Extending PSSA for Complex Systems Professor

Preliminary System Safety Assessment (PSSA) is a key stage of the safety process in the civil aerospace community. It is identified in ARP 4754/4761 as the stage in the safety process concerned with validating systems architecture, and producing derived safety requirements on system components. A very similar approach has been adopted by EUROCONTROL for Air Traffic Management (ATM). The process in ARP 4754, and the associated guidance in ARP 4761 (on which the EUROCONTROL work is based) focuses on technical systems. However, modern aircraft systems and ATM are complex and involve computers, hence software, human operators (pilots or Air Traffic Controllers (ATCOs)) and procedures. Thus, to be effective, PSSA has to deal with people, procedures and software, as well as the more classical technical issues covered by current standards. Also, the analysis of human behaviour needs to deal both with success, e.g. correct mitigation of equipment failure, and failure, e.g. lapses in implementing procedures. The paper presents an approach to extending PSSA to deal with software, human and procedural issues being developed in collaboration with EUROCONTROL, and the current (European and US) activities to update ARP 4754.