The emergence of accidents in industrial and aerospace environments has increased with the increase of activities in this field and the use of machinery. In traditional systems, after accidents and irreparable damage occur, research is done to investigate the defects and their causes. But today, due to the existence of different methods of hazard identification and risk assessment, before the occurrence of accidents, it is possible to identify accident hotspots and critical areas and to prevent and control them. Reviewing the analysis of failure modes and their effects (FMEA) is one of the industry's common risk assessment methods. Its purpose is to analyze the failure to obtain a comprehensive repair program that leads to the continuation of the operation of physical assets. In this study, with the help of the FMEA method, the risk priority number of the Ilyushin-76 aircraft hydraulic system was calculated, and its critical parts were identified. Due to the shortcomings of the usual risk priority number in the FMEA method, side methods of aggregation of ideas and Schaefer evidence theory were used to calculate the risk priority number. Using these methods, involving probabilities in the expression of opinion, the results of determining critical components became closer to reality. From the results obtained from the study and evaluation of critical components by the two usual RPN methods and Schaefer evidence theory, nine highly critical components are obtained jointly.