Safety Analysis And Reliability Assessment For Power Supply System Of Trial-Flight Test Equipment Of C919 Airplane

A trial-flight is an important part for the type development of an aircraft.With the installation of test equipment,flight parameters and the working conditions of onboard systems and equipment are recorded to analyze and verify the adequacy of the aircraft type design.The safety for powering test equipment is important to a trial-flight and the warranty of airworthiness.The power supply system for trial-flight test equipment of C919 airplane uses the onboard power as the power source and powers the test equipment after a conversion.Though the system is not an airborne equipment in a strict sense,it still needs to meet certain safety requirements in response to the trial-flight.This paper minutely analyzes the structure and working principle of the power supply system,and makes a discuss of the influencing factors of system safety,then the failure rates of the main functional devices are estimated with a reference to GJB/Z 299C-2006 Reliability Prediction Handbook for Electronic Equipment.On the basis of that,a safety assessment is made with the FTA method and combined with the safety index,and distinguishing the four working modes of Double-Generator,Single-Generator,Double-Generator closing and emergency.Meanwhile,this paper also analyzes the reliability feature with system reliability tests data.Aiming at the zero-failure situation of dynamic working life tests of Type I Censoring with replacement,this paper investigates a failure-factor-based self-adaptive synthetic expected Bayesian(FSSEB)method.The FSSEB method defines a failure factor and structures its value model as the failure information source,meanwhile defines a self-adaptive coefficient to constrain the prior value and the E-Bayesian estimation of the reliability parameter for a pre-complement input,and then establishes a failure weight with the relative probability method to simulate the failure effect.Thus the introduction of the failure information is completed.In this paper,the mean life is taken as a target,and the mathematical estimation model is deduced.With the E-Bayesian evaluation as a comparison,the mean life assessment for the power supply system in Double-Generator working mode is performed.Meanwhile,the comparison with E-Bayesian evaluation on accuracy and robustness also shows that the FSSEB method has a more stable evaluation performance.