UK-first ‘chase plane’ SAF emissions experiment undertaken
May 21, 2025
In a first-of-its-kind experiment for the UK, a novel airborne experiment has been undertaken to help assess how SAF could reduce a variety of non-CO2 aircraft emissions (including soot, other volatile particles and gases such as nitrogen oxides).
A collaboration between university scientists, the National Centre for Atmospheric Science (NCAS) and Rolls Royce, project GRIM-SAF (GRound-Based and Inflight Measures) saw the former’s FAAM Airborne Laboratory (a modified BAE-146) ‘chased’ by the National Flying Laboratory Centre (NFLC)’s Saab 340B research aircraft. With the BAE-146 trailing the Saab during close formation sorties, emission samples were taken to sample pollutants produced by both SAF and conventional jet fuel for further analysis.
Unlike previous in-flight emissions work in the UK, which has involved one aircraft following several miles behind another, GRIM-SAF experiments saw the aircraft fly within 60m of each other. This close formation work is “very useful for scientists to get an understanding of the emissions produced by burning different types of fuels,” explained lead researcher Dr Paul Williams, who nevertheless added that the research “aims to understand the emissions on the ground, and to correlate these to emissions at altitude so future experiments don’t rely on chasing aircraft with other aircraft”.
With this goal in mind, both aircraft also landed at RAF Brize Norton to “make detailed ground-based assessments with the goal of linking this to the in-flight work,” said the NCAS. Dr Williams further explained that with non-CO2 emissions contributing up to 66% of aviation’s Effective Radiative Forcing (ERF) – versus 33% from CO2 – it is important to further understand their impact. “Additionally, it’s important to understand what effects they have on our local air quality around airports,” he concluded.
Alongside the two-aircraft experiments, the FAAM Airborne Laboratory is also set to sample its own SAF and non-SAF exhaust emissions over several flights by flying in a ‘donut’ pattern, with initial work in 2024 confirming the aircraft’s capability to “fly along and detect its own exhaust trails”.
