Originally published at: Op Ed: The 'Tortured Path' of Unleaded Avgas
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…
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.
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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.”
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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:
- Octane (including supercharge rating) ~ same as 100LL;
- Fungible with 100LL in the FBO tanks and the wing tanks of the aircraft;
- Can be produced within existing industrial refining facilities;
- Cost ~ comparable with 100LL;
- FAA Approval for “Nearly All” Aircraft.
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)