Patent Publication Number: US-2023145226-A1

Title: Detecting fluid leakage at aircraft hatch

Description:
This application claims priority to Indian Patent Appln. No. 202111051811 filed Nov. 11, 2021, which is hereby incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     This disclosure relates generally to an aircraft and, more particularly, to an interface between a hatch and a wall of an aircraft fuselage. 
     2. Background Information 
     An airplane fuselage includes a fuselage wall and a door for opening and closing an opening in the fuselage wall. A rubber seal element is included to provide a sealed interface between the door and the fuselage wall. Degradation of this seal element may lead to gas leakage (e.g., atmospheric pressure leakage) across the sealed interface and out of the airplane fuselage. However, it may be difficult to detect such gas leakage until the leak is relatively large using existing airplane decompression detection systems. There is a need in the art therefore for systems and methods for detecting a fluid leak/an unexpected change in pressure at, inter alia, an airplane door. 
     SUMMARY OF THE DISCLOSURE 
     According to an aspect of the present disclosure, an assembly is provided for an aircraft. This aircraft assembly includes a fuselage and a second system. The fuselage includes a wall and a hatch configured to close an opening in the wall. The sensor system includes an optical fiber, a transmitter and a receiver. The optical fiber is arranged at an interface between the hatch and the wall. The transmitter is configured to transmit first electromagnetic radiation into the optical fiber. The receiver is configured to detect second electromagnetic radiation received from the optical fiber to provide receiver data. The sensor system is configured to detect fluid leakage across the interface between the hatch and the wall based on the receiver data. 
     According to another aspect of the present disclosure, another assembly is provided for an aircraft. This aircraft assembly includes a fuselage and a sensor system. The fuselage includes a wall and a hatch configured to close an opening in the wall. The sensor system includes an optical fiber, a transmitter and a receiver. The optical fiber is arranged at an interface between the hatch and the wall. The transmitter is configured to transmit first electromagnetic radiation into the optical fiber. The receiver is configured to detect second electromagnetic radiation received from the optical fiber to provide receiver data. The sensor system is configured to determine temperature data at the interface between the hatch and the wall based on the receiver data. 
     According to still another aspect of the present disclosure, a method is provided involving an aircraft fuselage including a wall and a hatch. During this method, first electromagnetic radiation is transmitted into an optical fiber. The optical fiber is arranged at an interface between the hatch and the wall. The hatch is configured to close an opening in the wall. Actual second electromagnetic radiation received from the optical fiber is detected. A fluid leak across the interface between the hatch and the wall is detected based on a wavelength shift between the actual second electromagnetic radiation and expected second electromagnetic radiation. 
     The sensor system may also be configured to process the temperature data to detect fluid leakage across the interface between the hatch and the wall. 
     The sensor system may also be configured to process the receiver data to determine a difference between the second electromagnetic radiation and expected electromagnetic radiation. The sensor system may still also be configured to detect the fluid leakage based on the difference between the second electromagnetic radiation and the expected electromagnetic radiation. 
     The difference between the second electromagnetic radiation and the expected electromagnetic radiation may be or include a wavelength shift between the second electromagnetic radiation and the expected electromagnetic radiation. 
     The sensor system may also be configured to determine a flowrate of the fluid leakage across the interface between the hatch and the wall based on the receiver data. 
     The sensor system may also be configured to provide an indicator signal when the flowrate of the fluid leakage across the interface is greater than a threshold. 
     The sensor system may also be configured to determine a location of the fluid leakage across the interface. 
     The optical fiber may include a grating configured to shift a wavelength of the first electromagnetic radiation. 
     The first electromagnetic radiation may interact with and pass through the grating to at least partially provide the second electromagnetic radiation. 
     The second electromagnetic radiation may include a reflection of at least a portion of the first electromagnetic radiation by the grating. 
