AIRCRAFT AND WARNING DEVICE FOR AN "ENGINE OIL SMELL" IN AN AIRCRAFT CABIN OF AN AIRCRAFT

Description

[0001] The present invention relates to an aircraft having at least two aircraft engines, with a device for branching off bleed air from the various aircraft engines to supply an air conditioning system of an aircraft cabin with supply air, and a warning device for an "engine oil smell" in an aircraft cabin of an aircraft having at least two aircraft engines, and with a device for branching off bleed air from the various aircraft engines to supply an air conditioning system of an aircraft cabin with supply air.

[0002] Essentially, the compressed air required to operate the aircraft's interior air conditioning system is diverted from the compressor stage of an aircraft engine, which is also referred to as bleed air. The line used to discharge the bleed air is also called a bleed duct.

[0003] Since aircraft engines necessarily have multiple bearings lubricated with a lubricant such as oil, a technical fault can cause a leak, allowing small amounts of contaminants to enter the bleed air and thus lead to an unpleasant "engine oil odor" in the cabin air. Since the bleed air is diverted from the compressor stages of various engines and combined before being fed into the aircraft cabin, identifying the engine causing the leak is not possible solely by detecting the "engine oil odor" in the cabin.

[0004] To eliminate this "engine oil smell" and identify the engine causing the smell, the cockpit crew first successively shuts off the individual engine bleed air connections and then, after a short period of time, shuts them back on and checks whether the "engine oil smell" still persists in the cabin air. Once the engine causing the smell has been identified, the bleed air supply from that engine is subsequently shut off, and the "engine oil smell" is eliminated. In this case, the subjective assessment of the crew's noses serves as the sensor for whether an "engine oil smell" is present and which engine is causing the smell. This search for the source takes an average of approximately 20 minutes and is based solely on the crew's subjective perception.Furthermore, this switching on and off of the bleed air supply necessarily requires a further supply of the contaminated bleed air for at least a short time until the engine causing the problem is identified.

[0005] Following a so-called "engine oil smell" in flight, an inspection can be conducted on the ground using handheld detectors. This also requires the aircraft engines to be individually switched on and off until the offending engine is identified. Such a run-up is complex and generally time-consuming, costly, and personnel-intensive. It may happen that the "engine oil smell" does not occur on the ground, as the operating and environmental conditions of the engines on the ground and in the air are completely different, making it impossible to identify the engine causing the "engine oil smell" on the ground.

[0006] Various measurement methods and measuring devices that can be connected externally to the engine are known from GB 2 181 847 A, US 2005 / 0229686 A1, US 8,938,973 B2, and EP 1 701 160 A1. These can be used to detect bleed air contamination while the aircraft is on the ground. Identifying the engine responsible for the contamination in flight is therefore not possible.

[0007] From the subsequently published WO 2016 / 189420 A1, the installation of air quality sensors in an aircraft ventilation system is known in order to detect the type and concentration of possible contaminants.

[0008] Against this background, the object of the invention is to provide an aircraft and a warning device by which the reliability of "Engine Oil Smell" detection is improved.

[0009] To achieve this object, an aircraft having the features of claim 9 and a warning device having the features of claim 1 are proposed. Further preferred developments can be found in the subclaims, the figures and the associated description.

[0010] According to the basic idea of the invention, it is proposed that at least one air quality sensor device is provided which is designed to monitor the air quality of the bleed air branched off from at least one of the aircraft engines and to emit a signal upon detection of impurities, and that at least one display device is provided which displays a signal depending on the signal emitted by the air quality sensor device.

[0011] The term "bleed air" encompasses the airflow bleed from the aircraft engine, both upstream and downstream of the aircraft's on-board air conditioning system, where the bleed air is processed for introduction into the aircraft cabin. The inventive concept is thus based on two steps: first, the air quality of the bleed air is objectively detected by the air quality sensor device, so that contamination in the bleed air can be identified independently of the crew's subjective perception. Second, the provided display device generates a signal that objectively indicates bleed air contamination detected by the air quality sensor device and actively alerts the crew to bleed air contamination.If the specified limit value for bleed air contamination that must be exceeded to trigger the warning signal is set sufficiently low, the crew can be alerted to contamination even if the contamination is not yet objectively perceptible to the crew.

