A high-mounted ducted tail structure and its forming method

Abstract

The present invention belongs to the technical field of helicopter structural design, and in particular relates to a high-mounted ducted tail structure and an assembly method thereof, comprising: a ducted adhesive assembly, an upper fairing, a rear fairing, and a tail reducer connecting pipe; the upper fairing and the rear fairing are bolted to the ducted adhesive assembly, the upper fairing and the rear fairing are assembled with the ducted adhesive assembly in an overlapping manner, and the ducted adhesive assembly is assembled and connected to the tail reducer connecting pipe. In addition to meeting basic performance requirements such as fixing the tail rotor and balancing the rotor anti-torque, it also ensures airworthiness lightning protection requirements, structural space design requirements, and reduces structural complexity, reduces structural weight, and reduces manufacturing costs as much as possible.

Description

Technical Field

[0001] The present invention belongs to the technical field of helicopter structure design, and in particular relates to a high-mounted ducted tail structure and a forming method thereof. Background Art

[0002] The tail structure of a helicopter mainly includes a conventional tail rotor and a ducted tail rotor. The main function of the tail rotor is to balance the anti-torque generated by the rotor. The ducted tail rotor is a cylindrical duct made at the tail, with tail rotor blades and tail rotor hub installed inside the duct. Compared with the conventional tail rotor layout, the ducted tail rotor has the advantages of good safety and less risk of injury accidents, low noise, small radar reflection area, which is conducive to stealth, and low power consumption of the ducted tail rotor during forward flight.

[0003] Based on the above advantages, a new type of civil helicopter design is now planning to adopt a ducted tail structure. In addition to meeting the conventional functions of fixing the tail rotor and balancing the rotor anti-torque, the ducted tail should also meet the lightning protection requirements of the airworthiness regulations, meet the design space requirements of the rear door of the model, improve the efficiency of the tail structure, reduce the structural weight as much as possible, and reduce the manufacturing difficulty and cost.

[0004] The existing ducted tail structure in China is heavy, has complex parts and structural layout, and is difficult to form, and can no longer meet the requirements of modern helicopter use. Summary of the Invention

[0005] The technical problem solved by the present invention is: Based on the technical requirements of the newly developed model design, a high-mounted ducted tail structure and its assembly method are designed. In addition to meeting the basic performance requirements such as fixing the tail rotor and balancing the rotor anti-torque, the airworthiness lightning protection requirements and structural space design requirements are guaranteed, and the structural complexity, structural weight and manufacturing costs are reduced as much as possible.

[0006] The technical solution of the present invention:

[0007] Firstly,

[0008] A high-mounted ducted tail structure, comprising: a ducted adhesive assembly 3, an upper fairing 4, a rear fairing 5, and a tail reducer connecting pipe 6;

[0009] The upper fairing 4 and the rear fairing 5 are respectively connected to the duct glue assembly 3, and the duct glue assembly 3 is connected to the tail reducer connecting pipe 6.

[0010] Furthermore, the duct adhesive assembly 3 includes:

[0011] Internal dimensional parts: duct front beam 7, vertical tail upper end rib 8, duct middle rib 9, duct oblique rib 10, duct rear rib 11, upper casing rib 12, lower casing rib 13, casing rib reinforcement corner box 14, casing rib reinforcement 15, tail reducer upper support rib 16, tail reducer lower support rib 17, vertical tail trailing edge strip 18;

[0012] External aerodynamic parts: duct inner ring 19, duct left skin 20, duct right skin 21, duct lower skin 22, duct skin cover 1 23, duct skin cover 24.

[0013] Furthermore, the upper fairing 4 and the rear fairing 5 are both fiber honeycomb sandwich structures; they serve as aerodynamic fairing parts and provide installation platforms for avionics equipment.

[0014] Furthermore, the tail reducer connecting pipe 6 is used to fix the tail reducer and tail rotor blades that balance the rotor anti-torque into the high-mounted ducted tail structure, and the tail reducer connecting pipe 6 is a composite material laminated structure.

