**4. Summary and conclusions**

Future development of power units requires an in-depth analysis of existing design, manufacturing, and logistics solutions. Their optimization can provide increasing in power unit efficiency. However, new ideas can provide more best performance, but they require a lot of time for research, testing, and analysis of results. New approaches (e.g. hydrogen power units) create significant impact on the traditional (for aviation engineering) design process.

Explained above detailed separation of the power unit structure by subsystems and subcomponents can provide more best understanding areas where it is necessary to apply extra efforts for the power unit efficiency increase, and can help to understand dependencies between different structural members of a power unit.
