Flying forward: advances in aviation

From radical engine design to innovative materials, could transformative technologies make air travel more efficient over the coming decades?

On a drizzly morning in May 1927, a crowd at Roosevelt Field on Long Island collectively held its breath as a silvery monoplane bounced along a muddy field, lumbered into the air and, heavy with fuel, barely cleared the treetops at the end of the runway. An astonishing 33 hours after this humble start, Charles Lindbergh landed in Paris, completing the first solo nonstop transatlantic flight and ushering in the era of commercial passenger aviation.

Now, as the industry prepares to mark the 100th anniversary of the flight, aviation is on the brink of another transformation. Lindbergh designed his plane for maximum efficiency – to stay aloft as long as possible. Airlines, too, must keep their fleets in the air to earn revenue. And fuel remains an ever-present concern, now accounting for up to 40 per cent of an airline’s operating costs. A new wave of innovation promises to address these challenges and more, starting with propulsion.

Propulsion breakthroughs

The aviation industry is exploring a range of new approaches to flight, from air taxis with vertical take-off and landing and self-flying planes, to hybrid electric-and-fuel-powered jets and Open Fan engines with exposed blades. “Everything is exciting,” says Mark Ricklick, Associate Professor of Aerospace Engineering at Embry-Riddle Aeronautical University who researches and teaches aircraft propulsion.

It’s not just talk. Governments and private companies are spending billions to get such designs off the ground in the near term. For example, the Clean Aviation Joint Undertaking is a €4.1bn public-private European program focusing on sustainable aviation. The mission? To perfect technologies to make flight dramatically more fuel efficient.

Axel Krein, Executive Director of Clean Aviation, a partnership between the European Commission and partners from the European aviation industry including CFM International (a joint venture between Safran Aircraft Engines and GE Aerospace), SMEs and academia, says Clean Aviation is developing multiple groundbreaking technologies in areas such as propulsion, aerodynamics, structures and systems.

CFM is betting big on one technology in particular. The Open Fan design represents a departure from that of conventional jet engines. Unlike traditional ducted engines enclosed by a nacelle, Open Fan configurations feature exposed fan blades that resemble oversized propellers. The architecture unlocks bypass ratios – a measure of how much air bypasses the engine core versus how much is combusted – that are unachievable in ducted designs, delivering significant efficiency gains.

“Among emerging technologies, Open Fan engine architecture is expected to have the largest impact in the coming decade “

Among all emerging technologies, Open Fan engine architecture is expected to have the largest impact in the coming decades,” says Jérôme Bonini, Vice President of Research and Technology at Safran. CFM is advancing Open Fan and a suite of other engine technologies through Clean Aviation and other international programs for future aircraft. 

Additional breakthroughs in progress include hybrid propulsion and so-called compact cores. Hybrid systems combine traditional combustion with electric power, providing another way to reduce fuel consumption (and potentially quieter take-offs and landings). Compact cores – smaller, more efficient engine centers operating at higher temperatures and pressures – complement the Open Fan architecture by maximizing thermal efficiency.

All these technologies can work in concert to push the envelope in aircraft propulsion. Bonini notes that they can also work with sustainable aviation fuels (SAF) to further reduce carbon emissions. “As an engine manufacturer, we are working to maximize the usability of SAF,” he says. “This involves both defining fuel formulations compatible with existing technologies and adapting engine and fuel system materials to maintain performance.”  

Krein adds: “The ambition is to deliver a further 20 per cent improvement in efficiency within the next decade – nearly double the rate of progress compared with earlier generations. Revolutionary new engine technologies, either unducted or ducted, mark a real turning point, not just for the industry but also for society as a whole.”

From concept to operation

Bringing such new technologies from laboratory to commercial service presents significant challenges. One of these is integration with the airframe. The larger fans will require adjustments in airframe design, for size and, additionally, to address the potential safety concerns of passengers who will be able to see them whirling away outside the windows.

Bonini says: “The introduction of disruptive architectures such as the Open Fan presents significant challenges and opportunities. But absolute flight safety is the priority. Certification of new technologies remains the top priority and requires extensive and rigorous testing and validation.”

CFM has already run more than 350 tests on new blade designs and other technologies, Bonini says. “Test results that are continuously feeding advanced modelling capabilities, allowing us to refine and correlate models, are now feeding the engine demonstrator preliminary design.” The designs also benefit from hundreds of hours of wind tunnel testing, run at sites across Europe. Ground and flight tests for the new engines are planned for an Airbus A380 as a flying test bed.

“Certification of new technologies remains top priority and requires extensive and rigorous testing and validation.”

For airlines, these advances could translate into substantial operational savings. Beyond the fuel efficiency gains, newer engine architectures may require less maintenance and deliver lower overall costs, according to Bonini.

Krein says there are also substantial benefits for the environment. “Clean Aviation aims to achieve a 30 per cent reduction in greenhouse gas emissions in advanced aircraft by 2035 [compared with 2020 state-of-the-art technology], with a target of replacing 75 per cent of aircraft fleets by 2050. When combined with sustainable aviation fuel, CO2 emissions could be reduced by up to 90 per cent.”

Despite the radical departure from conventional engines, noise levels must remain lower than those of standard jet engines, according to Bonini, who says Safran has been conducting listening tests with positive results. The altered aircraft configurations required to accommodate larger-diameter engines could also create opportunities for more spacious cabins, though such changes would depend on decisions by airframe manufacturers.

As these technologies take flight, in the near future onlookers may witness long-haul jets with exposed fans roaring off runways or electric air taxis floating down to rooftops without a sound – sights potentially as striking as Lindbergh’s Spirit of St Louis was in 1927.

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Flying forward: advances in aviation