Method for automatically testing hydraulic system of aircraft, control and monitoring unit for hydraulic system of aircraft, hydraulic system for aircraft, aircraft and computer program

Abstract

In order to reduce the time and workload during maintenance, the invention proposes a method of automatically testing a hydraulic system of an aircraft, a control and monitoring unit for a hydraulic system of an aircraft, a hydraulic system for an aircraft, an aircraft and a computer program. Wherein the hydraulic system (12) comprises a hydraulic pump (14) onboard the aircraft (10), a hydraulic reservoir (16), a hydraulic conduction system (18), a hydraulic drive unit (20), and a control and monitoring unit (22). The method comprises: a) pressurizing the hydraulic system (12) by means of the hydraulic pump (14); b) monitoring at least one parameter indicative of an external leak of the hydraulic system (12) during pressurization of the hydraulic system (12); c) determining whether an external leakage of the hydraulic system (12) is present on the basis of the at least one parameter.

Description

Technical Field

[0001] The invention relates to a method for automatically testing a hydraulic system of an aircraft during ground service. Furthermore, the invention relates to a device and a computer program for carrying out such a method. Background Art

[0002] For technical background, refer to the following literature:

[0003] [1] Hydraulic Ground Power Unit - Trunk Aircraft - 3000 psi and 5000 psi, company brochure of Test-Fuchs GmbH, downloaded from the Internet at www.test-fuchs.com on 29 August 2023

[0004] Current ground maintenance concepts for hydraulic systems of aircraft rely on the use of ground support equipment available at the airport, such as hydraulic ground carts, an example of which is disclosed in [1]. The procurement, logistics and use of these ground carts are important for airport operators. If a ground cart is not available at the location of the aircraft, delays will result. Maintenance personnel need to operate the ground carts and intervene during certain maintenance procedures. Summary of the invention

[0005] The object of the present invention is to reduce the time and costs for certain maintenance procedures during ground service.

[0006] To achieve such an object, the present invention provides a method according to one main aspect of the present application. Other main aspects of the present application relate to a control and monitoring unit, a hydraulic system, an aircraft and a computer program for executing the method.

[0007] Subsidiary aspects of the application relate to advantageous embodiments.

[0008] According to a first aspect of the present invention, there is provided a method for automatically testing a hydraulic system of an aircraft during ground service, wherein the hydraulic system comprises a hydraulic pump, a hydraulic reservoir, a hydraulic transmission system, a hydraulic drive unit and a control and monitoring unit onboard the aircraft, the method comprising:

[0009] a) pressurizing the hydraulic system with the aid of a hydraulic motor-pump unit,

[0010] b) monitoring at least one parameter indicative of an external leakage of the hydraulic system during pressurization of the hydraulic system,

[0011] c) determining whether an external leak of the hydraulic system exists based on the at least one parameter.

[0012] Preferably, before step a), the following steps are performed:

[0013] aa) Manually triggering the test procedure comprising steps a) to c).

[0014] Preferably, before step a), the following steps are performed:

[0015] bb) Automatically check whether the pressurization conditions of the hydraulic system are met.

[0016] Preferably, step bb) comprises:

[0017] bb1) Check if the aircraft is on the ground.

[0018] Preferably, step bb) comprises:

[0019] bb2) Check whether the temperature is within predetermined limits.

[0020] Preferably, step a) comprises:

[0021] a1) Pressurize the hydraulic system to a predetermined level.

[0022] Preferably, step a) comprises:

[0023] a2) Command the pump to pressurize the system with the aid of the control and monitoring unit.

[0024] Preferably, step a) comprises:

[0025] a3) Keep the hydraulic system pressurized by controlling the pump to compensate only for internal leakage.

[0026] Preferably, step a) comprises:

[0027] a4) Turn off the pump when the hydraulic system is pressurized.

[0028] Preferably, step a) comprises:

[0029] a5) Keep the hydraulic system pressurized by controlling the pump to maintain the pressure in the hydraulic system.

