I have been following the tortured path of Unleaded Aviation Fuel development, and I feel that this is a classic example of: “Those who fail to learn from History are condemned to repeat it.”
In my humble opinion, the requirement that unleaded aviation gasoline be “backwards compatible” with leaded aviation gasoline is proving to be both unworkable and the biggest barrier to adopting unleaded aviation gasoline. I’m not the only one who thinks so. Some in the petroleum industry tasked with meeting the compatibility requirements have stated publicly that backward compatibility is an impossible goal, and that the goal of backward compatibility should be abandoned.
History is instructive and provides a path forward in the example set by the EPA for the auto industry. When the EPA mandated unleaded gasoline for all new cars, starting with the 1975 model year, they didn’t impose a backwards compatibility requirement that the fuel be compatible with existing cars. Instead, they permitted the continued sale of leaded gasoline, right alongside the new unleaded fuel. New cars were fitted with a restrictor in the filler pipe to prevent mis-fueling with leaded gasoline, and the unleaded gasoline pumps used a smaller fill nozzle, to fit the new restricted filler necks. The older cars continued to use leaded gasoline as they always had, until leaded gasoline was finally banned completely, seventeen (17) years later, in 1992.
When leaded gasoline was finally banned completely, drivers of older cars had three (3) options.
They could buy a lead additive at the local auto parts store and add it to the gasoline tank at every fill up. Inconvenient and expensive, but necessary to prevent engine damage.
They could rebuild the engine to be compatible with the unleaded fuel, by replacing the valve guides and valve seats with hardened equivalents during a “valve job”. Also expansive and inconvenient, but a much easier pill to swallow, since the overhaul only needed to be done once, and the the conversion to unleaded fuel compatible parts could be done as part of a necessary engine overhaul for almost no extra cost over the basic overhaul.
Or, they could replace the original engine with a brand-new “crate” engine from the original manufacturer of the car. Also expensive, but again, only needing to be done once, and the new engine could be bigger and more powerful than the original engine being replaced, so there’s that.
So let’s ditch the backwards compatibility requirement and get this show on the road. I would, however, require that any replacement or overhauled engine be made compatible with the lead-free fuel, to receive an airworthiness certificate, to speed the process of retiring leaded aviation gasoline for good! A newly rebuilt engine installed in an airplane could have the airplane be fitted with the restrictor plate in the fuel filler neck(s) of the airplane’s fuel tanks, and a decal placed around the fuel filler cap(s) withe words “Unleaded Fuel Only”, just like it would be applied to new airplanes that meet the new rules, or have been placed on all cars manufactured and sold in the United States since the 1975 model year (September, 1974).
The much smaller installed base of aviation engines compared to automobiles should make this process go much faster than the seventeen years it took to purge leaded gasoline from the nation’s automotive fuel supply.
So stop dithering, and “Git’er done!” Our lungs and nervous systems will thank you for it!
Sincerely,
Mr. Robert G. Atkinson, Jr.
Op Ed: The ‘Tortured Path’ of Unleaded Avgas
Key Takeaways:
- The primary obstacle to adopting unleaded aviation fuel is the unworkable requirement for it to be "backwards compatible" with leaded aviation gasoline.
- The author suggests learning from the EPA's successful transition to unleaded automotive gasoline, which allowed both fuel types concurrently and only mandated new vehicles be unleaded-compatible.
- The proposed solution for aviation is to abandon the backward compatibility requirement, allow both leaded and unleaded fuels, and mandate that all new or overhauled aircraft engines be made compatible with the new unleaded fuel, accelerating its adoption.
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It’s not that simple with aviation. Especially the turbo prop aircraft that require the leaded fuel. Extensive modifications would need to be done, and the weight carrying capacity would suffer significantly. I remember someone trying to recreate the Doolittle operation. On 100 low lead, instead of the 130 high octane leaded fuel. The attempt failed. The engines had to be de tuned so far to run the 100 low lead, that recreating the stunt failed.
No need to install fuel tank restriction. The only reason they were installed on automobiles was to protect the catalytic converters that were mandatory at the 1975 model year. Leaded fuels then would and will still now plug up a converter. The higher octane is needed for turbo and high horsepower aviation engines. Any reduction in power would affect all multi-engine certification making some airplanes unable to meet certification standards. It would also affect the weight carrying certification standard of high performance single engine planes. Making engines able to run on unleaded fuels as far as valves are concerned is not a problem. Keeping the detonation margins in high compression engines is the problem. This suggestion by the author would ground most planes that need 100 octane. One of the reasons I bought an older C172 with an O300 engine. That engine will run on just about any unleaded auto or aviation fuels now being sold, and I have the FAA approved paperwork to make that legal. I sacrificed performance that I would have had with an O360 conversion to get an airplane that doesn’t need 100LL! Most pt135 charter operators don’t have that option and this suggestion would put all of them out of business.
