FAA Looking Into Possible G100UL Fuel Issues

News Discussion
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The FAA is now reportedly investigating reports of damage to aircraft related to their use of GAMI's G100UL unleaded fuel in California. Inspectors looked at several planes involved at Watsonville Airport south of San Francisco. Various incidents of peeling paint, leaking fuel tanks and even a bent pushrod/siezed valve have been reported in various forums.

This is a companion discussion topic for the original entry at https://www.avweb.com/aviation-news/faa-looking-into-possible-g100ul-fuel-issues
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What a F—- up… this is par for the course. Yeah, we’ll get the lead out. What a fricking joke. And the clown show continues…

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Getting more real world experience with G100UL is a good thing. I have the GAMI STC for my Maule but I haven’t run any G100UL since it’s not available in my area. Although GAMI did a huge amount of testing, running G100UL in a larger variety of aircraft, engines and flight operations over time will allow them to fine tune the fuel formulation, if necessary. I would like that to happen before I actually run G100UL in my Lycoming engine. I’m not worried about the manufacturer not honoring the warranty since my engine is long out of warranty. Most GA engines are out of warranty. According to the FAA, the average age of 150,000+ GA aircraft is over 50 years. We MUST get rid of the lead in aviation fuel just like we got rid of it in automobile fuel, which didn’t happen overnight. Getting G100UL into widespread use and closely monitoring engine health is the best way to gather more data about its effects and how to adjust the formulation to prevent engine damage. Instead of taking potshots at GAMI’s fuel effects, we should be trying to help them make it safer.

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The difficult part now will be separating out all of the normal wear and tear aircraft go through from the issues that are actually related to the fuel.

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First, airport neighbors complained about lead falling on their property, next they will complain about aluminum.

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It took the EAA from 1964 to 1982 (18 years) to convince the FAA it was safe to run mogas in an airplane. To this date, there are numerous airframe/engine combinations that do not qualify (eg PA28-181/O360). Petersen has expensive fuel system modifications to get PA28 STC and each airframe engine combination has to be tested before the FAA approves an STC for the airframe/engine combination.

There shouldn’t be a surprise that things might come up with a blanket STC for all airframe/engine combinations unless GAMI has tested all of the many hundreds (or more) combinations, some with post factory mods themselves. I’m glad they’re doing the big experiment in California and not where I am.

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Casting aspersions is not productive. We are going to have to move to unleaded fuel and taking the Luddite approach is not productive.

The big problem with these reports is determining causality. Peeling paint and staining is probably more of an issue with old and worn-out paint than anything else. Valve sticking is a long-time issue with Lycoming engines. Suddenly introducing an unleaded fuel at 1000 hours into a Lycoming engine and then blaming the fuel for a stuck valve is unreasonable. Did you do the wobble test before switching fuel? No? Huh.

So, let’s focus on light instead of heat. GAMI seems to be doing that. They have put more effort into fuel and combustion in aircraft engines than anyone else I know of. I really would like to see them taking the lead (unavoidable pun) on this. They know what they are doing. Joe 6-pack pilot, uh, not so much.

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Luddites trying to blame their poor maintenance on something new. Lawyers licking their lips; a very American problem.
Lead is bad for people and engines; we know that.
The Fuel companies and distributors don’t want to lose the extremely profitable 100 octane fuel market, so they encourage this kind of nonsensical attack!

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UL 94 will be the answer to the lead problem. Get ready to modify your engines with water injection.

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Anyone who has ever tried to roll out a new product to the market knows that, no matter how much testing you do, there will be some wrinkles and issues once you go public. Just ask Swift Fuels about that. As Brian1 said, it will be a challenge to determine whether any problems are truly related to the new fuel or just an incipient problem that suddenly appears. To be truly scientific, a pilot considering the switch to G100UL, or any other upcoming unleaded fuel, would be wise to thoroughly inspect his engine and fuel system to see if there are any issues brewing prior to the switch.

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As one who has been at ground zero (Reid HIllview) since the battle to close the airport started in 2016, and lead became the PR Weapon in 2021, it is important to remember two very important things. First, while not lovable, lead in Avgas is not killing people or harming kids, as it remains nearly undetectable relative to other sources of airborne lead and lead stirred up from the ground. And second, the unleaded Avgas race is like Betamax v. VHS with two companies competing to be the standard, using very different formulas. GAMI came out of the blocks first, by skipping a lot of testing, and Swift is catching up, with a product that has no signs of airframe or sealant/plastic damage. 2025 should be the year a winner emerges, and the drama will die down as the complexities of rolling out unleaded avgas progress…

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This again points to the need of STANDARIZED testing, i.e., ASTM.

