A method and apparatus for testing the crashworthiness of a helicopter fuel system

Abstract

This invention relates to the field of helicopter fuel systems, specifically to a method and apparatus for crash testing of helicopter fuel systems. The apparatus includes a drop platform, a rigid base assembly, and a control system. The drop platform comprises a steel cable, a cargo hook, a sling, a cable guide, a platform frame, a guide frame, and position sensors. The rigid base assembly includes a balance beam, guide ropes, a rigid base, and eye bolts. The platform frame is used to place a test prototype flat on it. The method involves installing the helicopter fuel system crash testing apparatus, placing the test prototype flat on the drop platform, using the control system to open the cargo hook, allowing the test prototype and the drop platform to fall freely together, colliding with the rigid base, recording data, and completing one helicopter fuel system crash test. This invention reduces the number of crash tests conducted using physical components, thus lowering the cost of helicopter development.

Description

Technical Field

[0001] This invention relates to the field of helicopter fuel systems, specifically to a method and apparatus for crashworthiness testing of helicopter fuel systems. Background Technology

[0002] Based on military and civilian helicopter crashes, the main causes of injury and death on board are the impact damage and the fire caused by fuel system rupture and subsequent fuel leaks. Clearly, if a fire occurs with a large amount of spilled fuel, the survival chances of the helicopter crew are greatly reduced. Therefore, crashworthiness design of the helicopter fuel system is paramount in helicopter crashworthiness design. With the widespread use and development of finite element analysis software and computer hardware, helicopter companies primarily use simulation analysis software for fuel system crashworthiness analysis, providing a large amount of reliable and effective data for helicopter fuel system design, reducing the number of physical crash tests, and lowering helicopter development costs. However, in the later stages of helicopter development, physical crash tests are still necessary to verify the correctness of the fuel system design. However, conducting full-scale helicopter fuel system crashworthiness tests is extremely expensive; therefore:

[0003] 1. How to simplify the structure of the fuel system and its surrounding environment, and construct a reasonable, comprehensive and practical test prototype;

[0004] 2. How to comprehensively consider the potential puncture hazards around the fuel system during a helicopter crash and assess all possible sources of danger;

[0005] 3. How to accurately and reasonably determine the attitude and position of the surrounding structures of the fuel system during a helicopter crash, so that the test process is more in line with the actual situation of a helicopter crash;

[0006] 4. How to reasonably set up the test equipment to obtain the closest possible crash scenario with the fewest number of tests, thereby reducing test costs;

[0007] These issues are crucial in the crashworthiness design of helicopter fuel systems. Currently, there is little literature on crashworthiness testing of helicopter fuel systems addressing these problems, nor are there any proposed solutions. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention proposes a helicopter fuel system crashworthiness testing device, comprising:

[0009] Drop platform, rigid foundation components and control system;

[0010] The drop platform includes steel cables, hooks, slings, cable guides, platform frames, guide frames, and position sensors;

[0011] The rigid foundation assembly includes a balance beam, guide ropes, a rigid foundation, and lifting eye bolts;

[0012] The drop platform is suspended below the balance beam by steel cables. One end of the steel cable is fixedly connected to the balance beam, and the other end is fixedly connected to the cargo hook.

[0013] The platform frame is U-shaped, with front and back panels and open sides for placing the test prototype flat on it; one end of the hanging rope is hung on the cargo hook, and the other end is fixedly connected to the four fixed supports of the platform frame with four feet respectively. The hanging rope acts as a limit and closely follows the outer contour of the test prototype.

[0014] The balance beam is equipped with guide ropes on both sides. One end of the guide ropes is fixed to the end of the balance beam, and the other end is fixed to the rigid foundation component to form two slide rails. The balance beam is also connected to hoisting equipment that can lift it to a certain height.

[0015] Guide frames are installed on the exterior of the front and rear wall panels of the platform frame. Steel cable guides are installed at the four opposite corners of the guide frames on both sides to ensure that the platform frame falls freely along the guide rope without rotating or tilting.

[0016] The cargo hook is an electronic cargo hook that can be opened and closed by a control system;

[0017] The control system includes an interconnected control box and cables, the other end of which is also connected to a cargo hook.

[0018] Furthermore, the rigid foundation is a non-deformable reinforced concrete square foundation.

[0019] Furthermore, position sensors for measuring the horizontal tilt angle of the test prototype before the collision are installed at the three corners of the platform frame, and the measurement data is received by the control system.

[0020] Furthermore, the test prototype includes a fuel system, representative surrounding structures, and a puncture hazard.

[0021] The fuel system retains the fuel storage unit and corresponding fuel supply pipeline components of the helicopter model under test.

[0022] The fuel storage unit includes a left fuel tank and a right fuel tank arranged symmetrically. The upper part of the left and right fuel tanks retains the fuel tank cap, and the interior retains a fuel quantity sensor, a low fuel switch, a fuel sump drain pipe and a filter screen. The size and structure of the fuel quantity sensor and the low fuel switch are the same as those of the actual helicopter model under test.

[0023] The fuel supply pipeline components retain the vent pipes connecting the upper parts of the left and right fuel tanks to the two fuel tanks. The vent pipes are fixed to the helicopter structure, and the lowest end of the vent pipes is trimmed to be flush with the bottom of the test prototype.

