GAMI's G100 Avgas Replacement Nears End Of Testing

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As the FAA’s leaded avgas replacement effort grinds to a temporary halt, General Aviation Modifications Inc. says it’s close to completing testing on its own 100-octane unleaded fuel. GAMI sidestepped the FAA’s Piston Aviation Fuel Initiative in favor of a more streamlined STC approval process that’s now within a few steps of being completed.

GAMI’s George Braly told AVweb this week that the company’s G100 fuel has been getting more attention from both the FAA and general aviation interests even before last week’s announcement that PAFI testing of two candidate fuels from Swift and Shell has been halted because of specification shortfalls. The agency declined to offer details, but said it would be inviting companies with candidate fuels outside the PAFI process to participate. Braly said GAMI will continue to focus its efforts on the STC approvals.

G100 is an aviation alkylate base stock with an octane enhancement package consisting of a blend of aromatic hydrocarbons. It has been under almost continuous testing and evaluation since 2010. Braly said the company is continuing testing “out of a hip pocket” and may be done with the FAA-mandated work by the end of the year or early next year. Braly said GAMI still has some detonation testing and inflight trials using a Lycoming IO-540K-eqipped Lance and a 150-hour test in a Cirrus.

The company has been approached by refiners interested in producing G100 under license and although an STC is required to use it, Braly said GAMI hopes to offer this for free as a simple download. The STCs will eventually cover the entire fixed-wing piston fleet and could eventually be expanded to cover helicopters and warbirds.

G100 is slightly heavier than 100LL, but not enough to make significant performance differences, Braly said. It weighs 6.25 pounds per gallon compared to 6 pounds for 100LL. At the refinery gate, Braly estimates that G100 will cost 40 to 80 cents more than leaded avgas, but not less. Retail price at the pump will vary according to local flowage margins.

Comments (13)

What a company this is.

I flew behind their balanced fuel injectors for years and, armed with the meticulous data that George and others made available, was able to comfortably and confidently run LOP for over a decade. What a statement it makes that, in the face of the irrefutably weird PAFI selection process, GAMI has been able to quietly make such progress.

It's an elegant, understated gesture that flies in the face of PAFI, "...yeah, go ahead with your project and we will quietly and securely SOLVE this problem." Hat's off to Mr. Braly and GAMI.

Posted by: ANTHONY NASR | June 12, 2018 6:25 PM    Report this comment

This is actually not great news to me. It is hard to get excited about a replacement that most likely will be $1 more a gallon than what we are currently paying. This is especially an issue in the Northeast region.

Posted by: STEPHEN SARACINO | June 12, 2018 7:23 PM    Report this comment

I've been following this "story" since an article on 100LL-replacement was published in a 2006 edition of Aviation Consumer. I am somewhat stunned we got this far into PAFI, the FAA put the brakes on it, and is now requesting new candidates. What could possibly show up 1 year into flight testing--bad enough to halt the program--that couldn't have been flushed out in a lab!?

Best of luck to GAMI. I sincerely hope you are successful. The spark-ignited piston fleet is 100% in your hands--and your debt--if the EPA is ever run by a man-made-global-warming disciple again.

Posted by: Jim Perkins | June 12, 2018 8:44 PM    Report this comment

I am glad GAMI is putting all the time and effort in this endeavor. However, with an option that costs MORE then what we already pay I'm not at all interested. Sorry but I'll stick with the lead. The GA world is trying to desperately save itself by finding options to allow GA to fly less expensively. Adding MORE cost to flying does not help us. It only hurts us.

We want an STC so we can burn high octane motor vehicle fuel. Just allow us to burn MOGAS and most of our problems will be solved and because GA will cost less we will get more flyers again.

Posted by: Steve LaCrosse | June 12, 2018 9:08 PM    Report this comment

I run behind a Rotax which is designed for lead-free fuel. Even at an extra $1/gallon it's probably cheaper for me to use G100L than to use 100LL and do more oil changes plus live with a shorter TBO (to say nothing of lower reliability).

I learned to fly in a C150 in the 1980s, and a standard pre-takeoff ritual was burning the lead off the spark plugs in the runup area, because the Cessna's O-200 engine preferred lead-free fuel. The airplane would have been more reliable, and cheaper to operate, if there had been no lead in the fuel.

That C150 was manufactured in the 1970s. We have been dancing around the issue of eliminating lead for forty years - in other words, for the entire flying lifetime of almost everyone in aviation. There's been plenty of heads-up. It's time.

P.S. Mogas STCs are useless, in practice, because there's no mogas sold at airports, and even if you truck auto gasoline to the field yourself - and who wants to truck 50 gallons of gasoline? - it's adulterated with ethanol. My airplane is certificated for ethanol-free auto fuel, which in practice I can't buy, at airports or really at all.

P.P.S. 6.25 lb/gallon - really? What kind of hydrocarbon is being added? How much of it?

Posted by: Thomas Boyle | June 13, 2018 7:30 AM    Report this comment

"Just allow us to burn MOGAS and most of our problems will be solved and because GA will cost less we will get more flyers again."