[0012] According to the invention, at least two air quality sensor devices are provided which detect the air quality of the bleed air branched off from the different aircraft engines separately from one another, and a display device is provided which displays an aircraft engine-individualized signal depending on the signals of the different air quality sensors.

[0013] The proposed further development allows the air quality of the bleed air diverted from the engines to be detected separately by the air quality sensor devices. Since the signal from the display device is also an aircraft engine-specific signal, it is also possible to directly identify the engine causing the bleed air smell, allowing the respective bleed air connection to be shut off and the engine oil smell to be remedied promptly. The aircraft engine-specific signal can then be logged, allowing appropriate maintenance measures to be performed on the ground without the need for a further run-up to identify the engine causing the smell.

[0014] The inventive solution thus enables real-time detection of bleed air contamination with simultaneous identification of the engine, allowing for rapid action to eliminate the engine oil smell as reliably as possible. For this to happen, the engine oil smell does not even have to have occurred in the aircraft cabin and thus be detectable, provided only one of the air quality sensors generates a corresponding signal. By separately detecting the bleed air diverted from the aircraft engines, the air quality sensors are effectively assigned to the sources of the bleed air, thus enabling very early warning if the bleed air of one of the aircraft engines is contaminated.

[0015] According to the invention, a common evaluation unit is provided, to which the signals from the air quality sensor devices are fed, which generates the signal displayed on the display device from the signals from the air quality sensor devices. The proposed solution enables a very simple system architecture with the air quality sensor devices, the display device, and the common evaluation unit arranged between them to be implemented. Predetermined limit values can then be stored in the evaluation unit with a corresponding evaluation algorithm in which the signals from the air quality sensor devices are processed. If the limit values are exceeded by one of the signals from the air quality sensor devices, the aircraft engine-specific signal is then displayed on the display device.Alternatively, the signals from the air quality sensors can simply be processed and displayed directly on the display unit. Exceeding the specified limits can then be signaled by changing the display of the measured values, such as by changing the color. The evaluation unit can be designed as a standalone component or integrated into the on-board electronics. If the proposed solution is designed as a retrofit for aircraft already in flight, it is advisable to design the evaluation unit as a separate component, thus avoiding the need to intervene in the on-board electronics.

[0016] Furthermore, the display device can also have a plurality of display fields or display elements, each assigned to an aircraft engine or a group of aircraft engines, and the aircraft engine-individualized signal can be realized by displaying a signal on one of the display fields or by activating one of the display elements. Using the plurality of display fields or display elements, the signal can be individualized with respect to an engine by displaying a signal on a display field assigned to the respective aircraft engine or by actuating a display element assigned to the engine. The causing engine can thus be easily identified based on which of the display elements is actuated or on which display field a corresponding signal is generated.

[0017] In one embodiment, the display device can be designed to be particularly cost-effective and at the same time easily recognizable by the display elements being formed by LEDs.

[0018] Furthermore, in an illustrative example not falling within the scope of the claims, the air quality sensor devices can be formed by optical sensor devices comprising at least one light source radiating into the bleed air and at least one photodiode detecting the reflection of the emitted light. If oil or other contaminant particles are present in the bleed air, the light emitted by the light source is reflected by these particles onto the photodiode, which then generates a signal. This further utilizes the advantage that the oil has fluorescent properties, so that the light emitted and reflected by the light source is further amplified by the fluorescent properties.

[0019] The fluorescent effect and the amplification of the reflected light by the oil particles are particularly intensified when the light source is a UV light source.

[0020] It is further proposed that the indicator be located in the cockpit of the aircraft. This allows crew members, and especially the pilots in the cockpit, to be alerted to the presence of an engine oil smell as early as possible, allowing them to initiate appropriate countermeasures as promptly and as early as possible.

[0021] Furthermore, the air quality sensor devices can each have a filter arranged in a flow line of the bleed air. The particles are collected by the filter, so that a larger quantity of particles adheres to them, even at very low particle concentrations in the bleed air. In this case, the sensors of the air quality sensor devices are directed at the filter or coupled to the filter and detect the particles adhering to the filter. Due to this increased quantity of particles on the filter, even very low particle volume concentrations in the bleed air can be detected. The filters can be formed, for example, by Millipore membrane filters.

[0022] Furthermore, filters can also be provided upstream of the sensor devices to protect the air quality sensor devices from damage and thus maintain their functionality.

