Helicopter main rotor blade folding and securing device

Abstract

The present application belongs to the field of helicopter technology system, and discloses a kind of main blade folding fixing device of helicopter, including blade fixed rod system and bottom support rod system, bottom support rod system is fixedly installed in the bottom of the belly of helicopter, bottom support rod system extends to the front end of helicopter, blade fixed rod system is installed above the extended part of bottom support rod system, blade fixed rod system extends to the above of helicopter and forms the support structure of helicopter front folding blade, bottom support rod system and blade fixed rod system are high rigidity structure;Wherein, blade fixed rod system is respectively equipped with left and right two blade support rods for supporting and fixing two folded blades.The main blade folding fixing design of certain type of helicopter uses this type of device to fix the helicopter front folding blade, when the helicopter is transported, the main blade will not knock the inner wall of the cabin of transport machine, and the strength and rigidity design requirements are met.At the same time, the whole fixing device also considers the convenience of disassembly and assembly, which is convenient for daily use and maintenance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of helicopter technology system, and relates to a blade fixing device and design method during the transportation and parking of a helicopter, in particular to a main blade folding fixing device of a helicopter. BACKGROUND

[0002] When a helicopter is transported by air or parked in a ship hangar, the main blades of the helicopter need to be folded to reduce the lateral space for parking. During the movement of the air transportation platform and the ship transportation platform, the main blades will generate inertial load, and the folding fixing device of the main blades needs to reliably constrain the folded main blades. The blade folding fixing device is generally composed of a plurality of rod systems, and the rod systems need to meet the design requirements of strength and stiffness at the same time. Especially in the air transportation state, the end of the folded main blade of the helicopter is close to the inner wall of the transport machine, and the folding fixing device with poor stiffness will cause the main blade to bump into the transport machine body, which may cause serious flight accidents.

[0003] A main blade folding fixing device of a helicopter is needed to ensure that the deformation of the blade end does not exceed the limit value under a specific main blade inertial load, and the device body and the connection also meet the strength design requirements. SUMMARY

[0004] OBJECTIVE

[0005] The present application provides a main blade folding fixing device of a helicopter, which provides sufficient constraint stiffness for the folded blades to ensure that the blades do not appear out-of-limit displacement when the helicopter is transported; when the support rod system is designed, the device is also easy to disassemble.

[0006] The technical scheme of the present application is as follows:

[0007] A main blade folding fixing device of a helicopter, comprising a blade fixing rod system and a bottom support rod system, the bottom support rod system is installed and fixed at the bottom of the belly of the helicopter, the bottom support rod system extends to the front end of the helicopter, the blade fixing rod system is installed above the extended part of the bottom support rod system, the blade fixing rod system extends upwards to form a support structure for the folded main blades in front of the helicopter, and the bottom support rod system and the blade fixing rod system are both high-stiffness structures; wherein the blade fixing rod system is respectively provided with left and right two blade support rods for supporting and fixing the two folded blades.

[0008] Further, the bottom of the blade fixing rod system is a fixed first horizontal rod, the first horizontal rod is perpendicular to the heading direction of the helicopter, two groups of herringbone rods are respectively installed on the left half and the right half of the first horizontal rod, and the top of each of the two groups of herringbone rods is respectively provided with a blade support rod for supporting and fixing the two folded blades.

[0009] Further, the two groups of herringbone-shaped rods comprise a first vertical rod, a first inclined rod, a second inclined rod and a second vertical rod, the first vertical rod and the second vertical rod are respectively vertically installed at two ends of the first horizontal rod, the first inclined rod and the second inclined rod are respectively installed at two sides of the middle part of the first horizontal rod, the top of the first vertical rod and the first inclined rod are connected to form a group of herringbone-shaped rods, and the top of the second inclined rod and the second vertical rod are connected to form another group of herringbone-shaped rods.

[0010] Further, the connection position of the first vertical rod and the first horizontal rod and the connection position of the first inclined rod and the first horizontal rod are located on the same side of the first horizontal rod, and the connection position of the second inclined rod and the first horizontal rod and the connection position of the second vertical rod and the first horizontal rod are located on the other same side of the first horizontal rod.