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First, it’s inaccurate to say that GAMI “skipped a lot of testing”, when that testing took place over 10 years. The FAA doesn’t just assign widespread STC approval without a lot of engineering data to back it up. G100UL is probably one of the most tested aviation fuels on the market.

Second, there were “no signs of airframe or sealant/plastic damage” for G100UL until it came to market, so who’s to say there won’t be similar signs of concern when 100R eventually makes it to wide-spread market?

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The greater impact is on rubber. O rings and fuel bladders. The main substance that is used to bump the octane is Toluene which is a solvent. Toluene also degrades wet wing sealant.

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How do you know what testing was done or demanded by a local FAA Cert office? And what makes you think the local FAA Cert Office are competent with fuel testing? We have the producer’s word for it that the fuel is most tested, but the testing is proprietary and so do we get to see the poor results or if areas of concern were tested? You try asking for it and tubleweed rolls through.
From the data supplied it seems the fuel at least has an issue with nitrile elastomers (very common as they’re cheap) and the narrative that it’s related to the aromatic content ignores the obvious issue that the octane booster used (aromatic amine it seems) is more polar than aromatics and so will itself act as a solvent.

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Ya right, put the horse buggy manufacturer group in charge of automobile standards. How do you think that goes?

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If we are going to do ADI, might as well do it so it works with mogas and skip the whole need for a special avgas.

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There is perhaps two very clear challenges with the mogas. Does the engine do ok with the reduced octane, which relates to compression ratio, ignition timing, and cylinder cooling. Engines only tolerate very light detonation on the long term.
The other issue being RVP. Will the fuel flash in the fuel line?
G1000 has neither of those weaknesses. It is likely any weakness found will be much more nuanced.

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FAA’s role in Certification: According to Title 14 CFR parts 33, 23, and 27 (among others), new unleaded fuels in the US marketplace must have FAA-certified approval for the appropriate engines, airframes, and rotorcraft intending to use the fuel. This FAA certification approval can come via a TC, STC or PAFI-type approval for a defined aviation fuel. To my knowledge the FAA is actively involved in all these areas of certification for the 3 fuels in the EAGLE program.

ASTM’s role in Fuel Standards: FAA statutory requirements, airworthiness directives, guidance documents and advisories also describe the use of voluntary industry consensus standards for avgas outside of FAA (e.g. ASTM International) to augment and reinforce the FAA’s Title 14 regulations. Industry consensus standards to increase and reinforce FAA certification efforts are called out in the FAA Reauthorization Act of 2024, OMB A-119, and AC20-24-D, among many other references. These industry standards also target fuel production, quality control, proper handling, and global supply chain aspects of the fuel – particularly upstream of the aircraft.

FAA’s 14 CFR Part 23 airframe regulations provide a thorough criteria of airworthiness standards and flight operations; however, these federal regulations tend to offer only high-level guidance on the importance of aircraft material compatibility. For example, in Section 23.2260 – the regulations describe materials and processes that provide clear guidance but only make vague references to the type of materials used in aircraft. To supplement this, ASTM International working with FAA, Industry and aviation OEMs has developed a comprehensive industry consensus standard for new aviation gasolines over the past 20 years called D7826 which thoroughly outlines numerous fit-for-purpose test requirements and specific aircraft and engine materials required by global industry participants to test some 32 metals, and over 50 non-metallic parts including fuel bladders, O-rings, diaphragms, anti-corrosion paint, epoxy-liner coatings, tank sealants, fabrics, hoses, composites, and many more items. Swift Fuels’ FAA STC program began testing all these ASTM D7826 specified items during PAFI and also from the beginning of our current 100R STC program, because the FAA part 23 requirements were known by industry to need additional clarity and augmentation on many of these critical points. Swift Fuels has reported all this information to FAA and to ASTM International and other industry groups on many of our test results pertaining to items since 2018.

Our FAA-approved Swift Fuels’ STCs do not allow the use of G100UL to be mixed with any of our fuel products due to the detrimental behaviors we believe are caused by 3+% meta-toluidine used in G100UL that has been reported to disturb fuel systems, impact aircraft performance, and disrupt supply chain assets. Swift Fuels has repeatedly reported these matters to industry based upon our own proprietary fuel testing that highlight these concerns. Accordingly, there is no indemnification to any third party by Swift Fuels if harm or destructive compatibility problems occur from using G100UL with our marketed unleaded fuel(s). It is our understanding that to date, the producers of G100UL have not and will not pursue an ASTM International industry consensus fuel specification. I believe this omission of ASTM testing to ultimately earn industry consensus fuel specification is a major defect for G100UL that should give the aviation industry and piston aviation pilot’s serious concerns.

Bottomline: FAA Certification + ASTM International Fuel Specifications is the minimum industry standard for a commercially available avgas.

Chris D’Acosta
CEO – Swift Fuels, LLC

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