An Airbus A350 running on 100% sustainable aviation fuel shadowed by a Falcon business jet. Video / Airbus
Initial findings from a world-first study of the impact of 100 per cent sustainable aviation fuel (SAF) on both engines of a commercial jet have provided promising early results.
The study, involving Airbus, Rolls-Royce, German research centre DLR and SAF producer Neste, marks the first time 100 per cent green fuel has been measured simultaneously on both engines of a commercial passenger aircraft.
It was trialled on an Airbus A350 aircraft powered by Rolls-Royce Trent XWB engines.
The push to use SAF is speeding up as the airline industry faces emissions reduction targets. In this country Air NZ has partnered with Airbus on development of SAF power for large aircraft.
Earlier this year the A350 flew three flights over the Mediterranean Sea pursued by a DLR Falcon chaser plane to compare in-flight emissions of both kerosene and Neste's hydro-processed esters and fatty acids (HEFA) sustainable fuel. The team also carried out compliance tests using 100 SAF and no operational issues were experienced.
The fights in April were part of programme by an interdisciplinary team, which also includes researchers from the National Research Council of Canada and the University of Manchester. It is planned to publish its results in academic journals towards the end of next year and 2023.
Findings from the study will support efforts currently under way at Airbus and Rolls-Royce to ensure the aviation sector is ready for the large-scale use of SAF as part of the wider initiative to decarbonise the industry. Aircraft are currently only allowed to operate on a 50 per cent blend of SAF and conventional jet fuel, but both companies support the drive to certify 100 per cent SAF use.
A business jet fitted with sensors closely followed the Airbus A350. Photo / Supplied
In-flight emission tests using 100 per cent SAF and a HEFA/Jet A-1 fuel blend resumed this month, while ground-based emissions testing to quantify the benefits of SAF on local air quality were also performed. The research team found SAF releases fewer particulates than conventional kerosene at all tested engine operating conditions, which points to the potential for reduced climate impact and improvement in air quality around airports.
In addition, SAF has lower density but higher energy content per kilogram of fuel compared to conventional kerosene, which brings some aircraft fuel-efficiency advantages due to lower fuel burn and less fuel mass to board to achieve the same mission. Detailed analysis by the team is ongoing.
"Engines and fuel systems can be tested on the ground but the only way to gather the full set of emissions data necessary for this programme to be successful is to fly an aircraft in real conditions," said Steven Le Moing, new energy programme manager at Airbus.
"In-flight testing of the A350 offers the advantage of characterising direct and indirect engine emissions, including particulates from behind an aircraft at high altitude."
Simon Burr, Rolls-Royce director of product development and technology, Civil Aerospace, said the research adds to tests already carried out on engines, both on the ground and in the air, which have found no engineering obstacle to our engines running on 100 per cent SAF.
''If we are to truly decarbonise long-haul air travel, then 100 per cent SAF is a critical element and we are committed to supporting its certification for service."
The DLR Falcon chaser aircraft was equipped with multiple probes to measure emissions at cruise level down to a distance of only 100m from the A350 and feed them into scientific instrumentation for analysis.
"SAF has been shown to have a significantly lower carbon footprint over its life cycle compared to conventional jet fuel and now we are seeing it is advantageous in reducing non-CO2 effects too," said Markus Fischer, DLR's divisional board member for Aeronautics.
"Tests such as these are continuing to develop our understanding of 100 per cent SAF, its use in flight and we are seeing positive signs for its potential in climate mitigation. We look forward to studying the data from the second series of ECLIF3 flights, which restarted with a first chase flight above the Mediterranean earlier this month."
Neste refines waste, residues and ''innovative'' raw materials into renewable fuels and sustainable feedstock for plastics and other materials and is a world-leading producer of renewable diesel and sustainable aviation fuel.
