Conventional helicopters: an adaptiveness study for more electric and alternative propulsion technologies

The power plant and drive systems in a conventional helicopter cause high development and operating costs, compromise safety, and introduce performance limitations. Even though much effort is devoted to mechanical transmission systems, the use of electric components promises a higher reliability. Magnetic gearboxes address many of the problems in mechanical transmissions, but proved to be too heavy at this time. However, since this technology has not achieved its full potential, improvements are imminent and could allow its implementation in the near future. Several combinations with energy sources, amongst which liquid hydrogen (LH2), showed a turboshaft with kerosene to offer the lightest configuration. For the lower required power range, Avgas piston engines should at least be replaced with more efficient diesel engines. The possibility of using electric motors, such as the switched reluctance motor, to drive the tail rotor is possible at the expense of weight. The use of LH2, which has a threefold higher energy density than kerosene, in a helicopter seems feasible; though heavier due to an increased helicopter volume and tank weight, it offers a free cold source for high-performing high-temperature superconductive devices.