[0030] Preferably, the parameter to be monitored in step b) is selected from the group of parameters comprising pressure in the hydraulic system, output power of the pump and fluid level in the reservoir.

[0031] According to a preferred embodiment of the method comprising step a3), an external leakage is determined when:

[0032] Detects a decrease in pressure over time in the hydraulic system, or

[0033] • Detection of a decrease in reservoir liquid level over time.

[0034] According to a preferred embodiment of the method comprising step a4), an external leakage is determined when:

[0035] a decrease in pressure over time in the hydraulic system is detected which is different from, i.e., faster than, the decrease in pressure due to an internal leak, or

[0036] • Detection of a decrease in reservoir liquid level over time.

[0037] According to a preferred embodiment of the method comprising step a5), the external leakage is determined when the output power of the pump increases.

[0038] Preferably, the hydraulic system comprises an isolation device configured to isolate parts of the hydraulic system from each other, wherein the method further comprises the following steps:

[0039] d) In the case where an external leakage is determined in step c), the external leakage is located by isolating the parts of the hydraulic system using an isolation device and performing steps a) to c) on one, multiple or all of the isolated parts to determine in which part of the parts the external leakage occurs.

[0040] Preferably, step d) comprises the following steps:

[0041] d1) Isolating the hydraulic system into a first portion located upstream of the isolation device and a second portion located downstream of the isolation device.

[0042] Preferably, step d) comprises the following steps:

[0043] d2) performing steps a) to c) on the first part, and

[0044] d2a) locating the external leak downstream of the isolation device when the external leak is no longer detected,

[0045] d2b) locating the external leak upstream of the isolation device if the external leak is still detected, and

[0046] d2c) in case the external leak is detected to be reduced in size, locating the external leak such that a first external leak is located upstream of the isolation device and a second external leak is located downstream of the isolation device.

[0047] Preferably, the second part of the hydraulic system remains isolated in case of d2a) or d2c) to prevent system loss due to external leakage.

[0048] Preferably, other isolation devices are used to further refine the positioning.

[0049] According to a preferred embodiment of the present invention, external leak detection is performed in flight, preferably with positioning, and more preferably with isolation, for example, using the apparatus and steps as described in one or more of the aforementioned embodiments to perform external leak detection in flight, preferably with positioning, and more preferably with isolation.

[0050] Therefore, according to another aspect, the present invention provides a method for automatically testing a hydraulic system of an aircraft, wherein the hydraulic system comprises a hydraulic pump, a hydraulic reservoir, a hydraulic transmission system, a hydraulic drive unit and a control and monitoring unit on board the aircraft, the method comprising:

[0051] Performing the method for testing during ground service according to any of the preceding embodiments, and performing the following steps for testing in flight:

[0052] 6b) monitoring at least one parameter indicative of an external leakage of the hydraulic system, and

[0053] 6c) Determining whether an external leak of the hydraulic system exists based on the at least one parameter.

[0054] Preferably, the method further comprises leak locating an external leak detected in flight when the hydraulic system comprises an isolation device, the isolation device being configured to isolate parts of the hydraulic system from each other. According to a preferred embodiment, the method for testing in flight further comprises the following steps:

[0055] 6d) In the case where an external leakage is determined in step 6c), the external leakage is located by isolating the parts of the hydraulic system using an isolation device and performing steps 6b) and 6c) on one part, multiple parts or all parts of the isolated parts to determine in which part of the parts the external leakage occurs.

[0056] Preferably, step 6d) comprises the following steps:

[0057] 6d1) Isolating the hydraulic system into a first part located upstream of the isolation device and a second part located downstream of the isolation device.

[0058] Preferably, step 6d) comprises the following steps:

[0059] 6d2) performing steps 6b) and 6c) on the first part, and

[0060] 6d2a) locating the external leak downstream of the isolation device when the external leak is no longer detected,

[0061] 6d2b) locating the external leak upstream of the isolation device if the external leak is still detected, and

[0062] 6d2c) In case the external leak is detected to be reduced in size, locating the external leak such that a first external leak is located upstream of the isolation device and a second external leak is located downstream of the isolation device.

