Systems for a Digital Take-off

Accounting for around 3.5 to five percent of anthropogenic warming, aviation is one of the biggest climate polluters. Under these circumstances, it is difficult to imagine that flying in its current form will still be part of our everyday lives in the future. To make flying more sustainable, alternative concepts rather than gradual improvements are called for. In addition to the use of sustainable fuels, hybrid-electric propulsion systems are increasingly becoming the focus of research and development. These technologies combine renewable energy sources with conventional propulsion systems and could thus make a decisive contribution to reducing environmental pollution.

However, integrating hybrid-electric propulsion systems in drones and aircraft is complex. Developing new product architectures involves many different manufacturers who realize the products. Long development times further complicate the situation, especially for aircraft manufacturers: Development, component and simulator tests, flight tests, certification, and other steps can take between five and 15 years. During this period, manufacturers, developers, suppliers, and authorities must remain in constant contact with each other. To make this complexity manageable, researchers at Fraunhofer IPK apply the concept of system orientation. The aircraft and its components, such as the propulsion system, are no longer viewed as stand-alone elements, but as parts of a larger system that influence each other. It is crucial to define the interfaces between the different systems and to develop a system architecture that enables seamless integration. However, this architecture is only the first step – to be truly effective, it must be integrated into the entire development, manufacturing, and testing process for these systems.

Another key to successfully implementing new propulsion concepts is using digital twins. These virtual models replicate the physical system and make it possible to link subsystems, identify target parameters, and analyze the behavior of the entire system. This can offer crucial advantages when developing and testing new hybrid electric engines, as the interaction between conventional combustion in a gas turbine, electric drive, and battery is highly complex. During flight, the parameters of all these systems must be continuously adjusted. The digital twin concepts developed in the DIREKT project help engineers design systems capable of handling this task: Both the electrical and conventional consumption of the powertrain and the current charge level of the electrical energy storage are continuously recorded – in combination with the remaining flight distance, this information can then be used to optimize the settings of the various drive parameters. And when developing the next generation of a propulsion system, the insights gained from the digital twin can be directly incorporated into the system architecture and support development decisions. This shortens development times and enables a continuous improvement process.

To make flying more sustainable, alternative concepts are called for:
Hybrid-electric propulsion systems are increasingly becoming the focus of research and development.

Before a new engine can be used in flight, manufacturers must undergo a certification process that imposes rigorous requirements on documentation and the scope and quality of the underlying data. This is particularly complex when certifying completely new propulsion systems, since sufficient reliable empirical data is not yet available to define safety limits in hybrid-electric propulsion systems. Using digital twins can make a decisive difference here, because new engines also require suitable methods to investigate the effects of such fundamental changes. By integrating data from different suppliers and manufacturers, the players can work closely with certification authorities and exchange the data they have collected. This facilitates faster and safer development of the necessary safety standards. Investigating this potential is also a part of the DIREKT project. The challenges here do not only lie in complex data integration, but also in defining consistent business models that motivate the various partners to provide the necessary data.

The interplay between data-driven system orientation and the use of digital twins could lay the foundation for the next generation of flying: more efficient, more sustainable, and ready for the challenges of the future.