Interview Gianmarco Sironi Interview Gianmarco Sironi | HBM

Advanced Air Mobility and Its Challenges

For decades, HBK has been delivering end-to-end measurement and data analytics solutions for aircraft testing, including structural, propulsion (gas turbine, electrics), thermal, acoustics and in-flight testing.

HBK application experts are highly skilled and experienced, working closely with our customers. So, they know about the aerospace industry, the engineering and validation processes, trends and challenges, such as Advanced Aircraft Mobility (AAM, also called UAM or eVTOL).

To help you get to know the HBK aircraft applications team – who they are and why they are the right support, not only for classical aircraft but also for start-up customers targeting AAM solutions – we interviewed our aircraft testing expert Gianmarco Sironi from our HBK Custom Solutions team.


Gianmarco, you have worked for HBK (formerly HBM) since 2016, managing global test and measurement projects for aerospace and defence customers. Before becoming a project leader in aircraft testing at HBK, you worked for a well-known helicopter manufacturer. How did your professional role change? Does your additional job experience benefit you in today’s job tasks?

"I moved from a team-leading role to a project-leading role and that has been one of the most satisfying challenges in my professional experience. The technical experience gained in my previous position has often proven precious in analysing customer needs and formulating the best possible response to project requirements."

Do companies designing AAM have a different development and validation philosophy compared to, for example, a traditional helicopter manufacturer?

"On the flight control side, there are some significant technical differences between the eVTOL concepts being developed for urban air mobility and a traditional rotary wing aircraft. Helicopter manoeuvring and control is based on swashplates which drive the blades’ variable pitch inside the rotor. This results in a complex cinematic, where all parts are subjected to heavy mechanical loads. Each rotating part must be individually tested and validated to secure fatigue life.

New concepts for urban air mobility rely on multiple electrical engines and manoeuvring is in most cases achieved by individually controlling each engine, removing one layer of complexity due to the rotor’s cinematic. This will drive new requirements in validating the design for sure. Some structural tests will probably be replaced by intensive testing and stressing of the electrical engines to ensure the necessary durability. Here, our eDrive dynamic power analysis solution is best-in-class. There will also be a need to validate fail-safe options, for example, with how many inoperative engines can I still achieve normal flight; how many operative engines do I need for a controlled emergency landing, and so on.

I also believe that the validation of the fuselage and most structural parts will continue to be based on the estimation and measurement of external loads and their effective reproduction on test rigs. This means that good old structural testing, as we already know it, will continue to be with us for quite a while."

What sort of R&D-based test facilities and measurement equipment do you see at AAM manufacturers?

"Compared to traditional aircraft and helicopter manufacturers, eVTOL manufacturers will need to set up facilities for electrical power testing and battery or fuel cell testing.

Then, of course, there will be the traditional test rigs for structural testing and validation, but this could also be done by external partners. Having a single partner company that can successfully fulfil the measurement and testing requirements of all these kinds of testing will surely be of advantageous."

What are the unique challenges of AAM?

"I already mentioned one, which is the unique manoeuvring and control concept based on a multi-engine architecture. This will pose some significant technical challenges, even for validation and testing.

There are, of course, other critical aspects. These aircraft are mostly aimed at urban mobility and are, therefore, supposed to fly in densely populated areas, a condition that requires the highest possible levels of safety and redundancy. Just to give you an idea – right now, single-engine helicopters are not allowed to fly over urban areas in Europe, so manufacturers will be requested to demonstrate the highest safety and redundancy standards. I’m expecting a strong focus on fail-safe operation.

Crashworthiness will also be very important, given the fact that there will be a number of batteries on board. Most of the lower part of the fuselage is normally crash-dimensioned, but the additional presence of batteries will add the requirement of safe battery containment in case of a crash. This will be somewhat comparable to the actual requirement of safe fuel containment but will pose new and interesting technical challenges."

"We are very passionate when it comes to aviation and we really enjoy working with these projects making the customer’s targets our own."

Gianmarco Sironi, Aircraft Testing Expert at HBK

At what stage do you see FAA or EASA type certification?