[0015] Secondly,

[0016] A method for forming a high-mounted ducted tail structure, the method being used to manufacture the high-mounted ducted tail structure described in the first aspect, the method comprising:

[0017] S1, put into the furnace for curing to complete the assembly of the duct bonding components;

[0018] S2, after the secondary bonding and curing of the duct bonding assembly 3, the tail reducer connecting pipe 6 and the duct bonding assembly 3 are installed;

[0019] S3. After the duct bonding assembly 3 and the tail reducer connecting pipe 6 are assembled, the duct skin cover 1 23 and the duct skin cover 2 24 are installed. Each cover is connected to the self-locking nut 25 in the skin with a large flat head screw 26.

[0020] S4, assemble and connect the ducted vertical tail and the tail boom;

[0021] S5, after the assembly and riveting of the ducted vertical tail and the tail boom are completed, the screw assembly of the ducted upper fairing 4 and the rear fairing 5 and the ducted adhesive assembly 3 are carried out, and the structural electrical overlap is connected.

[0022] Furthermore, S1 is specifically:

[0023] All internal dimensional parts, the duct right skin 21, and the duct lower skin 22 in the duct bonding assembly 3 are bonded twice with adhesive film and then sent to an autoclave for medium-temperature curing.

[0024] The left duct skin 20 is glued and positioned for the second time, and then put into the furnace for medium temperature curing for the second time.

[0025] Furthermore, S2 is specifically:

[0026] Insert the tail reducer connecting pipe 6 into the duct bonding assembly 3 through the tail reducer installation hole 22-1 on the duct lower skin 22, and then install and secure the tail reducer connecting pipe 6 through the openings located in the duct right skin 21 and the duct lower skin 22;

[0027] The upper and lower ends of the tail reducer connecting pipe 6 are fixedly connected to the half-bearing 27 and the upper support rib 16 and lower support rib 17 of the tail reducer pipe.

[0028] Furthermore, S4 is specifically:

[0029] The duct vertical tail and the tail boom are designed as a process separation surface: the connection is non-detachable with glue rivets, and the riveting position is the flange of the duct front beam 7; the duct left skin 20, right skin 21, lower skin 22 and the tail boom fish mouth 35 and the leading edge skin 34 are connected at the duct front beam 7; the tail boom fish mouth 35 and the duct front beam 7 are riveted in double rows, and the leading edge skin 34 is riveted in single rows.

[0030] Furthermore, S5 is specifically:

[0031] Use blind rivets to rivet a circle of support plate nuts 31 on the inner side of the vertical tail upper end rib 8 and the duct rear rib 10 for subsequent fairing assembly; then use large flat head screws 32 to lap the fairing and duct adhesive assembly 3;

[0032] The fairing and the left and right duct skins are electrically bonded by using conductive glue to bond copper sheets 33, and the lightning protection composite film in the contact area between the skin and the fairing is polished until the copper mesh is exposed.

[0033] This invention is the first domestically-designed high-mounted ducted tail rotor to be used in a helicopter model. This high-mounted ducted tail structure offers: high structural efficiency, which allows for a corresponding reduction in overall duct dimensions, thereby reducing weight; a low probability of tail rotor impact, and enhanced safety; and a high tail placement, making it suitable for rear-door designs. Furthermore, it is the first domestic application of a lightning protection composite membrane for ducted tail rotor helicopters, featuring high conductivity and simple installation. The high-mounted ducted tail structure is entirely constructed from composite materials, which are lightweight and high-strength, effectively reducing weight. The high-mounted ducted tail structure features a simple and rational separation plane, an integrated ducted structure layout without redundant connections, and an optimized internal layout. All components are simple and free of complex parts, effectively reducing weight while also simplifying tooling design and manufacturing, as well as part molding, and improving production efficiency. The ducted assembly utilizes a medium-temperature, secondary adhesive curing assembly, requiring only two furnace curing cycles. Fewer furnace curing cycles significantly reduce manufacturing costs and minimize deformation accumulation during furnace curing. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic diagram of a novel helicopter configuration - a high-mounted ducted tail rotor structure - provided by an embodiment of the present invention;

