Fixed landing gear structure with flexibility based on longitudinal wheel displacement

Abstract

The present invention discloses a fixed and flexible landing gear structure that comprises a specific geometry that allows flexibility based on the displacement of the tire and wheel assembly in the longitudinal direction, which can be forward or backward depending on the vertical displacement downwards of the fuselage of the aircraft. The proposed flexible fixed landing gear structure may be applicable to the main part and the front part (nose landing gear) of the aircraft.

Description

[0001] FIXED LANDING GEAR STRUCTURE WITH FLEXIBILITY BASED ON LONGITUDINAL WHEEL DISPLACEMENT FIELD OF THE INVENTION

[0002]

[0001] This invention falls within the field of mechanical and aeronautical engineering. More specifically, this invention is related to the area of structural engineering and comprises the application of flexible structures for absorbing kinetic energy.

[0003] BACKGROUND OF THE INVENTION

[0004]

[0002] Typically, fixed landing gears used on light aircraft absorb kinetic energy related to the movement of the aircraft, at the time of landing, and this absorption of kinetic energy is achieved by flexing the aircraft ' s landing gear structure . More specifically, the flexion of the landing gear structure occurs with the lateral displacement of the wheels as shown in figure 1. This lateral displacement of the wheels begins when the landing gear wheels touch the ground and continues as the aircraft rolls on the runway, thereby minimizing tire wear and the appearance of lateral friction loads .

[0005]

[0003] In vertical landing aircraft, the use of a fixed landing gear concept leads to excessive tire wear and the occurrence of lateral wheel loads, since the aircraft does not roll on the runway.

[0006]

[0004] Even in fixed landing gear with shock absorbers, such as used in some helicopters, complex mechanisms are necessary to make possible the necessary absorption of the kinetic energy and avoid the appearance of lateral loads and tire wear . The use of these additional mechanisms tends toincrease the weight of the landing gear assembly, influencing in the aircraft ' s performance .

[0007] STATE OF THE ART

[0008]

[0005] Technologies related to improvements made to landing gear assemblies can be found in the state of the art published in patent literature .

[0009]

[0006] Document WO 90 / 06257 discloses a wheeled landing gear assembly designed for fast replacement of a skid landing gear assembly comprising a pair of fore and aft longitudinal tubes attached to a pair of short, spaced-apart cross tubes that are positioned to be mounted on a helicopter structural saddle used to mount the skid landing gear . The longitudinal tubes act as energy absorbers for vertical loads during landing and, also act to stabilize the landing gear in the presence of wheel drag loads during flight . The document also discloses that during landing, the nose gear loads are absorbed by the bending deflection of the fore and aft longitudinal tubes and a resilient spring in the nose gear may be used to absorb energy in conjunction with the deflection of the longitudinal tubes .

[0010]

[0007] Although document WO 90 / 06257 discloses the use of flexible structural interfaces connecting the wheels to the aircraft, the document discloses an assembly with heavy weight, and which also relies on the lateral movement of rear wheels the landing gear wheels to absorb kinetic energy.

[0011]

[0008] Document US7770843 B2 discloses a new connection between the skid transverse beams and the fuselage of an aircraft that has variable angular stiffness and which increases with the sinking speed after contact with the ground, being intended to avoid ground resonance .

[0009] This document reveals that the connection means comprise first a connection means which alone, transmits forces from the cross-member to the airframe so long as the deformation of the cross-member remains below a determined level of deformation. It also discloses a second connection means that transmits forces from the cross-member to the airframe only when the level of cross-member deformation reaches or exceeds said predetermined level of deformation either in rolling or in vertical sinking.

[0012]

[0010] However, document US7770843 B2 also discloses an assembly with heavy weight, and which also relies on the lateral movement of the landing gear wheels to absorb kinetic energy, resulting in tire wear and lateral loads .

[0013] [ Oil ] Document US20230150655 Al discloses leaf spring type landing gear including a frame having a shape with higher performance for mitigation and absorption of shocks . The leaf spring type landing gear is mounted on a lower portion of a fuselage of an aircraft and includes a first frame connected to the fuselage and bent to have a circle center below; a second frame connected to the first frame; and a third frame connected to the second frame and at least partially bent to have a circle center below, wherein the second frame includes a 2-lst frame and a 2-2nd frame having circle centers formed in opposite directions and is formed to be bent in an S shape .

[0014]

[0012] This document reveals a landing gear with an elastic body (leaf spring type) in an S shape with a shock absorber at the bottom, and aims to minimize load factors, improve energy absorption and prevent the aircraft from bouncing during a hard landing.

