Airplane landing gear shock absorber, airplane landing gear, airplane and related methods

Abstract

An aircraft landing gear shock absorber, aircraft landing gear, aircraft and related methods are disclosed. The shock absorber includes a stop surface (44) arranged to limit extension of the shock absorber (6) and a crimped element (48) configured to deform if an extension load on the stop surface (44) exceeds a predetermined threshold. The crimped element (48) can form part of an outer stop tube (46) of the shock absorber (6). Deformation of the crimped element (48) can be identified by measuring the length of the fully extended landing gear by non-destructive testing or by measuring a change in the conductivity of the crimped element (48).

Description

Technical Field

[0001] This disclosure relates to aircraft landing gear shock absorbers. More particularly, but not exclusively, the aircraft landing gear shock absorbers of the present invention include corrugated elements. The present invention also relates to landing gear including such shock absorbers, aircraft including such landing gear, and methods for using such shock absorbers to detect excessive landing gear loads. Background Technology

[0002] Aircraft landing gear can have shock absorbers configured to dampen the movement of a wheel. Typically, such a shock absorber includes a piston mounted in a cylinder and at least one stop configured to limit the extension of the shock absorber and thereby retain the piston within the cylinder. The shock absorber is compressed by the weight of the aircraft when the wheel contacts the ground. When the weight of the aircraft disengages from the wheel, for example during takeoff, the wheel descends, causing the shock absorber to extend until the stop further prevents any further movement. The load generated on the stop when it prevents further extension can be referred to as an extension (or external stop) load. It will be understood that these extension loads can be transferred to the rest of the shock absorber. Considering the weight of the wheel and other wheel-related components of the landing gear (e.g., axles, bogies, brakes, and other components), these extension loads can be significant and constitute the ultimate load condition for designing the shock absorber. That is, the shape, size, and configuration of the various components of the shock absorber can be determined by the need to withstand these extension loads. Some aircraft shock absorbers may include a rebound element to dampen the extension of the shock absorber, thereby reducing the maximum extension load generated by the downward movement of the wheels. However, this rebound element typically provides energy through the compression of the shock absorber and may therefore fail to function when the shock absorber is only partially compressed or compressed for only a short period of time, such as when the aircraft is performing a 'touch-and-go' maneuver or aborting a landing. In the event of a malfunction, this rebound element may also fail to dampen extension. If the rebound element fails to function as intended, the extension load experienced by the shock absorber may exceed the extension load it was designed for (design extension load). This can be referred to as an extension event.

[0003] Current practice involves inspecting shock absorbers after events that may have caused the extended load to exceed the design maximum (e.g., aborted takeoff, 'touch-and-go', or other events). It would be advantageous to provide a device that indicates whether the shock absorber has been subjected to a load exceeding its design extended load, thereby minimizing the need for such inspections.

[0004] Inspection of shock absorbers typically requires jacking up the aircraft to reduce the load on the landing gear wheels and removing the piston from the cylinder block to allow inspection of internal components. This is an expensive and time-consuming process. It would be advantageous to provide a device that can identify whether a shock absorber has been subjected to loads exceeding its design extension without requiring disassembly.

[0005] The present invention seeks to alleviate the aforementioned problems. Alternatively or additionally, the present invention seeks to provide improved aircraft landing gear shock absorbers and / or improved methods for operating aircraft landing gear shock absorbers. Summary of the Invention

[0006] According to a first aspect, the present invention provides an aircraft landing gear shock absorber. The shock absorber may include a stop surface. The stop surface may be arranged to limit the extension of the shock absorber. The shock absorber may include a folding element, for example, a folding element configured to deform when the extension load on the stop surface exceeds a predetermined threshold. Therefore, the deformation of the folding element can be used as an indication that the landing gear, to which the folding element forms a portion, has experienced an event where the extension load exceeds the predetermined threshold (an extension event). The use of the folding element facilitates the detection and / or confirmation of the extension event without requiring the removal of the shock absorber and / or the landing gear to which the shock absorber forms a portion.