[0035] Figure 2 A schematic diagram of the tail structure provided in an embodiment of the present invention;

[0036] Figure 3 A schematic diagram of the composition of a duct assembly provided in an embodiment of the present invention;

[0037] Figure 4 A schematic diagram of the duct lower skin structure provided by an embodiment of the present invention;

[0038] Figure 5 A schematic diagram of the connection of the skin cover provided in an embodiment of the present invention;

[0039] Figure 6 A schematic diagram of the installation of the connecting pipe of the tail reducer provided in an embodiment of the present invention;

[0040] Figure 7 A schematic diagram of the installation of an upper fairing provided in an embodiment of the present invention;

[0041] Figure 8 A schematic diagram of the connection between the duct and the body provided in an embodiment of the present invention;

[0042] Among them, 1-fuselage rear door, 2-high-mounted duct tail structure, 3-duct bonding assembly, 4-upper fairing, 5-rear fairing, 6-tail reducer connecting pipe, 7-duct front beam, 8-vertical tail upper end rib, 9-duct middle rib, 10-duct oblique rib, 11-duct rear rib, 12-upper casing rib, 13-lower casing rib, 14-casing rib reinforcement corner box, 15-casing rib reinforcement, 16-tail reducer upper support rib, 17-tail reducer lower support rib. , 18-vertical tail trailing edge strip, 19-duct inner ring, 20-duct left skin, 21-duct right skin, 22-duct lower skin, 23-duct skin cover one, 24-duct skin cover two, 25-self-locking nut, 26-round head screw, 27-half bearing, 28-bolt, 29-thick flat washer, 30-nut, 31-support plate nut, 32-large flat round head screw, 33-lap copper sheet, 34-leading edge skin, 35-tail boom fish mouth, 36-sunk nail. DETAILED DESCRIPTION

[0043] The technical solution of the present invention is described in detail below with reference to the accompanying drawings.

[0044] After calculation and analysis, in order to meet the requirements of the rear door 1 structural design and reduce the structural weight, the tail structure used in the present invention adopts the following Figure 1The high-mounted ducted structure layout shown in the figure has a high-mounted ducted tail structure 2 composed of a ducted adhesive assembly 3, an upper fairing 4, a rear fairing 5, and a tail reducer connecting pipe 6. The entire structure is designed with all-composite materials.

[0045] The duct glued assembly 3 is the main structure of the tail structure, mainly including:

[0046] Internal dimensional parts: duct front beam 7, vertical tail upper end rib 8, duct middle rib 9, duct oblique rib 10, duct rear rib 11, upper casing rib 12, lower casing rib 13, casing rib reinforcement corner box 14, casing rib reinforcement 15, tail reducer upper support rib 16, tail reducer lower support rib 17, vertical tail trailing edge strip 18;

[0047] The external aerodynamic shape parts are composed of a duct inner ring 19, a duct left skin 20, a duct right skin 21, a duct lower skin 22, and a duct skin cover (23, 24).

[0048] After all parts are formed, they are bonded with Redux312.5 and Redux312-L adhesive films for secondary curing at medium temperature, requiring only a second injection into the furnace to complete the overall bonding.

[0049] The upper fairing 4 and the rear fairing 5 are both KEVLAR fiber honeycomb sandwich structures; their main functions are aerodynamic fairing and providing a necessary installation platform for avionics equipment.

[0050] The tail reducer connecting pipe 6 is used to fix the tail reducer (and tail rotor blades) that balances the rotor anti-torque into the duct structure.

[0051] The tail reducer connecting pipe 6 is a composite material laminate structure and is used to fix the tail reducer. The installation method is: after the duct bonding assembly 3 is bonded and cured, the tail reducer connecting pipe 6 is positioned and installed, and the tail reducer connecting pipe 6 is inserted into the duct bonding assembly 3 through the tail reducer installation hole 22-1 on the duct lower skin 22, and then the tail reducer connecting pipe 6 is installed and fixed through the openings (23, 24, 22-2) located at the duct right skin 21 and the duct lower skin 22; the upper and lower ends of the tail reducer are fixedly connected to the half-bearing 27 and the upper support rib 16 and lower support rib 17 of the tail reducer by bolts.

