In a recent column, I recommended that in the future general aviation actually needed two grades of unleaded fuel, with one being an unleaded 100 octane product and the other a less expensive 82 octane fuel based on automotive fuels.
We received a lot of great feedback on the column, which is always appreciated.
But one of the points I took away from the discussion was that there is some confusion as to how the ASTM process compares to Supplemental Type Certificate (STC) approval.
Some people even thought that they were basically the same.
In reality they are very different and most of that difference goes back to our old friend liability.
In a certified aircraft, the type certificate list all of the parts and consumables that go into the aircraft. If you could examine the type certificate of almost every aircraft in the general aviation fleet, it would note that the fuel needed for operating that aircraft must meet the ASTM D910 specification for a listed octane rating.
In case of an engine failure, accident, or incident, because the type certificate indicated that the manufacturer has specified a list of parameters for the fuel, all the fuel supplier is required to prove is that their product meets that specification.
Under the same conditions, a fuel supplier that supplies a fuel under an STC must prove that their product did not cause the problem in any way. This is because the manufacturer has not agreed that the STC fuel will meet the “needs” of their engine.
In fact, in a high dollar lawsuit the lawyers will name everyone involved and hope that the different parties will implicate each other.
This brings us to the debate on how to approve the new 100 octane unleaded fuels.
General Aviation Modifications Inc. (GAMI) is going the STC route for now, earning FAA approval in September 2022 for every piston engine in the FAA database.
To use this fuel, an aircraft owner must buy an STC. And, if there is a problem, GAMI will face the liability issues on its own.
The other fuel suppliers are planning on going the ASTM specification route.
Once a fuel is approved through this method, it is considered a “fleet approval,” which means it is approved for all general aviation piston aircraft engines. No STC need be purchased, as engine manufacturers will issue documents stating that these fuels are approved in all of their engines.
This will be a much safer path forward — in terms of liability — for the fuel providers.
But there will be one big problem still facing the general aviation community: Who will approve fuel for the orphan engines out there?
If 100LL is outlawed, what will the Wright, Franklin, and other orphan engine aircraft use?
Many of the private planes that use these engines can fly in the experimental category, but aircraft that are used in commercial service cannot do that.
So will they just need to be scrapped?
Or will the FAA or EPA say they will approve the use and take on the liability risk?
I think not.
I believe that the only organization that could do that is the US Congress — maybe — and they have trouble deciding what to do for lunch.
I do not see them taking on a problem like this, especially since there is so little money in the GA world.
There’s a podcast called “Aviation News talk” check out episode 222 that interviews the creator of GAMI fuel G100UL. This fuel was tested by the FAA in a Laboratory and it was seen to be able to run in those High Octane, Fire Breathing engines from WWll with absolutely no problems. The Bureaucracy to get this Fuel approved is incredible. Check out the podcast. You will be amazed.
I don’t see why this story did not include UL 94 and why it does not have the ASTM certification. It talked about auto fuel, but didn’t mention the fact that it’s really not available without alcohol in it in most states, which makes it totally impractical.
Amazed how the 94UL subject is avoided here as if it doesn’t exist, even though it might be the elephant in the room. The talk of car gas which is only available in California laced with corrosive ethanol means that 94UL might be the best possibility there and now about 8 different airports in California have it.
With GAMI not only will every aircraft owner have to pay for an STC to use it but every gasoline producer will have to pay a per gallon fee to produce the gasoline that meets the aircraft owners paid for STC. Per gallon forever and ever! What liability will they have? My guess is none because whatever name they place the ownership of the gasoline STC will have no assets other than future sales but if the gasoline turns out to have a problem what sales will there be to make claims against. I suggest stick with the ASTM route and let the formula be open source to whoever wants to get in the market to produce. The government is handing out large grants to help formulate the new style gas. The formula should not be private once it’s created.
