Helicopter tail boom structure severe damage repair method

Abstract

The application discloses a kind of serious damage repair methods of helicopter tail beam structure, comprising: determining the technical parameters of complete tail beam, and the three-dimensional numerical model of tail beam is established reversely by CATIA software;Develop special jig and make replacement bulkhead, and a plurality of bulkhead positioning tool, a plurality of stringer positioning tool and a plurality of bearing positioning tool arranged in the special jig;Cut the skin of damage area, bulkhead, stringer, and scrap;Install replacement bulkhead, and use bulkhead positioning tool to position;Install stringer, and stringer positioning tool is positioned;The upper bearing and lower bearing are positioned and installed by bearing positioning tool;According to stress analysis of tail beam, determine the skin repair tolerance, and make skin repair standard;Step eight, according to skin repair tolerance and skin repair standard, carry out skin riveting.The application realizes the repair of seriously damaged tail beam, meets the technical requirements of seriously damaged tail beam repair, so as to guarantee the training needs of helicopter equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of helicopter repair, and more particularly to a method for repairing a severely damaged tail boom structure of a helicopter. BACKGROUND

[0002] The Mi series helicopter is a large transport helicopter introduced from Russia by the Chinese army since the 1990s; during the tail boom overhaul, according to the maintenance outline requirements, the tail boom skin, spacer frame, stringer and other conventional inspections are carried out, such as skin scratches, corrosion, cracks and other faults, and when the above faults occur, the local reinforcement repair is carried out according to the general process method, but such a method is only suitable for minor damage of the tail boom; for the repair of the severely damaged tail boom, such as the severe fracture and damage of the skin, spacer frame, stringer and transmission shaft bearing, there is no corresponding repair method.

[0003] In the case of severe fracture and damage of the skin, spacer frame, stringer and transmission shaft bearing, the existing technical data only clearly defines the repair technical standards of the typical structure damage of the tail boom, and lacks the repair method of replacing the spacer frame, stringer, transmission shaft bearing and the skin lap joint; thus, the existing technical data cannot meet the technical requirements of repairing the severely damaged tail boom, which affects the training needs of the helicopter equipment.

[0004] Therefore, how to meet the technical requirements of repairing the severely damaged tail boom is a problem to be solved by the personnel in this technical field. SUMMARY

[0005] An object of the present application is to solve at least the above problems and / or deficiencies, and to provide at least the advantages described later.

[0006] In order to achieve these objects and other advantages of the present application, a method for repairing a severely damaged tail boom structure of a helicopter is provided, comprising the following steps:

[0007] Step one, determine the technical parameters of the complete tail boom, and establish a tail boom three-dimensional numerical model through reverse engineering by using CATIA software;

[0008] Step two, develop a special jig and make a replacement spacer frame according to the tail boom three-dimensional numerical model and the damage condition of the damaged tail boom, and set a plurality of spacer frame positioning tools, a plurality of stringer positioning tools and a plurality of bearing positioning tools in the special jig;

[0009] Step three, fix the damaged tail boom on the special jig by bolts, cut the skin, spacer frame and stringer in the damaged area, and scrap them;

[0010] Step four, install the replacement spacer frame and position it with the spacer frame positioning tool;

[0011] Step five, install the stringer and position it with the stringer positioning tool;

[0012] Step six, the upper bearing and the lower bearing are positioned and installed by the bearing positioning tool;

[0013] Step seven, according to the tail beam stress analysis, the skin repair tolerance is determined, and the skin repair standard is formulated;

[0014] Step eight, according to the skin repair tolerance and the skin repair standard, the skin riveting is carried out, and after the skin repair standard is inspected, the paint is sprayed.

[0015] Preferably, wherein the method for determining the technical parameters of the complete tail beam is:

[0016] Step S11, using a three-dimensional scanning device, collecting the skin aerodynamic appearance point cloud data of the complete tail beam of multiple helicopters of the same type and same batch, the relative position point cloud data of the bulkhead and the stringer, and the appearance point cloud data and assembly position point cloud data of the bearing;

[0017] Step S12, analyzing and optimizing the skin aerodynamic appearance point cloud data, and the appearance point cloud data and assembly position point cloud data of the bearing, to determine the technical parameters of the complete tail beam.

