Introduction: Nowadays, in civil aviation, issues related to improving efficiency, reducing the costs of air operations as well as the negative impact of air transport on the environment are of increasing importance. These ideas allow the formulation of the paradigm relating to the development of air transport – ‘more Efficiently, more Economically, more Eco-friendly – 3E’. The article presents in a cross-sectional and synthetic way research conducted by leading scientific centres around the world as well as prototype aviation constructions designed by companies from the aviation industry. Benefits and disadvantages of future propulsions, such as purely electric, hybrid and distributed propulsions, were presented. Conclusions were formulated regarding further possible directions of civil aviation development, taking into account the improvement of its efficiency as well as economic and ecological indicators.

The paper describes the selection of a distributed propulsion for the AOS H2 motor glider (selection of engines, their number, and propellers) and determination of its performance. This analysis is related to the research conducted on environment friendly and hybrid propulsions in various research centres. The main aim of the analyses conducted is to increase the performance of vehicles powered by electric motors. The batteries have a low density of energy, i.e. the ratio of mass to cumulated energy. Instead of a battery set, it is possible to apply a hybrid-electric system, where the combustion engine works as a generator or an electric-hydrogen generator, where the hydrogen cell supports a small set of batteries. One of such flying vehicles, fitting in this trend, is the AOS H2 motor glider built at the Rzeszow University of Technology in cooperation with other universities. It is a hybrid aircraft, equipped with a hydrogen cell, which together with a set of batteries is a source of electricity for the Emrax 268 electric motor. To increase the vehicle's performance (the range and flight duration), it is possible to use a distributed propulsion. This type of propulsion consists in placing many electric motors along the wingspan of the aircraft. Appropriate design of such a system (propeller diameters, engine power, number of engines) can improve the aerodynamic and performance parameters of the airframe. An analysis of the performance for the selected flight trajectory for this propulsion variant was conducted and compared to the performance of the AOS H2 motor glider equipped with traditional propulsion. The consumption of hydrogen was also determined for both systems. The results obtained were presented in the diagrams and discussed in the conclusions.

Comparative analysis of harmful compounds emission of classical and distributed propulsions applied on the AOS motor glider, taking into account the perspective of the development of hybrid propulsions. A novel path is indicated by so-called distributed aircraft propulsion. The advantages and disadvantages of this type of solutions are presented, as well as the conceptual design of the distributed propulsion for the AOS 71 motor glider. In the paper there were compared the emissions of harmful compounds generated by a hybrid power unit developed for the airframe of AOS 71 motor glider – traditional propulsion, so-called focused (one-propeller) and dispersed propulsion (multi-propelled). Functional diagrams of both types of propulsions solutions are presented. Construction and aerodynamic constraints of both propulsions are discussed and comparative analysis is made. In the traditional version of the propulsion (so-called focused propulsion). the propeller is driven by an Emrax 228 electric engine with effective parameters: N = 55 kW, M = 120 Nm. The power source is a battery set with a capacity of 16 Ah and a range extender powered by a LCR 407ti rotating piston engine with maximum power of 28 kW. In the variant of the distributed propulsion. Ten electric engines of AXI 8120 type were used to drive small propellers arranged along the wingspan. The power source in this variant is analogous to the variant with the Emrax electric engine. For the adopted variant of the flight mission of the motor glider. a flight trajectory model was developed, which was used to determine the load of the power unit. In laboratory conditions. emission tests of both propulsions were conducted. The results are summarized in charts and discussed in the conclusions.