[0023] According to the invention, the air quality sensor devices comprise a sensor arranged in a bleed air flow line. The bleed air flows directly around the sensors thanks to the proposed further development. If the sensor is arranged in the so-called bleed duct, the bleed air introduced into the aircraft cabin flows directly around the sensor, so that the detected signal represents the air quality of the bleed air introduced into the cabin unadulterated and directly. Furthermore, the flow line can also be a branch line of the bleed duct, in which a portion of the bleed air is discharged from the bleed duct and guided over the sensor. In this case, too, contamination of the bleed air directly leads to a signal from the air quality sensor device and to a signal from the display device. However, the provision of a branch line can offer advantages with regard to the structural connection of the air quality sensor device.

[0024] Furthermore, in this case, at least one pressure reducer can be provided to reduce the static pressure in the bleed air flow line, which is arranged upstream of the sensor in the flow direction. The bleed air branched off from the compressor has a higher static pressure, which is deliberately reduced by the pressure reducer, thereby reducing the forces acting on the sensor.

[0025] Furthermore, at least one nozzle, preferably a Venturi nozzle, can be provided in the flow line of the bleed air, which is arranged upstream of the sensor in the flow direction.

[0026] The nozzle and pressure reducer can create consistent pressure and flow conditions in the bleed air flowing past the sensor, thereby increasing the sensor's measurement accuracy. It is further proposed that a branch line be provided connected to a bleed air flow line, and that the air quality sensor devices detect the air quality of the bleed air in the respective branch line. The bleed air extracted in the branch line is representative of the bleed air branched from the respective engine. The branch line can be individually shaped and designed for connecting the air quality sensor device, or it can also be part of the air quality sensor device itself.

[0027] It is further proposed that the air quality sensor device and the display device be configured to monitor the air quality and display the signal when the aircraft is on the ground and when the aircraft is in the air. The proposed solution allows the signals from the air quality sensor devices to be displayed in real time via the display device during flight, so that a warning about an "engine oil smell" is immediately displayed regardless of the subjective perception of the crew and also regardless of any perceptible cabin air contamination, regardless of whether the aircraft is on the ground or in the air.

[0028] Furthermore, it is preferred that the air quality sensor device and the display device are configured to continuously monitor the air quality and continuously display the signal. Firstly, by continuously monitoring and displaying the signal, the time of occurrence can be precisely determined retrospectively, thereby simplifying the process of locating the source of the error in conjunction with possible operating parameters of the aircraft engine. Secondly, a fault in the air quality sensor device or display device can also be easily detected by continuously detecting the air quality and displaying the signal, for example, when the display device no longer displays a signal.

[0029] Furthermore, to achieve the object, a warning device for an "engine oil smell" in an aircraft cabin of an aircraft with at least two aircraft engines and a device for branching off bleed air from the various aircraft engines to supply an air conditioning system of an aircraft cabin with supply air is proposed, wherein at least two air quality sensor devices are provided which detect the air quality of the bleed air branched off from the different aircraft engines separately from one another, and a display device is provided which displays an aircraft engine-individualized signal depending on the signals from the different air quality sensors.

[0030] The aircraft cabin includes both the aircraft cockpit and the passenger cabin, or possibly crew compartments and cargo space.

[0031] The proposed warning device can be retrofitted to a finished aircraft, with the resulting benefits more than justifying the comparatively low cost of the air quality sensors and display. Furthermore, the warning device can also be integrated into an aircraft system during the initial planning phase of aircraft development, and the warning device can also interact with other aircraft systems.

[0032] The invention will be explained below using preferred embodiments with reference to the attached figures. Fig. 1: an aircraft with a duct system for supplying bleed air from the aircraft engines into the aircraft cabin; and Fig. 2: an enlarged aircraft engine with a duct system for extracting bleed air; and Fig. 3: an air quality sensor device with an optical sensor in an illustrative example, which falls within the scope of protection of the claims; and which does not Fig. 4: an air quality sensor device with an optical sensor in a further illustrative example, which does not fall within the scope of protection of the claims; and Fig. 5: a duct system with a branch line and a visual inspection window, which does not fall within the scope of protection of the claims; and Fig. 6: an aircraft with a warning device according to the invention in a schematic representation; and Fig. 7: a display device of a warning device according to the invention, and Fig. 8: an air quality sensor device, wherein the sensor is formed by a metal oxide sensor.

