By Bjorn Fehrm
September 21, 2021, ©. Leeham News: Airbus helicopter division presented their entry for the UAM market today at the Airbus 2021 Summit in Toulouse.
It was a presentation of a vehicle and ecosystem that has been cooking for years. After two demonstrators that tested different aspects of eVTOL flight and thousand of hours on supercomputers and in wind tunnels, the final CityAirbus is here, Figure 1.
Its configuration is as unique as Airbus’ approach when presenting it.
The presentation of the CityAirbus was different from the multitude of UAM launches we’ve seen over the last years:
The CityAirbus has a technical solution different from all other UAMs I’ve seen. Behind it lies over 200 flights with Airbus Vahanna and CityAirbus, where each demonstrator tested different parts of the UAM problem.
Vahanna explored vertical flight together with wing-borne flight, whereas CityAirbus focused on the operation of eight redundant lift propulsors in ground effect. It also explored the sizing problem known from helicopters. You can’t predict your problems using scale models as your challenges multiply with size. Therefore CityAirbus was large where Vahanna was not.
Airbus used these experiences together with thousands of hours with supercomputers and wind tunnels to study how propellers for VTOL generate noise but also how the stability of the propeller changes when you go from vertical propulsion to horizontal mode.
The result was a vehicle that has no movable parts except the rotors. Control of flight is 100% through an individual change of rotor RPMs. The CityAirbus has eight rotors with six working vertically from a main wing that also gives aerodynamic lift when flying forward.
Where it differs are the rear rotors which are canted to get a combined vertical and horizontal forward thrust. It means hovering is done with a slight tilt back to compensate for the rear rotor’s forward thrust component.
Forward flying tilts the CityAirbus forward until the speed of 120km/h is reached. The unique design is done to avoid the rotor propellers experience varying loads as this can cause propeller instabilities.
The CityAirbus is designed to be Certified to EASA Special Condition VTOL Enhanced Category. It gets its energy from batteries, and Airbus is realistic about this technology. It results in modest performance data, which is still described as a challenge for post-2025 introduction by Airbus.
Here is someone that dares say it upfront, with this technology, you cannot fly far and fast. You can fly 43nm at 65kts.
Airbus is not seeking investors to finance the project and, therefore, can avoid the overinflated claims that riddles this industry.
Can Airbus make it with the claimed performance and timetable? It’s the most realistic approach I’ve seen so far from this industry.