航空機 電子裝備의 運用壽命資料分析을 통한 信賴性 豫測評價 및 活用 硏究
viii, 101 p.
Operational Reliability MFTBF Electronic Equipment;
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Aerospace industry manufacturer has to assure customer reliability requirements and life time test specifications. Generally, the system reliability, that is the life of system, is to be predicted and verified through the design process. In aerospace industry, reliability of electronic equipments of military aircraft is predicted by using military specification. But the specification has not been revised since 1995. So some alternatives, such as SR-332, 217PLUS, etc., are suggested. In aerospace industry, MTBF(Mean Time Between Failures) and MFTBF(Mean Flight Time Between Failures) are generally used for reliability measure. In case of Korean military aircraft, generally MFTBF of electronic equipments is predicted by MIL-HDBK-217F and MIL-HDBK-338. However, the predicted MFTBF by military standard has a wide discrepancy to that of real-world operation, which leads to overstock and increase operation cost. In this thesis, reliability prediction specifications of aerospace electronic equipments are reviewed and compared by operational reliability data. Also reliability evaluation and improvement process of aerospace system is developed using operational data and reliability cost index is suggested. This study is composed as follows. First, reliability measures of repairable system including that of aerospace system are reviewed. Also reliability prediction specification and calculated method of electronic equipments are shown. Second, the process and method of MIL-HDBK-217F are compared with those of SR-332. Also the reliability prediction methods of aircraft electronic equipment using MIL-HDBK-217F and other aircraft usage data are investigated. The results show that predicted reliability of the equipment using MIL-HDBK-217F is more conservative (underestimated) than the reliability of that using other aircraft usage data when it is compared with field data. Third, this study analyzed operational data of aerospace electronic equipments. Operational MFTBF, which is calculated from operational data, is compared with predicted MFTBF calculated conventionally by military standard. In addition, failure rate trend is investigated to verify reliability growth in operational data. The investigation shows that failure rate curve from operational data has some pattern with decreased failure rate and constant failure rate. Finally, ORCI(Operational Reliability & Cost Index) is developed using Operational Reliability Data. Also KOREIP(KAI's Operational Reliability Evaluation and Improvement Process) is developed to find the items for design change and to improve reliability of aerospace equipments.