[0007] A pleated element can be defined as a component or a region thereof configured to deform, for example, compact, buckle, and / or fold, when subjected to a load exceeding a predetermined threshold. A pleated element can be configured to undergo plastic deformation when subjected to a load exceeding a predetermined threshold. The properties of the pleated element, such as its geometry, material, and / or structure, can differ from the remainder of the structural member arranged along the load path between the stop surface and the pleated element, such that the pleated element deforms under a lower extension load (e.g., a predetermined threshold) than the remainder of the structural member arranged along the load path. The predetermined threshold can be a design extension load.

[0008] When the wrinkle element is a region of a component, the properties of the wrinkle element, such as geometry, material, and / or structure, may differ from those of the rest of the component, causing the wrinkle element to deform under lower elongation loads than the rest of the component. When the wrinkle element is a separate component, the properties of the wrinkle element, such as geometry, material, and / or structure, may differ from those of adjacent components and / or other components on the load path between the stop surface and the wrinkle element and / or between the stop surface and the cylinder block, causing the wrinkle element to deform under lower elongation loads than said other components. Therefore, the wrinkle element may be a region in the component and / or on the load path with a planned weakness, through which the elongation load experienced by the stop surface is responded. The wrinkle element may be made of a material different from that of the rest of the component and / or other components on the load path, such as a material with a lower Young's modulus. The wrinkle element may have a geometry different from that of the rest of the component and / or other components on the load path, such as a reduced cross-sectional area or a reduced thickness. The pleated element may have a structure different from the rest of the component and / or other components on the load path. For example, the pleated element may include one or more folds, recesses and / or through holes.

[0009] The pleated element can be located on the load path through which the extended load experienced by the stop surface is responded. The pleated element can be connected to the stop surface such that the extended load experienced by the stop surface ( wholly or partially) is transferred to the pleated element, optionally via one or more intermediate components.

[0010] A shock absorber may include a piston assembly comprising a piston (also referred to as an inner tube). The piston (and piston assembly) may be mounted to move relative to a cylinder (also referred to as an outer tube and not necessarily cylindrical in form). The piston (and piston assembly) may be mounted to move between a compression configuration and an extension configuration. Extension of the shock absorber may include movement of the piston (and piston assembly) relative to the cylinder in a first direction such that the length of the shock absorber increases. Compression of the shock absorber may include movement of the piston (and piston assembly) relative to the cylinder in an opposite second direction such that the length of the shock absorber decreases. The shock absorber may be configured such that a stop surface limits the extension of the shock absorber by preventing further movement of the piston (and piston assembly) in the first direction. The shock absorber may be configured such that the stop surface contacts the piston assembly in an abutting relationship to prevent further extension of the shock absorber. The length of the shock absorber beyond which further extension is prevented by the stop surface may be referred to as the maximum extension length. At least a portion of the piston (and piston assembly) may be received within the cylinder.

[0011] The shock absorber can be configured such that deformation of the pleated element under an extension load exceeding a predetermined threshold causes a change, for example, an increase, in the length of the shock absorber at its maximum extension. In this way, confirmation and / or detection of an extension event can be achieved by measuring the length of the shock absorber at its maximum extension; the change in shock absorber length provides an indication that the pleated element has deformed and that the shock absorber and / or the landing gear formed by the shock absorber has undergone an extension event. This shock absorber allows for the detection and / or confirmation of an extension event without requiring the removal of the shock absorber and / or the landing gear formed by the shock absorber. The pleated element can be configured such that its length decreases when the extension load exceeds a predetermined threshold. The length of the pleated element can be its maximum dimension in the direction parallel to the piston's direction of movement relative to the cylinder block. The length of the landing gear can vary between 1 mm and 5 mm, for example, between 2 mm and 4 mm, in the event of an extension event. This change in length is sufficient to be detectable without excessive effort, while allowing the landing gear to continue operating safely.

