Application of risk tree to assess the reliability of tethered high-altitude unmanned platform

This paper addresses the problem of reliability assessment for a tethered high-altitude unmanned telecommunication platform using the risk tree analysis method. The aim of the study is to develop and test a methodology for the quantitative estimation of the probability of risk events and the associated material damage during long-term platform operation. A disruption in the provision of broadband wireless communication services by the platform is considered as the resulting risk event. A detailed technical description of the tethered platform “Albatros" is provided, which serves as the basis for identifying risk events. The general theory and methodology for constructing and analyzing a risk tree are presented, including the parameterization of the model with probabilistic and cost characteristics. Using the tethered high-altitude unmanned telecommunication platform as a case study, a comprehensive numerical investigation is carried out. Within this investigation, a sensitivity analysis of key output indicators — namely, the reliability function, quantiles, mean time to failure, and expected damage — is conducted with respect to the statistical properties of failure times, specifically the coefficient of variation and the distribution shape.The practical conclusions derived from the study demonstrate that the use of adequate probabilistic models (as opposed to simplified exponential ones) is critical for obtaining realistic forecasts. The most dangerous risk evolution scenarios are identified, and the contribution of factors influencing the occurrence of these events is quantitatively assessed. The proposed methodology is universal and can be applied to a wide range of complex technical systems, including other tethered platforms whose architectures allow decomposition into key components with established logical relationships between their failures. The obtained results can be used for the evidence-based design of such systems, the planning of scheduled maintenance, and the optimization of technical support strategies.

tethered high-altitude unmanned platform, reliability, risk, probabilistic risk analysis, risk tree, failure probability, most dangerous path, sensitivity

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