Joby Aviation received the first military airworthiness for an electric vertical take-off and landing (eVTOL) vehicle from the AFWERX Agility Prime program. (Joby Aviation)

There are questions about how realistic the predictions are concerning the commercial launch of electric vertical take-off and landing (eVTOL) aircraft in the next three to four years. While there are many factors that will determine if these timelines prove accurate, certification from regulatory bodies will be the deciding factor.

At a panel discussion during the Vertical Flight Society’s Forum 77 on May 13, experts from regulatory bodies and eVTOL manufacturers provided an update about the path eVTOL aircraft could take to achieve certification and what challenges still lie ahead.

One reason some people may be skeptical about how quickly eVTOL manufacturers are attempting to certify their aircraft is that the process is moving significantly faster than previously done in the industry.

“It took the airline industry almost 100 years to get to the level of safety, utility, and efficiency they have today and we’re trying to do it in about one-tenth of that time,” Lowell Foster, director of global innovation and engineering at GAMA, said.

Foster said the aspects of developing an aircraft must be done in parallel with each other instead of one at a time.

“We’re going to have to do everything in parallel. It’s a pretty big challenge, right,” Foster said. “Historically, you would certify the aircraft and would go through the pilot training, then you’d figure out how to operate it, and the infrastructure would follow. We don’t have that luxury today. We really need to be able to start operating these vehicles, as soon as they’re PC’d [part certified] which means we’ve got to work the training and the operations concurrently with certification. Furthermore, you know, if, we get these vehicles ready to fly and we don’t have the infrastructure, aerospace operations could be severely limited. So, it really is important we look at all these different aspects from a parallel approach.”

Several eVTOL aircraft manufacturers are currently coordinating with the Federal Aviation Administration (FAA) and the European Union Aviation Safety Agency (EASA) to find a path to certification. While eVTOL aircraft are unique, they also have aspects that allow them to take advantage of previous certifications.

“All the VTOL projects are using performance-based requirements in their cert. [certification] bases, which is a big benefit because it lets the authorities leverage means to compliance for all kinds of new technology and innovation,” Foster said. “The other good thing is that almost two-thirds of the existing means of compliance are already applicable. We are only looking at new areas for about a third of that.”

Archer Aviation’s eVTOL aircraft will use a blend of current FAA Part 23, 27, 33, 35, and 36 requirements, Eric Wright, head of certification at Archer, said. The areas where the aircraft differs from available certification requirements include unique aircraft configurations, electric distributed propulsion, energy storage and distribution systems, high voltage architecture, fly-by-wire flight control systems, advanced or automated systems, crashworthiness requirements, and noise standards.

“How are we dealing with these issues? Essentially these additional certification considerations are being dealt with by issue papers, for the most part, with all of these new and novel topics essentially being addressed through presentation of design application of standards and then regulatory collaboration,” Wright said. “There are white papers to bring up the understanding of the regulator with detailed system descriptions, and so the regulators get a good understanding of what those systems do and what other systems they talk to.”

Wright said there has been good progress with special conditions and provided the example of provisions under the FAA’s Part 41 for electric propulsion.

Archer Aviation’s eVTOL aircraft will use a blend of current FAA Part 23, 27, 33, 35, and 36 requirements. (Archer Aviation)

EASA is working on special condition VTOL (SC VTOL) means of compliance (MOC) to certify eVTOL aircraft. This process began in 2019 and is currently in phase three, David Solar, SC-VTOL lead at EASA, said. In the first two phases, the MOC addressed fly-by-wire systems, validation loads for structures, and design requirements. In phase three, which will be presented to the public later this year, Eurocae standards will be released as well as operational aspects including the development of the first EASA qualified virtual reality simulators.

One path that eVTOL manufacturers, like Joby Aviation, are choosing to take involves creating an aircraft that needs minimal exemption to currently available certifications.

“We have chosen a path that fits through the type certification path with minimal need for exemption, through the flight pilot training and qualification path through the operational path and into the airspace integration path,” Greg Bowles, head of government affairs at Joby Aviation, said.

Bowles said this thought process led them to decide to include a pilot onboard instead of building a fully autonomous aircraft like some other companies. Archer’s eVTOL aircraft will also be piloted.

“Having a pilot onboard allows us to take advantage of the existing air traffic control system, the voice communication path, it allows us to use the pilot’s traditional skills for detect and avoid,” Bowles said. “There are a whole number of technologies that aren’t actually needed to mature yet with a pilot on board.”

