GE Highlights Hybrid Power With Transatlantic Demonstrator Flight

Thirty-eight years ago, spectators at the Farnborough Airshow might have been convinced they were glimpsing the future as a McDonnell Douglas MD-88 buzzed overhead, powered by a novel General Electric engine called the GE36 unducted fan.

But it was not to be. Falling fuel prices and modern, quieter turbofans consigned the unducted fan (UDF) to history. Instead, industry refocused on conventional ducted engines, and the GE36 was quietly shelved as a concept ahead of its time.

• Hybrid technology will feed into next-gen single-aisles 
• The demonstration flight made history as the first large-scale hybrid flight above 30,000 ft.

However, what goes around comes around, as the saying goes. Fast-forward to 2026, and GE Aerospace was back at Farnborough with not one but two flying testbeds, both of which could play a key part in development of the Open Fan, a 21st-century descendant of the UDF.

One was a modified Saab 340B megawatt-class hybrid-electric testbed that made aviation history on May 20 by flying at 30,000 ft., representing a milestone for an electric propulsion system operating at standard commercial airline altitudes. The aircraft then chalked up another milestone by becoming the first to fly across the Atlantic aided by a hybrid-electric propulsion system.

The other testbed was GE’s workhorse Boeing 747-400, which could play a role in evaluating aspects of the engine concept, possibly as part of a NASA flight-test program. The role, if confirmed, would revive plans from the start of the CFM International Revolutionary Innovation for Sustainable Engines (RISE) technology program, which involved the use of the 747 as a potential testbed for the full-scale Open Fan propulsor.

Working with CFM joint venture partner Safran, GE is focusing its future technology efforts on the Open Fan as part of the RISE program launched in 2021. The initiative targets a 20% leap in fuel efficiency for next-generation single-aisle aircraft and is set for ground and flight tests by the end of the decade.

But the appearance of the company’s testbeds at Farnborough is about more than mere technology flag-waving, GE Aerospace President and CEO Larry Culp tells Aviation Week. “Our generation is completely committed to making sure that we do invent the future of flight,” he notes. “It’s a serious responsibility for the company, the team, our investors, our customers, everybody in our ecosystem. But how do you get beyond the platitudes?

“Being able to bring the 747 flying testbed is a really good way, maybe in a conventional sense, to do that and let people see and touch what we do day in and day out in Victorville, California,” Culp continues. Referencing the Saab 340B, he adds: “The timing couldn’t have been better. So we thought: ‘Let’s take advantage of that.’”

Together, the two demonstrators are “bookends in a conventional sense and in a disruptive sense,” Culp says. “I think they will hopefully underscore that our commitment to the future flight is real and here to very tangible physical proof points.”

Externally distinguished by its inverted No. 2 (right-hand) nacelle developed by Boeing subsidiary Aurora Flight Sciences, the Saab 340B’s hybrid-electric system incorporates GE Aerospace-developed motor-generators, power converters and inverters, controllers and Avio Aero gearboxes. Fitted with Dowty propellers, Unison heat exchangers and torque sensing, the aircraft mounts a standard CT7 engine on the left-hand (No. 1) side. Lithium-ion batteries are provided by BAE Systems.

BETA Technologies served as the systems integrator, and pilots from the electric vertical-takeoff-and-landing vehicle developer ferried the aircraft to the airshow, operating in hybrid-electric mode during each leg of the journey. Originating at BETA’s flight test site in Plattsburgh, New York, the transatlantic journey began with stops at Goose Bay, Canada; Nuuk, Greenland; Keflavik, Iceland; and Wick, Scotland, before terminating in Bournemouth, England.

“The very first time we turned on the hybrid system, it worked exactly as planned on the aircraft,” says Christine Andrews, hybrid electric leader at GE Aerospace. “We were able to operate the hybrid system in flight on the Saab 340 at over 30,000 ft. altitude, both motored and generated at full power. We used the hybrid system to get to a higher altitude than what the Saab is rated for or can go to on its own CT7 power and sustain that for 2 hr.

“We were so confident in the system that we did ferry the Saab 340 over here, and we used the hybrid system on every leg of the ferry flights,” she adds. Pilots used a specially developed lever that was pushed forward to add electrical boost power for climb or faster cruise speeds, or pulled back to recharge the energy storage system. Electrical power levels were displayed to the pilots in measures of minutes.

“Our minimum viable was 30,000-ft. continuous operation,” Andrews says. “We’ve hit every technical milestone that we wanted to, but when you are able to be this successful this quickly, you kind of want to see how much further you can push it. So we’ve got a few more things we want to do when we get back [to the U.S.], and then we have a few events that we want to take the aircraft to this year before we determine, you know, its end fate.”

GE says lessons continue to be learned that will be critical for future hybrid propulsion systems. “We understand the system—GE did the battery system management, the thermal management system associated with it, all the controls that come along with it,” Andrews says.

“Understanding how that worked across the flight envelope, where we may want to use batteries, where they would buy their way onto the cycle for the foreseeable future and what we would deem is required in the way of advancements in either batteries or fuel cells is all useful,” she continues. “But just being able to know we can operate the system as designed—whether it’s battery or fuel cell, from lab to flight—is a key hallmark of the program.”

The experience will pave the way for hybrid-electric application on RISE, says Arjan Hegeman, vice president of future of flight engineering at GE Aerospace. “The really high-voltage, massive wattage power in that motor-generator at altitude is really a first,” he says. “These power and voltage levels are unlikely to be the first step in a narrowbody platform, but demonstrating this aircraft with effectively the equivalent of three CT7 engines instead of just two gives an idea of the amount of power that we’re talking about here.

“Making that work at altitude, downscaling it to lower levels, is the easy part,” Hegeman adds. “We now have this massive understanding from an operational perspective—but also from an overall electronic system perspective—at those levels at that commercial flight altitude. That sets us up really well for the future and how to deploy this in RISE.”

“For nearly seven decades, NASA has taken on the near-impossible, solved very hard technical problems and helped move new capabilities into the hands of American industry,” NASA Administrator Jared Isaacman commented. “We’re doing it again today with a new generation of hybrid-electric propulsion systems that can improve efficiency, expand capability and potentially contribute to an exciting new future in air travel.

“When NASA began exploring this technology nearly 15 years ago, many questioned whether it could ever become practical at scale,” Isaacman added. “We spent years working through the hardest technical problems: electrical components, batteries, size, weight, thermal management and the power systems needed for megawatt-class performance to make it a reality. Now, alongside GE Aerospace, we made those systems lighter, more efficient and ready for the demands of flight.”

Ground tests of the integrated propulsion system in 2022 at NASA’s electric aircraft testbed at the Neil Armstrong Test Facility in Ohio simulated operations at 45,000 ft. “But now we’re moving out of the lab and into practical application,” Isaacman said. “The engine GE Aerospace is demonstrating integrated electric motors, a gas turbine and energy storage capabilities into a megawatt-class hybrid-electric propulsion powertrain for the kinds of aircraft millions of Americans rely upon every single day.”

—With Joe Anselmo in London