[0011] Further, the bottom support rod system is installed and fixed on the bottom of the fuselage of the helicopter through four reserved openings of the bottom longitudinal beam of the fuselage of the helicopter.

[0012] Further, the bottom support rod system comprises a first longitudinal rod and a second longitudinal rod, the four reserved openings of the bottom of the fuselage of the helicopter are distributed in a square shape as a whole, the rear end of the first longitudinal rod is installed on one reserved opening through a connecting structure, the middle part of the first longitudinal rod is installed on another reserved opening through a connecting structure, the front end of the first longitudinal rod extends out of the projection range of the helicopter and is connected with the first horizontal rod, the rear end of the second longitudinal rod is installed on one reserved opening through a connecting structure, the middle part of the second longitudinal rod is installed on another reserved opening through a connecting structure, and the front end of the second longitudinal rod extends out of the projection range of the helicopter and is connected with the first horizontal rod.

[0013] Further, the bottom support rod system further comprises a first short rod, a first triangular rod, a second triangular rod, a second short rod, a third triangular rod and a fourth triangular rod, wherein the first triangular rod, the second triangular rod and the first longitudinal rod form a triangular rod system with the first longitudinal rod as the base, and the first short rod is arranged on the perpendicular line of the triangle with the first longitudinal rod as the base; the third triangular rod, the fourth triangular rod and the second longitudinal rod form a triangular rod system with the second longitudinal rod as the base, and the second short rod is arranged on the perpendicular line of the triangle with the second longitudinal rod as the base. The first longitudinal rod, the first triangular rod, the first short rod and the second triangular rod form a triangular rod system, the second longitudinal rod, the third triangular rod, the second short rod and the fourth triangular rod form another triangular rod system, and the vertical support rigidity of the first horizontal rod at the connection points D and E is improved.

[0014] Further, the second horizontal rod and the third inclined rod are further included, the two ends of the second horizontal rod are respectively connected to the bottom ends of the two triangular rod systems, and the third inclined rod is obliquely arranged between the first short rod and the second short rod.

[0015] Further, the installation interface position of the abdomen of the helicopter fuselage is a square four installation interfaces, the first longitudinal rod and the second longitudinal rod are respectively installed on the two installation interfaces arranged in the heading direction; wherein the two installation interfaces connected by the first longitudinal rod are point C and point A from the rear to the front in the heading direction, and the two installation interfaces connected by the second longitudinal rod are point G and point B from the rear to the front in the heading direction; the first longitudinal rod and the second longitudinal rod are connected with the helicopter at points A and B through ring joints respectively, so that the first longitudinal rod and the second longitudinal rod do not transmit the heading load at points A and B; the first longitudinal rod and the second longitudinal rod are connected with the helicopter at points C and G through barrel joints respectively, so that the lateral load and the vertical load of the first longitudinal rod and the second longitudinal rod at points C and G are transmitted to the helicopter fuselage through the barrel joints.

[0016] The beneficial effects of the present application are:

[0017] In the folding and fixing design of the main rotor blade of a certain type of helicopter, the device is used to fix the front folding rotor blade of the helicopter. When the helicopter is transported by a certain type of transport aircraft, the main rotor blade of the helicopter will not bump into the inner wall of the cabin of the transport aircraft under the II level limit overload, meeting the strength and rigidity design requirements. At the same time, the entire fixing device also considers the convenience of disassembly and assembly, facilitating daily use and maintenance. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is a schematic diagram of the rod system of the main rotor blade folding and fixing device of the helicopter of the present application.

[0019] Figure 2 It is a force diagram of the blade fixing rod system, i.e. the herringbone rod system, of the present application.

[0020] Figure 3 It is a force diagram of the bottom support rod system, i.e. the longitudinal rod system, of the present application.

[0021] Figure 4 It is a schematic diagram of the ring joint connected with the body at points A and B of the present application.

[0022] Figure 5 It is a schematic diagram of the barrel joint connected with the body at points C and G of the present application.

[0023] Figure 6 It is a schematic diagram of the mechanical equivalent model of the main rotor blade folding device of the present application.

[0024] Figure 7 It is a schematic diagram of the lateral force at the blade clamping position of the present application.

[0025] Figure 8 It is a schematic diagram of the distribution of force at the front vertex of the longitudinal triangular support of the present application.

