Photo Info

David Solar on EASA’s regulatory framework for eVTOL certification

By Alex Scerri | July 4, 2022

Estimated reading time 18 minutes, 19 seconds.

Last week, the European Union Aviation Safety Agency (EASA) published three new documents to continue to build up its framework for eVTOL aircraft certification and advanced air mobility (AAM) operations. The proposed new regulatory framework is open to public consultation until Sept. 30.

We spoke to David Solar, head of general aviation and the vertical take-off and landing department at EASA, to give us more information on these documents, as well as the origins and future for EASA’s VTOL regulations.

German eVTOL startup Lilium is one of the original equipment manufacturers engaging with the European Union Aviation Safety Agency on eVTOL certification. Lilium Image

This interview has been edited for length and clarity.

Alex Scerri: David, can you give us a brief background on yourself?

David Solar: I started my aviation career 21 years ago at Dassault Aviation as a Falcon 7X certification engineer and later as technical support manager. I joined EASA in 2006 as a project certification manager for large aeroplanes, where I also worked on the A380 and B787 programs.

In 2017, I moved to the rotorcraft section, and in 2019, was appointed as head of department. By 2019, we already had eVTOL applicants for a couple of years, so we decided to rename the rotorcraft department to “vertical take-off and landing (VTOL).”

In 2021, we also merged the general aviation and VTOL departments, and I am heading that now. It encompasses all certification specifications (CS) because it also includes CS-25 with the larger business jets, in addition to balloons, airships, eVTOL, small aircraft, rotorcraft, and small unmanned aircraft systems (UAS). It is quite a wide scope.

Alex Scerri: When did EASA start looking into the regulations that resulted in SC-VTOL?

David Solar: Our first engagement with an eVTOL project was in 2017. We got to work to compile the first draft of SC-VTOL and opened it for public consultation in October 2018, publishing the first issue in July 2019. It was quite a challenging schedule.

Alex Scerri: What was the rationale of using a special condition rather than creating a new certification specification (CS) at the outset?

David Solar: There were several considerations. None of the existing CS were adequate. With the different architectures, some could claim they are an airplane, others a rotorcraft. In fact, most were neither. The second aspect was that placing them under an existing rule would come with a whole legacy framework that was not necessarily adapted to an innovative branch of aviation.

We also had to ensure equality of treatment. Some applications were very close to CS-23 which includes most smaller airplanes up to commuters. For example, with four passengers, it would be Level 2 with a safety objective of 10-7. Then you had others which are closer to rotorcraft, where there is no such safety continuum so would go to 10-9. We would have introduced a bias for products that were going to operate in the same environment and market.

A special condition is much more flexible. We are very much on a learning curve and this agility is necessary. Frankly, a new CS would also involve a legislative process that is not compatible with the timelines expected by these projects.

Alex Scerri: What can you tell us about the new set of documents you released last week?

David Solar: We released the second publication of Means of Compliance – 2 (MoC) Issue 2. A few items were removed, including performance data, take-off, climb requirements and landing, where there was a lack of convergence with the industry mainly on handling qualities, and these will be reintroduced in Issue 3.

We also released MOC-3 that introduces MOC VTOL.2440 – Propulsion Batteries Thermal Runaway.

The third document we released, which was the result of an extensive effort, is Notice of Proposed Amendment (NPA) 2022-06, part of Rulemaking Task (RMT).0230, to introduce a UAS and eVTOL operational framework. It is a very comprehensive document. Nonetheless, we are not reinventing the wheel as it is an adaptation of the legacy system. It is open for public consultation, and I am sure we will receive thousands of comments which, though challenging, is essential. It is not only related to operations, but also considers continued airworthiness, flight crew licensing, etc.

Alex Scerri: What else is needed to have all the regulatory blocks in place to certify and operate eVTOL aircraft commercially in Europe?

David Solar: We are already working on a third wave of MoCs. In parallel, we are actively engaged with EUROCAE Working Group WG-112, so toward the end of the summer, you should see a whole range of new standards being released. There will be specific designs that will require more exchanges, but for the wider view, I think we are reaching maturity as far as the blocks needed to certify these aircraft.

On the operational side, we need to receive and evaluate the comments for the NPA. We still have some guidance material (GM) to be issued, but I believe we are well-positioned to have all the regulatory framework in place. It will be gradual entry into service, so we will learn and iterate the rules as happened for legacy aviation.

Alex Scerri: Besides the COVID-19 pandemic, was there any factor which slowed the issuance of these documents more than you would have wanted?

David Solar EASA
David Solar is the head of general aviation and the vertical take-off and landing department at EASA. EASA Image

David Solar: The pandemic didn’t affect us so much, as we could continue most of the work remotely. We did miss some face-to-face interaction which is helpful when developing consensus standards. I think most of the time was taken to evaluate the comments we received. Some were straightforward to process but when you have contradicting views from the ecosystem, it takes more time to resolve. We have a broad set of experts that are assigned to this work, but they are not just dedicated to eVTOL, and have parallel tasks which adds some complexity.

Alex Scerri: Is the plan for SC-VTOL to become a certification specification in the future? What would be the timescale for this?