"There is still some work to do, but the regulators are certainly taking this new development very seriously. It is not easy to formulate airworthiness directives for something that represents a completely new way of flying, so I think this is going to take a while and it will be an iterative process. EASA is following the approach of building a new regulatory framework specific for this kind of aircraft, while the FAA is working on adapting its Part 23 (Small Airplane Certification) for the certification of eVTOLs. This is a potential disruptive point. If the regulators continue going on their own without harmonizing their approaches, we may see significantly different processes and requirements applied between eVTOL designs developed in the EU and in the US, which could mean that obtaining the double type certification may be more difficult compared to what happens with today’s traditional aircraft and rotorcraft.

It could even be that an eVTOL design, developed in Europe, will require substantial modifications and additional validations to fly in the US, and vice versa."

What are the three most important things to consider for/during type certification of aircraft?

"First, you need a good and open communication line with the regulator authority. This can save a lot of trouble and potential misunderstandings. The certification process is an authentic document marathon – there is a ton of technical documentation, and a seamless flow of information is important to get things done fast. Any interference in communication costs time and money.

Communication is important because the organization needs to listen carefully to the certification authority and understand where the regulator most wants reassurance. Then you can decide where to concentrate your testing and validation efforts to optimize the use of time and resources.

And I would recommend adding flexibility. During aircraft certification, you can’t expect everything to run by the book; there will always be inconveniences and change requests. Being reactive to changes and ready to rapidly reorganize or repeat tests when needed is a great strategic asset for an organization. Here, having the right test equipment and a responsive partner really makes a difference."

There is a lot of pressure to reduce time-to-market, with stakeholders wanting to see results and their vision realised. How can a data acquisition and analysis solution supplier, such as HBK, help to accelerate testing?

"I would say in many ways. The first thing that comes to my mind is data certainty and measurement confidence. The worst-case-scenario for a test lab is to fall into a position where the acquired test data is questioned by the internal/external customer or (even worse) by the regulator. That would be bad and could lead to an official test repetition request, which would not only have a significant impact on the overall project schedule, but also be a big hit for morale, and cause frustration for the entire team. That's a real nightmare for a lab organization, something to be avoided at all costs.

We, as HBK, have a strong record of successful aerospace projects and our measurement equipment is known in this market. Our hardware adheres to the highest standards and can withstand even the most meticulous auditor. We respond to any technical enquiry and we support our customers even in the toughest processes.

Then there is expertise. I cannot imagine a company in this field that can offer the amount of experience and knowledge that we have. We are domain experts in the entire measurement and data analytics chain – from sensors in the mechanical world measuring strain, force, acceleration/vibration, torque and noise over to the electrical world measuring voltage, current and temperature on high common mode onto electronics collecting all sensors and data signals offering real-time analysis and integration, and finally to software for data acquisition, analytics and collaboration – a complete eco system. We have an excellent new electrical power testing platform and the right solution for structural integrity testing – basically a one stop shop.

We know the applications very well and our customers trust us as a reliable and prepared partner. And finally, we are very passionate when it comes to aviation, and we really enjoy working with these projects making the customer’s targets our own."

A personal question: what would be the first flight you would book for an AAM service when it’s available?

"I need to be neutral here. I personally like the many technical concepts being developed right now. It reminds me of the pioneering times in aviation.
There are so many different design and propulsion concepts that I am convinced that all this energy, willingness, and enthusiasm in development will result in something good, and the chances that AAM will get a strong place in aviation are very high. It will for sure revolutionize flight training by dramatically reducing cost.

But if I really have to choose, my dream for now is still to fly in a big, powerful, twin-turbine heavy helicopter."

Gianmarco, we thank you for talking to us, that was quite revealing



Questions? Contact Gianmarco Sironi

If you have any questions regarding Advanced Air Mobility, we are here to support you.

Gianmarco Sironi is one of HBK's application experts for aircraft design and validation. He gained his knowledge from 10 years of direct hands-on vertical-lift experience in engineering and testing. Since he joined HBK he has managed many global projects for the aircraft industry.

If you have any questions, please get in touch with Gianmarco.