards the or a further axial channel of the metering pin to disrupt the or a further axial flow of damping liquid. Optionally, the flow restricting plate is formed as an assembly of sub plate components. Alternatively, the flow restricting plate can be unitary in nature. According to a second aspect of the invention, there is provided an aircraft landing gear assembly comprising: the aircraft landing gear shock absorber strut according to any preceding claim; a wheel or other ground contacting assembly coupled to the shock absorber strut; and a mounting bearing via which the aircraft landing gear assembly is arranged to be rigidly coupled to an aircraft or movably coupled to an aircraft for movement between a stowed condition for flight and a deployed condition for take-off and landing. Optionally, the aircraft landing gear assembly further comprises a side stay, drag stay or plunger lock arrangement coupled to the shock absorber strut and arranged to enable the shock absorber strut to be maintained in the deployed condition. Brief Description of the Drawings By way of example only, certain embodiments of the invention will now be described by reference to the accompanying drawings, in which: Figure 1 is a diagram of an aircraft; Figures 2 and 3 are diagrams of a known aircraft landing gear assembly; Figures 4a and 4b are diagrams of a known shock absorbing strut, illustrating axial flow of damping liquid during compression of the shock absorber; Figure 4c is a cross section diagram of a known fluted metering pin; Figure 5 is invention; Figure 6 is invention; Figure 7 is invention; Figure 8 is invention; Figure 9 is diagram diagram diagram diagram diagram invention; and Figures 10a and 10b of of of of of are shock absorbing shock absorbing shock absorbing shock absorbing shock absorbing strut strut strut strut strut according according according according according cross sectional diagrams of a to to to to to an an an an an embodiment of the embodiment of the embodiment of the embodiment of the embodiment of the metering pin of a shock absorbing strut according to an embodiment of the invention. Detailed Description Figure 1 is a diagram of an aircraft 2. The aircraft includes assemblies such as a nose landing gear 4 and a pair of main landing gear 6. The landing gear 4, 6 each includes a shock absorber strut for damping landing loads and supporting the weight of the aircraft 2 when it is on the ground. The term aircraft as used herein can include aeroplanes, helicopters and the like having mass in excess of 450kg. Figure 2 is an example of an aircraft landing gear assembly 6 which can include a shock absorber strut according to an embodiment of the invention. It will however be appreciated that shock absorber struts according to embodiments of the invention can be used in a range of types of aircraft landing gear including main landing gear and nose landing gear, with one or more axles and include wheels or other ground contacting means. In some embodiments the shock absorber according to embodiments of the invention can for example form part of a "capsule type" shock absorber strut, where the shock absorber is hinged at both ends and provides shock absorbing functionality to the load bearing elements of the strut. The aircraft landing gear assembly 6 is movable between a deployed condition, for take-off and landing, and a stowed condition for flight. The landing gear assembly includes a main shock absorber strut 8, comprising an outer cylinder and a sliding tube, a foldable stay 14, and a lock link 20. An upper end of the strut 8 is provided with a bearing 9 via which the strut 8 is pivotally coupled to the airframe of the aircraft 2. A lower end of the strut 8 is provided with a wheel and brake assembly 30. A retraction actuator 12 is provided for moving the landing gear between the deployed condition and the stowed condition. The retraction actuator can have one end coupled to the airframe 11 and another end coupled to the strut 8. The stay 16 serves to support the orientation of the strut 8 when the landing gear is in the deployed condition. The stay 18 generally includes a two-bar linkage 16, 18 that can be unfolded to assume a generally straight or aligned, over centre condition in which the stay 18 is locked to inhibit movement of the outer cylinder, as shown in Figure 2. When the stay is broken, it no longer inhibits pivotal movement of the strut 8 about the mounting bearing and strut 8 can be moved by the retraction actuator 12 towards the stowed condition. The lock link 20 has an elongate upper link arm having a lower end pivotally coupled to an upper end of an elongate lower link arm via a pivot pin. The link arms can therefore pivotally move relative to one another about the pivot pin. The lock link is pivotally coupled to the strut 8 and one of the stay arms 16. When the lock link 20 is in the locked condition, as shown in Figure 2, the upper and lower link arms are generally longitudinally aligned or coaxial, and can be 'over-centre', such that the lock link 20 is arranged to oppose a force attempting to break or fold the stay 14. The lock link 20 must be broken to enable the stay 14 to be broken and folded, thereby permitting the strut 6 to be moved by the retraction actuator 12 towards the stowed condition. The down lock assist in moving the landing gear assembly to the deployed condition and locking it in that state by making the lock link 20. Down lock springs also inhibit the lock link 20 accidentally