AOPA’s Beech Baron ran 200 hours with 100LL fueling one engine and GAMI’s G100UL the other (Photo: AOPA)
Industry wide progress on a so-called drop-in replacement for high-octane avgas always seems to go in fits and starts. Lots of noise then a period of silence. Is anyone actually doing something on this, you may ask? The answer is most definitely yes, but the recent news has come more in dribs and drabs than the full-firehose effect we expect around the major airshows.
But let’s start here. The other shoe dropped on the sale of leaded avgas in California. There had been a legal agreement (a consent decree) that depended on the availability of an alternative to 100LL but now the transition is being forced by new legislation signed into law this month that “would prohibit an airport operator or aviation retail establishment, as defined, from selling, distributing, or otherwise making available leaded aviation gasoline to consumers on or after January 1, 2031.” Coincidentally, the End Aviation Gasoline Lead Emissions (EAGLE) program has as its goal a replacement in place by the end of 2030. Reportedly, the California effort was originally slated to take effect earlier but was pushed back with the help of aviation special interest groups.
According to reports, there are still three candidates in the unleaded-avgas derby, so to speak. General Aviation Modifications, Inc. (GAMI) has had its G100UL fuel in development for decades and received a fleetwise STC in 2022 for virtually all fixed-wing aircraft. GAMI has chosen not to participate in either the current EAGLE or its predecessor PAFI programs that are pushing for an ASTM spec for the replacement fuel. GAMI’s path has got it well and truly cross-threaded with the industry groups.
One could argue that GAMI is trying to “go it alone,” but recently Swift Fuels, which, in addition to VP/LyondellBasell, makes up the remaining contestants on the scene, has received an STC for its 100R to be used in Cessna 172R and 172S models. Swift CEO Chris d’Acosta said, “Our 100R unleaded avgas product will be the preferred fuel to eliminate toxic lead from avgas. We are actively working with industry and OEMs on FAA-certifications and ASTM International specifications. Yes, the FAA recently approved a critical part of our engine and airframe (STC) certification program. This follows a similar FAA / ASTM approval pattern we architected for UL94 avgas over 9 years ago.”
Getting the Swift 100R into public use would help the company gain real-world experience with the fuel. Similarly, the demonstration program undertaken by AOPA last year has concluded, according to reporting by the association. AOPA had run a Beech Baron for 200 hours with one engine consuming just 100LL and one consuming only GAMI’s G100UL. “The pilots who have flown the AOPA fuel demo Baron have been unanimous that the unleaded fuel used—GAMI G100UL—acts just like avgas in flight. No special techniques are required for engine starts, full-power takeoffs and climbs, cruises, or descents. If the airplane didn’t have decals and placards proclaiming the presence of unleaded fuel in the left engine, pilots would be hard pressed to notice,” the association said.
Testing did reveal some peculiarities. Apparently an overly rich mixture will leave a dark, ashy deposit on exhaust pipes and spark plugs. In addition, the fuel will apparently stain paint if not carefully cleaned up. In the AOPA report, GAMI founder and developer of the G100UL fuel, George Braly, said “If the fuel is left on the surface and exposed to the UV from sunlight, then that will cause some brown discoloration.”
Finally, there was a very public display of a leaking fuel bladder in the Baron on the side that was using G100UL. According to AOPA, the culprit was more likely old fuel bladders, which were originally made in the 1970s (but later “refurbished”), than a corrosive effect of the fuel.
So where does that leave us? GAMI has approval for fixed-wing aircraft now but has yet to make G100UL widely available. Swift will be seeing 100R flying in certain Cessnas. And VP/LyondellBasell is still in the development phase, which is working toward getting an ASTM spec. With California backing down from making leaded avgas illegal until 2031, some of the pressure might seem to have come off, but the clock is still very much ticking.
I know that Rotax engine support 100LL and Unleaded fuels, but has there been any testing with either GAMI’s G100UL or Swift’s 100R? Last time I was at Lockwood, they very much preferred using the Swift 94UL fuel in their aicraft.
Wish I could get my hands on 94UL for my own Rotax.
Agreed. Too expensive to try and buy a fuel tote as an individual.
why can’t you just buy mogas?
In the US, around 200,000 type certificated aircraft and another 40,000 experimental aircraft that fly around 40 hours per year on average. At one part per million lead in avgas, this current flying accounts for maybe 5% of the lead in the atmosphere with volcanic action placing 95% of the lead in our atmosphere. Or no need to remove lead from avgas; especially since the lead keeps exhaust valves from freezing to their seats. And Cirrus says they will not endorse any lead free gas in their aircraft. This has been a dead issue since day one with almost no one looking at the facts given here. Sensibility is rare in California. Knee jerk reactions in California without examining the facts are common there having lived there in the distant past.