David Solar: Yes, that’s the plan. NPA 2022-06 goes from light UAS to where you could have an existing aircraft, such as the Airbus A320, converted into a remotely piloted aircraft without having to recertify the airframe. CS-VTOL, or whatever the final name will be, is also in our plans but it is a longer-term view, maybe 10 years or so down the line.

Alex Scerri: The U.S. Federal Aviation Administration (FAA) has recently announced that it will be using the 21.17(b) special class process to certify these aircraft. Will this make mutual recognition between the agencies more challenging?

David Solar: Actually, we have a positive opinion on this decision. It seemed that a lot of focus was being put on using Part 23 even if some aircraft clearly needed to go via the special class route. That could have created some inequality of treatment as I described earlier.

As we are using a special condition, I think it improves on harmonization versus the previous option. We were always open to engage with the FAA, but they seemed to be still mulling what path to take. However, now, they seem to have made their choice. What I always remind the FAA in our exchanges is that SC-VTOL did not come out of thin air but is 80% based on CS-23. This was revised and harmonized with Part 23 a few years ago with a performance-based approach, so let’s leverage that.

Alex Scerri: How many eVTOL original equipment manufacturers are in touch with EASA for projects in progress, and are any of them based in the United States?

David Solar: We have five eVTOL projects that we are engaged with, but none are from the U.S.

Alex Scerri: Which technology used in these aircraft do you see as the most challenging to certify?

David Solar: One thing we see is that the inceptors are very different between the various projects and there is no real standard. Handling qualities will also be a challenge to define and that was one reason why we temporarily removed it from the MoC. Integration is another issue because they are quite complex yet compact aircraft. Therefore, space is at a premium so proper segregation of systems is challenging.

Alex Scerri: Some eVTOL exponents think that the EASA safety objective for Category Enhanced is unnecessarily stringent at 10-9. Why and how did EASA settle on this target?

David Solar: EASA’s safety objective is from 10-7 to 10-9 depending on the usage and operation. CS-23 / FAR 23 has been designed with general aviation leisure aircraft in mind. If you see those which were in the commuter category, they were already at 10-9. We don’t see how you can relate a small general aviation aircraft which is flying a few hundred hours a year to air taxi operations where you must maximize the number of flight hours. The most successful CS-23 aircraft probably consist of a fleet of just a few thousand aircraft, but here we can expect at least two orders of magnitude greater than that.

We did not want to mislead the industry by starting at a low base and then when operations ramp up, realize that the safety objectives are not adequate anymore. It is also a matter of perception. When companies state that safety is their first objective, then they should embrace standards that promote this. The 1977 crash at the Pan Am building in New York could have well been the triggering event that subdued the urban air taxi business for years, and we want to avoid a repeat of that. We wanted to be transparent with the industry from day one, that if they wanted to operate high-density urban air taxis, then they had to satisfy this safety objective.

Alex Scerri: EASA’s roadmap for fully autonomous aircraft is in the 2035 timeframe. What are the factors you considered when defining that timeline?

David Solar: It is mainly a matter of where we expect the maturity of the technology to be. There is a lot of development in machine decision-making, etc. For these technologies to go from a non-safety critical to a safety-critical application, you need time. If you consider aviation timelines, it is not so far in the future.

Alex Scerri: Is there a regulatory framework planned or in place that would allow remotely piloted aircraft to carry passengers commercially before that?

David Solar: That’s a good question. It will depend on the cybersecurity aspects as any link to the ground is a potential breach point. It really depends on how the two technologies will develop, and we still do not have an answer if remotely piloted is better than the autonomous option.

Alex Scerri: What can you tell us about flight crew licensing for eVTOL?

David Solar: Initially, we will allow conventional licensing to bridge the gap from both the rotary- and fixed-wing sides. In this way, we will not be starting from scratch but using an established framework. A standard license will be used as a basis, that will be complemented by specific training determined from the Operational Suitability Data (OSD) established in certification to cover the type-specific items. As we gain experience, we will develop a dedicated license for these aircraft and at some point, also automation-oriented licenses as explained in NPA 2022-06.

Alex Scerri: Do you have any advice to share with the eVTOL community?

David Solar: My first message is not to be discouraged by the safety objectives. For example, when we started with the drop tests for the batteries, many people said, “This is impossible to design.” Yet, the batteries were designed and built, we drop tested them, and everything was fine. Use sound engineering principles to design your systems as per the specifications and don’t anticipate problems before you try to build and test the component.

To all the entrepreneurs who have an idea that looks great on paper, I also recommend having an organization with the proper skillset and establish that before entering the certification phase. The process will then be much smoother than taking an ad hoc and disjointed approach. We saw many established companies take this approach by having a good mix of engineers from the aviation world and others that can give a fresh look at a project.

Leave a comment

Your email address will not be published. Required fields are marked *

Teaser from our recent visit to Valley #Helicopters in Hope, B.C. #VerticalMag #Aviation #Flying

Notice a spelling mistake or typo?

Click on the button below to send an email to our team and we will get to it as soon as possible.

Report an error or typo

Have a story idea you would like to suggest?

Click on the button below to send an email to our team and we will get to it as soon as possible.

Suggest a story