Safety Assessment Process for a Modern Helicopter with Fly By Wire Flight Control System

The work provides a methodological approach to the safety assessment process of a Fly-By-Wire/Flight Control System of a transport category rotorcraft. Starting from the review of the documents forming the guidelines for the safety assessment process for airborne systems and equipments, the phases of the process are described and practically applied giving an example. The attention is focused on the first phases of the safety assessment process. Once the rotorcraft-level and the system-level functional requirements are defined, a rotorcraft-level Functional Hazard Assessment is carried out for a particular function involving the Flight Control System. A system-level FHA is then carried out pointing out the failure conditions for two different Flight Control System architectures. To give an example about how to conduct the Preliminary System Safety Assessment, a Fault Tree Analysis for a particular system-level functional failure is performed on both architectures, pointing out the effects of different design choices on the safety and operative requirement.