Comparative reliability analysis of electric aircraft versions for NASA’s X-57 based on Lz-transform method

Abstract

As the goals of air transport shift towards more-electric or all-electric airplanes, different drive train configurations have been explored recently. A major goal on the way towards the inclusion in commercial air traffic is high reliability. One of the experimental electric airplanes is NASA’s X-57 “Maxwell”, which consists of fourteen electric motors powered from a battery pack. The aim of this paper is to assess the reliability of the proposed design of the X-57 by using the Lz-transform approach, as well as to propose several alternative designs to its electric drive train, in order to use less vehicle mass on the motors and more on the battery pack, without sacrificing the original availability and expected performance, with a final goal to increase the flight range. The reliability analyses show that the replacement of X-57’s three-phase motors with six-phase ones greatly improves availability of the electric drive train due to the use of fault-tolerant electric machines. Additionally, all of the further proposed alternative designs have higher availability than the X-57. The alternatives with CHB inverter topologies generally achieved higher availability values and higher expected performance than the B6 variants. Finally, the use of a distributed propulsion system with smaller take-off motors leads to a motor-mass advantage compared to more conventional drive train designs.