[0026] Figure 9 It is a schematic diagram of the distribution of pitch moment at the front vertex of the longitudinal triangular support of the present application.

[0027] Figure 10 Force lateral, vertical force distribution schematic diagram for the connection between point A, B and the fuselage of the application;

[0028] Figure 11 Torque distribution schematic diagram for the connection between point A, B and the fuselage of the application;

[0029] Figure 12 Three-way force distribution schematic diagram for the connection between point C, D and the fuselage of the application;

[0030] Figure 13 Torque distribution schematic diagram for the connection between point C, D and the fuselage of the application;

[0031] Figure 14 Maximum deformation schematic diagram for the blade support of the application;

[0032] Figure 15 Maximum stress schematic diagram for the blade support rod system of the application;

[0033] In the figure: 1-first vertical rod, 2-first inclined rod, 3-second inclined rod, 4-second vertical rod, 5-first horizontal rod, 6-first longitudinal rod, 7-first triangular rod, 8-first short rod, 9-second triangular rod, 10-second longitudinal rod, 11-third triangular rod, 12-second short rod, 13-fourth triangular rod, 14-second horizontal rod, 15-third inclined rod. DETAILED DESCRIPTION

[0034] This part is an embodiment of the application, which is used to explain and illustrate the technical solutions of the application. In the case of no conflict, the embodiments of the application and the features in the embodiments can be combined with each other.

[0035] In the description of the application, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship as the orientation or positional relationship given to the drawings, and are only for the purpose of facilitating the description of the application and simplifying the description, and do not indicate or imply that the device or the case must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the application. In addition, the terms "first", "second" and the like are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implying the number of the indicated technical features. Therefore, the features defined with "first", "second" and the like can explicitly or implicitly include more features. In the description of the application, unless otherwise stated, the meaning of "multiple" is two or more.

[0036] In the description of the present application, it should be noted that unless otherwise specified and limited, the terms "mounting", "connecting", "connecting" should be interpreted broadly, for example, it can be fixed connection, or detachable connection or integrated connection; it can be mechanical connection, or point connection; it can be direct connection, or indirect connection through intermediate medium, or internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0037] A helicopter main blade folding fixing device of the present application is shown in Figure 1 The bottom support rod system is installed and fixed at the bottom of the belly of the helicopter through four reserved openings of the longitudinal beam position of the bottom of the belly of the helicopter.

[0038] The bottom of the blade fixing rod system is a fixed first horizontal rod 5, which is perpendicular to the direction of the helicopter. Two groups of herringbone rods are installed on the left and right halves of the first horizontal rod 5, respectively, and each group of herringbone rods is provided with a blade support rod for supporting and fixing the two folded blades.

[0039] The two groups of herringbone rods include a first vertical rod 1, a first inclined rod 2, a second inclined rod 3 and a second vertical rod 4. The first vertical rod 1 and the second vertical rod 4 are respectively installed vertically at the two ends of the first horizontal rod 5. The first inclined rod 2 and the second inclined rod 3 are respectively installed on the front and rear sides of the middle part of the first horizontal rod 5. The top of the first vertical rod 1 and the first inclined rod 2 is connected to form a group of herringbone rods, and the top of the second inclined rod 3 and the second vertical rod 4 is connected to form another group of herringbone rods.

[0040] The connection positions of the first vertical rod 1 and the first inclined rod 2 with the first horizontal rod 5 are located on the same side of the first horizontal rod 5, and the connection positions of the second inclined rod 3 and the second vertical rod 4 with the first horizontal rod 5 are located on the other side of the first horizontal rod 5. Force analysis: the two blades are subjected to lateral overload at the top support point to generate lateral load Fy. The generated first inclined rod 2 and second inclined rod 3 axial load values are approximately opposite in direction, which offsets the deformation at point E and improves the stiffness of horizontal rod 5.

[0041] The bottom support rod system is installed and fixed at the bottom of the belly of the helicopter through four reserved openings of the longitudinal beam position of the bottom of the belly of the helicopter.

