NATA’s Hard Line Complicates Fuel Quest


The National Air Transportation Association (NATA) has laid all its cards on the table. We now know why it thinks General Aviation Modifications Inc.’s G100UL unleaded fuel is clearly considered an outlier in the quest for a new drop-in replacement for 100LL even though it has been approved by the FAA via a universal STC for gas engines in certified airplanes (the helicopter process is underway).

According to a statement from NATA, the STC, which in FAA circles is an immensely powerful document, is nothing more than “a positive step” toward an unleaded replacement fuel because GAMI has chosen not to submit the fuel to ASTM International for testing and the granting of a “fuel specification.”

In a nutshell, NATA says ASTM tests more stuff that is relevant to its members like compatibility with hoses, tanks, meters, etc. It also says that without that ASTM fuel specification, its members don’t want to touch it because they’re afraid insurance won’t cover any issues that crop up.

Obviously that logjam could be broken if GAMI submitted G100UL to ASTM, but company founder George Braly doesn’t trust the ASTM process and has thus far resisted getting involved with them. I don’t know if there’s any negotiating room there, but I also don’t know if anyone in a more relevant position has asked.

The hell of this impasse is that we could end up with a fuel that ticks all the boxes for trucks, pipes and pumps on the ground but may not work without some form of operating or physical modification in some aircraft engines up in the air.

During an update on the quest for an unleaded fuel by the End Aviation Gasoline Lead Emissions (EAGLE) committee last week, it was mentioned several times that the last fuel standing in the Piston Aviation Fuel Initiative (PAFI) program, the process that would lead to a “fleet authorization,” may not be completely compatible with a small minority of engines.

The fuel, made by Lyondell/Basell and VP Racing, is now undergoing extensive testing by the FAA, and it seems like EAGLE already knows it’s going to cause issues in some of the 143 engine makes on the FAA registry that are not Continental, Lycoming or Rotax. The nature of those possible shortcomings or how widespread they are was not discussed, but even if 99% of engines hum happily on that fuel, try telling the folks in that remaining 1% that it’s acceptable collateral damage that they can’t just pump the fuel and go flying.

And there’s the question of just how much power an ASTM specification wields in this process. The FAA is used to being in charge of these sorts of things, and is it really going to surrender that regulatory omnipotence to make sure insurance companies are happy?

There’s also the sticky issue of optics and potential or perceived conflicts. NATA is unequivocal in its assessment of G100UL. It’s going nowhere without ASTM. NATA is a member of EAGLE and must therefore present that position to the EAGLE membership, and NATA President Curt Castagna is co-chair of EAGLE.

Under parliamentary procedure, the chair(s) are neutral and only vote to break ties. I’ve never seen a vote at an EAGLE meeting so maybe it’s not bound by those rules, but NATA’s clear position on the ASTM thing puts Castagna in an uncomfortable spot at best.

We all want the same thing. We want a fuel that performs at least as well as 100LL and it seems like all those elements are satisfied among the three remaining contenders in the process. Given that, it seems unfortunate that hard positions that exclude any of the players are being taken.

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.


  1. Considering how long ago 100LL was approved, I wonder if it would pass the current ASTM testing requirements, especially considering the contamination it causes in current engines.

  2. “NATA is unequivocal in its assessment of G100UL. It’s going nowhere without ASTM. NATA is a member of EAGLE and must therefore present that position to the EAGLE membership, and NATA President Curt Castagna is co-chair of EAGLE.”

    This all makes it sound like NATA is opposed to G100UL because of a conflict of interest, and I suspect even if G100UL is submitted to and receives an ASTM spec, NATA would just find another reason to pretend it’s not a viable alternative. It wouldn’t surprise me if the argument then becomes something like “It’s not part of the EAGLE process, so it’s not a viable alternative”.

  3. The UL story parallel’s Mad Magazine’s “Spy vs Spy” where the parties involve are more dedicated to neutralizing the other guy than solving the problem. For EAGLE, with its big players, to be outdone by upstart GAMI is unacceptable by them. While egos, both corporate and individual, can’t help but being in play, profit potential is the key player in this mess. If the present squabbling continues, we’ll be buying fuel from China along with everything else.

  4. ATSM, is a VOLUNTARY industry consensus standard, or so it is called under the Federal Acquisition Regulations. Under those same FARs, the government cannot mandate use of a particular industry standard. (Congress could do so in specific legislation, but that is very rare.) It sounds like NATA is trying to force the FAA to mandate something it cannot do.

  5. Actually, if it worked with 99% of the recips flying, that’s good enough. More than good enough, in fact.

    • I doubt the people flying aircraft with those 1% of engines feel the same, especially since there is a fuel that apparently IS compatible with those engines.

      • Outside of Continental, Lyc, & Rotax, the percentage is likely closer to 99.9%. I’d be curious to know that answer. The next question is, of those other engines, how many actually REQUIRE 100 octane (vs. auto gas octane levels)? I suspect that would take the number down further yet. Yes, it would cause those remaining operators significant challenges, but since many of those engines are experimental anyway, it may be easier for those manufacturers to find a work-around.

