Airplane hydraulic system and airplane

Abstract

This invention relates to an aircraft hydraulic system and an aircraft. The aircraft hydraulic system includes a valve position indicator, a flow-fuse valve, an adjustable clamping spring, a control valve, and a control switch. The valve position indicator indicates whether the flow-fuse valve is in the open or closed position. Hydraulic oil flows to the hydraulic user via the flow-fuse valve. The adjustable clamping spring is connected to the flow-fuse valve to apply preload pressure. The control valve is connected to the adjustable clamping spring to adjust the preload pressure. The control switch is connected to the control valve, thereby controlling the opening / closing of the control valve by turning the control switch on / off. When the aircraft is in normal operating condition, the flow-fuse valve closes when the hydraulic flow through it exceeds a first flow rate setting threshold. When the aircraft is in ground maintenance condition, the flow-fuse valve closes when the hydraulic flow through it exceeds a second flow rate setting threshold.

Description

Technical Field

[0001] This invention relates to aircraft hydraulic systems. Background Technology

[0002] In modern aircraft, the control surface operating system and power recovery system are almost entirely driven by hydraulic systems, such as the movement of landing gear, flaps, and spoilers. Therefore, hydraulic lines are inevitably distributed throughout the aircraft. The hydraulic system transmits hydraulic energy to the user system, with hydraulic oil flowing from the high-pressure side to the low-pressure side. Because the seals in the hydraulic system are consumable parts, they are at risk of failure after prolonged use. Even when closed, hydraulic oil will still flow from the high-pressure side to the low-pressure side within the hydraulic system. This phenomenon reduces system performance and energy efficiency. Prolonged leakage can lead to excessively low hydraulic oil levels, affecting system performance and even jeopardizing flight safety.

[0003] In the existing technology, one type of aircraft determines the internal leakage status by detecting system pressure. When the aircraft is on the ground, the hydraulic user is kept still, the electric pump is started and then turned off, and the time required for the system pressure to drop from 4500psi to 500psi is detected. If the time is less than 3 seconds, the internal leakage of the system is considered to be too large, and the user components of the system need to be disassembled and tested again on the next time.

[0004] Another type of aircraft uses ultrasonic flow sensors to periodically detect the flow rate of the hydraulic system. The time of ultrasonic wave emission and reception is related to the flow rate of the hydraulic system. The flow rate detected by the ultrasonic flow sensor is used to determine whether the leakage in the hydraulic pipeline exceeds the standard.

[0005] However, existing technologies for detecting leaks in aircraft hydraulic systems suffer from high maintenance costs and poor maintainability. Summary of the Invention

[0006] One object of the present invention is to provide an aircraft hydraulic system that can realize the function of internal leakage detection of the aircraft hydraulic system, reduce the maintenance cost of the hydraulic system, and improve the maintainability of the hydraulic system.

[0007] The above-mentioned objectives of the present invention are achieved by an aircraft hydraulic system, which includes a valve position indicator, a flow fusible valve, an adjustable clamping spring, a control valve, and a control switch.

[0008] The valve position indicator is used to indicate whether the flow fuse valve is in the open or closed position. Hydraulic oil flows to the hydraulic user through the flow fuse valve. The adjustable clamping spring is connected to the flow fuse valve to apply a preload pressure to the flow fuse valve. The control valve is connected to the adjustable clamping spring to adjust the preload pressure of the adjustable clamping spring. The control switch is connected to the control valve, so that the control valve is controlled to close or open by closing or opening the control switch.

[0009] When the aircraft is in normal operating condition, the control switch is turned off, thus the control valve is closed. The adjustable clamping spring applies a first preload pressure corresponding to a first flow rate setting threshold to the flow-fuse valve. When the hydraulic flow through the flow-fuse valve does not exceed the first flow rate setting threshold, the flow-fuse valve opens, and hydraulic oil flows to the hydraulic user. When the hydraulic flow through the flow-fuse valve exceeds the first flow rate setting threshold, the flow-fuse valve closes, preventing hydraulic oil from flowing to the hydraulic user. At this time, the valve position indicator indicates that the flow-fuse valve is closed.

