Rotorcraft

Abstract

This invention relates to a rotorcraft having a rotor and a skid-type landing gear, the landing gear having a first skid and a second skid, as well as a first lateral member and a second lateral member. The first lateral member is connected to the rotorcraft fuselage only by two fasteners. The second lateral member is carried only during flight by two supports fastened to the fuselage and through which the second lateral member passes. Each support includes a hole defined by a stop surface, and the second lateral member is always separated from each stop surface by a gap. An intermediate support member is arranged laterally between the two supports and above the second lateral member.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of FR2303075, filed on March 30, 2023, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] This invention relates to a rotorcraft whose fuselage is supported by a skid-type landing gear with areas capable of withstanding variable forces. More specifically, this invention belongs to the technical field of skid-type landing gear for rotorcraft. Background Technology

[0004] Traditionally, gyroplanes include landing gear through which the fuselage rests on the ground. More specifically, landing gear, known as "skid landing gear," has a first longitudinal support skid and a second longitudinal support skid. The skids are designed to make contact with the ground.

[0005] To connect each skid to the rotorcraft fuselage, the skid landing gear may have a first lateral member and a second lateral member, each of which connects the first skid to the second skid.

[0006] In addition, rotorcraft, including those with lift rotors having at least three articulated blades, may be affected by ground resonance.

[0007] In fact, based on the elastic deformation patterns of the landing gear, particularly the elastic deformation related to roll, the oscillations of each blade around its drag axis can combine in an unstable manner with the motion of the rotorcraft's fuselage. This is what causes "ground resonance."

[0008] As the rotor blades rotate, they move out of their stable position within the rotor's plane of rotation and may become unequally distributed around the rotor's axis of rotation. This uneven distribution leads to imbalance as the rotor's center of gravity moves away from its axis of rotation. Furthermore, as the blades move out of their stable position, they oscillate around that position at an oscillation frequency FPP, which is the blade's inherent drag frequency. The rotorcraft fuselage is then excited at an excitation frequency equal to the rotor's rotational frequency plus or minus the absolute value of the oscillation frequency FPP.

[0009] When the natural roll or pitch frequency of the fuselage on the landing gear is close to the excitation frequency corresponding to a phenomenon known as ground resonance, there is a risk of instability on the ground. In fact, roll instability may occur if the natural roll frequency of the fuselage on its landing gear is close to the absolute value of the rotor's rotational frequency minus the oscillation frequency FPP.

[0010] To avoid instability, attempts have been made to prevent these frequency interactions by adjusting the roll and / or pitch stiffness of the landing gear. However, adjusting the landing gear can be complex. In particular, a compromise needs to be found between the vertical stiffness of the landing gear, which manages comfort during landing and the load levels introduced into the fuselage, and the pitch and roll stiffness, which have a significant impact on ground resonance behavior.

[0011] It should be noted that "vertical stiffness" is used by those skilled in the art to refer to the stiffness of the landing gear along the vertical axis of the rotorcraft to its most recent static attitude under the action of gravity (or any other vertical load).

[0012] In addition, the landing gear is connected to the fuselage by fasteners that connect the front and rear transverse members to the fuselage of the rotorcraft.

[0013] Traditional skid-mounted landing gear consists of two fasteners on one transverse member and a central fastener on another transverse member. This type of landing gear can be described as a "landing gear with three fastening points." The advantage of a landing gear with three fastening points is that it reduces the inherent roll frequency of the fuselage resting on the landing gear, which may limit the risk of ground resonance. However, the fuselage needs to be reinforced to withstand the forces introduced at a single point by the transverse members fastened to the fuselage via a single fastener during a hard landing.

[0014] Another conventional skid-type landing gear includes two fasteners on each transverse member and can be described as a "landing gear with four fastening points." This type of landing gear is advantageous because it allows the forces maintained during a hard landing to be distributed across the two wing spars of the fuselage. However, the inherent roll frequency of the fuselage resting on the landing gear is also increased.