[0012] The cylinder block may have a first end and an optional second end opposite to the first end. A stop surface may be spaced apart from the first end of the cylinder block, for example, spaced apart from the first end of the cylinder block along an axis of the shock absorber parallel to the direction of piston movement relative to the cylinder block. A pleated element may be located between the first end and the stop surface (e.g., the first end, the pleated element, and the stop surface are spaced apart in this order along the length of the cylinder block) such that deformation of the pleated element reduces the distance between the first end and the stop surface, thereby resulting in an increase in the length of the shock absorber at its maximum extension. Thus, the first end and the stop surface may be spaced apart by a first distance before deformation of the pleated element and by a smaller second distance after deformation of the pleated element.

[0013] A stop surface can be mounted on the cylinder block such that a load path extends between the stop surface and the cylinder block, through which the extended load on the stop surface is transferred (at least partially) to the cylinder block. A pleated element can be located on the load path.

[0014] The shock absorber may include a stop, for example, mounted thereon, mounted in the cylinder body, and / or on the cylinder body. The stop may include a stop surface.

[0015] The shock absorber may include a sleeve (which may be referred to as an outer stop sleeve) mounted in and / or on the cylinder body. The sleeve may include a stop surface. The stop surface may be formed by a first end of the sleeve, such as the end of the sleeve furthest from the first end of the cylinder body. Therefore, the piston assembly may abut against the sleeve, such as the first end of the sleeve, when the shock absorber is at maximum extension. The load path between the stop surface and the cylinder body may extend through the sleeve. The sleeve may extend around the exterior of the piston, such as the outer periphery of the piston, in whole or in part. The sleeve may be a tubular member. The sleeve may be mounted concentrically with the cylinder body and / or piston. The sleeve may be installed between the cylinder body and the piston.

[0016] The piston assembly may include a piston bearing, for example, in a region of the piston's end located within the cylinder body. The piston bearing may contact a stop surface when the damper is at maximum extension. The cylinder body may include a cylinder body bearing, for example, in a region of a first end of the cylinder body. The sleeve may have a second end opposite to the first end. The second end of the sleeve may abut against the cylinder body bearing, for example, such that the sleeve is held within the cylinder body by the cylinder body bearing. The cylinder body bearing may be located on the load path between the stop surface and the cylinder body, for example, the load path may terminate at the cylinder body bearing. The sleeve may include a pleated element. Forming a pleated element within the sleeve allows for the detection and / or confirmation of extension events without requiring any additional components in the damper and / or in a mechanically simple manner. The pleated element may include a region of the sleeve with different properties (e.g., geometry, material, and / or structure) than the rest of the sleeve, such that the pleated element deforms under lower loads than the rest of the sleeve.

[0017] Shock absorbers can be hydraulic struts. Hydraulic struts can be defined as hydraulic shock absorbers that use a mixture of gas and liquid, such as air and oil. Such struts are well known in the landing gear industry.

[0018] The crease element can be located within the shock absorber, such as within the cylinder body, so that the crease element (and / or deformation of the element) is not visible during normal use. Therefore, no visible indication of extended events can be provided.

[0019] According to a second aspect of the invention, a landing gear is also provided, which includes an aircraft landing gear shock absorber according to the first aspect or any other aspect.

[0020] The landing gear may include a main assembly and a main strut (or landing gear leg) mounted to move relative to the main assembly. Shock absorbers may be arranged to dampen the movement of the main strut relative to the main assembly. The main assembly may include a cylinder block. The main strut may include a piston.

[0021] The landing gear may include one or more wheels mounted to the distal end of the main strut. The landing gear may include one or more axles and / or bogies, with one or more wheels mounted on the main strut via the one or more axles and / or bogies.

[0022] The landing gear and / or actuators may include one or more sensors configured to detect changes in the length of the landing gear and / or actuators due to deformation of the folding elements. For example, the landing gear may include at least one proximity sensor and at least one target. The landing gear may be configured such that deformation of the shock absorber causes the proximity sensor and the target to move closer or further away, such that signals from the sensors provide an indication of a change in the length of the shock absorber.

[0023] According to a third aspect of the invention, an aircraft is also provided, the aircraft comprising an aircraft landing gear shock absorber according to the first aspect or any other aspect and / or a landing gear according to the second aspect or any other aspect.

