Gerrit Rexhausen, project leader for Lufthansa Technik’s Hydrogen Aviation Lab in Hamburg, discusses progress and pitfalls so far in the MRO provider’s project to evaluate maintenance and ground processes for hydrogen-powered aircraft.

Lufthansa Technik (LHT) received the Airbus A320 for its Hydrogen Aviation Lab (HAL) last October. Since you took possession of the aircraft, what progress has been made on the study?

Since [the public unveiling in October 2022], the project activity has been mainly focused on the overall setup of the research program together with the project partners, the design and layout of the various aircraft modifications, and the procurement of suitable hydrogen components. Here, finding qualified suppliers proved quite a challenging task as we are breaking new ground in almost every aspect. Hence, we could rarely rely on off-the-shelf hardware and almost every component had to be purpose-designed or at least heavily modified for the use in our aircraft laboratory. The still tense supply chain situation also didn’t make this task easier.

The fuel cell, for example, is now procured and currently in final stages of modification before installation into the aircraft’s former auxiliary power unit compartment. We have moreover successfully installed the mandatory gas warning system. The cryogenic (-253C) hydrogen tanks, the internal one to be installed in the rear aircraft fuselage and the external one in the container-based “refueling station,” are expected to arrive in November/December. With the major components finally on-site, we will begin the integration phase shortly after and hope to commission the hydrogen system early next year, finally paving the way for the first fueling and the commencement of practical research.

What lessons have you learned so far about hydrogen-based aircraft operations?

Even though the practical research could not yet commence due to the ongoing procurement and installation of hydrogen components, we have already made several valuable findings in the setup and design phase:

• We were able to significantly broaden our insights on the landscape of suitable suppliers, especially regarding the fueling system’s components.
• We already gained a lot of good experience in designing a capable fuel flow interface for the aircraft part of the HAL, for which we broke entirely new ground as there is no off-the-shelf solution available yet.
• We managed to develop a comprehensive control concept for the overall field laboratory that allows for a safe and efficient operation on LHT’s Hamburg base and the adjacent premises of Hamburg Airport.
• We gained a lot of valuable experience with what is required to obtain the operating permit from the regulatory bodies.

How is predictive maintenance being used within the digital twin of the A320?

The digital twin of the HAL, which was mainly designed by the German Aerospace Center, allows us to significantly broaden the parameters of the various research tasks. Once it is validated against the practical research in the field laboratory, it allows the researchers to try out a multitude of parameters in a short amount of time where the real asset would need lengthy modifications for only one adjusted parameter. This increases productivity and, in certain use cases, the virtual/digital level significantly broadens the knowledge that can be gained. Predictive maintenance, i.e., the timely prediction of hydrogen component failures and their prophylactic replacement, can be one aspect in this regard. Elements of artificial intelligence are used, for example, in smart hydrogen sensors that have some sort of self-learning capabilities regarding their calibration and adjustment of the necessary check intervals.

There has been growing aviation industry interest in hydrogen technology. What industry feedback are you getting from Lufthansa Technik’s customers? Does it seem like the technology is gaining traction?

Given the comparably long research horizon, that might a bit early to tell but, generally, we have received positive feedback that we are evaluating the technology at such an early stage, and especially that we also are looking at it from the MRO and ground handling perspective. Our customers are equally eager to learn more about this potential future gamechanger.

As the use of hydrogen will affect not only the aircraft design but also the required ground infrastructure, customers at a certain point in time might have to look at the possible purchase of hydrogen-powered aircraft from more directions than just the aircraft data to make an informed decision. In this regard, we hope the HAL can deliver some valuable insights not only for aircraft designers and operators, but for all stakeholders that will have to deal with the technology in the future, for a simple reason: To fully leverage hydrogen’s beneficial impact on the aviation industry’s sustainability efforts, hydrogen-powered aircraft need to achieve a sufficient market penetration. Therefore, we must make sure that as many stakeholders as possible can safely and efficiently operate the technology.

What are your predictions for the growth of hydrogen technology over the next decade? Do you expect more MRO companies to get involved?

The European Union targets net zero CO2 emissions by 2050. With an envisioned market readiness from 2035 onwards, hydrogen could play an important role in this, both via direct combustion in a turbine and via conversion to electricity in a fuel cell to supply (fully or hybrid) electric propulsion. Due to its higher energy density than Jet-A and a lower Global Warming Potential of up to 55% (Jet A: 310%, SAF: 185%), hydrogen appears one promising option for achieving the industry's long-term climate goals.

And not just in our (aviation) industry. We already see significant investments being made in the technology and infrastructure (e.g. European Hydrogen Backbone) for hydrogen in various other industries and countries. I can well imagine the aviation industry following suit once the general technical foundation is laid. Laying this foundation for aviation is one of the goals of the HAL. Once a critical market penetration is reached, every MRO will have to deal with the technology to stay competitive. At LHT, the HAL thus also helps us to stay ahead of the competition.

To find out more about the potential future of hydrogen and its impact on the aftermarket, make sure not to miss the “Sustainability Part 1: The potential of hydrogen and electric” session on Oct. 17 at MRO Europe in Amsterdam.