WATER SUPPLY AND DISTRIBUTION SYSTEM ON-BOARD AN AIRCRAFT AND METHOD FOR OPERATING SUCH SYSTEM

A method for operating an on-board water supply and distribution system of an aircraft for supplying water includes a central water tank, central pump, having an upstream side and a downstream side for conveying and pressurizing water from the upstream side to the downstream side, consumer assemblies including a supply device and a buffer tank including a pressurizing device. A high-pressure conduit system connects the downstream side with the consumer assemblies and is configured where the central pump operating can deliver water from the downstream side to the buffer tank of each of the consumer assemblies. The method includes operating the central pump where water is pressurized to a first pressure, monitoring pressure in the high-pressure conduit system for a first period of time, and providing a first failure signal when pressure in the high-pressure conduit system drops below a second pressure within the first period of time.

TECHNICAL FIELD

The disclosure herein is directed to a method for operating a water supply and distribution system on-board an aircraft. The disclosure herein is further directed to a water supply and distribution system for an aircraft.

BACKGROUND

Conventional water supply and distribution systems on-board commercial aircraft comprise pipework made from rigid pipes, i.e., rigid plumbing. Through the rigid pipes potable water is supplied from a central water tank towards consumer assemblies such as sinks and toilets in a lavatory or steam ovens and sinks in a galley.

However, recently a high-pressure water system was introduced, and it is described in EP 3 385 361 A1. Such industry-optimized water system architecture is based on the concept of a reduction of pipe cross-sections accompanied by an increase in pressure level as well as a change of pressurization technology, i.e., rather than employing pressurized central water tanks, displacement pumps are used, but other types of pumps may also be used in such high-pressure systems. With such pumps water in a so-called high-pressure conduit system downstream the pump is pressurized and conveyed at such increased pressures. This adaption allows massive savings, e.g., weight, installation time, equipment cost etc.

In any kind of water supply system but especially in case of those pressurized systems there is the risk that due to leaks in the monuments and the high-pressure conduit system large amounts water may escape into areas of the aircraft such as spaces behind claddings or below floor elements where the components of the conduit system are installed, where even large amounts or accumulations of water cannot be discovered without disassembling claddings or floor components. Similarly, visual inspection of the high-pressure conduit system and the components of it in monuments also require the disassembly of the floor or the cladding members which in turn requires a lot of efforts.

Furthermore, leaking water can, for example, damage sensitive electronic equipment which is especially critical regarding safety when the avionics bay is affected, because this area houses the flight control computers. In addition, large amounts of water mean a lot of weight, which can have a safety-relevance since it results in a shift in the center of gravity of the entire aircraft. Especially, in permanent cold-weather operation, when the drainage openings in the aircraft fuselage cannot drain the leaking water, an ice shell can form in the aircraft bilge over several legs, which can have a mass of several hundred kilograms.

SUMMARY

Hence, it is an object of the disclosure herein to provide for monitoring the integrity of the water supply system during operation without the need to disassemble components of the interior of the aircraft.

The aforementioned object underlying the disclosure herein is solved by a method for operating an on-board water supply and distribution system of an aircraft for supplying water, the system comprising a central water tank, a central pump, having an upstream side and a downstream side and being capable of conveying and pressurizing water from the upstream side to the downstream side, a plurality of consumer assemblies, each consumer assembly comprising a supply device, such as faucets, toilet rinse valves, coffee machines, steam ovens in galley etc., and a buffer tank, wherein the buffer tank of each of the consumer assemblies comprises a pressurizing device configured for applying a consumer pressure to the water kept in the buffer tank, and each consumer assembly being configured to supply water from the buffer tank via the supply device, and a high-pressure conduit system, wherein the central water tank is connected to the upstream side, wherein the high-pressure conduit system connects the downstream side with the plurality of consumer assemblies, with the high-pressure conduit system being configured such that the central pump, when operating is capable of delivering water from the downstream side to the buffer tank of each of the consumer assemblies, the method comprising the following steps:operating the central pump such that water in the high-pressure conduit system is pressurized to a predetermined first pressure;monitoring the pressure in the high-pressure conduit system for a predetermined first period of time; andproviding a first failure signal when the pressure in the high-pressure conduit system drops below a predetermined second pressure within the first period of time.

Thus, the method of the disclosure herein is performed with a pressurized on-board water supply and distribution system comprising a central water tank, a central pump and a plurality of consumer assemblies comprising a buffer tank and a supply device.

Here, it is to be noted that it is preferred that either the central pump is provided with a backflow prevention mechanism, which prevents water and/or a gas to flow in an opposite direction from the downstream side to the upstream side when it is not operated, or an additional backflow prevention valve is provided which is closed, when the central pump is not operated and prevents water and/or a gas to flow from the downstream side to the upstream side.

Moreover, each of the buffer tanks is provided with a pressurization device configured for applying a consumer pressure to the water kept in the buffer tank. The pressurizing device allows to pressurize the water in the buffer tanks, so that the pressure level, the water in the buffer tanks has, is the aforementioned consumer pressure. The buffer tank with the pressurizing device may be configured such that the tank may hold both the water and a gas. In particular, the buffer tank may for example comprise a membrane that separates the inner volume of the buffer tank into two parts. Firstly, a receiving space is formed for receiving the water being supplied via the high-pressure conduit system. In addition, a gas volume is formed, that hold the gas which is compressed when the receiving space is filled with water, so that it acts as an elastic member that in turn pressurizes the water.

However, it is also conceivable that the buffer tank and/or the gas volume is coupled to a compressor that is controlled such that it pressurizes the gas volume to a predetermined pressure corresponding to the consumer pressure and also maintains this pressure.

When employing a compressor, it is not necessary, that the membrane is provided, which separates the inner volume of the buffer tank. In such case, the membrane may be omitted.

In addition to the above approaches, metallic or plastic bellows may be employed as passive pressurization devices. Alternatively, a spring-loaded piston applying pressure onto a volume connected to the space in the buffer tank receiving the water may also be employed. Moreover, such piston may also be loaded by a linear actuator, which is controlled in a corresponding manner.

Furthermore, other approaches to apply the consumer pressure to the water that is kept in the buffer tank are also conceivable, and the disclosure herein is not limited to the afore-mentioned examples.

Further, the consumer assemblies and especially its buffer tanks are connected with the central pump via the high-pressure conduit system.