[0063] Preferably, the second part of the hydraulic system remains isolated in case of 6d2a) or 6d2c) to prevent system loss due to external leakage.

[0064] Preferably, other isolation devices are used during flight to further refine the positioning.

[0065] According to another aspect, the invention provides a control and monitoring unit for a hydraulic system of an aircraft, the control and monitoring unit being configured to control and monitor the hydraulic system to perform a method according to any of the preceding embodiments. Preferably, the control and monitoring unit comprises a processor and a memory, the memory comprising a computer program with instructions for executing the method.

[0066] According to another aspect, the present invention provides a hydraulic system for an aircraft, the hydraulic system comprising: a pump; a hydraulic reservoir; a hydraulic transmission system; a hydraulic drive unit; at least one sensor for a parameter of the hydraulic system indicating external leakage; and a control and monitoring unit, wherein the control and monitoring unit is configured to control the hydraulic system to perform a method according to any one of the aforementioned embodiments.

[0067] Preferably, the hydraulic pump is part of a hydraulic motor-pump unit. In particular, the pump is part of an electrically driven hydraulic motor-pump unit, in particular a power pack.

[0068] Preferably, the hydraulic conduction system comprises a plurality of distribution lines.

[0069] Preferably, the hydraulic system further comprises at least one isolating means, preferably a plurality of isolating means, configured to isolate parts of the hydraulic system from each other.Preferably, the isolating means comprises valves controlled by the control and monitoring unit.

[0070] Preferably, the at least one sensor is selected from the group consisting of: a pressure sensor for sensing the pressure in the hydraulic system; a sensor for determining the level of the hydraulic fluid in the reservoir; and an output power sensor for determining the power output of the pump. Preferably, the output power sensor is configured to determine the power required by the electric motor-pump unit.

[0071] Preferably, the control and monitoring unit is further configured to monitor parameters during flight to determine external leaks of the hydraulic system.

[0072] Preferably, the control and monitoring unit is further configured to cause the hydraulic system to perform one, multiple or all of steps d), d1) and d2) in flight. Preferably, the control and monitoring unit is further configured to cause the hydraulic system to keep the second part of the hydraulic system isolated in flight in the case of d2a) or d2c) to prevent system loss caused by external leakage.

[0073] Preferably, also during the external positioning performed during flight, further isolating means are used to further refine the positioning.Preferably, the control and monitoring unit is configured to control further isolating means to further refine the positioning.

[0074] According to a further aspect, the invention provides an aircraft comprising a hydraulic system according to one of the preceding embodiments and / or a control and monitoring unit according to one of the preceding embodiments.

[0075] According to another aspect, the invention provides a computer program comprising instructions for causing a hydraulic system of one of the preceding embodiments to perform the steps of a method according to any of the preceding embodiments.

[0076] The preferred embodiments of the present invention provide methods and apparatus for external leak detection and location utilizing a hydraulic power pack.

[0077] With respect to hydraulic systems, when a fluid leak occurs within that system, the leak is internal. An external leak is a leak of hydraulic fluid from the hydraulic system to the outside. External leaks may occur, for example, due to hose ruptures and loose hose fittings. In some embodiments, the A / C hydraulic system has primarily internal leaks due to the function of the servo control. The servo control is used in standard actuators, such as flight control actuation. The servo control requires a minimum internal flow to operate. This internal flow is considered internal leakage (from HP to LP). Wear of the servo valve causes an increase in this internal leakage, but even new servo valves have internal leaks.

[0078] In some embodiments of the invention, hydraulic ground support equipment on an airport is replaced. This is accomplished via enhancements to the aircraft hydraulic system and already installed hardware. In some embodiments, the hydraulic system, equipment, software including monitoring and control, and / or maintenance strategies are therefore designed and / or adjusted to perform ground maintenance.

[0079] Some embodiments of the present invention are able to control a hydraulic motor-pump unit similar to a ground cart but from the aircraft (e.g., a hydraulic motor-pump unit of a power pack). This operation goes beyond current functionality, applies predetermined settings for scheduled maintenance, and also allows for fully independent control. This is an advantage for every operator, especially at small sites (such as small airports) where less ground service equipment is available.

