Podcast: eSTOL Aircraft Break Into AAM Reality Index

In the most recent release of the Advanced Air Mobility Reality Index, Electra and Airflow hit the top 20 list with their eSTOL aircraft. Aviation Week's Graham Warwick and Sergio Cecutta of SMG Consulting discuss the market feasibility of eSTOL and the challenges that lie ahead.

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Here is a rush transcript of the Check 6 podcast for July 15, 2021.

Carole Hedden:          Welcome to the Aviation Week Network's Check 6 podcast. I'm Carole Rickard Hedden, managing editor of Aviation Week’s new advanced air mobility report.

Carole Hedden:          New companies continue to join the race toward advanced air mobility and most often we think of this in terms of electric vertical takeoff and landing vehicles, but just as important are other types of vehicles, including the electric ultra-short takeoff and landing aircraft and the new small regional aircraft that are beginning to develop. Today's Check 6 podcast looks at where these companies stand through the lens of the Advanced Air Mobility Reality Index provided to Aviation Week in partnership with Sergio Cecutta and SMG Consulting. The list of viable efforts hit 20 in the July Reality Index and here to discuss it with us are Sergio and Graham Warwick, Aviation Week's executive editor for technology. First off, Sergio, what exactly goes into calculating the readiness index and who's leading?

Sergio Cecutta:           Carole, first of all, thank you for having us. Quickly, there are five different factors or characteristics to calculate in the index. The first one is the funding received by the company. The second one is the experience of the team. The third is going to be the technology readiness that looks at their progress with their prototypes and with their walk towards developing a conformal prototype. The fourth is going to be the certification progress. And the last is going to be the production readiness, that is, are they ready to actually productize this vehicle and produce it. How many, they say in their business plan, that usually it's in the thousands.

Carole Hedden:          Thanks for that. Now let's turn the conversation over to the two of you. We saw two new interests in the list of 20 AAM projects this month, one from Electra and the other from AirFlow. Can you tell us more about those?

Sergio Cecutta:           Both Electra and Airflow are eSTOL or the electric short takeoff and landing. So in this case, they're not aircraft that can takeoff and land vertically. They're going to require a runway, albeit a very short runway. And we think that they are a viable alternative to eVTOLs, especially when it comes to regional, as well as middle-mile logistics, and middle-mile logistic meaning operated from one warehouse to another warehouse where, for both of them, there is very few restrictions when it comes to the space.


There is also, for these vehicles, the interest of operating in urban areas. I think we've heard that basically three landing areas for any VTOL, it's enough for one of these vehicles to takeoff and land. The interest around these vehicles is basically on three points that the companies are making. Number one, lower operating costs. The second, it's the fact that they do not need a charging infrastructure when they land. And last but not least, it's the fact that they should be easier to certify because they introduce less new and novel features.

Graham Warwick:       I think it's interesting. It’s actually a good development. We make it clear here, this is an AAM Reality Index, not a UAM reality index. And when you talk about AAM, you really have to broaden your thinking from the intracity in urban to the intercity, and also to these, as Carole said, to regional. And in fact, today, we have the announcement that [United Airlines] has placed some pre-orders, conditional orders, with Sweden's Heart Aerospace for an electric regional airplane, a 19-seat conventional airplane, just electric propulsion, short range. Because it's in the sort of 200-mile, 250-mile range, which is really in this market, we're talking about this undeveloped or abandoned market for short range air transportation.

                                   So I think you have to bring eSTOL into this because, particularly when you're looking outside of an urban environment and you are talking about intercity services, and as Sergio says, this middle-mile logistics services, that eSTOL becomes a really interesting player. And for the reasons that Sergio says, the lower operating cost fundamentally is because you're not using the battery to take off and land vertically, and you don't need the energy density or the power delivery that you need from a battery in eVTOL aircraft. So your batteries can be smaller or they can be less stressed, so they can have a longer cycle. All sorts of ways that plays out where you get more for your battery buck. More bang for your battery buck if you do eSTOL.

                                   You know, as [Sergio] says, it's easier, therefore, to charge infrastructure and all that sort of stuff becomes an easier issue, particularly if they're hybrid and they recharge [as you fly].

                                    But easier to certify--that's the one where I raise a flag because I understand the math about eSTOL versus VTOL and it really makes a lot of sense. One of these players, Electra, came out with some work that was done at MIT and was funded by Aurora Flight Sciences, now part of Boeing. Aurora Flight Sciences was founded by John Langford. Langford is the founder of Electra.aero, and they are developing an eSTOL.

                                    So they built a technology demonstrator, admittedly, a small technology demonstrator, but they built it to see whether this basic idea of powered lift using distributed electric propulsion for super-STOL performance really worked. And it did.

This thing took off in no time at all, but it was almost uncontrollable. Now it was being remotely piloted, which is not ideal. But if you watch the video, you realize that distributed electric powered lift eSTOL aircraft bring with them enormous control challenges. These things are incredibly sensitive to gusts. They are incredibly sensitive to changes in the air flow over the direction of the air flow over and under the wing ... They are enormous control challenges. So when it comes to certification, I definitely get the battery bit, I definitely get the basic airframe sort of design bit. But, you are going to need very advanced flight controls and post 737 MAX, the FAA is going to take a really, really, really close look at highly advanced, highly automated flight control systems.


Sergio Cecutta:           I agree with you that, for sure, the FAA it's going to put a lot of scrutiny [into these aircraft]. But I don't think it's just flight control. I feel that the FAA is going to put scrutiny for two reasons. Number one, the 737 experience, it didn't leave the best of feeling in the organization. But I think also the fact that this is a brand new family of aircraft, whether it's eSTOL, eVTOL, eCTOL it doesn't matter. They're new.