It is also to be noted that the system in addition to the above-described consumer assemblies comprising pressurized buffer tanks may include further consumer assemblies that do not have buffer tanks being the pressurized or even buffer tanks at all. Hence, it is within the scope of the disclosure herein that the water supply system may comprise additional components not mentioned before. However, it is essential, that a plurality of consumer assemblies is provided having pressurized buffers tanks as described above.

In this respect, it is further to be noted that in a preferred embodiment the high-pressure conduit system comprises a pressure reservoir that is configured such that it applies a pressure at a reservoir pressure to the high-pressure conduit system after the operation of the central pump has been stopped with the reservoir pressure and the pressure in the high-pressure conduit system at that point in time where the central pump was stopped being the same. Such pressure reservoir may be in the form of a tank containing a gas volume and an elastic membrane that separates the gas volume from a further volume being connected to the high-pressure conduit system and receiving water and/or gas such as ambient air from the conduit system, i.e., the reservoir is configured in a similar form as the tank in conventional compressors. However, other configurations are conceivable as well. A component of the high-pressure conduit system having compressibility such the aforementioned pressure reservoir can also be generated by providing shape elasticity of a hose element of the high-pressure conduit system or other compressible elements with spring properties may be integrated into the high-pressure conduit system.

With the method of the disclosure herein is a first step that the central pump is operated such that the water in the high-pressure conduit system is pressurized to a predetermined first pressure.

In a preferred embodiment at least after this first pressure or a pressure level has been reached, the consumer assemblies are operated such that in each of the consumer assemblies the connection between the buffer tank of the consumer assembly and the high-pressure conduit system is brought in a closed position.

In parallel the pressure in the high-pressure conduit system is monitored for a first period of time. In case the pressure in the high-pressure conduit system drops below a predetermined second pressure within this first period of time, a first failure signal is provided. The provision of a failure signal may be in such a form that a control unit of the on-board water supply and distribution system generates such first failure signal which is then further provided to the aircraft data network of the aircraft in which the entire system is installed. In particular, due to the first failure signal a specific failure message may be displayed on control panels such as the flight attendant panel and/or the first failure signal will cause that the central pump of the water supply and distribution system will automatically be switched off.

In case the pressure in the high-pressure conduit system does not drop below the predetermined second pressure but stays above, in a preferred embodiment a test-passed signal will be generated by the control unit which signal may cause that a corresponding message will be displayed on the aforementioned panels. It is further preferred that this information is also stored onboard in the aircraft data base. This offers evidence for the maintenance staff when the system was tested successfully and when the system started to have a water leakage.

When performing the test as specified by the method of the disclosure herein, a drop of the water pressure in the high-pressure conduit system below the predetermined second pressure indicates that there is a leak in the high-pressure conduit system, i.e., with this procedure it can simply be determined whether there is a leak in the high-pressure conduit system. Water cannot escape from the high-pressure conduit system except there is a leak, so that in case the entire system is properly working, the water pressure in the system should remain constant above a certain level after an equilibrium level has been reached.

Thus, the method of the disclosure herein allows for quickly obtaining general information about the status of the water supply and distribution system without the need to disassembly components of a cladding or floor and to visually inspect the system.

In a preferred embodiment of the method of the disclosure herein, the consumer assemblies are operated such that for each of the consumer assemblies the connection between the buffer tank of the consumer assembly and the high-pressure conduit system is in an open position, wherein the pressures are monitored in the buffer tanks of each of the consumer assemblies after a second period of time and wherein a second failure signal is provided, when the difference between the monitored pressures in the buffer tanks of two consumer assemblies exceeds a first pressure difference.

Hence, in this preferred embodiment it is monitored, whether, when the connections between the buffer tanks and the high-pressure conduit system are in an open position for each of the consumer assemblies, the same pressure is reached after an equalization period. Should this not be the case, this indicates that the entire system is not running properly, i.e., certain sensors are not correctly working, which would be indicated by the second failure signal transmitted by the aircraft data network. In case identical pressure values are obtained, it is conceivable that a test-passed signal will be transmitted.

In another preferred embodiment the consumer assemblies are operated such that for each of the consumer assemblies the connection between the buffer tank of the consumer assembly and the high-pressure conduit system is in an open position, wherein the pressures are monitored in the buffer tanks of each of the consumer assemblies and in the high-pressure conduit system after a second period of time and wherein a second failure signal is provided, when the difference between the monitored pressure in the buffer tank of one of the consumer assemblies and the monitored pressure in the high-pressure conduit system exceeds a first pressure difference.

In this preferred embodiment it is monitored, whether when the connections between the buffer tanks and the high-pressure conduit system are in an open position for each of the consumer assemblies, that the same pressure is reached in the buffer tanks and the high-pressure conduit system after an equalization period. Should this not be the case, it also indicates that sensors are malfunctioning or that a leak is present.

In a further preferred embodiment of the method of the disclosure herein, the consumer assemblies are operated such that for the consumer assemblies the connections between the buffer tank and the high-pressure conduit system are subsequently brought in the open position so that at one point in time for only one of the consumer assemblies the connection between the buffer tank of the consumer assembly and the high-pressure conduit system is in an open position, whereas for the remaining consumer assemblies the connection between the buffer tank of the consumer assembly and the high-pressure conduit system is in a closed position, wherein for each of the consumer assemblies when the connection between the buffer tank and the high-pressure conduit system is in the open position, the pressure in the high-pressure conduit system is monitored for the predetermined first period of time, and wherein the first failure signal is provided, when for at least one of the consumer assemblies, the pressure in the high-pressure conduit system drops below the predetermined second pressure within the first period of time.

In this preferred embodiment of the method of the disclosure herein the connection between the central pump and the buffer tank of each of the consumer assemblies is subsequently checked. This allows to determine whether any of the paths between the central pump and the buffer tanks comprises a leak, which is indicated when the pressure which is monitored in the high-pressure conduit system or the buffer tank currently coupled with the high-pressure conduit system, drops below the second pressure within the first period of time.

In a further preferred embodiment, the first failure signal is provided, when for at least one of the consumer assemblies, the pressure in the high-pressure conduit system and in the buffer tank of that consumer assembly currently connected to the high-pressure conduit system differ by more than a second pressure difference after the first period of time. This allows to double check the pressure sensors in the high-pressure conduit system and the respective buffer tank. If the monitored pressures do not sufficiently match the first failure signal is provided.

Further, it can be distinguished between a sensor malfunction and a leak by monitoring the pressure by sensors at different positions after a predetermined time interval. When each of the sensors also indicate a lower pressure after the time interval, there must be a leak since they are fluidly connected. If the difference is still present after the interval, then a sensor error or malfunctioning must be the root cause.

