At the moment, the design of various aircraft systems is a complex process in which you have to choose from a large number of competing versions of the developed system. Decisions that were made during development can affect various key factors, including system reliability. In this article a comparative analysis of two variants of hydraulic system power unit design for a heavy twin-engine aircraft with passenger capacity up to 300 people was carried out. For the analysis was taken a number of basic technical solutions, which were applied in such aircraft as A-350, B-787, IL-96, SSJ-100, and several others. As a result of the analysis, the most suitable version of the hydraulic system in terms of reliability and the possibility of implementing this version of the system was selected.