A Comprehensive Design and Trade-Off Method for Integrating Safety and Operational Reliability Requirements

Abstract

The design of civil aircraft must simultaneously meet safety objectives mandated by certification authorities and operational reliability objectives expected by airline customers. In practice, the derivation of these two types of objectives remains disjointed: operational reliability is typically addressed through statistical methods to establish aircraft-level targets and allocate them downward, whereas safety requirements are derived using the structured process outlined in SAE ARP4761. This separation results in redundant analyses, inconsistent requirements, and challenges in achieving synergistic design optimization. This paper proposes an integrated design methodology that adapts the SAE ARP4761 safety assessment process to determine and allocate operational reliability requirements. The proposed framework enables traceable, architecture-driven allocation of both safety and reliability targets from the aircraft level down to the component level. It provides design teams with a unified workflow, reduces redundant effort, and enhances consistency between safety and reliability engineering.