Gulfstream Aerospace and Rolls-Royce have completed a series of high-altitude flight tests using 100% sustainable aviation fuel (SAF), examining its potential to reduce non-CO₂ emissions associated with contrail formation.
The campaign included the first flight of a Gulfstream G800 powered by Rolls-Royce Pearl 700 engines operating entirely on neat SAF. The flight formed part of Gulfstream’s high-altitude testing programme and assessed emissions at altitudes of up to 50,000 feet.
A modified Gulfstream G700, also equipped with Pearl 700 engines, accompanied the aircraft as a flying emissions laboratory. Flying in close formation, the aircraft enabled researchers to collect real-world measurements of particulate emissions and atmospheric conditions linked to contrail formation at altitudes commonly used by business aviation.
The research programme was led by Gulfstream Aerospace in collaboration with the U.S. Federal Aviation Administration (FAA), NASA, the German Aerospace Center (DLR), Missouri University of Science and Technology, Rolls-Royce, Aerodyne Research, Montana Renewables and World Fuel Services.
The tests compared emissions from three fuel types: conventional Jet-A fuel, low-sulphur Jet-A and neat hydroprocessed esters and fatty acids (HEFA) sustainable aviation fuel, which contains no sulphur or aromatic compounds.
According to preliminary findings, the use of neat SAF resulted in a measurable reduction in particulate emissions associated with contrail formation compared with conventional aviation fuels.
Alan Newby, Director of Research and Technology at Rolls-Royce, said:Sustainable Aviation Fuels in combination with compatible, ultra-efficient aero engines will not only play a vital role in decarbonising aviation but have also been shown to reduce certain non-CO2 emissions. The valuable insights we have gained from these latest tests at high altitudes, as well as the data from projects like QRITOS or ECLIF3, are driving real progress in understanding aviation’s non-CO2 climate impacts and potential mitigation options.
The results from the latest campaign will be shared with the aviation and atmospheric science communities to support the development of emissions models, inform future fuel standards and contribute to operational strategies aimed at reducing aviation’s environmental impact.
Rolls-Royce’s current Trent and business aviation engines are capable of operating on 100% sustainable aviation fuel, although existing fuel certification standards currently permit blends containing up to 50% SAF mixed with conventional jet fuel.
Sustainable aviation fuel has the potential to reduce lifecycle carbon dioxide emissions by around 80% compared with conventional jet fuel, depending on the feedstock and production pathway used.