I have to agree with your thinking. On our current path that we have been on for at least 40 years now we have really gone nowhere.
UL 91 or UL 94 needs to be made available at most airports in order to make a viable transition. Currently, we are getting nowhere it seems.
The government and the AOPA has definitely let us down with absolutely no real promotion of the transition fuel product, in fact, they are actually standing in the way by mandating the continual use of leaded fuel, instead of mandating a transition product.
The real issue that has hung it up is who has to pay for it. If the backward compatibility is dropped everyone with an engine that requires leaded avgas will have a huge bill to pay. The backward compatibility doesn’t really get rid of the problem it just spreads it across everyone. Then there is the issue that any major change is likely to change who is currently getting the money and that is a major cause for lobbying by the current established players. In the end the issue is just about money. If we had even 1-2% of the volume of the car manufacturers this wouldn’t be an issue but there really just isn’t enough sales there to spread the cost over. Lets face it most people flying an old 1970s or earlier high HP aircraft can’t afford a quarter mil or more to put new engines in their aircraft. If they could most of them would have moved over to an older turboprop. of course the warbird market is another issue as well though most of them could probably afford to have specialized gas delivered. I do kind of wish the airports would start offering UL 91 or UL 94 before I get my RV-9A finished I would actually prefer to never put leaded fuel in it. The big thing I am a bit concerned about is if we do get a drop in fuel that ends up costing 9-10 dollars a gal it could really kill the already fragile GA market. We really do need to find someone to fix the GA cost issue. When 172s cost 4-5 times as much relative to salary’s at they did during the 70s and new IO-320s with mags (one of the simplest engines currently sold) cost almost 3 times the cost of the most expensive corvette crate engines we really can’t afford somthing that drives the cost up for most of us,
Why does no one consider the storage issue? Part of the “backwards compatible” is long time storage. Car gas starts to lose it’s octane rating in as little as 30 days, not an issue when filling stations and cars are replenished weekly. But my lawn mower does not run after it sits idle all winter with car gas in it. Avgas is by MIL spec good for two years. Aviation fuel must be “backwards compatible” in that respect.
I bought the $600 GAMI G100UL STC early on for my Maule MX-7-180 with a Lycoming O-360-C1F engine. I’ve been waiting for G100UL for the last 3 years so in my case it isn’t the backward compatibility issue that’s the problem. Instead it’s a fuel availability problem. I realize that Vitol’s production of G100UL started on the West Coast initially and hasn’t yet reached the East Coast but it’s taking a long time to happen. So far only about 0.5% of the piston GA aircraft fleet have purchased GAMI’s STC so there’s not a big demand for it yet. I’m sure that Vitol and AVFuel are looking at the demand numbers to figure out where to expand the distribution network. A big part of the demand problem is that there’s no economic incentive for a FBO to buy G100UL since they can’t be sure of selling it. I see two ways to change that: environmental restriction on leaded AVGAS or federal/state subsidy to FBOs that buy it. So far no one seems to be talking about either alternative any earlier than EAGLE’s goal of phasing out leaded AVGAS by 2030. A goal isn’t the same as a law so I doubt that they will achieve the 2030 goal. I think everyone agrees that lead is bad for the environment so why not introduce legislation to make the 2030 deadline a law and simultaneously offer subsidies to public airports that agree to sell G100UL or one of the other EAGLE competitors? At heart, I think this is an economic problem. It took about 20 years to transition from leaded automobile gasoline to unleaded gasoline and there were competing incompatible products like the difference between G100UL and 100R. Economics eventually drove the market to standardized unleaded autogas but EPA’s ban on the sale of leaded autogas in 1996 completed it. If we just rely on aircraft owners to voluntarily purchase a GAMI or Swift Fuels STC, it’s going to be a really long process!
Nobody ever asks the question why, with such a limited amount of general Aviation activity, why on earth this is needed to begin with? There were billions of gallons of leaded gas consumed for 100 years and the human species survived. Then compare that to the minuscule amount of Avgas consumed and it’s nothing but a political feel good football.