[0015] Therefore, designing skid landing gear is a challenging task.

[0016] In particular, various landing gears are known for preventing ground resonance.

[0017] Document FR2749561A1 describes a skid landing gear with three fastening points.

[0018] Document FR2554210A1 describes a flexible beam made of composite materials, which is essentially in the form of an elongated box with a laminated structure. Two rigid flanges are connected by two webs. Between the two flanges are deformable energy-absorbing inserts comprising at least one block made of an elastomeric material with high deformation remanence. The beam also includes at least one viscoelastic damper mounted on the outer surface of the flanges. When the beam bends, the damper is tensioned via a linkage, thereby increasing the damping provided by each energy-absorbing insert.

[0019] Document US4270711 discloses a landing gear having a beam that is pivotally connected to a transverse member of the landing gear so as to be able to rotate about an axis.

[0020] Document US6244538 discloses a transverse member that engages with two pivot fasteners.

[0021] Document US3173632 discloses a landing gear having two skids connected by two torsion bars.

[0022] Document FR2895368B1 discloses a rotorcraft having a front transverse member and a rear transverse member, the front transverse member having four front links to be connected to the fuselage, and the rear transverse member having a single central fastener. The four front links include two first active linkages for transmitting forces between the front transverse member and the fuselage when the front transverse member undergoes deformation less than a predetermined roll or vertical drop deformation, and two second active linkages for transmitting forces when the transverse member undergoes deformation reaching or exceeding a predetermined deformation.

[0023] Document FR2965546A1 describes an aircraft that includes landing gear adapted to ground slope.

[0024] Also known are documents FR2995874A1, FR3014079B1, and FR3029891B1. Document CN106347638A is also known, describing a skid-type landing gear for unmanned aerial vehicles. Summary of the Invention

[0025] Therefore, the object of this invention is to provide a rotorcraft with an innovative landing gear for limiting the risk of ground resonance and for structurally optimizing the fuselage.

[0026] Therefore, the present invention relates to a rotorcraft having a rotor and a skid-type landing gear having a first skid and a second skid, as well as a first lateral member and a second lateral member, the first lateral member and the second lateral member each connecting the first skid to the second skid, the first lateral member and the second lateral member each having a first branch fixed to the first skid and a second branch fixed to the second skid, and a central branch connecting the first branch to the second branch, the first lateral member being connected to the fuselage of the rotorcraft by only two fasteners.

[0027] These two fasteners can be connected to the two corresponding wing spars of the fuselage.

[0028] The second lateral member is supported only during flight by two supports fastened to the fuselage through which the second lateral member passes. Each support includes a hole defined by a stop surface of the support. The second lateral member is always separated from each stop surface by a gap. The fuselage supports an intermediate support member arranged laterally between the two supports. When the rotorcraft is parked on a level ground, the intermediate support member is above the second lateral member. When the rotorcraft is parked on the ground and in the absence of plastic deformation and vertical acceleration of the second lateral member, the second lateral member presses against the intermediate support member, and the gap exists above the second lateral member.

[0029] The statement "when the rotorcraft is parked on the ground and in the absence of plastic deformation and vertical acceleration of the second transverse member, the gap above the second transverse member" means that when the rotorcraft is parked on the ground and in the absence of overturning and deformation, as an observer would see, the space between the second transverse member and each stop surface is located above the second transverse member.

[0030] Therefore, when on the ground and under normal landing conditions, the landing gear behaves like a landing gear with three fastening points during the first operational phase. Forces are transmitted between the landing gear and the fuselage via two fasteners for the first lateral member and an intermediate support member for the second lateral member. In fact, the dimensions of the support member are determined to have a gap above the second lateral member under these conditions to prevent force transmission. Thus, the inherent roll frequency of the fuselage on the landing gear is minimized, which, from the perspective of ground resonance, can help improve the rotorcraft's behavior.

