Abstract:
A component trend monitoring system for monitoring the performance of components and comparing the performance with stored performance data to accurately trend and predict the failure of the components. The system includes computer chips attached to the various components, for receiving and storing historical and performance data about each component, and a processor for retrieving the stored data from the memory chips. The processor receives and analyzes the data against historical data for predicting failure based upon past trends within the historical data. The processor also provides a signal for impending failure of a given component.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims the benefit of U.S. Provisional Application Ser. No. 60/247,440 filed Nov. 9, 2000. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to a method and apparatus for tracking relative to time the performance, reliability and condition of line replacement units used on aircraft and other types of machines. 
   Auxiliary power units (APU) for aircraft may generally be gas turbine engines used on aircraft to supply pneumatic power and/or shaft horsepower when the primary propulsion engines may not be operating. Typically, as illustrated in  FIG. 1 , the APU  10  may be mounted in the tailcone  12  of the aircraft, though on some airplanes such as the Boeing 727, the APU may be mounted in the wheel well. 
   Referring to  FIG. 2 , one form of an auxiliary power unit to which the present invention relates may generally be denoted by reference numeral  10 . The APU  10  may include in flow series arrangement a compressor inlet  14 , a compressor  16 , a bleed port  18  for providing compressed air to the aircraft, a combustor  20  having a primary fuel nozzle  22  and a secondary fuel nozzle  24 , a turbine  26  and a gas exhaust  28 . The compressor  16  and the turbine  26  may be mounted for rotation on a shaft  30  that extends to and drives a gearbox  32 . Mounted to the gearbox  32  may be accessory components such as an electric generator  34 , a lube pump  36 , a fuel control unit  38  and a start motor  40 . When one of these components fails, it may be easily removed by detaching it from the gearbox  32  and replacing it with a new component that may be just as easily attached to the gearbox  32 . In many instances, these components may be attached/detached without removing the APU from the aircraft. For some configurations in order to attach/detach these components, the APU may have to be removed from the aircraft. In these cases, however, the replacing of the components may occur on the tarmac adjacent the aircraft. In either scenario, the component may be replaced without removing the aircraft from operation. Accordingly, these components are referred to as Line Replaceable Units, (LRU), as they can be replaced without taking the aircraft out of operation or off line. 
   In operation, as the shaft  30  rotates, air may be inducted through the inlet  14  and pressurized in the compressor  16 . Any required bleed air flows through bleed port  18  with the remaining air flowing into the combustor  20 . In the combustor  20  the air may be mixed with fuel and ignited to form a hot pressurized gas. This gas expands across the turbine  26 , causing the turbine  26 , shaft  30 , compressor  16  and gearbox  32  input to rotate which in turn drives the LRUs  34 ,  36 ,  38  and  40 . The expanded gas then flows through the exhaust  28  and out into the surrounding environment. The operation of the APU  10  is controlled by an electronic control unit (ECU), not shown, that may be remotely located from the APU  10  in the aircraft. 
   The APU has a data memory module (DMM) that collects and stores APU operational and performance data as well as the serial number of the APU. This data may be used for tracking the APU health and operational conditions. Some life cycle calculations may be made by the ECU and stored in the DMM. Data is manually collected from the DMM when the aircraft may be taken off line and into a repair and overhaul facility. 
   For cost and performance reasons, the ability to track the performance, reliability and condition of these LRUs may be important. However, these types of components may be very difficult to track in the field. The LRUs may often be replaced, exchanged, or even discarded when thought to have failed. 
   Current systems use the data stored in the DMM to try to predict the failure of LRUs by evaluating performance trends (trending) of the APU as a whole. However, trending the LRUs as part of the APU has not been very successful, as current systems do not account for or know a units current configuration. That is they do not have a way to detect when an old LRU has been replaced with a new LRU. Current trending systems look at operational parameters to track particular performance trends looking for changes over time. Current systems fall short when an LRU may be replaced because the new LRU will affect the APU performance trend. Although the data in the DMM may show a change in APU performance, it may not be evident why the performance data has changed. Currently, there is no way for the current trending systems to know that an LRU has been changed. In addition, current systems do not use trend monitoring for the individual LRU components. 
   As can be seen, there is a need for a trending system and method that is able to determine the exact configuration of the APU as well as provide a method for each of the LRUs to be individually trended. 
   Although the foregoing description pertains to the use of this invention for APUs, similar application and benefits exist for LRUs associated with propulsion gas turbine engines and other machines. 
   SUMMARY OF THE INVENTION 
   The present invention comprises a method and apparatus for determining the configuration of an APU as well as for performing predictive trend monitoring on the APU and its LRUs. 
