Embraer Narrows Down On New Turboprop Definition, ATR Defines Upgrades

While the Boeing-Airbus duopoly remains in the large commercial aircraft market, regional aviation has seen massive change of late: Mitsubishi shelved the SpaceJet project, production of the Bombardier CRJ family has ended, and de Havilland also decided to stop manufacturing the Q400 turboprop, at least for the time being. All these changes have left two manufacturers with segment monopolies—Embraer for regional jets and ATR for turboprops.

• Embraer works toward 2022 launch of new turboprop
• ATR makes progress on substantial incremental changes
• Both OEMs explore hydrogen power transition options

Given the circumstances, one might not expect quick moves into new aircraft programs. After all, the industry is in a phase between what is now considered legacy or traditional, the old way of doing things, and the revolutionary, transformative technologies that will become available at some point down the road. Now, any new program taking the wrong bets risks being overtaken by superior competitors in the not-too-distant future, which makes it harder to recover investments. However, while no new traditional regional jets are on the horizon, the situation could be different for turboprops soon. 

Embraer continues to work toward a 2022 launch of its large new turboprop, a project that—if realized—will almost certainly spur a reaction from ATR and would also set in motion a new development cycle for engine manufacturers.

After studying a large new turboprop concept for more than two years, Embraer has recently decided important changes to the architecture that it hopes will achieve two goals: revive the U.S. turboprop market and thereby make the business case for it more compelling and enable the aircraft to compete for decades to come by preparing it for eventual liquid-hydrogen propulsion.

Embraer had most recently presented a low-wing aircraft concept using the E2 fuselage diameter and wing-mounted engines. But the OEM is now pitching an aircraft with engines mounted at the rear, much like the 50-seat ERJ-145 regional jet or the ill-fated CBA 123 Vector—a 1980s turboprop project that was terminated during flight testing and after causing huge losses.

“We would only change the configuration if we discover any roadblocks,” says Rodrigo Silva e Souza, Embraer Commercial Aviation’s vice president of marketing. So far none have been found.

The aircraft under discussion is a family of two versions of 70 and 90 seats in single-class configurations able to fly ranges of up to 800 nm but typically pitched and optimized toward much shorter sectors to avoid competition with Embraer’s regional jets. A big part of the aircraft-maker’s target market are aging 50-seat jets flown by U.S. carriers. Depending on cabin layout, the turboprop can either offer more seats or more comfort. Embraer is showing studies of three-class configurations including a domestic first-class cabin, premium economy and coach that feature 50 seats in the smaller version and 76 seats in the larger.

When Embraer presented the proposal using wing-mounted engines, it did not gain traction with U.S. regional airlines. Executives cited the flying public’s turboprop avoidance as a major concern: The aircraft simply looked too similar to what people have not liked in recent decades.

With the new layout, “we started getting different reactions,” Silva e Souza says. “It looks more modern and more advanced than the traditional configuration.” The response among potential customers has been “excellent,” he says. Embraer estimates the U.S. 50-seater replacement market makes up about 500 aircraft alone. If Embraer could win a big part of that, the business plan for the turboprop would be much easier to close.

Perception is important, but other factors have played a role, too. With the engines in the back, Embraer argues the aircraft will be compatible with air bridges used for regional jets at many U.S. airports and the cabin can be quieter, an important element if airlines want to attract first-class and premium-economy flyers even on thin regional routes.

The other main consideration for the redesign is future propulsion technology. Embraer has come to the conclusion that “for this size [of regional aircraft] the future is hydrogen,” Silva e Souza says, noting that the proposed turboprop will be too big for electric or hybrid-electric propulsion. The aircraft would be designed to use sustainable aviation fuels (SAF) in the short term and be easily reconfigurable for liquid-hydrogen propulsion in the long term. “It is important to think about what will be the evolution of the platform,” Silva e Souza adds.

Embraer also expects development of fuel cells will not come fast enough for the project, so plans call for a large liquid-hydrogen tank at the back of the fuselage, with the proximity to the engines minimizing the need for tubing and reducing weight. Embraer has not decided yet whether it would accept a smaller passenger cabin when more space is needed for the tank. Alternatively, it could make provisions for the aircraft to be stretched to accommodate the same number of passengers and a tank big enough to ensure the targeted ranges.

While the aircraft is being designed for a maximum range of 800 nm, most sectors will be 250-300 nm, according to Silva e Souza.

The ability to fit larger propellers because of the higher ground clearance has not been a factor in the discussion. However, having the engines at the back has other operational advantages beyond compatibility with air bridges: The aircraft can sit lower on smaller landing gear, making baggage handling easier at small airports with little or no special ground equipment.

Preparing the aircraft for hydrogen propulsion is not the only revolutionary element in an initially conventional concept. Embraer is also looking at designing a cockpit that would enable single-pilot operation once aviation authorities certify it and passengers accept it.

Embraer also plans to study the potential for a freighter version. “There is now a much bigger recognition for cargo needs because it has become a bigger part of the airline business,” Silva e Souza says.

The manufacturer aims to launch the two-member aircraft family in the second half of 2022, with entry into service following in 2027 or 2028. However, a lot of open questions remain before Embraer can formally commit. The design needs to be frozen, and what the company describes as much better feedback from its customers needs to be turned into firm orders. Replacing 50-seat regional jets would be a big step for regional airlines.

