For owners and operators of private and corporate aircraft, the use of Sustainable Aviation Fuel or “SAF” to power jet engines is becoming more accepted, although challenges still loom with regard to its adoption. However, industry experts are working to promote the product and to stamp out some of the fallacies regarding its use.
Charles Etter, a scientist with Gulfstream Aerospace, recently told NBAA that SAF has to satisfy all of the requirements imposed under ASTM D1655, the industry standard that establishes the criteria for Jet A and Jet A-1 aviation fuel, and it has to be tested both before and after it is blended with conventional fuel. “There are no negative performance impacts with SAF, no changes in maintenance or fueling practices,” Etter emphasized. “It’s not like Jet A — it is Jet A.” According to Etter, Gulfstream has been using SAF in its aircraft since 2011, bought more than 1.8 million gallons, conducted hundreds of flights, and all without a single problem.
Frank Moesta, a senior vice president with Rolls-Royce, told NBAA that Rolls engines are currently certified to run on a blend of 50% SAF and 50% kerosene and have run hundreds of thousands of operations, on the ground and in the air, without incident. Moesta said Rolls-Royce already has conducted flight tests using 100% SAF and the engines are actually more efficient and produce fewer emissions. He characterized the current 50/50 percentage limitation as an issue of availability rather than capability.
Nate Dietsch, an aircraft maintenance manager with Netflix, seconded Moesta’s assessment. Dietsch said Netflix has discovered that, because of the lower sulphur content and aromatics, engines operating on an SAF blend actually burn cleaner and emit fewer particulate emissions. He also said the use of SAF has not caused any additional maintenance work for Netflix.
Regarding the concern over microbial growth in fuel, Etter said there is no evidence that SAF contributes to that process. The Gulfstream scientist said the refining system is adapted on the front end to process the different type of feed stock and that after initial adjustments, the refining procedure is no different than it is with traditional petroleum. Once refining is finished, “the fuel molecules are pure hydrocarbons so there’s no extra material” being introduced into the SAF. Etter said he thinks concerns about SAF and microbial growth may stem from problems people have experienced or heard about involving biodiesel or ethanol in other, non-aviation contexts, but he said the characteristics of SAF are completely different. He also expressed the view that any increase in microbial growth operators experience could be the result of handling and storage issues and introduction of water and other particulates into the fuel tank rather than SAF.
For now, it appears any problems relating to SAF are caused by lack of availability and price, not performance. As more customers demand SAF and, in particular, if the federal government takes action to support its production, more private jet owners and operators will be able to adopt this cleaner alternative for greener skies.
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