Research On The FMECA And FTA Of The Landing Gear System For A Certain Type Of Aircraft In Failure Analysis

As an important constituent part of the aircraft,aircraft landing gear system was the “bridge” and the “bond” to link the sky and the ground,being called the "feet" of the aircraft.It not only undertook the secure take-off and landing tasks but also provided support for the whole aircraft at both static and dynamic conditions on the ground.so it played an important role in secure completion of the task.During the aircraft landing gear system operation process,however,failures would inevitably occur.Therefore,it was necessary to analyze and recognize the failure of the landing gear system,in order to improve the maintenance efficiency,and ensure the safety and reliability of the landing gear system.Additionally,prevention of failure in advance could also reduce the failure occurrence.When failure occurred,realization of fast failure location and troubleshooting could allow the reduction of re-launch time.By taking the front landing gear system of a certain type of aircraft as the research object,this paper had analyzed the failure of the front landing gear system by utilizing the Failure Modes Effect and Critically Analysis(FMECA)and Fault Tree Analysis(FTA),which further provided basis for troubleshooting,maintenance plan development and weak link improvement.The following aspects were mainly researched:(1)The previously statistic data based FMECA analysis.The constituent and work principle of the aircraft landing gear system was learnt,the reliability block diagram of the task was drawn,the failure data was collected,the FMECA analysis of the front landing gear system was carried out,the FMECA report was output,as well as,the matrix graph of the failure mode criticality was drawn according to the national military standards.(2)Fuzzy FMECA analysis.In order to comprehensively consider the impact resulted from the probability of failure occurrence,the severity of failure and the complexity of failure detection on the degree of risk,the fuzzy FMECA risk evaluation model was established,the weight of the influencing factor was determined by utilizing the analytic hierarchy process,and the risk level of the failure mode was determined by utilizing the fuzzy comprehensive evaluation and the RPN method on the basis of the previously statistic data based FMECA analysis.And the risk evaluation order for each failure mode was obtained by performing the risk evaluation on each failure mode of the front landing gear system,and then,the corresponding maintenance measures by judging each subsystem and the overall risk and referring the judgment results,was proposed.(3)FTA analysis.Based on FMECA analysis,abnormal retracting operation of the front landing gear system was selected as the top event to give illustration and analysis.By FTA method,the failure tree model was established,so as to give qualitative analysis and fuzzy theory based quantitative analysis for the failure tree.It was obtained,the importance degree order for the fuzzy probability regarding on the bottom event was consistent with the statistic failure results approximately,which indicated the fuzzy theory based failure tree analysis conformed to the engineering practice.According to the analysis results and the actual situation,suggestions on maintenance measures to prevent the occurrence of faults are put forward.