A350 SAF boost for decarbonised long-haul air travel

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Efforts to decarbonise long-haul air travel have been boosted by a study of the impact of 100 per cent sustainable aviation fuel (SAF) on both engines of a commercial jet.

The Emission and Climate Impact of Alternative Fuels (ECLIF3) study, an effort involving Airbus, Rolls-Royce, German research centre DLR and Finnish SAF producer Neste, marks the first time 100 per cent SAF has been measured simultaneously on both engines of a commercial passenger aircraft – an Airbus A350 aircraft powered by Rolls-Royce Trent XWB engines.

According to Airbus, in-flight emissions tests and associated ground testing on the ECLIF3 programme began earlier this year and have recently resumed. The interdisciplinary team, including researchers from the National Research Council of Canada and Manchester University, will publish its results in academic journals towards the end of next year and 2023.

Airbus and Rolls-Royce support the drive to certify 100 per cent SAF use, which is currently restricted to aircraft operating on a 50 per cent blend of SAF and conventional jet fuel. Findings from the study will support efforts at both companies to ensure a transition to large-scale use of SAF as part of wider decarbonisation initiatives within the industry.

Rolls-Royce flies engine on 100 per cent SAF

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Airbus confirmed that in April the A350 flew three flights over the Mediterranean Sea followed by a DLR Falcon chaser plane to compare in-flight emissions of kerosene and Neste’s hydro-processed esters and fatty acids (HEFA) sustainable fuel. The team also carried out compliance tests using 100 per cent SAF and reported no operational issues.

In-flight emission tests using 100 per cent SAF and a HEFA/Jet A-1 fuel blend resumed in November, along with ground-based emissions testing to quantify the benefits of SAF on local air quality. Airbus said the research team found SAF releases fewer particulates than conventional kerosene at all tested engine operating conditions.

In addition, SAF is said to have 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.

decarbonised long-haul air travel
ECLIF3 Falcon chaser in pursuit of an A350 using SAF

Simon Burr, Rolls-Royce director of product development and technology, civil aerospace,  said: “This research adds to tests we’ve already carried out on our 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 is equipped with multiple probes to measure emissions at cruise level down to a distance of 100m from the A350.

“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."