[0080] Currently, external leak testing of aircraft hydraulic systems is performed entirely manually. For example, using a hydraulic ground power unit cart such as disclosed in [1], the hydraulic ground power unit is connected to the aircraft hydraulic system via a hydraulic port, and the hydraulic system is pressurized and the reservoir fluid level is checked or only visually inspected. If this level decreases over time, a leak can be expected. If this is the case, maintenance personnel must perform a visual inspection of the entire hydraulic system to locate the leak.

[0081] Using the method and apparatus of the present invention, external leak testing is performed with the device on board the aircraft, most preferably without the need for visual inspection.

[0082] By introducing the ground cart function into the onboard hydraulic system, at least one, several or all of the following advantages can be achieved in preferred embodiments of the present invention:

[0083] Significantly reduce costs for airport maintenance operators – e.g., reduction in personnel, procurement, logistics.

[0084] · Floor maintenance is more flexible. For example, there is no need to keep floor carts available and / or maintenance can be performed in a substation.

[0085] No common failures on different aircraft due to contaminated ground carts.

[0086] • More flexible use of hydraulic fluid, especially new hydraulic fluid. The fluid is dedicated only to the aircraft and is not used in public maintenance points, such as ground carts.

[0087] Increased safety. For example, one uses all the control and monitoring devices installed on the aircraft, for example, automatically stopping pressurization if an external leak is detected.

[0088] Reduced probability of incorrect testing (due to automated maintenance routines).

[0089] Greater flexibility in case of new maintenance procedures. For example, the use of hydraulic pumps allows all functions within the aircraft's operating cycle.

[0090] No additional weight is added to the aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0091] Embodiments of the present invention are explained below with reference to the accompanying drawings, in which:

[0092] Figure 1 is a side view of the aircraft during ground service;

[0093] Figure 2 is a schematic simplified block diagram of the hydraulic system of an aircraft;

[0094] Figure 3 is a flow chart of an embodiment of a method for testing a hydraulic system; and

[0095] Figure 4 is a flow chart of the other steps of the method. DETAILED DESCRIPTION

[0096] Figure 1 and Figure 2 An embodiment of an aircraft 10 is shown having a hydraulic system 12 . The hydraulic system 12 comprises a hydraulic pump 14 , a hydraulic reservoir 16 , a hydraulic transmission system 18 , a hydraulic drive unit 20 and a control and monitoring unit 22 on board the aircraft 10 .

[0097] In some embodiments, the hydraulic system 12 includes one or more hydraulic (electric) power packs (HPP) 24, which include a pump 14, an (electric) motor 25 for driving the pump 14, a reservoir 16 and multiple sensors, wherein the multiple sensors include: a fluid level sensor 26, a pressure sensor 28 and a power sensor 30, the fluid level sensor 26 is used to detect the reservoir fluid level, the pressure sensor 28 is used to detect the pressure in the hydraulic system 12, and the power sensor 30 is used to detect the output power of the pump 14, for example, by detecting the output power of the pump 14 by detecting the electric power required to drive the pump 14.

[0098] The hydraulic transmission system 18 comprises a plurality of hydraulic lines 32 , in particular hydraulic distribution lines, and isolating means 34 , such as valves 36 , for isolating parts of the hydraulic system 12 from one another.

[0099] The control and monitoring unit 22 may be implemented in one component or as a control and monitoring system comprising a plurality of components. The control and monitoring unit 22 comprises a processor 38 and a memory 40 comprising a computer program having instructions for causing the hydraulic system 12 to perform the method mentioned below.

[0100] The control and monitoring unit 22 is configured to control and monitor the hydraulic system 12. In some embodiments, the control and monitoring unit 22 is connected to the HePP 24 and the isolation device 34 via a communication line 42. In addition, the control and monitoring unit 22 is connected to an aircraft control unit 44, which includes a user interface and a plurality of devices for detecting the state of the aircraft 10 and environmental parameters, such as temperature. For example, in Figure 2 A temperature sensor 46 is shown in FIG.