[0010] When the aircraft is in ground maintenance mode, the control switch is turned on, thus opening the control valve. The adjustable clamping spring applies a second preload pressure corresponding to a second flow rate setting threshold to the flow-fuse valve. When the hydraulic flow rate through the flow-fuse valve does not exceed the second flow rate setting threshold, the flow-fuse valve opens, and hydraulic oil flows to the hydraulic user. When the hydraulic flow rate through the flow-fuse valve exceeds the second flow rate setting threshold, the flow-fuse valve closes, preventing hydraulic oil from flowing to the hydraulic user. At this time, the valve position indicator indicates that the flow-fuse valve is closed.

[0011] Wherein, the second flow rate setting threshold is less than the first flow rate setting threshold, and correspondingly, the second pre-tightening pressure is less than the first pre-tightening pressure.

[0012] According to the above technical solution, the aircraft hydraulic system of the present invention can achieve the following beneficial technical effects: it can realize the internal leakage detection function of the aircraft hydraulic system, reduce the maintenance cost of the hydraulic system, and improve the maintainability of the hydraulic system; moreover, it can cut off the hydraulic oil supply to the hydraulic user in time when a large leakage occurs, so as to ensure the hydraulic oil supply to other hydraulic users.

[0013] Preferably, the flow-controlled fuse valve is a pressure-controlled two-position two-way directional valve.

[0014] According to the above technical solution, the aircraft hydraulic system of the present invention can achieve the following beneficial technical effects: by using a suitable type of flow-stop valve, the opening / closing of the flow-stop valve can be better realized, thereby better realizing the internal leakage detection function of the aircraft hydraulic system, reducing the maintenance cost of the hydraulic system, and improving the maintainability of the hydraulic system.

[0015] Preferably, the control valve is an electrically controlled two-position two-way directional valve.

[0016] According to the above technical solution, the aircraft hydraulic system of the present invention can achieve the following beneficial technical effects: by using a suitable type of control valve, the preload pressure of the adjustable compression spring can be better adjusted, thereby better realizing the internal leakage detection function of the aircraft hydraulic system, reducing the maintenance cost of the hydraulic system, and improving the maintainability of the hydraulic system.

[0017] Preferably, the first flow rate setting threshold and the corresponding first preload pressure are determined according to different hydraulic users.

[0018] According to the above technical solution, the aircraft hydraulic system of the present invention can achieve the following beneficial technical effects: it can set different first flow rate setting thresholds and first preload pressures for different hydraulic users, thereby cutting off the hydraulic oil supply to the hydraulic user in time when a large leakage occurs, and ensuring the hydraulic oil supply to other hydraulic users.

[0019] Preferably, the first flow rate setting threshold is 105% to 110% of the normal flow rate when the hydraulic user is working normally.

[0020] According to the above technical solution, the aircraft hydraulic system of the present invention can achieve the following beneficial technical effects: by setting an appropriate first flow rate threshold, it can better cut off the hydraulic oil supply to the hydraulic user in time when a large leakage occurs, ensure the hydraulic oil supply to other hydraulic users, and at the same time leave appropriate redundancy to avoid frequent or accidental cut-off.

[0021] Preferably, the second flow rate setting threshold is 2 to 5 liters per minute.

[0022] According to the above technical solution, the aircraft hydraulic system of the present invention can achieve the following beneficial technical effects: by setting an appropriate second flow rate threshold, leakage in the hydraulic system can be detected more promptly, while also having appropriate redundancy to avoid false alarms of leakage in the hydraulic system.

[0023] Preferably, when the aircraft is in normal operating condition, the control switch is turned off, thus the control valve is closed, and the control valve does not apply any force to the adjustable clamping spring, so that the adjustable clamping spring applies a first preload pressure corresponding to the first flow rate setting threshold to the flow-off valve by its own spring force.

[0024] According to the above technical solution, the aircraft hydraulic system of the present invention can achieve the following beneficial technical effects: when the aircraft is in normal working condition, the control switch is closed and the control valve is closed, so the adjustable clamping spring can be easily adjusted to the first preload pressure corresponding to the first flow rate setting threshold, which can better cut off the hydraulic oil supply to the hydraulic user in time when a large leakage occurs, and ensure the hydraulic oil supply to other hydraulic users.

[0025] Preferably, when the aircraft is in a ground maintenance state, the control switch is turned on, thus opening the control valve. The control valve applies a force opposite to the spring force of the adjustable clamping spring to counteract a portion of the spring force, thereby the adjustable clamping spring applying a second preload pressure to the flow fuse corresponding to the second flow setting threshold.

