Abstract: The airlines pay close attention to maintenance cost for efficiency improvement and consumption reduction.In this paper, basing on the theory of rough set, the problem of how to determine proper shop visit workscope before the aero-engine being removed is discussed.The key point is to obtain related rules between the on-conditional parameters and the performance of engine units.The uniformity of rough set and statistical methods are employed to find out the significance of each attributes by its knowledge entropy.The rules can be generated by determining the significant degree of each attribute.According to the experimental results, the proposed new method can improve the prediction accuracy for drawing up shop visit workscope.The method has been partly adopted by airlines, and it is proved to be helpful to reduce the costs of airlines.

Key words: civil airplane, maintenance costs, combination model, rough set