[0101] During ground service, if Figure 1 As shown, the external leak test can be performed using the components 12, 22 on the aircraft without the need for a ground cart 48. In other words, the ground cart function "external leak test" is introduced into the onboard hydraulic system 12.

[0102] Methods used to automatically test hydraulic systems include:

[0103] a) Pressurize the hydraulic system with the help of a hydraulic pump,

[0104] b) monitoring at least one parameter indicative of an external leakage of the hydraulic system during pressurization of the hydraulic system,

[0105] c) determining whether an external leak of the hydraulic system exists based on the at least one parameter.

[0106] Figure 3 A flow chart of a preferred embodiment of a method for testing a hydraulic system 12 implementing an external leak test is shown. As an optional feature, external leaks may also be located using the device 12, 22 on the aircraft. Figure 4 A flow chart showing a preferred embodiment of this optional leak localization is shown.

[0107] exist Figure 3 and Figure 4 The reference numerals used in the text refer to the following:

[0108] ELD External Leak Detection

[0109] MC Maintenance Staff

[0110] HePP Hydraulic Electric Power Pack

[0111] CMU control and monitoring unit

[0112] IM Isolation Devices

[0113] Y is

[0114] No

[0115] S1 triggers leak detection

[0116] S2 checks whether the test condition is met

[0117] S3 indicates that the test failed

[0118] S4 command pressurization

[0119] S5 pressurizes the hydraulic system

[0120] S6 sends sensor data (pressure, reservoir, level, power)

[0121] S7 monitors reservoir level, system pressure & power

[0122] S8 indicates the test was completed and no findings were found

[0123] S9 indicates external leakage

[0124] ELL External Leak Location

[0125] S10 Start: Leak detected

[0126] S11 starts positioning

[0127] S12 command isolation

[0128] S13 Isolate the hydraulic lines

[0129] S14 command pressurization

[0130] S15 pressurizes the hydraulic system

[0131] S16 sends sensor data (pressure, reservoir, level, power)

[0132] S17 monitors reservoir level, system pressure & power

[0133] S18 leak?

[0134] S19 indicates the isolation downstream of the isolation device

[0135] S20 Are other isolation devices available?

[0136] S21 indicates positioning upstream of the isolation device

[0137] Reference Figure 2 and Figure 3 , an external leakage test is performed using devices installed on the aircraft 10, in particular using a hydraulic motor-pump unit, such as HePP 24, and a control and monitoring unit 22. In some embodiments, the test can be automatically performed by the following time sequence:

[0138] The S1 maintenance personnel MC triggers the test when testing is required.

[0139] S2 The control and monitoring unit CMU 22 then checks whether all conditions for pressurizing the hydraulic system are met, such as the aircraft 10 being on the ground, the temperature being within limits, etc. If this is the case (Y), the next step S4 follows; otherwise, a test failure is indicated in step S3. S4, S5 The hydraulic system 12 is pressurized to a defined value, and

[0140] a. Keep the hydraulic system 12 pressurized by controlling the pump 14 to compensate only for internal leaks, or

[0141] b. Then turn off pump 14, or

[0142] c. Keep the hydraulic system 12 pressurized by controlling the pump 14 to maintain pressure.

[0143] S6, S7 The hydraulic system pressure, the reservoir level and the HePP output power monitored by the control and monitoring unit 22 on board the aircraft are indicators of an external leak, or in other words, parameters indicative of an external leak. According to the implementation of steps S4, S5 (as in the alternatives a., b. or c. mentioned above), the performance of the hydraulic system 12 is monitored.

[0144] a. If the pressure decreases over time differently than the decrease caused by an internal leak, or if the reservoir liquid level decreases over time, an external leak can be expected.

[0145] b. If the pressure decreases differently than would be caused by an internal leak - ie, decreases more quickly, or if the reservoir level decreases over time, an external leak may be expected.

[0146] c. If the power output of the HePP 24 increases, then a higher flow demand is expected to be the root cause. This indicates an external leak.