being broken / unlocked. A lock stay actuator 22 is coupled between the stay 14 and lock link 20 and arranged to pivotally move the link arms so as to make and break the lock link 20. The lock stay actuator 22 can break the lock link 20 against the down lock spring bias, allowing the landing gear assembly to be folded and stowed as described previously. Referring additionally to Figure 3, the outer cylinder 24 and sliding tube 26 of the shock absorber strut 8 can be coupled via a set of torque links 28 which permit relative axial movement but inhibit relative rotational movement between the outer cylinder 24 and sliding tube 26. Wheel and brake assemblies 10 can be mounted on axles 30 which in turn are mounted at end regions of a bogie beam 32. The bogie beam 32 is pivotally coupled near its centre to the sliding tube 26 via a bogie pivot pin 34. Brake rods 35 can be provided to anchor the brake packs to the sliding tube 26 to react brake torque. Figures 4a and 4b are diagrams of the internal arrangement of the shock absorber strut 8, illustrating axial flow of damping liquid during compression of the shock absorber strut 8. The outer cylinder 26 has an inner surface 26a defining a cylinder bore B extending into the outer cylinder from a first axial face 26b of the outer cylinder 26. The cylinder 26 is elongate and in this example is of circular cross section. A sliding tube 28 is movably mounted within the cylinder bore B so as to be movable along the cylinder bore B between a compressed position in which a first free end portion 28a of the sliding tube 28 disposed outside of the bore B is relatively close to the first axial face 26b of the outer cylinder 26 and an extended position in which the first free end portion 28a of the sliding tube 28 is relatively far from the first axial face 26b of the outer cylinder 26. An upper bearing 30 is mounted near the inner end 28b of the sliding tube 28 to slide against the inner surface 26a defining the bore B. The lower end of the cylinder 26 can be provided with a lower bearing assembly sleeve insert 32 to define a lower bearing arranged to act on the outer surface 28c of the sliding tube 28 as it moves between the compressed and extended positions. A gland nut (not shown) can be screwed into the end of the bore to retain the lower bearing assembly 32. However, in other embodiments, any suitable bearing assembly can be utilised; for example, the upper bearing can be mounted on the cylinder 26 and arranged to act on the sliding tube 28. A space within the bore B between the cylinder 26 and sliding tube 28 defines an annular volume which varies in size as the sliding tube 28 moves between the compressed and extended positions. One or more dynamic seals (not shown) are arranged within the cylinder bore B between the inner surface of the outer cylinder 26 and an outer surface of the sliding tube 28 to inhibit hydraulic liquid within shock absorber passing the dynamic seals as the sliding tube 28 moves between the extended and compressed positions. In this example, the dynamic seals are mounted on the lower bearing sleeve assembly 32. The sliding tube defines a bore B2 which extends into the sliding tube 28 and is in fluid communication with cylinder bore B. The cylinder bore B and sliding tube bore B2 together define an oleo pneumatic chamber containing a hydraulic liquid L such as oil and a gas G such as nitrogen. The oleo pneumatic chamber is unseparated, meaning that the liquid L is free to mix with the gas G. An elongate metering pin 34 is provided and configured to work with a mating damping orifice DO to provide variable damping based on the extension state of the strut 50. The metering pin 34 has a longitudinal axis which is coaxial with the axis of the bore B. The metering pin 34 is mounted in the sliding tube bore B2 and coupled to the sliding tube 28 to move with the sliding tube 28. A mating damping orifice DO is formed through a flow restricting plate 36 extending across the sliding tube bore B2 and coupled to the outer cylinder 26 by an orifice support tube 38. As such, the metering pin 34 axially moves through the mating damping orifice DO as the sliding tube 28 moves between the extended and compressed positions. 'Unseparated' or 'wet' shock absorbers, where the gas and hydraulic liquid are free to mix, can have a lower gas index on dynamic closure compared with 'separated' or 'dry' shock absorbers, due to the hydraulic liquid cooling the gas. Instead of a pure adiabatic index of y = 1.4 in PV7 or the typical y = 1.3 found with 'dry' shock absorbers a value of y = 1.1 is common and may be even lower if hydraulic liquid jets J squirting through orifices further mix oil and gas on closure, causing quenching of the gas. This can affect the increase in pressure and load reaction of the landing gear upon rapid closure, and jetting tends to result in oil foaming, becoming less effective at damping than unaerated oil. Furthermore, the jetting and foaming effects can result in a change of shock absorber characteristics over repeated landings or rough taxiing, leading to inconsistency in operation. Referring additionally to Figure 4c, it is common practice to use either a fluted or a tapered metering pin through a central orifice in order to vary the orifice area according to shock absorber closure. A 'fluted' pin has a cylindrical outer surface CO with grooves G of varying size (e.g. depth) along the metering pin 34 to vary the flow area as the metering pin 34 passes