This paper present the design of a permanent-magnet starter-generator unit for aerospace applications from concept to implementation. Attention is placed on the required failure-rates, system architecture, power density, prototype implementation and experimental test-setup. Measures taken to realise the failure-rates are the design of an electrical machine which can operate under unbalanced short-circuit conditions, a short-circuit detection circuit and a dedicated hardware-protection layer. An increase in power density is investigated through the implementation of an integrated magnetic component based on a novel stacked PCB approach, while a high inertia turbine simulator was realised using a back-to-back electrical machine setup.@en