[0147] S8, S9 When the test is completed, the results are provided to the maintenance personnel MC.

[0148] In some embodiments, an enhanced function that extends the method for testing external leakage ELD is leak location ELL. The preferred implementation of this function is Figure 4 . This function replaces the visual inspection of the hydraulic system 12 after an external leak is detected. In order to achieve leak location, an isolation device 34IM needs to be installed in the aircraft hydraulic system 12. Note that leak location can utilize existing isolation devices 34, such as valves 36. In some embodiments, new isolation devices 34 are introduced into the hydraulic system 12 to provide this function.

[0149] Reference Figure 2 and Figure 4, a preferred implementation of the procedure for external leak location ELL is as follows:

[0150] If an external leak is detected in S10 and S11, the positioning function starts.

[0151] S12, S13 control the isolation device 34 to isolate the downstream distribution pipeline. In some embodiments, when multiple isolation devices 34 are available, the positioning test uses the isolation device farthest from the HePP 24 in the downstream direction, such as Figure 2 The valve 36.1 in is started. Thus, the downstream part 50.1 of the hydraulic system 12 is isolated from the upstream part 50.2 of the hydraulic system 12.

[0152] S14, S15 pressurize the hydraulic system 12. In some embodiments, this is similar to the above and Figure 3 Steps S4 , S5 of the procedure for external leakage detection ELD shown in proceed analogously, with different implementation options a., b. and c..

[0153] S16, S17 monitor the reservoir level, hydraulic system pressure and HePP output power for external leak indication. In some embodiments, this is similar to the above and Figure 3 Steps S6 , S7 of the procedure for the external leakage detection ELD shown in proceed analogously, with different implementation options a., b. and c..

[0154] There are several possible leak detection results for S18:

[0155] i. S19 If no external leak is detected any more, the external leak is expected to be located downstream of the isolation, i.e. in the downstream portion 50.1 of the hydraulic system 12. This information is provided to the maintenance personnel MC. The distribution line - downstream portion 50.1 - remains isolated to prevent system loss due to external leaks.

[0156] ii. S20, S21 If an external leak is still detected, it is expected that the external leak is located upstream of the isolation device, i.e. in the upstream part 50.2 of the hydraulic system 12. As indicated in step S20, another isolation device 34 can be controlled to further refine the location (starting from S11 again). Figure 2 In the example of , the next valve 36.2 in the upstream direction can be closed to isolate the two parts of the preceding upstream part 50.2 of the hydraulic system 12 from each other, and

[0157] Repeat the procedure.

[0158] iii. S19, S20, S21 In the case where the leakage detection in steps S16, S17 and S18 results in a result in which the external leakage is reduced but still detected, it is expected that there are two (or more) external leaks. One external leak is assumed to be located downstream of the isolation device 34, i.e. in the downstream portion 50.1. This information is provided to the maintenance personnel MC. The distribution lines are kept isolated to prevent system losses caused by external leaks. The second external leak is expected to be located upstream of the isolation device, i.e. in the upstream portion 50.2 of the hydraulic system 12. As indicated in step S20, another isolation device 34 can be controlled to further refine the location of the second external leak (starting again from S11). In Figure 2 In the example of , the next valve 36 . 2 in the upstream direction may be closed to isolate the two parts of the preceding upstream part 50 . 2 of the hydraulic system 12 from each other, and the procedure is repeated.

[0159] In the most preferred embodiment, in addition to the on-ground function, the reservoir level also indicates external leaks during flight. If no significant consumer operation is being performed and the reservoir level is decreasing, an external leak can be expected and indicated. In some embodiments, the control and monitoring unit 22 of the hydraulic system 12 and / or also other systems or units, such as, for example, flight control, is used to determine the status of each consumer, such as the hydraulic drive unit 20. If no command is given, only internal leaks are expected at the consumer. If the RSVR level then decreases rapidly, an external leak is detected.