     The optical fiber may include a plurality of gratings arranged at discrete locations along the interface between the hatch and the wall. The gratings may include a first grating and a second grating. The first grating may be configured to reflect a first wavelength of electromagnetic radiation. The second grating may be configured to reflect a second wavelength of electromagnetic radiation. 
     The optical fiber may include a plurality of gratings arranged at discrete locations along the interface between the hatch and the wall. Each of the gratings may be associated with unique electromagnetic radiation transmitted into the optical fiber. 
     The optical fiber may extend longitudinally between a first end and a second end. The transmitter and the receiver may be arranged at the first end. 
     The optical fiber may extend longitudinally between a first end and a second end. The transmitter may be arranged at the first end. The receiver may be arranged at the second end. 
     The aircraft assembly may also include a seal element arranged at the interface between the hatch and the wall. The optical fiber may be disposed along and outside of the seal element. 
     The aircraft assembly may also include a seal element arranged at the interface between the hatch and the wall. At least a portion of the optical fiber may be disposed within the seal element. 
     The optical fiber may be disposed at an exterior side of the interface between the hatch and the wall. 
     The optical fiber may be disposed at an interior side of the interface between the hatch and the wall. 
     The aircraft assembly may also include a second sensor system including a second optical fiber, a second transmitter and a second receiver. The second optical fiber may be arranged at the interface between the hatch and the wall. The second transmitter may be configured to transmit third electromagnetic radiation into the second optical fiber. The second receiver may be configured to detect fourth electromagnetic radiation received from the second optical fiber to provide second receiver data. The second sensor system may be configured to detect fluid leakage across the interface between the hatch and the wall based on the second receiver data. 
     The present disclosure may include any one or more of the individual features disclosed above and/or below alone or in any combination thereof. 
     The foregoing features and the operation of the invention will become more apparent in light of the following description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective illustration of an aircraft. 
         FIG.  2    is a side illustration of a portion of an aircraft fuselage. 
         FIG.  3    is a sectional illustration of a portion of the aircraft fuselage taken along line  3 - 3  in  FIG.  2   . 
         FIG.  4    is a schematic illustration of an assembly for the aircraft. 
         FIG.  5    is a schematic illustration of a sensor system configured at an interface between a hatch and a wall of the aircraft fuselage. 
         FIG.  6    is a schematic illustration of another sensor system configured at the interface between the hatch and the wall of the aircraft fuselage. 
         FIG.  7    is a flow diagram of a method involving an aircraft. 
         FIG.  8    is a cross-sectional illustration of a seal element and an optical fiber configured discrete from the seal element. 
         FIG.  9    is a cross-sectional illustration of the seal element and the optical fiber configured integral with the seal element. 
         FIG.  10    is a partial illustration of the optical fiber arranged at an exterior side of the seal element. 
         FIG.  11    is a partial illustration of the optical fiber arranged at an interior side of the seal element. 
         FIG.  12    is a partial illustration of optical fibers arranged on both sides of the seal element. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    is an illustration of an aircraft  20 . This aircraft  20  may be configured as an airplane such as, but not limited to, a passenger plane or a cargo plane. The aircraft  20  of  FIG.  1    includes an aircraft fuselage  22 . This aircraft fuselage  22  includes a fuselage wall  24  and one or more fuselage hatches  26 ; e.g., doors, removable panels, etc. Each hatch  26  is configured to open and close a respective opening  28  in the wall  24 . 
     Referring to  FIGS.  2  and  3   , in a closed position, each hatch  26  engages the wall  24  at a hatch-wall interface  30  between the respective hatch  26  and the wall  24 . The hatch-wall interface  30  of  FIG.  3    is configured as a sealed interface with a polymer hatch seal element  32  (e.g., a rubber seal element) arranged between and engaging (e.g., contacting, pressed against) a surface  34  of the wall  24  and a surface  36  of the respective hatch  26 . The seal element  32  is located at the hatch-wall interface  30 . The seal element  32  of  FIG.  2    extends longitudinally along the hatch-wall interface  30  and about (e.g., completely around) the respective wall opening  28 . The seal element  32  of  FIGS.  2  and  3    may thereby seal a gap between the wall  24  and the respective hatch  26  at the hatch-wall interface  30 . 