[0018] Preferably, wherein the special jig comprises:

[0019] The support is provided with a bulkhead positioning profile plate on both sides for connecting with the bulkheads at both ends of the tail beam.

[0020] A plurality of tail beam positioning clamping plates for supporting and positioning the complete part of the damaged tail beam are symmetrically arranged in the support.

[0021] Preferably, wherein the bulkhead positioning tool comprises:

[0022] The hinge seat is fixedly connected with the support;

[0023] Two semicircular positioning clamping plates are hingedly connected with the hinge seat at the top ends, and the two semicircular positioning clamping plates are mirror image arranged, one side of each semicircular positioning clamping plate is fixedly connected with a quick positioning clamp, and the other side of each semicircular positioning clamping plate is further connected with a profile positioning plate;

[0024] The connecting seat is fixedly connected with the support, and the connecting seat is detachably connected with the bottom ends of the two semicircular positioning clamping plates through bolts.

[0025] Preferably, wherein the stringer positioning tool comprises:

[0026] The stringer positioning plate is fixedly connected at the bottom of the semicircular positioning clamping plate, and a sliding groove is formed in the stringer positioning plate;

[0027] A limiting screw is slidingly arranged in the sliding groove, and a screw rod of the limiting screw penetrates through the bottom end of the sliding groove, and a spring is further sleeved on the limiting screw, one end of the spring abuts against the head of the limiting screw, and the other end of the spring abuts against the bottom end of the sliding groove;

[0028] A hook plate is fixedly connected with the end of the limiting screw.

[0029] Preferably, the bearing positioning tool comprises:

[0030] A positioning arm is fixedly connected with the middle position of the hinged seat at the top end, and the bottom end of the positioning arm is integrally and protrusively provided with an arc-shaped clamping plate for abutting against one side of the upper bearing and the lower bearing;

[0031] Two clamping plates for abutting against the other side of the upper bearing and the lower bearing are integrally and protrusively provided with an adjusting rod on one side for abutting against the side end of the upper bearing and the lower bearing, and the two adjusting rods are connected with the two side ends of the arc-shaped clamping plate in a penetrating manner, respectively, and a butterfly nut is threadedly connected on each of the two adjusting rods, and the bottom end of each butterfly nut is threadedly screwed against the arc-shaped clamping plate.

[0032] Preferably, the method for positioning and installing the upper bearing and the lower bearing comprises the following steps:

[0033] Step S61, the transmission shaft is erected at the corresponding position of the partition frame, and the upper bearing and the lower bearing are sleeved and installed on the transmission shaft;

[0034] Step S62, the upper bearing and the lower bearing are moved to the installation position of the partition frame, the two side ends of the upper bearing and the lower bearing are abutted and limited by the two adjusting rods, the butterfly nuts are tightened, the two clamping plates cooperate with the arc-shaped clamping plate to position and clamp the two side faces of the upper bearing and the lower bearing, and then the fixing bolts between the upper bearing and the lower bearing are tightened;

[0035] Step S63, the upper bearing is riveted with the partition frame by using rivets with the same specifications as the original machine, after 3 rivets are riveted between the upper bearing and the partition frame, the butterfly nuts are loosened to cancel the positioning and clamping of the upper bearing and the lower bearing, and the data of the coaxiality and the edge distance of the transmission shaft are measured, if the data meet the requirements, the riveting is continued, otherwise the positioning is re-performed.

[0036] Preferably, step three further comprises:

[0037] Step S31, the upper and lower bearings on the damaged partition frame are disassembled, and if there is no damage, the damaged partition frame is continued to be used, otherwise a new one is replaced.

[0038] Preferably, the method for determining the repair tolerance of the skin comprises:

[0039] Step S71, analyze the stress condition of the tail beam, determine the skin damage area position and damage area size;

[0040] Step S72, refer to the skin aerodynamic shape point cloud data of the complete tail beam, the relative position point cloud data of the bulkhead and the stringer, and calculate the overlap amount of the new skin and the stringer.

