Requirement Generation for Highly Integrated Aircraft Systems Through STPA: An Application

Abstract

This Paper presents an approach to requirement generation for complex and highly integrated aircraft systems using System Theoretic Process Analysis, a hazard analysis technique that handles hardware, software, and human operators and integrates them in a unified process. The approach is illustrated using the interfaces of the air management system (engine bleed, cabin air conditioning, pressurization, and anti-ice) of a generic commercial aircraft. System Theoretic Process Analysis is applied first to identify undesired/unsafe system behaviors through a structured, top-down approach. Requirements are subsequently generated from the results of System Theoretic Process Analysis in order to handle these unsafe behaviors. Results from the application show that this approach allows systematically assessing the design space of the system starting from an early development phase and generating requirements to handle those properties that emerge from indirect component interaction and that often jeopardize the fulfillment of the high-level system goals. Human-machine interactions are also particularly well addressed by this methodology, integrating the human-factors process into the overall engineering process.