In another preferred embodiment, the method of the disclosure herein comprises the following steps:pressurizing gas, preferably ambient air, in the high-pressure conduit system to a predetermined third pressure, preferably by the central pump;monitoring the pressure in the high-pressure conduit system for a predetermined third period of time; andproviding a third failure signal when the pressure in the high-pressure conduit system drops below a predetermined fourth pressure within the third period of time.

With this preferred embodiment the high-pressure conduit system, especially when in a preferred embodiment the connections between the buffer tank of the consumer assemblies and the high-pressure conduit system are in the closed position, can be checked as to whether it comprises a leak without having water in the system but performing in the test with gas such as ambient air as the medium in question. In this regard it is to be noted that the high-pressure conduit system as well as the central tank need to be drained.

Furthermore, it is to be noted that means other than the central pump may by employed as the source for pressurized gas. In particular, it is conceivable that a ground pressure source is used or that the high-pressure conduit system is configured such that it comprises an interface which can connected to an interface of the cabin pressurization system or, as an alternative, it may also be connected to an interface of the bleed air system.

In another preferred embodiment the consumer assemblies are operated such that for each of the consumer assemblies the connection between the buffer tank of the consumer assembly and the high-pressure conduit system is in an open position, wherein the pressures are monitored in the buffer tanks of each of the consumer assemblies after a fourth period of time, and wherein a fourth failure signal is provided, when the difference between the monitored pressures in the buffer tanks of two consumer assemblies exceeds a third pressure difference. With this preferred embodiment it is monitored, whether for each of the consumer assemblies, when the connections between the buffer tanks and the high-pressure conduit system are in an open position, the same gas pressure is reached after an equalization period. Should this not be the case, this indicates that the entire system is not running properly, i.e., certain sensors are not correctly working, which would be indicated by the fourth failure signal transmitted by the aircraft data network. In case an identical pressure values are obtained, it is conceivable that a test-passed signal will be transmitted.

In another preferred embodiment the consumer assemblies are operated such that for each of the consumer assemblies the connection between the buffer tank of the consumer assembly and the high-pressure conduit system is in an open position, wherein the pressures are monitored in the buffer tanks of each of the consumer assemblies and in the high-pressure conduit system after a fourth period of time and wherein a fourth failure signal is provided, when the difference between the monitored pressure in the buffer tank of one of the consumer assemblies and the monitored pressure in the high-pressure conduit system exceeds a fourth pressure difference.

In this preferred embodiment it is monitored, whether when the connections between the buffer tanks and the high-pressure conduit system are in an open position for each of the consumer assemblies, that the same gas pressure is reached in the buffer tanks and the high-pressure conduit system after an equalization period. Should this not be the case, it also indicates that sensors are malfunctioning or that a leak is present.

As an alternative to the aforementioned preferred embodiment, where the connections between the buffer tanks and the high-pressure conduit system are closed, it is also preferred that the consumer assemblies are operated such that for the consumer assemblies the connection between the buffer tank and the high-pressure conduit system are subsequently brought in the open position so that at one point in time for only one of the consumer assemblies the connection between the buffer tank of the consumer assembly and the high-pressure conduit system is in an open position, whereas for the remaining consumer assemblies the connection between the buffer tank of the consumer assembly and the high-pressure conduit system is in a closed position, wherein for each of the consumer assemblies, when the connection between the buffer tank and the high-pressure conduit system is in the open position, the pressure in the high-pressure conduit system is monitored for the predetermined third period of time, and wherein the third failure signal is provided, when for at least one of consumer assemblies, the pressure in the high-pressure conduit system or in the buffer tank of the at least one consumer assembly drops below the predetermined fourth pressure within the third period of time.

Hence, in this preferred embodiment the different paths from the central pump to each of the buffer tanks of the consumer assemblies are inspected as to whether a leak is present in the respective path. If the latter is the case, the gas pressure in the system will drop below the fourth pressure within the third period of time and a third failure signal will be provided and transmitted via the aircraft data network. In the alternative, in case no significant pressure drop occurs in the third period of time, again a test-passed signal may be provided.

In a further preferred embodiment, the third failure signal is provided, when for at least one of the consumer assemblies, the pressure in the high-pressure conduit system and in the buffer tank of that consumer assembly currently connected to the high-pressure conduit system differ by more than a predetermined pressure difference after the third period of time. This again allows to double check the pressure sensors in the high-pressure conduit system and the respective buffer tank. If the monitored pressures do not sufficiently match the third failure signal is provided.

In another preferred embodiment the method of the disclosure herein comprises the following steps:operating the central pump such that water is conveyed from the upstream side to the downstream side, into the high-pressure conduit system and into the buffer tank of at least one of the consumer assemblies;operating the at least one consumer assembly such that the connection between the buffer tank of the at least one consumer assembly and the high-pressure conduit system is brought in a closed position, wherein the water in the buffer tank of the at least one consumer assembly is kept at the consumer pressure by the pressurizing device;monitoring the pressure in the buffer tank of the at least one consumer assembly while the supply device of the at least one consumer assembly is kept in a closed position; andproviding a fourth failure signal when the pressure in the buffer tank of the at least one consumer assembly drops below a predetermined fifth pressure below the consumer pressure within a fourth period of time.

In this preferred embodiment it is monitored whether the pressure in the buffer tank of at least one of the consumer assemblies is maintained and whether the pressure does not drop below the predetermined fifth pressure. In case the letter occurs, a fourth failure signal will be generated and transmitted which then indicates that the consumer assembly being provided with the buffer tank in question obviously comprises a leak. As a consequence, the respective monument having the consumer assemblies with the leak may be disconnected from the system by permanently closing the connection between the respective consumer assembly and the high-pressure conduit system. Similarly, as in the aforementioned embodiments, in case no significant pressure drop is detected in the fourth period of time, a test-passed signal may be provided and transmitted to the control unit via the aircraft data network.

In another preferred embodiment of the disclosure herein, the pressurizing devices of the consumer assemblies are further configured for increasing a pressure of the water in the buffer tanks to an operating pressure and the pressure of the water at the operating pressure when water is or has been drained from the buffer tank, wherein the method further comprises the following steps:operating at least one consumer assembly for a predetermined time interval such that the pressurising device of the at least one consumer assembly increases the pressure in the buffer tank of the at least one consumer assembly towards the operating pressure, while the supply device of the at least one consumer assembly is in the closed position, and that the connection between the buffer tank of the at least one consumer assembly and the high-pressure conduit system is in the closed position;monitoring the pressure in the buffer tank of the at least on consumer assembly after expiry of the time interval; andproviding a fifth failure signal when the pressure in buffer tank of the at least one consumer assembly is below the operating pressure after expiry of a fifth period of time by more than a predetermined value.

