Safety Assessment Using Behavior Trees and Model Checking

This paper demonstrates the use of Behavior Trees and model checking to assess system safety requirements for a system containing substantial redundancy. The case study concerns the hydraulics systems for the Airbus A320 aircraft, which are critical for aircraft control. The system design is supposed to be able to handle up to 3 different components failing individually, without loss of all hydraulic power. Verifying the logic of such designs is difficult for humans because of the sheer amount of detail and number of different cases that need to be considered. The paper demonstrates how model checking can yield insights into what combinations of component failures can lead to system failure.