[0024] The aircraft can be a commercial passenger aircraft, for example, an aircraft configured to carry more than fifty passengers, such as more than one hundred passengers. The aircraft can be a fixed-wing aircraft. The landing gear can be wing-mounted landing gear (i.e., wholly or partially mounted to the wings of the aircraft), fuselage-mounted landing gear (i.e., wholly or partially mounted to the fuselage of the landing gear), and / or nose landing gear (e.g., steerable landing gear). The landing gear can be retractable landing gear.

[0025] The aircraft may include a control system configured to provide instructions to the pilot upon detection of a change in the length of the landing gear, such as when a sensor, such as a proximity sensor, indicates that a change in length has occurred.

[0026] According to a fourth aspect of the invention, an aircraft landing gear having a hydraulic strut is provided. The hydraulic strut may include one or more of a cylinder, a piston mounted within the cylinder, and an outer stop tube mounted within the cylinder. The piston and the outer stop tube may be in an abutting relationship when the hydraulic strut is in an extended configuration, thereby preventing further extension of the hydraulic strut. The outer stop tube may include a pleated element configured to deform under a lower extension load than the rest of the outer stop tube.

[0027] According to a fifth aspect of the invention, a method is provided for determining whether an aircraft landing gear has experienced an extension event. The landing gear may include a shock absorber having a corrugated element. An extension event may be defined as an extension load generated when the shock absorber reaches a maximum extension exceeding a predetermined threshold (e.g., a design maximum value). The method may include determining whether the corrugated element has deformed, and determining whether an extension event has occurred based on whether the corrugated element has deformed. For example, the method may include: determining that an extension event has occurred if the corrugated element has deformed and / or determining that an extension event has not occurred if the corrugated element has not deformed.

[0028] In the event of an extension event, the pleated element may deform when the extension load exceeds a predetermined threshold, but the rest of the shock absorber (and / or the parts in which the pleated element forms a part) does not deform.

[0029] The length of the crease element can be varied, for example, reduced when the extended load exceeds a predetermined threshold. Deformation of the crease element can cause a change in the length of the landing gear when it is at maximum extension. Therefore, determining whether the crease element has deformed can include determining whether the length of the landing gear has changed relative to its original or design length, for example, increased. The method can include measuring the landing gear to determine whether the length of the landing gear at maximum extension has increased. The method can include measuring the total length of the landing gear and / or the distance between a first reference point (e.g., on the cylinder block) and a second reference point (e.g., on the piston). The method can include measuring the landing gear at maximum extension, for example, when there is no aircraft weight on the wheels and / or when the piston (or piston assembly) abuts a stop surface. The method can include removing the weight of the aircraft from the wheels, for example, by jacking up the aircraft or by taking off, and then measuring the landing gear. The method can include one or more sensors, such as the proximity sensors described above, to provide information related to the length of the landing gear at maximum extension, for example, signals indicating a change in the length of the landing gear. The method may include a control system that processes signals from one or more sensors and provides the aircraft's pilot with an indication (e.g., an audible or visual signal) that the landing gear may have experienced an extension event if the signals indicate that the landing gear length has changed.

[0030] Determining whether a creased element has deformed may involve using non-destructive testing and / or imaging techniques, such as ultrasound or X-rays, to determine if the shape of the creased element has changed. If the shape has changed, this can be considered an indication that an extension event has occurred. Non-destructive testing / imaging can be a quick and / or cost-effective way to determine if the landing gear has undergone an extension event and / or avoid the need to measure the landing gear when it is fully extended (i.e., under wheel load) and / or to disassemble the landing gear.

[0031] Determining whether a folded element has deformed may include measuring the (electrical) conductivity of the folded element. If the conductivity has changed, for example, by more than a predetermined amount, this can be considered an indication that an extension event has occurred. This may include measuring one or more of the current flowing through the folded element or a component formed by the folded element and / or the shock absorber and / or the landing gear, the voltage across its terminals, and / or the resistance. Measuring the conductivity of the folded element (or a portion of the load path that includes the folded element) can be a quick and / or cost-effective way to determine whether the landing gear has experienced an extension event and / or avoid the need to measure the landing gear when it is fully extended (i.e., under wheel load) and / or the need to disassemble the landing gear.