       FIG.  4    schematically illustrates an assembly  38  for the aircraft  20 . This aircraft assembly  38  includes the wall  24 , one or more of the hatches  26  and one or more sensor systems  40 . Each of the sensor systems  40  is configured to monitor the hatch-wall interface  30  between the wall  24  and a respective one of the hatches  26 . More particularly, each sensor system  40  is configured to detect fluid leakage (e.g., airflow) across the hatch-wall interface  30  between the wall  24  and the respective hatch  26 . 
     Referring to  FIG.  5   , each sensor system  40  includes an optical fiber  42  (e.g., a strand of fiber optics), an electromagnetic radiation transmitter  44  and an electromagnetic radiation receiver  46 . Each sensor system  40  also includes a processing system  48 . 
     The optical fiber  42  is arranged at (e.g., on, adjacent or proximate) the hatch-wall interface  30  with the seal element  32 . The optical fiber  42  extends along a longitudinal centerline between a first end  50  of the optical fiber  42  and a second end  52  of the optical fiber  42 . 
     The optical fiber  42  of  FIG.  5    is configured with one or more internal gratings  54 A-H (generally referred to as “ 54 ”; schematically shown) (e.g., fiber Bragg gratings (FBG)) within a fiber core of the optical fiber  42 . These gratings  54  are arranged (e.g., distributed) at discrete locations along the longitudinal centerline between the fiber first end  50  and the fiber second end  52 . Each of the gratings  54  is configured to reflect one or more specific wavelengths of electromagnetic radiation (e.g., light) while permitting the remaining wavelengths of the electromagnetic radiation to pass/travel therethrough. Each grating  54  may thereby filter the one or more specific wavelengths of electromagnetic radiation. Each of the gratings  54  may be provided by forming a periodic variation in a refractive index of the fiber core of the optical fiber  42 ; e.g., by constructing a distributed Bragg reflector within a short segment of the optical fiber  42 . 
     Each of the gratings  54  within the optical fiber  42  is tuned for (e.g., configured to reflect/filter) a different wavelength (or wavelengths) of the electromagnetic radiation. The first grating  54 A, for example, may be tuned for a first wavelength of the electromagnetic radiation. The second grating  54 B may be tuned for a second wavelength of the electromagnetic radiation which is different than the first wavelength of the electromagnetic radiation. The second wavelength of the electromagnetic radiation may also be separated (e.g., spaced) from the first wavelength of the electromagnetic radiation by one or more intermediate wavelengths of the electromagnetic radiation to provide further differentiation between the different wavelengths of the electromagnetic radiation. 
     The transmitter  44  is configured transmit one or more wavelengths (e.g., a spectrum) of the electromagnetic radiation into the optical fiber  42 . The transmitter  44 , for example, may be configured as an electromagnetic radiation emitting device. The transmitter  44  of  FIG.  5    is disposed at and/or otherwise in communication (e.g., optically coupled) with the fiber first end  50 . 
     The receiver  46  is configured to receive radiation (e.g., optical) information via electromagnetic radiation received from the optical fiber  42 . The receiver  46  is also configured to provide receiver data generated from and/or indicative of the radiation information. The receiver  46 , for example, may be configured as an optical receptor or any other electromagnetic radiation receptor/sensor. The receiver  46  of  FIG.  5    is disposed at and/or otherwise in communication (e.g., optically coupled) with the fiber second end  52 . However in other embodiments, referring to  FIG.  6   , the receiver  46  may alternatively be disposed at and/or otherwise in communication with the fiber first end  50 . 
     Referring again to  FIG.  5   , the processing system  48  is in signal communication with the transmitter  44  and the receiver  46 . The processing system  48 , for example, may be hardwired and/or wirelessly coupled with the transmitter  44  and the receiver  46 . 