[0026] According to the above technical solution, the aircraft hydraulic system of the present invention can achieve the following beneficial technical effects: when the aircraft is in a ground maintenance state, the control switch is turned on and the control valve is opened, so the adjustable clamping spring can be easily adjusted to the second preload pressure corresponding to the second flow rate setting threshold, which can better detect internal leakage of the hydraulic system in a timely manner, reduce the maintenance cost of the hydraulic system, and improve the maintainability of the hydraulic system.

[0027] Preferably, the hydraulic user includes any one of the following: landing gear, flaps, spoilers, rudder, elevator, ailerons, leading-edge slats, and thrust reversers.

[0028] According to the above technical solution, the aircraft hydraulic system of the present invention can achieve the following beneficial technical effects: it can perform internal leakage detection and large leakage cut-off for various hydraulic users.

[0029] The above-mentioned objectives of the present invention are also achieved by an aircraft comprising an aircraft hydraulic system as described in any of the foregoing aspects.

[0030] According to the above technical solution, the aircraft of the present invention can achieve the following beneficial technical effects: it can realize the internal leakage detection function of the aircraft hydraulic system, reduce the maintenance cost of the hydraulic system, and improve the maintainability of the hydraulic system; moreover, it can cut off the hydraulic oil supply to the hydraulic user in time when a large leakage occurs, so as to ensure the hydraulic oil supply to other hydraulic users. Attached Figure Description

[0031] Figure 1A This is a schematic diagram of an aircraft hydraulic system according to an embodiment of the present invention when the aircraft is in normal operating condition and the flow fuse valve is open.

[0032] Figure 1BThis is a schematic diagram of an aircraft hydraulic system according to an embodiment of the present invention when the aircraft is in normal operating condition and the flow fuse valve is closed.

[0033] Figure 2A This is a schematic diagram of an aircraft hydraulic system according to an embodiment of the present invention, in the state of aircraft ground maintenance, when the flow fuse valve is open.

[0034] Figure 2B This is a schematic diagram of an aircraft hydraulic system according to an embodiment of the present invention in the aircraft ground maintenance state when the flow fuse valve is closed.

[0035] List of reference numerals

[0036] 1: Valve position indicator;

[0037] 2: Flow-through fuse valve;

[0038] 3: Adjustable compression spring;

[0039] 4: Control valve;

[0040] 5: Control switch. Detailed Implementation

[0041] The following describes specific embodiments of the present invention. It should be noted that, in order to provide a concise description, this specification cannot exhaustively describe all features of the actual embodiments. It should be understood that, in the actual implementation of any embodiment, just as in any engineering or design project, various specific decisions are often made to achieve the developer's specific goals and to meet system-related or business-related constraints, and this can change from one embodiment to another. Furthermore, it is understood that although the efforts made in this development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this invention, some design, manufacturing, or production modifications based on the technical content disclosed herein are merely conventional technical means and should not be construed as insufficient content of this disclosure.

[0042] Unless otherwise defined, the technical or scientific terms used in the claims and description shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in the patent application description and claims of this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. The terms "an" or "a" and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms "comprising" or "including" and similar terms mean that the element or object preceding "comprising" or "including" encompasses the element or object listed following "comprising" or "including" and its equivalents, and do not exclude other elements or objects. The terms "connected" or "linked" and similar terms are not limited to physical or mechanical connections, nor are they limited to direct or indirect connections.

[0043] In the following description, in order to clearly demonstrate the structure and working method of the present invention, a number of directional terms will be used. However, terms such as "front", "back", "left", "right", "outside", "inside", "outward", "inward", "up", and "down" should be understood as convenient terms and not as limiting terms.

[0044] Figure 1A This is a schematic diagram of an aircraft hydraulic system according to an embodiment of the present invention when the aircraft is in normal operating condition and the flow fuse valve is open. Figure 1B This is a schematic diagram of an aircraft hydraulic system according to an embodiment of the present invention when the aircraft is in normal operating condition and the flow fuse valve is closed. Figure 2A This is a schematic diagram of an aircraft hydraulic system according to an embodiment of the present invention, in the state of aircraft ground maintenance, when the flow fuse valve is open. Figure 2B This is a schematic diagram of an aircraft hydraulic system according to an embodiment of the present invention, in the aircraft ground maintenance state, with the flow fuse valve closed. It should be noted that... Figures 1A to 2B The red arrow in the image indicates circulation. Figures 1A to 2B The green arrows in the diagram indicate that the flow is blocked or cut off.

