A review of the concept of autonomy in the context of the safety regulation of civil unmanned aircraft systems.

Civil aviation safety regulations and guidance mate- rial classify Unmanned Aircraft Systems (UAS) as ei- ther Remotely-Piloted Aircraft Systems (RPAS) or Autonomous Aircraft Systems (AAS). This distinc- tion is based on the premise that the e ective safety risk management of UAS is dependent on the degree of autonomy of the system being operated. However, it is found that there is no consensus on the concept of autonomy, on how it can be measured, or on the na- ture of the relationship between Levels of Autonomy (LoA) and the safety-performance of UAS operations. An objective of this paper is to evaluate existing LoA assessment frameworks for application in avia- tion safety regulations for UAS. The results from a comprehensive review of existing concepts of auton- omy and frameworks for assessing LoA are presented. Six case study UAS were classi ed using the pub- lished LoA frameworks. The implied LoA of UAS for existing modes of operation (e.g., teleoperation, semi- autonomous) were also assessed using the published frameworks. It was found that the existing LoA assessment frameworks, when applied to the case study UAS, do not provide a consistent basis for distinguishing between the regulatory classes of RPAS and AAS. It was also found that the existing regulatory de ni- tion of an autonomous aircraft is too broad, covering UAS of signi cantly di erent levels of capability and system complexity. Within the context of aviation safety regulations, a new LoA assessment framework for UAS is required.