     The processing system  48  may be implemented with a combination of hardware and software. The hardware may include a memory and at least one processing device, which processing device may include one or more single-core and/or multi-core processors. The hardware may also or alternatively include analog and/or digital circuitry other than that described above. 
     The memory is configured to store software (e.g., program instructions) for execution by the processing device, which software execution may control and/or facilitate performance of one or more operations such as those described in the method below. The memory may be a non-transitory computer readable medium. For example, the memory may be configured as or include a volatile memory and/or a nonvolatile memory. Examples of a volatile memory may include a random access memory (RAM) such as a dynamic random access memory (DRAM), a static random access memory (SRAM), a synchronous dynamic random access memory (SDRAM), a video random access memory (VRAM), etc. Examples of a nonvolatile memory may include a read only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), a computer hard drive, etc. 
       FIG.  7    is a flow diagram of a method  700  involving an aircraft such as the aircraft  20  described above. This method  700  is described below for detecting fluid (e.g., air) leakage across a select one of the hatch-wall interfaces  30  (see  FIG.  5   ) during aircraft flight. However, the method  700  may alternatively be performed for detecting fluid leakage across more than one (e.g., all) of the hatch-wall interfaces  30 . Furthermore, while the method  700  is described as being performed during aircraft flight, the present disclosure is not limited thereto. 
     In step  702 , first electromagnetic radiation (e.g., a first spectrum of light) is transmitted into the optical fiber  42 . The processing system  48 , for example, may signal the transmitter  44  to emit the first electromagnetic radiation, which enters the optical fiber  42  at the fiber first end  50 . 
     In step  704 , the first electromagnetic radiation travels within the optical fiber  42  and interacts with the one or more gratings  54  to provide second electromagnetic radiation (e.g., a second spectrum of light). The first electromagnetic radiation input by the transmitter  44 , for example, travels through a first segment (e.g.,  56 A) of the optical fiber  42  to the first grating  54 A. The first electromagnetic radiation interacts with the first grating  54 A, where at least one wavelength of the first electromagnetic radiation is reflected and the remaining wavelengths of the first electromagnetic radiation pass through the first grating  54 A to provide first filtered electromagnetic radiation. This first filtered electromagnetic radiation travels through a second segment (e.g.,  56 B) of the optical fiber  42  from the first grating  54 A to the second grating  54 B. The first filtered electromagnetic radiation interacts with the second grating  54 B, where at least one wavelength of the first filtered electromagnetic radiation is reflected and the remaining wavelengths of the first filtered electromagnetic radiation passes through the second grating  54 B to provide second filtered electromagnetic radiation. This electromagnetic radiation propagation and filtering process is repeated along the optical fiber  42  with each grating  54  (e.g.,  54 C-H) until the second electromagnetic radiation is provided following interaction (e.g., filtering) with the last grating  54 ; e.g., the eighth grating  54 H in  FIG.  5   . Thus, the second electromagnetic radiation at the fiber second end  52  is different than (e.g., a derivation of) the first electromagnetic radiation at the fiber first end  50 . 
     In step  706 , receiver data (e.g., sensor data) is provided. The receiver  46 , for example, detects, captures and/or otherwise receives at least a portion or all of the second electromagnetic radiation at the fiber second end  52 . The receiver  46  may convert the received second electromagnetic radiation into the receiver data, which receiver data is indicative of the received second electromagnetic radiation. 