No mention that the world’s largest producer of aircraft engines, Rotax, has a policy that all its engines must operate on lead-free, ethanol-free mogas, available at most GA airfields in Europe. Something like 70% of all legacy aircraft in the US operate just fine on mogas with an inexpensive STC requiring no modifications other than a placard. If anyone wants to point a finger on who is to blame, look at the aviation alphabets, especially the EAA, which obtained the original mogas STC decades ago but in recent years has been behind the pipe dream of a one-size-fits-all Avgas replacement at any price. Take Cirrus out of the picture and there would probably be very little support for an Avgas replacement. Let it continue being sold as Rotax and other modern aircraft engine makers replace the dwindling number of aircraft engines that need Avgas.
Continental TSIO-550-K used in the Cirrus SR22T is certified for 94UL unleaded aviation gas.
Maybe a good step towards the fuel issue would include removing type certificate rules for Vintage aircraft. I’d like to see the FAA create a new category of aircraft for Vintage aircraft. Call the category Certified Vintage, where aircraft over 50 years old are treated more like experimental, but still be required to use aviation equivalent components (not requiring PMA or TSO). Equivalent parts would include parts commonly used in experimental aircraft kits. A like for like when it comes to weight so aircraft don’t become unsafe. For example, a Piper cub would be able to have a Rotax engine installed. Instead of STC, have a Compatible Replacement Part(CRP) document; where the document demonstrates like or improved performance without changing flight characteristics, (not altering the CG). These CRPs could also be sold like STCs, but do not require the level of scrutiny as an STC. The CRPs would be logged and documented similar to an STC; and either revoked or AD’s issued if the CPR is proven to have issues or be unsafe. The CPRs would show steps and measurements and would be approved by a local FSDO. The FSDO would be required to approve within 90 days unless they provide proof of unreasonable risk.
I fly a Rans S-20 with a fuel injected Rotax. It starts and runs like a modern car engine but with dual ignition and fuel controls and dual fuel pumps. Problem is that most airports do not have unleaded fuel. The Rotax will run on leaded fuel but the lead contaminates the oil, the valves and the spark plugs not to mention the pilots or fuelers. Rotax actually recommends running E-10 rather than leaded fuels. I have a different solution for the high performance engines that require higher octane fuels. This solution is not a new idea and dates back to WW2. Add a separate tank for alcohol or an alcohol water solution and inject this directly into the intake manifold at high power settings. Most of the time at cruise, the engine would run OK without the injection so the tank would not need to be that large and injection could be automated. This would keep the oil and the engine cleaner. It is way past time to get the lead out. Of course, the other solution for new aircraft is use liquid cooled engines which are lighter and can run higher compression without the high temperature hot spots that require the higher octane fuel. Just look at the power to weight ratio of the Rotax or MWFly. MWFly offers a 220 hp engine that weights 222 lbs and runs on mogas with or without ethanol.
Here we have another comparing aircraft to cars, cause that’s what they know.
They also want other pilots and owners to conform to their wishes. Never mind any others. Its what they want and to h___ with others, with an industry, etc . Kill an industry to feel better. Never mind we’re the only country trying to save the environment.
Pilots and owners need to keep fighting to be able to fly, whether its for fuel, airspace, or whatever.
GAMI 100 fuel has no problems except the desire of legacy providers to prevent its’ availability.
The fuel has a better detonation margin than 100LL.
The fuel is stable.
The fuel is available at the manufacturing facility.
By all accounts, 100LL is extremely profitable,
That is why the current providers are fighting so hard, using disinformation and nonsense to hang on to their market.
There is no real issue of “Backwards Compatibility”.
The real issue is the ignorance of parts of the aviation community, and the greed typical of US big business.
Lead is bad for engines;
Lead is bad for people;
Get the facts;
Get over it!
FACTS that are well established:
A) About 60-70% of 100LL is consumed by aircraft that require high octane aviation gasoline;
B) It is politically impossible to keep using leaded avgas, regardless of the actual health hazards associated with exposure to atmospheric lead;
C) The only producer of TEL has stated to AOPA that they intend to stop TEL production, possibly sooner than 2030. That has been verified by other industry fuels companies;
D) There is only one avgas storage tank at the vast majority of airports;
E) Airplanes stop at different airports during their normal use;
F) In light of D & E, above, any replacement fuel, must be backward compatible with 100LL in the engine and fuel system - - “fungible with 100LL”.
G) From both an engineering-certification perspective and an economic perspective: It is impractical and likely impossible to “retrofit” the fleet of high performance piston aircraft in a manner that would allow them to operate on lower octane (including both the MON rating and the supercharger rating) avgas.
H) Congress has allowed airports to stop selling 100LL (without impairment of the grant assistance money) when the airport provides an alternative avgas that is approved for “nearly all” of the aircraft (aircraft = rotorcraft + airplanes).
I) There is one high octane unleaded avgas now approved for 98+% of the aircraft.