[0041] Preferably, wherein the skin repair standard comprises:

[0042] After the skin is replaced, check if there is a scratch on the surface, if there is a scratch and the depth does not exceed 0.3mm, polish it smooth with fine sandpaper, if there is a scratch and the depth exceeds 0.3mm, it needs to be repaired;

[0043] The skin overlap should be fitted, and the gap at the overlap is not more than 0.2mm, otherwise add a pad to eliminate it;

[0044] The rivet head height of the riveted skin is L=(0.3-0.7)Dmm;

[0045] The rivet head diameter d=(1.3-1.7)Dmm;

[0046] Wherein D is the diameter of the rivet, and the rivet should have no mechanical damage.

[0047] The present application at least includes the following beneficial effects:

[0048] The present application realizes the repair of severely damaged tail beams, meets the technical needs of severely damaged tail beam repair, and thus guarantees the training needs of helicopter equipment; the special jig supports the damaged tail beam, and connects the special jig and the bulkhead at both ends of the tail beam through bolts, further limits the activity position of the damaged tail beam, so as to realize the support and positioning of the damaged tail beam; the bulkhead positioning tool limits the activity position of the bulkhead, which can effectively prevent the bulkhead from deflecting, so as to realize the positioning of the bulkhead; the stringer positioning tool hooks the stringer to limit the stringer, so as to realize the positioning of the stringer; the bearing positioning tool positions the upper bearing and the lower bearing, guarantees the coaxiality of the plurality of upper and lower bearings, and guarantees that the edge distance between the upper and lower bearings and the transmission shaft can meet the standard, which has the advantages of guaranteeing the repair effect and guaranteeing the positioning accuracy.

[0049] Other advantages, objects, and features of the present application will be apparent to those skilled in the art from the following description, and will be understood by those skilled in the art through practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0050] Figure 1 The special jig structure of the present application is shown in the figure.

[0051] Figure 2 The bulkhead positioning tool connection diagram of the present application is shown in the figure.

[0052] Figure 3 Connection diagram of the quick positioning fixture of the present application.

[0053] Figure 4 Connection diagram of the profile positioning plate of the present application.

[0054] Figure 5 Connection diagram of the stringer positioning tool of the present application.

[0055] Figure 6 Connection diagram of the present application.

[0056] Figure 7 Connection diagram of the bearing positioning tool of the present application.

[0057] Figure 8 Connection diagram of the positioning arm of the present application.

[0058] Figure 9 Connection diagram of the clamping plate of the present application. DETAILED DESCRIPTION

[0059] The present application will be further described below in conjunction with the accompanying drawings, so that those skilled in the art can implement the present application according to the description and drawings.

[0060] It should be understood that the terms such as "have", "contain" and "include" used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0061] It should be noted that in the description of the present application, the orientation or positional relationship indicated by the terms is based on the orientation or positional relationship shown in the drawings, and is only for the purpose of facilitating the description of the present application and simplifying the description, and does not indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0062] In the description of the present application, unless otherwise explicitly specified and limited, the terms "mount", "provided with", "sleeved / connected", "connected" and the like should be understood broadly, for example, "connected" can be fixedly connected, can be detachably connected, or integrally connected, can be mechanically connected, can be electrically connected, can be directly connected, can be indirectly connected through an intermediate medium, can be internal communication of two elements, and those skilled in the art can understand the specific meaning of the above terms in the present application according to the specific circumstances.

[0063] In addition, in the present application, unless otherwise explicitly specified and limited, the first feature is "on" or "under" the second feature can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature "above", "over" and "on" the second feature can be that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature. The first feature "below", "under" and "under" the second feature can be that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is horizontally lower than the second feature.

[0064] Embodiment:

[0065] A helicopter tail beam structure serious damage repair method, comprising the following steps:

[0066] Step one, step S11, using three-dimensional scanning equipment, collecting the skin aerodynamic appearance point cloud data of the complete tail beam of multiple helicopters of the same type and same batch, the relative position point cloud data of the bulkhead and the stringer, and the appearance point cloud data and assembly position point cloud data of the bearing;

[0067] Step S12, analyzing and optimizing the skin aerodynamic appearance point cloud data, and the appearance point cloud data and assembly position point cloud data of the bearing, to determine the technical parameters of the complete tail beam;

[0068] And the tail beam three-dimensional model is established reversely through CATIA software;