[0033] In the Figure 1An aircraft 1 with five jet engines 2, 3, 4, 5 and 6 can be seen, whereby the aircraft engine 6 located in the area of the rear horizontal stabilizer is only a so-called Auxiliary Power Unit (APU), which essentially serves on the ground to supply various units, such as the air conditioning system, with air and energy. Figure 2 An enlarged view of an aircraft engine 2 with a bleed air extraction can be seen.

[0034] Bleed air is extracted from the compressor stages of aircraft engines 2, 3, 4, 5, and 6 via flow lines 9 and 10, combined via flow lines 12, 13, and 14, and fed to an air conditioning system for the aircraft cabin via branches 7. Flow lines 9 and 10 are provided with reference symbols only in aircraft engine 2, but are of course also provided in aircraft engines 3, 4, 5, and 6.

[0035] The bleed air is taken from the fan of aircraft engine 2 via a flow line 9 and from a compressor stage of aircraft engine 2 via a pair of flow lines 10a and 10b. The bleed air is branched off via flow line 10a from the 5th stage of the low-pressure section and via flow line 10b from the 9th stage of the high-pressure section of the compressor. The partial flows of the bleed air are then recombined in flow line 10 and finally fed to a pre-cooler 11, which also receives the bleed air from flow line 9 of the fan. After exiting pre-cooler 11, the bleed air is then fed through flow line 14 into the aircraft cabin's air conditioning system. The supply of bleed air through the flow lines 9, 10a, 10b and 10 can be switched on, switched off or volume-controlled by a plurality of valves and associated control devices 15.To this extent, aircraft 1 corresponds to the state of the art.

[0036] In the Figures 3, 4 and 5 is the detail X of the Figure 2 enlarged in various embodiments. The bleed air branched off from the compressor stage via the flow lines 10a and 10b is brought together in the flow line 10, in which in the embodiments of the Figures 3 and 4 An air quality sensor device 16 is provided in each case. Depending on the positioning of the air quality sensor device 16 in the flow lines 9, 10, 12, 13 or 14, it can detect the bleed air branched off from the fan or the compressor stage separately, or also the bleed air branched off from a single aircraft engine 2, 3, 4, 5, 6 or also the bleed air branched off from a group of, for example, two aircraft engines 2, 3, 4, 5 or 6 after it has been combined.

[0037] In the illustrative example of Figure 3, which does not fall within the scope of the claims, the air quality sensor device 16 is formed by an optical sensor device and comprises a light source 42 and a photodiode as a sensor 43, which is connected to an evaluation unit 23. The light source 42 radiates into the flow line 10 into the bleed air. If engine oil 44 is present in the bleed air, the light emitted by the light source 42 is reflected by the engine oil 44 onto the photodiode, which then generates a signal. The light source 42 and the sensor 43 are arranged on different sides of the flow line 10. In the illustrative example of the Figure 4, which does not fall within the scope of the claims, an air quality sensor device 16 operating according to the same measuring principle can be seen, in which the light source 42 and the sensor 43 are arranged on the same side of the flow line 10. In both air quality sensor devices 16, the sensor 43 is positioned such that the light 42 emitted by the light source 42 can only reach the sensor 43 by reflection from the engine oil 44, so that the sensor 43 does not deliver a signal if no engine oil 44 is present in the bleed air.

[0038] The sensor 43 is connected to the evaluation unit 23 via a signal line 19, which in turn is connected to a display device 24 via a signal line 22. Four display elements 25, 26, 27, and 28 in the form of light-emitting diodes (LEDs) are provided on the display device 24. Each of the LEDs is assigned to an aircraft engine 2, 3, 4, and 5, which is identified by the markings Eng1, Eng2, Eng3, and Eng4.

[0039] As in the Figure 6As can be seen, further air quality sensor devices 17 and 18 are provided in the aircraft 1. The air quality sensor devices 16 and 17 are assigned to the flow lines designated by reference numerals 13 and 14 in Figure 1, in which the bleed air from the two adjacent aircraft engines 2 and 3, or 4 and 5, is fed to the connections 7 of the air conditioning system after being merged. However, additional air quality sensor devices can be provided so that the bleed air branched off from the aircraft engines 2, 3, 4, and 5 is detected separately. If each of the aircraft engines 2, 3, 4, and 5 is assigned an air quality sensor device, the aircraft engine 2, 3, 4, or 5 causing the engine oil smell can be directly identified when it occurs.If the air quality sensor devices 16 and 17 were assigned to a respective flow line 13 and 14, in which the bleed air from two aircraft engines 2 and 3 or 4 and 5 is supplied to the air conditioning system, only the pair of two aircraft engines 2, 3 or 4, 5 causing the "engine oil smell" would be possible to identify. Furthermore, a third air quality sensor device 18 is provided, which is also connected to the evaluation unit 23 via a signal line 21. The third air quality sensor device is assigned to an additional aircraft engine 6, which is used as an auxiliary power unit (APU) only when the aircraft 1 is on the ground and additional consumers, such as the air conditioning system, must be supplied with energy or bleed air.