[0024] It also retains the connecting oil pipe in the middle for mutual fuel transfer, the fuel supply line in the lower part connecting the left and right fuel tanks, and the fuel cut-off valve located in the middle of the fuel supply line;

[0025] The representative surrounding structures include the rear section of the nacelle and the sealed cavities installed on the left and right sides of the top of the fuselage tower for encapsulating the left and right fuel tank bladders.

[0026] The sealed cavity is surrounded by external sealing representative structures, including the fuel tank bracket, the front fuselage skin, the fairing ring, and the firewall.

[0027] The firewall structure is consistent with the actual firewall components of the helicopter under test.

[0028] The forward fuselage skin is fixed to the rear section of the nacelle, the upper part of the fairing ring is connected to the forward fuselage skin, and the lower part is fixed to the fuselage tower;

[0029] The fuel tank bracket is also fixedly connected to the front fuselage skin, fairing ring, and back firewall;

[0030] The rear section of the cabin is a shell section cut from the cabin of the helicopter model under test. It is located in front of the firewall and is fixedly connected to the fuselage tower. The bottom is trimmed to be flush with the bottom of the fuselage tower.

[0031] The puncture hazards include the fuselage tower, control system, engine gearbox, main rotor gearbox, main rotor mast, driven pulley, and automatic swashplate assembly;

[0032] The fuselage tower, located below the fuel system and its external sealing representative structure, is a truss structure;

[0033] The control system includes a collective pitch control system and a cyclic pitch control system;

[0034] The collective pitch control system includes a V-shaped rocker arm, a first lever, a second lever, and a triangular rocker arm.

[0035] One end of the herringbone rocker arm is fixed to the automatic tilting plate assembly, and the other end is fixedly connected to the first pull rod; the other end of the first pull rod is fixed to the triangular rocker arm; the other end of the triangular rocker arm is fixedly connected to the second pull rod; the free end of the second pull rod is fixed to the fuselage tower.

[0036] The cyclic pitch control system includes a symmetrically arranged cyclic pitch control system for the driver and co-pilot, comprising lever three, a T-shaped rocker arm, and lever four.

[0037] One end of the tie rod three is fixedly connected to the automatic tilting plate assembly, and the other end is connected to the T-shaped rocker arm by bolts. The other end of the T-shaped rocker arm is connected to the tie rod four by bolts. The free end of the tie rod four is fixed to the fuselage tower.

[0038] The engine gearbox is located in the installation space between the left and right fuel tanks and is fixedly connected to the fuselage tower.

[0039] The main rotor gearbox, main rotor mast, driven pulley, and automatic swashplate assembly are all located in the installation space between the left and right fuel tanks. The driven pulley is installed at the rear end of the main rotor gearbox and fixed to the fuselage tower. The main rotor mast is installed in the middle of the main rotor gearbox and tilts upward. The automatic swashplate assembly is installed at the lower part of the main rotor gearbox. The size and weight of the main rotor gearbox are consistent with the actual gearbox of the helicopter model under test and it is fixed to the fuselage tower.

[0040] A forward lubrication line is retained at the lower front end of the main rotor gearbox.

[0041] Furthermore, the length of the rear section of the cabin is 0.4 meters.

[0042] Furthermore, the shock absorber on the T-shaped rocker arm is ignored in the cyclic pitch control system, and a steel pipe is used instead of the fine-tuning motor.

[0043] This invention also discloses a method for crashworthiness testing of a helicopter fuel system, comprising the following steps:

[0044] Step 1 Installation

[0045] Using the aforementioned helicopter fuel system crashworthiness test device, the test prototype was placed flat on the drop platform, with the left and right sides of the test prototype aligned with the longitudinal plane.

[0046] The drop platform is placed at the center of the rigid base assembly, with the two central axes at 45 degrees to each other;

[0047] The balance beam is slowly lifted using hoisting equipment. Once the drop platform is off the ground, the cable guide is adjusted so that the two guide ropes are centered on the cable guide and parallel to each other. At the same time, the entire drop platform is adjusted to a horizontal position based on the data received from the position sensor by the control system.

[0048] Continue lifting the drop platform until it reaches the required height for the test, with the guide rope set to be just taut at this point;

[0049] Step 2 Experiment

[0050] The control system opens the cargo hook, allowing the test prototype to fall freely together with the drop platform, completing the collision on a rigid base, while a camera records the collision process.

[0051] Step 3 Check

[0052] Check the measurement data from the position sensor to confirm that the pitch and roll angles of the test prototype relative to the drop platform do not exceed the specified values. Inspect the test prototype, record the data, and complete a helicopter fuel system crashworthiness test.

[0053] Furthermore, step 1 also includes the following settings for the experimental prototype:

[0054] (1) Dyeing water was used instead of fuel in the test. The left and right fuel tanks of the test prototype were filled with dyeing water at 80% volume.

[0055] (2) If necessary, counterweights can be added to the test device to balance the center of gravity of the test device and make it fall horizontally.

