Safety assessments are a primary means of compliance for systems that are critical to safe flight and operation. Safety assessments proceed in a stepwise, data-driven manner. Functional hazard assessments are performed to identify the failure conditions associated with each airplane function, and system functional hazard analyses are performed for system-level functions.
The bottom-up verification starts with a safety analysis of the components of a system to ensure that single failures do not result in significant effects.
Combinations of failures are then analyzed to develop the probability of a failure and checked to ensure that the probability is commensurate with the criticality of the failure condition. Thus, the final definition and characterization of a safety-critical system is verified by the result of the analyses conducted during a safety assessment.