We tested a tried-and-true engine on 100% sustainable aviation fuel. It passed with flying colors.

V2500 test is part of RTX strategy to increase SAF use and help meet industry climate goals

Jet-A fuel, made mostly of kerosene, coursed into the V2500 engine for the singular purpose of proving it was in good working order. 

Then the team flushed the system and got down to the real business of the day: to show the engine could also run on a pure formulation of something called HEFA-SPK – a sustainable aviation fuel derived from reclaimed fats that produces far less carbon dioxide when burned.  

There were no surprises; the engine performed exactly as they knew it would. 

The V2500, made by IAE International Aero Engines AG, is the ninth engine Pratt & Whitney has tested on 100% sustainable aviation fuel, or SAF, since 2022. (Pratt, an RTX business, is a member of the IAE consortium.) That track record – which includes testing three auxiliary power units on 100% SAF – reflects the commitment of Pratt and RTX as a whole to helping the aviation industry reach net-zero carbon emissions by the year 2050.

“SAFs are a critical lever for the decarbonization of aviation,” said Sean Bradshaw, senior technical fellow for Sustainable Propulsion at Pratt & Whitney. “They really are key to the industry achieving its environmental goals.”  

The engine that could (and has) 

The V2500 is a two-shaft turbofan engine and one of the most enduring, hardworking propulsion systems out there. Because it powers so many aircraft, it’s one of many high-priority engines being tested on 100% SAF. 

The V2500 engine: 

  • Powers commercial, military and cargo aircraft.
  • Has been in service since 1989.
  • Currently flies on nearly 3,000 aircraft.
  • Can be found on the Airbus A319, A320 and A321, as well as the Embraer C-390 Millennium. 

“This test demonstrates to our customers who are invested in the lifecycle of the V2500 that  this engine continues to play a part in IAE’s sustainability strategy,” explained Brandon Naples, associate director of V2500 Business Strategy at Pratt & Whitney. 

In addition to Pratt & Whitney, the IAE consortium includes Pratt & Whitney Aero Engines International (PWAEI), Japanese Aero Engines Corporation (JAEC), and MTU Aero Engines AG. The test took place in March 2024 at MTU’s maintenance, repair and overhaul facility in Hannover, Germany.

Brandon Naples

“This test demonstrates to our customers ... that this engine continues to play a part in IAE’s sustainability strategy.”

Brandon Naples | Associate Director of V2500 Business Strategy | Pratt & Whitney

Lessons in fuel chemistry 

There’s something in conventional Jet-A fuel that pure SAFs don’t have – at least right now – that fuel engineers are working hard to solve for: aromatics.

Aromatics are hydrocarbons that help rubber seals expand into place and prevent fuel leaks on some legacy engines. The higher the percentage of SAFs in a fuel source, the lower the aromatics. Synthetic aromatics are coming, but not yet readily available.  

“Fuels are soups of molecules,” added Bradshaw. “When you make changes to the composition of that soup, as we see with 100% SAF, you have to understand how every part works with the new combination of molecules.” 

That includes a deep analysis of the fuel’s effect on parts like seals and valves. Which is just what the IAE test team did. 

Bradshaw profile on digital mottled background

“Fuels are soups of molecules. When you make changes to the composition of that soup, as we see with 100% SAF, you have to understand how every part works with the new combination of molecules.”

Sean Bradshaw | Senior Technical Fellow for Sustainable Propulsion | Pratt & Whitney

Previous test as precedent 

They started with a strong foundation of data. Using the successful 100% SAF tests on Pratt’s GTF Advantage engine as a starting point, the team postulated that certain parts would perform similarly on the V2500.

They had a 20-plus-item punch list that predicted success in various categories, looking at fuel lubricity and viscosity, density, surface tension and thermal stability. The team was particularly interested in the wetted fuel components, or those that touch the fuel-delivery system, as they evaluated the operability characteristics of the engine.

And the best part? Everything worked well – even without aromatics. That’s because, even though it’s a more mature engine, the V2500’s sealing materials were compatible with the SAF used for the test. More extensive testing would be required to see how the engine performs on pure SAF over time.

“We did a good thing that day at MTU,” said Amar Rajbhandari, a Pratt & Whitney deputy validation manager who represented his team at the test. “It was a proud moment for the IAE team – and for me personally to see the engine perform so well.”

Fast facts about SAFs


flights used SAF in 2016


flights used SAF in 2022

600 million

liters of SAF produced in 2023 vs. 100 million liters in 2021

~449 billion

liters of SAF needed to meet the net-zero goal by 2050

Scaling up SAF production

Pratt & Whitney has been testing SAFs since 2006 and helped establish the original technical standards that allow today’s aircraft engines to operate on SAF blends up to 50%. Recently, Pratt joined an industrywide working group to address the technical challenges of running engines on 100% SAF, with the goal of setting a new technical standard for pure SAF that won’t need to be blended with fossil fuels at all. 

The next hurdle is timing. What will widespread adoption of SAFs look like and how quickly can we get there? It depends. Bradshaw explained that production and distribution will be on very different timelines, based on whether we’re talking about drop-in or non-drop-in fuel solutions. 

Drop-in SAFs can be adopted much faster – they require no changes to existing technology or infrastructure, and there would be no need to certify them individually by aircraft.

Non-drop-in solutions, which are generally more synthetic, have the potential to be even cleaner to produce, with fewer soot particles. But their vastly different chemical composition would require a lengthier adoption process.

Both will be vital in their own right. But Bradshaw said there’s a sense of urgency to establish a standard for a drop-in SAF solution now, one that’s compatible with all engines – legacy, modern and future.

“Either way,” he said, “we’ll be ready.” 

IAE team in front of test engine
Pratt & Whitney engineer Amar Rajbhandari (grey shirt, center right) stands with other members of the IAE team in front of the V2500 engine at the MTU Aero Engine facility in Germany, where they recently demonstrated the engine’s successful performance running on 100% SAF.
bottles of renewable fuel test materials

Some of the raw materials that go into today’s SAF blends include reclaimed cooking oil, plant materials and rendered animal fats. Photo by Olli-Pekka Orpo. All rights Neste.

Infographic titled 'The power and potential of SAFs'