Electric propulsion—it's never been so developed. However, I would say that, while you're correct that eSTOLs has some challenges when it comes to their controllability as gusts and everything you've said, I think the complexity of the flight control, it's not going to be very different than if you need to control an eVTOL that has multiple rotors.

                                    What we hear is  that if you look at vertical aerospace, and I think that might be the case for most of the vehicles, we talking about a triple redundant Fly-by-Wire system. Last time I saw a three-point redundant Fly-by-Wire system [was] in F22s, F35s. And again, no one of the players has spoken to what axes are these aircraft unstable on. Usually when you talk about an F22 or an F35, we know that there is one of the axes where the stability is relaxed in order to make them more maneuverable. And so for these aircraft, no one has spoken to say, maybe it's relaxed stability in yaw or in pitch or in roll. And so, there is the need for that.

                                    And I think, at the end, it's going to be the challenge for all of them were Fly-by-Wire becomes a flight critical system. Because yes, it's triple redundant, but at the same time, if the system were to fail, would the airplane not be controllable by a human? And on that same tech, if anyone is coming out with a vehicle that is controllable in case of a Fly-by-Wire full critical failure, so all the system fail, that's going to be a big advantage because at that point Fly-by-Wire it's not critical on the certification path.

Graham Warwick:       Which, of course, brings you to Beta [Technologies], which is a little bit mysterious about what they're doing, but they do emphasize that they're eVTOL design is incredibly simple from the flight control and they've flown it pretty much only in fixed-wing mode at the moment.

But they really seem to be trying to make a fixed wing aircraft that literally only just does the vertical bit very briefly at either end. And we'll see how that plays out. But I did want to pick up something else that you said Sergio. And I think this is where eSTOL really, I think, highlights this. It's this middle-mile logistics, just logistics generally, I think, is to me, is beginning to really emerge as a potential, probably early thrive in this market, particularly when you've got the Air Force Agility Prime program. They've got some logistics demos planned with Joby and Beta and the likes.

                                   And then you look at eSTOL, then you look at... We talked about Electra but Airflow is starting off by focusing purely on this warehouse-to-warehouse logistics mission. And I think that there are so many reasons why that may be a really good early market for any of these technologies, because type certification is just one piece of the equation. The other piece of the equation is operating approvable under part 135.

                                   But also infrastructure, and cargo operations are always going to be sort of easier to get approval for because you've got a limited number of people actually involved in the operation. And secondly, when it comes to infrastructure, if you've got a warehouse, you've got a big parking lot, or you've got a big roof, or you've got something where you can more easily put in infrastructure and get a service operating, begin to build flight experience, begin to get data to the FAA so they understand what these vehicles can do, how safe they are, how quiet they are, and really get the market moving. So I do think that middle-mile logistics is going to be a really important market for both eVTOL and eCTOL. But I think that bringing eSTOL into the equation, I think, just highlights that importance of that market.

Sergio Cecutta:           I think you hit the nail on the head, Graham. We're looking at this market and we're doing some work on understanding the different news cases. And I think the use case that captured the public attention has been air taxi. However, we are starting to look at these use cases and we're dividing in two buckets, what we call push demand and pull demand. So in case of push demand, meaning there is really nonexisting demand. I don't think anyone of us went to our transportation people in our cities and say, "I want to fly to work." But at this, it's a technology push that there's a new technology available that can bring you a new form of transportation.

                                   On the logistics side, we see instead a pull demand, as in there's companies with a need, but they don't have the vehicles. And in the way that we're seen, we're doing a study to understand how would these middle-mile logistic influence by this new form of transportation. And by 2024, we could see companies like TuSimple in autonomous trucking, autonomous truck work between warehouses.

Then we can have companies like Airflow and Beta with the Alia aircraft operating in the air between these warehouses. So as you're saying, we see logistics as starting at the same time as air taxi. However, their CAGR [compounded annual growth rate], their growth rate, is going to be significantly higher, at least for the first, until 2030, 2032. Much higher than air taxi. And then air taxi will catch up. And this is, if you look at the Morgan Stanley projection, this is exactly the same thing that they project there.

Carole Hedden:          We need to wrap it up in just a second, but I wanted to ask you just one more question. We see that the top five companies in this month's list have not changed, but we did see Archer move up a bit on the list. What created that change this month?

Sergio Cecutta:           Well, until now Archer had shown drawings and so it was important for them to actually introduce a prototype that still has some way to go before it can fly. However, the introduction of the prototype, I think, it brings closer to reality the beginning of their certification.

And one other item that I think it's interesting about Archer. Archer wants to approach the entire prototype and certification more from a social media point of view. They've even talked about live streaming their flight tests. And I that's very interesting because you might appeal to the younger generation, and at the same time, maybe bring even more attention to this industry. The downside is, usually, you want to start your test on your own before you bring in the world.

Carole Hedden:          That's a great point. You can find the entire list at wwwaviationweek.com/advancedairmobilityreport. And that's going to wrap this week's Check 6 podcast, now available for download on iTunes, Stitcher, Google Play, and Spotify. Special thanks to Graham and Sergio, as well as to our producer in Washington, D.C., Donna Thomas. Join us again next week for another Check 6.

Carole Rickard Hedden

Carole Rickard Hedden was Executive Editor for custom content and Program Excellence for the Aviation Week Network, providing custom content and research to industry executives.

Graham Warwick

Graham leads Aviation Week's coverage of technology, focusing on engineering and technology across the aerospace industry, with a special focus on identifying technologies of strategic importance to aviation, aerospace and defense.