How do you conduct a System Safety Assessment (SSA) for a new avionics system per ARP 4761?

System Safety Assessment follows ARP 4761 methodology: 1) Functional Hazard Assessment (FHA) identifies failure conditions and classifies severity (Catastrophic, Hazardous, Major, Minor, No Safety Effect). 2) Preliminary System Safety Assessment (PSSA) allocates safety requirements to functions using fault tree analysis (FTA) from top-level failures. 3) During design, Common Cause Analysis (CCA) examines Particular Risks, Common Mode Analysis, and Zonal Safety Analysis. 4) System Safety Assessment (SSA) validates achieved safety levels using Failure Modes and Effects Analysis (FMEA), Markov analysis for complex redundancy, and test/flight data. Quantitative requirements: Catastrophic <10^-9/FH, Hazardous <10^-7/FH, Major <10^-5/FH. Documentation supports certification per FAR 25.1309.