     In step  708 , at least one condition of the hatch-wall interface  30  is determined. The processing system  48 , for example, receives the receiver data from the receiver  46 . The processing system  48  may process this receiver data to determined whether or not there is fluid leakage across the hatch-wall interface  30 . The actual receiver data provided by the receiver  46 , for example, may be compared to (e.g., predetermined or modeled) expected receiver data, which expected receiver data is data that is expected to be received by the receiver  46  based on one or more parameters such as, but not limited to, a fully sealed hatch-wall interface  30 , current flight conditions and/or current aircraft cabin conditions. The actual receiver data may be different than the expected receiver data where, for example, a fluid leak (e.g., air pressure leakage) forms across the hatch-wall interface  30 . Such a fluid leak (e.g., air pressure leakage) may cause a local drop in fluid (e.g., air) temperature at the location of the fluid leak, which drop in temperature may alter the (e.g., reflection, filtering) characteristics of one or more nearby gratings  54 . For example, the drop in temperature may cause a nearby grating  54  to physically contract. This change in the grating characteristics may result in provision of altered filtered electromagnetic radiation received (e.g., detected) by the receiver  46  such that, for example, there is one or more wavelength shifts/differences between the actual receiver data and the expected receiver data. The magnitude of the wavelength shift(s) are indicative of a temperature at the grating(s)  54 , and may be used to predict a flowrate of the fluid leaking across the hatch-wall interface  30  based on the temperature. 
     Where the actual receiver data is the same as the expected receiver data, the processing system  48  may determine that the condition of the hatch-wall interface  30  is fully operational and serviceable. In some embodiments, slight fluid leakage across the hatch-wall interface  30  may be expected, acceptable and/or accommodatable by an aircraft cabin pressurization system. In such embodiments, the processing system  48  may also determine that the condition of the hatch-wall interface  30  is fully operational and serviceable where the magnitude of the wavelength shift(s)/difference between the actual receiver data and the expected receiver data is less than a first threshold. Where the magnitude of the wavelength shift(s)/difference between the actual receiver data and the expected receiver data is equal to or greater than the first threshold, but less than a second threshold, the processing system  48  may determine that the hatch-wall interface  30  is still serviceable, but no longer fully operational. With such a determination, the processing system  48  may provide a maintenance notification signal (e.g., an alert) such that future maintenance may be planned and performed. Thus, the aircraft  20  may finish its current flight (and possibly one or more additional flights) since the fluid leakage is caught/detected at an early stage. Where the magnitude of the wavelength shift(s)/difference between the actual receiver data and the expected receiver data is equal to or greater than the second threshold, the processing system  48  may determine that the condition of the hatch-wall interface  30  is no longer serviceable. With such a determination, the processing system  48  may provide a notification signal (e.g., an alert) such that (e.g., immediate or otherwise timely) action may be taken. For example, the aircraft  20  may be diverted to a closer airport or maintenance may be performed at the destination airport; but, deployment of oxygen masks may be averted. 
     The processing system  48  may also determine a predicted location of the fluid leak when that leak is detected as described above. For example, since each of the gratings  54 A-H within the optical fiber  42  is tuned for (e.g., configured to reflect/filter) an individualized/different wavelength (or wavelengths) of the electromagnetic radiation, the processing system  48  may analyze the receiver data to determine which grating  54  was most likely affected to cause the wavelength shift(s) in the actual receiver data. Maintenance personnel may thereby inspect a certain area of the hatch-wall interface  30  and the associated portion of the seal element  32  to determine what repair or part (e.g., seal element) replacement is needed. 
     As described above, the method  700  may be performed for each of the sensor systems  40  such that each of the hatch-wall interfaces  30  is monitored for fluid leakage. Each of the processing systems  48  of  FIG.  4    may be in signal communication (e.g., hardwired and/or wirelessly coupled) with a central processing system  58 ; e.g., a controller. This central processing system  58  may receive the notification signal(s) from the sensor system(s)  40 , and then relay notification information to a pilot and/or other personnel. The central processing system  58  may also or alternatively store the notification information for consideration (e.g., review, analysis, etc.) by, for example, a ground maintenance crew. Of course, in other embodiments, some or all of the sensor systems  40  may share a single central processing system  58  where the processing systems  48  (see  FIG.  5 ,  6   ) are integrated into the central processing system  58 . In such embodiments, however, the gratings  54  in each sensor system  40  may be discretely tuned such that the wavelength shift(s) may identify which one of the hatch-wall interfaces  30  is associated with the fluid leakage. 