[0045] like Figures 1A to 2B As shown, an aircraft hydraulic system according to an embodiment of the present invention includes a valve position indicator 1, a flow fuse valve 2, an adjustable pressure spring 3, a control valve 4, and a control switch 5.

[0046] Valve position indicator 1 is used to indicate whether the flow fuse valve 2 is in the open or closed position. Hydraulic oil flows to the hydraulic user through the flow fuse valve 2. Adjustable clamping spring 3 is connected to the flow fuse valve 2 to apply preload pressure to the flow fuse valve 2. Control valve 4 is connected to the adjustable clamping spring 3 to adjust the preload pressure of the adjustable clamping spring 3. Control switch 5 is connected to control valve 4, so that the control valve 4 is closed / opened by the closing / opening of control switch 5.

[0047] like Figures 1A to 1B As shown, when the aircraft is in normal operating condition, control switch 5 is closed, therefore control valve 4 is closed. Adjustable clamping spring 3 applies a first preload pressure corresponding to the first flow rate setting threshold to flow-fuse valve 2. When the hydraulic flow through flow-fuse valve 2 does not exceed the first flow rate setting threshold, such as... Figure 1A As shown, the flow-stop valve 2 opens, and hydraulic oil flows to the hydraulic user; when the hydraulic flow through the flow-stop valve 2 exceeds the first flow-setting threshold (for example, when there is a rupture in the hydraulic user or the hydraulic user's pipeline causing a large amount of hydraulic oil leakage), such as Figure 1B As shown, the flow-stop valve 2 is closed, preventing hydraulic oil from flowing to the hydraulic user. This allows for timely cutting off of the hydraulic oil supply to the hydraulic user in the event of a large leak, ensuring the hydraulic oil supply to other hydraulic users and preventing the entire hydraulic system from failing due to a rupture in the remote structure. At this time, the valve position indicator 1 indicates that the flow-stop valve 2 is closed.

[0048] like Figures 2A to 2B As shown, when the aircraft is in ground maintenance mode, control switch 5 is turned on, thus control valve 4 opens. Adjustable clamping spring 3 applies a second preload pressure to flow fuse valve 2, corresponding to the second flow set threshold. When the hydraulic flow through flow fuse valve 2 does not exceed the second flow set threshold, such as... Figure 2A As shown, the flow-fuse valve 2 opens, and hydraulic oil flows to the hydraulic user; when the hydraulic flow through the flow-fuse valve 2 exceeds the second flow setting threshold (also known as excessive internal leakage), as... Figure 2B As shown, the flow fuse valve 2 is closed, preventing hydraulic oil from flowing to the hydraulic user. At this time, the valve position indicator 1 indicates that the flow fuse valve 2 is closed, thereby timely detecting and indicating leakage in the hydraulic system.

[0049] The second flow rate setting threshold is less than the first flow rate setting threshold, and correspondingly the second preload pressure is less than the first preload pressure.

[0050] According to the above technical solution, the aircraft hydraulic system of the present invention can achieve the following beneficial technical effects: it can realize the internal leakage detection function of the aircraft hydraulic system, reduce the maintenance cost of the hydraulic system, and improve the maintainability of the hydraulic system; moreover, it can cut off the hydraulic oil supply to the hydraulic user in time when a large leakage occurs, so as to ensure the hydraulic oil supply to other hydraulic users.

[0051] Specifically, this invention achieves internal leakage detection of aircraft hydraulic systems without adding hydraulic valves (only using a flow-controlled fuse valve to replace the existing hydraulic valves in the prior art) and without using ground support equipment (such as ground detection systems, flow sensors, etc.), thereby reducing hydraulic system maintenance costs and improving hydraulic system maintainability. The high-flow safety valve (flow-controlled fuse valve) can cut off the oil circuit protection system when a large leakage occurs downstream. By adding a low-flow mode to the high-flow safety valve (by adding a valve core control spring and its control valve; during maintenance, the control valve is opened to change the spring compression, thereby reducing the operating flow of the safety valve to the internal leakage flow set threshold), the flow-controlled fuse valve will close and indicate when the internal leakage exceeds the limit, thus achieving internal leakage detection.

[0052] Preferably, the valve position indicator 1 can be a mechanical or electronic indicator integrated into the aircraft's onboard maintenance system.