   In one aspect of the present invention a memory chip may be embedded in each LRU. The memory in the memory chip may be addressed by system electronics or any computer via a data bus. During the build of the LRU, data that describes the component by serial number, part number, as-built performance, and other pertinent data may be loaded in the smart chip. During operation the system may keep track of the LRU usage (hours and cycles) as well as compare its current performance to its as-built performance. As-built performance being the performance of a new or refurbished LRU. 
   In another aspect, the present invention may also support monitoring software that will track and compare the LRU usage and performance to determine when it has failed or is about to fail. This process is called trend monitoring. In this case it may be considered a smart trend monitoring as not only may the performance of the individual components be trended against themselves, but also they may be trended to determine how well they are operating in the system. The information may be transmitted to a collection station or stored in the system for later retrieval. Knowing how the LRU is operating compared to its as-built performance may allow the trending software to alert the operator of a pending failure prior to actual failure. 
   In yet another aspect, the present invention may also reduce the chance for an unscheduled replacement that may also reduce the number of delays, thus reducing operational cost. Also, the embedded chip may collect usage hours and cycle data of the LRU that may be used to schedule repairs and for warranty purposes. 
   These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an illustration of an auxiliary power unit mounted in an aircraft; 
       FIG. 2  is a schematic cross-section of an exemplary gas turbine auxiliary power unit; 
       FIG. 3  is a schematic block diagram indicating the relational links between components of the system; 
       FIG. 4  is a logical decision flow diagram of the SDMM and LRU protocol; 
       FIG. 5  is a schematic diagram of transmission and use of data from the performance monitoring equipment; 
       FIG. 6  is a schematic diagram of the elements of the data monitoring and reporting system. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims. 
   Although a large number of machines may benefit from use of the invention, for purposes of illustration, the invention may be described as it may be implemented for an APU of an aircraft as shown in FIG.  2 . 
   The operational sequence for monitoring the LRUs may be described in conjunction with  FIGS. 2 and 3 . When the operator of an aircraft wants to start the APU  10 , a start command may be sent from the cockpit to the APU&#39;s electronic control unit (ECU)  50 . The ECU  50  runs a diagnostics sequence checking itself and all of the LRUs  34 ,  36 ,  38 , and  40  for static feedback just to assure there are no opens/shorts in the equipment. After the diagnostic check, the ECU  50  in turn sends signals to the starter motor  40  and fuel control unit  38  to initiate a start of the APU  10 . Mounted on each of the LRUs may be a computer chip  52  that communicates with a smart data memory module (SDMM)  54  that may be mounted in the APU  10 . The SDMM  54  may communicate with each of the chips  52  through a data bus  56 . 
   When the ECU  50  applies power to the SDMM  54  it may perform the same function as the DMM mentioned in the background section of this application. In addition, the SDMM  54  may also communicate with and read the memory of all of the chips  52  located with the LRUs  34 ,  36 ,  40 . These chips  52  may be located with any component where there may be a need to track usage or where there may be a desire to know when a component has failed or is about to fail. The present invention may be used in any system that uses components to control operation. 
   There may be two kinds of data stored on each chip  52 . The first kind of data may be data stored when the LRU is built, as-built data, which may include the part number, serial number, as built performance map (a number of performance points recorded during acceptance test), the build location, whether the part is a new or repaired part, the type of repair (if it is a repaired part), and any other data as determined necessary. The chip  52  may be programmed when the LRU is built or returned to the factory for repair. The programming may be done automatically when the Acceptance Test is run on the LRU, just before shipment. Acceptance Test may be the test run on a production LRU to assure that it will meet a specified level of performance before it leaves the factory. If the LRU fails the test, it may not be shipped. 
   The second kind of data that may be stored in each chip  52  may be from the SDMM  54  as data acquired during operation. The SDMM  54  may store data in each LRU&#39;s chip  52  during the power down sequence which data may include the hours accumulated, the number of starts accumulated, and the Built-in-Test (BITE) record. The BITE record may be a record of the results of the ECU&#39;s  50  Built-In-Test or BITE procedures. For example, when the ECU  50  may perform a BITE test it may determine that one of the LRUs had a short. The BITE record may then be transmitted to the SDMM  54  for it to be stored in the LRU&#39;s chip  52 . BITE fault date and time may also be stored. The chip  52  may also store other performance data as determined during the power down sequence or other operations. The SDMM  54  may read all chips  52 . Each of the chips  52  may be able to store at least 2 k bytes of data. 
