Preventing common-cause failures by partitioning software and hardware into isolated assurance domains.
An aircraft-level Catastrophic hazard does not automatically mean every component must be DAL A. Under ARP4754A Section 5.4, a Catastrophic function can be decomposed into two architecturally independent subsystems developed to DAL B, dramatically reducing development cost without compromising safety.
Regulators require formal proof that redundant channels cannot fail simultaneously from a single root cause (e.g., shared power supply, identical compiler optimization bug, or co-located wiring harnesses). Common Cause Analysis (CCA) enforces physical and logical segregation.