课程设计振动故障

航空工程学院航空发动机综合课程设计Core Vibration Higher Than 7.3 Units题目核心机振动值高于7.3个单位作者姓名赵冬福专业名称热能与动力工程指导教师尚永锋提交日期2011年月日答辩日期2011年月日中国民航飞行学院航空工程学院课程设计ABBREVIATIONSAPM ARINC Processing ModuleANI Analog InputBITE Build In TestCMC Centralized Maintenance ComputerCFMI CFM InternationalDMC Display management ComputerDIM Discrete Input ModuleECU Electronic Control UnitEMI Electromagnetic InterferenceFMECA Failure Mode Effects and Criticality Analysis FFCCV Forward Flange Compressor Casing vibration FADEC Full Authority Digital Engine ControlGPM General Processing ModuleLRU Line Replaceable UnitMCDU Multifunction Control Display UnitPSM Power Supply ModuleRFI Radio Frequency InterferenceRCC Remote Charge ConverterSFC Specific Fuel ConsumptionSPM Signal Processing ModuleCore V ibrations Higher than 7.3 UnitsTable of contentsChapter 1 Overview of CFM56-5C (1)1.1 General (1)1.1.1 The CFM56-5C series (1)1.1.2 The advantages of CFM56-5C (2)1.2 The main modules of the engine (2)1.2.1 Fan/Booster rotor (2)1.2.2 Fan/Booster stator (2)1.2.3 Fan frame (3)1.2.4 Compressor rotor (3)1.2.5 Compressor stator (3)1.2.6 Combustor (3)1.2.7 High pressure turbine (4)1.2.8 Low pressure turbine (4)Chapter 2 Engine Interface and V ibration Monitoring System (EIVMS) (4)2.1 General (5)2.1.1 Description (5)2.1.2 Operation (7)2.2 Component Location (7)2.3 System Description (8)2.3.1 engine vibration system (8)2.3.2 Power Supply (9)2.3.3 Interface (9)2.4 Operation/Control and Indicating (10)2.4.1 Engine Vibration Monitoring (10)2.4.2 Engine Vibration Maintenance (12)Chapter 3 VIBRA TION SENSORS (12)3.1 General (15)3.1.1 Component Location (15)3.1.2 System Description (15)3.2 Component Description (17)3.2.1 No.1 Bearing Vibration Sensor (17)3.2.2 FFCC V ibration Sensor (18)3.2.3 Remote Charge Converter (RCC) (18)Chapter 4 failure analyzing (21)4.1 The related functional block diagram (21)4.2 Analyzing the probable causes resulting (22)4.3 Carrying out FMECA on the basis of the causes (22)4.4 Drawing the failure tree of the fault (24)4.6 Troubleshooting flow chart (24)中国民航飞行学院航空工程学院课程设计4.7 V ibration monitoring and fault diagnosis method (26)Reference (27)中国民航飞行学院航空工程学院课程设计Chapter 1 Overview of CFM56-5C1.1 GeneralThe CFM56-5C series engine is an axial flow, dual spool, high bypass ratio, turbo-fan engine with fan and multistage compression systems driven by reaction turbines. The engine is designed for use with a long duct, forced mixed flow exhaust system. The single stage fan and 4 stage booster is driven by a 5 stage low pressure turbine. A 9 stage, variable geometry, high pressure compressor is driven by an air cooled single stage turbine. A full annular combustor with 20 duplex fuel nozzles distributes the fuel to provide the heat energy to drive the turbines with residual energy providing thrust.The accessory drive system extracts energy from the high pressure rotor to drive the engine and engine-mounted aircraft accessories. Reverse thrust for braking the aircraft after landing is supplied by an integrated system which acts on the fan discharge airflow.1.1.1 The CFM56-5C seriesThe principal operational differences between the CFM56-5C series engine models are summarized below:Table 1-1 CFM56-5C seriesCFM56-5C2 31,200 lbs (13,878 daN) 950CFM56-5C2/F 31,200 lbs (13,878 daN) 965CFM56-5C2/G 31,200 lbs (13,878 daN) 975CFM56-5C3/F 32,500 lbs (14,456 daN) 965CFM56-5C3/G 32,500 lbs (14,456 daN) 975CFM56-5C4 34,000 lbs (15,123 daN) 975Core V ibrations Higher than 7.3 Units1.1.2 The advantages of CFM56-5CCharacteristics:1. Lowest SFC of the CFM56 family.2. Quietest engine in its thrust class.3. High thrust-to-weight ratio to provide excellent takeoff performance for high-altitude and hot airfields.4.36,000 pounds of thrust demonstrated during ground testing.5. Second-generation FADEC.6. Long-duct, mixed-flow nacelle developed by CFM to provide significant noise attenuation, reduced fuel burn, and increased climb thrust.1.2 The main modules of the engineThe main modules of the engine are:-The fan-The fan and booster-The high pressure compressor-The combustor chamber-The low pressure turbine-The high pressure turbine-The accessory drive gearbox.1.2.1 Fan/Booster rotorThe fan rotor consists of one full diameter single stage fan and a smaller 4 stage booster for the core engine flow.The fan and the booster are mounted on a common internal concentric shaft driven by the 5 stage fan turbine. Two bearings support the fan assembly in the fan frame.1.2.2 Fan/Booster statorFixed stator vanes are provided for both the fan and the rotors. The fan casing, in which the fan stator is mounted, has provisions for blade containment forward of and in the plan of the fan中国民航飞行学院航空工程学院课程设计rotor. The casing is supported by the fan frame and also supports the accessory drive gearbox. 