[0056] Furthermore, the experimental prototype was configured such that: the inlet and outlet of the pipeline connection were blocked, the fuel tank cap of the fuel system was sealed and closed, but the vent pipe remained open, and the bottom of the vent pipe was wrapped with a plastic bag to collect any liquid that might spill out; the fuel cut-off valve was closed, and the oil pan drain pipe was closed.

[0057] At the same time, the A-frame rocker arm and lever are positioned as close as possible to the fuel tank bladder to simulate the actual operation of a pilot pulling up the helicopter with all their might when it crashes, while the cyclic torque converter is placed approximately in neutral.

[0058] Furthermore, the camera includes a regular camera, a high-speed camera, and a GoPro camera;

[0059] High-speed cameras and GoPro cameras were used to capture videos of the experimental device impacting the rigid foundation.

[0060] Ordinary cameras were used to photograph the entire crashworthiness test process.

[0061] This invention simplifies the fuel system and its surrounding structure, proposing a representative structure that realistically reflects the fuel system during a helicopter crash. It fully considers the environment around the fuel system, assesses all potential hazards, incorporates these hazards into the test prototype, and determines their attitude and position during the crash, accurately simulating the helicopter crash scenario. This provides a representative alternative for full-size helicopters used in fuel system crashworthiness testing. The invention also provides a complete crashworthiness test apparatus, clearly defining the test process and methods. The test apparatus is simple, easy to assemble and disassemble, has low testing costs, good maneuverability, and a reliable and effective test method. Tests have demonstrated that the test method and apparatus provided by this patent are reliable and accurate, realistically simulating the impact and hazards experienced by the fuel system during a helicopter crash. It is highly suitable for helicopter fuel system crashworthiness testing and has significant practical application value. Attached Figure Description

[0062] Figure 1 This is a schematic diagram of the helicopter fuel system crashworthiness test device in an embodiment of the present invention.

[0063] Figure 2 This is a schematic diagram of the drop platform in an embodiment of the present invention.

[0064] Figure 3 for Figure 1 A top view of the helicopter fuel system crashworthiness test setup.

[0065] Figure 4 This is a schematic diagram of the rigid foundation component in an embodiment of the present invention.

[0066] Figure 5 This is a schematic diagram of the control system in an embodiment of the present invention.

[0067] Figure 6 This is a schematic diagram of the installation structure of the test prototype in an embodiment of the present invention.

[0068] Figure 7 This is a schematic diagram showing the positional relationship between the drop platform and the rigid foundation component in an embodiment of the present invention.

[0069] Figure 8 This is a schematic diagram of the fuel system in an embodiment of the present invention.

[0070] Figure 9 This is a schematic diagram of a representative structure of a fuel system in an embodiment of the present invention.

[0071] Figure 10 This is a schematic diagram of the installation structure of the operating system in an embodiment of the present invention.

[0072] Figure 11 This is a schematic diagram of the installation structure of the gearbox and other accessories in an embodiment of the present invention.

[0073] Figure 12 This is a schematic diagram of the camera arrangement in an embodiment of the present invention.

[0074] The reference numerals in the accompanying drawings include:

[0075] 100. Prototype; 200. Drop platform; 300. Rigid foundation components; 400. Control system;

[0076] 201. Steel cable, 202. Cargo hook, 203. Lifting rope, 204. Steel cable guide, 205. Platform frame, 206. Guide frame, 207. Position sensor

[0077] 301. Balance beam, 302. Guide rope, 303. Rigid foundation, 304. Eye bolt, 401. Control box, 402. Cable;

[0078] 111. Left fuel tank bladder, 112. Vent line, 113. Right fuel tank bladder, 114. Fuel supply line, 115. Fuel shut-off valve, 116. Connecting fuel line, 117. Clamp;

[0079] 121. Aft section of the nacelle; 122. Fuselage tower; 123. Fairing ring; 124. Perforated foam; 125. Fuel tank bracket; 126. Forward fuselage skin; 127. Firewall.

[0080] 131. A-frame rocker arm; 132. Tie rod one; 133. Tie rod two; 134. Triangular rocker arm; 135. Fixed support one; 141. Tie rod four; 142. T-shaped rocker arm; 143. Tie rod three; 144. Fixed support two;

[0081] 151. Driven pulley; 152. Main rotor gearbox; 153. Main rotor mast; 154. Automatic swashplate assembly; 155. Engine gearbox; 156. Top support; 157. Lateral support; 158. Tripod.

[0082] 001. High-speed camera; 002. Ordinary camera; 003. GoPro-specific camera; 004. GoPro-specific camera; Detailed Implementation