[0031] Furthermore, using an intermediate support member that only contacts the top of the second lateral member during flight and does not clamp the second lateral member, instead of clamping the flange of the lateral member, helps to create a connection between the second lateral member and the fuselage that completely decouples the roll vibration mode of the fuselage from other vibration modes.

[0032] Furthermore, under normal landing conditions, the force transmission via the intermediate support member remains moderate. Therefore, the intermediate support member can be secured to a structure that does not require significant reinforcement.

[0033] During a hard landing, the second operational phase of the second lateral member is initiated. The second lateral member bends and folds beneath the intermediate support member, causing it to contact the top of the stop surface of the support member. Force is transmitted between the landing gear and the fuselage via two fasteners for the first lateral member and two supports for the second lateral member. The supports are now sized to have clearance beneath the lateral members. The landing gear then behaves as if it were a landing gear with four fastening points.

[0034] Therefore, the considerable forces generated by a hard landing at the second transverse member are transferred to two different areas of the fuselage, thus optimizing its dimensions. Furthermore, the second transverse member can plastically deform, allowing some of the fuselage's kinetic energy to be absorbed during landing.

[0035] Therefore, rotorcraft have landing gear that has the advantages of skid landing gear with three fastening points under normal conditions and skid landing gear with four fastening points under less favorable conditions.

[0036] Rotorcraft may also include one or more of the following features, either individually or in combination.

[0037] According to one possibility, the second transverse member has a lower part and an upper part in the vertical direction. When the rotorcraft is parked on the ground and in the absence of plastic deformation and vertical acceleration of the second transverse member, the lower part rests on the bottom of the stop surface of each support member, while the gap separates the upper part from the top of the stop surface of each support member, and the upper part presses against the intermediate support member.

[0038] The statement that "the second horizontal component has a lower and an upper part in the vertical direction" means that when the rotorcraft is parked on the ground, unless it flips over, the observer will see the upper part as higher than the lower part.

[0039] Therefore, the force is transmitted only through the intermediate support member between the second horizontal member and the fuselage.

[0040] Conversely, when the deformation exceeds the threshold deformation, for example, when the second horizontal member undergoes plastic deformation, the lower part no longer rests on the bottom of the stop surface of the support member, but the upper part presses against the top of the stop surface of each support member. Furthermore, the upper part no longer presses against the intermediate support member.

[0041] According to a possibility compatible with the aforementioned possibilities, when on the ground, as long as the deformation experienced by the second horizontal member is below the limit deformation, the second horizontal member can introduce force into the fuselage only through the intermediate support member; when the deformation experienced by the second horizontal member is greater than the limit deformation, the second horizontal member introduces force into the fuselage only through the two support members.

[0042] The ultimate deformation may be the beginning of plastic deformation of the second lateral member. When the second lateral member undergoes plastic deformation, the landing gear behaves like a landing gear with four fastening points, and when the second lateral member undergoes elastic deformation, the landing gear behaves like a landing gear with three fastening points.

[0043] According to one possibility compatible with the foregoing, each support may include a reinforcement that carries a liner, the liner including a stop surface of the support.

[0044] For example, the lining prevents metal-to-metal contact between the support and the cross member. For example, this lining may not be made of metal, but rather of an elastomer.

[0045] The reinforcement may include a U-shaped half-clamp fixed to the fuselage. This half-clamp is relatively simple and allows the second cross member to be closed while providing the required clearance.

[0046] According to one possibility compatible with the foregoing possibilities, the intermediate support member may include a base fixed to the fuselage that carries the insert, which rests against the insert when the rotorcraft is parked on the ground and in the absence of plastic deformation and vertical acceleration of the second transverse member.

[0047] For example, the insert is designed to prevent metal-to-metal contact between the support and the cross member. For example, such an insert may not be made of metal, but rather of an elastomer.

[0048] The insert may include a plane that contacts the second cross member. Alternatively, the insert may include a surface that contacts the second cross member, which is shaped to conform to the shape of the second cross member, for example, extending along an arc.

