The German Aerospace Center (DLR) demonstrated an air transport scenario in Cochstedt between Hamburg Airport and a "stop" (Vertidrom) on the Inner Alster lake. The HorizonUAM (Urban Air Mobility) project aims to define aircraft, flight corridors, and landing stations.

During the flight tests, several 1:4 scale multicopters were piloted as flying objects, moving between the airport and the Vertiport Arena on the Inner Alster Lake, flying over a narrow street. The researchers demonstrated methods of airspace integration using so-called U-space services and showcased the workflow of a vertiport controller. The application and safety of artificial intelligence were also tested, using the example of automatic person detection via onboard camera images. Algorithms for safe communication and navigation in urban areas were validated.

Numerous stops and affordable prices are said to be essential for any potential demand for air taxi services; a price range of four to eight euros per kilometer is needed to ensure reasonably economical operation. This includes the concept of an air taxi with six swiveling rotors for four passengers and a range of up to 100 kilometers.

A.Kaysser-Pyzalla (right)

In early July 2023, researchers presented their findings at the DLR National Test Center for Unmanned Aircraft Systems in Cochstedt. Key flight tests were conducted in a model city. Concrete examples for the development of urban air traffic were designed, particularly for the city of Hamburg. Simultaneously, feedback was gathered from citizens regarding the potential use of urban air traffic. "Future urban air traffic places diverse demands on safe and efficient operation, requiring suitable take-off and landing sites as well as flight routes that can be integrated smoothly into the existing infrastructure and the daily lives of local residents," said DLR Chair of the Executive Board, Anke Kaysser-Pyzalla. "This requires a holistic approach to research and development, which the DLR project HorizonUAM addresses." A total of ten DLR institutes and facilities are involved.

Under observation

To gain a comprehensive understanding, the researchers developed a complete system simulation and a methodology for forecasting global demand for UAM (Universal Ambulance Service) transportation services. They applied this method to 990 urban areas with more than 500,000 inhabitants worldwide. "The results show that demand clearly increases with a rising number of stops and their ease of access," reports Bianca Schuchardt from the DLR Institute of Flight Guidance and project manager of HorizonUAM. "Affordable prices play a crucial role." Using this methodology, the researchers identified more than 200 cities worldwide as "suitable for UAM." These include metropolises like New York and Tokyo, as well as Hamburg. Important factors include population size, urban area, and gross domestic product.

Photos: DLR

The researchers also examined the costs. To do this, they developed and investigated various application scenarios: inner-city air taxi services, airport shuttles, and regional transport. The result: To cover operating costs and simultaneously generate 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 specific circumstances.

Vertical takeoff aircraft

Several preliminary designs for vertical take-off and landing (VTOL) air taxis were developed. "For one of the concepts with six swiveling rotors, a detailed cabin design was also created, which we optimized for UAM (Universal Air Taxi) operation with regard to safety, passenger comfort, and operational procedures," explains Schuchardt. In a newly constructed cabin simulator at the DLR (German Aerospace Center) site in Braunschweig, the flight in an air taxi was simulated for 30 test subjects using mixed reality. The test subjects proved to be very receptive to a remotely piloted air taxi flight without a pilot on board. However, in the event of unexpected occurrences, such as a route change, the perceived well-being tended to increase when a crew member was present.

The air taxi of the future should ideally be safe, reliable, and largely autonomous. Researchers also investigated how it could be safely operated and monitored remotely, and how the certification process for these aircraft should work. It quickly became apparent that air taxis bring together two major challenges of manned and unmanned aviation: the desire for comparable autonomy to that of unmanned aviation and the need 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 significantly more complex certification of autonomous functions, we have developed partial solutions, but further research is needed in this area," explains Schuchardt.

bus stops

For air taxis to be used in urban areas, they need landing points, i.e., small inner-city airfields, so-called vertidromes. These must be integrated into the existing urban infrastructure and the respective cityscape. In this context, researchers at the DLR site in Cochstedt built their model city on a 1:4 scale, in which they also studied the management of a vertidrome. Schuchardt: "The simulated flight path through Hamburg could be conveniently laid out along the existing S-Bahn (suburban railway) line." Sensitive areas or those with higher air traffic volume, such as around the Hamburg University Hospital, were avoided.

Perception and acceptance

Urban air transport could not be implemented without broad public acceptance. Therefore, the researchers conducted several studies to gather feedback from citizens. They commissioned the institute BIK Aschpuris + Behrens to carry out a large-scale telephone survey. The survey revealed a tendency towards a more positive opinion regarding civilian drones, while respondents were more reserved about air taxis.

The perspective of local residents was captured in a further study. Here, participants were given an impression, using virtual reality technology, 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 noise level of drones but also allows users to provide subjective assessments of it.

Example Hamburg

To visualize their work in HorizonUAM, the researchers created 3D renderings illustrating their vision for vertidrome concepts. The traffic-congested metropolis of Hamburg proved particularly suitable as a reference city for various HorizonUAM studies. "In Hamburg, we placed a vertidrome with a single landing pad, the so-called vertistop, in the Inner Alster Lake," reports Schuchardt. "We designed a vertidrome with multiple pads for takeoff and landing, i.e., a vertiport, for the Hanseatic city's airport," Schuchardt continues. A particular challenge is the integration at the airport, as the air taxis must not get too close to conventional air traffic. In rapid simulations, as many as 20 different vertidrome locations within Hamburg were investigated. In this way, 2,800 flights with a total of 275 air taxis could be completed in 24 hours.

In addition, the researchers defined approach and departure maneuvers and routes for air taxis within Hamburg. These were analyzed in rapid simulations and then tested in several scenarios together with air traffic controllers in a tower simulator. The study investigated how air traffic control at Hamburg Airport could manage manned and unmanned air traffic simultaneously. The defined procedures proved effective, but the increasing workload for controllers with additional airspace users also became apparent.

Following the completion of the HorizonUAM project, a follow-up project is already being planned. This project will continue work on the overall system simulation. The model city will also be further developed and expanded to include infrastructure for a permanent vertigo demonstrator, and the remote control of multiple air taxis will be tested in the control center.

www.dlr.de