Functional Hazard Assessment of the Propulsion Control System Designed for a Small Hybrid Electric Aircraft

Abstract

This paper presents the Functional Hazard Assessment (FHA) of a Propulsion Control System (PCS) designed for a hybrid electric aircraft considering the Failure Conditions (FCs) that are novel due to the electrification of the propulsion system. It will be worked out whether these FCs are covered by current certification regulations. After defining the functionality, the FCs for a hybrid electric propulsion system are established, based on current standards and also the Working Group 113 (WG-113) recommendations. The FHA and Preliminary System Safety Assessment (PSSA) approaches are used to evaluate and improve the architecture of the control system. The system functions on propulsion level are defined and allocated to different subsystems. Their FCs and effects are then established. Based on the applicable standards and recommendations of WG-113, these effects are classified, and the Safety Requirements (SRs) are then defined. The FHA results include 23 FCs related to the hybrid system, some of which are not addressed by the current regulatory framework. In summary, this paper outlines how electrified powertrain systems will affect new propulsion architectures from a safety perspective and how the current regulatory framework and the work of the WG-113 could be improved by addressing new FCs resulting from the FHA. By suggesting SRs derived from the FHA, this paper also discusses what system/safety activities need to be undertaken in order to design a propulsion architecture that is compliant with the applicable certification documents.