Evaluating the reliability & availability of more-electric aircraft power systems

With future aircraft designs increasingly embracing the more-electric concept, there is likely to be a greater reliance on electrical systems for safe flight. More-electric aircraft (MEA) will have a greater number of electrical loads which are critical to the aircraft flight. It therefore is essential that the design of aircraft power systems embraces new technologies and methods in order to achieve targets for aircraft certification. The various design drivers (e.g. weight, space) for aircraft will also have to be considered when incorporating reliability into future MEA. This paper will investigate options for future platforms to meet reliability and availability targets whilst continuing to improve overall efficiency. The paper proposes a software tool that has the ability to determine the reliability of a number of potential alternative design architectures. This paper outlines present designs of such systems and how reliability is enhanced through the use of redundancy and back-up generation. The regulatory challenges associated with aircraft are summarised, including a discussion on reliability targets for various loads. Techniques for assessing the reliability of aircraft systems are described and simple examples of their application to aircraft electrical systems are provided. These examples will highlight the advantages and drawbacks attributed to each method and the reasoning behind the selection of these techniques on which an analysis tool can be based.