[0049] According to one possibility compatible with the foregoing, the two holes of the two supports can have rectangular shapes in two corresponding longitudinal vertical planes, and the second horizontal member has a circular cross section in the longitudinal vertical planes without deformation.

[0050] For example, each longitudinal vertical plane is parallel to the rotorcraft's yaw and roll axes.

[0051] The rectangular shape of the hole gives the second horizontal member with a circular cross-section a degree of freedom of movement in the vertical direction.

[0052] According to one possibility compatible with the aforementioned possibilities, the two support members can be correspondingly fastened to the two wing spars of the fuselage, the two fasteners can be correspondingly fastened to the two wing spars, and the intermediate support member can be fastened to the structure extending from one wing spar to the other.

[0053] Therefore, the rotorcraft frame may include two spars supporting two supports and two fasteners to withstand forces during a hard landing. Each spars may include one or more beams. Another beam or frame may support an intermediate support member.

[0054] According to one possibility compatible with the foregoing possibilities, the two supports include a first support and a second support, and the central branch of the second transverse member can carry a first stop and a second stop, the first stop and the second stop being configured to restrict the degree of freedom of movement of the second transverse member relative to the fuselage in the direction from the first support to the second support by correspondingly interfering with the shapes of the first support and the second support.

[0055] Since the two supports and the intermediate support member do not clamp the second transverse member, the two stop members restrict the second transverse member's degree of freedom of movement in the lateral direction. For example, each stop member may include a skid fastened to the central branch of the second transverse member by a screw / nut system. Each stop member may be positioned between the two supports.

[0056] According to a possibility compatible with the foregoing, when the first stop member contacts the first support member, the second stop member does not contact the second support member, and when the second stop member contacts the second support member, the first stop member does not contact the first support member.

[0057] This structure avoids the need for a stop component to always be in contact with any support.

[0058] According to one possibility compatible with the foregoing, the intermediate support member may extend at a distance equal to that of the two supports. Attached Figure Description

[0059] The invention and its advantages will appear in more detail below in the context of the description of embodiments given with reference to the accompanying drawings, in which:

[0060] Figure 1 This is a simplified perspective view of a rotorcraft according to the present invention;

[0061] Figure 2 This is a perspective view of the second transverse member of the landing gear according to the present invention;

[0062] Figure 3 This is a longitudinal view of the second transverse member of the landing gear according to the present invention;

[0063] Figure 4 A longitudinal view of the second transverse member of the landing gear according to the present invention during flight;

[0064] Figure 5 This is a longitudinal view of the second transverse member of the landing gear according to the invention, operating according to the first operating phase in a rotorcraft with minimal mass.

[0065] Figure 6 This is a longitudinal view of the second transverse member of the landing gear according to the invention, operating according to the first operating phase in a rotorcraft with maximum mass.

[0066] Figure 7 This is a longitudinal view of the second transverse member of the landing gear according to the invention during the transition between the first and second operating phases; and

[0067] Figure 8 This is a longitudinal view of the second transverse member of the landing gear according to the invention, operating according to the second operating phase. Detailed Implementation

[0068] Elements present in multiple figures have the same reference numerals in each figure.

[0069] The diagram shows three directions, X, Y, and Z, that are orthogonal to each other.

[0070] The first direction X is referred to as the longitudinal direction, and it is parallel to the roll axis of the rotorcraft shown. The term "longitudinal" relates to any direction parallel to the first direction X.

[0071] The second direction Y is referred to as the lateral direction and is parallel to the pitch axis of the rotorcraft shown. The term "lateral" relates to any direction parallel to the second direction Y.

[0072] Finally, the third direction Z is referred to as the vertical direction, which is parallel to the yaw axis of the rotorcraft shown. The term "vertical" is used in relation to any direction parallel to the third direction Z.

[0073] Figure 1 A rotorcraft 1 is shown. The rotorcraft 1 includes a rotor 3 carried by a fuselage 2. The rotor 3 may include at least three blades 4, each blade 4 being movable relative to the hub, particularly in the drag direction.