I’d note that the lead compound being organic in tetraethyl lead is extremely relevant for health hazards, as compared to lead compounds from volcanos which don’t tend to have carbon at all.
The ethyl groups make it so that our metabolisms actually try to bring it into cells for processing, making much more severe heavy metal poisoning.
It was necessary to remove the lead from auto gas with how many billions of autos on the road? 240,000 small aircraft using 1 part per million lead is less than nothing. As stated less than 5% of the total output to atmosphere with volcanic action causing the 95% plus remainder; plus what ever else is placed in the atmosphere by others. I assume you are suggesting tetraethyl lead is more dangerous than volcanic lead. Maybe so, except doing the math: 1 ppm in aircraft burning 7 gallons per hour on average for 40 hours is 280 parts per million spread over the entire US. Or with 240,000 aircraft in the US flying 40 hours per year on average, that amounts to 67,200,000 ppm divided by 1,000,000 is 67.2 parts of avgas at 7 pounds per gallon or 470.4 pounds of tetraethyl lead per year spread over the entire US. But, really, why isn’t the US Weather Bureau and the EPA measuring all the other toxins in the atmosphere in addition to the volcanic activity? Sorry, your sense of proportion with all of the other toxins in our atmosphere is just missing!! If unleaded gas actually worked in aircraft engines, no argument would exist. The exhaust valves stick to their seats eventually causing a loss of an engine cylinder. Most small aircraft are single engine, meaning loss of a cylinder is an immediate off field landing; if even possible. In metro areas, other people are likely to be hurt or killed; where most of the small aircraft are located. A large spike in aircraft engine failures is likely to occur with the removal of lead with increased loss of life. The unleaded avgas manufacturers say they have looked for and found a substitute. This is not believable knowing the weight of lead and how it appears to create a safe environment for exhaust valves. No substitute exists for tetra ethyl lead at 1 part per million in avgas, unfortunately. The avgas manufacturers over 50 years reduced the lead in avgas from around 50 ppm to 1 ppm at the insistence of the EPA; which almost no one argued with. The line in the sand is drawn. With the loss of the first few hundred aircraft using unleaded avgas, I expect that insurance companies to sue the federal government and the unleaded avgas manufacturers for more than they can afford to pay! Where this situation appears to be headed! This discussion has no end if you add in diesel fuel; much, much worse the 1 ppm of TEL; especially by the volume burned by the trucking industry in the US. How many millions of large trucks are on US freeways and highways? And they get what? 2 gallons to the mile? With on average 20 parts per million toxins in number 2 diesel fuel!! Where the real problem is located; with diesel fuel no 2. Priorities matter; and almost no one has made a priority list by the amount of toxicity to people and animals. I call this shame, shame, shame, at the EPA! Scorn for such intransigence will likely show up in court. The attorneys will make certain the public has a real picture. Number 1 diesel fuel is better at 2 to 5 parts per million toxins in it; but 2 to 5 times worse than the 1 PPM of TEL in avgas! Except number 2 costs 10% to 20% less than number 1. So, truckers buy number 2 diesel fuel probably 5 to 1 over number 1 diesel fuel. A very, very big diesel fuel pollution problem, world wide, not just the US. The 400 pound gorilla in the room no one will address. The truckers own the country through their congressmen; along with another 2 dozen other groups. The one group the EPA pays attention to; the US Congress. The real picture as I know it. Tell the knee jerkers to go hide, please! And stop the wining about TEL in avgas!
I’m so confused. Where are you getting this 1PPM number for 100LL? Lead content for 100LL is 2 grams per gallon. That’s not 1PPM. It’s over 800x that amount. Perhaps you want to revisit your conclusions.
He threw a bunch of text and numbers without actual basis in reaponse. Basically a gish gallop while avoiding actually acknowledging that the main hazards from organic heavy metal compounds is in their unburned state along with changing subject to other fuels for a derivative of what-about-ism.
Lets us assume you are correct; then 240,000 aircraft burning 8 gallons an hour is 1,920,000 gallons of avgas per year. At 2 grams per gallon TEL, is 3,840,000 grams of TEL in the US Atmosphere per year. At 454 grams per pound or 3,840,000 grams divided by 454 grams per pound or 8458 pounds of TEL spread over the US per year. 8458 pounds of TEL in the US per year divided by 3,790,000 sq miles 0.0022275 grams per sq. mile TEL in the US per year; or 2.2275 milligrams per sq mile TEL in the us per year. So where is the problem?? Snake bites and small critter tetanus are at least 10 times the problem. Do the math!!! Or accept what I have given you here!