[0069] Step two, according to the tail beam three-dimensional model and the damage condition of the damaged tail beam 5, a special jig 1 is developed, a replacement bulkhead 6 is made, and a plurality of bulkhead positioning tools 2, a plurality of stringer positioning tools 3 and a plurality of bearing positioning tools 4 are arranged in the special jig 1;

[0070] Replacement bulkhead 6 manufacturing method:

[0071] According to the bulkhead shape data, a bulkhead forming die is made; through physical and chemical analysis, a domestic aluminum plate of corresponding brand and specification is selected, and the replacement bulkhead is formed through an air bag forming machine. Then, the replacement bulkhead 6 is subjected to heat treatment (solid solution treatment + artificial aging), the shape of the replacement bulkhead 6 is trimmed according to the bulkhead shape data, and the replacement bulkhead 6 is then subjected to surface paint (brand H06-27). The skin and stringer are prepared and painted H06-27 (brand H06-27).

[0072] The special jig 1 comprises:

[0073] The bracket 11 is provided with a bulkhead positioning plate 12 on both sides for connecting with the bulkheads at both ends of the tail beam;

[0074] A plurality of tail beam positioning plates 13 are arranged symmetrically in the support 11 to support and position the intact part of the damaged tail beam 5.

[0075] Working principle: when repairing the damaged tail beam 5, the intact part of the damaged tail beam 5 is clamped with the plurality of tail beam positioning plates 13, the damaged tail beam 5 is supported by the plurality of tail beam positioning plates 13, and the two spacer positioning plates 12 are connected with the end spacers of the damaged tail beam 5 by bolts, further limiting the movement position of the damaged tail beam 5, thereby achieving the support and positioning of the damaged tail beam 5, which has the advantages of ensuring stable connection and facilitating repair.

[0076] The spacer positioning tool 2 comprises:

[0077] The hinged seat 21 is fixedly connected with the support 11;

[0078] The two semicircular positioning plates 22 are hingedly connected with the hinged seat 21, and the two semicircular positioning plates 22 are mirror image arranged, one side of each semicircular positioning plate 22 is fixedly connected with a quick positioning clamp 24, and the other side of each semicircular positioning plate is further connected with a profile positioning plate 25;

[0079] The connecting seat 23 is fixedly connected with the support 11, and the connecting seat 23 is detachably connected with the bottom end of the two semicircular positioning plates 22 by bolts.

[0080] Working principle: when repairing the damaged tail beam 5, the spacer 6 is installed, the semicircular positioning plate 22 corresponding to the damaged part of the damaged tail beam 5 is rotated, so that the semicircular positioning plate 22 abuts against the outer wall of the spacer 6, then the bottom end of the semicircular positioning plate 22 is connected with the connecting seat 23 by bolts, so as to limit the movement position of the semicircular positioning plate 22, and the spacer 6 is clamped by the quick positioning clamp 24 to limit the movement position of the spacer 6, and the profile positioning plate 25 limits the movement position of one end face of the spacer 6, which cooperates with the clamping of the quick positioning clamp 24 to effectively prevent the spacer 6 from deflecting, thereby achieving the positioning of the spacer 6, which has the advantages of facilitating regulation and control and ensuring positioning effect.

[0081] The stringer positioning tool 3 comprises:

[0082] The stringer positioning plate 31 is fixedly connected at the bottom of the semicircular positioning plate 22, and a sliding groove is formed in the stringer positioning plate 31;

[0083] A limiting screw 32 is slidingly arranged in the sliding groove, and the screw rod of the limiting screw 32 penetrates the bottom end of the sliding groove, and a spring is further sleeved on the limiting screw 32, one end of the spring abuts against the head of the limiting screw, and the other end of the spring abuts against the bottom end of the sliding groove;

[0084] A hook plate 33 is fixedly connected with the end of the limiting screw 32.

[0085] Working principle: when the stringer 7 is positioned, the stringer positioning plate 31 is fixed on the corresponding position of the semicircular positioning clamp plate 22, the hook plate 33 is pulled to pull out the limiting screw 32 from the sliding groove, the hook plate 33 is pulled to the corresponding position of the stringer 7, so that the spring is contracted, then the hook plate 33 is loosened to drive the limiting screw 32 to reset by the elasticity of the spring, so that the limiting screw 32 applies a pulling force to the hook plate 33, so that the hook plate 33 hooks the stringer 7, and the stringer 7 is limited, so as to realize the positioning of the stringer 7, which has the advantages of guaranteeing the positioning effect and guaranteeing the connection strength.

