Conceptual design of electric helicopters for urban air mobility

There is currently interest in the design of small electric vertical take-off and landing aircraft to alleviate ground traffic and congestion in major urban areas. To support progress in this area, a conceptual design method for single-main-rotor and lift-augmented compound electric helicopters has been developed. To validate the method, flight test results from two existing experimental electric helicopters were used to create notional mission profiles that were applied in the design of new aircraft. The weight, power, and energy results of the designed aircraft were found to be reasonably similar to the test aircraft in both cases. The design method was then used to investigate the feasible design space for electric helicopters based on varying mission profiles and technology assumptions. The results for each configuration show that the design space is sensitive to battery energy density and that mission length variables such as hover time and cruise distance are more impactful than other mission profile parameters on the resulting vehicle design. Within the feasible design space, it was found that a crossover boundary exists as a function of cruise distance and hover time where the most efficient configuration changes from a single-main-rotor helicopter to a lift-augmented compound helicopter. In general, for longer cruise distances and shorter hover times, the lift-augmented compound helicopter is the more efficient configuration. For longer hover times and shorter cruise distances, the single-main-rotor helicopter is the more efficient configuration. The results provide selection criteria based on desired mission profile for comparing electric single-main-rotor helicopters and electric lift-augmented compound helicopters for urban air mobility purposes.