through the orifice DO. Oil passing through the metering pin orifice or flutes will tend to jet upwards, as illustrated by arrows J in Figure 4b. Figure 5 is a diagram of an aircraft landing gear assembly shock absorber strut 50 according to an embodiment of the invention. By way of a non-limiting overview, shock absorber struts according to embodiments of the invention include a second damping orifice orientated to direct a second flow of damping liquid towards the axial channel of the metering pin to disrupt the axial flow of damping liquid along the channel; as such, embodiments of the invention are arranged to deflect or disrupt the axial liquid jet emerging from the metering pin orifice. The shock absorbing strut 50 is similar to the shock absorbing strut 8 as illustrated in figures 4A and 4B, and for brevity, the following description will focus on the differences. In the illustrated embodiment, the damping diaphragm or flow restricting plate 52 include includes a first portion 52a, through which the first damping orifice DO extends, and a second portion, 52b, through which a second damping orifice DO2 extends. The first portion 52a and second portion 52b are parallel and coplanar, being formed by a single plate. The second damping orifice DO2 orientated to direct a second flow of damping liquid J2 towards the axial channel AC of the metering pin 34 to disrupt the axial flow of damping liquid J along the channel AC. The second flow of damping liquid J2 can disrupt the axial flow of damping liquid J by mixing or by causing it to strike sidewalls before reaching the oil-gas interface surface I. The second damping orifice DO2 is orientated such that its axis A2 is arranged at an angle a of approximately 45 degrees with respect to the axis A of the metering pin 34 and first damping orifice. In other embodiments, the axis A2 of the second damping orifice DO2 can be at an angle of at least 15 degrees with respect to the axis A of the first damping orifice DO; for example, the axis A2 of the second damping orifice DO2 can be arranged at an angle of between 15 degrees and 90 degrees with respect to the axis A of the first damping orifice DO. If an angled drilling passes through a 'horizontal' orifice plate at the bottom of the orifice support tube, then it will form an elliptical shape where it intersects with the plate surface. Elliptical orifices are not preferred since they are less predictable than circular orifices. The second damping orifice DO2 is therefore provided with outlet DO2a of a first diameter and includes a central portion DO2b of reduced diameter with respect to the outlet. As such, the second damping orifice DO2 addresses this problem by setting the working orifice diameter DO2b at the bottom of a larger counterbore DO2a. Two such counterbores DO2a, DO2c, one each side, are preferable so that the second damping orifice DO2 can control flow in both directions. In any embodiment, the working orifice diameter of the second damping orifice DO2 (which in some embodiments can describe the full orifice length) can be 2mm to 20 mm, in some embodiments 5mm to 10 mm diameter. I should however be noted that a wide range of diameters can be utilised depending upon for example the size of landing gear, damping requirements and numbers of orifices provided. Referring now to Figure 6, a shock absorbing strut 60 according to an embodiment of the invention is shown. The shock absorbing strut 60 is similar to the shock absorbing strut 50 of Figure 5, and for brevity, the following description will focus on the differences. In this embodiment, the end of the orifice support tube which defines the flow restricting plate 62 is formed in a generally conical form or the like. As such, the second portion 62b of the flow restricting plate 62 is arranged at an angle P with respect to the first portion 62a. As such, the first portion 62a and second portion 62b are not parallel. In view of this, the second damping orifice DO2 can extend through the second portion 62b generally perpendicular of normal to the surface so that either the counterbore is not required or that a reduced counterbore length may be used. In other embodiments, the second damping orifice DO2 can be provided though a cylindrical section such that its flow J2 is at or near 90 degrees to the metering pin axial jet J. Referring now to Figure 7, a shock absorbing strut 70 according to an embodiment of the invention is shown. The shock absorbing strut 70 is similar to the shock absorbing strut 60 of Figure 6, and for brevity, the following description will focus on the differences. In this embodiment, a baffle plate 74 extends across the inside of the orifice support tube 72 so that the metering pin axial jet J is deflected to strike the baffle plate 74. The baffle plate 74 can have a plurality of holes H of larger total area then the orifice(s) DO2, either axial or angled or further baffled, such that the fluid passing above the baffle is diffused and jetting is stopped or reduced. Referring now to Figure 8, a shock absorbing strut 80 according to an embodiment of the invention is shown. The shock absorbing strut 80 is similar to the shock absorbing strut 60 of Figure 6, and for brevity, the following description will focus on the differences. In this embodiment, the shock absorbing strut is arranged such that the metering pin jet is deflected onto a curved surface CS to be further deflected due to the Coanda effect. The curved surface CS can be arranged to direct