[0074] The fuselage 2 extends longitudinally along the plane of symmetry P1. Furthermore, the fuselage 2 rests on a skid-type landing gear 5. Specifically, the landing gear 5 is attached to the frame of the fuselage 2.

[0075] It should be noted that, in order to show the landing gear 5, a portion of the fuselage 2 is... Figure 1 The middle part is rendered as transparent.

[0076] The landing gear 5 includes a first skid 6 and a second skid 7. The first skid 6 and the second skid 7 form a plane that can rest on a flat ground 100.

[0077] Therefore, the landing gear 5 includes two transverse members 10 connecting the first skid 6 and the second skid 7, namely the first transverse member 20 and the second transverse member 30. Reference numeral 10 is used to refer to any transverse member, and reference numerals 20 and 30 are used to refer to specific transverse members individually if necessary.

[0078] The first transverse member 20 may form a front transverse member, and the second transverse member 30 may form a rear transverse member. The terms "front" and "rear" are conventionally used by those skilled in the art and are considered in the direction of forward travel of the rotorcraft 1.

[0079] Figure 1 A rotorcraft 1 is shown, having two skids 6, 7, each skid extending from the free rear end to the free front end, and each transverse member 10 connecting the front and rear ends of each skid 6, 7. Other embodiments are possible, for example, as shown in patent FR2749561.

[0080] Each cross member 20, 30 has a first branch 11, 31 that is conventionally fixed to the first skid 6, and a second branch 12, 32 that is conventionally fixed to the second skid 7.

[0081] Furthermore, each transverse member 20, 30 shown in the figure is continuous, including central branches 13, 33 extending from the first branches 11, 31 to the second branches 12, 32. Branches 11, 12, 31, 32 are sometimes referred to as "descent branches" because when the rotorcraft 1 is on the ground, these branches 11, 12, 31, 32 extend from the central branches 13, 33 toward the skids 6, 7 toward the ground. Therefore, the first transverse member 20 sequentially includes a first main descending branch 11, a main central branch 13, and a second main descending branch 12. Similarly, the second transverse member 30 sequentially includes a first secondary descending branch 31, a secondary central branch 33, and a second secondary descending branch 32.

[0082] On a flat surface, as the observer can see, each transverse member 20, 30, and especially each central branch 13, 33, can be divided into an upper and a lower part. For example, the lower and upper parts may meet midway through the transverse member.

[0083] In addition, each horizontal component 10 is fastened to the fuselage 2.

[0084] Therefore, the first transverse member 20 is connected to the fuselage 2 of the rotorcraft 1 by only two fasteners 41, 42. Each fastener 41, 42 surrounds the first transverse member 20 without gaps and is fixed to the frame of the fuselage 2. For example, the two fasteners 41, 42 are fastened to two corresponding spars of the fuselage 2. According to one example, each fastener 41, 42 includes a half-clamp that is fastened to the load-bearing member (i.e., the frame, such as a spar) and clamps the two portions of the lining surrounding the first transverse member 20 without gaps.

[0085] Reference Figure 2 The second horizontal member 30 is supported by the first support member 50 and the second support member 60 only during flight (i.e., when skids 6 and 7 are no longer in contact with the ground). The first support member 50 and the second support member 60 are more simply referred to as "support members".

[0086] Two support members 50 and 60 are fixed to the fuselage 2, particularly to its frame. For example, the first support member 50 and the second support member 60 are respectively fixed to the first spar 96 and the second spar 97 of the fuselage 2. The first spar 96 may also be fixed to a fastener 41, while the second spar 97 is fixed to another fastener 42.

[0087] The first support member 50 and the second support member 60 are completely passed through by the second transverse member 30 in the transverse direction DIR from the first support member 50 to the second support member 60. In particular, the first support member 50 and the second support member 60 are passed through by the central branch 33 of the second transverse member 30.