[0040] The signals from the air quality sensor devices 16, 17 and 18 are processed in the evaluation unit 23 and compared there with stored limit values. If the predetermined limit values are exceeded, a corresponding warning signal is sent via the signal line 22 to the display device 24, which is located in the Figure 7is shown. The display device 24 shown in Figure 7 comprises, in addition to the display elements 25 to 28, additional display elements 29 to 34 which are formed by light-emitting diodes and are assigned, based on the markings, to the individual aircraft engines 2, 3, 4, 5 and 6 and to contamination of the bleed air either with engine oil (OIL) or with other possible contaminants, such as de-icing fluid or hydraulic fluid (OTHER). If one or more of the air quality sensor devices 16, 17 or 18 detect engine oil 44 or other contaminants in the bleed air, a corresponding signal is generated via the evaluation unit 23 and one or more of the light-emitting diodes on the display device 24 are illuminated accordingly.By selecting which of the LEDs on the display device 24 illuminates, a signal specific to each aircraft engine is generated, which immediately and objectively indicates to the crew that an "engine oil smell" or other bleed air contamination is present. Second, by selecting the illuminated LED, it is indicated which of the aircraft engines 2, 3, 4, 5, or 6 is causing the "engine oil smell" or contamination by other substances. This allows the bleed air taken from the respective aircraft engine 2, 3, 4, 5, or 6 to be shut off by actuating the respective valves 15, and the "engine oil smell" or cabin air contamination can be actively and immediately remedied during flight. If the threshold values are set sufficiently low, the respective bleed air could even be shut off before the "engine oil smell" is even noticeable in the aircraft cabin.To switch off the respective bleed air, additional switches or sensor surfaces 35 to 39 assigned to the aircraft engines 2, 3, 4, 5, and 6 are provided on the display device 24. In addition to simply displaying the warning signal, the display device 24 also serves as an actuating device, thus forming a multifunctional device for monitoring and controlling the bleed air in the aircraft 1. Furthermore, an on / off switch 40 and a rotary control 41 for regulating the brightness of the LEDs are provided on the display device 24.

[0041] In the described illustrative examples, which do not fall within the scope of the claims, the air quality sensor devices 16, 17, and 18 are designed as optical sensor devices, which is advantageous in that the oil particles 44 present in the bleed air in the event of an "engine oil smell" have fluorescent properties and thus amplify the light reflected onto the sensors 43 and the signal from the sensors 43. This fluorescent effect can be particularly enhanced if a UV light source (black light source) is used as the light source 42.

[0042] Sensors 43 according to the invention can preferably be designed as semiconductor gas sensors (metal oxide semiconductor MOS) as static or dynamic (temperature-modeled). In alternative examples not falling within the scope of the claims, a sensor 43 of the following type can also be used: Infrared sensor (IR sensor) Photoionization detector (PID sensor) Electrochemical cell (NC sensor) Carbon dioxide sensor (CO2) Carbon monoxide sensor (CO) Non-dispersive infrared sensor (NDIR) Photoacoustic spectroscopy (PAS) Thermal conductivity sensor (TCD) Pellistor (PEL) Field effect transistor (FET) Flame ionization detector (FID) Tunable laser diode spectroscopy (TLDS) TLDS with cavity ring down (CRDS) TLDS with photoacoustic detector (PAS) Fourier transform IR spectrometer (FTIR) Particle sensor Condensation particle counter (CPC) Faraday cup electrometer (FCE) Hygroscopic tandem differential mobility analyzer (HTDMA) Optical particle counter (OPC) Scanning mobility particle sizer (SMPS) Single particle soot photometer (SMSP) Sensor array Quartz crystal microbalance Use of surface waves.