[0160] Similar to the positioning described above for services on the ground, positioning can also be performed in flight by using the isolation means IM34, 36, 36.1, 36.2, wherein instead of leak detection for ground conditions, an in-flight leak detection as mentioned above is performed.

[0161] All in all, the functions described above save costs and time and reduce the probability during maintenance. On the aircraft side, the weight of the equipment or the installation effort will not increase, because the detection function can be realized by means of software.

[0162] Reference numerals list

[0163] 10 Aircraft

[0164] 12. Hydraulic system

[0165] 14 Pumps

[0166] 16 Storage

[0167] 18Hydraulic transmission system

[0168] 20 Hydraulic drive unit

[0169] 22Control and monitoring unit

[0170] 24 Hydraulic Electric Power Pack

[0171] 25 Motor

[0172] 26 Fluid Level Sensor

[0173] 28 Pressure Sensor

[0174] 30 Power Sensor

[0175] 32 hydraulic lines

[0176] 34 Isolation Devices

[0177] 36, 36.1, 36.2 valves

[0178] 38 processors

[0179] 40 Memory

[0180] 42 communication pipeline

[0181] 44 Aircraft Control Unit

[0182] 46 Temperature Sensor

[0183] 48 Ground Cart

[0184] 50.1 Downstream part

[0185] 50.2 Upstream part

[0186] ELD External Leak Detection

[0187] MC Maintenance Staff

[0188] HePP Hydraulic Electric Power Pack

[0189] CMU control and monitoring unit

[0190] IM Isolation Devices

[0191] Y is

[0192] No

[0193] S1 triggers leak detection

[0194] S2 checks whether the test condition is met

[0195] S3 indicates that the test failed

[0196] S4 command pressurization

[0197] S5 pressurizes the hydraulic system

[0198] S6 sends sensor data (pressure, reservoir, level, power)

[0199] S7 monitors reservoir level, system pressure & power

[0200] S8 indicates the test was completed and no findings were found

[0201] S9 indicates external leakage

[0202] ELL External Leak Location

[0203] S10 Start: Leak detected

[0204] S11 starts positioning

[0205] S12 command isolation

[0206] S13 Isolate the hydraulic lines

[0207] S14 command pressurization

[0208] S15 pressurizes the hydraulic system

[0209] S16 sends sensor data (pressure, reservoir, level, power)

[0210] S17 monitors reservoir level, system pressure & power

[0211] S18 leak?

[0212] S19 indicates the isolation downstream of the isolation device

[0213] S20 Are other isolation devices available?

[0214] S21 indicates positioning upstream of the isolation device

Claims

1. A method for automatically testing a hydraulic system (12) of an aircraft (10) during ground service, wherein: The hydraulic system (12) comprises a hydraulic pump (14), a hydraulic reservoir (16), a hydraulic transmission system (18), a hydraulic drive unit (20) and a control and monitoring unit (22) onboard the aircraft (10), and the method comprises: a) pressurizing the hydraulic system (12) by means of the hydraulic pump (14), b) monitoring during said pressurization of said hydraulic system (12) at least one parameter indicative of an external leakage of said hydraulic system (12), c) determining whether an external leak of the hydraulic system (12) exists based on the at least one parameter.

2. The method according to claim 1, wherein: Before step a), at least one or more of the following steps are performed: aa) manually triggering the test procedure including steps a) to c), bb) automatically checks whether the pressurization condition of the hydraulic system is met, preferably so that step bb) includes at least one or more of the following steps: bb1) checking whether the aircraft (10) is on the ground, bb2) Check whether the temperature is within predetermined limits.

3. A method according to any one of the preceding claims, wherein: Step a) includes at least one or more of the following steps: a1) pressurizing the hydraulic system (12) to a predetermined level, a2) commanding the pump (14) to pressurize the system (12) by means of the control and monitoring unit (22), a3) keeping the hydraulic system (12) pressurized by controlling the pump (14) to compensate only for internal leaks, a4) shutting off the pump (14) when the hydraulic system (12) is pressurized, a5) keeping the hydraulic system (12) pressurized by controlling the pump (14) to maintain the pressure in the hydraulic system (12).