1.2.3 Fan frameThe fan frame is one of the major structural and aerodynamic components of the engine. Aerodynamically the fan frame forms the inner and outer flow passage of the fan and core airstreams.Structurally the fan frame functions are:-to carry inlet cowl loads-to support the fan casing, the two fan bearings and the core engine forward bearings-to house the accessory drive power take off gearbox and radial drive shaft-to contain the variable bypass valve between the booster and high pressure compressor-to support the transfer and accessory gearboxes- to provide mounting surfaces for the fan-stream acoustic panels.This frame also serves as the forward support for the high compressor.1.2.4 Compressor rotorThe compressor is a 9 stage axial flow assembly. The rotor consists of the stage 1 and 2 disks which form a spool, a separately attached stage 3 disk and a spool containing stage 4 - 9 disks. Stages 1, 2, and 3 disks have axial dovetail slots and stages 4 - 9 blades are retained in circumferential slots. All blades are individually replaceable without spool disassembly.1.2.5 Compressor statorAll 9 stages of the compressor stator are shrouded. The Inlet Guide V anes (IGV) and the first 3 stages of the compressor are variable. The casing is composed of two semi-cylindrical halves, permitting a quick access to the core engine compressor.1.2.6 CombustorA step diffuser is incorporated upstream of the combustor for reduction of the combustor sensitivity to the compressor velocity profile. The combustor can be replaced without disturbing the fuel nozzles. The combustor casing provides structural support for the combustor, the compressor Outlet Guide V anes (OGV), the High Pressure (HP) stator and shrouds, and the sealsCore V ibrations Higher than 7.3 Unitsfor the Compressor Discharge Pressure (CDP).1.2.7 High pressure turbineThe High Pressure Turbine (HPT) is an air-cooled single-stage high-energy turbine. Rotor blades are individually replaceable without the need for rotor disassembly or re-balancing.1.2.8 Low pressure turbineThe Low Pressure Turbine (LPT) consists of 5 stages of blades and vanes. The first stage nozzle vane is cooled and transfers cooling air for the high pressure and low pressure turbine disks. The LPT drives the fan rotor through the inner concentric shaft and is aerodynamically coupled to the high pressure system. The front flange of the LPT casing supports the A8 flange extension and the partial axial flow bulkhead.Fig.1-1 CFM56-5CChapter 2 Engine Interface and Vibration Monitoring System(EIVMS)2.1 GeneralThe Engine Interface and Vibration Monitoring System (EIVMS) have two main functions:-Engine interface-Vibration monitoring.The Engine Interface and Vibration Monitoring System (EIVMS) consist in:-One computer (EIVMU)-One separate Remote Charge Connector (RCC)2.1.1 DescriptionThe EIVMU contains:-One General Processing Module (GPM)-One Discrete Input Module (DIM)-One Signal Processing Module (SPM)-One ARINC Processing Module (APM)-One Power Supply Module (PSM)-Four relays(a) General processing moduleThe GPM is involved in all the EIVMU functions except in the transfer function.Most of the logics and all the Discrete Outputs (DSO) are processed by this board from Digital Input (DGI), Discrete Signal Input (DSI) or Analog Input (ANI).BITE data are centralized or GPM for the whole EIVMS.The GPM internally communicates with APM and SPM, but is always the slave in the communication. The GPM has also relations with all other boards (centralization of BITE). (b) Discrete Input ModuleThe DIM acquires all Discrete Inputs (DSI) for the EIVMS. It can be considered as an hardware extension of the GPM board which manages it.(c) Signal processing moduleThe SPM acquires all Analog Inputs (ANI), vibration inputs and processes corresponding data. This board receives accelerometer signal through the RCC.The SPM internal communication is only performed with the GPM.