[0043] Furthermore, in other alternative examples, which do not fall within the scope of the claims, the use of the following measuring devices and measuring methods as air quality sensor devices for detecting the bleed air or the cabin or cockpit air is conceivable: Mass spectrometer (MS) Ion mass spectrometer (IMS) Laser ion mass spectrometer (LIMS) Gas chromatograph (GC)

[0044] The advantage of these measuring devices is that they can detect the exact composition of the air.

[0045] Furthermore, the display device 24 with the display elements 25 to 34 for displaying the aircraft engine-specific signal was described. However, the display device 24 can also be designed as a display with multiple display fields or display surfaces. The aircraft engine-specific signal can be formed, for example, by displaying a special symbol, e.g., in the form of a symbolized aircraft, with the information about the occurrence of an "engine oil smell" then being provided by warning lamps appropriately positioned on the aircraft 1. Furthermore, the aircraft engine-specific signal can also simply be formed by a word sequence with corresponding content displayed on the display, such as: "Engine Oil Detected - ENG1".

[0046] The display device 24 is preferably positioned so that it can be read at all times. A location that the crew sees as frequently as possible is preferred, such as within the field of vision of the cockpit crew or the captain and co-pilot.

[0047] Furthermore, the detected data and in particular the identification of the aircraft engine 2, 3, 4, 5 or 6 causing the failure can also be stored in a memory unit of the display device 24 or the evaluation unit 23 over a longer period of time, so that the corresponding maintenance measures can subsequently be carried out on the ground without a further run-up.

[0048] The air quality sensor devices 16, 17, and 18 can preferably be mounted in a housing. Branch lines 45 can be provided in the air quality sensor devices 16, 17, and 18, which are or can be connected to the flow lines 9, 10, 12, 13, or 14, so that the installation of the retrofittable warning devices only requires corresponding connections to the flow lines 9, 10, 12, 13, and 14 and sufficient installation space. Furthermore, the evaluation unit 23 and the display device 24 must be provided, but these can also be combined as a structural unit. Finally, the air quality sensor devices 16, 17, and 18, the evaluation unit 23, and the display device 24 only need to be interconnected via corresponding signal lines 19, 20, 21, and 22. The effort required to retrofit existing aircraft is thus comparatively low.

[0049] In the Figure 5An illustrative example, which does not fall within the scope of the claims, with a simplified control option for detecting "engine oil smell" can be seen, in which a branch line 45 is connected to the flow line 10. A transparent visual inspection window 46 is provided in the branch line. The offending aircraft engine 2, 3, 4, 5, or 6 can be easily detected in this case by the maintenance personnel on the ground shining a light source 42 through the visual inspection window 46. If oil particles 44 are present in the bleed air, the light is reflected and amplified by the fluorescent properties of the oil particles 44. The oil particles 44 then begin to glow, which can be visually perceived by the maintenance personnel.

[0050] This very simple solution requires only an accessible branch line 45.

[0051] In the Figure 8A solution can be seen in which the sensor 43 is formed by a metal oxide sensor, with a temperature-modeled semiconductor sensor preferably being used. The advantages of such a sensor 43 are that an ageing-free and drift-free detection of the gases and vapors in the bleed air is possible with a single sensor 43. The highly sensitive sensor, with its sensitive semiconductor layer made of metal oxide, is in contact with the branched bleed air. The measured variable is the electrical resistance, which either decreases or increases based on the reactions taking place on the sensor surface, whereby the sensor can be operated at a constant or, preferably, also at a modulated temperature.

[0052] Multiple sensors 43 of the same or different types can be used, which are designed to detect the bleed air in different measuring ranges, such as temperature and pressure ranges. Alternatively, however, different sensors 43 of different types can also be used, if, for example, different components in the bleed air are to be detected. By combining sensors 43 of different or the same type, the measuring range, the sensitivity, and ultimately also the accuracy of the air quality sensor device 16 can be improved.

[0053] In the flow direction of the bleed air branched off from the flow line 10 in the flow line 10b, a filter 48 is provided, which filters the branched off bleed air and thereby additionally protects the downstream air quality sensor device 16. In addition to the actual sensor 43, the air quality sensor device 16 also comprises a critical nozzle 47 arranged upstream of the flow direction of the branched off bleed air, in which the flow conditions in the branched off bleed air are adjusted to conditions suitable or even optimal for the sensor 43.