[0042] The bottom support rod system comprises a first longitudinal rod 6 and a second longitudinal rod 10, four reserved openings on the bottom of the helicopter belly are distributed in a square shape, the rear end of the first longitudinal rod 6 is installed on one reserved opening through a connecting structure, the middle part of the first longitudinal rod 6 is installed on another reserved opening through a connecting structure, the front end of the first longitudinal rod 6 extends out of the projection range of the helicopter and is connected to the first horizontal rod 5; the rear end of the second longitudinal rod 10 is installed on one reserved opening through a connecting structure, the middle part of the second longitudinal rod 10 is installed on another reserved opening through a connecting structure, and the front end of the second longitudinal rod 10 extends out of the projection range of the helicopter and is connected to the first horizontal rod 5.

[0043] The bottom support rod system further comprises a first short rod 8, a first triangular rod 7, a second triangular rod 9, a second short rod 12, a third triangular rod 11 and a fourth triangular rod 13; wherein the first triangular rod 7, the second triangular rod 9 and the first longitudinal rod 6 form a triangular rod system with the first longitudinal rod 6 as the bottom side, and the first short rod 8 is arranged on the vertical line of the triangle with the first longitudinal rod 6 as the bottom side; the third triangular rod 11, the fourth triangular rod 13 and the second longitudinal rod 10 form a triangular rod system with the second longitudinal rod 10 as the bottom side, and the second short rod 12 is arranged on the vertical line of the triangle with the second longitudinal rod 10 as the bottom side. The first longitudinal rod 6, the first triangular rod 7, the first short rod 8 and the second triangular rod 9 form a triangular rod system, the second longitudinal rod 10, the third triangular rod 11, the second short rod 12 and the fourth triangular rod 13 form another triangular rod system, and the vertical support stiffness of the first horizontal rod 5 at the connecting points D and E is improved.

[0044] The second horizontal rod 14 and the third inclined rod 15 are further included, the two ends of the second horizontal rod 14 are respectively connected to the bottom ends of the two triangular rod systems, and the third inclined rod 15 is arranged between the first short rod 8 and the second short rod 12.

[0045] The installation interface positions of the helicopter belly are four square-shaped installation interfaces, the first longitudinal rod 6 and the second longitudinal rod 10 are respectively installed on two installation interfaces arranged in the heading direction; wherein the two installation interfaces connected by the first longitudinal rod 6 are point C and point A from rear to front in the heading direction, and the two installation interfaces connected by the second longitudinal rod 10 are point G and point B from rear to front in the heading direction; the first longitudinal rod 6 and the second longitudinal rod 10 are connected to the helicopter at point A and point B through ring joints, so that the first longitudinal rod 6 and the second longitudinal rod 10 do not transmit the heading load at point A and point B; the first longitudinal rod 6 and the second longitudinal rod 10 are connected to the helicopter at point C and point G through barrel joints, so that the lateral load and the vertical load of the first longitudinal rod 6 and the second longitudinal rod 10 at point C and point G are transmitted to the helicopter body through the barrel joints.

[0046] Points D and E have forces in x, y and z directions, and the paths of the loads diffused from points D and E to the body connecting points are the same. The load transmission is described by taking point D as an example. Figure 3 )。

[0047] The x-direction (heading) load at point D is: Fdx = Fcx;

[0048] Lateral load in the y-direction at point D: Fdy = Fay - Fcy;

[0049] The z-direction (vertical) load at point D is: Fdz = Faz - Fcz;

[0050] Where Fdx and Fcx represent the heading loads at points D and C, respectively; Fdy, Fay, and Fcy represent the lateral loads at points D, A, and C, respectively; and Fdz, Faz, and Fcy represent the vertical loads at points D, A, and C, respectively.

[0051] To ensure that points A and B do not transmit loads in the x-direction, the following method is adopted: Figure 4 The annular joint is shown. The first longitudinal rod 6 and the second longitudinal rod 10 pass directly through the joint. To facilitate the rotation of the first longitudinal rod 6 and the second longitudinal rod 10 around the y-axis and z-axis at points A and B during installation, the rods are inserted into the joint at points C and G. The inner surface of the annular joint is designed as a circular arc surface, see... Figure 4 Sectional view.

[0052] The y-direction and z-direction loads at points A and B are achieved through the contact between the first longitudinal bar 6, the second longitudinal bar 10 and the annular joint.

