Mission-Phase Dependent Reliability and Maintainability Analysis of a UAV Using Semi-Markov Process

Unmanned Aerial Vehicles (UAVs) are increasingly employed in a wide range of applications where mission success depends on the reliable operation of several interdependent subsystems throughout different phases of flight. This paper presents a reliability and maintainability assessment framework for Unmanned Aerial Vehicle (UAV) missions using a three-phase mission model and Semi-Markov Process (SMP) modeling. The mission is decomposed into three sequential operational phases, namely takeoff, mission execution and landing, and the stochastic behavior of the UAV system is analyzed through state-transition modeling. Reliability and maintainability measures are evaluated to assess mission performance and system recovery characteristics. In addition, reliability importance analysis is performed to identify and rank critical subsystems according to their contribution to overall mission success. The proposed framework facilitates the identification of vulnerable mission phases and key components requiring reliability enhancement and maintenance attention and thus, provides a systematic tool for reliability assessment, design optimization, and maintenance planning of UAV systems. Numerical results demonstrate the effectiveness of the approach in supporting reliability-centered design, maintenance planning, and performance improvement of UAV systems.