J) The Courts have held that the term “nearly all” in Congressional bills means “more than 85% but not all.”
In 2010, when GAMI started the certification testing for G100UL Avgas, the first thing its engineers did was to create the following set of “Design Requirements”:
Requirements for an unleaded replacement for ASTM D910 100LL:
Two major name brand producers of 100LL have told GAMI that those are the correct design requirements for an avgas to replace 100LL.
The fuel approved by the FAA on September 1st, 2022, for use in “nearly all” aircraft, fully meets those design requirements.
There is much to much disinformation and confusion about this subject !
True, the unleaded fuel requirement was to protect the catalytic converters, but separating leaded from unleaded gas is still a good idea. Besides, you don’t think the EPA is going to stop at just unleaded avgas, do you? “Cats” for airplanes will follow just as surely as they did for cars, with the same results: More electronic engine controls, greater cost and complexity, but with much higher reliability.
The fuel storage issue is largely a result of the ethanol added to “mogas”. No ethanol, no problem. Automotive gasoline without ethanol is available, but hard to find and expensive. There’s no reason why ethanol has to be added to aviation fuel. Frankly, there’s no reason to add ethanol to auto gas either, that decision was political, not technical. It was done to help farmers in farm states find another market for corn, when corn exports were restricted as a result of one trade dispute or another. “The opposite of progress is Congress!” - John Adams.
Once the lead is out, then refiners can refine “avgas” in the same refineries that they use for “mogas”, and retire the dedicated refineries, pipelines and tank trucks that are necessary to keep lead out of the automotive fuel supply. The resulting cost savings should result in lower prices for “avgas” overall. A lot depends on the oil companies, who will probably keep the savings to bolster their profit margins instead of passing the savings along to the aviation consumer, but even so, the resulting increase in availability and higher profit margins are all good things that will keep the fuel flowing to users.
Not so. 20 years ago old auto gas was no good after a couple of months in my lawn mowers and tractors. and turned to shellac in about a year. without ethanol. way before ethanol.
Also, the unleaded fuels need to be all one standard or compatabñe with each other. This is not happening right now. The new fuels are all compatable with 100LL but not each other. We can’t have different incompatible unleaded fuels at different airports.
I am sure Mr. Braley would (rightfully) cringe at having to make his GAMI fuel compatible with all the others.
So the FAA needs to figure out how to select one fuel or standard.
Vince Massimini
Kentmorr Airpark MD (3W3)
Not sure who the author is, but he seems to parrot what the “industry experts” say - that is those trying to protect their territory. GAMI has a fuel but even the EAA folded and stopped so much as mentioning it. (I wonder what (loss of) money was held over their heads?) I thing brianhope said it right - the problem is corporations who have no product ready, and all the Luddites who don’t want to switch because it’s new.
Andrew_M is right that financial incentives might be necessary to make the change - this market is just too small to absorb these costs easily. I’m thinking of our local airport - owned by a retired pilot who barely makes a profit on the place. He does it for the love of aviation. There is no way he could afford an entirely new fuel delivery system.
And, of course, George Braly has thought this out very well. It’s only money that keeps people from listening - either the potential loss of it, or the cost to convert/add G100UL (both aircraft and airfield).
Robert,
Lead or No Lead :
Avgas is not produced insufficient volumes to warrant transportation in pipelines.
The contamination of one batch of fuel with another at the beginning and end of a pipeline run would not be an acceptable with the small volumes of Avgas.
And Avgas could not stand the contamination (lower octane) from even small amounts of autogas in the “tail” left over from pipeline shipments.
George
One has to be careful in discussing compatibility of fuels.
If one is going to use the “mixed” fuel in a engine already approved for use of Swift 100R ( there are only two aircraft so far approved for use of Swift 100R - - two make/model C 172s) then there is no immediate safety issue with mixing G100UL avgas with Swift 100R.
But it is NOT a two-way street. You could not used the “mixed” “comingled” fuel in a Bonanza without likely causing detonation and other problems.
Because of the potential risk of confusion with this issue, it is easier to just say “don’t mix them.”
We have extensively tested fuel made to conform to the Swift composition with 25% ETBE - - on our elaborately instrumented test stand at GAMI.
Those tests demonstrate that 25% ETBE fuel blends like Swift 100R will not operate safely on 8.5:1 high performance engines, without serious modifications and/or derating/restrictions on the engine operating envelope. For twin engine aircraft, that might not even be possible do to the single engine performance requirements.
Anything you see or hear to the contrary is simply mis-informed or based on erroneous data.
George
Catalytic converters were designed and deployed to reduce smog.