[0088] Therefore, the first support member 50 and the second support member 60 respectively have two holes, namely, a first hole 51 and a second hole 61. The first hole 51 and the second hole 61 are transversely passed through by the second transverse member 30. The two holes 51 and 61 can be radially defined by two stop surfaces 52 and 62 about the transverse direction DIR. Thus, the first hole 51 can be radially defined by the first stop surface 52 of the first support member 50 relative to the transverse direction DIR. Similarly, the second hole 61 can be radially defined by the second stop surface 62 of the second support member 60 relative to the transverse direction DIR.

[0089] For example, the first support member 50 includes a reinforcement referred to as "first reinforcement 54". The first reinforcement 54 carries a liner referred to as "first liner 53", which extends along the closure line. Therefore, the first stop surface 52 is the inner surface of the first liner 53 radially surrounding the first hole 51. According to the example shown, the first reinforcement 54 includes a U-shaped half-clamp 55, which is fixed, for example, directly to the fuselage 2 or via a connector to the first spar 96.

[0090] For example, the second support 60 includes a reinforcement referred to as "second reinforcement 64". The second reinforcement 64 carries a liner referred to as "second liner 63", which extends along the closure line. Therefore, the second stop surface 62 is the inner surface of the second liner 63 radially surrounding the second hole 61. According to the example shown, the second reinforcement 64 includes a U-shaped half-clamp 65, which is fixed, for example, directly to the fuselage 2 or via a connector to the second spar 97.

[0091] To restrict the degree of freedom of the second transverse member 30 in its translational movement relative to the fuselage 2 in the lateral direction DIR, the central branch 33 may carry the first stop member 81 and the second stop member 82. The first stop member 81 and the second stop member 82 are arranged, for example, laterally between the first support member 50 and the second support member 60. The purpose of the first stop member 81 and the second stop member 82 is to restrict the lateral movement of the second transverse member 30 relative to the fuselage 2 by correspondingly interfering with the shapes of the first support member 50 and the second support member 60.

[0092] For example, the first stop member 81 includes a screw / nut system 811 passing through the second transverse member 30 to secure the first insert 812 to the second transverse member 30. Similarly, the second stop member 82 includes a screw / nut system 821 passing through the second transverse member 30 to secure the second insert 822 to the second transverse member 30. The first insert 812 and the second insert 822 are concealed within... Figure 2 In and Figure 3 As shown in the image.

[0093] Reference Figure 3 The first distance D1 represents the minimum distance between the first stop member 81 or its first insert 812 and the first support member 50. Similarly, the second distance D2 represents the minimum distance between the second stop member 82 or its second insert 822 and the second support member 60. Therefore, when the stop member contacts the corresponding support member, the first distance D1 may be different from the second distance D2. The first distance D1 and the second distance D2 are never both zero.

[0094] This is irrelevant; please refer to [the relevant source] again. Figure 2The second transverse member 30 always maintains gaps 56 and 66 with the two stop surfaces 52 and 62, specifically a first gap 56 with the first stop surface 53 and a second gap 66 with the second stop surface 62. Therefore, the empty space always vertically separates the second transverse member 30 from the bottom 52INT and / or top 52SUP of the first stop surface 52, and also vertically separates the second transverse member 30 from the bottom 62INT and / or top 62SUP of the second stop surface 62. When the rotorcraft 1 is parked on a flat ground 100, as seen by an individual on that ground 100, the top of the stop surfaces 52 and 62 is actually located above the bottom of the stop surfaces 52 and 62.

[0095] To achieve the required clearances 56, 66, the two holes 51, 61 of the two support members 50, 60 can be rectangular in the form of two corresponding longitudinal vertical planes P2, P3. Conversely, in the absence of deformation, the second transverse member 30 can have a circular cross-section in these longitudinal vertical planes P2, P3. Therefore, when the rotorcraft 1 is parked on the horizontal ground 100, the second transverse member 30 has the degree of freedom to translate relative to the two support members 50, 60 along an axis that can be vertical.

