Metric evaluating potentials of condition-monitoring approaches for hybrid electric aircraft propulsion systems

Abstract

Hybrid electric aircraft propulsion will become a necessity for general and commercial aviation in the near future to enable the achievement of ambitious objectives with respect to a reduction of emissions in air traffic. Furthermore, this technology is crucial to facilitate the introduction of new aircraft concepts such as electric vertical takeoff and landing (eVTOL) for personal air mobility. The advent of electrified propulsion systems for aeronautical applications raises questions concerning the reliability and the possibility of detecting faults of the propulsion chain before they become critical. Evaluating the influence of individual subsystems on reliability is necessary for decision making during condition-monitoring design. To address these questions, a reference hybrid electric propulsion system (HEPS) is defined and analyzed in terms of its possible failure modes and failure probabilities. A condition-monitoring system (CMS), applied to the subsystems of a hybrid electric propulsion system, is assessed with regard to its potential to reduce the probability of a total loss of thrust (TLOT). For the purpose of this assessment, a metric is developed which allows for a quantitative comparison of failure probabilities of the reference system with and without CMS, which offers a more intuitive approach on decision making during the design process. The results of this study showcase for which components of a hybrid electric propulsion system the application of CMS could potentially be beneficial.