Reliability, availability and maintenance man-hours analysis of uncrewed aerial vehicle systems

The reliability of uncrewed aerial vehicle (UAV) systems is essential for mission success in safety-critical scenarios such as military surveillance, rescue operations, and disaster assessment. System availability depends not only on subsystem reliability but also on maintenance work to keep UAV systems functioning. This study evaluates UAV reliability characteristics, focusing on availability, reliability, and maintenance man-hours (MMH) under scenarios. Unlike existing UAV reliability studies that primarily focus on overall system reliability and availability, the proposed framework provides comprehensive subsystem-level analysis by identifying critical subsystems, evaluating their impact on system performance, and integrating MMH with preventive replacement planning. A generalized stochastic Petri nets (GSPN) modeling framework is applied to examine failure and repair behavior and assess system availability and reliability. The GSPN determines maintenance personnel and identifies maintenance priorities for subsystems. The MMH is determined using an age replacement strategy to identify optimal replacement timing based on component degradation. The results show that the proposed GSPN-based framework improves system availability from 0.9388 to 0.9905 and enhances system reliability from 0.6157 to 0.9605. In addition, MMH is evaluated under preventive replacement policies corresponding to 60%–90% of characteristic life, enabling replacement intervals for efficient maintenance planning. The framework supports UAV fleet operators, maintenance planners, and defense organizations through comprehensive reliability and availability analysis of the overall UAV system and its critical subsystems. By estimating maintenance manpower, identifying critical subsystems, and determining preventive replacement schedules, the framework supports efficient maintenance planning, improves operational readiness, and minimizes unnecessary maintenance effort and costs.