[0096] Furthermore, the fuselage 2 supports an intermediate support member 70. This intermediate support member 70 is arranged laterally between the first support member 50 and the second support member 60 according to the lateral direction DIR. In addition, when the rotorcraft 1 is parked on the horizontal ground 100, as can be seen by an individual on the ground, this intermediate support member 70 is arranged above the second transverse member 30.

[0097] The intermediate support member 70 can extend laterally at a distance equal to that of the first support member 50 and the second support member 60 (e.g., in the plane of symmetry P1).

[0098] The intermediate support member 70 may include a base 71, which is fixed to the fuselage 2, for example, to a structure 98 extending from the first spar 96 as described above to the second spar 97. The base 71 may be fastened to the structure 98 in a conventional manner, for example by threaded connections and / or riveting devices.

[0099] The base 71 may support the insert 72.

[0100] Under these conditions, such as Figure 2As shown, (a) during flight, or (b) when the rotorcraft 1 is parked on the ground 100 and in the absence of vertical acceleration and plastic deformation of the second lateral member, the second lateral member 30 presses against the intermediate support 70 located above it. Furthermore, two gaps 56 and 66 exist above the second lateral member 30 within the two supports. In effect, the lower portion 30INF of the second lateral member rests on the bottom 52INF and 62INF of the stop surfaces 52 and 62 of each support 50 and 60, while the gaps 56 and 66 separate the upper portion 30SUP of the second lateral member from the top 52SUP and 62SUP of the stop surfaces 52 and 62 of each support 50 and 60.

[0101] Figures 4 to 8 The operation of the present invention is illustrated.

[0102] Figure 4 The second lateral member 30 during flight is shown. Under these conditions, the intermediate support member 70 and (if applicable) the insert 72 rest on the upper portion 30SUP of the second lateral member 30. Furthermore, gaps 561 and 661 exist between the two supports 50 and 60 above the second lateral member 30. Due to gravity, the lower portion 30INF of the second lateral member 30 rests on the bottom portions 52INF and 62INF of the first stop surface 52 and the second stop surface 62. The second lateral member 30 is suspended below the fuselage 2, yet in contact with the intermediate support member 70.

[0103] During the first operational phase upon landing on the ground 100, or while docked on the ground 100, the intermediate support member 70 applies a force to the second transverse member 30 at approximately the center of the central branch 33. The central branch 33 bends. Therefore, the lower gaps 562, 662 separate the second transverse member 30 from the bottom 52INF, 62INF of each stop surface 52, 62, and the upper gaps 561, 661 separate the second transverse member 30 from the top 52SUP, 62SUP of each stop surface 52, 62.

[0104] Therefore, the landing gear 5 behaves similarly to a landing gear with three fastening points. Furthermore, the use of the intermediate support member 70 allows the roll vibration modes of the fuselage 2 to be decoupled from its landing gear 5.

[0105] Figure 5 The image shows a rotorcraft 1 parked on the ground but with minimal mass, while... Figure 6 The image shows a rotorcraft 1 with maximum mass, parked on the ground.

[0106] Under these conditions, as long as the deformation experienced by the second horizontal member 30 is below the limit deformation, the second horizontal member 30 will introduce force into the fuselage 2 only through the intermediate support member 70.

[0107] Conversely, during a hard landing, referencing Figure 7 The second transverse member 30 continues to bend and enters the second operating stage. The switch from the first operating stage to the second operating stage occurs when the deformation of the second transverse member exceeds the limit deformation, and may, for example, correspond to the transition from the deformation stage of the elastic range of the second transverse member to the deformation stage of the plastic range of the second transverse member.

[0108] Then, the second horizontal member 30 not only presses against the intermediate support member 70, but also presses against the top 52SUP and 62SUP of the stop surfaces 52 and 62.

