Safety-oriented dynamic procedure modeling

Ensuring the safety of unmanned aerial systems (UAS) is a growing concern as their numbers grow increasingly fast. Regulatory bodies are in the process of tackling this problem by issuing standards and recommendations to be met by the UAS designers. The European Union Aviation Safety Agency (EASA) published the Specific Operations Risk Assessment (SORA). Among others, it requires that procedures are appropriately defined and designed. As it is, procedures are still widely found in the form of text-based documents, proving hard to analyse for safety. This makes it hard for UAS designers to validate their procedures and acquire flight authorizations from the relevant authorities. In this paper, we aim to facilitate this process. To that end, we expand our previous work on modeling procedures. We propose a clearly delineated methodology for modeling UAS flight procedures. We present the components needed to follow this methodology, as well as their implementation we performed in the AltaRica DataFlow (ADF) language. We also give increased consideration to dynamic behaviours compared to our previous work. This allows us to perform analyses that reveal more complex failure scenarios than we could previously identify. We illustrate this on a relevant fixed-wing UAS, for which we model, simulate and analyse three emergency flight procedures.