Abstract:

To solve the missing problem of FTA and FMEA,a new safety analysis modeling and numerical solution method is proposed based on FMEA,named FMBD (failure mode block diagram). This method obtains the failure modes of the airborne equipments through FMEA,and establishes failure mode block diagrams depending on devices,working priniciples and relationships between device parts. By using FMBD method,an expression is proposed to calculate the failure rate. Compared with FTA method,the FMBD method not only simplifies the safety analysis process,but also overcomes the cut set omissions of FTA. The accuracy of failure rate estimation is improved. FMBD method is introduced into safety analysis of OPU,which is an airborne equipment. Through
safety analysis of this equipment,some modifications of hardware design are proposed. After modifying,the security of OPU hardware has been greatly improved,and the preallocated development assurance level has been met. Through all these works,the feasibility and accuracy of this method get well verified. This method can also be applied to all levels of failure rate analysis of aircraft systems,offering new path for aircraft safety analysis.

Key words: airborn equipments, FMEA, FMBD, safty assessment