[0053] To achieve the transfer of x-direction load between points C and G, the first longitudinal member 6 and the second longitudinal member 10 are inserted. Figure 5 The barrel-shaped joint shown is connected to the end of the long rod using a pin. The y- and z-direction loads at points C and G are achieved through the contact between the ends of the first longitudinal rod 6 and the second longitudinal rod 10 and the inner wall of the joint.

[0054] To ensure the lateral stability of the two longitudinal triangular trusses, a triangular stabilizing truss is installed between points A and B. It consists of a first short member 8, a second horizontal member 14, and a third diagonal member 15.

[0055] The first horizontal bar 5, first vertical bar 6, and second vertical bar 10 mainly bear bending loads. To ensure bending stiffness, they are made of 30CrMnSiA alloy steel. The first vertical bar 1, first diagonal bar 2, second diagonal bar 3, second vertical bar 4, first triangular bar 7, first short bar 8, second triangular bar 9, third triangular bar 11, second short bar 12, fourth triangular bar 13, second horizontal bar 14, and third diagonal bar 15 mainly bear axial loads and are made of 2A12 aluminum alloy. This design ensures that the entire blade fixing device meets both strength and stiffness requirements while minimizing weight.

[0056] Finally, a mechanical analysis model of the main blade fixing device was established to simulate the strength and stiffness of the blade under lateral overload when the blade is clamped.

[0057] Key aspects of this invention include:

[0058] 1. Each blade has two support rods underneath, adopting a "V"-shaped main and auxiliary support rod design, which improves structural stability.

[0059] 2. The first crossbar 5 extends a certain distance beyond the longitudinal strut section, which effectively ensures structural rigidity and limits deformation. When the propeller blades supported above experience inertial overload and deflect to one side of the fuselage, the loads on the first diagonal bar 2 and the second diagonal bar 3 can be offset, thereby reducing the displacement at the end of the crossbar and limiting overall structural deformation.

[0060] 3. Due to the relatively long longitudinal steel pipe, a design was made to provide sufficient vertical stiffness. Figure 1 The triangular support system, consisting of the first longitudinal bar 6, the first triangular bar 7, the first short bar 8, the second triangular bar 9, the first longitudinal bar 10, the third triangular bar 11, the second short bar 12, and the fourth triangular bar 13, forms a triangular support structure. These structures connect to the front, middle, and rear of the long steel pipe, respectively, reducing structural deformation. The apex of the triangular support base is positioned so that the helicopter will not hit the ground during transport.

[0061] 4. To prevent lateral instability of the longitudinal struts, a design was implemented. Figure 1 The triangular support rod system shown in the area between midpoints A and B forms a triangular support structure, which makes the lateral deformation of the two longitudinal steel pipes more coordinated and prevents the lower support rod system from twisting as a whole when the blade moves laterally.

[0062] 5. Each pipe and connector is connected with a quick-release pin, which facilitates disassembly and assembly, reduces workload, and improves work efficiency.

[0063] The installation and usage method of this invention is as follows:

[0064] After the helicopter is parked, the first longitudinal rod 6, the first triangular rod 7, the first short rod 8, and the second triangular rod 9 are connected by a connector using pins to form a longitudinal triangular support rod system.

[0065] The first longitudinal rod 10, the third triangular rod 11, the second short rod 12, and the fourth triangular rod 13 are connected by a joint using pins to form a longitudinal triangular support rod system.

[0066] The second horizontal bar 14, the third diagonal bar 15, and the second short bar 12 are connected by pins to form a lateral triangular support structure.

[0067] After assembly, use pins to connect the connector to the mounting device at the lower frame beam of the fuselage;

[0068] The first crossbar 5 is connected to the end joint of the longitudinal long bar using a pin to form a transverse blade support structure.

[0069] Then the blade is moved to the correct position using the first vertical rod, the second vertical rod 4, and then supported and fixed using the first auxiliary diagonal rod 2 and the second diagonal rod 3, and is fixed on the first horizontal rod 5 through a pin.

[0070] The joint material is 30CrMnSiA, the pin material is 30CrMnSiA, and the radius is 4 mm.