[0052] The openings (22-1, 22-2) on the duct lower skin 22 are covered by the drooping tail structure that protects the duct, and no specially designed cover is required.

[0053] After the duct glue assembly 3 and the tail reducer connecting pipe 6 are assembled, the duct skin cover (23, 24) is installed, and the connection method is bolt connection.

[0054] Then the duct and the tail beam are assembled and connected, and the two are designed to be separated by a process: that is, the connection is non-detachable by glue rivets, and the riveting position is the flange of the duct front beam 7; the left, right and lower skins (20, 21, 22) of the duct are connected with the tail beam fish mouth 35 and the leading edge skin 34 at the duct front beam 7; because the lower end of the duct front beam 7 is subjected to greater force, in order to increase the connection strength, the tail beam fish mouth 35 and the duct front beam 7 are riveted in double rows, and the leading edge skin 34 is riveted in single rows.

[0055] After the assembly and riveting of the duct and tail beam are completed, the upper fairing 4 and rear fairing 5 of the duct are bolted together with the duct bonding assembly 3. The upper fairing 4 and rear fairing 5 are assembled with the duct bonding assembly in an overlapping manner.

[0056] In order to meet the relevant requirements for lightning protection in airworthiness, the high-mounted duct tail structure adopts the laying of advanced lightning protection composite membrane as the overall structure, and the structures are connected and conducted through overlapping copper sheets and the copper mesh of the lightning protection composite membrane.

[0057] The tail structure used in the present invention adopts Figure 1 The high-mounted ducted structure layout shown in the figure is that the high-mounted ducted tail structure 2 is composed of a ducted adhesive assembly 3, an upper fairing 4, a rear fairing 5, and a tail reducer connecting pipe 6 for supporting the tail reducer and tail rotor blades. The entire structure adopts a fully composite material design.

[0058] The duct bonding assembly 3 is the main structure of the tail structure, and is composed of internal dimensional parts including: duct front beam 7, vertical tail upper end rib 8, duct middle rib 9, duct oblique rib 10, duct rear rib 11, upper casing rib 12, lower casing rib 13, casing rib reinforcement corner box 14, casing rib reinforcement 15, tail reducer upper support rib 16, tail reducer lower support rib 17, vertical tail trailing edge strip 18; and external aerodynamic shape parts including: duct inner ring 19, duct left skin 20, duct right skin 21, duct lower skin 22, duct skin cover (23, 24). After the parts are formed, they are bonded with Redux312.5 and Redux312-L adhesive films for secondary bonding and medium-temperature curing, and only need to be put into the furnace twice to complete the overall bonding:

[0059] 1. All the skeleton components, the duct right skin 21, and the duct lower skin 22 in the duct bonding assembly 3 are bonded with adhesive film for a second time and then sent to an autoclave for medium-temperature curing.

[0060] 2. Carry out secondary gluing and positioning of the duct left skin 20, and put it into the furnace for medium temperature curing for the second time.

[0061] After the assembly of the duct adhesive assembly is completed after two times of curing in the furnace, the left and right duct skins (20, 21) and the duct front beam 7 are riveted using NAS1921 countersunk blind rivets to increase the connection strength and reliability.

[0062] After the duct bonding assembly 3 is cured and formed after secondary bonding, the installation process of the tail reducer connecting pipe 6 and the duct bonding assembly 3 is carried out: the tail reducer connecting pipe 6 is inserted into the interior of the duct bonding assembly 3 through the tail reducer pipe installation hole 22-1 on the duct lower skin 22, and then the tail reducer connecting pipe 6 is installed and fixed through the openings (23, 24, 22-2) located at the duct right skin 21 and the duct lower skin 22; the upper and lower ends of the tail reducer pipe are fixedly connected to the half-bearing 27 and the tail reducer pipe upper support rib 16 and the tail reducer pipe lower support rib 17 by 4 sets of Q-22201BE060012L bolts 28, 23119DG060J thick flat washers 29, and Q-22541N060 nuts 30.

