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Electric VTOL Aircraft for Urban Air Mobility

Electric propulsion concepts are a key technology for the development of VTOL air taxis for urban air mobility. Electric power transmission enables the distribution of thrust generation to multiple, flexibly arranged rotors or fans, opening up a large design space. The balance between efficient hovering/vertical flight and high efficiency during cruise flight is an essential design decision. Considering a possible future on-demand UAM network, it is also important to be able to serve a broad spectrum of ranges in the best possible way.

In a study at Bauhaus Luftfahrt, two air taxi concepts with different design priorities were investigated as possible reference configurations: a multicopter with 18 concentrically arranged rotors and a correspondingly large rotor surface as well as a so-called lift+cruise configuration. The latter enables vertical take-off and landing using eight smaller rotors and changes to a separate drive train with a single propeller for cruise flight. Lift is then efficiently generated by fixed wings. This allows a much higher cruising speed of 180 km/h compared to the multicopter. A glance at the energy efficiency for different mission ranges illustrates the different strengths of the concepts. The multicopter requires significantly less energy for missions within its mission range (up to 19 km). Only on longer mission ranges, the lift+cruise concept achieves better efficiency values. From an energy efficiency perspective, this indicates a fleet mix for future UAM scenarios.

  • Comparison of technical data of air taxi concepts: The multicopter relies on a very efficient hovering flight with an exceptionally low disc loading. The more compact and therefore less efficient VTOL system of the lift+cruise configuration, in turn, permits much better aerodynamics in cruise flight.Comparison of technical data of air taxi concepts: The multicopter relies on a very efficient hovering flight with an exceptionally low disc loading. The more compact and therefore less efficient VTOL system of the lift+cruise configuration, in turn, permits much better aerodynamics in cruise flight.
  • Comparison of technical data of air taxi concepts: The multicopter relies on a very efficient hovering flight with an exceptionally low disc loading. The more compact and therefore less efficient VTOL system of the lift+cruise configuration, in turn, permits much better aerodynamics in cruise flight.Comparison of technical data of air taxi concepts: The multicopter relies on a very efficient hovering flight with an exceptionally low disc loading. The more compact and therefore less efficient VTOL system of the lift+cruise configuration, in turn, permits much better aerodynamics in cruise flight.
  • Energy efficiency of air taxi concepts for two and four passengers: The multicopter concept is significantly more energy-efficient in its range of applications. On longer distances, however, the lift+cruise configuration provides better efficiency and requires less than 400 Wh per passenger kilometre for distances greater than 46 km.Energy efficiency of air taxi concepts for two and four passengers: The multicopter concept is significantly more energy-efficient in its range of applications. On longer distances, however, the lift+cruise configuration provides better efficiency and requires less than 400 Wh per passenger kilometre for distances greater than 46 km.