Research On Technique Of Reliability Assessments For Civil Aircraft Products

Aviation industry is one of the most important hi-technology strategy industries in our county. The new ARJ 21(Advanced Regional Jet 21st) has already finished its assembly and flight test successfully; the C919 commercial aircraft project is also in progress. All these have been done is of great importance in improving the position in national economy and international power of our country's aviation industry. The reliability assessments for civil aircraft products are significant in the process of total aircraft's project demonstration, engineering research & development, production, consignation into use and maintenance. It can evaluate whether the productions'reliability reaching the original object, validate the rationality of reliability design, point out the productions'weakness and demonstrate direction in elevating the civil aircraft's design, manufacturing, technics and maintenance optimization. Therefore, Researches on technique of reliability assessment for civil aircraft productions are of great significance to develop our county's civil aircraft projects. With the background of the situation, according to the reliability information's characteristics gathering in the aircraft design and operation's process, this paper puts emphasis on the researches about the theory and technique of reliability assessments, at the same time we have developed practicable aircraft information database and reliability assessments system. The main research contents and conclusions include:(1) The reliability assessment method for civil aircraft productions based on small sample life information is proposed. According to the small sample reliability life information gathered during the aircraft's design and operation process, the paper has tested the hypothesis of distribution, proposed a fuzzy-bayes method fusing the experts experience information, evaluated the productions'life distribution and finally computed the reliability parameters; When there are no experts experience information or other information available, research on the reliability analysis with small sample life information is carried out by using Statistical Learning Theory in machine intelligence research fields. Under the circumstances of limited sample, the method can achieve high precision in the assessment, fully indicating the particular advantages in the reliability analysis of small sample.(2) Traditional reliability information is merely recorded the failure number and time. However the tests and operation of high-reliability and long-life civil aircraft products include accurate, ample performance degradation information related to the life closely. So, in order to make full use of the performance degradation data, a Support Vector Machine (SVM) based reliability method is established by modeling the degradation track, acquiring the degradation data, analyzing the relationship between the track and the life distribution, evaluating the products'reliability. This method can be used to analyze the high-reliability and long-life civil aircraft products on the condition of less degradation sample and has comprehensive applicability.(3) On the aspect of assessing complex systems of aircraft products, in order to fully mine the reliability information from all sources of databases, the reliability assessment technique based on the environment factor and integrated information entropy is proposed. The method fuse the test information gathered under different circumstances into equivalent test information of working circumstances and evaluate the reliability of aircraft products based on the systems integrated test information eventually. In this paper, the method is used in assessing the reliability of ARJ 21's flap operation system and has good effects through engineering practice.(4) The life and reliability management of civil aeroengine is an important work. In this paper, according to several aeroengine parameters, a combined prediction method named IA-PSO is brought forward to predicting the life on wing. Multiple single models was based in this method, Particle Swarm Optimization algorithm (PSO) improved by Immunity Algorithm (IA) was used to set weights for every single model which attended combing, and different kinds of information form different single models could be integrated by it. Based on the prediction, the distribution of the life on wing and its parameters can be achieved. Finally, a method which is used to control the life on wing is established.(5) According to the requirements of the projects this paper relied on, a set of reliability assessment system of aircraft products (RASAP) is developed by using the technology of advanced database and application in order to solve the problems of reliability assessments. The theory and methods including the developed system mentioned in this paper have received high estimation. The work provides convenient and practical methods and tools for the reliability assessments and maintenance optimization in the fields of our county's civil aircraft design and operation.