[0063] After the duct bonding assembly 3 and the tail reducer connecting pipe 6 are assembled, the duct skin cover (23, 24) is installed. Each cover is connected to the 52358CCM050E self-locking nut 25 in the skin through 6 Q / 2AJ653-TK-050-S-012-X large flat round head screws 26.

[0064] After the above work is completed, the duct vertical tail and the tail beam are assembled and connected. The two are designed as a process separation surface: the connection is non-detachable by glue rivets, and the riveting position is the flange of the duct front beam 7; the left, right and lower skins (20, 21, 22) of the duct are connected with the tail beam fish mouth 35 and the leading edge skin 34 at the duct front beam 7; because the lower end of the duct front beam 7 is subjected to greater force, in order to increase the connection strength, the tail beam fish mouth 35 and the duct front beam 7 are riveted in double rows in parallel, and the leading edge skin 34 is riveted with single rows of nails; the rivets are NAS1921 series countersunk nails 36.

[0065] After the duct and tail beam are assembled and riveted, press Figure 8 The upper and rear fairings 4 and 5 of the duct are screwed together and electrically bonded to the duct adhesive assembly 3. First, a ring of GB930M4 support nuts 31 are riveted to the inside of the vertical tail upper rib 8 and the rear duct rib 10 using blind rivets for subsequent fairing assembly. The fairings are then bonded to the duct adhesive assembly 3 using Q / 2AJ653-TK-050-S-014-X large flat head screws 32. Electrical bonding is achieved between the fairings and the left and right duct skins using conductive adhesive DAD-8-3, using overlapping copper sheets 33. The lightning protection composite film in the contact area between the skin and the fairing is polished until the copper mesh is exposed. One copper sheet is used on each side, made of H62M δ0.4. The resistance is guaranteed to be no greater than 1000 μΩ, meeting the bonding requirements between structural components.

[0066] Example: Design of the ducted tail structure of the AC332 four-ton high-altitude civilian helicopter

[0067] The AC332 high-altitude civilian helicopter has high requirements in terms of weight control, flight safety, rescue and first aid. The tail structure adopts a ducted tail rotor layout. The existing domestic models have a complex ducted vertical tail structure, a large overall weight, and poor workmanship, which is far from meeting the design requirements of the new era helicopter. To ensure the smooth development of the model, a new ducted tail structure design is carried out:

[0068] (1) Adopting a high-mounted ducted tail structure: The high-mounted tail structure has many advantages, such as high efficiency, low probability of tail rotor impact, and convenience for adding rear doors to the fuselage. Correspondingly, it can reduce the overall duct size and has great advantages in controlling the structural weight.

[0069] (2) Made of all-composite materials: The main structure of the duct is designed and manufactured with composite materials. Its lightweight and high-strength properties ensure the strength and stiffness of the tail while also facilitating structural weight control.

[0070] (3) The entire surface of the duct is covered with a lightning protection surface film: In order to be suitable for flight missions in severe weather and meet airworthiness regulations, a surface lightning protection film is used for lightning protection.

[0071] (4) By learning from the advantages and disadvantages of the past ducted vertical tail manufacturing, the overall layout of the duct, the separation surface design, and the process molding were improved in many aspects, such as simplifying the number of parts, optimizing the part configuration, and optimizing the process molding method.

[0072] The tail structure design has been verified in terms of strength, airworthiness, and craftsmanship to meet various performance requirements.