[0083] The helicopter fuel system crashworthiness testing device in this embodiment, such as Figures 1-5 As shown, it mainly consists of a drop platform 200, a rigid base component 300, and a control system 400. Figure 2 and Figure 3 As shown, the drop platform 200 mainly consists of steel cables 201, hooks 202, suspending ropes 203, cable guides 204, platform frames 205, guide frames 206, and position sensors 207. Figure 4 As shown, the rigid foundation assembly 300 mainly consists of components such as a balance beam 301, a guide rope 302, a rigid foundation 303, and lifting eye bolts 304. Figure 1 , Figure 2 and Figure 3 As shown, the drop platform 200 is suspended below the balance beam 301 by steel cable 201 and bolt assembly. One end of the steel cable 201 is connected to the double lugs of the balance beam 301 by bolt assembly, and the other end is connected to the hook 202. Figure 1 and Figure 3As shown, the drop test platform 200 is used to place the test prototype 100 flat on it. One end of the suspension rope 203 in the drop test platform 200 is attached to the hook 202, and the other end has four feet connected to the four fixed supports of the platform frame 205. The suspension rope 203 is close to the outer contour of the test prototype 100, serving only a limiting function to ensure that the test prototype 100 does not move out of the predetermined position during the descent. Figure 1 and Figure 4 As shown, guide ropes 302 are attached to both sides of the balance beam 301. One end of the guide rope 302 is fixed to the double lugs of the balance beam 301 by a bolt assembly, and the other end is fixed to the rigid foundation assembly 300 by a lifting eye bolt 304. The balance beam 301 can be connected to a crane or tower crane via the three single lugs at the top to lift the test device to a certain height. The guide ropes 302 on both sides form two slide rails, allowing the drop platform 200 to fall freely without rotation or tilting, impacting the rigid foundation 303 at the correct angle without interfering with the test process. The rigid foundation 303 is a non-deformable reinforced concrete square foundation.

[0084] like Figure 2 As shown, the platform frame 205 is U-shaped, with triangular panels at the front and back, and open on both sides. The platform frame 205 is entirely made of rigid wood. Guide frames 206 are provided on both sides of the platform frame 205, and the guide frames 206 are arranged according to… Figure 2 The design ensures that the failure of the guide frame 206 does not interfere with the test process when the test prototype 100 collides with the rigid base component 300. Each of the four diagonal points of the guide frames 206 on both sides is equipped with a dedicated steel cable guide 204. By adjusting the position and angle of the steel cable guide 204, the guide rope 302 ensures that the drop platform 200 can fall freely without rotation or tilting, impacting the rigid base 303 at the correct angle without interfering with the test process. The hook 202 is an electronic hook, which can be opened and closed via the control system 400. Figure 3 As shown, position sensors 207 are installed on the three corners of the platform frame 205 to measure the horizontal tilt angle of the test prototype before the collision. The measurement data is received by the control system 400.

[0085] like Figure 1 and Figure 5 As shown, the control system 400 mainly consists of a control box 401 and a cable 402. One end of the cable 402 is connected to the hook, and the other end is connected to the control box 401. The control box 401 can control the opening and closing of the hook and receive measurement data from the position sensor 207.

[0086] The crashworthiness test method for the helicopter fuel system in this embodiment is as follows:

[0087] 1) Installation

[0088] like Figure 3 and Figure 6 As shown, the test prototype 100 is placed flat on the drop platform 200, with a distance of ≥100mm from the front and rear triangular wall panels of the drop platform 200; the left and right sides of the test prototype 100 are placed in the center relative to the longitudinal plane, and the center of gravity requirement is met.

[0089] like Figure 7 As shown, the drop platform 200 is placed at the center of the rigid base component 300, with the two central axes at 45 degrees to each other.

[0090] like Figure 1 As shown, two guide ropes 302 pass through the steel cable guides 204 on the drop platform 200 and are connected to the double lugs on both sides of the balance beam 301. One end of the suspension rope 203 has four feet connected to the four fixed supports of the platform frame 205, and the other end is hung on the hook 202. The suspension rope 203 is adjusted to be close to the outer contour of the test prototype 100, and the hook 202 is connected to the double lugs of the balance beam 301 through the steel cable 201.

[0091] The balance beam 301 is slowly lifted using a crane or tower crane. The lifting process stops as soon as the drop platform 200 leaves the ground. The cable guide 204 is adjusted so that the two guide ropes 302 are centered and parallel to each other. Simultaneously, based on data received from the position sensor 207 by the control system 400, the entire drop platform 200 is adjusted to a horizontal position. The drop platform 200 is then lifted further until the required test height of 50 feet (as specified in airworthiness regulations), specifically the vertical distance from the bottom of the fuel tank to the upper surface of the rigid foundation 303. At this point, the guide ropes 302 are just taut. Throughout the entire process, the relative position of the test prototype 100 and the drop platform 200 must not be changed. Finally, the pre-positioned cameras are adjusted and activated as needed, the site is cleared, and a warning line is established.

[0092] 2) Test setup

[0093] ① Tests for simplifying the design of fuel systems and their surrounding structures;

[0094] Considering cost and feasibility, using a full-size aircraft for helicopter fuel system crashworthiness testing is highly unreasonable. Therefore, it is necessary to simplify the fuel system and its surrounding structure, encapsulating the fuel system in a representative structure to construct a reasonable, comprehensive, and realistic test prototype to replace the full-size aircraft for testing. This is also one of the important methods in this experiment.