In this preferred embodiment the pressurizing device is configured such that it is capable of increasing the pressure of the water in the buffer tanks to an operating pressure. In such case this preferred embodiment at least one of the consumer assemblies is operated such that the pressure of the water in its buffer tank is increased to the operating pressure for a predetermined period of time. After the pressurizing device has been switched off, the pressure in the buffer tank is monitored and in case it drops below the operating pressure by more than a threshold, namely by more than the predetermined value, a fifth failure signal will be sent through the aircraft data network. In case such drop does not occur, a test-passed signal may be generated.

In another preferred embodiment, the method of the disclosure herein further comprises the following steps:operating the central pump such that water is conveyed from the upstream side to the downstream side, into the high-pressure conduit system and into the buffer tank of at least one of the consumer assemblies;monitoring whether the level in the buffer tank of the at least one consumer assembly exceeds a predetermined second filling level;stopping operation of the central pump or closing the connection between the at least one consumer assembly and the high-pressure conduit system, when the level in the buffer tank of the at least one consumer assembly has exceeded the predetermined second filling level;monitoring whether the level in the buffer tank (41) of the at least one of the consumer assembly falls below a predetermined second filling level; andproviding a seventh failure signal when the level in the buffer tank (41) of the at least one the consumer assembly (5) has fallen below the predetermined second filling level within a predetermined seventh period of time.

In this preferred embodiment the buffer tank of one of the consumer assemblies is initially filled up to a predetermined first filling level, and when this level has been reached, the central pump is switched off or the connection between the at least one consumer assembly and the high-pressure conduit system is closed, e.g., by closing an inlet valve, i.e., preferably an inlet valve connecting the buffer tank of this consumer assembly and the high-pressure conduit system, and the respective supply device is closed, when the first predetermined filling level has been reached. In the following, the level in the buffer tank is monitored, and when the level in the respective buffer tank falls below a predetermined second filling level, a seventh failure signal is provided to the aircraft data network and treated correspondingly. The seventh failure signal is generated because a decrease of the level in one of the buffer tanks even though the supply device and the inlet valve are closed, indicates that the respective consumer assembly is malfunctioning and comprises a leak. In addition, in case the level in the buffer tank stays above the second filling level within the seventh period of time, again a test-passed signal may be generated and transmitted via the aircraft data network.

With regard to the disclosure herein and the preferred embodiments explained above it is to be noted that although some embodiments are merely described as being preferred, they are to be considered as a disclosure herein even when taken in isolation.

DETAILED DESCRIPTION

As can be taken fromFIGS.1and2the example embodiment of a water supply and distribution system1is generally arranged on-board an aircraft3and configured such that it supplies a plurality of consumer assemblies5which comprise supply devices7such as sinks and toilets in a lavatory or steam ovens and sinks in a galley, with potable water as will be described in detail below.FIG.1only schematically shows the arrangement of the system1in the aircraft3, and several types of arrangements are conceivable.

The water supply and distribution system1comprises a central water tank9which is provided with a connector11at its bottom. The connector11is connected to a supply line13which extends to a fill/drain coupling15with a valve17being arranged in the supply line13adjacent to the fill/drain coupling15. The valve17is connected to a control unit19of the system1and can remotely be controlled such that it can be switched between a closed and an open position. As can further be taken fromFIG.1, the supply line13also connects the connector11with a central pump21. Preferably, the central pump21is configured as a positive displacement pump and further preferred as a gear pump.

Furthermore, the central pump21is also connected to the control unit19and can be operated in a supply mode where it conveys and pressurizes water or other media such as ambient air from its upstream side23and the supply line13to its downstream side25that is connected to a high-pressure conduit system27which will be described in detail below. The downstream side25of the central pump21is equipped with a flow sensor29and a pressure sensor31which are both connected with the control unit19and which are capable of monitoring the flow rate of the water conveyed by the central pump21and the pressure the water supplied by the pump21has.

In addition, it is to be noted that it is preferred that either the central pump21is provided with a backflow prevention mechanism (not shown), which prevents water and/or a gas to flow in an opposite direction from the downstream side25to the upstream side23when the pump21is not operated, or an additional backflow prevention valve (not shown) is provided which is closed, when the central pump21is not operated and prevents water and/or a gas to flow from the downstream side25to the upstream side23.

The high-pressure conduit system27comprises a plurality of conduits connecting the downstream side25of the central pump21with the consumer assemblies5. In addition, in this preferred embodiment, the high-pressure conduit system27comprises a pressure reservoir33that is configured such that that it applies a pressure at a reservoir pressure level to the high-pressure conduit system27. The reservoir pressure level being the level the pressure has after operation of the central pump21has been stopped so that the reservoir pressure level is the level the pressure in the high-pressure conduit system27has at that point in time where the central pump21was stopped. The pressure reservoir33can be in the form of a tank containing a gas volume and an elastic membrane that separates the gas volume from a further volume being connected to the high-pressure conduit system and receiving water and/or gas such as ambient air from the conduit system, i.e., the pressure reservoir33can be configured in a similar form as in conventional compressors.

The consumer assembly5shown inFIG.3is configured as a lavatory with a sink35provided with a faucet37and a toilet39as supply devices7. Here, it is to be noted that other forms of consumer assemblies are conceivable such as galleys having sinks etc. and that the disclosure herein is not limited to consumer assemblies in the form of lavatories. In particular, since galleys are provided with buffer tanks that have a larger capacity than those of lavatories, the buffer tanks of galleys may play a more important role in the method of the disclosure herein, as will become clear below.

Furthermore, the consumer assembly5comprises a buffer tank41having an inlet43and an outlet45, the inlet43being provided with an inlet valve47which is connected to a control device49which in turn is connected to the control unit19so that each of the consumer assemblies5can be controlled by and can send signals the control unit19.

The position of the inlet valve47can be controlled by the control device49. The outlet45is connected to the faucet33and the toilet39. As can further be taken fromFIG.3, the line connecting buffer tank41with the toilet39is provided with a valve53that is controlled by the control device49. Similarly, the line connecting the buffer tank41with the faucet37is also provided with a valve55connected to and controlled by the control device49.