(d) ARINC processing moduleThe APM ensures the processing of all Digital Inputs (DGI) and Digital Outputs (DGO). In particular, the transfer function is fully performed through this board.The APM internal communication is only performed with the GPM thanks to a mail-box process.(d) Power Supply ModuleThe Power Supply Module (PSM) provides all necessary supplies for the whole EIVMS. Aircraft power supply (28VDC) is monitored in order to have a satisfactory behaviour in case of transient.(f) RelaysThree relays are necessary to switch the aircraft power supplies to the corresponding engine. Switching conditions can be software (from GPM) or hardware (direct link to ENG FIRE or ENG/MASTER switch OFF discrete inputs).1.ECU supply switchingThe two following conditions energize the relay R1:-One hardware condition (FIRE ON)-One processed condition (on ground, ENG/MASTER switch in off position for at least 15 minutes).Upon energization of the relay R1, the ECU power supply is cut.2. Igniter supply switchingThe following condition energizes the relay R2:-One hardware condition (ENG FIRE ON or ENG/MASTER switch OFF)Upon energization of the relay R2, the igniter power supply is cut.3.T / R supply switchingThe relay R4 is energized when the EIVMU receives Throttle in REV position from the throttle control unit.2.1.2 OperationThe EIVMU interfaces with aircraft computers and with the associated propulsion system to perform the following functions:-data concentration from the cockpit panels and various aircraft computers to the associated engine control-engine to engine segregation-airframe electrical supplies to engine control-internal processing of some engine related status signals needed by the related engine control system-Processing and monitoring of engine vibration signals.2.2 Component LocationEngine Interface and Vibration Monitoring Unit (EIVMU) are located avionics compartment.- 2 EIVMUS are left.- 2 EIVMUS are right.Fig.2-1 the location of sensorsFig.2-2 Location of EIVMSFig.2-3 the location of sensors2.3 System Description2.3.1 Engine vibration systemThe engine vibration system comprises per engine:-Two monitoring sensors (piezo-electric accelerometers) the No. 1 bearing vibration sensor and the Forward Flange Compressor Casing vibration (FFCCV) sensor-Two tachometers N1 speed sensor and N2 speed sensor- One Engine Interface and Vibration Monitoring Unit (EIVMU)- One Remote Charge Converter (RCC)2.3.2 Power SupplyThe engine vibration system is supplied through the EIVMU from the 3PP bus bar2.3.3 InterfaceThe EIVMU is an interface between the propulsion system and the aircraft.A Interface Signals between Propulsion System and EIVMUFor the vibration monitoring purpose, the EIVMU receives:-Two digital signals from the Electronic Control Unit (ECU) through ARINC 429 data bus ECUA and ECUB:N1 speed, label 045 (used as a back-up for the N1 speed sensor)N2 speed, label 344.-Three analog signals from the:N1 speed sensorNo. 1 BRG VIB sensor (or ACCLRM A) through the RCCFFCC VIB sensor (ACCLRM B) through the RCC.B Interface Signals between EIVMU and AircraftThe EIVMU receives digital signals through ARINC data bus from:-CMC bus CMCM, labels 040, 041, 042, 125, 126, 227, 233, 234, 235, 236, 237, 260, 301, 302, 303, 304 (ARINC 429)-PRINTER bus PRINTER, labels 234, 235, 236 or 237 (ARINC 740).The EIVMU transmits digital signals through ARINC data bus to:-DMC bus A1, labels 035, 135, 136 (ARINC 429)-CMC bus A1, label 356 (ARINC 429)-test plug in the 800VU bus A1, (ARINC 429)-PRINTER bus A2, labels 172 and 223 (ARINC 740).2.4 Operation/Control and IndicatingThe engine vibration system has two main functions:-monitoring-Maintenance.2.4.1 Engine Vibration MonitoringThe EIVMU processes by means of:-Two accelerometer signals No.1 BRG and FFCC VIB received through the RCCFig.2-4 the interface of EIVMU-One N1-dedicated speed sensor signal (one pulse per revolution included) or N1 speed message from ECU buses (as a backup)-One N2 speed message given by the ECU buses.The EIVMU processes:-ACCLRM A corresponds to No.1 BRG (Bearing) VIB sensor, while ACCLRM B corresponds to FFCCV (Forward Flange Compressor Casing Vibration) VIB sensor. Narrow band frequencyfiltering for both of these sensors allows to obtain the two vibration values for each N1 and N2 shafts. An unfiltered BB (Broad Band) measurement is also available for each accelerometer.