Civil Aircraft Airframe Direct Maintenance Cost Assessment

China is promoting the R&D in the aeronautics industry nowadays. The circumstance of this article is the cooperation project civil aircraft maintenance economics data analysis commissioned by one Chinese aircraft manufacturer. Based on this background, this research mainly focuses on the implementation of maintenance cost assessment in China in order to improve aircraft competencies worldwide. The mainly contents are as follows.1. For the direct maintenance cost estimate, based on the limitation of current estimation methods which don't fit circumstances in China, an improved K-means based CBR is proposed to help estimate the direct maintenance cost.This method uses the K-means to improve the performance in the retrieving phase. Then the nearest neighbor method is implemented to find the most similar case with the target case,and the introduction of case similarity is obtained based on information entropy assignment method. The weighted average method is also used in the modification phase of CBR. Finally the remaining of the case is determined by the similarity.2. For the direct maintenance cost evaluation, In the past the assessments based on a qualitative evaluation of investigations and experts' experience, lacking of scientific evaluation method. Because of the poor evaluation results from the previous methods, the analytic hierarchy process gray system fuzzy comprehensive evaluation method is proposed based on the theory of attribute importance, analytic hierarchy process and gray system theory.The researches mentioned above help build a complete and practical maintenance cost assessment system.