Mogas STCs from Petersen and the EAA have been around for 40+ years. Thousands of pilots have flown on nothing but mogas for 40+ years with rarely an issue. Most of these pilots also self-fuel, also with rarely an issue. It amazes me that so many others seem clueless on what has been common practice for 40+ years. Thank you Ben for providing your wisdom, once again. Some people take longer for information to sink in, it seems. BTW – at least here in North Carolina, our state refunds every penny of state highway taxes when we buy auto fuel for our airplanes, an added plus in addition to its relatively low cost. Pure-gas.org shows tens of thousands of sellers of lead-free, ethanol-free gasoline, aka mogas.
Like currently, I prefer to just fly and land wherever for avgas. Not interested in researching, STCs, having to go out of route.
And there isn’t a mogas STC for Mooney the last I’ve heard, vapor lock issues.
I believe that you are correct on the Mooney, one of very few legacy piston singles for which an STC does not exist, yet. My understand is that the problem is the fuel pump, Todd Petersen would know best. No one has every claimed that Mogas is a drop-in replacement for 100% of all piston planes. But it would cover over 70% of all legacy singles and nearly all of the new generations of aircraft powered by a Rotax and similar modern engines. And it would cost less, be far more available than any boutique aviation fuel, etc. The thing is, aircraft owners are going to buy it at gas stations and fuel terminals, pay no money into the aviation funding system, and probably avoid buying Avgas from public airports. I am planning to create my own airstrip on nearby farmland and install my own fuel tank – for only mogas, of course. Small fuel distributors abound who are happy to bring me 1000 gallons during their rounds.
The problem with MoGas is that even with E-0 Mogas, you don’t know what else is in the fuel. I ran MoGas in my planes for years. When I retired and moved to a different area of the country, I found that every gas station in my new area carried Ethanol Free Mogas. Wonderful… or so I thought. Soon after, I walked into the hangar one day to find both tanks leaking in one of my planes with fuel running down the sides of the fuselage and dripping on the hangar floor. The composite tanks in my plane had completely delaminated. I had tested each station for alcohol content and tested the fuel I drained from the plane. None-found. But they are now adding some sort of cleaner to the fuel that destroyed my composite tanks requiring the removal of the wings and a major rebuild. While I detest all the damage being done to valves and valve guide in my engines by using 100LL, I seem to be stuck with it until such time as the feds will get off their butts and allow/promote distribution of an unleaded or low lead fuel. 100LL is Low Lead in name only.
Let the buyer beware – buy ethanol-free fuel only from named brands and the highest AKI rating possible. Test for ethanol, which is easy. Petersen sells small test jars, or you can make your own from an olive jar. Best is to have a fuel company deliver ethanol-free fuel straight to your airfield. Ethanol may not be pumped through fuel pipelines, therefore every fuel terminal has high-octane ethanol free by definition. Bad Avgas is also a problem at airports, for instance when fuel systems are not maintained correctly. Or when a line boy puts Jet-A into a piston plane with a turbocharger, a somewhat common problem years ago. We’ve certainly all gotten water in our 100LL too, and good pilots check this before flying. The horrible ethanol quotas, part of the terrible EISA 2007, should be repealed forever. Nevertheless, the number of gas stations selling E0 is huge and continues to rise. Sellers that do not sell what they advertise face the prospect of far more lawsuits from boat owners with their composite fuel tanks than from the relatively small aviation community. Interestingly, E0 mogas is available at most GA airfields I visit when travelling in Europe. The world’s largest maker of aircraft engines, Rotax, certifies all their engines up to E10 mogas, E0 being their recommended fuel. What is wrong with us in the US?
Perhaps approving a lead substitute additive for the orphans. Or like vintage cars, upgrade their valve system to be compatible. Of course being aviation that will make a mountain out of a molehill.
Certainly ASTM should be the standard.
Imagine ConocoPhillips, Texaco, Shell and every other brand having authority complicating fuel availability and design and STCs. What worked for cars works for aircraft.