        • You seem to have forgotten all those Warbirds out there that are not part of the group of engine manufacturers you mentioned. Pratt & Whitney, Allison, Warner, Franklin, Ranger and a few others. Most of them REQUIRE 100 LL. Don’t be so close minded. We all fly airplanes of different types. The new fuel MUST work for ALL of us.

  6. I have to wonder if the powers to be are uncomfortable with an outsider like Mr. Braly selling fuel. GAMI more or less became what it is by doing the obvious to correct a condition the engine manufacturers should have done in the first place. That being matching injector nozzle size to cylinder airflow. As I recall, once GAMI started making a few dollars, the engine manufacturers started doing the same. Braly’s contention of operating an engine “lean of perk” combustion temperatures never really was accepted by all that I can recall.

    In the end, his GAMI product does not make him a qualified fuel engineer. His reluctance to seek the ASTM certification is somewhat of a mystery. Maybe he knows something? In any case, I would be reluctant to use fuel provided by any company outside of the established fuel industry. As for the FAA? Their STC process really only requires the product or modification to show it does no harm.

    In a situation where the entire GA piston fleet is involved, once a workable solution is proven, it should simply become a standard available to all fuel suppliers. An STC is not a patent. It is only an approval. In the end, I doubt if Mr. Braly could compete with the industry nationwide in either quantities or distribution.

    • “Braly’s contention of operating an engine “lean of perk” combustion temperatures never really was accepted by all that I can recall.”

      I assume that’s a typo and was meant to read “lean of peak”. But who are you referring to who “never really” accepted it? When airliners were still using piston engines, they regularly operated them lean of peak.

      “In the end, I doubt if Mr. Braly could compete with the industry nationwide in either quantities or distribution.”

      GAMI isn’t a fuel distributor. They’re simply licensing others to make and distribute their fuel.

      • Comparing a commercial operation to a GA is truely comparing apples to oranges. It’s been twenty years since I ran a GA shop but at that time neither Continental or Lycoming recommended running an engine lean of peak. And most engine overhaul shops strongly advised against it.

        My point was that the ability to do so is what drove a lot of owners to purchase his product. Which were simply different sized injectors matched to each cylinder. Soon after the GAMI injectors became popular, Continental did the same with all of their engines. But Mr. Braly and many shops continued to sell them to those owners anyway.

        Mr. Braly is attempting to skim a little off every gallon burned. Do we really need yet another hidden cost? If an STC is an acceptable solution, then it should be as easy as the Autogas STC which the EAA provided years ago to obtain. Paying for an STC once is one thing, paying for it with every gallon burned is another.

        Yes, I agree. The powers to be are trying to freeze Mr Braley out. But there may be good reasons to do so. And in this business, liability is a very large issue. But allowing one person to sit back and watch the cash register ring with every gallon pumped may also be a good reason.

        • Are you still hanging on to the idea that GAMI was not correct about LoP operation (which was approved on my 550 with settings in the POH and everything) or about shock cooling?
          That doesn’t help your argument here.

    • It’s been pointed out here several times that the existing suppliers, as well as competitors for new fuels, are big players in ASTM. They sit on committees, provide funding, all that sort of thing. 100UL, if successful, will likely end all of their Avgas business within a few years.
      I don’t think one needs to be paranoid, and GAMI has all sorts of reason to think there are people out to get them, to think your formula might not get a fair hearing or may not be kept completely secret.

  7. Send me the GAMI fuel; I will be very happy to use it!
    GAMI knows more about fuel, engines, and combustion than anyone in NATA, or possibly even the FAA.
    NATA needs to show what they know about fuel that no-one else knows, or be told to get out of the way of moving forward.
    Seems like NATA personnel likely have no clue about fuel, only fear of change.
    (And; the lawyers are undoubtedly circling)

    • NATA’s whole argument has zero to do with science, and they do not claim it does. It’s about liability and semantics.

  8. GAMI’s STC is an alteration to a type design.
    The FAA approves TCs, STCs, PMAs, TSOs, and various subcategories to these for airborne products. They do not approve or authorize the use of any fuel unless it is attached to a TC or STC process.
    ASTM (or any consensus organization) does not approve any products or materials. They generate consensus data to be used in the approval process by others in the business of testing. Take your pick.
    Engine manufacturers approve the use of fuels for their products. They do not approve the characteristics of that fuel, just the use of that fuel they deem acceptable for their engines.
    ALL stakeholders have an interest in the combined experience and expertise found in consensus standards-including the aforementioned. It is not about trust, it’s about predictability.

  9. Liability! That is the elephant in the room. Until the liability issue is resolved, no matter which direction the unleaded fuel research goes, nothing will change. Tom Helm’s comment is correct in wondering if when 100LL was originally created, would it then or now meet this ASTM standard. Would it have been possible to bring out 100LL in the current sue happy legal environment?