[0086] The bearing positioning tool 4 comprises:

[0087] A positioning arm 41 is fixedly connected with the middle position of the hinge seat 21 at the top end, and the bottom end of the positioning arm 41 is integrally formed and protrudingly provided with an arc-shaped clamp plate 42 for abutting against one side of the upper bearing 61 and the lower bearing 62;

[0088] Two clamp plates 43 for abutting against the other side of the upper bearing 61 and the lower bearing 62 are integrally formed and protrudingly provided with an adjusting rod 44 for abutting against the side end of the upper bearing and the lower bearing on one side, and the two adjusting rods 44 are respectively connected with the two side ends of the arc-shaped clamp plate 42 in penetration, and the butterfly nut 45 is respectively threadedly connected on the two adjusting rods 44, and the bottom end of the butterfly nut 45 abuts against the arc-shaped clamp plate 42 through screwing.

[0089] Working principle: when positioning the upper bearing bush 61 and the lower bearing bush 62, the intermediate position of the positioning arm 41 and the hinged seat 21 is fixedly connected, so that the position of the arc-shaped clamping plate 42 is fixed, and after the upper bearing bush 61 and the lower bearing bush 62 are connected, the arc-shaped clamping plate 42 is abutted against one side of the upper bearing bush 61 and the lower bearing bush 62, the two adjusting rods 44 are abutted against and limited on the two side ends of the upper bearing bush 61 and the lower bearing bush 62, the wing nuts 45 are tightened, the two clamping plates 43 are abutted against and limited on the other side of the upper bearing bush 61 and the lower bearing bush 62, so that the upper bearing bush 61 and the lower bearing bush 62 are limited in the front, back, left and right directions, and then the upper bearing bush 61 is riveted with the mounting position on the bulkhead, so as to guarantee the positioning accuracy of the installation of the upper bearing bush 61 and the lower bearing bush 62, guarantee the coaxiality of the plurality of upper bearing bushes 61 and lower bearing bushes 62, and guarantee that the edge distance between the upper and lower bearing bushes and the transmission shaft can meet the standard, which has the advantages of guaranteeing the positioning accuracy and guaranteeing the installation effect.

[0090] Step three, fix the damaged tail beam 5 on the special jig 1 by bolts, cut the skin, bulkhead and stringer in the damaged area, and scrap; when cutting the damaged stringer, the adjacent stringers should be staggered by at least 100 mm to avoid stress concentration;

[0091] Step S31, disassemble the upper and lower bearing bushes on the damaged bulkhead, and continue to use if there is no damage, otherwise replace new parts.

[0092] Step four, install the replacement bulkhead 6 and position it with the bulkhead positioning tool 2;

[0093] Step five, install the stringer 7 and position it with the stringer positioning tool 3;

[0094] Step six, position and install the upper bearing bush 61 and the lower bearing bush 62 through the bearing bush positioning tool 4;

[0095] The method for positioning and installing the upper bearing bush 61 and the lower bearing bush 62 is as follows:

[0096] Step S61, erect the transmission shaft 8 at the corresponding position of the bulkhead, and install the upper bearing bush 61 and the lower bearing bush 62 on the transmission shaft 8;

[0097] Step S62, move the upper bearing bush 61 and the lower bearing bush 62 to the mounting position of the bulkhead, abut and limit the two side ends of the upper bearing bush 61 and the lower bearing bush 62 through the two adjusting rods 44, and tighten the wing nuts 45, position and clamp the two side surfaces of the upper bearing bush 61 and the lower bearing bush 62 through the cooperation of the two clamping plates 43 and the arc-shaped clamping plate 42, and then tighten the fixing bolts between the upper bearing bush 61 and the lower bearing bush 62;

[0098] Step S63, riveting the upper bearing bush 61 with the bulkhead by using rivets with the same specifications as the original machine, after 3 rivets are riveted between the upper bearing bush 61 and the bulkhead, the butterfly nut 45 is loosened to cancel the positioning and clamping of the upper bearing bush 61 and the lower bearing bush 62, and the coaxiality and the edge distance data of the transmission shaft 8 are measured, the coaxiality is not greater than 1.2 mm, and the edge distance between the upper bearing bush 61, the lower bearing bush 62 and the transmission shaft 8 is not less than 3 mm, if the data meet the requirements, continue to rivet, otherwise reposition.

