Modelling the risks remotely piloted aircraft pose to people on the ground

Regulations for remotely piloted aircraft systems (RPAS) should have a strong foundation in, and traceability to, the management of the safety risks. This paper describes a new approach for modelling the risks associated with RPAS operations near populous areas to support the development of regulations and safety cases. A review found that existing models do not provide a simple means for incorporating the wide range of technical and operational controls into the risk analysis process. A Barrier Bow Tie Model (BBTM) is proposed as it focuses risk analysis, evaluation, and decision-making activities on the practical devices, people, and processes that can be used to reduce risk. Existing literature and practical controls were reviewed and used to define the components of the model and a case study is used to exemplify its application. More than 50 practical controls were incorporated into the model. The template barriers, controls, and graphical nature of the BBTM facilitated a simple comparison of the two case study RPAS operations and a more structured approach to the setting of airworthiness requirements taking into consideration the wide range of technical and operational factors that can be used to manage risk. The model provides the linkage between a regulation, associated controls, and how the controls contribute to a reduction in risk, which is necessary for the adoption of a risk-based approach to the regulation of RPAS. The BBTM provides a generic framework that can be used to structure the development of safety cases for any RPA operation.