  10. I’ve followed GAMI’s story from the beginning. At Airventure 2023, I attended the GAMI forum and listened to George (after he got there because he was getting the final full STC approval from FAA) talk about ASTM. He said he’d had ‘enough’ of the process and wasn’t going to deal with ASTM. Just two weeks ago, I attended a large EAA chapter meeting where GAMI Pres. Tim Roehl gave a briefing on the subject. From what I heard, GAMI has tested, retested and tested again their G100UL to the point where they are happy with it. They have their full STC and if ya want to use it … fine. If not, fine, too. In effect, take it or leave it. We’re all talking about lawyers suing over use of their fuel … on what basis? It’s approved? I can’t remember when I last pulled a spark plug on any of my vehicles … what are we all waiting for with our airplanes? Personally, I do NOT believe the minute amount of lead coming from our engines is harming anyone but DO feel that it’ll make maintenance chores easier.
    This is turning out to be a political and insider event — “Not Invented Here” (as someone said) — and little more. The boys that are ‘here ta help’ need to get off their keisters and DO something. STOP talking about it.

    At the EAA meeting, Tim talked about why the 94UL fuel didn’t work out for UND. GAMI bought some of the stuff and tested it. It was their position that 94UL may have been marginally incapable of preventing detonation under some leaning procedures. They’d flow 46,000 hours so lots of different pilots had a hand in the issue. He described some machine they built to measure compression pressures. Apparently, under partial (weak) detonation, the valves were being slammed into their seats resulting in the recession issue. It sounded like GAMI wanted to know what the tentative issue was and THEY had the only machine capable of this testing. All I know from all of what I’ve heard is … I’ll put GAMI G100UL in MY 100LL engine as soon as I can buy it. Sadly, he says it’ll be ~$1 more.

    • You can’t compare your modern car to a 1930 technology aircraft engine. Your car has numerous computers measuring dozens of engine conditions hundreds of times per second. Those computers adjust the combustion process almost instantly and that’s what leads to long component life and clean burning. Your aircraft engine has none of that.

      The last new engine I installed in an A36 cost over $25,000 bucks. And that was twenty years ago. If I was an owner today, I wouldn’t be so cavalier about what I put into the tank. And I certainly wouldn’t want an added dollar per gallon added to the cost of my flying if it can be avoided. But it was nice of him to slip that bit of information into the message.

  11. I have worked with ASTM specification for over 42 years. The ASTm spec D7547 which covers UL94 et al. should be the model for UL 100 with the only addition being the octane requiremnt for that grade. NOW this is the wat the current leaded ASTM spec reads. SO lets assume that is the case. There is NO requirement for these fuels to be compatible with anything or meet any requirement other than specified in the ASTM spec. period.

    Next. IF the fuel meets the specification as written as cetrtificated by the manufacturere which is how every other spec works in the astm. then the fuel meets that respec. The ASTM is a spec writing body NOT a verification body. if they were then there would be language of required submittal etc.

    GAMI is playing by the normal rules of aerospace work. iF they state their fuel meets the ASTM spec it does it is their responsibility and risk as is the manufacturer who makes the fuel to their formulation. IF there is a need to have the materials in the supply chain meet swell criteria then it is taht manufacture who has to test thier materials to the spec materials. but again the spec is what it is. Any testing out side that specification which is needed o be in a fail fail criteria then it must be a requirement and in the spec. IF Gami is stating they do not meet the ASTM spec and do not publish thier minimum requiremnts then they are not sellin a standardized product. IF the GAMI product meets some of the ASTM spec and not others they can and should stae wht it will meet PUBLISH that and work for that being the requiremnts. The ony reason that will not be acceptable to the ASTM is if this chage affects the fit form or function of the product to the point the end use is compromised.

  12. Russ- Do you know what is in GAMI’s Fuel? do you know how many different actual airplanes and engines it has been tested in? Do you know how many forms of rubber, sealant and plastic it has been tested with? With a proprietary formula untested by 3rd parties, nobody else does either. And IF there is an incident or problem, GAMI’s pockets are not exactly “deep”… There is a reason the refiners and retailers are staying on the sidelines. After what the Trial Lawyers have done to the GA manufacturers, imagine what they can do to the fuel supply chain… Count me among those who say to the impatient:”If you want to pay $9/gallon for barrels of a secret formula gasoline because the FAA region office says GAMI met the requirements for a supplemental type certificate, be my guest…” I’ll wait for Chevron and Phillips to start brewing a vetted unleaded 100 octane fuel that is tested in every possible dimension and is patented with published specs.

  13. There are 1 million gallons of G100UL available to anyone who wants to buy some or all of it today, it will be at least another two years before the EAGLE fuel(s) are available. The NATA’s reliance on an ASTM spec is meaningless for type certificated (TC) aircraft. I see no ASTM listing in my POH for approved fuel, only 100LL (blue) and 100/130 (green) are authorized. At least GMAI’s STC is a LEGAL means to use an alternative fuel not approved under the TC. I am not aware of how the FAA intends to alter the TCs of all piston-powered aircraft to provide legal cover for the EAGLE fuel(s). I am sure NATAs real objective is a version of the General Aviation Revitalization Act of 1994 that limits it’s members liability (they were not included in the 1994 Act), and the EAGLE initiative is the opening they need to get it implemented.

  14. NATA President Curt Castagna also EAGLE chair putting a halt on GAMI sounds like a conflict of interest it doesn’t smell right! What’s the real reason I suspect $$$.