Concept and Requirements for an Integrated Contingency Management Framework in UAS Missions

The rapidly expanding adoption of unmanned aircraft systems (UAS) for various applications warrants increasing importance of the adequate handling of off-nominal flight conditions. Strategies for contingency management have been explored in previous studies and have been identified as a necessary component in unmanned air traffic management (UTM). However, the integration of comprehensive contingency measures into the tactical management of UAS flights has not been widely addressed so far. This paper presents a reference implementation architecture based on deterministic and automated decision-making. The architecture contributes towards ensuring the operational safety of UAS missions and lays the foundation of a modular flight management framework which is able to handle multiple hazard scenarios with different levels of automation. Following a risk-based approach and considering the ongoing development of technologies that support contingency management in an UTM environment, a concept of operations is developed. In order to cover a wide range of off-nominal scenarios and to ensure seamless flow of information, a functional analysis of the system design and interfaces is performed. Moreover, an initial model of quantitative risk assessment is incorporated in the decision-making process to facilitate the resolution of contingency scenarios. Functional requirements are then formulated for a real-time onboard implementation and used for the design of the reference architecture. The requirements are refined through expert consultation and the novel advanced capabilities of the decision-making process are implemented in the open-source autopilot and flight stack \pmbPX4. The contingency management implementation is then tested using a real-time physics simulation environment. In particular, the suitability of a contingency procedure for landing on safe zones is evaluated through the simulation of an use case representing realistic operations in complex environments. Consideration of available UAS capabilities is identified as a key requirement in the development process of contingency management strategies. The results show that the reference architecture is technically feasible and suitable for further implementation of operational procedures towards fully autonomous contingency management.