[0054] Furthermore, a second flow line 10a is provided, which is connected to the flow line 10 and in which a small amount of bleed air is also branched off from the flow line 10. A Venturi nozzle 49 is provided in the flow line 10b, to which the flow line 10b is connected in the region of the smaller cross-section. In the Venturi nozzle 49, the branched off bleed air is accelerated and the static pressure in the bleed air is reduced, whereby the bleed air is sucked in from the flow line 10b. The flow line 10a, together with the Venturi nozzle 49, essentially forms a suction device for generating a driving pressure difference in the flow line 10b between the inlet and the outlet. The small amount of branched off bleed air is then passed further in the flow line 10 through a cooling section 50 after flowing through the Venturi nozzle and finally, after cooling, released into the environment through a scattering nozzle 51.The Venturi nozzle 49 acts here as a pressure reducer, which reduces the static pressure in the branched bleed air at a point arranged upstream of the air quality sensor device 16, so that the bleed air is practically drawn through the air quality sensor device 16.

Claims

1. Warning device for detecting "engine oil smell" in an aircraft cabin of an aircraft (1), wherein the aircraft (1) is equipped with at least two aircraft engines (2, 3, 4, 5, 6) and with - a device for diverting bleed air from the different aircraft engines (2, 3, 4, 5, 6) to supply fresh air to an air conditioning system of an aircraft cabin, wherein - at least two air quality sensor devices (16, 17, 18) are provided, which are adapted to monitor the air quality of the bleed air diverted from the different aircraft engines (2, 3, 4, 5, 6) and to detect it separately from each other and to emit a signal upon detection of pollutants, and wherein - at least one display device (24) is provided, which is adapted to display an aircraft engine-specific signal as a function of the signals from the different air quality sensor devices (16, 17, 18), characterized in that - a common evaluation unit (23) is provided, to which the signals from the air quality sensor devices (16, 17, 18) are fed, which is adapted to generate, from the signals from the air quality sensor devices (16, 17, 18), the signal displayed in the display device (24), wherein - the air quality sensor devices (16, 17, 18), in an installed state in which the warning device is installed in an aircraft, comprise a sensor (43) arranged in a flow line (9, 10) of the bleed air, wherein - the sensor (43) is formed by at least one metal oxide sensor.

2. Warning device according to claim 1, characterized in that - the display device (24) comprises a plurality of display fields or display elements (25 to 34) each assigned to an aircraft engine (2, 3, 4, 5, 6) or a group of aircraft engines (2, 3, 4, 5, 6), and - the aircraft engine-specific signal is produced by displaying a signal on one of the display fields or by activating one of the display elements (25 to 34).

3. Warning device according to claim 2, characterized in that - the display elements (25 to 34) are formed by LEDs.

4. Warning device according to any one of claims 1 to 3, characterized in that - the display device (24) is arranged in a cockpit of the aircraft (1).

5. Warning device according to any one of the preceding claims, characterized in that - at least one pressure reducer is provided which reduces the static pressure in the flow line (9, 10) of the bleed air and which, when installed in an aircraft, is arranged upstream of the sensor (43) in the direction of flow.

6. Warning device according to any one of the preceding claims, characterized in that - at least one nozzle, preferably a venturi nozzle, is provided in the flow line (9, 10) of the bleed air, which, when installed in an aircraft, is arranged upstream of the sensor (43) in the direction of flow.

7. Warning device according to any one of claims 1 to 6, characterized in that - the air quality sensor device (16, 17, 18) and the display device (24) are adapted to monitor the air quality and to display the signal when the aircraft (1) is on the ground and when the aircraft (1) is in the air.

8. Warning device according to any one of claims 1 to 7, characterized in that - the air quality sensor device (16, 17, 18) and the display device (24) are adapted to continuously monitor the air quality and to continuously display the signal.

9. Aircraft (1) with at least two aircraft engines (2, 3, 4, 5, 6) and a device for diverting bleed air from the different aircraft engines (2, 3, 4, 5, 6) to supply fresh air to an air conditioning system of an aircraft cabin, characterized in that - a warning device according to any one of claims 1 to 8 is provided.

10. Aircraft (1) according to claim 9, characterized in that - at least one branch line (45) connected to a flow line (9, 10) of the bleed air is provided, and - the air quality sensor devices (16, 17, 18) are adapted to detect the air quality of the bleed air in the respective branch line (45).