-N1 vibrations are measured as a displacement in mils (1/1000 of an inch), while N2 vibrations are measured as a speed IPS (inch per second). N1 phase angle is also measured in degrees for balancing purposes.-MAX N1 narrow band VIB selection and normalization for display:The display between 0 and 5 units depicts a vibration between 0 and 5 mils (linear)The display between 5 and 10 units depicts a vibration between 5 and 25 mils (linear).-MAX N2 narrow band VIB selection and normalization for display.The display between 0 and 10 units depicts a vibration between 0 and 3 IPS(linear).-broadband vibration monitoring (inch per second) through a 20 to 500 Hz filter from both No.1 BRG and FFCC VIB-N1 (DEG) phase and displacement (mm inch) from both No.1 BRG and FFCC VIB-N1 and N2 advisory level exceed from MAX of No.1 BRG and FFCC VIB.The N1 and N2 digital vibration values are:-in green color in normal operation-in green pulsing color (only one advisory level), if N1 or N2 engine vibrations exceed 5.7 units and 5.6 units for N2.-Besides the maximum values of the different vibratory measurements encountered during the flight, the EIVMU also processes and stores the cumulated exposure time above "long term operation levels".This exposure time is the sum over the whole flight of all time periods during which at least one "long term operation level" has been exceeded.The "long term operation levels" are fixed at:-20 mils for N1 vibrations-2.4 IPS for N2 vibrationsThere is no specific relationship between max flight values and long term exposure time. LONG TERM EXPOSURE: 0S (zero seconds) means that the "long term operation levels" have not been exceeded.Each of the leg records includes the measurements mentioned above at the moment when the vibration level shown in the record heading reached its maximum during the leg.Fig.2-5 the line of N1 VIBFig.2-6 the line of N2 VIB2.4.2 Engine Vibration MaintenanceThe maintenance tasks are divided into the following main parts:-normal modeSome specific tasks can be activated, in addition to the failure detection. The LRUs and wiring failures specific to vibration detected by the EIVMU are listed below.- Menu mode.(1) Normal modeThe specific tasks are:-max. flight vibrations acquisition-frequency analysis with printing of the results, by direct specific input and output buses linked to the printer-monitoring of broadband level exceed.-monitoring of maintenance level exceed.- Acquisition of 8 sets of points in predetermined conditions for engine trim balance.(a) Max. flight vibrations acquisitionThe EIVMU stores, for each flight and for N1 and N2 vibrations, the max vibration levels.The Max. N1 VIB, and Max. N2 VIB, from No.1 BRG VIB and FFCC VIB sensors are processed during the flight (phase 6) and are available through the MCDU in menu mode for the last 8 flights.(b) Frequency analysisThe frequency analysis (between 1 and 500 HZ by step of 4 HZ) is a semi-graphic print which is done if the broadband threshold level is exceeded or if required on the MCDU before flight (for given conditions).(c) Monitoring of broadband level exceed(d) Monitoring of maintenance level exceedThe EIVMU monitors whether the N1 NB and N2 NB vibrations from the No.1 BRG and FFCC VIB have reached a maintenance level:N1 maintenance level = 6 Mils for all N1 rangeN2 maintenance level = 1,7 IPS for all N2 range.(e) Acquisition of 8 sets of points in predetermined conditionsAcquisition of phase and displacement in stabilized flight conditions allows to rebalance the engine fan.(2) Menu modeThe following tasks can be activated:-ground scanning and integral test of the system-discrete input and output status-frequency analysis demand-max flight vibration displayChapter 3 VIBRATION SENSORS3.1 GeneralThe Remote Charge Converter (RCC) performs the amplification and the conditioning of the vibration pick-up signals from the No.1 bearing vibration and the forward flange compressor casing (FFCC) vibration sensors (respectively ACCLRM A and B), and transmits the signals to the Engine Interface Vibration Monitoring Unit (EIVMU).3.1.1 Component LocationA No.1 Bearing Vibration SensorThe accelerometer part of the vibration sensor is not visible externally. It is located inside the fan and booster section at the 9:00 o'clock position (aft looking forward) on the No.1 and No.2 bearing support near No.1 bearing.The sensor cable is routed on the No.1 and No.2 bearing support, then through the fan frame from which it comes out at