FUELEAP Model-Based System Safety Analysis

Abstract

NASA researchers, in a partnership with Boeing, are investigating a fuel-cell powered variant of the X-57 "Maxwell" Mod-II electric propulsion aircraft, which is itself derived from a stock Tecnam P2006T. The "Fostering Ultra-Efficient Low-Emitting Aviation Power" (FUELEAP) project will replace the X-57 power subsystem with a hybrid Solid-Oxide Fuel Cell (SOFC) system to increase the potential range of the electric-propulsion aircraft while dramatically improving efficiency and emissions over stock internalcombustion engines.Our FUELEAP safety analysis faces two primary challenges. First, the Part 23 certificated Tecnam P2006T is undergoing significant modifications to host the hybrid electric-propulsion system, and the challenge is to assure that the safety inherent in the stock aircraft (and subsequently in X-57 Mod-II) is not compromised by changes in avionics, aircraft structural loading, weight and balance, or other considerations. Secondly, because the SOFC power system has little (if any) relevant in-service precedent, our challenge is to assure that we identify and mitigate all reasonably plausible hazards introduced by unique FUELEAP equipage.We are investigating and utilizing Model-Based Safety Analysis (MBSA) methods to help us address these FUELEAP safety challenges. We captured aircraft-level system hazard conditions using instances of a SysML hazard block via aircraft-level Functional Hazard Analysis (FHA). Then, using SysML models of the FUELEAP architecture, we related the hazard conditions to initiating system events and possible mitigations, such as design architecture modifications or operational constraints. We are continuing to define our approach to MBSA by developing a component-by-component inventory of local failure modes and tracing their possible contribution to hazard conditions. Finally, we are applying an argument-based approach to FUELEAP assurance. Through a FUELEAP "safety case," we are providing an explicit argument for FUELEAP safety by associating assurance evidence with overarching safety claims through a structured argument.

Evaluation of Off-Nominal Performance and Reliability of a Distributed Electric Propulsion Aircraft during Early Design

“…Hasan et al [23] and Hemm et al [24] utilized modeling and simulation tools to gain additional knowledge regarding hazard severity and probabilities while focusing on the operational safety paradigm. Papathakis et al [25] and Woodham et al [26] conducted safety assessments of novel electric propulsion technologies. However in all these, variants of traditional methods like FTA and FHA have been utilized with subject matter expert knowledge to conduct safety assessments of novel aircraft technologies.…”

“…In addition to the novel technologies being tested with the X-57 program, of interest in the present work are the tools and methods used to conduct safety analysis of such transformational aviation concepts. Research in this direction available in literature points towards the utilization of traditional methods to assess safety [25,26,45]. Having multiple propulsors, the effect of one or more propulsors failing must be considered to assess the safety of the aircraft.…”

Design and Performance of a Hybrid-Electric Fuel Cell Flight Demonstration Concept

“…This, combined with the battery, provides enough performance for the aircraft to maintain level flight or shallow drift-down performance, giving the operator more options for an expedited landing. These and other situations are discussed in the companion papers by Papathakis et al [5] and Woodham et al [7].…”

“…Finally, Section IV summarizes the results of this research. Other companion papers include: a more detailed description of the power system design [4], electrical integration of this power system into the X-57 [5], thermal cycle testing of SOFC hardware to assess suitability for aviation operations [6], system safety analysis of the FUELEAP X-57 demonstrator concept [7], and the use of model-based systems engineering frameworks to aid in the development of future demonstrator concepts [8].…”

NASA concept vehicles and the engineering of advanced air mobility aircraft

“…NASA commissioned several investigations to contrast major design differences of UAM aircraft and explore the safety and reliability implications from the perspective of vehicle design, propulsion architecture and flight dynamics and control [32,[68][69][70][84][85]. The industry is pursuing the issues of UAM aircraft safety [93][94][95], particularly since EASA's issue of special conditions for VTOL certification and the proposed means of compliance [96][97]. EASA SC-VTOL-01 establishes certification criteria for vertical takeoff and landing vehicles with unique propulsion and control architectures, including distributing the flight controls and electric propulsion elements.…”