[0099] Step seven, according to the tail beam stress analysis, the skin repair tolerance is determined, and the skin repair standard is formulated.

[0100] The method for determining the skin repair tolerance is:

[0101] Step S71, according to the tail beam stress analysis, the damage area is located on the right side of the tail beam (tension side), and the damage area is large;

[0102] Step S72, according to the skin aerodynamic shape point cloud data of the complete tail beam, the relative position point cloud data of the bulkhead and the stringer, the lap amount should meet the arrangement of three rows of rivets, and the rivet pitch is arranged according to the original machine rivet parameters.

[0103] The skin repair standard includes:

[0104] After the skin is replaced, check whether there is scratch on the surface, if there is scratch and the depth is not more than 0.3 mm, polish and smooth with fine sandpaper;

[0105] The skin lap joint is fitted, and the gap at the lap joint is not greater than 0.2 mm;

[0106] The diameter of the rivet D is 4 mm;

[0107] The rivet head height L of the riveted skin is 2 mm;

[0108] The rivet head diameter d is 6 mm, and the rivet has no mechanical damage.

[0109] Step eight, according to the skin repair tolerance and the skin repair standard, riveting the skin, and after the skin repair standard is passed, spraying H06-27 (H06-27 grade).

[0110] Although the embodiments of the present application have been disclosed as above, they are not limited to the application listed in the specification and the embodiments, and can be fully applied to various fields suitable for the present application, and other modifications can be easily realized by those skilled in the art, therefore, the present application is not limited to specific details and the figures shown and described herein, without departing from the general concept defined by the claims and the equivalent scope.

Claims

1. A method for repairing severe damage to a helicopter tail boom structure, characterized in that, Includes the following steps: Step 1: Determine all technical parameters of the complete tail beam and reverse engineer the tail beam 3D model using CATIA software. Step 2: Based on the three-dimensional digital model of the tail beam and the damage condition of the damaged tail beam, develop a special frame and manufacture replacement partitions, as well as multiple partition positioning fixtures, multiple stringer positioning fixtures and multiple bearing positioning fixtures set in the special frame. Step 3: Secure the damaged tail beam to the special frame with bolts, cut the skin, frame, and stringers of the damaged area, and scrap it; Step 4: Install and replace the partition frame, and use the partition frame positioning fixture for positioning; Step 5: Install the stringers; use stringer positioning fixtures for positioning. Step 6: Position and install the upper and lower bearings using the bearing positioning fixture; Step 7: Based on the stress analysis of the tail beam, determine the skin repair tolerance and formulate skin repair standards; Step 8: Rivet the skin according to the skin repair tolerance and skin repair standards, and paint after the skin repair is inspected and approved according to the skin repair standards.

2. The method for repairing severe damage to the helicopter tail boom structure according to claim 1, characterized in that, The method for determining all technical parameters of the complete tail beam is as follows: Step S11: Using a 3D scanning device, collect point cloud data of the aerodynamic shape of the skin of the complete tail boom of multiple helicopters of the same model and batch, point cloud data of the relative positions of the bulkhead and stringers, and point cloud data of the shape and assembly position of the bearing bush. Step S12: Analyze and optimize the aerodynamic shape point cloud data of the skin, as well as the shape point cloud data and assembly position point cloud data of the bearing bush, to determine the various technical parameters of the complete tail beam.

3. The method for repairing severe damage to the helicopter tail boom structure according to claim 1, characterized in that, The special-purpose frame includes: The bracket has frame positioning plates on both sides for connecting with the frame at both ends of the tail beam; Multiple tail beam positioning plates are symmetrically arranged within the bracket for supporting and positioning the intact portion of the damaged tail beam.