[0032] This method can occur at predetermined intervals, for example, as part of a routine maintenance plan. Additionally or alternatively, this method can be performed after a suspected extended event, such as an aborted landing or takeoff.

[0033] Of course, it will be understood that features described with respect to one aspect of the invention may be incorporated into other aspects of the invention. For example, the method of the invention may incorporate any of the features described with reference to the apparatus of the invention, and the apparatus of the invention may incorporate any of the features described with reference to the method of the invention. Attached Figure Description

[0034] Embodiments of the invention will now be described by way of example only with reference to the accompanying schematic diagrams, in which:

[0035] Figure 1 A front view of an aircraft according to a first embodiment of the present invention is shown;

[0036] Figure 2 It shows Figure 1 An enlarged view of a part of the landing gear;

[0037] Figures 3(a) and 3(b) show Figure 1 Figure 3(a) shows the landing gear in compression and Figure 3(b) shows the landing gear in extension.

[0038] Figures 4(a) and 4(b) show schematic enlarged cross-sectional views of the height of a portion of the landing gear before the extension event in Figure 3(a) and after the extension event in Figure 3(b); and

[0039] Figure 5 An example method according to the present invention is shown. Detailed Implementation

[0040] Figure 1An aircraft 1 with two wings 2 is shown, each wing having a landing gear 4 mounted thereon. Although Figure 1 The landing gear 4 is shown mounted on the wing, but in other embodiments, the landing gear may be a nose landing gear or may be mounted on the fuselage of the aircraft.

[0041] Figure 2 It shows Figure 1 An enlarged view of a portion of the landing gear 4. The landing gear 4 includes a shock absorber 6 having a cylinder 8 and a piston 10. A shaft 12 is mounted at the distal end of the piston 10. A pair of wheels 14 are mounted on the shaft 12. The shock absorber 6 can be a fluid spring shock absorber, such as a hydraulic strut (i.e., an air-oil shock absorber), an oil-filled shock absorber, a pneumatic shock absorber, a solid spring shock absorber, or other types of shock absorbers.

[0042] Figure 3(a) shows Figure 1The landing gear 4 is shown in a cross-sectional view, for example, a portion of the aircraft 1 in a compressed configuration during taxiing. A piston 10 is concentrically mounted within a cylinder 8 in the form of a tube. A piston bearing 20 is mounted to the exterior of the upper end of the piston 10 and extends around the exterior of the upper end of the piston 10. A slider 22 is mounted within the piston 10 and partially along the piston 10, and the slider 22 includes a metering rod 24 (an elongated member with a varying cross-section) concentric with the cylinder 8 extending upward into an orifice tube 26. The lower end of the slider 22 includes an end portion 36 that extends across the interior of the piston 10 to form a storage portion 34 within the piston above the end portion 36. The orifice tube 26 is concentrically mounted with the cylinder 8 and the piston 10, and the orifice tube 26 includes a plurality of orifices 28. The orifice tube 26 divides the volume within the cylinder 8 into an inner chamber 30 (located inside the orifice tube 26 and having a metering rod 24 extending therein in FIG. 3(a)) and an outer chamber 33 (located outside the orifice tube 26). The piston bearing 20 has a plurality of damping orifices (not shown) formed therein, extending axially from the top side to the bottom side of the piston bearing 20, thereby providing fluid communication between the outer chamber 33 and a spring-loaded chamber 32 formed below the piston bearing 20 between the cylinder 8 and the piston 10. An orifice plate 38 extends across the bottom of the orifice tube 26 and has a main orifice 40 formed therein. The metering rod 24 of the slider 22 extends through the main orifice 40, with its end portion 36 located below the orifice plate 38 and thus outside the inner chamber 30. The outer stop tube 46 is positioned concentrically with the cylinder body 8 and the piston 10 and positioned between the cylinder body 8 and the piston 10 (in the springback chamber 32). The outer stop tube 46 extends from directly below the orifice plate toward the lower end of the cylinder body 8, where it abuts against the cylinder body bearing 42, which is mounted inside the cylinder body 8 and attached to the lower end of the cylinder body 8. A stop surface 44 is formed at the top of the outer stop tube 46.