[0053] In some embodiments, such as Figures 1A to 2B As shown, the flow-controlled fuse valve 2 is a pressure-controlled two-position, two-way directional valve. In other words, the flow-controlled fuse valve 2 is a two-position, two-way directional valve whose pressure is controlled by changes in flow rate. When the pressure exceeds the set pressure threshold due to excessive flow (i.e., when the flow rate exceeds the set flow threshold), the flow-controlled fuse valve 2 switches from the open position to the closed position, preventing hydraulic oil from flowing through. Therefore, by using a suitable type of flow-controlled fuse valve, the opening / closing of the flow-controlled fuse valve can be better realized, thereby better realizing the internal leakage detection function of the aircraft hydraulic system, reducing the maintenance cost of the hydraulic system, and improving the maintainability of the hydraulic system.

[0054] In some embodiments, such as Figures 1A to 2B As shown, control valve 4 is an electrically controlled two-position two-way directional valve. Therefore, by using a suitable type of control valve, the preload pressure of the adjustable clamping spring can be better adjusted, thereby better realizing the internal leakage detection function of the aircraft hydraulic system, reducing the maintenance cost of the hydraulic system, and improving the maintainability of the hydraulic system.

[0055] In some embodiments, the first flow rate setting threshold and the corresponding first preload pressure are determined according to different hydraulic users. Therefore, different first flow rate setting thresholds and first preload pressures can be set for different hydraulic users, thereby promptly cutting off the hydraulic oil supply to that hydraulic user in the event of a large leak, while ensuring the hydraulic oil supply to other hydraulic users.

[0056] In some embodiments, the first flow rate setting threshold is 105% to 110% of the normal flow rate of the hydraulic user during normal operation. Therefore, by setting an appropriate first flow rate setting threshold, it is possible to better cut off the hydraulic oil supply to the hydraulic user in a timely manner when a large leakage occurs, ensuring the hydraulic oil supply to other hydraulic users, while also leaving appropriate redundancy to avoid frequent or accidental cut-offs.

[0057] For example, taking the landing gear of a certain aircraft model as an example, the normal flow rate of the landing gear when it is working normally is 120 liters / minute. Therefore, the first flow rate setting threshold can be set to 105% to 110% of the normal flow rate of 120 liters / minute, that is, 126 to 132 liters / minute.

[0058] In some embodiments, the second flow rate setting threshold is 2 to 5 liters per minute. Therefore, by using an appropriate second flow rate setting threshold, leakage in the hydraulic system can be detected more promptly, while also providing adequate redundancy to avoid false alarms of leakage in the hydraulic system.

[0059] In some embodiments, such as Figures 1A to 1B As shown, when the aircraft is in normal operating condition, control switch 5 is closed, therefore control valve 4 is closed. Control valve 4 does not apply any force to the adjustable clamping spring 3, thus the adjustable clamping spring 3 relies on its own spring force to apply a first preload pressure corresponding to the first flow rate setting threshold to the flow-stop valve 2. Therefore, when the aircraft is in normal operating condition, control switch 5 is closed, control valve 4 is closed, and the adjustable clamping spring 3 can be easily adjusted to the first preload pressure corresponding to the first flow rate setting threshold. This allows for better timely disconnection of hydraulic oil supply to a hydraulic user in the event of a large leak, ensuring hydraulic oil supply to other hydraulic users.

[0060] In some embodiments, such as Figures 2A to 2B As shown, when the aircraft is in ground maintenance mode, control switch 5 is activated, thus opening control valve 4. Control valve 4 applies a force opposite to the spring force of adjustable clamping spring 3 to counteract part of the spring force. This causes adjustable clamping spring 3 to apply a second preload pressure corresponding to the second flow rate setting threshold to flow-stop valve 2. Therefore, when the aircraft is in ground maintenance mode, with control switch 5 activated and control valve 4 open, adjustable clamping spring 3 can be easily adjusted to the second preload pressure corresponding to the second flow rate setting threshold. This allows for better and more timely detection of internal leaks in the hydraulic system, reduces hydraulic system maintenance costs, and improves hydraulic system maintainability.

[0061] In some embodiments, the hydraulic user includes any of the following: landing gear, flaps, spoilers, rudder, elevator, ailerons, leading-edge slats, and thrust reversers. Therefore, internal leakage detection and large leakage shut-off can be performed for a variety of different hydraulic users.