[0013] However, the invention disclosed in document US20230150655 Al still reveals an assembly with heavy weight, and which also relies on the lateral movement of the landing gear wheels to absorb kinetic energy, resulting in tire wear and lateral loads .

[0015]

[0014] In a contrary manner and in order to solve the existing problems of the state of the art, mainly related to the lateral movement of the landing gear wheels that results in tire wear and lateral loads, the present invention adopts a different concept when compared to typical solutions and proposes the use of a fixed and flexible landing gear assembly for vertical landing aircrafts as an alternative to a conventional landing gear with shock absorbers .

[0016] BRIEF DESCRIPTION OF THE INVENTION

[0017]

[0015] The present invention discloses a fixed and flexible landing gear structure that comprises a specific geometry that allows flexibility based on the displacement of the tire and wheel assembly in the longitudinal direction, which can be forward or backward depending on the vertical displacement downwards of the fuselage of the aircraft . The propose fixed and flexible landing gear structure may be applicable to the main and the front (nose) landing gears of the aircraft .

[0018] BRIEF DESCRIPTION OF THE DRAWINGS

[0019]

[0016] To assist in identifying the main characteristics of the present invention, each figure is briefly described as follows :

[0020]

[0017] Figure 1 shows the landing gear of aircraft bending as known from the stated of the art, with the lateral wheel displacement .

[0018] Figure 2A, 2B and 2C show the proposed fixed and flexible landing gear .

[0021]

[0019] Figure 3 shows fixed landing gear flexibility relationship between vertical fuselage displacement and longitudinal wheel displacement .

[0022]

[0020] Figure 4 shows the flexibility of the parts of fixed landing gear according to a first embodiment of the invention .

[0023]

[0021] Figure 5A, 5B and 5C show variation in size of the fixed and flexible landing gear .

[0024]

[0022] Figure 6 shows the flexibility of the parts of a fixed landing gear according to a second embodiment of the invention related to nose landing gear .

[0025]

[0023] Figure 7 shows the fixed and flexible landing gear structure being applicable to the main part and the front part (nose) of the aircraft and main landing gear .

[0026] DETAILED DESCRIPTION OF THE INVENTION

[0027]

[0024] The present invention proposes the concept of a fixed and flexible landing gear whose flexibility is defined by the displacement of the tire and the wheel assembly in the longitudinal direction, and which can be forward or backward. One of the embodiments of the proposed fixed and flexible landing gear can be seen in figures 2A, 2B and 20 which shows the fixed and flexible landing gear in lateral, front and perspective views respectively.

[0028]

[0025] To make this concept viable, the fixed landing gear structure has a geometry that maximizes the longitudinal displacement (dx) of the tire and wheel assembly, in relation to the vertical displacement (dz ) of the fuselage of theaircraft . As shown in figure 3, the initial longitudinal distance between the wheel axis and one of the landing gear connection points with the aircraft' s fuselage, is defined as (Lx) . The longitudinal displacement (dx) of the tire and wheel assembly (Lx + dx) can be observed as the result of the vertical displacement (dz) of the aircraft' s fuselage .

[0029]

[0026] Therefore, the wheel displacement in the longitudinal direction during landing aims to avoid excessive tire wear and the occurrence of lateral loads on the wheel . That is why it is not convenient to use fixed and no flexible landing gear on vertical landing aircraft, since the wheel (s) would typically move laterally, resulting in tire wear and lateral loads .

[0030]

[0027] Thus, the longitudinal displacement of the wheel assembly that guarantees flexibility and aims to absorb the kinetic energy originated from the vertical landing displacement of the aircraft through the relationship between the vertical displacement of the fuselage (dz) and the displacement in the longitudinal direction of the wheel assembly (dx) .

[0031]

[0028] The displacement of the proposed fixed and flexible main landing gear as the result of the vertical displacement of the fuselage (dz) occurs through the flexion in opposite directions of the front beam ( 1 ) and the rear beam (2 ) of the landing gear' s structure and which may connect the wheel assembly to two interface points (A) and (B) with the fuselage positioned in a horizontal line (H) as shown in figure 4.

[0032]

[0029] In an alternative embodiment, the front beam ( 1 ) and the rear beam (2 ) of the landing gear' s structure mayconnect the wheel assembly to a single interface point with the fuselage .

[0033]

[0030] In addition, the landing gear structure may also comprise one or more transverse beams (3) connecting the front beam ( 1 ) in one end and the rear beam (2 ) in the other end as also shown in figure 4.