[0043] Figure 3(b) shows the landing gear of Figure 3(a) in an extended configuration during normal operation, such as after takeoff. Compared to Figure 3(a), the piston 10, including the slider 22, has moved downward until the piston bearing 20 abuts against the stop surface 44 of the outer stop tube 46. The distal end of the metering rod 24 is located in the main orifice 40, but does not extend significantly beyond the main orifice 40 into the inner chamber 30.

[0044] During normal operation (as shown in Figures 3(a) and 3(b)), when the weight of the aircraft 1 is applied to the wheel 14, for example during landing, the gas in the storage compartment 34 is compressed, thereby forcing the oil in the storage compartment 34 into the inner chamber 30 through the main orifice 40. The oil then flows from the inner chamber 30 to the outer chamber 33 via the orifice 28. When fully pressurized, the oil from the outer chamber 33 flows into the springback chamber 32 through the damping orifice in the piston bearing 20. The upward movement of the piston 10 and the slider 22 causes the metering rod 24 to move relative to the main orifice 40. The metering rod 24 is thicker at its base than at its tip, thus reducing the cross-sectional area of ​​the main orifice 40 through which fluid can flow as the metering rod 24 moves upward. This increases the flow resistance of the fluid through the main orifice 40 and dampens the upward movement of the piston 10. When the weight is released from wheel 14, for example after takeoff, piston 10 descends under the weight of wheel 14, and the oil present in the rebound chamber 32 slows the descent of piston bearing 20, thereby damping the extension of piston 10. Piston 10 continues to move downward within cylinder 8 until piston bearing 20 abuts against stop surface 44. Stop surface 44 thereby limits the extension of landing gear 4.

[0045] If the landing gear 4 is severely compressed for only a short time before being released (e.g., after a touchdown and go-around event), very little or no oil will flow into the rebound chamber 32 when the load is released from wheel 14. Therefore, the extension of the landing gear—that is, the downward movement of piston 10—will be undamped or insufficiently damped, and piston 10 will travel faster when piston bearing 20 reaches stop surface 44, thereby generating a larger extension load on stop surface 44 that may exceed the design maximum. Length L1 is the distance between the lower end of piston bearing 20 and the lower end of cylinder block 8 in Figure 3(b).

[0046] Figures 4(a) and 4(b) show schematic height views of a portion of the landing gear in extended configuration of Figures 3(a) before an event that has caused the extended load to exceed the design maximum, such as a 'touch-and-go' event, and Figure 3(b) after said event. In Figure 4(b), a region 48 of the outer stop tube 46 is wrinkled (region 48 may therefore be referred to as a wrinkled element or wrinkled area), and this region 48 is deformed compared to the rest of the outer stop tube 46 and the appearance of said region 48 in Figure 4(a). In Figures 4(a) and 4(b), region 48 is located at the lower end of the outer stop tube 46, but the axial and / or circumferential position of region 48 is not particularly important. Length L2 is the distance between the lower end of the piston bearing 20 and the lower end of the cylinder block 8. As a result of the compaction zone 48, the length L2 is less than the length L1 because the outer stop tube 46 is now shorter, thus allowing the piston bearing 20 to move further along the cylinder block 8, and the landing gear 4 is longer in Figure 4(b) than in Figure 4(a).