[0095] (1) Fuel System

[0096] Helicopter fuel systems are quite complex. Considering fuel leakage in the event of a crash, the main components retained are the fuel storage unit and some fuel supply lines, such as... Figure 8 As shown: The left fuel tank bladder 111 and the right fuel tank bladder 113 are symmetrically arranged on both sides of the helicopter. The upper part of the fuel tank bladder retains the fuel tank cap, and the interior retains the fuel quantity sensor, low fuel switch, fuel sump drain pipe (located in both left and right fuel tank bladders), and filter, etc. (not shown in the figure). The fuel quantity sensor and low fuel switch have the same size and structure as the actual product and may not include electronic components. The upper part of the left and right fuel tank bladders retains the vent pipe 112 connecting the two fuel tanks. The vent pipe 112 is fixed to the helicopter structure by clamp 117. The lowest end of the vent pipe is trimmed so that it does not extend below the test aircraft and is flush with the bottom of the test prototype. The middle part is the connecting fuel pipe 116 for transferring fuel between the two fuel tank bladders. The lower part also connects the fuel supply pipes of the left and right fuel tank bladders, and the fuel cut-off valve 115 is located in the middle of the fuel supply pipe. The fuel cut-off valve 115 is a ball valve manually operated from the cockpit. Other drain pipes and hoses of the fuel system are not considered.

[0097] (2) Representative structures in the surrounding area

[0098] like Figure 9 As shown, the left fuel tank bladder 111 is encapsulated within a sealed cavity mounted on top of the fuselage tower 122, located on both sides of the main rotor gearbox 152. This sealed cavity constitutes a representative structure for the helicopter fuel system crashworthiness test. The firewall 127 is identical to the actual firewall component of a helicopter; the forward fuselage skin 126 is riveted to the aft section 121 of the nacelle. The upper half of the fairing ring 123 is connected to the forward fuselage skin 126 by riveting, and the lower lugs are fixed to the fuselage tower 122 by bolt assemblies. The fuel tank bladder bracket 125 is connected to the forward fuselage skin 126, the fairing ring 123, and the firewall 127 by riveting, forming a representative external sealed structure for mounting the left fuel tank bladder 111. The aft section 121 of the nacelle, the fuel tank bladder bracket 125, the forward fuselage skin 126, the fairing ring 123, and the firewall 127 are all fixed to the fuselage tower 122 structure. The space between the left fuel tank bladder 111 and the external sealing representative structure is filled with a thick layer of open-cell foam 124, which effectively prevents the left fuel tank bladder 111 from collapsing and fuel sloshing, and also provides some protection against punctures. Additionally, the rear section 121 of the cabin is a section of the shell cut from a standard helicopter cabin, typically 0.4 meters in length H, located in front of the firewall 127 and fixedly connected to the fuselage tower, with its bottom trimmed to be flush with the bottom of the fuselage tower 122. The cabin shell is necessary in helicopter fuel system crashworthiness testing, providing a rigid connection point for the forward fuselage skin in the representative structure.

[0099] In this embodiment, any threaded connections that do not require fixing components to the prototype and the tail fairing bulkhead are omitted. Additionally, brackets, supports, and pipelines fixed to the fuselage tower 122 that could affect the horizontal and vertical collision of the representative structure need to be removed. The representative structure around the right fuel tank 113 is the same as that of the left fuel tank 111.

[0100] ② Assessment of potential puncture risks in the surrounding area

[0101] Taking into full account the potential damage to the surrounding structures of the helicopter's fuel system during a crash collision, the potential puncture hazards in the surrounding environment of the fuel system were assessed as much as possible. This is also one of the important methods in this test. Generally speaking, the area in front of the fuel tank bladder is the firewall 127 and the cabin outer shell, while the area behind the fairing ring 123 is empty space. Therefore, potential puncture hazards come from the following aspects:

[0102] (1) Below the fuel tank bladder

[0103] There may be several potential puncture hazards below the fuel system.

[0104] a. Fuselage tower

[0105] like Figure 7 As shown, the fuselage tower 122, located below the representative structure of the fuel system, is the helicopter's main load-bearing component. It is a welded steel tubular truss structure that protects the components within the fuselage tower from damage. Crash resistance testing must include and assess any potential puncture hazards posed by the tower.

[0106] b. Operating system

[0107] The helicopter's control system includes a collective pitch control system and a cyclic pitch control system. The control stick extends from the cockpit to the engine nacelle and finally connects to the automatic swashplate assembly 154 of the rotor mechanism. Since the control stick and other control components in the cockpit are blocked by the firewall 127, only the potential puncture hazard from the control stick and other control components behind the firewall 127 needs to be considered. In this embodiment, the helicopter's control system includes, as... Figure 10 As shown, it includes:

[0108] (i) Collective pitch control system: One end of the herringbone rocker arm 131 is fixed to the automatic swashplate assembly 154 by a bolt assembly, and the other end is connected to the first pull rod 132 by a bolt assembly. The other end of the first pull rod 132 is fixed to the triangular rocker arm 134 by a bolt assembly. The other end of the triangular rocker arm 134 is connected to the second pull rod 133 by a bolt assembly. Originally, the second pull rod 133 should be connected to the rocker arm in the cockpit, but since the puncture hazard of the control stick and other operating components behind the firewall 127 is not considered, it is necessary to use a bolt assembly to fix the free end of the second pull rod 133 to the fixed support 135 of the fuselage tower 122 to limit the attitude of the collective pitch.

