Air taxis land safely and autonomously Camera-based automatic landing system developed for Advanced Air Mobility

For autonomous aircraft to be able to fly in the city, they must be able to navigate reliably and automatically along the optimal route to the landing site. This is the only way to ensure both the safety of the critical landing phase and economic efficiency. In the recently completed “C2Land” research project, scientists from Technische Universität Braunschweig and the Technical University of Munich, in cooperation with Volocopter and f.u.n.k.e. Avionics, have developed and successfully demonstrated camera-assisted navigation and flight control. With this technology, crewed vertical take-off and landing aircraft (VTOL) will be able to land automatically, energy-efficiently and precisely.

“C2Land is now in control” is the message on a sunny winter’s day at an airfield in southern Germany. Concentrated faces follow every movement and every measurement at the ground station. The aircraft first hovers in the air, then turns and flies precisely towards the landing site – autonomously, without the intervention of a pilot.

Four cameras are installed underneath the aircraft. They are the eyes of the aircraft, constantly monitoring the surroundings and the landing area. “The most important human sense for driving and flying is sight. An autopilot should also be able to access these very information-rich sensory impressions – but it must also be able to process them,” says C2Land’s technical project manager, Finn Hübner.

“Our team at the Institute of Flight Guidance at TU Braunschweig has developed an image processing system that can recognise the various elements of a landing site and use them to deduce its own flight status or position. This position calculation works completely independently of other technical aids”.

Satellite-based navigation systems are generally accurate enough to perform precise landings. However, it is not easy to verify that the solution is correct – a problem not least because of the increasing frequency of jamming and manipulation of the satellite signal by military actors, among others. This is where optical positioning comes in, allowing the integrity of the entire positioning solution to be checked autonomously and continuously. This is the only way to increase confidence in the overall solution to the point where it can be used as an autopilot until touchdown.

On this basis, the Institute of Flight System Dynamics at the Technical University of Munich developed a flight control system that automatically steers the new type of aircraft along an optimised flight path until it touches down. The special dynamic characteristics of a VTOL with many small rotors instead of a large slowly reacting propulsion system had to be taken into account. To find the optimal flight path, a special optimisation algorithm was developed to find the most energy-efficient route while minimising the risk of unsafe flight conditions.

During an autonomous landing, the safety of other airspace users must also be guaranteed. To this end, f.u.n.k.e Avionics GmbH has developed a transponder-based anti-collision system which, in case of doubt, resolves the situation by issuing avoidance commands. Avionics components for the exchange, recording and telemetric transmission of system data have also been provided so that the unmanned C2Land system can be monitored in flight and commands can be transmitted.

Together with project partner Volocopter, the sensor technology was then installed in eVTOL (electric Vertical Take-Off and Landing aircraft) prototypes and validated in realistic flight tests. These electrically powered test vehicles are intended to provide a safe, quiet, and emission-free mode of mobility to complement existing transport systems bypassing congested streets, thereby reducing the burden on urban road traffic.

The C2Land C2 project, funded by the German Federal Ministry for Economic Affairs and Climate Action (FKZ: 50NA2003) and managed by the DLR Space Agency, has now been successfully completed. “We were able to demonstrate the technical feasibility of an optical automatic landing system for this new class of aircraft,” says Hübner. It will probably be some time before the system can be used commercially in a fully autonomous air taxi. It would need to be extended to include more flight phases, the test setup would need to be miniaturised, and risk analyses and extensive testing would need to be carried out in preparation for approval by the relevant aviation authorities. The concept could also be integrated into VTOLs and helicopters to assist pilots and make landings even safer.