[0047] In some embodiments, the outer stop tube 46 is made of aluminum, but it will be understood that other materials may be used. In the same or other embodiments, region 48 is made of the same material as the rest of the outer stop tube 46, but region 48 has a different geometry, such as a reduced thickness compared to other regions of the outer stop tube. In other embodiments, region 48 is made of a different material than the rest of the outer stop tube 46. In other embodiments, region 48 has a structure different from the rest of the outer stop tube 46, such as including one or more folds, recesses, and / or through holes, which reduce the level of extended load required to deform the element. In the same or other embodiments, the folded element may be configured as a separate component on the load path between the stop surface 44 and the cylinder bearing 42. In some embodiments, the length of the landing gear may be increased by 2 mm to 3 mm after the folded element deforms. Embodiments of the invention include elements (folded elements) designed to deform when subjected to a predetermined load. Such an element can form a planned region with a weakness along the load path, through which the extended load associated with stopping the downward movement of the piston is responded to by the cylinder. Those skilled in the art will understand that many different ways exist to provide such a corrugated element, including but not limited to incorporating different materials, geometries, and / or structures in the design of such an element.

[0048] By including the folding element as described above, the landing gear according to this exemplary embodiment can allow the detection and / or confirmation of an event (hereinafter referred to as an extension event) in which the extension load generated during the extension of the landing gear exceeds a predetermined level, such as a design maximum value. In particular, including the folding element as described above allows for the detection and / or confirmation of such an event without requiring disassembly of the landing gear. Additionally or alternatively, the folding element as described above can be incorporated into existing components of the landing gear, such as the outer stop sleeve, thereby allowing for the detection and / or confirmation of the extension event without requiring any additional components of the landing gear. Additionally or alternatively, including the folding element as described above allows for the detection and / or confirmation of such an extension event in a mechanically simple and reliable manner.

[0049] Figure 5 A flowchart of an example method according to the present invention is shown. Figure 5 The method includes measuring the length 70 of the landing gear when it is in maximum extension. In some embodiments, the total length of the landing gear (e.g., the distance between the proximal and distal ends of the landing gear) is measured. In other embodiments, the distance between a first reference point on the landing gear (e.g., on the cylinder or major assembly of the landing gear) and a second reference point (e.g., on the piston) is measured. The method includes determining, based on the measured length, whether an extension event 72 has occurred. If the length of the landing gear in maximum extension has increased, for example, by more than a predetermined threshold amount, this is considered an indication that the landing gear has undergone an extension event. Conversely, if the length of the landing gear has not increased or has increased by less than the predetermined threshold amount, this is considered an indication that the landing gear has not yet undergone an extension event. If it is determined that an extension event 72 has occurred, landing gear maintenance 72 can be appropriately performed. Optionally, the method includes jacking up the aircraft 76 before measuring the length 70 to reduce the weight of the wheels and the landing gear to be extended. In other example methods, the step of measuring the length 70 can be performed while the aircraft is in flight. In this method, one or more sensors can be used to detect changes in the length of the landing gear. For example, by verifying whether a target (e.g., on the piston) remains close to a proximity sensor (e.g., on the cylinder block).

[0050] In other methods according to the invention, detection and / or confirmation of an extension event can be achieved by determining whether the crease element has creased, for example, using non-destructive testing techniques including X-rays and / or ultrasound. This technique allows for confirmation and / or detection of extension events without requiring the aircraft to be lifted. In the same or other embodiments, an extension event can be achieved by determining whether the conductivity, i.e., resistance, of the outer stop sleeve (or any other element containing the crease element) has changed.

[0051] Although the invention has been described and illustrated with reference to specific embodiments, it will be understood by those skilled in the art that the invention is applicable to many different variations not specifically described herein. It will be understood by way of example only that the application of the invention is not limited to landing gears having the specific geometries and arrangements shown above and in the accompanying drawings. For example, the shape and / or structure of the cylinder block, piston, slider, spring chamber, compression chamber, outer stop tube, piston bearing, and / or cylinder block bearing may differ from those described herein. In some embodiments, one or more of the slider, spring chamber, compression chamber, outer stop tube, piston bearing, and / or cylinder block bearing may be completely absent. The layout of the main orifice and other orifices may differ from the layout of the main orifices and other orifices described above, and in some embodiments, one or more or all of the orifices may be absent. For example, the invention can be applied to landing gears that do not rely on oil and / or gas for damping.