[0109] (ii) Cyclic Pitch Control System: The cyclic pitch control system for the driver and co-pilot is symmetrically arranged. Lever 3 143 is connected to the double lugs of the automatic swashplate assembly 154 via bolt assemblies, and its other end is connected to the T-shaped rocker arm 142 via bolt assemblies. The other end of the T-shaped rocker arm 142 is connected to lever 4 141 via bolt assemblies. Similarly, the free end of lever 4 141 is fixed to the fixed support 2 144 of the fuselage tower 122 using bolt assemblies to limit the attitude of cyclic pitch control. The shock absorber on the T-shaped rocker arm 142 is ignored, and a steel pipe is used instead of the fine-tuning motor. Since the steel pipe has greater rigidity than the fine-tuning motor, this is a conservative but effective alternative. In some other embodiments, if a fine-tuning motor is present, both are installed in the same way.

[0110] c. Engine gearbox

[0111] To realistically simulate the load and reaction experienced by the fuselage tower 122 during a crash, the potential puncture hazard from the engine gearbox 155 located beneath the left and right fuel tank bladders must be considered. Figure 11 As shown, the engine gearbox 155 is fixed to the fuselage tower 122 via three supports (a top support 156 and a side support 157, and another symmetrically arranged side support not shown in the figure). This connection method ensures that the engine gearbox can generate realistic displacement and deformation during a crash collision of the test prototype 100. Since the impact load and deformation are generated when the engine gearbox contacts the ground, the mass of the engine gearbox is not the primary concern; the rigidity of the engine gearbox and its connected supports is more important. Therefore, in this embodiment, a scrapped engine gearbox is used as the most representative replacement, which not only ensures the rigidity requirements but also significantly reduces the test cost.

[0112] (2) Middle of the fuel tank bladder

[0113] The prototype 100 should consider adding components such as the main rotor gearbox 152, main rotor mast 153, driven pulley 151, and automatic swashplate assembly 154, as these are located in the middle of the fuel tank and very close to the fuel tank and fuel lines, potentially posing a puncture risk to the fuel system. Figure 11 As shown, the driven pulley 151 is mounted at the rear end of the main rotor gearbox 152 and fixed to the fuselage tower 122 by a tripod 158. The main rotor mast 153 is mounted in the middle of the main rotor gearbox 152, tilting upwards. The automatic swashplate assembly 154 is mounted at the lower part of the main rotor gearbox 152 and connected to the pull rods of the collective pitch control system and the cyclic torque control system. The main rotor gearbox 152 is fixed to four dedicated fixed supports at the top of the fuselage tower 122 by bolt assemblies. The dimensions and weight of the main rotor gearbox 152 should be consistent with the actual gearbox. The forward lubrication line at the lower front end of the main rotor gearbox 152 should also be retained (not shown in the figure) because it is close to the fuel system connecting oil line 116. Other external connecting components of the main rotor gearbox 152 do not need to be considered.

[0114] All structures, whether simplified or retained or added to account for potential puncture hazards, must be trimmed if they extend beyond the bottom of the test prototype 100 to ensure they are flush with the bottom of the test prototype 100 and that the test device can impact the rigid foundation in the correct direction.

[0115] ③ The attitude of each component

[0116] The experiment aimed to determine the attitude and location of the fuel system, representative surrounding structures, and components that could potentially cause puncture damage during a helicopter crash, simulating the actual conditions of each system during the crash. This was one of the key methods used in the experiment.

[0117] In this embodiment, the fuel system has been simplified by removing some unnecessary drain pipes and hoses; therefore, the inlets and outlets of these pipe connections must be plugged as required. The fuel tank cap of the fuel system is sealed closed, but the vent pipe 112 remains open to simulate natural venting. The bottom of the vent pipe 112 is wrapped with a plastic bag to collect any liquid that may spill. The fuel shut-off valve 115 is closed, and the oil pan drain pipe is also closed.

[0118] This embodiment also simulates a helicopter crash scenario. The collective pitch control system's collective pitch stick is fully extended, at which point the helicopter's lift is at its maximum, simulating the pilot's actual control when pulling the helicopter up with all their might during a crash. At the same time, the A-arm rocker arm 131 and the lever 132 are closest to the fuel tank bladder, increasing the risk of the collective pitch control system puncturing the fuel system. Meanwhile, the cyclic torque converter system is positioned approximately in neutral, preventing the helicopter from generating additional yaw and roll.

[0119] ④ Balance

[0120] To ensure the test device remains horizontal during the drop and that the tilt angle does not exceed the specified range, the center of gravity of the test prototype 100 (which is filled with 80% water at this time) and the drop platform 200 should be aligned. Specifically, the device can be lifted, and a section of metal pipe can be placed near its lower center for balance, thereby determining the center of gravity of the test prototype 100 and the drop platform 200.

[0121] ⑤ Camera placement

[0122] To obtain better and more accurate experimental data and images, the camera placement should be as follows: Figure 12 As shown. High-speed camera 001 and GoPro cameras 003 and 004 primarily film the impact of the test device on the rigid foundation, while ordinary camera 002 films the entire crash resistance test process, positioned at 45° to the prototype axis. High-speed camera 001 is activated by the opening of hook 202, and the other cameras are activated at the start of the test.

