Next series of UL 91 unleaded avgas approvals revealed by Lycoming

Lycoming Engines released Service Instruction SI-1070R in April 2012, which approved a wide variety of engines for use with ASTM D7547 UL 91 unleaded avgas. This week, the company reports 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, 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.

European Aviation Safety Administration (EASA) Safety Information Bulletin (SIB) 2011-01 provided aircraft-level approval on the basis of engine approval.

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 91 without 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 the fuel at additional locations throughout Europe.

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  1. KK says

    This is a great step in the right direction.

  2. says

    Pretty ironic that Lycoming is spending so much time and money on providing approval for a fuel spec that will only be peculiar to Europe. ASTM D7547 is a DOD spec for drone fuel and not likely to ever be produced in the U.S. However there is an unleaded avgas spec that is likely to be produced if TEL disappears. That is ASTM D7592 for 94 UL. Wonder when Lycoming will invest in the U.S.?

  3. Dick Russell says

    Seems to me we ought to be considering what we do Now for current GA airplanes. Nice to consider our future, but I believe we also need to focus on the present.

  4. Jscott says

    If Lycoming and Continental had any marketing sense, they would continue a push towards converting their product lines to run on Mogas. UL 91, like 100LL, is a low volume, high priced boutique fuel. Unless the manufacturers are going to be willing to design and build for a readily available mass produced affordable fuel, private aviation will continue it’s downhill slide into the history of a once great nation. In the mean time, EAA and AOPA are full speed ahead with the manufacturers search for a drop in replacement, costs to the users be damned. None seem to seem to understand that the end users that have to pay for their products may very well not be able to afford them.

  5. Kent Misegades says

    Given that UL91 was announced in Europe about two years ago but is available only at a handful of airports there, this appears to be a major belly-flop for the fuel. My German pilot friends laugh about it, calling UL91 ‘expensive perfumed Mogas’ which explains why mogas is the fuel #1 for recreational pilots there. It is great though to see Lycoming’s implicit endorsement of Mogas after criticizing it for two decades or more.

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