Except good luck finding mogas without ethanol in it.


On the face of it, "40 to 80 cents more" is a non-starter. However, for the engines that don't need the 100 octane but still have to deal with lead deposits, the extra maintenance that will no longer be necessary will reduce the effective price of the fuel. And if G100 were to become *the* replacement for 100LL, maybe that price will come down with volume?

Posted by: Gary Baluha | June 13, 2018 8:10 AM    Report this comment

If memory serves, I believe that the 40 to 80 cents of additional cost per gallon is in line with previous estimates that I've seen for the PAFI candidate fuels. As previously stated in the comments, lower operating costs may be realized through the resulting lower maintenance costs due to usage of non-leaded fuel. Would the resulting lower maintenance costs equate to a net savings in total operating costs? That is another question that perhaps someone else could knowledgeably address.

Posted by: John Nevils | June 13, 2018 9:46 AM    Report this comment

Apologies to the optimists in the crowd but given the intersecting constraints of chemistry and engine performance requirements, eliminating lead from the fuel pool was never going to be less costly. To my knowledge not a single participant in this process has said it would be cheaper. Some of the costs of production could be offset by less difficult transport. Regardless, a stable secure supply of unleaded avgas that meets the needs of the entire fleet (without costly engine modifications) is far preferable to a basket of several solutions for subsets of the fleet under which segregation and transport costs would be higher.

The value of a solution to the longevity of GA is hard to understate.

Posted by: Geoff Reid | June 13, 2018 11:26 AM    Report this comment

The STC route is smart albeit constrained. But of the available possibilities for using a new fuel it's probably the least of all evils given the current regulatory framework. One can only hope one is covered and the fuel is widely distributed.

40 to 80 cents more is mouse nuts compared to everything else.

The real problem is a regulatory one more than an engineering one. The FAA have painted themselves into a regulatory corner with the whole type certification structure. When the current certification process was established, nobody ever thought of the possibiilty that aviation gasoline as defined for existing type certificates might one day go away. The rules were designed to prevent change and be intentionally inflexible to avoid the possibility someone might do something that was not thoroughly tested (hence permitted) and therefore cause an unsafe condition.

As the rules are written all aircraft are obligated to use the fuel which appears on their TCDS. If it says aviation gasoline then it includes TEL. To change this boadly without using the STC process would require a change in the definition of aviation gasoline, which would require the FAA to make a change to FAR. This would make them responsible for what happened, and that is anathama. Heretofore, the certification process put the liabiilty for everything on the manufacturers of aircraft and fuel. That's not something the FAA wants to take on.

The regulatory framework is the entire reason technology has lept far ahead of aviation, and within aviation the experimental world is far ahead of the certificated world. From a regulator standpoint, the question is "How do you keep every hayseeing knumbknut from turning their aircraft into an unairworthy piece of grabastic junk while still allowing aircraft operators to upgrade critical components like engines and avionics from technology that predates the lawnmower."

While I am no big fan of what I believe is somewhat excessive and limiting regulation I will also concede there are more than enough idiots out there quite willing to do something stupid with an aircraft that realistically might get you and me killed.

Posted by: FILL CEE | June 13, 2018 12:09 PM    Report this comment

Anathema broadly, and leapt are misspelled and a few worlds ended up with double i's where they ought not to be. Where was my copyeditor?

Posted by: FILL CEE | June 13, 2018 12:14 PM    Report this comment

The aromatic hydrocarbons Mr. Braly is using to improve detonation margins are products of the refinery reformer unit. These specific aromatic compounds would likely need to be separated from the unit's bulk reformate stream. The cost depends on whether separation is required and how complex the separation step is. Addition of aromatics to the avgas base stock would possibly alter its vapor pressure and require subsequent adjustment of the alkylate component. This is a lot of chemical engineering for a product with a limited, and shrinking, market. A one dollar premium could be reasonable.

If environmental concerns are behind the removal of lead from avgas, then some thought should be given to potential liabilities of the aromatics that will replace it. A number of aromatic compounds have been shown to be carcinogenic over the years (benzene removal now represents a substantial cost in reformate production). There is no way to predict whether this will become a problem, but the probability is not zero. I'd very much like to know why a savvy refiner like Shell did not go down this path.

Posted by: kim hunter | June 13, 2018 1:19 PM    Report this comment

I commend GAMI / Mr. Braly for their work and hope it is successful. The only hiccup with the STC route is that will it be per engine (IO-550-C, IO-540-KG1D), per airframe (BE35, PA32), or some combo (PA32 w/ IO-540-KG1D).

I really hope it's just done on an engine basis, but I don't know if that's plausible from the previously issued certification perspective.

Regardless of all that, I would like to commend the teams (not just GAMI) trying to come up with a single piston fuel.

Posted by: Joe Servov | June 13, 2018 3:28 PM    Report this comment

"Except good luck finding mogas without ethanol in it"

If your MoGas has ethenol in it, is it really MoGas?

Posted by: Robert Ore | June 14, 2018 4:07 PM    Report this comment

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