Embraer needs buy-in from suppliers, too. When the company planned to sell control of its commercial aircraft business to Boeing, it argued that the unit could not survive on its own in the long term, particularly after Airbus had acquired the Bombardier C Series program, now called the A220. Suppliers, which are planned to participate as risk-sharing partners, and financial investors are contributing to the funding. “We see strong interest in the aircraft from partners,” Silva e Souza says, adding that “it may be the only new platform from any OEM.”

ATR, meanwhile, is going ahead with an extensive incremental improvement of its ATR 42-600 and ATR 72-600 turboprops in the 40- and 70-seat classes, respectively.

The most significant program in that strategy is the ATR 42-600S, a short-takeoff-and-landing version of the smaller model. It is targeted at enabling the use of an 800-m (2,600-ft.) runway with “more than 40 passengers,” the company says. The precise number of seats, between 40 and 48, will be determined with flight testing, says Stephane Viala, ATR’s senior vice president of engineering.

ATR says it has modified the -600S’ development schedule to “realign with customer needs.” Certification has been postponed to early 2024 from mid-2023 and a pre-pandemic goal of 2022. Entry into service is now slated for “some time in 2024,” Viala says.

As announced at program launch in 2019, Air Tahiti is the launch operator, and Elix Aviation Capital serves as launch lessor.

The detailed design phase has been completed, and the first parts are being produced and are expected to be received this year. An existing prototype aircraft will then begin to be modified.

Additional -600S features will be progressively integrated and evaluated. The automated braking system and the spoilers will be among the first. A new-generation multifunction computer will replace an old design and centralize flight warnings. The aft fuselage is to be reinforced, enabling the aircraft to accommodate a larger rudder, which is necessary to cope with thrust asymmetry in case of engine failure. The -600S will use its Pratt & Whitney Canada PW127Ms at a higher power rating. The new rudder will be installed in mid-2022, Viala says, after which a one-year flight-test effort will commence.

Reducing direct maintenance costs (DMC) is a key part of the improvement project. As a result, the interval between C checks has been increased from 5,000 to 8,000 flight hours.

A new air management system provides lower DMC, in addition to enhanced reliability and greater comfort. Supplied by Liebherr Aerospace, it was certified on the ATR 72 passenger and freighter variants last year. It will be certified on the ATR 42 this year or later, depending on the launch customer’s need.

More changes can be expected at engine and nose landing gear levels,  Viala says, adding: “Every major component is reviewed with cutting DMC in mind.”

All maintenance documentation was digitalized in 2020. “Thanks to tools such as hyperlinks, contextual menus and integration into an operator’s maintenance information system, using digital documentation is more effective,” Viala tells Aviation Week. “ATRs now rely on the same platform as the Airbus A350.” ATR will update only the digital maintenance documentation for its aircraft types.

The improvement project goes as far as considering other fuels and modes of propulsion. “Our time frame extends to 2040,” Viala says.

ATR is betting on SAF to contribute to decarbonizing the sector in the short term. The ATR 42/72 is certified to run on a 50% SAF blend. Despite the conundrum of SAF procurement, ATR and Pratt & Whitney Canada engineers are working on the use of 100% SAF with current engines by 2025.

The challenge can be tackled in two different manners, Viala says. In one, engineers plan on the fuel composition to remain in the current specification, he says. Additives could meet the need for the fuel to help engine lubrication. Those additives are similar to existing ones in conventional fuel and generate some pollution. However, such SAF would be very close to conventional fuel and relatively easy for standardization organization ASTM to approve, says Viala. The only remaining technical challenge would be the different density, which would entail a modification to the gauging system.

The second way to enable the use of 100% SAF is to find a solution without the additives. ATR’s engineers are studying the effect on lubrication, as well as seal aging.

With Swedish carrier BRA and SAF producer Neste, ATR is planning to perform a demonstration flight in 2022. The aircraft will run on 100% SAF in one engine and 50% SAF in the other. The calculated emissions-reduction stands at 64%. In 2019, a BRA-operated ATR flight used a 50% blend of SAF.

For the longer term, an electric aircraft relying on batteries is not considered likely because of their low specific energy, measured in Watt-hours per pound.

On the other hand, hydrogen could work as an incremental change, Viala says. It could be used either in a fuel cell or a gas turbine engine. ATR’s engineers are investigating the technical, economic and operational feasibility of both concepts. The fuel cell would feed electric power to a motor connected to the gearbox. The propeller could thus be driven by both an electric motor and turbine engine in a parallel hybrid architecture. In a gas turbine engine, hydrogen would burn in a modified combustor. The system would have to cope with the longer flame hydrogen generates.

Even more daringly, ATR is considering a dual kerosene-hydrogen combustor that could burn both types of fuel and allow ATRs to continue to fly to major as well as small, remote airports, Viala emphasizes. Whether a dual combustor can be designed has yet to be demonstrated, he notes.

In any case, aviation hydrogen would have to be produced in an environmentally friendly fashion. And it could be directly used as a fuel or combined with captured CO₂, Viala says. In the latter case, it would form synthetic kerosene (also known as power-to-liquid or e-fuel, which belongs to the SAF family).

Maybe to give it more visibility, the incremental approach may translate into a product unveiling early next year. “We are considering different options,” says CEO Stefano Bortoli. “I think we will have something to share at the beginning of 2022. At the maximum, we are targeting something that could be on the market in five years.”

Sources at two major ATR suppliers confirm such an announcement may be expected.