FAA Approves 600 Engines For GAMI Unleaded Fuel


The FAA has approved an additional 611 certified piston aircraft engines to run on GAMI’s G100UL high octane unleaded avgas in an FAA-approved model list that was posted on Thursday. With the announcement, about 70 percent of existing engines in service are now able to use the fuel, which received FAA approval itself in July. “This is a very bullish sign that the FAA is continuing to honor their commitment to move unleaded avgas forward as fast as possible,” AOPA fuel consultant Paul Millner said in a story published on the organization’s website. Another approved list in which those engines are mated to approved airframes will be coming soon.

The approved list covers most lower-powered engines by Lycoming, up to 360-cubic-inch displacement (CID), and Continental up to 470 CID plus many Franklins. The list also includes dozens of radial engines by Pratt & Whitney and Curtiss-Wright up to some of the largest models. Engines not on the list include the high-powered six-cylinder Continental and Lycoming mills that power most of the commercial piston fleet. Although they account for about 30 percent of in-service engines, they burn more than 80 percent of the avgas sold in the U.S. AOPA says GAMI CEO George Braly is expecting the big engines to be approved in 2022. GAMI is working with Avfuel to distribute the fuel and is concentrating in areas where 100LL sales are being phased out.

Russ Niles
Russ Niles is Editor-in-Chief of AVweb. He has been a pilot for 30 years and joined AVweb 22 years ago. He and his wife Marni live in southern British Columbia where they also operate a small winery.

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    • Those will already burn any swill, won’t they?
      At least the modern ones come approved for UL mogas.

      • UL/ULS, sure, as far as Rotax is concerned, though the ULS requires higher octane than UL. Certificated versions 912A, F, or S depend on the airframe type certificate. In the EASA to FAA conversion, most didn’t take chances with out ethanol-laced winter/summer variant car gas and specified 100LL on their FAA type certificates. So, AFIK, legally stuck unless an STC or blanket approval is granted.

  1. This is another big step toward addressing the real market, those engines (and airframes) that require 100 octane fuel for protection and performance. Any word on when STCs for airframes containing these engines will be issued, so these new engine STCs will be usable when G100LL is available?

  2. Note GAMI’s mention of developing better methods of measuring detonation.

    ‘Octane’ is rather variable, I learn from attempting to understand what fuels might be useable in aircraft that originally used something like 130 or 145 octane fuel (big roundies like the Wright Turbo-Compound).

    Beware that some people’s claim of compatibility of high power engines with certain octane levels _assumes_ operating at reduced power. That’s misleading.

    (Might help get an airplane home from somewhere.)

    Not a good idea for aircraft like the Martin Mars forest fire suppression seaplane IMO. In the old days when fighting fires in the interior of BC the Mars would fly home to Sproat Lake on Vancouver Island to refuel and get maintenance checks. (It has ample tank capacity though that is weight at the start of the fighting day.) For missions further out its own tank truck was needed.

      • The upgraded Mars flew to save an observatory in California, in September of 2020.

        Big problem is political/cronyism, phony claims by the almost monopoly customer in BC that it is not suitable. BC once again failed to use all available air and ground resources while settlements burned up.

        Whereas USFS had three 10Tankers on contract last summer, and various federal, state, and country wildfire agencies have other airplanes and heavy helos (some form Coulson, including a rapid reaction force in Orange and Ventura counties).

        The Mars is a big dump which quenches raging fires so reduces spread of fire by embers. Or can spread a fire line quickly by salvoing doors (dropping water, foamed water, or gelled water but not ‘retardant” the stuff usually coloured red). Only 10Tanker is a larger dump in North America, newer airliner based tankers and Coulson’s C-130s carry 4000 USG or less whereas the Mars carries 7200 USG. (The 747 is not active now.)

        You could buy a Mars.
        (Coulson had a deal to trade one with a navy museum in FL for parts for C-130s, arms trade and other gummint interference blocked that. Yes, the Mars is a military airplane and C-130 parts are arms, never mind both countries have civilian C-130s. AFAIK it sits in the background on the beach at Sproat Lake, painted original USN blue.)

  3. Dear GAMI:

    I’ve got a TON of love for you guys, but you’re skating on thin ice, my friend. Some of those engine models listed on that AML are installed in what, 15 aircraft maybe. Who ever is working on all the iterations of the Lycoming O-235s and missed the deadline to submit the engineering data to be included on this round of approvals, they don’t get paid until that engine is on that list. Want to eat? Get it done.

    Seriously, I feel like you were more concerned that the aircraft at Old Rhinebeck then you were with the thousands of O-235s scattered about. Who is in charge of racking and stacking the priority list over there!??!