The rapid growth in availability and use of Unmanned Aircraft Systems (UAS) brings with it safety questions and significant challenges to the Federal Aviation Administration (FAA) and the aviation community. One of the key questions and challenges concerns the integration of UASs into the National Airspace System (NAS) and the path, criteria and processes that should be applied for their certification, to ensure their safe operation within the NAS. This paper discusses an ongoing project supported by the NASA Ames Research Center to develop a validation and verification (V&V) framework for model-based control systems (MBCSs) and adaptive control systems (ACSs). This framework incorporates multi-valued logic tools such as the Dynamic Flowgraph Methodology (DFM) and the Markov Cell-to-Cell Mapping Technique (CCMT) and supports the development of a risk-informed safety case for certification purposes. The AC 20-115C1 advisory circular recognizes adherence to DO-178C2 as an acceptable means, although not necessarily the only means, for showing compliance with the applicable airworthiness regulations for the software aspects of airborne systems and equipment certification. DO-178C itself, in the “Alternative Methods” chapter, discusses the use of an “assurance case” (also in other contexts referred to as “safety case”) to demonstrate that the system safety objectives are satisfied. An assurance case consists in essence of a structured and hierarchical logic framework that explicitly organizes and presents arguments to link specific factual and analytical evidence to the claims of compliance with the system safety objectives.
S. Guarro, M. Yau, et al, “Risk Informed Safety Case Framework for Unmanned Aircraft System Flight Software Certification,” Proceedings of the 2017 AIAA SciTech Forum, Grapevine, Texas, January 9-13, 2017