The authors have witnessed a notable surge in the number of designs and in the guidance material for electric and hybrid aircraft. FAA and EASA have continued to evaluate the safety of Propulsion Battery Systems (PBS), with a focus on thermal runaway containment testing. As a result, a harmonization white paper [7] was issued to provide a certification path for Thermal Runaway (TR) Hazards, followed by an EASA certification memorandum on the acceptable approaches for the certification of Electric/Hybrid Propulsion Systems (EHPS). Recently, an FAA Advisory Circular (draft) was issued for the “powered-lift” aircraft that feature these propulsion battery systems.
Despite the advances made by electric/hybrid aircraft manufacturers and the aviation authorities, there is still a missing piece of the puzzle. Mainly, engineering work still needs to be done to properly integrate the EHPS architecture to achieve safety objectives. The burden is still on systems engineering to propose their own methodology in absence of a standard that addresses the integration complexities of the EHPS.
In our previous paper, we outlined an approach for the hazard analysis of the battery system, with an emphasis on TR hazards [1]. In this paper, we will build upon this approach by outlining a PSSA methodology that serves to validate the EHPS architecture by addressing the novelties and the integration complexities between the PBS, EHPS, and the aircraft. This approach is designed to evaluate the robustness of the EHPS in achieving the safety objectives, by detailing a customized requirements validation process. With this approach, we can ensure that a correct and complete set of safety requirements will be derived no matter the aircraft configuration. With this “designing for safety” approach, or in this case: “integrating for safety”, we can be assured a clear pathway to certification.