They did a superb job.
Aircraft engines at altitude and with their three-dimensional dispersal of any exhaust emissions do not contribute to smog.
George
That may be true, but that still leaves fleets of dedicated tank trucks and any refineries dedicated solely to aviation gasoline to deal with. I don’t know how many refineries are dedicated solely to aviation gasoline production, but my guess would be no more than one or two, at most. Switching to unleaded fuel will move that production to a wider base of production facilities, preventing a possible single point failure, if the only refinery dedicated to leaded avgas has to shut down for any reason.
I must respectfully disagree with your contention that visible smog was the only issue in air pollution controls for automobiles. The three (3) regulated pollutants, carbon monoxide, oxides of nitrogen and unburned hydrocarbons, all have undesirable health and environmental effects. Oxides of nitrogen react with water in the air to form nitrogen acids (nitrous acid, nitric acid) which contribute to acid rain. Unburned hydrocarbons react with sunlight to form photochemical smog, yes, but carbon monoxide is a real hazard to pilots, passengers and those of us on the ground alike! The catalysts were fitted to reduce those pollutants in all levels of the atmosphere. Oxides of Nitrogen have also been implicated in the destruction of Earth’s ozone layer, well above operational flight altitudes. Anyone who has driven behind a pre-emission-controlled car, without a catalyst, can smell the difference in the exhaust! So, no it wasn’t just visible “smog” that forced the rules, but these invisible components of internal combustion engine exhaust as well.
Studies have shown that residents near General Aviation (GA) airports have higher lead levels in the blood, with documented effects on the brain and central nervous systems of those people. The effects are most severe on the developing brains of young children, so getting the lead out is of vital importance to all of us!
I’m inclined to agree. This prompts me to ask a question, though. Since warbirds used to use 130 octane aviation gasoline, where do they get the fuel necessary for them to run as they were designed to run? As far as I know, 130 octane avgas is no longer sold, at least in the US, and 100LL won’t be good enough for these incredibly powerful engines. Detonation would be a huge problem, so how is that issue addressed? Do warbird pilots have to add octane boosters to the fuel so the airplane can run without damage? Thank you for your help.
Back before G100UL was available, I suggested ‘replacing’ 100 LL with Jet-A:
Stop selling new avgas airplanes and engines, and sell diesels that can run on jet-A instead. Existing engines could be replaced with diesels when they reach TBO. The extra costs would be offset by lower fuel burn of the new diesels. Airports and FBOs would actually save money because they would only have one fuel type.
Anyway, now that G100UL is here, that is no longer necessary. G100UL IS backward compatible. It just doesn’t have the scale of production and distribution that 100LL enjoys. Airplane owners have no reason to buy the STC, because they can’t get the fuel. And FBOs have no incentive to offer it, because not enough of their customers have the STC. The existing producers and suppliers are digging their heels in to prevent G100UL from gaining market share.
People say that the existing producers want to keep their money from making 100LL. GAMI is not a fuel producer, so they are not competing. They sell a license to make G100UL. Is that license fee so expensive that the fuel producers can’t profit? When TEL is no longer available, what do they plan to do?
All auto engines are water cooled and not comparable to air cooled aircraft engines due to exhaust valve heating and deterioration in air cooled aircraft engines from unleaded avgas. Air cooled engine exhaust valves need a replacement for lead; either finely ground iron or copper or some combination to cool the air cooled exhaust valves. The FAA needs to mandate either iron or copper or some combination for air cooled engines to obtain exhaust valves that will last more than 2000 hours of operation. From personal experience, unleaded avgas exhaust valves will burn in 100 to 400 hours of use; totally inadequate and unacceptable.
“We have extensively tested fuel made to conform to the Swift composition with 25% ETBE - - on our elaborately instrumented test stand at GAMI.”
I’m amazed to see this written down as I understood that Swift had a patent granted for their fuel.
If so (and I have some legal experience), that would make blending and / or testing without their permission illegal here in the USA. Of course you testing Swift’s fuel would be possible if the fuel was obtained commercially (which I don’t think is possible yet), but it is not legal for someone to independently blend and test something that is covered by existing registered Intellectual Property.
It’s an interesting testing observation, but you might want to alter your post before Swift lawyers contact you…
I think the 1970 Clean Air Act was used to push the change to unleaded fuel to have a supply across the US was accomplished in less than 2 years. The catalytic convertor saw to that. The unavailability of G100UL is because the EAGLE has spoken and the Fuel Distributors refused to transport GAMI. When an inferior unleaded fuel was championed by EAGLE, it assured the industry of having leaded fuel available long after any of us stop breathing air.