the disrupted axial flow of damping liquid to a fluid passage hole H2 through the orifice support tube 82. Referring now to Figure 9, a shock absorbing strut 90 according to an embodiment of the invention is shown. The shock absorbing strut 90 is similar to the shock absorbing strut 80 of Figure 8, and for brevity, the following description will focus on the differences. In this embodiment, the metering pin jet is deflected onto one or more vanes V to further deflect the jet. The vane V is defined by a tube and can have further features or shape to help diffuse the jet. Such features may include a widening section (smoothly or in steps) to reduce the velocity of the fluid flow, or else may include projections, steps and the like in order to dissipate the fluid jet energy in turbulence where the turbulence is safely below the oil-gas surface I. Referring now to Figures 10a and 10b, in order that the angled orifice jet J2 can effectively impinge on the metering pin flute jet J, the shape of the metering pin flutes in any embodiment can be selected to be more of a flat than a channel. As illustrated, the metering pin 100 has a circular cross section and the axial channel AC has a base defined by a chord Cl of the circular cross section, such that the axial channel AC has open sides to enable the second flow of damping liquid J2 from second damping orifice DO2 to disrupt the axial flow of damping liquid moving along the channel AC. Thus, flutes can be arranged as flat sections of varying depth. This can have an advantage that an impinging oil jet with a transverse vector component can flow across the face. In this example, the metering pin 100 has a second axial channel AC2 with a base defined by a chord C2 on the diametrically opposite side of the pin 100 and a third damping orifice DO3 arranged to direct a third flow of damping liquid J3 to disrupt an axial flow of damping liquid moving along the second axial channel AC2. In any embodiment, the metering pin can include a single flute or multiple flutes. In any embodiment, one or more angled orifices can be provided and some or all of the orifices can be linear or generally linear in nature. Preferably a plurality of flutes are provided, with a plurality of angled orifices, preferably one per flute. A plurality of flutes allows them to be spaced evenly around the metering pin to avoid or reduce unbalanced flow or forces. In any embodiment, one or more conventional non-angled orifices can also be provided for damping. In any embodiment, the cylindrical surface of the metering pin can be in contact with the bore of the first damping orifice DO or it can have a slight clearance. It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be capable of designing many alternative embodiments without departing from the scope of the invention as defined by the appended claims. In the claims, any reference signs placed in parenthesis shall not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps other than those listed in any claim or the specification as a whole. The singular reference of an element does not exclude the plural reference of such elements and vice-versa. Parts of the invention can be implemented by means of hardware comprising several distinct elements. In a device claim enumerating several parts, several of these parts can be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. An aircraft landing gear shock absorber strut comprising:an outer cylinder having an inner surface defining a cylinder bore extending into the outer cylinder from a first axial face of the outer cylinder, the cylinder bore defining an oleo-pneumatic chamber containing a damping liquid and a gas which can mix within the cylinder bore;a sliding tube including a first end portion movably mounted within the cylinder bore so as to be movable along the cylinder bore between a compressed position, in which a second end portion of the sliding tube disposed outside of the bore is relatively close to the first axial face of the outer cylinder, and an extended position, in which the second end portion of the sliding tube is relatively far from the first axial face of the outer cylinder, the sliding tube including a tube bore extending into the sliding tube from the first end portion, the tube bore being arranged in fluid communication with the cylinder bore to exchange the damping liquid with the cylinder bore;an elongate metering pin having a longitudinal axis and including an axial channel for passage of damping liquid as the sliding tube moves from the extended position towards the compressed position; anda flow restricting plate including:a first portion provided with a first damping orifice in which the metering pin is located and through which the metering pin axially moves as the sliding tube moves between the extended and compressed positions to vary the free space cross sectional area of the first damping orifice to control an axial flow of the damping liquid moving from the tube bore to the cylinder bore as the sliding tube moves from the extended position towards the compressed position; anda second portion provided with a second damping orifice for passage of damping liquid as the sliding tube moves from the extended position towards the compressed position to define a second flow of the damping liquid, wherein the second damping orifice is orientated to direct the second flow of damping liquid towards the axial channel of the metering pin to disrupt the axial flow of damping liquid.

