Developing a clean-sheet hybrid-electric propulsion regional aircraft that integrates the most promising technologies to reduce fuel consumption, noise, and emissions of carbon dioxide and nitrogen dioxide demands close cooperation with the entire aviation “ecosystem,” according to Marco Protti, head of advanced research at the aircraft division of Italian aerospace and defense group Leonardo. “If we are not in a condition to create an uptake in the market for this new aircraft, we will fail in our goal to deliver a zero-emission aircraft,” he remarked in a panel discussion on hybrid-electric regional aircraft at the recent Clean Aviation Annual Forum in Brussels.
“We cannot be looking just at the aircraft, but [we need to look at] the full system that is around the aircraft to make sure it is a possible solution for air mobility,” Protti added. Moreover, the hybrid-electric regional airliner must provide a solution that complies with the very specific environment in which it operates, Protti said, noting that the regional segment is a relatively low-cost market. “Our community customer has a very precise business case. We cannot imagine destroying this business case,“ he explained. “One of the characteristics of a regional aircraft, for instance, the ATR family, is that it is very efficient, very simple to operate, and it has a low cost of ownership for the customers. The low cost of ownership is not a secondary parameter.”
Jumping from a simple aircraft to a very complex solution that relies on a completely different maintenance system and supply chain in one step will depress market interest, Protti cautioned. “We need an evolution,” he maintained while acknowledging that “from an airframer point of view, a wrong product from the beginning is not the best step to take.” Leonardo holds a 50 percent share in ATR while Airbus owns the other 50 percent.
A founding member of the European Union’s public-private Clean Aviation partnership, Leonardo serves as the lead of the aeronautics research program’s Hybrid-Electric Regional Aircraft (HERA) project. The HERA project includes 48 partners and aims to develop a range of technologies enabling the reduction in direct, inflight greenhouse gas emissions of 50- to 100-seat aircraft by at least 50 percent compared with today’s offerings. HERA leaders project the hybrid-electric powered regional airliner would enter service by 2035.
That timetable requires the adoption of the new decarbonizing technologies by 2027 or 2028. “That is in just four to five years’ time,” Liebherr Aerospace managing director Nathalie Duquesne to last week's conference. Speaking at the same panel discussion, she called on the airframers and engine manufacturers to start making a tradeoff of the technologies so the supply chain can invest in the production ramp. “There is a lot of technology that is almost ready,” added Duquesne. “It is important that some people in the aircraft and engine manufacturing organizations have a vision of what it implies and give a strong lead. This is my message—decide on which path is dead and this one we will go with. Then we can accelerate.” Readying the production of the different components of the zero-emission aircraft will require an even larger investment from the equipment providers than the existing level of spending on new technologies.
“I discussed this with Airbus this morning,” she said. “The airframer has an idea and says, ‘maybe I will put hydrogen directly in the engine, maybe I will do fuel cells, maybe I will do hybrid-electric.’ We are just below [Leonardo] in the chain, and we have to explore all the possible solutions if we want to stay in the game. For sure, this translates into an additional R&T budget. Most system equipment providers have increased their R&T budgets by 25 to 50 percent.”
HERA remains in the process of identifying the level of hybridization of the propulsion for the 2035 hybrid-electric regional aircraft. “We are assessing the trade-offs of the technologies and what the supply chain can provide in terms of our targets on performance, reliability, and maintainability. We are exploring battery and H2 fuel cell, we are less focused on hydrogen burning engines because for a turboprop it is not the most effective solution,” asserted Protti. “We need to look at the full lifecycle of the solution…The battery itself has a quite complex environmental footprint and fuel-cell requires green hydrogen because if you use grey hydrogen the environmental footprint is worse than the current solution.”
The HERA project will develop also certification rules with the European Union Aviation Safety Agency (EASA). Clean Aviation and EASA in October last year inked a memorandum of cooperation to facilitate that process, along with for other Clean Aviation projects, such as the ultra-efficient short/medium-range airliners and hydrogen aircraft. EASA now sits on Clean Aviation’s governing board, technical committee, and scientific advisory body, which EASA executive director Patrick Ky said will accelerate the formulation of new safety rules.
According to Clean Aviation, regional aircraft-operated routes and connections account for more than 12 percent of the world's available seat kilometers. Regional aircraft now serve some 38 percent of world city pairs and perform about 40 percent of the total departures and around 36 percent of the total flown hours. Thirty-six percent of existing European airports rely exclusively on regional turboprop-operated services.