Claims

1. A method for forming a high-mounted ducted tail structure, characterized in that: The method is used to manufacture a high-mounted ducted tail structure, the structure comprising: a ducted adhesive assembly (3), an upper fairing (4), a rear fairing (5), and a tail reducer connecting pipe (6); The upper fairing (4) and the rear fairing (5) are respectively connected to the duct glue assembly (3), and the duct glue assembly (3) is connected to the tail reducer connecting pipe (6); The duct glued assembly (3) comprises: Internal dimensional parts: duct front beam (7), vertical tail upper end rib (8), duct middle rib (9), duct oblique rib (10), duct rear rib (11), upper casing rib (12), lower casing rib (13), casing rib reinforcement corner box (14), casing rib reinforcement (15), tail reducer upper support rib (16), tail reducer lower support rib (17), vertical tail trailing edge strip (18); External aerodynamic parts: duct inner ring (19), duct left skin (20), duct right skin (21), duct lower skin (22), duct skin cover 1 (23), duct skin cover 2 (24); The tail reducer connecting pipe (6) is used to fix the tail reducer and tail rotor blades for balancing the rotor anti-torque into the high-mounted ducted tail structure, and the tail reducer connecting pipe (6) is a composite material laminated structure; The method comprises: S1, put into the furnace for curing to complete the assembly of the duct bonding components; S2, after the duct bonding assembly (3) is secondary bonded and solidified, the tail reducer connecting pipe (6) and the duct bonding assembly (3) are installed; S3, after the duct glue assembly (3) and the tail reducer connecting pipe (6) are assembled, the duct skin cover 1 (23) and the duct skin cover 2 (24) are installed, and each cover is connected to the self-locking nut (25) in the skin through a large flat round head screw (26); S4, assemble and connect the ducted vertical tail and the tail boom; S5, after the assembly and riveting of the ducted vertical tail and the tail beam are completed, the upper fairing (4) and the rear fairing (5) of the ducted and the ducted adhesive assembly (3) are screwed and assembled, and the structural electrical connection is conducted.

2. The method for forming a high-mounted ducted tail structure according to claim 1, characterized in that: The upper fairing (4) and the rear fairing (5) are both fiber honeycomb sandwich structures; they serve as aerodynamic fairing parts and provide an installation platform for avionics equipment.

3. The method for forming a high-mounted ducted tail structure according to claim 1, characterized in that: S1 is specifically: All internal dimensional parts, the duct right skin (21), and the duct lower skin (22) in the duct bonding assembly (3) are bonded for a second time using adhesive film and then sent to an autoclave for medium-temperature curing; The left duct skin (20) is glued and positioned for the second time, and then put into the furnace for medium temperature curing for the second time.

4. The method for forming a high-mounted ducted tail structure according to claim 3, characterized in that: S2 is specifically: Insert the tail reducer connecting pipe (6) into the interior of the duct bonding assembly (3) through the tail reducer pipe installation hole (22-1) on the duct lower skin (22), and then install and fix the tail reducer connecting pipe (6) through the openings located at the duct right skin (21) and the duct lower skin (22); The upper and lower ends of the tail reducer connecting pipe (6) are fixedly connected to the half-bearing (27) and the tail reducer pipe upper support rib (16) and the tail reducer pipe lower support rib (17).

5. The method for forming a high-mounted ducted tail structure according to claim 4, characterized in that: S4 is specifically: The duct vertical tail and the tail beam are designed as a process separation surface: the connection is non-detachable by glue rivets, and the riveting position is the flange of the duct front beam (7); the duct left skin (20), right skin (21), lower skin (22) and tail beam fish mouth (35), leading edge skin (34) are connected at the duct front beam (7); the tail beam fish mouth (35) and the duct front beam (7) are riveted in double rows, and the leading edge skin (34) is riveted in single rows.

6. The method for forming a high-mounted ducted tail structure according to claim 5, characterized in that: S5 is specifically: A circle of support plate nuts (31) are riveted on the inner side of the upper end rib (8) of the vertical tail and the rear rib (10) of the duct using blind rivets for subsequent fairing assembly; the fairing is then assembled in an overlapping manner with the duct bonding assembly (3) using large flat round head screws (32); The fairing and the left and right duct skins are electrically bonded by using conductive adhesive to bond copper sheets (33), and the lightning protection composite film in the contact area between the skin and the fairing is polished until the copper mesh is exposed.

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