4. A method according to any one of the preceding claims, wherein: The parameter to be monitored in step b) is selected from the group of parameters comprising the pressure in the hydraulic system (12), the output power of the pump (14) and the fluid level in the reservoir (16).

5. The method according to claim 3 and claim 4, wherein: 5.1 In the case of step a3), an external leak is determined when: detecting that the pressure in the hydraulic system (12) decreases over time, or Detecting a decrease in the reservoir liquid level over time; 5.2 In the case of step a4), an external leak is determined when: a decrease in the pressure in the hydraulic system (12) over time is detected, the decrease being different from, i.e., faster than, a decrease in pressure due to an internal leak, or · detecting a decrease in the reservoir liquid level over time; or 5.3 In the case of performing step a5), when the output power of the pump (14) increases, external leakage is determined.

6. A method for automatically testing a hydraulic system (12) of an aircraft (10), wherein: The hydraulic system (12) comprises a hydraulic pump (14), a hydraulic reservoir (16), a hydraulic transmission system (18), a hydraulic drive unit (20) and a control and monitoring unit (22) onboard the aircraft (10), and the method comprises: The method according to any of the preceding claims is performed during ground service and the following steps are performed in flight: 6b) monitoring at least one parameter indicative of an external leakage of the hydraulic system (12), and 6c) Determining whether an external leak of the hydraulic system (12) exists based on the at least one parameter.

7. A method according to any one of the preceding claims, wherein: The hydraulic system (12) comprises an isolation device (34) configured to isolate a plurality of parts (50.1, 50.2) of the hydraulic system (12) from each other, wherein the method further comprises the following steps: d) In the case where an external leakage is determined in step c) or 6c), the external leakage is located by isolating the parts (50.1, 50.2) of the hydraulic system (12) using the isolation device (34) and performing steps a) to c) or steps 6b) and 6c) on one, multiple or all of the isolated parts (50.1, 50.2) to determine in which part of the parts (50.1, 50.2) the external leakage occurs.

8. The method according to claim 7, wherein: Step d) comprises the following steps: d1) isolating the hydraulic system (12) into a first part (50.2) located upstream of the isolating device (34) and a second part (50.1) located downstream of the isolating device (34), d2) performing steps a) to c) or steps 6b) and 6c) on the first part (50.1), and i. locating the external leak downstream of the isolation device (34) when the external leak is no longer detected, ii. locating the external leak upstream of the isolation device (34) if the external leak is still detected, and iii. In the event that the external leak is detected to be reduced in size, locating the external leak such that a first external leak is upstream of the isolation device (34) and a second external leak is downstream of the isolation device (34).

9. The method according to claim 8, wherein: In case i. or iii., the second portion (50.1) remains isolated to prevent system losses due to external leakage.

10. The method according to any one of claims 7 to 9, wherein: Other isolation devices (36.2, 34) are used to further refine the positioning.

11. A control and monitoring unit (22) for a hydraulic system (12) of an aircraft (10), the control and monitoring unit (22) being configured to control and monitor the hydraulic system (12) to perform the steps of the method according to any of the preceding claims.

12. A hydraulic system (12) for an aircraft (10), the hydraulic system (12) comprising: A pump (14); a hydraulic reservoir (16); a hydraulic transmission system (18); a hydraulic drive unit (20); at least one sensor (26, 28, 30) for a parameter of the hydraulic system (12) indicating an external leakage; and a control and monitoring unit (22), wherein the control and monitoring unit (22) is configured to control the hydraulic system (12) to perform the steps of the method according to any one of claims 1 to 10.

13. The hydraulic system (12) according to claim 12, wherein: The control and monitoring unit (22) is also configured to monitor at least one of the parameters during flight to determine external leaks of the hydraulic system (12).

14. An aircraft (10) comprising a hydraulic system (12) according to claim 12 or 13 and / or a control and monitoring unit (22) according to claim 11.

15. A computer program comprising instructions for causing a hydraulic system (12) according to claim 12 or 13 to perform the steps of the method according to any one of claims 1 to 10.

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