Joby has also classified its eVTOL with the FAA as an airplane that can take off and land vertically, Bowles said.

“So, if you think of something like an F-35, that’s an airplane,” Bowles said. “We would look at that and not say that’s a rotorcraft vehicle, we would look at that and say, oh, that’s an airplane, and it can also perform vertically.”

While these achievements mean the certification process for eVTOL aircraft is moving forward, experts expressed there are still hurdles before they can reach the finish line.

Near-term challenges could include the use of fossil fuel certification approaches for electric propulsion aircraft, Foster said.

“We’re still seeing the use of the fossil fuel mentality when we approach electric propulsion,” Foster said. “…The concern here is that we may miss an electric specific safety issue because we’re so focused on legacy.”

Another problem could be regulatory agencies’ tendency to be too conservative when considering new technologies, Foster said.

“The general tendency is for authorities to approach new technology from an absolute versus relative safety perspective,” Foster said. “…The problem with the tendency to lockstep to absolute safety is, it can present a disincentive to putting new safety devices on aircraft because of the additional costs and the additional timeframe that might be there and uncertainty too.”

Creating a certification for the use of automation could also prove to be an obstacle.

“The extensive use of automation for not just flight controls but for distributed electric propulsion and also where we’re replacing traditional pilot tasks with automation the complexity level is very high and we may need a new approach here instead of just the traditional Part 25/29 legacy approach,” Foster said. “As we get into higher levels of automation, we really have the potential to make aircraft a lot safer and maybe more human error tolerant too. We probably need to be looking at a new approach to systems or maybe a new architecture to really leverage that and so we don’t want to get too locked into legacy approaches develop in the 70s.”

Bowles said all the new technological developments might be a challenge as companies are developing.

“We get very excited right now in aviation because we’re in such a technological change,” Bowles said. “And as this evolution is happening, there are going to be infinite opportunities, and frankly that’s why there’s so much excitement around the world for this space. But the good news is we don’t want to lose sight of the path that’s right in front of us that we can execute on in the short term and how that evolves into all those different directions.”

The Mars Ingenuity helicopter completed the first flight on Mars. This photo was taken by Ingenuity and shows the ground view as it is flying. (JPL)

NASA’s Ingenuity Mars helicopter made history on April 19 completing the first powered flight on Mars, according to an announcement from the Jet Propulsion Laboratory (JPL) who confirmed the flight at 6:46 a.m. EDT today.

The flight took place at 3:34 am EDT, which is 12:33 Mars time, and was flown completely autonomously. The data resulting from the flight was transferred back to the JPL through the Perseverance rover, according to NASA.

“Ingenuity was a technology demonstrator and experimental mission but its success is truly remarkable and it gives us this new capability,” acting NASA Administrator Steve Jurczyk said during a briefing on April 19. “I believe…that we should be doing these types of technology demonstrations on all our science missions to take advantage of the ability to prove out new technologies and capabilities that will then feed forward to even more ambitious and productive missions in the future.”

The flight consisted of a three-meter climb, five-second hover, a 96-degree turn, 20-second hover, and landing, Håvard Grip, Ingenuity Mars Helicopter chief pilot at JPL, said during the briefing.

This altimeter chart shows data from the first flight of NASA’s Ingenuity Mars Helicopter, which occurred on April 19, 2021. (JPL)

“This flight was all about proving that it is possible to fly on Mars,” Grip said. “So to that end, what we had instructed Ingenuity to do was to climb to an altitude of three meters, hover there for a little bit, about five seconds, then make a turn of about 96 degrees, hover for another 20 seconds, and then go to land again in the same place that it took off from. That’s what we told engineering to do and it did exactly that. And it did it just perfectly.”

Grip said the flight is considered successful from the data JPL has received so far.

“From everything we’ve seen so far, it was a flawless flight,” Grip said. “It was a gentle takeoff, at altitude it’s gets pushed around a little bit by the winds but it really just maintained station very well, and it stuck the landing right in a place where it was supposed to go.”

Ingenuity is only four pounds, and its blade span is just under four feet. The small helicopter faced many challenges to get to its first flight including Mars’ unique atmosphere.