The buffer tank41of each consumer assembly5is provided with a level sensor57which is connected to the control device49and, hence, also to the control unit19. The level sensor57is configured such that it provides a signal to the control device49indicating the fill level in the buffer tank41. Furthermore, the buffer tanks41comprise an overpressure relief valve58which prevents that the pressure inside the buffer tanks41exceeds a maximum pressure which could cause damage to both the buffer tanks41and the conduit system attached to them.

The central tank9is also provided with a level sensor59that is connected to the control unit19so that the filling level in the central tank9can also electronically be determined by the control unit19.

Moreover, in this preferred embodiment the buffer tank41of each of the consumer assemblies5is configured for holding both a gas and the water. In addition, a pressurizing device61is provided on the buffer tank41and further configured for increasing a pressure of the gas in the gas volume63of the buffer tank41to an operating pressure or maintaining the pressure of the gas in the gas volume63at the operating pressure when water is or has been drained from the water volume65. Thus, the pressurizing device61is configured for applying a consumer pressure to the water kept in the buffer tank41. In this regard it is to be noted that pressurizing devices61is provided with an intake conduit66so that fresh air from an uncontaminated area may be sucked in.

So, the pressure of water in the water volume65is kept at or increased to a consumer pressure. In particular, between the gas volume63and the water volume65a flexible membrane or other separation element (not shown) may be provided. The pressurizing device61can be in the form of a compressor, that is controlled by the control device49which in turn is coupled to a pressure sensor67. The sensor67may by arranged in the water volume65, as shown inFIG.3, or in the gas volume63above the water level. Other configurations of the pressurizing device61are conceivable, as already indicated above.

Finally, the inlet43of the buffer tank41of each of the consumer assemblies5is connected to the downstream side25of the central pump21via the high-pressure conduit system27and the inlet valve47, so that the buffer tanks41can be supplied with water by the central pump21.

The control unit19of the system1in combination with the control device49of each of the consumer assemblies5are configured such that they operate the system1and especially the central pump21in this example embodiment in the following manner:

During normal operation the central pump21is constantly or intermittently operated in a supply mode so that water from the central tank9is delivered to the consumer assemblies5and their buffer tanks41, which are connected to the downstream side25of the pump21via the high-pressure conduit system27, so that the buffer tanks41of the consumer assemblies5are filled. In particular, in this step the inlet valves47of those consumer assemblies5, the buffer tanks41of which shall be filled, are at the same time or subsequently brought into its open position. The level in the buffer tanks41may be monitored by the level sensors57. Further, the water may be supplied from the buffer tank41to the faucet37or the toilet39by opening the respective valves53,55. In particular, the respective valve53,55are opened and a passive pressurization element such as a membrane expands to maintain the pressure onto the water in the buffer tank41. Alternatively, when the respective valve53,55is opened, an active pressurization device61, e.g., a compressor, a linear actuator acting on a piston, etc., is triggered via a signal from the pressure sensor67or the level sensor57on the buffer tank41so as to achieve that the pressure in the buffer tank41is maintained.

In addition, to ensure that the above described system is properly operating and no leaks or blockages are present in the entire system or at least that such leaks or blockages are detected at an early stage, the following safety procedures may be performed by the control unit19and the control devices49of the consumer assemblies5when starting the aircraft or during operation, with the control unit19and the control devices49being configured correspondingly:

Pressurizing gas, preferably ambient air, in the high-pressure conduit system27to a predetermined pressure, preferably by operating the central pump21such that the gas drawn in, e.g., via the fill drain coupling15or via an overflow line in the central water tank9, and supplied to the high-pressure conduit system27is pressurized to a predetermined pressure monitored by the control unit19via the pressure sensor31;monitoring the pressure in the high-pressure conduit system7with the pressure sensor31for a predetermined period of time;providing a corresponding failure signal by the control unit19to the aircraft data network ADN of the aircraft3when the pressure in the high-pressure conduit system27drops below a predetermined pressure within the period of time. In particular, a test-passed signal may be transmitted in case the pressure does not drop below the predetermined pressure within the period of time.

With this procedure it can simply be determined whether there is a leak in the high-pressure conduit system27without the high-pressure conduit system being filled with water.

In this procedure the connection between the buffer tank41of the consumer assembly5and the high-pressure conduit system27, i.e., the inlet valve47, may be in a closed position, i.e., the inlet valves47are switched to their closed position, after the water has been pressurized by the central pump21.

It is also possible that the consumer assemblies5are operated such that for each of the consumer assemblies5the connection between the buffer tank41and the high-pressure conduit system27, i.e., the inlet valve47is in an open position. The gas pressures are monitored in the buffer tanks41of each of the consumer assemblies5after a predetermined period of time and a failure signal is provided, when the difference between the monitored gas pressures in the buffer tanks41of two consumer assemblies5exceeds a predetermined pressure difference. Additionally, or as an alternative, a failure signal is provided, when the difference between the monitored gas pressure in the buffer tank41of one of the consumer assemblies5and the monitored gas pressure in the high-pressure conduit system27exceeds a predetermined pressure difference.

Alternatively, this procedure can also be performed such that for the consumer assemblies5the connection between the buffer tank41and the high-pressure conduit system27, i.e., the inlet valves47, are subsequently brought in the open position, so that at one point in time for only one of the consumer assemblies5the inlet valve47is in an open position, whereas for the remaining consumer assemblies5the inlet valve47is in a closed position.

For each of the consumer assemblies5when the inlet valve47is in the open position, the pressure in the high-pressure conduit system27is monitored for the above predetermined period of time, and the failure signal is provided, when for at least one of the consumer assemblies5, the pressure in the high-pressure conduit system27drops below the predetermined fourth pressure within the period of time.

Hence, with this specific procedure the different paths from the central pump21to each of the buffer tanks41of the consumer assemblies5are inspected as to whether a leak is present in the respective path. If the latter is the case, the gas pressure in the system will drop below the pressure within the period of time and a failure signal will be provided and transmitted via the aircraft data network ADN. In the alternative, in case no significant pressure drop occurs in the period of time, again a test-passed signal may be provided.

Monitoring the level in the central tank9, e.g., via the level sensor59, when the central pump21is not operated so that it does not convey water from the upstream side23to the downstream side25and preferably when the alignment of the aircraft is constant, i.e., when roll and pitch are constant; andproviding a corresponding failure signal by the control unit19when the level in the central water tank decreases by more than a predetermined amount within a predetermined period of time.

