The search for new types of propulsion systems in aviation has been ongoing throughout its history. Often there were parallel tests of engines based on different physical principles. This made it possible to determine the more promising direction of work.
Today, there are active experiments with the installation of electric motors on airplanes. This trend is due to their relative simplicity and environmental friendliness: electric motors have no harmful emissions, like traditional turbojet engines. However, creating an airplane that uses only electric motors as its propulsion system is too complicated a task, requiring new technologies in energy storage: you need batteries that would be light enough, quickly charged, have the necessary capacity, and not react to different climatic conditions.
If you count only in pieces, purely electric flying machines are probably the most mass-produced in the world right now. But they are only small copters, serving mostly as a means of entertainment. The growth in the size of these aircraft is limited by the current capabilities of electric batteries. A hybrid propulsion system combining gas turbine or piston engines with electric ones seems more logical.
Today, the direction of low-noise and environmentally friendly hybrid propulsion systems has become one of the defining technologies for the future of aviation. All aviation concerns of the world and specialized scientific centers are engaged in their research, first of all for prospective serial airplanes of small and regional aviation. Such aviation, according to forecasts, should appear in the world somewhere around 2030. The advantage of hybrid power plants is the possibility, on the one hand, to benefit from energy-efficient, environmentally friendly electric technologies, on the other hand, to maintain acceptable weight efficiency by optimizing the design and modes of operation of gas turbine or piston aircraft engines.
Russia is a leader in this area. In 2021, the S. A. Chaplygin Siberian Aviation Research Institute (SibNIA) together with the CIAM created the Yak-40LL laboratory aircraft. This was the first flying laboratory in the world to test a hybrid power plant including a 500 kW electric aircraft engine. Instead of central engine on this Yak there is gas-turbine engine TV2-117. An electric generator is installed on its shaft. The generator is the source of power for the unique electric aircraft engine which has no analogues in the world. Its peculiarity lies in the use of second generation high-temperature superconductors as stator windings. The efficiency of the electric motor is 98%.
High-temperature superconductors allow reducing the weight of electric machines many times over. There is every reason to believe that only a similar technology will make it possible in the future to create electric motors and generators with a capacity of 10-20 MW for hybrid propulsion systems for short- and medium-range aircraft. Application of electric propulsion in aviation will allow to reduce noise and fuel consumption significantly. In the perspective of 15-20 years with the improvement of technologies it is predicted to reduce the cost of operating the aircraft up to 75%.