“When things work, it looks easy,” MiMi Aung, Ingenuity Mars Helicopter project manager at JPL, said during the briefing. “I would like to take this opportunity to remind how difficult it is to fly a rotorcraft at Mars. First and foremost, because the atmosphere there is so thin, right, about one percent compared to that at Earth. That’s like on Earth being at elevation three times the height of the Himalayas. So, the air is very thin and Ingenuity had to be really light, small and has to be able to fly in the atmosphere and survive on its own. It did all of that under four pounds.”

Aung said Ingenuity has met all three of NASA’s agency-level objectives by showing powered flight is possible on Mars, actually flying on Mars, and getting data for future generations of Mars helicopters.

“Mars helicopter Ingenuity technology demonstration project has three goals in alignment with NASA’s agency-level objectives,” Aung said. “The first is to show on Earth that it is possible to fly power controlled flight at Mars. We did that before we were launched. The second goal was to actually fly on Mars, we have done it…The third goal is to get data back that will inform engineers that are designing future generations of Mars helicopters, and we have done that too.”

Ingenuity’s flight was captured by two cameras, the Mastcam-Z and Navcam, on the Mars rover Perseverance which was parked about 211 feet away during the flight, Justin Maki, Perseverance Mars rover imaging scientist at JPL, said during the briefing. The Mastcam-Z camera recorded the video.

“It’s a 720p video and it’s 1280 by 720 pixels,” Maki said. “It runs at about 6.7 frames per second.”

The blades of the helicopter are blurred because the video has a 10-millisecond exposure time which equals about one-half rotation of the blade, Maki said. So far, they have been able to receive about 2,000 image frames from the rover.

“I can tell you from firsthand experience that that was harder than it looks,” Maki said. “In fact, I think I speak for our entire imaging team that we’re kind of relieved that we caught it in flight. We had practiced this three or four times before and this is the first time that we were able to nail it…You have two different spacecraft. They both have roughly the same time, but they operate differently, and so characterizing how the heli operates when we tell it to go, compared to how the rover does its thing is actually tricky.”

Now that Ingenuity has taken its first flight, the JPL team is planning up to four more flights in the coming weeks. The technology demonstrator has two weeks left in its planned month of experimentation.

“So, beyond this first flight, over the next coming days we have up to four flights planned and increasingly difficult flights, challenging flights, and we are going to continually push all the way to the limit of this rotorcraft, we really want to push the rotorcraft flights to the limit and really learn and get information back from that,” Aung said.

Bob Balaram, Ingenuity Mars Helicopter chief engineer at JPL, said Ingenuity is in very good shape after its first flight, possibly better shape than before.

“Ingenuity itself is extremely healthy at this point,” Balaram said during the briefing. “In fact, she’s even healthier than she was before this. She shook off some of her dust that I’ve been covering her solar panels and is in fact, producing even more solar energy than before. The batteries are looking good. The communication system is fantastic. The landing gear appears to work well. All the silver mechanisms and motors are doing great. The computers and avionics behave flawlessly. So all in all, it’s in a perfect state. And I’m just really excited to see what else she can teach us over the next few weeks as we explore aerial mobility on Mars.”

The next flights could test things like speed, distance, or how the helicopter reacts to wind. Aung said the JPL team expects to test the helicopter to meet its limits. This information will be important to allow the JPL team to find unknowns that they weren’t able to model.

“It’s also important and probably supportive of that plan to actually deal with this, like a tech demo, and we really want to be sure that when everything is said and done we know the full scope of what’s possible with that type of flying machine,” Grip, Ingenuity’s chief pilot, said. “And so for us, that’s really critical…The month of Ingenuity is very much in the spirit of a tech demo. That’s exactly what you would want to do, right, kind of to make sure that in fact, we’re putting a pedal down and are going for it.”

An added element of additional flights could be audio. This capability was available during the first flight however there was a concern that there could have been EMI interference between the microphone and the helicopter flying, Aung said.

“There is a plan to record the sound,” Maki said. “We didn’t want to put that into the first observation or the first try, because it was complicated enough just trying to get the video to work. So, we’re going to be putting that in an upcoming plan. I’m not sure if it’ll be the second flight, but it’s certainly one of our later flights.”

Right now NASA and JPL are working to gather and analyze all the data from Ingenuity’s first flight and that will inform the next flight which could be as soon as Thursday, Grip said.

“We’ll get the high rate data downlink from the helicopter to us tomorrow, and then we will be attempting to fly within the next few days,” Grip said. “So we’re targeting for this Thursday but we’ll know more after we get the high rate data.”

