The article addresses the urgent problem of ensuring fire safety at hazardous industrial facilities of the oil and gas refining industry. In the context of the implementation of the Strategy for the Development of Unmanned Aviation of the Russian Federation until 2030, the prospects of using heavy unmanned aerial vehicles for extinguishing fires on hard-to-reach high-altitude technological installations are substantiated. The authors analyzed accident statistics and proposed a new engineering methodology for calculating the parameters of fire extinguishing systems using heavy unmanned aerial vehicles. A key feature of the developed approach is the system integration of three groups of parameters: the geometric characteristics of the protected object, hydraulic pressure losses in vertical hose lines, and the mass-dimensional limitations of the aircraft. The paper describes in detail a step-by-step algorithm that includes verifying the conditions of payload margin and permissible working pressure in the system. The proposed methodology allows for automating the equipment selection process, filtering out technically unfeasible configuration options, and minimizing the number of unmanned aerial vehicles required to ensure the normative intensity of the extinguishing agent supply. The obtained results form a theoretical and practical basis for the design and implementation of new-generation mobile robotic fire extinguishing complexes.