4. The method for repairing severe damage to the helicopter tail boom structure according to claim 3, characterized in that, The frame positioning fixture includes: A hinged base, which is fixedly connected to the bracket; Two semi-circular arc positioning plates are hinged at their top ends to the hinge seat, and the two semi-circular arc positioning plates are mirror images of each other. A quick positioning fixture is fixedly connected to one side of each semi-circular arc positioning plate, and a profile positioning plate is also connected to the other side of each semi-circular arc positioning plate. The connecting seat is fixedly connected to the bracket, and the connecting seat is detachably connected to the bottom ends of the two semi-circular positioning plates by bolts.

5. The method for repairing severe damage to the helicopter tail boom structure according to claim 4, characterized in that, The stringer positioning fixture includes: A stringer positioning plate, the bottom of which is fixedly connected to the semi-circular arc positioning plate, and the stringer positioning plate is provided with a sliding groove; A limiting screw is slidably disposed in the slide groove, and the screw of the limiting screw is connected to the bottom end of the slide groove. A spring is also sleeved on the limiting screw, one end of the spring abuts against the head of the limiting screw, and the other end of the spring abuts against the bottom end of the slide groove. The hook plate is fixedly connected to the end of the limiting screw.

6. The method for repairing severe damage to the helicopter tail boom structure according to claim 4, characterized in that, The bearing positioning fixture includes: The positioning arm has its top end fixedly connected to the middle position of the hinge seat, and the bottom end of the positioning arm is integrally formed with an arc-shaped clamping plate for abutting against one side of the upper bearing and the lower bearing. Two clamping plates are used to abut against the other side of the upper and lower bearing bushes. Each of them has an integrally formed adjusting rod protruding on one side for abutting against the side ends of the upper and lower bearing bushes. The two adjusting rods are respectively connected to the two ends of the arc-shaped clamping plate. The two adjusting rods are also threaded with wing nuts. The bottom end of each wing nut abuts against the arc-shaped clamping plate by screwing the threads.

7. The method for repairing severe damage to the helicopter tail boom structure according to claim 6, characterized in that, The method for positioning and installing the upper and lower bearing shells is as follows: Step S61: Place the drive shaft in the corresponding position of the partition frame, and install the upper and lower bearing shells on the drive shaft; Step S62: Move the upper and lower bearing shells to the installation position of the partition frame, use two adjusting rods to abut and limit the two ends of the upper and lower bearing shells, tighten the wing nuts, use two clamping plates and arc clamping plates to position and clamp the two sides of the upper and lower bearing shells, and then tighten the fixing bolts between the upper and lower bearing shells. Step S63: Use rivets of the same specifications as the original machine to rivet the upper bearing shell to the partition frame. After riveting 3 rivets between the upper bearing shell and the partition frame, loosen the wing nut to remove the positioning clamp on the upper and lower bearing shells, and measure the coaxiality and edge distance of the drive shaft. If the data meets the requirements, continue riveting; otherwise, reposition.

8. The method for repairing severe damage to the helicopter tail boom structure according to claim 1, characterized in that, Step three also includes: Step S31: Disassemble the upper and lower bearing shells on the damaged partition frame. If there is no damage, continue to use it; otherwise, replace with new parts.

9. The method for repairing severe damage to the tail boom structure of a helicopter according to claim 2, characterized in that, The method for determining the tolerance of skin repair is as follows: Step S71: Analyze the stress on the tail beam to determine the location and area of ​​the skin damage area; Step S72: Refer to the point cloud data of the aerodynamic shape of the complete tail beam skin, the point cloud data of the relative positions of the frame and stringers, and calculate the overlap of the new skin and stringers.

10. The method for repairing severe damage to the helicopter tail boom structure according to claim 1, characterized in that, Skin repair standards include: After the skin is replaced, check the surface for scratches. If there are scratches and the depth does not exceed 0.3 mm, polish them smooth with fine sandpaper. If there are scratches and the depth exceeds 0.3 mm, they need to be reinforced and repaired. The skin overlaps should fit snugly, with an allowable gap of no more than 0.2 mm; otherwise, a shim should be added. The rivet head height L of the riveted skin is (0.3~0.7)D mm; The diameter of the rivet head is d = (1.3~1.7)D mm; Where D is the rivet diameter, and the rivet should be free from mechanical damage.

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