[0123] ⑥ Post-test inspection

[0124] After the crash test, the fuel system of the test prototype is inspected for leaks, including the left and right fuel tanks, fuel lines, and connectors. After inspecting the left and right fuel tanks, the prototype is left to stand for 15 minutes. The vent line 112 is then sealed, and the fuel tanks are inverted and inspected again for leaks. If no liquid leaks, seepage, or fuel system ruptures are found (a slight leak in the vent line 112 is acceptable), the fuel system passes the crash test; otherwise, the test fails.

[0125] ⑦ Other requirements

[0126] (1) Dyeing water was used instead of fuel oil in the test. First, it can ensure that the sparks generated by the test collision will not ignite the fuel oil. Second, dyeing water is convenient for leakage inspection after the collision.

[0127] (2) If necessary, counterweights can be added to the test device to balance the center of gravity of the test device and make it fall horizontally.

[0128] (3) There should be no crosswinds during the test, otherwise it will affect the test.

[0129] 3) Experiment

[0130] First, a final pre-drop inspection is conducted on the installation and lifting equipment of the test prototype 100 and the drop platform 200.

[0131] Then, the control system 400 opens the cargo hook 202, and the test prototype 100 and the drop platform 200 fall freely together, completing the collision on the rigid foundation 303.

[0132] Finally, the measurement data from position sensor 207 was checked to confirm that the pitch and roll angles of the test prototype 100 and the drop platform 200 did not exceed ±10°. All cameras were stopped, the test prototype was inspected, the data was recorded, and a helicopter fuel system crashworthiness test was completed.

[0133] The crashworthiness of a helicopter fuel system is crucial for helicopter safety. This invention simplifies the fuel system and its surrounding structure, proposing a representative structure that realistically reflects the fuel system during a helicopter crash. It fully considers the environment surrounding the fuel system, assesses all potential hazards, incorporates these hazards into a test prototype, and determines their attitude and position during a crash, accurately simulating the helicopter crash scenario. This provides a representative alternative for full-size helicopters used in fuel system crashworthiness testing. The invention also provides a test apparatus for the entire crashworthiness test, clearly defining the test process and methods. The test apparatus is simple, easy to assemble and disassemble, has low testing costs, good maneuverability, and a reliable and effective test method. Tests have demonstrated that the test method and apparatus provided by this patent are reliable and accurate, realistically simulating the impact and hazards experienced by the fuel system during a helicopter crash. It is highly suitable for helicopter fuel system crashworthiness testing and has significant practical application value.

[0134] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A helicopter fuel system crashworthiness testing device, characterized in that, include: Drop platform, rigid foundation components and control system; The drop platform includes steel cables, hooks, slings, cable guides, platform frames, guide frames, and position sensors; The rigid foundation assembly includes a balance beam, guide ropes, a rigid foundation, and lifting eye bolts; The drop platform is suspended below the balance beam by steel cables. One end of the steel cable is fixedly connected to the balance beam, and the other end is fixedly connected to the cargo hook. The platform frame is U-shaped, with front and back panels and open sides for placing the test prototype flat on it; one end of the hanging rope is hung on the cargo hook, and the other end is fixedly connected to the four fixed supports of the platform frame with four feet respectively. The hanging rope acts as a limit and closely follows the outer contour of the test prototype. The balance beam is equipped with guide ropes on both sides. One end of the guide ropes is fixed to the end of the balance beam, and the other end is fixed to the rigid foundation component by the lifting eye bolts, forming two slide rails. The balance beam is also connected to the hoisting equipment that can lift it to a certain height. Guide frames are installed on the exterior of the front and rear wall panels of the platform frame. Steel cable guides are installed at the four opposite corners of the guide frames on both sides to ensure that the platform frame falls freely along the guide rope without rotating or tilting. The cargo hook is an electronic cargo hook that can be opened and closed by a control system; The control system includes interconnected control boxes and cables, with the other end of the cables also connected to a cargo hook. The test prototype includes a fuel system, representative surrounding structures, and a puncture hazard. The fuel system retains the fuel storage unit and corresponding fuel supply pipeline components of the helicopter model under test. The fuel storage unit includes a left fuel tank and a right fuel tank arranged symmetrically. The upper part of the left and right fuel tanks retains the fuel tank cap, and the interior retains a fuel quantity sensor, a low fuel switch, a fuel sump drain pipe and a filter screen. The size and structure of the fuel quantity sensor and the low fuel switch are the same as those of the actual helicopter model under test. The representative surrounding structures include the rear section of the nacelle and the sealing cavities installed on the left and right sides of the top of the fuselage tower for encapsulating the left and right fuel tank bladders. The puncture hazards include the fuselage tower, control system, engine gearbox, main rotor gearbox, main rotor mast, driven pulley, and automatic swashplate assembly; The fuselage tower is located below the fuel system and its external sealing representative structure, and is a truss structure; The engine gearbox is located in the installation space between the left and right fuel tanks and is fixedly connected to the fuselage tower. The main rotor gearbox, main rotor mast, driven pulley, and automatic tilting disc assembly are all located in the installation space between the left and right oil tanks; The driven pulley is installed at the rear end of the main rotor gearbox and fixed to the fuselage tower; the main rotor mast is installed in the middle of the main rotor gearbox and tilted upwards; the automatic tilting disk assembly is installed at the lower part of the main rotor gearbox; the size and weight of the main rotor gearbox are consistent with the actual gearbox of the helicopter model under test and are fixed to the fuselage tower.