[0071] The materials of the first horizontal rod 5, the first vertical rod 6 and the second vertical rod 10 are 30CrMnSiA, and the other rods are made of aluminum alloy material 2A12.

[0072] Each connection adopts a quick disassembly and assembly structure, universal joints are arranged between the blade clamps and the support rods, length adjusting mechanisms are arranged on the support rods, and the use requirements of quick disassembly, folding position error compensation and the like can be met.

[0073] The design principle and verification of the application are as follows:

[0074] 1. The first horizontal rod 5, the first vertical rod 6 and the second vertical rod 10 adopt beam element simulation, can transmit force and torque, other rod systems adopt two-force rod elements, and only bear axial force, as shown in Figure 6 ;

[0075] 2. The lateral load Fy of the blade clamping support is 890N, as shown in Figure 7 ;

[0076] 3. Through the first vertical rod 1, the first diagonal rod 2, the second diagonal rod 3 and the second vertical rod 4, the vertical force at the connecting point D is 2750N, the heading force is 12800N, the vertical force at the point E is 2790N, and the heading force is 13000N, as shown in Figure 8 ; The pitching bending moment at the connecting points D and E is 642000N.mm and 652000N.mm, as shown in Figure 9 ;

[0077] 4. The lateral load at the connecting point A with the fuselage is 1680N, and the vertical load is 14400N. The lateral load at the point B is 1340N, and the vertical load is 14600N, as shown in Figure 10 . The torsional moments distributed at the points A and B are 58600N.mm and 41600N.mm, respectively, as shown in Figure 11 ;

[0078] 5. The three-way forces distributed at the connecting point C with the fuselage are 2400N, 681N and 8660N respectively. The three-way forces distributed at the point G are 2400N, 591N and 8780N respectively, as shown in Figure 12 ; The torsional moments distributed at the points C and G are 77700N.mm and 64700N.mm respectively, as shown in Figure 13 ;

[0079] 6. The maximum lateral displacement at the top is 226mm, which is less than the distance between the blade and the side structure, preventing collision. The bottom structure experiences minimal deformation, and the strut system does not exhibit instability, providing stable support for the main blade. Figure 14 ;

[0080] 7. The maximum stress of the support rod system is 588 MPa, located at point E of the first crossbar. The material is 30CrMnSiA, with a tensile strength of 980 MPa. The safety margin is (980 / 588-1)×100%=66.7%>0, which meets the strength design requirements. Figure 15 .

[0081] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent transformations or modifications made according to the spirit and essence of the present invention should be covered within the scope of protection of the present invention. The technologies, shapes, and structures not described in detail in this invention are all well-known technologies.

Claims

1. A folding and securing device for a main rotor blade of a helicopter, characterized in that, The blade fixing rod system and the bottom support rod system are provided, the bottom support rod system is installed and fixed at the belly bottom of the helicopter, the bottom support rod system extends to the front end of the helicopter, the blade fixing rod system is installed above the extended part of the bottom support rod system, the blade fixing rod system extends upwards to form a support structure of the front folding blade of the helicopter, and the bottom support rod system and the blade fixing rod system are high-rigidity structures; wherein the blade fixing rod system is provided with two left and right blade support rods for supporting and fixing the two folded blades. The bottom of the blade fixing rod system is a fixed first horizontal rod (5), the first horizontal rod (5) is perpendicular to the direction of the helicopter, two groups of herringbone rods are installed on the left half and the right half of the first horizontal rod (5), and the top of each of the two groups of herringbone rods is provided with a blade support rod for supporting and fixing the two folded blades. The bottom support rod system is installed and fixed at the belly bottom of the helicopter through four reserved openings of the belly bottom longitudinal beam of the helicopter. The bottom support rod system includes a first longitudinal rod (6) and a second longitudinal rod (10), the four reserved openings of the belly bottom longitudinal beam of the helicopter are distributed in a square shape as a whole, the rear end of the first longitudinal rod (6) is installed on one reserved opening through a connecting structure, the middle part of the first longitudinal rod (6) is installed on another reserved opening through a connecting structure, the front end of the first longitudinal rod (6) extends out of the projection range of the helicopter and is connected with the first horizontal rod (5); the rear end of the second longitudinal rod (10) is installed on one reserved opening through a connecting structure, the middle part of the second longitudinal rod (10) is installed on another reserved opening through a connecting structure, and the front end of the second longitudinal rod (10) extends out of the projection range of the helicopter and is connected with the first horizontal rod (5).