[0052] In the foregoing description, where references are made to elements or components having known, obvious, or foreseeable equivalents, these equivalents are incorporated herein as if described separately. The true scope of the invention should be determined with reference to the claims, and should be interpreted as encompassing any of these equivalents. The reader will also understand that elements or features of the invention described as preferred, advantageous, convenient, etc., are optional and do not limit the scope of the independent claims. Furthermore, it should be understood that while such optional elements or features may be beneficial in some embodiments of the invention, they may be undesirable and therefore absent in other embodiments.

Claims

1. An aircraft landing gear shock absorber, the aircraft landing gear shock absorber comprising: Cylinder block; A piston assembly including a piston, the piston assembly being mounted to move relative to the cylinder body; A stop surface, the stop surface being arranged to limit the extension of the aircraft landing gear shock absorber, wherein the stop surface is mounted on the cylinder, a load path extends between the stop surface and the cylinder, and an extended load on the stop surface is at least partially transferred to the cylinder via the load path; and A pleated element located on the load path and configured to plastically deform when the extended load on the stop surface exceeds a predetermined threshold. Wherein, the wrinkled element is a separate component, and the properties of the wrinkled element differ from those of other components on the load path between the stop surface and the wrinkled element and / or between the stop surface and the cylinder block, such that the wrinkled element plastically deforms under lower elongation loads compared to the other components; or The wrinkled element is a region of the component, and the properties of the wrinkled element are different from those of the rest of the component, such that the wrinkled element plastically deforms under lower elongation loads compared to the rest of the component.

2. The aircraft landing gear shock absorber according to claim 1, wherein, The aircraft landing gear damper is configured such that the plastic deformation experienced by the pleated element under an extended load exceeding the predetermined threshold results in an increase in the length of the aircraft landing gear damper at its maximum extension.

3. The aircraft landing gear shock absorber according to claim 2, wherein, The cylinder has a first end, and the pleated element is located between the first end and the stop surface, such that the plastic deformation of the pleated element reduces the distance between the first end and the stop surface, thereby causing an increase in the length of the aircraft landing gear shock absorber at its maximum extension.

4. The aircraft landing gear shock absorber according to any one of claims 1-3, wherein, The aircraft landing gear shock absorber includes an outer stop sleeve installed in the cylinder body, and the outer stop sleeve includes the stop surface.

5. The aircraft landing gear shock absorber according to claim 4, wherein, The outer stop sleeve includes the pleated element.

6. The aircraft landing gear shock absorber according to any one of claims 1-3, wherein, The aircraft landing gear shock absorber is a hydraulic strut.

7. The aircraft landing gear shock absorber according to any one of claims 1-3, wherein, The crease element is located within the aircraft landing gear shock absorber, making it invisible during normal use.

8. An aircraft landing gear comprising an aircraft landing gear shock absorber according to any one of claims 1-7.

9. An aircraft comprising the aircraft landing gear according to claim 8.

10. A method for determining whether an aircraft landing gear has experienced an extension event, wherein, The aircraft landing gear includes an aircraft landing gear damper according to any one of claims 1-7, and the extension event includes an extension load exceeding a predetermined threshold generated when the aircraft landing gear damper reaches maximum extension, the method including determining whether the crease element has undergone plastic deformation, and determining whether the extension event has occurred based on whether the crease element has undergone plastic deformation.

11. The method for determining whether an aircraft landing gear has experienced an extension event according to claim 10, wherein, Determining whether the folded element has undergone plastic deformation includes measuring the aircraft landing gear to determine whether the length of the aircraft landing gear at its maximum extension has increased.

12. The method for determining whether an aircraft landing gear has experienced an extension event according to claim 10 or claim 11, wherein, Determining whether the wrinkled element has undergone plastic deformation includes using non-destructive testing techniques and / or imaging techniques to determine whether the shape of the wrinkled element has changed.

13. The method for determining whether an aircraft landing gear has experienced an extension event according to claim 12, wherein, The nondestructive testing and / or imaging technologies include ultrasound or X-rays.

14. The method for determining whether an aircraft landing gear has experienced an extension event according to claim 10 or claim 11, wherein, Determining whether the wrinkled element has undergone plastic deformation includes measuring the electrical conductivity of the wrinkled element.

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