   Referring to  FIG. 4 , the logical flow for the SDMM  54  of the present invention as it communicates with the chips  52  located with the LRUs may be as follows. In step  200 , the SDMM  54  may be programmed to look at the first two memory locations (not shown) where the part number and serial number for the LRU may be stored. In step  202 , the system may determine if this is a new LRU by comparing the part number and serial number with the previously stored data. The system may then determine if there are more LRU chips to read, at step  204 . If there are more LRU chips to read the system may proceed to read the next LRU chip. In the event that the system determines that the part number and serial number do not match with the previously stored data, the system may determine it is a new part and may upload all of the data stored in the chip at step  208 . Once again the system may query if there are more LRU chips to read, step  210 , and if so the system may proceed to read the next LRU chip. Once the SDMM  54  reads all of the LRU chips  52 , following the sequence above, the SDMM  54  may transmit the data to the ECU  50  at step  212 . 
   The ECU  50  may now know the serial number of the APU  10  and all of its LRUs  34 ,  36 ,  38 ,  40 . During APU operation, the APU  10  and each of the LRUs actual performance may be compared to their as built performance. The trending system may now trend the APU performance and the performance of each LRU over time and is smart enough to know if a part has been changed. 
   A smart trend monitoring approach may be used to determine if an LRU is about to fail by trending its current performance to its as built new performance. 
   A smart trend monitor system may have the ability to send an alarm or warning message to the operator to change the part, say at the next airplane non-flight period. Therefore, based upon the trend monitoring, the system may automatically notify the operators that a failure may be approaching. 
   Other benefits of the present invention may be that the chips  52  may contain all of the as built data as well as all the performance data for LRU operation in the field to provide a history of operation and failure. One of the biggest problems with monitoring LRUs is that there is no operational history (hours, cycles, fault record etc.) when they are returned to the shop for repair. Users may not know why the part was returned or the number of hours or cycles on the part. Typically, warranties on these parts are based on hours or cycles. Many of the parts may be tested upon return and found to be operational. Industry calls this event, No Fault Found (NFF). This may be because a parts performance, much of the time, may depend on the performance of other parts in the same system. The fuel system for example, has a fuel control, shut off valve, flow divider, atomizers, etc. A smart trend monitoring system may trend the parts as a system and trend each part against its as built new performance. 
   Referring back to  FIG. 3 , the data stored on the SDMM  54  may be sent by the ECU  50  to an aircraft communication addressing reporting system (ACARS)  60 . The ACARS  60  may transmit the data to maintenance personnel  62  at remote location. The maintenance personnel  62  may be able to utilize the trend monitoring data of the present invention to conduct real-time troubleshooting produce accurate LRU reports, and accurate estimations of spare parts needed. 
   Referring to  FIGS. 5 and 6 , the present invention may be employed on an aircraft  402 . The system may retrieve and store data based upon performance and use during a given time period. The time period may be a portion of a flight, a flight, a series of flights, or on-ground testing. The data from the system of the present invention may be retrieved by communicating, including wireless communication, with another computer for downloading the stored data. An engineer or maintenance technician at a flight line maintenance location  404  may retrieve the data for evaluation and transmission to ground station  412 . The trend monitoring data may also be transmitted using other systems such as the aircraft communication addressing reporting system (ACARS)  406 . The ACARS  406  may transmit data to a satellite  408  that in turns transmits the data to a fleet maintenance ground station  412  via antenna  410  for use by personnel to assess the data. 
   The present invention may help to predict failures, improve dispatch reliability, provide a quick response and improve the ability to plan for the storing of parts. The present system may also improve and optimize spare parts provisioning. 
   The usage and trend data updated by the ECU on the aircraft may compare data during and after operation. The present invention may allow for a programmed replacement of parts prior to failure and improved spares provisioning. The trend monitoring of the present invention may minimize false alarms and replacement of LRUs before necessary. 
   Elements of the system may also be used with an avionics information management system  508  which may be in communication with a central maintenance computer (CMC)  507  and ACARS  506  that communicates with a ground station. Non-volatile memory modules  510  may be embedded in high value LRUs  501 ,  502 ,  503 ,  504  with information monitored and transmitted to utility controllers where data may be collected and updated for readable data at repair/ATP time. Usage and trend data may be updated by electronic controllers onboard an aircraft and compared during operational use. The data may be used to schedule repair, for spares provisioning, and for trend monitoring to facilitate operating cost reduction. Small hand held computers  509  may also be used at ground stations for data collection from controllers. 
   The high value LRU&#39;s  501 ,  502 ,  503 ,  504  monitored may be actuator valves, electronic elements, APUs associated with engines  505  and other aircraft system elements. The data monitored may include part number, serial number and usage data, such as, operating hours, cycles/starts and performance data. The data monitored may allow for programmed replacement of parts prior to failure and for spares provisioning. Approximate trend analysis may allow for minimization of false alarm and nonfailed parts replacement. Analysis may include statistical based diagnostic evaluation and performance data used to define control limits. Events beyond limits for LRUs may be flagged for investigation and for improved maintenance planning. 
   It should be understood, of course, that the foregoing relates to preferred embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.