2. A device for folding and securing a main rotor blade of a helicopter according to claim 1, characterized in that The two groups of herringbone rods include a first vertical rod (1), a first inclined rod (2), a second inclined rod (3) and a second vertical rod (4), the first vertical rod (1) and the second vertical rod (4) are installed vertically on the two ends of the first horizontal rod (5), the first inclined rod (2) and the second inclined rod (3) are installed on the front and rear sides of the middle part of the first horizontal rod (5), and the top of the first vertical rod (1) and the first inclined rod (2) is connected to form one group of herringbone rods, and the top of the second inclined rod (3) and the second vertical rod (4) is connected to form the other group of herringbone rods.

3. A device for folding and securing a main rotor blade of a helicopter according to claim 2, characterized in that The connecting positions of the first vertical rod (1) and the first horizontal rod (5) and the first inclined rod (2) and the first horizontal rod (5) are located on the same side of the first horizontal rod (5), the connecting positions of the second inclined rod (3) and the first horizontal rod (5) and the second vertical rod (4) and the first horizontal rod (5) are located on the other same side of the first horizontal rod (5); stress analysis: the two blades are subjected to lateral overload to generate lateral load Fy at the top support point, the generated first inclined rod (2) and the second inclined rod (3) axial load values are approximately opposite, which offsets the deformation at point E and improves the rigidity of the first horizontal rod (5).

4. A folding and securing device for a main rotor blade of a helicopter according to claim 1, characterized in that The bottom support rod system further comprises a first short rod (8), a first triangular rod (7), a second triangular rod (9), a second short rod (12), a third triangular rod (11), and a fourth triangular rod (13); wherein the first longitudinal rod (6) is taken as a bottom side, the first triangular rod (7), the second triangular rod (9), and the first longitudinal rod (6) form a triangular rod system, and the first short rod (8) is arranged on a vertical line of the triangle with the first longitudinal rod (6) as the bottom side; the second longitudinal rod (10) is taken as a bottom side, the third triangular rod (11), the fourth triangular rod (13), and the second longitudinal rod (10) form a triangular rod system, and the second short rod (12) is arranged on a vertical line of the triangle with the second longitudinal rod (10) as the bottom side; the first longitudinal rod (6), the first triangular rod (7), the first short rod (8), and the second triangular rod (9) form a triangular rod system, the second longitudinal rod (10), the third triangular rod (11), the second short rod (12), and the fourth triangular rod (13) form another triangular rod system, and the vertical support rigidity of the first horizontal rod (5) at the connecting points D and E is improved.

5. A device for folding and securing a main rotor blade of a helicopter according to claim 4, characterized in that The bottom support rod system further comprises a second horizontal rod (14) and a third inclined rod (15), both ends of the second horizontal rod (14) are connected to the bottom ends of the two triangular rod systems respectively, and the third inclined rod (15) is arranged obliquely between the first short rod (8) and the second short rod (12).

6. A folding and securing device for a main rotor blade of a helicopter according to claim 1, characterized in that The installation interface positions of the helicopter fuselage abdomen are four square installation interfaces, the first longitudinal rod (6) and the second longitudinal rod (10) are installed in the two installation interfaces arranged in the heading direction respectively; wherein the two installation interfaces connected by the first longitudinal rod (6) are point C and point A from the rear to the front in the heading direction, and the two installation interfaces connected by the second longitudinal rod (10) are point G and point B from the rear to the front in the heading direction; the first longitudinal rod (6) and the second longitudinal rod (10) are connected with the helicopter at point A and point B through ring joints respectively, so that the first longitudinal rod (6) and the second longitudinal rod (10) do not transmit the heading load at point A and point B; the first longitudinal rod (6) and the second longitudinal rod (10) are connected with the helicopter at point C and point G through barrel joints respectively, so that the lateral load and the vertical load of the first longitudinal rod (6) and the second longitudinal rod (10) at point C and point G are transmitted to the helicopter fuselage through the barrel joints.

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