Resurrected GE propfan offers a 20% boost to aircraft fuel efficiency

General Electric has brought the propfan engine back from the dead as part of a joint venture with Safran Aircraft Engines.
Christopher McFadden
Concept image of the new engine.


General Electric (GE) has announced its intention to work with CFM Rise (a 50:50 joint venture with Safran Aircraft Engines) to develop and build a super-efficient "propfan" engine that promises to deliver 20% fuel saving over conventional turbojet engines. Also known as unducted fans or open rotor engines, this is not a new technology, but anxiety around fuel prices and the drive for net zero has resurrected the concept.

First conceived in the 1970s, the propfan design made significant progress in the 1980s before being mothballed. They also look a little strange, with smooth nacelles, air intakes at the front, and two sets of fan blades poking out into the open air at the back. However, the fuel efficiency they promise is not something to be sniffed at.

Propfans are not a new technology

Propfans generally feature numerous blades that are often heavily twisted and swept back, with the rear blades twisted opposite to the front blades. Some models utilize counter-rotation, while others have stationary blades that serve as variable-pitch stator blades to enhance flow recovery.

According to a whitepaper from GE, advancements in aviation propulsion have been made by utilizing new technologies that enable larger fan sizes and higher bypass ratios. The propfan design combines the fuel efficiency of a turboprop with the speed and performance of a turbofan, achieving both capabilities.

Recently, fuel prices have increased greatly, and the aviation industry is now focused on reducing the carbon footprint of its energy-intensive business. This has led to a renewed interest in propulsive efficiency. While batteries and hydrogen cannot fully replace kerosene as an energy source, increasing the mileage has become crucial. As a result, in collaboration with Safran Aircraft Engines, GE introduced a new UDF airliner engine called the "Rise" in 2021.

Although the aviation industry has made significant progress in efficiency over the last few decades, GE claims that its "Rise" engine will still provide 20% more mileage than any other engine currently available for a given amount of energy. Previous propfan designs have been criticized for creating excessive noise both inside the cabin and on the ground. Still, the CFM team assures that the "Rise" engine is being thoroughly tested to meet the most rigorous noise emission standards.

They offer significant fuel savings, however

“The industry can’t reach its net zero ambition by 2050 with status quo incremental improvements in fuel efficiency," says Mohamed Ali, vice president of engineering for GE Aerospace. "Revolutionary technologies are needed. That’s why we believe the time for [an] open fan is now, an advanced engine architecture that could unlock the single greatest jump in generational engine efficiency that CFM has ever achieved. This is supported by our most comprehensive testing roadmap yet to prove out and mature these technologies for the future of flight,” he added.

The "Rise" engine is highly adaptable and can be conveniently installed on the top or bottom of an airliner's wing. The team has partnered with Airbus to develop an open fan demonstrator, expected to take flight in the mid-2020s. Until such time, GE has built some prototypes, and CFM has conducted around 400 ground tests. In the meantime, GE Aerospace has been doing intensive simulation work and recently revealed in a press release on Friday that it is utilizing the world's "fastest supercomputer."

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