2. The aircraft landing gear shock absorber strut according to claim 1, wherein the axis of the second damping orifice is at an angle of at least 15 degrees with respect to the axis of the first damping orifice.

3. The aircraft landing gear shock absorber strut according to claim 2, wherein the axis of the second damping orifice is at an angle of 15 degrees to 90 degrees with respect to the axis of the first damping orifice.

4. The aircraft landing gear shock absorber strut according to any preceding claim, wherein the flow restricting plate is defined by an end portion of an orifice support tube, the office support tube being coupled to the outer cylinder to maintain the flow restricting plate at a fixed distance from a second axial face of the outer cylinder, the orifice support tube having a sidewall provided with a plurality of fluid passage holes.

5. The aircraft landing gear shock absorber strut according to any preceding claim, wherein the metering pin has a circular cross section and the axial channel has a base defined by a chord of the circular cross section, such that the axial channel has open sides to enable the second flow of damping liquid to disrupt the axial flow of damping liquid moving along the channel.

6. The aircraft landing gear shock absorber strut according to any preceding claim, wherein the first portion and the second portion of the flow restricting plate are parallel and the second orifice has an inlet and outlet of a first diameter and includes a central portion of reduced diameter with respect to the inlet and outlet.

7. The aircraft landing gear shock absorber strut according to any of claims 1 to 5, wherein the second portion of the flow restricting plate is non-parallel with respect to the first portion and the axis of the second orifice is normal with respect to the second portion.

8. The aircraft landing gear shock absorber strut according to any preceding claim, further comprising a baffle plate including a plurality of axial fluid passages and positioned in a fixed relationship with respect to the flow restricting plate such that the axial flow of damping liquid strikes the baffle plate once disrupted by the second flow of damping liquid.

9. The aircraft landing gear shock absorber strut according to any preceding claim when dependent on claim 4, wherein the orifice support tube comprises a curved surface positioned in a fixed relationship with respect to the flow restricting plate such that the axial flow of damping liquid strikes the curved surface once disrupted by thesecond flow of damping liquid, the curved surface being curved away from the axis of the metering pin to diffuse the disrupted axial flow of damping liquid.

10. The aircraft landing gear shock absorber strut according to claim 9, wherein the curved surface directs the disrupted axial flow of damping liquid to a fluid passage hole through the orifice support tube.

11. The aircraft landing gear shock absorber strut according to claim 9 or claim 10, wherein the curved surface is defined as a vane and optionally the vane is defined by a tube.

12. The aircraft landing gear shock absorber strut according to claim 11, wherein the tube widens away from the metering pin to reduce the velocity of the fluid flow and / or includes projections extending into the tube in order to dissipate the fluid jet energy in turbulence.

13. The aircraft landing gear shock absorber strut according to any preceding claim, wherein the flow restricting plate includes one or more further portions each provided with a further damping orifice for passage of damping liquid as the sliding tube moves from the extended position towards the compressed position to define a further flow of the damping liquid, each further damping orifice being orientated to direct the further flow of damping liquid towards the or a further axial channel of the metering pin to disrupt the or a further axial flow of damping liquid.

14. An aircraft landing gear assembly comprising:the aircraft landing gear shock absorber strut according to any preceding claim;a wheel or other ground contacting assembly coupled to the shock absorber strut; anda mounting bearing via which the aircraft landing gear assembly is arranged to be movably coupled to an aircraft for movement between a stowed condition for flight and a deployed condition for take-off and landing.

15. The aircraft landing gear assembly according to claim 14, further comprising a side stay, drag stay or plunger lock arrangement coupled to the shock absorber strut and arranged to enable the shock absorber strut to be maintained in the deployed condition.

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