[0062] According to an embodiment of the present invention, an aircraft includes an aircraft hydraulic system as described in any of the above aspects. Based on the above technical solution, the aircraft of the present invention can achieve the following beneficial technical effects: it can realize the internal leakage detection function of the aircraft hydraulic system, reduce the maintenance cost of the hydraulic system, and improve the maintainability of the hydraulic system; moreover, it can promptly cut off the hydraulic oil supply to a hydraulic user in the event of a large leakage, ensuring the hydraulic oil supply to other hydraulic users.

[0063] The specific embodiments of the present invention have been described above. However, those skilled in the art will understand that the above specific embodiments do not constitute a limitation on the present invention. Those skilled in the art can make various modifications based on the above disclosure without exceeding the scope of the present invention.

Claims

1. An aircraft hydraulic system, the aircraft hydraulic system comprising a valve position indicator, a flow fusible valve, an adjustable clamping spring, a control valve, and a control switch; wherein The valve position indicator is used to indicate whether the flow fuse valve is in the open or closed position. Hydraulic oil flows to the hydraulic user through the flow fuse valve. The adjustable clamping spring is connected to the flow fuse valve to apply a preload pressure to the flow fuse valve. The control valve is connected to the adjustable clamping spring to adjust the preload pressure of the adjustable clamping spring. The control switch is connected to the control valve, so that the closing / opening of the control valve is controlled by the closing / opening of the control switch. When the aircraft is in normal operating condition, the control switch is turned off, thus the control valve is closed. The adjustable clamping spring applies a first preload pressure corresponding to a first flow rate setting threshold to the flow-fuse valve. When the hydraulic flow through the flow-fuse valve does not exceed the first flow rate setting threshold, the flow-fuse valve opens, and hydraulic oil flows to the hydraulic user. When the hydraulic flow through the flow-fuse valve exceeds the first flow rate setting threshold, the flow-fuse valve closes, preventing hydraulic oil from flowing to the hydraulic user. At this time, the valve position indicator indicates that the flow-fuse valve is closed. When the aircraft is in ground maintenance mode, the control switch is turned on, thus opening the control valve. The adjustable clamping spring applies a second preload pressure corresponding to a second flow rate setting threshold to the flow-fuse valve. When the hydraulic flow rate through the flow-fuse valve does not exceed the second flow rate setting threshold, the flow-fuse valve opens, and hydraulic oil flows to the hydraulic user. When the hydraulic flow rate through the flow-fuse valve exceeds the second flow rate setting threshold, the flow-fuse valve closes, preventing hydraulic oil from flowing to the hydraulic user. At this time, the valve position indicator indicates that the flow-fuse valve is closed. Wherein, the second flow rate setting threshold is less than the first flow rate setting threshold, and correspondingly, the second pre-tightening pressure is less than the first pre-tightening pressure.

2. The aircraft hydraulic system of claim 1, wherein, The flow-controlled fuse valve is a pressure-controlled two-position two-way directional valve.

3. The aircraft hydraulic system of claim 1, wherein, The control valve is an electrically controlled two-position two-way directional valve.

4. The aircraft hydraulic system of claim 1, wherein, The first flow rate setting threshold and the corresponding first preload pressure are determined according to different hydraulic users.

5. The aircraft hydraulic system of claim 1, wherein, The first flow rate setting threshold is 105% to 110% of the normal flow rate when the hydraulic user is working normally.

6. The aircraft hydraulic system as claimed in claim 1, characterized in that, The second flow rate setting threshold is 2 to 5 liters per minute.

7. The aircraft hydraulic system of claim 1, wherein, When the aircraft is in normal operating condition, the control switch is turned off, and therefore the control valve is closed. The control valve does not apply any force to the adjustable clamping spring, so the adjustable clamping spring applies a first preload pressure corresponding to the first flow rate setting threshold to the flow fuse valve by its own spring force.

8. The aircraft hydraulic system of Claim 7, wherein, When the aircraft is in ground maintenance mode, the control switch is turned on, thus opening the control valve. The control valve applies a force opposite to the spring force of the adjustable clamping spring to counteract part of the spring force, thereby the adjustable clamping spring applying a second preload pressure to the flow fuse corresponding to the second flow setting threshold.

9. The aircraft hydraulic system of Claim 1 wherein, The hydraulic users include any of the following: landing gear, flaps, spoilers, rudder, elevator, ailerons, leading-edge slats, and thrust reversers.

10. An aircraft comprising an aircraft hydraulic system as claimed in any one of claims 1-9.

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