2. The helicopter fuel system crashworthiness testing device according to claim 1, characterized in that, The rigid foundation is a non-deformable reinforced concrete square foundation.

3. The helicopter fuel system crashworthiness testing device according to claim 1, characterized in that, Position sensors for measuring the horizontal tilt angle of the test prototype before the collision are installed at three corners of the platform frame, and the measurement data is received by the control system.

4. The helicopter fuel system crashworthiness testing device according to claim 1, characterized in that, The fuel supply pipeline components retain the vent pipes connecting the upper parts of the left and right fuel tanks to the two fuel tanks. The vent pipes are fixed to the helicopter structure, and the lowest end of the vent pipes is trimmed to be flush with the bottom of the test prototype. It also retains the connecting oil pipe in the middle for mutual fuel transfer, the fuel supply line in the lower part connecting the left and right fuel tanks, and the fuel cut-off valve located in the middle of the fuel supply line; The sealed cavity is surrounded by external sealing representative structures, including the fuel tank bracket, the front fuselage skin, the fairing ring, and the firewall. The firewall structure is consistent with the actual firewall components of the helicopter under test. The forward fuselage skin is fixed to the rear section of the nacelle, the upper part of the fairing ring is connected to the forward fuselage skin, and the lower part is fixed to the fuselage tower; The fuel tank bracket is also fixedly connected to the front fuselage skin, fairing ring, and back firewall; The rear section of the cabin is a shell section cut from the cabin of the helicopter model under test. It is located in front of the firewall and is fixedly connected to the fuselage tower. The bottom is trimmed to be flush with the bottom of the fuselage tower. The control system includes a collective pitch control system and a cyclic pitch control system; The collective pitch control system includes a V-shaped rocker arm, a first lever, a second lever, and a triangular rocker arm; One end of the herringbone rocker arm is fixed to the automatic tilting plate assembly, and the other end is fixedly connected to the first pull rod; the other end of the first pull rod is fixed to the triangular rocker arm; the other end of the triangular rocker arm is fixedly connected to the second pull rod; the free end of the second pull rod is fixed to the fuselage tower. The cyclic pitch control system includes a symmetrically arranged cyclic pitch control system for the driver and co-pilot, comprising lever three, a T-shaped rocker arm, and lever four. One end of the tie rod three is fixedly connected to the automatic tilting plate assembly, and the other end is connected to the T-shaped rocker arm by bolts. The other end of the T-shaped rocker arm is connected to the tie rod four by bolts. The free end of the tie rod four is fixed to the fuselage tower. A forward lubrication line is retained at the lower front end of the main rotor gearbox.

5. The helicopter fuel system crashworthiness testing device according to claim 4, characterized in that, The length of the rear section of the cabin is 0.4 meters.

6. The helicopter fuel system crashworthiness testing device according to claim 4, characterized in that, The shock absorber on the T-shaped rocker arm is ignored in the cyclic pitch control system, and a steel pipe is used instead of the fine-tuning motor.

7. A method for testing the crashworthiness of a helicopter fuel system, characterized in that, Includes the following steps: Step 1 Installation Using the helicopter fuel system crashworthiness test apparatus as described in any one of claims 1-6, the test prototype is placed flat on the drop platform, with the left and right sides of the test prototype centered relative to the longitudinal plane; The drop platform is placed at the center of the rigid base assembly, with the two central axes at 45 degrees to each other; The balance beam is slowly lifted using hoisting equipment. Once the drop platform is off the ground, the cable guide is adjusted so that the two guide ropes are centered on the cable guide and parallel to each other. At the same time, the entire drop platform is adjusted to a horizontal position based on the data received from the position sensor by the control system. Continue lifting the drop platform until it reaches the required height for the test, with the guide rope set to be just taut at this point; Step 2 Experiment The control system opens the cargo hook, allowing the test prototype to fall freely together with the drop platform, completing the collision on a rigid base, while a camera records the collision process. Step 3: Check Check the measurement data from the position sensor to confirm that the pitch and roll angles of the test prototype relative to the drop platform do not exceed the specified values. Inspect the test prototype, record the data, and complete a helicopter fuel system crashworthiness test.

8. The method according to claim 7, characterized in that, Step 1 also includes the following settings for the test prototype: (1) Dyeing water was used instead of fuel in the test. The left and right fuel tanks of the test prototype were filled with dyeing water at 80% volume. (2) If necessary, counterweights can be added to the helicopter fuel system crashworthiness test device to balance the center of gravity of the helicopter fuel system crashworthiness test device and make it fall horizontally.

9. The method according to claim 7, characterized in that, The cameras include ordinary cameras, high-speed cameras, and GoPro cameras; High-speed cameras and GoPro cameras were used to film the process of the helicopter fuel system crashworthiness test device impacting the rigid foundation. Ordinary cameras were used to photograph the entire crashworthiness test process.

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