How is a systems safety assessment (SSA) conducted for aircraft systems?

SSA per ARP 4761 demonstrates system safety for certification. Process: Functional Hazard Assessment (FHA) - Identify aircraft-level failure conditions and severity (Catastrophic, Hazardous, Major, Minor, No Effect); Preliminary SSA (PSSA) - Allocate safety requirements to systems using fault tree analysis, determine required DAL (Design Assurance Level); Common Cause Analysis (CCA) - Zonal safety (proximity hazards), particular risks (fire, lightning, HIRF), common mode analysis; System Safety Assessment (SSA) - Validate achieved safety using FMEA (Failure Modes and Effects), fault tree quantification. Safety objectives: Catastrophic <10^-9/FH, Hazardous <10^-7/FH, Major <10^-5/FH. Methods: Fault trees for top-down deduction, FMEA for bottom-up failure analysis, Markov for dependent failures. Documentation: System safety plan, FHA report, PSSA, CCA, SSA, culminating in compliance showing. Certification: DER review, FAA certification engineer approval.