Formulating Risk Indices and Criteria for Unmanned Aerial Systems

Abstract

Purpose: Owing to widespread use of unmanned aerial systems (UAS) across various sectors, the likelihood of accidents is progressively increasing. To ensure operational safety and reliability, establishing risk indices and criteria is imperative. However, current insufficient accident data hinder the formulation of reliable risk criteria. Thus, this study offers a proposition for UAS risk indices, prioritizing ground personnel damage as a significant consequence of UAS crashes.BRMethods: The comprehension of major risk events influencing factors, treated probabilistically, enables the derivation of risk indices and criteria for UAS. These get established through comparison with the risk indices and criteria for conventional manned aerial systems‘ structures and engines, including factors like Single Flight Probability of Failure (SFPOF), Cumulative Probability of Failure (CPOF), Non-Recoverable In-Flight Engine Shutdown (NRIFSD) and Engine Related Loss of Aircraft (ERLOA).BRResults: The risk criteria for UAS can be updated by referencing risk indices (NRIFSD, ERLOA) based on instantaneous or cumulative failure rates of manned aerial systems. Both rates take into account the risk severities and the occurrence probabilities for each risk factor. Notably, the specific acceptable risk criteria for UAS can be appropriately adjusted by considering the likelihood of a fatal injury to ground personnel (0.01∼1) and the probability of a person‘s proximity to the UAS crash site (0.026∼0.000019 people/m2) according to the operational environment.BRConclusion: NRIFSD, representing risk per 100,000 hours, suits short-term operations’ risk evaluation. Concurrently, ERLOA provides comprehensive information about the reliability of the aircraft, enabling its utilization in managing operational maintenance costs and making economic lifespan decisions. Depending on the operational environment and UAS objectives of, users can select appropriate risk indices and criteria.