     The second electromagnetic radiation described above includes the wavelength(s) of electromagnetic radiation that pass through the various gratings  54  within the optical fiber  42 . In such embodiments, referring to  FIG.  5   , the transmitter  44  may be located at the fiber first end  50  and the receiver  46  may be located at the fiber second end  52 . Such an arrangement may be implemented for various installations including, but not limited to, those where a longitudinal length of the optical fiber  42  is relatively short and both fiber ends  50  and  52  are open. However, in other embodiments, the second electromagnetic radiation may include the electromagnetic radiation that is reflected by the gratings  54 . In such embodiments, referring to  FIG.  6   , the transmitter  44  and the receiver  46  may both be located at a common fiber end  50 ,  52 ; e.g., the fiber first end  50 . Such an arrangement may be implemented for various installations including, but not limited to, those where the longitudinal length of the optical fiber  42  is relatively long and one of the ends  50 ,  52  (e.g., the fiber second end  52 ) is closed; e.g., capped. 
     In some embodiments, referring to  FIG.  8   , at least a portion or an entirety of the optical fiber  42  may be disposed along and outside of the seal element  32  at the hatch-wall interface  30 . The optical fiber  42 , for example, may be located next to and may extend longitudinally along an exterior surface  60  of the seal element  32 . The optical fiber  42  may engage (e.g., contact) the seal element  32 . Alternatively, the optical fiber  42  may be (e.g., slightly) spaced from and disengaged with (e.g., not contacting) the seal element  32 . 
     In some embodiments, referring to  FIG.  9   , at least a portion or an entirety of the optical fiber  42  may be disposed along and within the seal element  32  at the hatch-wall interface  30 . The optical fiber  42 , for example, may be integrated into material  62  of/a body  64  of the seal element  32 . 
     In some embodiments, referring to  FIG.  10   , at least a portion or an entirety of the optical fiber  42  may be disposed at (e.g., on, towards, etc.) an exterior side  66  of the hatch-wall interface  30 . The optical fiber  42 , for example, may be located closer to the exterior side  66  of the hatch-wall interface  30  than an interior side  68  of the hatch-wall interface  30 . The exterior side  66  of the hatch-wall interface  30  is next to or proximate an external environment  70  outside of the aircraft fuselage  22 . The interior side  68  of the hatch-wall interface  30  is next to or proximate an internal environment  72  inside of the aircraft fuselage  22 ; e.g., the aircraft cabin. 
     In some embodiments, referring to  FIG.  11   , at least a portion or an entirety of the optical fiber  42  may be disposed at (e.g., on, towards, etc.) the interior side  68  of the hatch-wall interface  30 . The optical fiber  42 , for example, may be located closer to the interior side  68  of the hatch-wall interface  30  than the exterior side  66  of the hatch-wall interface  30 . 
     In some embodiments, referring to  FIGS.  10  and  11   , each hatch-wall interface  30  may be associated with a single sensor system  40 . In other embodiments, referring to  FIG.  12   , one or more of the hatch-wall interfaces  30  may each be associated with a plurality of the sensor systems  40 A and  40 B. One of these sensor systems  40 A may be disposed at the exterior side  66  of the hatch-wall interface  30 , and the other one of the sensor systems  40  may be disposed at the interior side  68  of the hatch-wall interface  30 . The multiple sensor systems  40  may thereby provide redundancy to reduce or eliminate provision of false positives. 
     While various embodiments of the present invention have been disclosed, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the invention. For example, the present invention as described herein includes several aspects and embodiments that include particular features. Although these features may be described individually, it is within the scope of the present invention that some or all of these features may be combined with any one of the aspects and remain within the scope of the invention. Accordingly, the present invention is not to be restricted except in light of the attached claims and their equivalents.