[0034]

[0031] Therefore, during landing, the vertical displacement of the fuselage (dz) occurs pressing the landing gear structure against the ground. The front beam ( 1 ) of the landing gear' s structure flexes downwards (down bending) while the rear beam (2 ) flexes upwards (up bending) so that the landing gear wheel moves backwards (dx) .

[0035]

[0032] This geometry and flexibility pattern for the main fixed landing gear with at least one interface point with the fuselage is repeated for different landing gear sizes as shown in figures 5A, 5B and 5C, noting that as the main landing gear becomes larger, new transverse beams may be applied. This allows the concept to be applied to both small aircraft and helicopters, drones and VTOLs .

[0036]

[0033] The beams of the landing gear structure may be preferably circular or rectangular but not limited to these sections and may have a cross-section body as tubular or solid. In addition, the beams can be made in metallic or composite material .

[0037]

[0034] The proposed concept can also be applied to the front part of the aircraft (nose landing gear) , and in this example, an upper beam (4 ) and a lower beam (5) connect the wheels assembly to two points of the fuselage (A' ) and (B' ) of the aircraft, positioned in a vertical line (V) as shown in figure 6. For the geometry of front landing gear, therelationship between the vertical displacement of the fuselage (dz) and the displacement in the longitudinal direction of the wheel (dx) occurs through the bending (Up Bending) of both, the upper beam (4 ) and the lower beams (5) , in the same direction, which in this case is upwards .

[0038]

[0035] Therefore, the focus of protection is a fixed and flexible landing gear structure comprising a specific geometry that allows flexibility based on the displacement of the tire and wheel assembly in the longitudinal direction, which can be forward or backward depending on the vertical displacement downwards of the fuselage . The proposed fixed and flexible landing gear structure being applicable to the main part and the front part (nose) of the aircraft as shown in figure 7 .

Claims

CLAIMS1. Fixed landing gear structure with flexibility based on longitudinal wheel displacement CHARACTERIZED IN THAT comprises :a flexible front beam ( 1 ) connecting the wheel assembly to the aircraft' s fuselage;a flexible rear beam (2 ) connecting the wheel assembly to the aircraft' s fuselage;wherein the flexible front beam ( 1 ) is down bendable while the flexible rear beam (2 ) is up bendable .

2. Fixed landing gear of claim 1, CHARACTERIZED IN THAT the front beam ( 1 ) and the rear beam (2 ) of the landing gear structure may connect the wheel assembly to a single interface point with the aircraft' s fuselage .

3. Fixed landing gear of claim 1, CHARACTERIZED IN THAT the front beam ( 1 ) and the rear beam (2 ) of the landing gear structure may connect the wheel assembly to two interface points (A) and (B) with the aircraft' s fuselage .

4. Fixed landing gear of claim 1, CHARACTERIZED IN THAT the landing gear structure may also comprise one or more transverse beam ( 3) connecting the front beam ( 1 ) at one end and the rear beam (2 ) at the other end.

5. Fixed landing gear of claim 1, CHARACTERIZED IN THAT the beams of the landing gear structure may be circular or rectangular .

6. Fixed landing gear of claim 5, CHARACTERIZED IN THAT the beams may have a cross-section body as tubular or solid.

7. Fixed landing gear of claim 6, CHARACTERIZED IN THAT the beams can be made in metallic or composite material .

8. Fixed landing gear structure with flexibility based on longitudinal wheel displacement CHARACTERIZED IN THAT comprises :a flexible upper beam (4 ) connecting the wheel assembly to the aircraft' s fuselage; anda flexible lower beam (5) connecting the wheel assembly to the aircraft' s fuselage;wherein the flexible upper beam (4 ) and the flexible lower beam (5) are both, up bendable .

9. Fixed landing gear of claim 8, CHARACTERIZED IN THAT the upper beam (4 ) and the lower beam (5) of the landing gear structure may connect the wheel assembly to a single interface point with the aircraft' s fuselage .

10. Fixed landing gear of claim 8, CHARACTERIZED IN THAT the upper beam (4 ) and the lower beam (5) of the landing gear structure may connect the wheel assembly to two interface points (A' ) and (B' ) with the aircraft' s fuselage .

11. Fixed landing gear of claim 8, CHARACTERIZED IN THAT the landing gear structure may also comprise one or more transverse beam (3) connecting the upper beam (4 ) at one end and the lower beam (5) at the other end.

12. Fixed landing gear of claim 8, CHARACTERIZED IN THAT the beams of the landing gear structure may be circular or rectangular .

13. Fixed landing gear of claim 12, CHARACTERIZED IN THAT the beams may have a cross-section body as tubular or solid .

14. Fixed landing gear of claim 13, CHARACTERIZED IN THAT the beams can be made in metallic or composite material .

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