The assessment began with a baseline test using traditional Jet-A fuel to ensure the engine was functioning properly. After confirming the engine’s performance, the system was purged, and the focus shifted to testing the engine with HEFA-SPK, a sustainable aviation fuel derived from reclaimed fats known for significantly reducing carbon dioxide emissions. The results were as expected: the engine operated flawlessly.

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

Since 2022, Pratt & Whitney, in collaboration with IAE International Aero Engines AG, has tested nine engines, including three auxiliary power units, on 100% SAF. This initiative is part of Pratt & Whitney’s commitment to reducing the environmental impact of aviation.

The V2500 engine, a robust two-shaft turbofan in service since 1989, powers various commercial, military, and cargo aircraft, including the Airbus A319, A320, and A321, as well as the Embraer C-390 Millennium. With nearly 3,000 aircraft using this engine, it is a high priority for SAF testing.

“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.

The IAE consortium, which includes Pratt & Whitney Aero Engines International, Japanese Aero Engines Corporation, and MTU Aero Engines AG, conducted the test in March 2024 at MTU’s facility in Hannover, Germany.

One of the challenges of SAFs is the absence of aromatics, hydrocarbons found in conventional Jet-A fuel that help rubber seals expand to prevent leaks. “Fuels are soups of molecules,” said 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.”

The team used data from previous 100% SAF tests on Pratt’s GTF Advantage engine to predict performance on the V2500. They examined fuel properties such as lubricity, viscosity, density, surface tension, and thermal stability, focusing on components in contact with the fuel. The test showed that the V2500’s sealing materials were compatible with SAF, even without aromatics. More extensive testing is needed to evaluate long-term performance.

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

Pratt & Whitney has been pioneering SAF research since 2006, contributing to technical standards that currently allow aircraft engines to operate on up to 50% SAF blends. The company is now part of an industry working group aiming to establish standards for 100% SAF, eliminating the need for fossil fuel blends.

Bradshaw emphasized the urgency of developing a drop-in SAF solution compatible with all engine types to expedite adoption. “Either way,” he said, “we’ll be ready.”