the 3:00 o'clock position (ALF) as a 3-pin receptacle.B FFCC Vibration SensorThe FFCC vibration sensor is installed at the 4 O'clock on the front flange of the compressor casing, and is connected to 6 o'clock junction box by a harness.C Remote Charge Converter (RCC)The RCC is located at the 3:00 o'clock position on the fan case (ALF), above the ignition exciters.3.1.2 System DescriptionThe vibration sensor system is made of:-One No.1 bearing vibration sensor-One FFCC vibration sensor-One RCC.Fig.3-1 the location of V ibration unitsA No.1 Bearing Vibration SensorThe No.1 bearing vibration sensor permanently monitors the vibrations from the No.1 bearing. It is also used for trim balance operations.B FFCC Vibration SensorThe forward flange compressor casing (FFCC) vibration sensor is used in conjunction with the No.1 bearing vibration sensor.C Remote Charge Converter (RCC)The RCC is the engine equipment, interfacing with the EIVMU and up to the No.1 BRG VIB and FFCC VIB sensors.Its main function is to condition (Integration in speed) the two piezo-type accelerometer signals and to amplify these preconditioned signals to send them to the EIVMU.3.2 Component Description3.2.1 No.1 Bearing Vibration Sensor(1)DescriptionFig.3-2 Sensor wiringThe No.1 bearing vibration sensor assembly is made of the following items:-One housing including:One accelerometerOne bracket with 2 holes ensuring housing attachment to the No.1 bearing support with 2 bolts -One semi-rigid cable including:Two conductors inserted in an inner sheath and an outer sheath.Two metal tubes to supply cable rigidity.One metal plate for cable attachment to the forward flange of the fan frame mid-box structure. Five shock absorbers to guide and dampen the cable in a tube through the fan frame strut No.3. One 3-pin connector at one end provided with a nut for connector attachment to the fan frame. Four clamps for tube attachment to the fan frame No.1 bearing support.(2) OperationThe sensor is of the piezo-electric type. It includes a stack of piezo-electric discs placed between a mass and a base. When the accelerometer is subjected to a vibration, the mass exerts a variable force on the discs and so generates a potential difference directly proportional to the acceleration in a certain frequency range. The analysis of the signal delivered by this potential difference enables identification of vibration characteristics of the monitored part. The accelerometer sensitivity is 100pc/g.Fig.3-3 No.1 Bearing Vibration Sensor3.2.2 FFCC Vibration Sensor(1) DescriptionThe FFCC vibration sensor consists of a hermetically sealed housing that encloses the sensing element. A flange with two holes is provided to attach the housing to the engine. One electrical connector at the end of the semi-rigid harness provides the interface with a harness to the RCC.(2)OperationThe sensor is of the piezo-electric type.A piezo-electric material generates electrical charges when it is submitted to a mechanical stress. An inert mass is attached to a piece of piezo-electric material. When the assembly is submitted to vibrations, the inertia of the mass generates mechanical stresses in the piezo-electric material. It is therefore possible to collect an electrical signal the frequency and intensity of which is representative of the vibration level to be measured.3.2.3 Remote Charge Converter (RCC)(1)DescriptionThe fan case installed RCC is vibration isolated by four dampers. It consists of:- Two connectors A and B which receive input accelerometer signals from the No.1 BRG VIBand FFCC VIB sensors.Fig.3-4 FFCC V ibration Sensor-One connector C which sends output signals to the EIVMU.-a grounding braid which provides its case ground reference.-Two identical processing channels featuring:One RFI input filter which protects the charge converter against Radio Frequency Interference (RFI) and Electromagnetic Interference (EMI).One differential and symmetrical charge converter which transforms the charge input into a voltage proportional to acceleration.One integrator which converts the acceleration signals into a signal which proportional to velocity.One voltage modulator stage for output of the vibration signal (velocity terms) and power supply input for the circuit.One RFI output filter which protects the Remote Charge Converter against the RFI and Electromagnetic Interference.The RCC features a common circuitry (BITE system) which consists of:-A BITE demodulator.