This procedure allows to determine whether the central tank9and the supply line13to the central pump21comprise any leakages. In case the level in the central tank21decreases by more than the predetermined amount, the corresponding failure signal is generated and supplied to the aircraft data network ADN.

Operating the central pump21by the control unit19such that water in the high-pressure conduit system27is pressurized to a predetermined pressure;monitoring the pressure in the high-pressure conduit system27for a predetermined period of time by the pressure sensor31; andproviding a corresponding failure signal by the control unit19to the aircraft data network ADN when the pressure in the high-pressure conduit system27drops below a predetermined pressure within the period of time.

With this procedure it can also simply be determined whether there is a leak in the high-pressure conduit system27. However, this test may also be performed during normal operation, because different from Procedure 1 it is not required that the high-pressure conduit system is filled with gas instead of water.

In this procedure the inlet valve47may be in a closed position, i.e., the inlet valves47are switched to their closed position, after the water has been pressurized by the central pump21.

It is also possible that the consumer assemblies5are operated such that for each of the consumer assemblies5the connection between the buffer tank41and the high-pressure conduit system27, i.e., the inlet valve47is in an open position. The pressures are monitored in the buffer tanks41of each of the consumer assemblies5after a predetermined period of time and a failure signal is provided, when the difference between the monitored pressures in the buffer tanks41of two consumer assemblies5exceeds a predetermined pressure difference. Additionally, or as an alternative, a failure signal is provided, when the difference between the monitored pressure in the buffer tank41of one of the consumer assemblies5and the monitored pressure in the high-pressure conduit system27exceeds a predetermined pressure difference. Alternatively, this procedure can be performed such that for the consumer assemblies5the connection between the buffer tank41and the high-pressure conduit system27, i.e., the inlet valves47, are subsequently brought in the open position, so that at one point in time for only one of the consumer assemblies5the inlet valve47is in an open position, whereas for the remaining consumer assemblies5the inlet valve47is in a closed position.

For each of the consumer assemblies5when the inlet valve47is in the open position, the water pressure in the high-pressure conduit system27is monitored for the above predetermined period of time. The failure signal is provided, when for at least one of consumer assemblies5, the pressure in the high-pressure conduit system27drops below the predetermined pressure within the period of time.

Therefore, the different paths from the central pump21to each of the buffer tanks41of the consumer assemblies5are inspected with this specific procedure as to whether a leak is present in the respective path. If the latter is the case, the water pressure in the system will drop below the pressure within the period of time and a failure signal will be provided and transmitted via the aircraft data network ADN. In the alternative, in case no significant pressure drop occurs in the period of time, again a test-passed signal may be provided.

With this procedure the paths from the central pump21to the respective buffer tanks41can be inspected during normal use of the system, since the medium that is employed is water, which is present in the system anyway.

Operating the central pump21such that water is conveyed from the upstream side23to the downstream side25, into the high-pressure conduit system27and into the buffer tank41of one of the consumer assemblies5;monitoring, e.g., by the control devices49and level sensor57or pressure sensor67, whether the level in the buffer tank41of the one of the consumer assemblies5increases by more than a predetermined first filling level difference via the level sensors57;providing a corresponding failure signal when the level in the buffer tank41of the one of the consumer assemblies5has not increased by the predetermined filling level difference within a predetermined period of time, preferably wherein the flow of water from the upstream side23to the downstream side25and into the high-pressure conduit system27is monitored by the control unit19and the flow sensor29so that the predetermined period of time is calculated by the control unit19based on the monitored flow of water from the upstream side23to the downstream side25and into the high-pressure conduit system27.

Firstly, this procedure allows to determine whether in at least one of the consumers assemblies5a leak is present. Further, this procedure generally allows, in combination with the simple embodiment of Procedures 1 or 3, i.e., where the inlet valves47are not subsequently opened, to determine in which path to the consumer assemblies5a leak is present when a failure signal was generated by Procedure 1 or 3. For this purpose, the procedure has to be carried out with the buffer tank41of each of the consumer assemblies5subsequently being filled until a failure signal is generated (see Procedure 6). In addition, if Procedures 1 or 2 do not identify a leak but in Procedure 4 the predetermined filling level difference is not achieved, a partial or total blockage can also be present upstream or downstream the central pump21.

Operating the central pump21by the control unit19such that water is conveyed from the upstream side23to the downstream side25, into the high-pressure conduit system27and into the buffer tank41of at least one of the consumer assemblies5;monitoring whether the level in the buffer tank41of the at least one of the consumer assemblies5increases by a predetermined filling level difference via the control device49and the level sensor57;stopping operation of the central pump21by the control unit19and preferably closing the inlet valve47, when the level in the buffer tank41of the at least one of the consumer assemblies5has increased by the predetermined filling level difference; further the valves53,55in the conduits to the supply devices37,39are also closed;monitoring whether the level in the buffer tank41of the at least one of the consumer assemblies5decreases by a predetermined filling level difference by the level sensor57and the control device49; andproviding a corresponding failure signal to the aircraft data network ADN by the control unit19when the level in the buffer tank41of the at least one of the consumer assemblies5has decreased by the predetermined filling level difference within a predetermined period of time.

This procedure allows to check whether there is any leakage in the monument comprising that consumer assembly5the level in the buffer tank41is monitored.

Operating the central pump21such that water is conveyed from the upstream side23to the downstream side25, into the high-pressure conduit system27and into the buffer tank41of each of the consumer assemblies5, wherein the buffer tanks41are subsequently filled such that at one point in time only one of the consumer assemblies5is supplied with water;monitoring whether the level in the buffer tank41of each of the consumer assemblies5increases by a predetermined filling level difference; andproviding a failure signal when for at least one of the consumer assemblies5the time between the start of the filling of its buffer tank41and of reaching the predetermined first filling level difference exceeds the predetermined period of time.

In order to determine the respective period of time the flow rate to the buffer tank41is required. Here, a nominal value of the central pump21may be the basis or the flow rate may be derived from the current pressure value in the high-pressure conduit system27. Finally, the signal of the flow sensor29arranged at the downstream side25of the central pump21may be used for this purpose.

When combined with Procedure 5, this procedure allows to check whether any blockages are in the path between the central pump21to the buffer tank41of each of the consumer assemblies5, because the respective test is conducted for each of the consumer assemblies5separately.

However, for confirming that a leak or blockage is present in that region it is additionally required that a certain minimum pressure of the pump21is reached. Otherwise, the pump21could also be damaged or it could have a leak.

