As the aviation industry shifts towards sustainability, more manufacturers are developing electric engines to move away from jet fuel. However, despite years of developments on the industry side, civil aviation regulatory authorities have yet to actually certify one of these aircraft.
The aircraft manufacturers are at the mercy of regulatory authorities when it comes to certification and some say it is the only thing stopping them from entering into service. During a panel at the Vertical Flight Society’s Electric Aircraft Symposium on July 21, industry and regulatory experts explained what challenges still exist for electric aircraft certification.
“The only thing that’s stopping us today from operating UAM [urban air mobility] aircraft is to a get an aircraft through certification, that is going to be the pacing item,” Martin Peryea, chief executive officer at Jaunt Air Mobility, said.
Peryea cautioned that aircraft manufacturers need to establish a certification basis before designing their aircraft to avoid future problems.
“From a design perspective, you have to actually establish your certification bases before you start designing,” Peryea said. “Unless you really fully understand, how you’re going to certify the aircraft into what rules, it is hard to layout an aircraft architecture from a systems perspective until you could have a full understanding.”
Some manufacturers like Jaunt plan on certifying their aircraft under existing rules like Part 29 and 135, however, they will need a special condition to certify their electric engines.
The Federal Aviation Administration (FAA) has been working on creating a special condition for electric engines to provide a guide to certification for electric engine manufacturers, Gary Horan, an aerospace controls systems specialist at the FAA, said during the panel. Horan said the FAA has been working with one company in particular to develop this special condition, magniX.
“We are working at the FAA…to get a special condition issued for the first project to certificate an electric engine,” Horan said. “This special condition is written around one particular company and their product, and to be honest with you, we don’t know if they’ll be the first ones to cross the finish line, but, you know, we had to pick a horse and that’s what we did.”
Horan said the special condition is based on an American Society for Testing and Materials (ASTM) standard. He said the terminology is important to consider when talking about certification because the FAA is certifying an electric motor, not electric propulsion.
“This special condition was developed based on an ASTM standard that we put together over a span of a year, two years, probably longer than that…and it was for what was called at the time electric propulsion, well that terminology is going away,” Horan said. “It is an electric engine that we’re talking about and that makes a huge difference for the FAA, and for [European Union Aviation Safety Agency] EASA by the way, because that’s the only thing we can certify is an engine. We can’t certify an electric propulsion unit because that’s the way the rules are written.”
One change that the FAA has made is anyone who wants to certify an engine will have to provide information on what aircraft that engine is going in, Horan said. This is based on the agency’s effort to increase safety standards.
“We are changing one aspect of what we require relative to the engines and safety that we have not required in the past,” Horan said. “If you try to get a type certificate for an engine, you have to do the safety assessment of that engine and you have to project what the rates of failure will be and whatnot. You are now being required to know where it’s going to be installed. You have to know the aircraft because you have to take into account the objectives that the aircraft needs to make to stay safe. So we’ve broadened the scope of the safety assessment, at least at the engine level, but I think what that is going to do is it’s going to reach across to the aircraft level as well.”
Releasing this special condition will allow manufacturers to have guidelines to follow for engine certification. Lowell Foster, director of global innovation and engineering at the General Aviation Manufacturers Association (GAMA), said without this certification basis, manufacturers are still left with more questions than answers while trying to design a vehicle.
“The FAA has been a lot more challenging in terms of getting cert basis out and getting agreement with what the means of compliance are, which leaves these questions lingering while you’re trying to design a vehicle,” Foster said.
However, there are many other areas where manufacturers are still unsure of certification standards. Foster said one example of this is the FAA’s flight standard which is going to apply power-lift requirements to electric vertical take-off and landing (eVTOL) aircraft.
“The big one that we just found out about is that the FAA flight standard is going to apply powered lift to our fixed-wing VTOL aircraft,” Foster said. “We don’t know what that means yet, other than we’re having to go down a lot more substantial exemption routes. It will also not just be leveraging new generation sims, but it’ll make using simulators and flight training devices a lot more important.”
Another challenge for the FAA is the varied design architectures from one aircraft to the next.
“It’s absolutely amazing how many different variations there are,” Horan said. “There are very few applicants that have come to us, that have the same thing that somebody else has. It’s like everybody’s got a slightly different spin on it.”
While electric aircraft have made strides in recent years, Horan said the biggest issue they still face is power supply.
“I think the largest issue that they’re all faced with is the power resource, meaning where are you going to get the energy, how you’re going to manage that,” Horan said. “Total battery operation is extremely appealing because it seems like it’s the quickest way to get there, but the battery technology has still got a ways to go to make it a cost and economic benefit and impact on a range. So I see that as being really the biggest issue.”
Foster said that he is concerned about the issues that aren’t front and center right now.
“My concerns are with certification too and not so much the ones that are obvious because I think it’s pretty easy to look across some of the new technology and say these are going to be certification issues, and so we’re focused on those but having watched cert programs for a long time, it’s the little stuff that you’re not watching that bite you in the end,” Foster said.
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