Risk-based regulation of unmanned aircraft systems
Creators: name: Washington, Achim
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 400199
subject: Aerospace engineering not elsewhere classified
classificationCode: 401005
subject: Risk engineering

description: The aviation sector is faced with a novel array of new airspace users including Urban Air Mobility (UAM) concepts, personal air mobility vehicles, reusable space launch vehicles, and Unmanned Aircraft Systems (UAS). Focusing on UAS, there is much effort being directed towards the development of safety regulations for this industry. National Aviation Authorities (NAA) have advocated the adoption of a risk-based approach to the development of regulations, whereby regulations are driven by the outcomes of a systematic process to assess and manage identified safety risks.<br><br>Central to a risk-based approach is the Safety Risk Management Process (SRMP). A review of relevant aviation safety policy, guidance and regulatory material found that aviation safety literature does not adequately address the uncertainty inherent to any SRMP. For example, when measuring risk, only the likelihood and severity are taken into consideration, with uncertainty generally not being mentioned. Where uncertainty is recognised, it is taken into consideration through the use of conservative worst-case assumptions. This can result in the imposition of overly stringent restrictions or worse, regulations that do not adequately mitigate safety risks. Subsequently, providing a more comprehensive treatment of uncertainty in the aviation SRMP is essential to the uptake of a risk-based approach to rule-making. Further, it follows that if assessments of performance can be uncertain, then these uncertainties also need to be accounted for in other NAA regulatory processes such as the regulatory compliance assessment and compliance finding processes. It was found that the current aviation compliance process does not provide an objective means for accounting for uncertainty. As a consequence, compliance assessments can be subjective and inconsistent, with regulators lacking the tools and processes to be able to make objective compliance findings on the basis of compliance risk. A means to enable NAA to account for uncertainty in regulatory compliance processes is needed.<br><br>The overall aim of this thesis is to improve regulatory outcomes under the new paradigm of risk-based regulation, through providing a conceptual framework for the rational, transparent and systematic treatment of uncertainty in the risk assessment and regulatory decision-making processes. The thesis proposes the application of Bayesian methods and normative decision theory to the aviation safety regulatory process. System Safety Regulations (SSR), commonly referred to as "Part 1309" regulations, for UAS are used as a case study. It is posited that the general theoretical approach proposed in this thesis can improve the objectivity, consistency, and transparency of current aviation regulatory processes. The generalised approaches presented in this thesis enable the adoption of risk-based rulemaking for new aviation sectors and provides the theoretical basis for risk-based compliance; a paradigm shift in how aviation safety regulators approach risk-based regulation.