Operating the central pump21by the control unit19such that water is conveyed from the upstream side23to the downstream side25and into the high-pressure conduit system27;monitoring the pressure in the high-pressure conduit system27for a predetermined period of time by the control unit19via the pressure sensor31; andproviding a corresponding failure signal by the control unit19to the aircraft data network ADN when the pressure in the high-pressure conduit system27remains below a predetermined pressure within the predetermined period of time.

When Procedures 5 and 6 have subsequently been conducted before and no failure signals were generated, i.e., no leaks and or blockages were detected downstream the central pump21, this procedure allows to check whether any blockages are present in the path between the central tank9and the central pump21and whether the pump21is operating properly.

Operating the central pump21by the control unit19such that water is conveyed from the upstream side23to the downstream side25and into the high-pressure conduit system27;monitoring the flow of water from the upstream side23to the downstream side25and into the high-pressure conduit system27with the inlet valves47of the buffer tanks41in an open position for a predetermined period of time by the control unit19and the flow sensor29;providing a corresponding failure signal by the control unit19to the aircraft data network ADN when the flow of water from the upstream side23to the downstream side25and into the high-pressure conduit system27remains below a predetermined flow level within the predetermined period of time.

Similar to Procedure 7a, this procedure also allows to check whether any blockages are present in the path between the central tank9and the central pump21, when combined with Procedure 6. In addition, it is monitored whether the pump21is operating in the right manner. Further it is to be noted, that the flow of water through the central pump21can be measured by the flow sensor29or inverse methods may also be used such as detecting the rotational speed of the central pump21to derive the flow if the pressure is measured by the pressure sensor31downstream the central pump21.

Operating the central pump21such that water is conveyed from the upstream side23to the downstream side25and into the high-pressure conduit system27;monitoring the flow of water from the upstream side23to the downstream side25and into the high-pressure conduit system27for a predetermined period of time;operating a first group of the consumer assemblies5such that the inlet valve47is open during the predetermined period of time, so that water is supplied to the buffer tank41of the consumer assemblies5of the first group;operating a second group of the consumer assemblies5such that water is supplied from the buffer tank41via the supply device7of the consumer assemblies5of the second group with the flow of supplied water through the supply device7being monitored during the predetermined period of time, e.g., by monitoring the level change in the respective buffer tank41, via operating parameters of the associated supply device7, with a flow sensor56associated to the supply device7or on the basis of a nominal flow value of the respective supply device7;monitoring the level in the buffer tanks41of the consumer assemblies5of the first and the second group of consumer assemblies during the predetermined period of time;determining from the change of the monitored level in the buffer tank41of the consumer assemblies5of the first and the second group of consumer assemblies5the total change of the amount of water received in the buffer tanks41of the consumer assemblies5in the predetermined period of time;determining by the control unit19from the monitored flow of water from the upstream side23to the downstream side25the total amount of water supplied by the central pump21to the consumer assemblies5in the predetermined period of time;determining from the monitored flow of supplied water from the buffer tanks41through the supply device of the consumer assemblies5of the second group of consumer assemblies5the amount of water supplied by the consumer assemblies5in the predetermined period of time; andproviding a failure signal when the change of the amount of water received in the buffer tanks41in the predetermined period of time differs from the total amount of water supplied by the central pump21minus the amount of water supplied by the second group of consumer assemblies5in the period of time by more than a predetermined value.

This procedure also allows to determine whether in the path between the central pump21and the supply device7of the one consumer assembly5leaks are present.

Operating the central pump21such that water is conveyed from the upstream side23to the downstream side25, into the high-pressure conduit system27and into the buffer tank41one of the consumer assemblies5;operating the consumer assembly5such that the connection between the buffer tank41and the high-pressure conduit system27, i.e., the inlet valve47, is brought in a closed position, wherein the water in the buffer tank41of the consumer assembly5is kept at the consumer pressure by the pressurizing device61; depending of the type of pressurization device61it needs to be activated first in order to maintain the pressure level in the buffer tank41;monitoring the pressure in the buffer tank41of the consumer assembly5while the supply device7of the consumer assembly5is kept in a closed position; andproviding a fourth failure signal when the pressure in the buffer tank41of the consumer assembly5drops below a predetermined pressure below the consumer pressure within a predetermined period of time.

With this preferred embodiment the buffer tank41is checked whether there is any kind of leakage. In addition, it is also checked whether the pressurization device61operates properly. If malfunctioning is detected a further failure signal will be generated and transmitted via the aircraft data network ADN. On the other hand, if the pressure drop is above the predetermined value, a test-passed signal may again be generated.

Therefore, with Procedure 9 it is possible to check whether buffer tanks41or the piping between the buffer tanks41and the respective supply device7have any leaks and whether the pressurization61are malfunctioning.

Operating the central pump21such that water in the high-pressure conduit system27is pressurized to a predetermined first pressure;operating the consumer assemblies5such that for each of the consumer assemblies5the connection between the buffer tank41of the consumer assembly5and the high-pressure conduit system27, i.e., the inlet valve47, is in an open position;monitoring the pressures in the buffer tanks41of each of the consumer assemblies5after a first predetermined period of time; andproviding a failure signal, when the difference between the monitored pressures in the buffer tanks41of two consumer assemblies5exceeds a first pressure difference.

This procedure allows again by making use of the pressurizing device61in the consumer assemblies5that maintain a pressure in the buffer tanks41and, due to the open inlet valves47, also in the high-pressure conduit system27, that it can be checked whether any of the consumer assemblies5or the high-pressure conduit system27comprises a leakage. However, it is required that the central pump21has a backflow prevention.

For this procedure the pressurizing devices61of the consumer assemblies5are configured for increasing a pressure of the water in the buffer tanks41to an operating pressure and maintaining the pressure of the water at the operating pressure when water is or has been drained from the buffer tank (41), e.g., the pressurizing devices are configured as compressors;Operating a consumer assembly5for a predetermined time interval such that the pressurising device61of the consumer assembly5increases the pressure in the buffer tank41towards the operating pressure, while the supply device7of the consumer assembly5is in the closed position, and that the connection between the buffer tank41and the high-pressure conduit system27, i.e., the inlet valve47, is in the closed position;monitoring the pressure in the buffer tank41of the consumer assembly5after expiry of the time interval; andproviding a failure signal when the pressure in buffer tank41is below the operating pressure after expiry of a further period of time after expiry of the time interval by more than a predetermined value.

Finally, this procedure allows by employing the pressurizing device61in the consumer assemblies5to check whether any of the consumer assemblies5comprises a leakage.

