The MEA (More Electric Aircraft)/AEA (All Electric Aircraft) and MEE (More Electric Engine) is representative of system evolution, contributing to improved energy management of the entire aircraft system and reducing fuel consumption of aircraft. Looking at future aviation, it is necessary to have further evolution beyond the MEA/AEA and MEE to achieve further improvement of aircraft efficiency and “greener aviation”. The electrified propulsion system, which uses electrical energy as propulsive power, would be a possible option, and various kinds of configurations have been studied and developed. Small one- or two-seater airplanes have already successfully flown with the all-electrified propulsion; however, there are a lot of perspectives for the system configuration for larger-sized commercial aircraft. It is considered that a hybrid propulsion system, in which the E3M (Engine Embedded Electric Machine) provides assisting power to the engine shafts, would be one of the probable configurations. The authors are currently developing the E3M as an LP (Low Pressure) spool-driven generator, and the approach is considered to be practical because E3M technology can be commonly applicable for both large electrical power generation and hybrid propulsion. In this paper, several advanced propulsion system configurations are compared, and perspectives of the hybrid propulsion for future commercial aircraft are described. Also technical challenges for the MEE/E3M, continuing toward future hybrid propulsion, are outlined and further R&D steps are considered.

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