[0109] If the deformation continues, refer to... Figure 8 The second lateral member 30 moves away from the intermediate support member 70, but remains in contact with the tops 52SUP and 62SUP of the stop surfaces 52 and 62. The landing gear 5 thus behaves like a landing gear with four fastening points. If necessary, the second lateral member 30 continues to bend and plastically deform to absorb some of the energy generated by landing. As a result, when the second lateral member 30 undergoes deformation greater than its limit deformation, it introduces force into the fuselage 2 only through the two supports 50 and 60.

[0110] Naturally, there will be many variations in the implementation of this invention. Although several embodiments have been described above, it should be readily understood that it is impossible to exhaustively identify all possible embodiments. Without departing from the scope of this invention, it is naturally conceivable to replace any of the described devices with equivalent means.

Claims

1. A rotorcraft having a rotor and a skid-type landing gear, the landing gear having a first skid and a second skid, a first lateral member and a second lateral member, the first lateral member and the second lateral member each connecting the first skid to the second skid, the first lateral member and the second lateral member each having a first branch fixed to the first skid and a second branch fixed to the second skid, and a central branch connecting the first branch to the second branch, the first lateral member being connected to the fuselage of the rotorcraft by only two fasteners. The second transverse member is supported during flight by only two supports fastened to the fuselage, through which the second transverse member passes. Each support includes a hole defined by a stop surface of the support. The second transverse member is always separated from each stop surface by a gap. The fuselage supports an intermediate support member, which is laterally arranged between the two supports. When the rotorcraft is parked on a level ground, the intermediate support member is above the second transverse member. When the rotorcraft is parked on the ground and in the absence of plastic deformation and vertical acceleration of the second transverse member, the second transverse member rests against the intermediate support member, and the gap exists above the second transverse member.

2. The rotorcraft according to claim 1, in, The second transverse member has a lower part and an upper part in the vertical direction. When the rotorcraft is parked on the ground and in the absence of plastic deformation and vertical acceleration of the second transverse member, the lower part rests on the bottom of the stop surface of each support member, while the gap separates the upper part from the top of the stop surface of each support member and the upper part presses against the intermediate support member.

3. The rotorcraft according to claim 1, in, When on the ground, as long as the deformation experienced by the second horizontal member is below the limit deformation, the second horizontal member introduces force into the fuselage only through the intermediate support member; when the deformation experienced by the second horizontal member is greater than the limit deformation, the second horizontal member introduces force into the fuselage only through the two support members.

4. The rotorcraft according to claim 1, in, Each support includes a reinforcement that carries the liner, the liner including the stop surface of the support.

5. The rotorcraft according to claim 4, in, The reinforcing member includes a U-shaped half-clamp fixed to the body.

6. The rotorcraft according to claim 1, in, The intermediate support member includes a base fixed to the fuselage, the base supporting the insert, and when the rotorcraft is parked on the ground and in the absence of plastic deformation and vertical acceleration of the second transverse member, the second transverse member presses against the insert.

7. The rotorcraft according to claim 1, in, The two holes of the two supports have a rectangular shape in two corresponding longitudinal vertical planes, and the second horizontal member has a circular cross section in the longitudinal vertical plane without deformation.

8. The rotorcraft according to claim 1, in, The two support members are correspondingly fastened to the two wing spars of the fuselage, the two fasteners are correspondingly fastened to the two wing spars, and the intermediate support member is fastened to a structure extending from one wing spar to the other.

9. The rotorcraft according to claim 1, in, The two support members include a first support member and a second support member. The central branch of the second horizontal member carries a first stop member and a second stop member. The first stop member and the second stop member are configured to restrict the degree of freedom of movement of the second horizontal member relative to the fuselage in the direction from the first support member to the second support member by interfering with the corresponding shapes of the first support member and the second support member.

10. The rotorcraft according to claim 9, in, When the first stop member contacts the first support member, the second stop member does not contact the second support member, and when the second stop member contacts the second support member, the first stop member does not contact the first support member.

11. The rotorcraft according to claim 1, in, The intermediate support member extends at a distance equal to that of the two supports.

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