Pressurizing gas, such as ambient air, in a consumer assembly5in its line connecting the supply device7, such as the faucet37or the toilet39, to the high-pressure conduit system27; in particular, the gas may be pressurized by the pressurization device61of the consumer assembly5;monitoring the pressure in the line connecting the supply device7of the consumer assembly5to the buffer tank41, e.g. via the sensors67, for a predetermined period of time; andproviding a failure signal when the pressure in the line connecting the supply device7of the consumer assembly5to the buffer tank41drops below a predetermined pressure within the period of time.

With this procedure it can be tested, preferably when the valve53,55of the supply device7such as the toilet39or the faucet37are in a closed position, whether there is a leak in the conduits of the consumer assembly5. When it is detected that the gas pressure in the pressurized conduit drops below the predetermined threshold, a corresponding failure signal is generated and transmitted through the aircraft data network (ADN).

Operating the pressurization device61of a consumer assembly5such that water in the line connecting the buffer tank41and the supply device7, such as the faucet37or the toilet39, of the consumer assembly5is pressurized to a predetermined pressure;monitoring the pressure in the line connecting the buffer tank41and the supply device7of the consumer assembly5, e.g. via the sensor67for a predetermined period of time; andproviding a failure signal, e.g., via the aircraft data network ADN, when the pressure in the line connecting the buffer tank41and the supply device7of the consumer assembly5drops below a predetermined pressure within the period of time.

In this procedure the consumer assembly5in question is tested by pressurizing the water in the conduits whether there is a leak. In case a pressure drop is detected after the pressurization device61was switched off, this indicates the presence of a leak. In such case the corresponding failure signal is transmitted through the aircraft data network (ADN).

Operating the pressurization device61such that water is conveyed in the line connecting the supply device7of a consumer assembly5, such as the faucet37or the toilet39, to the high-pressure conduit system27or the buffer tank41;monitoring the pressure in the line connecting the supply device7of the consumer assembly5to the high-pressure conduit system27or the buffer tank41, e.g., via sensor56, for a predetermined period of time; andproviding a failure signal when the pressure in the line connecting the supply device7of the consumer assembly5to the high-pressure conduit system27or buffer tank41remains below a predetermined pressure within the period of time.

With this procedure it is tested with whether the pressurization device61of the consumer assembly5in question is operating properly, i.e., whether it is capable of building up a sufficient pressure in the buffer tank41. In case a sufficient pressure level cannot be reached, a corresponding failure signal will be generated and transmitted via the aircraft data network (ADN).

Operating the pressurization device61such that water is conveyed in the line connecting the supply device7of a consumer assembly5, such as the faucet37or the toilet39, to the buffer tank41;monitoring the flow in the line connecting the supply device7, such as the faucet37or the toilet39, to the buffer tank41; andproviding a failure signal when the flow in the line connecting the supply device7of the consumer assembly5to the buffer tank41remains below a predetermined second flow level within the period of time.

With this embodiment it is again tested with whether the pressurization device61of the consumer assembly5in question is also operating properly, i.e., whether it is capable of providing a sufficient pressure and hence flow in the conduit between the buffer tank41and the supply device7, or whether there is a blockage in that conduit. In case such sufficient flow level cannot be reached, a corresponding failure signal will be generated and transmitted via the aircraft data network (ADN).

In a further embodiment, the afore-mentioned procedures can be combined to the following test procedure to be run during system start-up or as a general system test procedure (seeFIG.4). However, it is to be noted that other combinations and sequences of the procedures may be employed as start-up or system test procedure.

In this embodiment, the start-up or system test procedure starts with Procedure 1, and when the gas pressure in the high-pressure conduit system27does not drop below a predetermined pressure and the test is passed, the procedure proceeds to the next step where above Procedure 11 is conducted. In case, Procedure 1 is not passed, i.e., there is a pressure drop which is too large, the routine stops and the entire system has to be checked in a maintenance procedure as indicated in the left part of aFIG.4.

This generally applies to any of the following steps. Whenever a test is not passed the procedure stops and a maintenance is required (left part).

When Procedure 11 was successfully conducted, i.e., a sufficient pressure buildup could be obtained which is also maintained over a predetermined period of time, the procedure continues to the next step, where Procedures 1 and 3 are conducted with the inlet valves47of the consumer assemblies5being in the open position, so as to test whether the signals delivered by different pressure sensors31,67are in agreement with each other and the sensors31,67are working correctly. In case, this test is passed, the procedure continues to the next step where above Procedure 12b is performed.

In the following Procedures 7a and7bare performed in the next step. Then Procedure 2 is conducted in a further step. In the next step the already mentioned Procedure 3 is performed but with the inlet valves47being subsequently opened as discussed above.

In the following steps Procedures 4, 5, 6, 8, 9, and 10 are subsequently conducted.

In the final step the consumer assemblies5and especially the pressurization devices61are further tested via Procedures 12a, 12c and 12d. When this final test is passed, the procedure proceeds to the remaining startup.

During system operation, the above Procedures 1 to 12d can be run at predefined times or continuously as soon as the test conditions are met.

For example, the central pump21conveys water and re-fills the buffer tanks41of the consumer assemblies so that those of the above test procedures can be run, when operation of the central pump21is required. On the other hand, if the system is not in use or operated without running the central pump21, because the consumer water supply is at such a low level that buffer tanks41do not need to be re-filled, those tests procedures can be run that require the central pump21being operated.

However, the consumer water supply has priority, i.e. if a consumer assembly5requests for water during a test, the test procedure is interrupted and restarted as soon as the test conditions are met again.

Moreover, it is to be noted that in another preferred embodiment only a subset of the procedures will be conducted during aircraft start-up in order to be fast and efficient. At the same time, certain tests can also be carried out after a predefined time period has elapsed, for example every 10 days or e.g. every 20 flight cycles.

However, a system test can also be initiated by the cabin crew via the flight attendant panel or by the flight crew via the aircraft maintenance system in case they assume a leak or a malfunction of the water system1for example an abnormal low water tank capacity or low water pressure at the point of use.

In case a failure is detected in one of the above steps, the crew is informed and automated actions are possible as already indicated, e.g., switching off the central pump21, close inlet valves41etc. In addition, manual crew actions may also be required after the crew has been informed, e.g., verify failures, and disable/close lavatories.

It can be taken from the above description of the preferred embodiments, that the disclosure herein provides for an efficient method to check the status of an on-board water supply and distribution system without the need to visually inspect such system.

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