Lycoming expands list of engines approved to UL91 unleaded avgas

Lycoming Engines will release Service Instruction SI-1070S in the fall, which will add 20 engines to the list of models approved for use on UL 91 unleaded avgas and bringing the total number approved to 55. With the move, Lycoming officials continue to call for UL100 as a fleetwide solution to replacing 100LL.

The new Service released Service Instruction follows SI-1070R, which was released on April 16 that approved the first 35 engines for use with ASTM D7547 UL 91 unleaded avgas. In conjunction, the European Aviation Safety Administration (EASA) Safety Information Bulletin (SIB) 2011-01 provided aircraft-level approval on the basis of engine approval.

The latest models to be approved include the large installed base of (I)O- 320-B, D; LIO-320-B; O-540-A, D, E, F, G, H, J; and IO-540-C, D, N, T, V, W, AF, AB engine models. The EASA SIB will allow UL 91 use on European Union-based aircraft such as the Piper Warrior and Archer; Cessna 152, 172 Skyhawk and 182 Skylane; Robinson R22 and R44- Raven I; Diamond DA40 and DA42-L360; and many other models.

“Our continued efforts to expand our approvals of UL 91 support the increased deployment by European fuel producers that has occurred since our announcement earlier this year. We are responding to progressively wider availability of unleaded aviation-grade fuel supplies for light aircraft,” says Michael Kraft, Lycoming senior vice president and general manager. “It’s a significant and positive development that European unleaded avgas producers and EASA are making UL 91 available and easily usable to consumers. UL 91 provides a well-conditioned aviation suitable solution for engines originally designed for lower-octane leaded aviation and automotive fuels.”

UL 91 originally entered into distribution in Europe largely to serve engines approved to operate on automotive specification fuels. EASA Safety Information Bulletin 2011-01R1 and now R2 provided aircraft-level approval on the basis of engine approval.

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.

UL 91 is offered at 17 airfields in the UK, nine airfields in France and six in Switzerland. The fuel is also available at airfields in Germany and Belgium. Plans are currently in place to offer fuel at additional locations throughout Europe.

“Once again, we want to emphasize that UL 91 is not a replacement for 100LL, but it is a very robust aviation-suitable alternative to automotive gasoline that should result in overall lower operating costs for consumers,” Kraft says. “Lycoming remains vigorously supportive of a long-term unleaded 100LL replacement fuel, which could uniformly serve the entire installed base. Our expansion of UL 91 approvals continues to represent an excellent opportunity to prime the pump for a ‘UL 100’ future.”

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  1. Kent Misegades says

    Does anyone understand why Lycoming is doing this?   80% of all piston-engine planes in the U.S. are already approved for 91+ AKI mogas, which represents about half all the fuel burned in piston engine aircraft in Germany today.  Why bother?   As one German pilot put it – UL91 is little more than expensive ‘perfumed’ mogas.  He prefers the lower cost solution of mogas, which is probably why you will not find UL91 at many places in Germany.

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