Research On Risk Assessment Method Of Flight Test Of Civil Aircraft Flight Control System

Flight test is a complex system engineering,its purpose is to verify the safety of the aircraft.Flight control system is the key system to ensure the safe operation of civil aircraft and improve its operational reliability.Flight test should be carried out in real environment to verify the working state,function,logic and performance of flight control system.It is of great significance for the safety of civil aircraft flight test to study the flight test risk assessment method of civil aircraft flight control system and establish the corresponding risk assessment process.The structure and function of the fly-by-wire flight control system,high lift system and automatic flight control system of the civil aircraft flight control system are studied,and the main failure modes of the flight control system are analyzed.The requirements and validation contents of flight test for flight control system are determined,as well as the work contents in three stages: research and development flight test,validation flight test,function and reliability flight test.The regulations of flight test validation of fly-by-wire flight control system,high lift system and automatic flight control system are analyzed,which lays a foundation for the establishment of flight test risk assessment process and evaluation method of civil aircraft flight control system.Based on the theory of risk assessment and the requirements of flight test risk assessment of civil aircraft flight control system,the flight test risk assessment process of civil aircraft flight control system is established,which is divided into three stages: before flight test,during flight test and after flight test.The initial risk assessment and detailed risk assessment are carried out before flight test.The process of flight test risk assessment in different stages is determined,and the risk assessment methods and selection principles in each analysis stage are studied.Referring to the airworthiness regulations and standards related to risk assessment,combining the analytic hierarchy process and the gray-fuzzy comprehensive evaluation method,the probability index of flight control system test risk is calculated,and then the consequence severity index of flight control system test risk is calculated by combining the analytic hierarchy process and the fuzzy comprehensive evaluation method.Based on these two indices,risk assessment matrix and ALARP risk acceptance principle are used to judge the risk level of flight control system test risk events.The Bayesian network technology based on probabilistic risk analysis is applied to flight test risk assessment of flight control system.Taking G650 flight test accident as an example,the Bayesian network flight test risk assessment model based on fault tree is established by using the Bayesian modeling software GeNIe,and the quantitative probability reasoning calculation is carried out to find out the main causes of flight test risk.By comparing the fault tree method with Bayesian network model,the effectiveness and advantages of risk assessment method based on Bayesian network model are verified.The method and process of flight test risk assessment for civil aircraft flight control system proposed in this paper can effectively maintain and enhance the safety of civil aircraft during flight test.