Lycoming gets FAA nod to update list of approved fuels

Just weeks after Lycoming Engines announced it would seek approval to operate certain engines on ASTM D7547 UL 91 unleaded avgas, it has received FAA approval to update its listing of approved fuels.

Lycoming’s newly available Service Instruction SI-1070R lists 35 engine models approved to operate on ASTM D7547 UL 91 fuel. The models are members of the 235, 290, 320, 340, 360, 435, 480 and 540 engine families. SI-1070R also specifies the lubricants to be used in conjunction with UL 91. SI-1070R is available at

“Our approval of UL 91 supports recent actions by European fuel producers and EASA that have resulted in progressively wider availability of unleaded aviation grade fuel supplies for light aircraft,” says Michael Kraft, Lycoming senior vice president and general manager. “We are continuously working to expand our specified fuels list. Distribution of UL 91 has provided a well-conditioned aviation suitable solution for engines originally designed for lower octane leaded aviation and automotive fuels.”

In conjunction with Lycoming’s approval to operate certain engines on UL 91, Lycoming is entering into a collaborative program with the FAA, Shell Aviation and TOTAL to examine the long-term effects of UL 91 on “purpose built” aviation engines and lubricants. This program will provide supporting information for more extensive unleaded avgas solutions. Shell Aviation produces AeroShell lubricants and TOTAL is a manufacturer of ASTM D7547 UL 91 avgas.

UL 91 originally entered into distribution in Europe largely to serve engines approved to operate on automotive specification fuels. European Aviation Safety Administration (EASA) Safety Information Bulletin 2011-01R1 provides aircraft level approval on the basis of engine approval.

Together with EASA Safety Information Bulletin, SI-1070R immediately enables the use of UL 91 on certain Lycoming-powered aircraft produced by manufacturers, such as Cessna, Diamond, Piper, American Champion, Aviat, Maule, Tecnam, CubCrafters, Zenair, and more; certain Lycoming-powered helicopters produced by manufacturers such as Robinson, Helicopteres Guimbal and more; experimental aircraft kits manufactured by Van’s, Glasair, Lancair, Zenith, Safari, Inpaer, and others.

In the United States, UL 91 will require an additional approval by the airframe manufacturer to operate aircraft using that fuel. There are no known distributors of UL 91 in the United States at this time, Lycoming officials note.

According to TOTAL, 18 U.K. airfields currently offer UL 91 and another three are making arrangements to offer the fuel. In France, the fuel is available at 10 airfields with four more preparing to offer it. Switzerland has four airfields with the fuel and plans are also in place to offer the fuel at airfields in Germany and Belgium.

“UL 91 is not a replacement for 100LL, but it is a very robust aviation-suitable alternative to automotive gasoline at lower prices than 100LL,” Kraft says. “Lycoming remains vigorously supportive of a long-term unleaded 100LL replacement fuel which could uniformly serve the entire installed base. Distribution of UL 91 and our collaboration program represents an excellent opportunity to prime the pump for a ‘UL 100’ future.”




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  1. Dean Billing says

    “There are no known distributors of UL 91 in the United States at this time, Lycoming officials note.”
    Why should there be?  ASTM D7547 was a specification rushed through ASTM by the Dept. of Defense for the Rotax 914 as used in the Predator drone when they couldn’t get a modification for ASTM D910 without TEL and the ASTM spec for 94UL, which is also D910 without TEL, was plodding along through ASTM because everyone knew it would never be made until TEL disappears.  The real question is why isn’t Lycoming asking FAA for approval of all of those engines on the 94UL spec  too?  And why isn’t the FAA looking at approving airframes that were approved for 91/96 avgas for 94UL.  Then someone might actually order it and a refiner might actually make it.  As it stands now, the only unleaded aviation gasoline you can get in the U.S. is made to ASTM D4814, auto gas, but all of that is getting blended with ethanol, so it won’t be around for aviation use much longer.  At least Europe is serious about getting the lead out of aviation gasoline, and probably understands that TEL is going away soon.

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