Study On System Safety Analysis Methods Of The Main Landing Gear System

With the improvement of the complexity of products, safety has gradually become a significant issue in the process of system development, manufacture and use. Especially for aviation, accidents usually result in serious personal injury and enormous economic losses. System safety analysis could efficiently improve products'safety. It runs through the whole phases of development and manufacture. In the process of system safety assessment, various safety analysis methods are used for qualitative and quantitative analysis to assure that the product under consideration satisfies the requirements of design and safety. However, there are some disadvantages in terms of dynamic system safety modeling and analysis for traditional methods. Dynamic Fault Tree and Petri Net are studied for dynamic problems in system safety analysis in this thesis, and the aircraft main landing gear system is analyzed as an example.System safety assessment process and system safety analysis method and its application are overviewed. According to the basic theory of Dynamic Fault Tree, the specific applications in some aspects are studied. A new logic gate is tried to optimaize the presentation and analysis of the special failure mode of dual components. In addition, how to introduce the result of Common Cause Analysis (CCA) into Dynamic Fault Tree is discussed in terms of model and arithmetic. To solve the problem that Markov model is not intuitive and easy to induce errors, it is studied that how to use Petri Net model to replace Markov model for system safety modeling and critical condition analysis. The relations of Petri Net and Fault Tree are addressed. For proving the applicability of new methods, they are used in system safety analysis of aircraft main landing gear system. The specific failure conditions of the system are proved to satisfy the safety requirements. Comparing with the results of traditional Fault Tree of wheel braking system, the applicability of Dynamic Fault Tree and Petri Net for system safety analysis of aircraft main landing gear system is proved. Additionally, from the views of description ability and the degree of intuitiveness of the models, as well as the result of analysis, the improvements and shortcomings of the new methods is discussed.