The aerospace industry has unique requirements for product / fleet safety and reliability, therefore, strict procedures and analyses have to be carried out for design of aerospace grade systems.
Standards and regulatory requirements guide the safety analysis process, including risk analyses and expensive tests. This drives up the cost of aerospace equipment.
Another outcome of the complex process is long design time and service cycles that create obsolescence challenges. Aircraft design time from initial concept to the point of airworthiness certification can exceed a decade. During this time, production of many components is stopped, and replacements have to be found, tested and certified.
Furthermore, expensive spare parts with long procurement times require careful planning of fleet logistics.
Therefore, safety, reliability and maintainability assessments during the design process are crucial for optimal product design, reducing cost, risk, and time to market.
A key term in aerospace functional safety analysis is Design Assurance Level (DAL) (sometimes referred to as Development Assurance Level). DAL is defined in standards DO-178B and DO-254. DAL is the aerospace variant of Safety Integrity Level (SIL) which is defined in IEC 61508. DAL requirements are defined for software and hardware based on the risk that software or hardware failures may pose.
Risk may be reduced by mitigating failure modes with potential severe effects, adding redundancies, fault tolerance, and Built In Tests (BITs) for fast failure detection and isolation.