Next Series of ASTM D7547 UL 91 Unleaded Avgas Approvals Announced by Lycoming

April 24, 2013
Service Instruction SI-1070S has been approved for release, adding 31 engines to the list of models approved for use on UL 91 unleaded avgas.

Williamsport, PA – April 23, 2013 – Lycoming Engines, a division of Avco Corporation, released Service Instruction SI-1070R in April of 2012, which approved a wide variety of engines for use with ASTM D7547 UL 91 unleaded avgas. European Aviation Safety Administration (EASA) Safety Information Bulletin (SIB) 2011-01 provided aircraft-level approval on the basis of engine approval.

Today Lycoming is pleased to announce that Service Instruction SI-1070S has been approved for release, adding 31 engines to the list of models approved for use on UL 91 unleaded avgas and bringing the total number approved to 63.

Engine models added through this approval include the large installed base of: O-235-K, L, M, N, P; O-320-B, D; IO-320-B, D; AEIO-320-A, B, C; LIO-320-B; HO-360-C; HIO-360-B, G; O-540-A, E, F, G, H, J; and IO-540-C, D, N, T, V, W, AB, AF engine models.

With the Lycoming engine model approvals, the EASA SIB immediately allows ASTM D 7547 Grade UL 91 use on European Union based aircraft such as the Cessna 152, Cessna 172 Skyhawk and Cessna 182 Skylane; Diamond DA40 and DA42-L360; Helicoptères Guimbal’s Cabri G2; Piper Warrior and Archer;Robin DR 200, DR400-120 Dauphin and DR400-160 Major; Robinson R22 and R44- Raven I; Socata TB9 Tampico and Socata TB20 Trinidad; and many other models.

“Lycoming has expanded our approvals of UL 91 for our engine models in response to the increasing availability in Europe of unleaded aviation-grade fuel supplies for light aircraft,” says Michael Kraft, Lycoming senior vice president and general manager. “This latest revision of SI-1070 represents the final set of currently existing engine models that can operate on UL 91without any alteration of the Engine Type Design operating limitations.”

“Altering Engine Type Design operating limitations means that aircraft performance would likely be affected. SI-1070S provides consumers and fuel producers alike a view as to which engines have an octane demand that is best satisfied by a UL 100 solution,” Kraft says. “This is why we remain vigorously supportive of a long-term unleaded 100LL replacement fuel and emphasize that UL 91 is not a replacement for 100LL, but a very robust unleaded aviation-suitable alternative to automotive gasoline.”

UL 91 originally entered into distribution in Europe largely to serve engines and aircraft approved to operate on automotive specification fuels. EASA Safety Information Bulletin 2011-01R1 and R2 provide 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.

According to TOTAL, UL 91 is offered at 18 airfields in the UK, and nine airfields in France. The fuel is also available at airfields in Belgium, Germany, the Netherlands and Switzerland. Plans are currently in place to offer fuel at additional locations throughout Europe.

About Lycoming

Lycoming Engines specializes in engineering, manufacture, service and support of piston aircraft engines. Based in Williamsport, Pennsylvania, Lycoming piston engines power more than half of the world's general aviation fleet - both rotary-wing and fixed-wing. Lycoming Engines is a division of Avco Corporation. More information is available at

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