The Mach 6 quiet wind tunnel at Purdue University. (Purdue)

The Air Force Research Laboratory (AFRL) is partnering with Purdue University and the University of Notre Dame to conduct hypersonic research in key areas including the transition from laminar to turbulent flow, predicting the heating of turbulent flow, systems engineering, and propulsion, Jonathan Poggie, a professor in the school of aeronautics and astronautics at Purdue University and leader of the hypersonics program, told Aviation Today. The research will be used for any military vehicle or object flying at hypersonic speeds.

Purdue and Notre Dame were chosen specifically to participate in the $5.8 million program because each of them have separate Mach 6 (about 4,500 mph) quiet wind tunnels and combustion facilities. The multidisciplinary effort emphasizes the pressure to move fast and get stuff done, Poggie said.

“The key thing that I would emphasize in this being unique is while it involves so many institutions and it’s multidisciplinary, we’re not just doing ordinary academic research,” Poggie said. “We’re putting together many different fields to try to make the whole that’s bigger than the parts.”

Two of the projects the program is focused on involve the transition from laminar to turbulent flow for next-generation high-speed vehicles capable of flying at Mach 5 and beyond. When laminar flow, which is smooth and quarterly in layers, transfers to turbulent flow, which is chaotic, it is very difficult to predict the transfer rates, which can be a factor of 10 higher when in turbulent flow over laminar flow, Poggie explained.

“The idea there is that transition from laminar to turbulent flow describes features particularly sensitive to external disturbances and particular sound,” Poggie said. “A conventional wind tunnel is very noisy, that when it runs you can actually hear the rumbling, and that turbulent flow on the sidewalls of the tunnel contaminates the flow field, creating an unrealistic disturbance environment that’s not representative of light. These tunnels [Mach 6] are specially designed to reduce that noise field to a minimum that’s very close to what you get when you actually fly through the atmosphere.”

This research will be led by Joseph Jewell, assistant professor of aeronautics and astronautics at Purdue, and Thomas Juliano, associate professor of aerospace and mechanical engineering and Notre Dame.

Sally Bane, associate professor of aeronautics and astronautics at Purdue, will be leading the program’s research into how to improve the capability of designers to predict heating of turbulent flow using computer models. This is important because it will determine what materials will need to be used in a hypersonic vehicle.

“We’ll be trying to predict those measurements with the best available computer models and see how we can help improve the capability of making this prediction so when designers go to design a hypersonic vehicle, they know the level of heating they can expect from flight,” Poggie said. “That’s important for us to know that and have an error bound on the value because otherwise, they have to use a very conservative design and a conservative thermal protection system is heavy and reduces the vehicle performance.”

According to Poggie, the program will also include a system engineering project which will examine how different design aspects can mitigate heat transfer. The project will take an integrated approach examining all parts of the design including aerodynamic structures, flight controls, and the internal systems of the vehicle. This project will be led by Dan DeLaurentis, director of the Institute for Global Security and Defense Innovation (i-GSDI).

“Disciplines including aerodynamics, aerothermal effects, and propulsion all can come into play when a vehicle is flying at hypersonic speeds,” DeLaurentis said in a press statement. “Multidisciplinary research is a point of emphasis for the i-GSDI and the Department of Defense.”

Carson Slabaugh, assistant professor of aeronautics and astronautics at Purdue, will be leading the programs work in scramjet combustion experiments.

The multidisciplinary effort involves a total of 16 researchers between the universities and it will be Poggie’s job to coordinate these efforts to create a cohesive result.

“We all have a big history working together and that’s what enabled this all to come together,” Poggie said. “People knew each other, and they had confidence working with each other. And then we have a good set of leads for each of the tasks… That hierarchy will hopefully allow me to not have to have my hands in every single project.”

The HYPULSE donated by Northrup will allow for flight simulations from Mach 5 to Mach 40. (Purdue)

Earlier this year, Purdue was awarded $5.9 million by the AFRL to develop a Mach 8 wind tunnel, and Northrop Grumman donated a Hypersonic Pulse (HYPULSE) shock tunnel to the university in October. The HYPULSE will allow flight simulations from Mach 5 to Mach 40, which is fast enough to allow a plane traveling from Washington, D.C. to fly to California in just 15 minutes. Purdue is only the second university to have one of these wind tunnels.