Lift off, please!
July 2023

Lift off, please!

By Volker Paulun (with material from DLR)
Drones and highly automated air taxis have the potential to enrich urban air transport with new possibilities. But what requirements must be met so that airborne urban mobility can be used in a few years? In the HorizonUAM (Urban Air Mobility) research project, the German Aerospace Center DLR has sought answers.

Flying quickly over the traffic jam to reach an important appointment – who among us has not dreamed of this. With an air cab, such mobility dreams can come true. But this requires some important building blocks such as availability, safety, efficiency, sustainability and affordability.

In order to get the full picture, the researchers developed an overall system simulation as well as a methodology for forecasting the global demand for UAM transport services. They applied this methodology to 990 urban areas with more than 500,000 inhabitants worldwide. “The results show that demand clearly increases with an increasing number of stops and their easy accessibility,” reports Bianca Schuchardt from the DLR Institute of Flight Guidance and HorizonUAM Project Manager. “Affordable prices play a crucial role in this.”

Over 200 cities worldwide are UAM-ready

Using the methodology, the scientists identified more than 200 cities worldwide as ‘UAM-suitable’. In addition to large cities such as New York and Tokyo, Hamburg is also among them. Important factors are, for instance, the size of the population, the extent of the city and the gross domestic product.

UAM Air Taxi
DLR study says air taxis could usefully add to the mobility mix in many metropolitan areas around the world© iStock

The researchers also took a close look at the costs. For this purpose, they developed and examined various application scenarios: urban air taxi traffic, airport shuttles and regional traffic. The result – in order to cover the operating costs and at the same time make a profit, operators of air taxis and shuttle services would have to charge prices ranging from four to eight euros per kilometer, depending on the circumstances.

Pilot? Not necessarily!

What should a vehicle that enables people to be transported from A to B in urban airspace ideally look like? The researchers in the HorizonUAM project also looked into this question. “We made several preliminary designs for vertical take-off air taxis. For one of the concepts with six swivelling rotors, we also produced a detailed cabin design, which we optimised for UAM operation in terms of safety, passenger comfort and operational procedures,” explains Schuchardt. In a newly built cabin simulator at the DLR site in Brunswick, 30 test participants experienced a flight in an air taxi using mixed reality. The test participants were very open to a remote-controlled air taxi flight without a pilot on board. However, in the case of unexpected events, such as a change of route, the perceived sense of well-being tended to increase when a crew member was on board.

Safe, reliable and largely autonomous – this is what the air taxi of the future should look like. The researchers also investigated how it could be operated and monitored safely from a distance and how certification for these aircraft would have to proceed. It quickly became apparent that two major challenges of manned and unmanned aviation come together for air taxis – the desire to achieve autonomy similar to that of unmanned aviation and the desire for the same high safety standards as in manned aviation. “We were able to successfully demonstrate the certifiability of air taxi components such as the battery system. For the much more complex certification of autonomy functions, we have developed partial solutions, but there is still a need for research in this area,” explains Schuchardt.

Stops for air taxis

If air taxis are to be used in urban areas at all, they need stopping points – that is, small urban airfields, known as vertidromes. These must be able to be integrated into the existing urban infrastructure and the relevant cityscape. In this context, the researchers built a model city on a scale of 1:4 at the DLR site in Cochstedt, in which they also investigated the management of a vertidrome.

City Airport für UAM
Visualization of a vertidrome placed in Hamburg’s Binnenalster lake© DLR

Schuchardt reports: “In the model city, we were able to test an air taxi scenario for Hamburg as a prime example. This involved an air link between Hamburg Airport and a vertidrome positioned in the Binnenalster lake. The simulated flight route through Hamburg could be conveniently arranged along the existing S-Bahn rail line. However, sensitive areas or those with higher air traffic volumes, such as around Hamburg’s University hospital, were omitted.

Perception and public acceptance

Urban air transport cannot be implemented without broad public acceptance. For this reason, the researchers conducted several studies to gather feedback from citizens. These results were then analysed by the researchers and a wide range of opinions emerged. For civilian drones (e.g. for medical transports), there was a general tendency towards a rather positive opinion, while for air taxis, the respondents were more sceptical.

The views of local residents were assessed in another study. This involved the use of virtual reality technology to give participants an impression of what it feels like to be a pedestrian in a city where civilian drones are flying. In addition, the researchers developed an app that not only measures the background noise of drones, but also allows the user to make their own evaluations

Electric propulsion systems for sustainable aviation

Based on the expertise and know-how of the Automotive Technologies division, Schaeffler develops electric powertrains for aircraft such as aerocabs (eVTOLs) and electric fixed-wing aircraft. “We offer a comprehensive range of systems and products for (hybrid) electric propulsion systems including powerful electric motors and fully integrated assemblies,” says Armin Necker, Managing Director of Schaeffler’s Aerospace division. At the 2023 Paris Air Show, the technology corporation showcased an exhibit demonstrating the company’s high level of expertise in the field of electric powertrain systems: a fully redundant, i.e., failsafe, dual electric propeller propulsion system consisting of two electric motors, each featuring 150 kW, silicon-carbide power electronics, a gearbox and propeller bearing including controllers. “This propulsion system was dimensioned, developed, designed and optimized according to a customer’s requirements,” Necker explains.