-A BITE level control which simulates an acceleration signal to test the RCC.Fig.3-5 Remote Charge Converter (RCC)(2) OperationThe electronics of the RCC performs the amplification and the conditioning (integration in speed) of the vibration pick-up signals from the No.1 BRG VIB and FFCC VIB sensors, and transmits the signals to the EIVMU.The two analog vibration inputs are fed into the RCC. This charge signal is first voltage converted, then amplified and integrated to transform the vibration signal fro m acceleration to velocity. In order to transmit the signal to the EIVMU through the power line of the RCC (10 V, 6 mA source), it is voltage modulated.An auto-test, triggered by the EIVMU and sent to the RCC over the transmission line, allows the EIVMU to check the proper function of this remote device.The RCC handles the following main functions:-Accelerometer interface.-Test of the remote charge converter.Chapter 4 failure analyzing4.1 The related functional block diagramThe No.1 bearing vibration sensor permanently monitors the vibrations from the No.1 bearing. It is also used for trim balance operations.NO.1 BRG VIB sensorFFCCVsensorRCCEIVMUDMC ECAMFig.4-1 Signal transmission chartThe forward flange compressor casing (FFCC) vibration sensor is used in conjunction with the No.1 bearing vibration sensor.The RCC is the engine equipment, interfacing with the EIVMU and up to the No.1 BRG VIB and FFCC VIB sensors. Its main function is to condition (Integration in speed) the two piezo-type accelerometer signals and to amplify these preconditioned signals to send them to the EIVMU.The piezoelectric acceleration sensor is using some substances such as quartz crystal of piezoelectric effect, accelerometer be in vibration, the quality of the piezoelectric element with the force changed also. When measured vibration frequency is far lower than the natural frequency of the accelerometer is measured by the change and force is directly proportional to the acceleration. The piezoelectric accelerometer during the test has the obvious directivity.From the above analysis, we can draw a diagram of the engine vibration system function structure as follow:Engine vibration systemVibration sonsers system EIVMU N1 speedsonserN2speedsonserNO.1VIB sonser FFCCV VIBsonserRCCMonitorvibrationfrom NO.1Trim balanceMonitor vibration from N2As backupfor NO.1VIBsonserfilter amplifierVoltagemodulator BITEOver voltage &EMI suppressorAnalog moduleBalancing moduleData processingmodule Fig.4-2 functional block diagram of vibration4.2 Analyzing the probable causes r esultingCore Vibrations Higher than 7.3 Units may be caused by three reasons:1.Vibration sensors2.Wiring3.EIVMUVibration sensors-Crystal material or accelerometer.RCC failure.Wiring-short circuit or open circuit.EIVMU fault.4.3 Carrying out FMECA on the basis of the causesTable 4-1 V ibration system FMECA of table(1) (2) (3) (4) (5) (6) (7) (8) (9)sequence number Components namefailuremodefailurecausetaskcycleFailure Impact probability ofoccurrenceSeverity composite ratingpreventivemeasuresitself On oneleveloverallunit1 wires corrosion Break,short-circuitall scrapAffectsignaltransmissiondisabler C Ⅳ4C inspection2 EIVMU ProcessingsystemfaultEIVMUfailure allfailure offunctionV ibrationmonitoring andProcessingCompromisesafetyD Ⅲ3D Bite3NO.1VIBSONSERAccelerometerfailureOrCrystalmaterialsfailureNO.1VIBSONSERfailure all scrapVibrationdetectionCompromisesafetyB Ⅳ4B inspection4 RCC InternalcircuittofailuresRCCfailure allfailure offunctionsignalconditioningCompromisesafetyD Ⅲ3D Bite5FFCCVVIBSONSERAccelerometerfailureOrCrystalmaterialsfailureFFCCVVIBSONSERfailureall scrapVibrationdetectionCompromisesafetyB Ⅳ4B inspection4.4 Drawing the failure tree of this faultVibration sensorsCore vibrations higher than 7.3unitsWiringEIVMUX6X5X7X2X1X3X4Fig 4-3 failure treeX1-damaged pins; X5-RCC failure;X2-connectors oxidation; X6-EIVMU internal system failure; X3-Accelerometer lose effectiveness; X7-EIVMU connectors; X4-Crystal material performance decline;4.6 Troubleshooting flow chart Fault Isolation -Test EIVMU-If no EIVMU CMS fault message is present and max flight vibs confirms vibration above 2.2 IPS:-check vibration sensors installation and wiring connectors and receptacles from vibrations sensors to EIVMU. If the check is not correct: -repair or replace as required.。