Leonardo Helicopters and Pratt & Whitney Canada (P&WC) have flown an AW139 intermediate-twin with one of two PT6 engines burning sustainable aviation fuel (SAF) in order to study engine performance with the new fuel source.

Performed on 21 November, the AW139 took off from the airframer’s headquarters in Cascina Costa in northern Italy, Leonardo and P&WC said on 7 December. The flight and associated ground tests lasted 75min.

The companies say the aircraft burned “100% sustainable aviation fuel” but clarify that one of the twin-engined AW139’s PT6C-67C engines burned traditional fossil-based Jet A1 fuel. The other engine burned the 100% SAF – a biofuel called Hydro-Processed Esters and Fatty Acids Synthetic Paraffinic Kerosene.

“We did the first flight burning 100% SAF in one engine and will repeat the test with both engines,” Leonardo says.

Leonardo-PW&C AW139 SAF flight

Source: Leonardo Helicopters

Leonardo Helicopters and P&WC completed the first 100% SAF flight of an AW139 on 21 November 2023

The team “evaluated engine performance at multiple power levels” and the turboshafts ”demonstrated no significant differences in the response to the new fuel compared with the use of Jet A1”, P&WC says.

Many in aviation view SAF as key to their ability to achieve net-zero CO2-reduction goals by 2050, which they say has 80% lower “life-cycle” CO2 emissions than fossil fuels, though several reports have questioned the actual viability, feasibility and sustainability of SAF.

P&WC president Maria Della Posta says the AW139 flight as a step toward ensuring PT6 engines operate properly when burning SAF, which is typically biofuel produced from used cooking oil, grain or other biomass.

“Proving the engine’s capability with drop-in SAF provides the foundation for the future of the PT6 in sustainable aviation and builds on its legacy of success,” she says.

“We are demonstrating how we can support the rapid evolution of sustainability requirements in aviation as the industry aims at a greater use of SAF in operations,” adds Leonardo Helicopters managing director Gian Piero Cutillo.

Leonardo-PW&C AW139 SAF flight

Source: Leonardo Helicopters

Flight and ground tests using 100% SAF lasted about 75min

Several industry players recently completed SAF-flight milestones. On 28 November, Virgin Atlantic flew a Boeing 787 powered with SAF from London to New York, albeit without any paying passengers on board. On 19 November, Gulfstream achieved what it said was the first transatlantic flight of any aircraft burning 100% SAF – operating a G600 from Savannah, Georgia to Farnborough in England.

Despite industry enthusiasm, SAF remains prohibitively expensive – from two to nine times more than fossil fuel, a recent study found – and production remains meagre.

One recent report also said few SAFs hit carbon-reduction targets and that different groups use varying methods to estimate CO2 benefits, with widely differing results.

Other reports have warned that crop-mass needed to support large-scale SAF production would require conversion of food-crop land to SAF-crop land, inflating food prices, or deforestation. Methods of producing non-bio-based SAF exist, such as the carbon-capture method. But such technologies remain prohibitively expensive and of unproven feasibility.