Originally published at: https://avweb.com/aviation-news/swift-100r-unleaded-fuel-clears-astm/
Unleaded aviation fuel takes step closer to broader adoption
- This fuel cannot be combined with G100UL without (apparently) risking damage due to how the octane-enhancing ingredients interact (they can each be combined with 100LL). That sounds like a recipe for disaster.
- STC process? Really? How did this become the norm? How is it that different blends of 100LL can be marketed without an STC but lead-free avgas can’t? It’s completely impractical to expect facility operators to have a fuel pump and limit its use to people with STCs (which, among other things, would block all Experimental, Light Sport and MOSAIC aircraft, none of which have Type Certificates).
So strange to have a product that is meant to replace 100LL and there has been no engine testing on engines that absolutely have to have high octane fuel. This ASTM Approval does not appear to be approving that this fuel has a 100 octane anti-knock performance. So why is it so important to have the ASTM approval.
The io-360 engine requires a minimum of 100 octane.
Politics. That’s why George braley’s effort is being stifled by everybody who can possibly do it.
Even the EAA has gotten into it, going full behind all the companies that give them lots of money, to approve this fuel. They have all joined ranks and done what they’ve always done, good old boys club that keeps the money where the money is.
My opinion of the EAA dropped to the floor when they put that opinion article written by the ASTM group into the front of their magazine, completely ignoring that there’s any alternative method of getting unleaded fuel for airplanes.
Same stinking politics that oil companies have done all along, earning the reputation that they now have.
“Many more aircraft are expected to be FAA-certified soon,” said D’Acosta.”
It should be easy to add just about all Cessna 172 models to the list since both the carbureted and fuel injected engines for the 172 do not require 100 octane fuel. And, any other airplane that uses the Lyc parallel valve 360 series is similarly qualified. All of this proves nothing toward whether 100R will actually work for high compression engines. As for Swift providing the fuel to “several” flight schools, doesn’t prove much either since most of them probably used the 172 fleet in their schools. Besides, GAMI did the same for its G100UL prior to obtaining their STC and that didn’t reveal any of the issues currently appearing in their attempted rollout to the fleet.
I find it interesting that Swift seems to think their fuel will work in high compression engines when Lyondell/Bassel, who uses a similar ether-based formula, has openly admitted that their formula may not have the sufficient octane rating to suppress detonation under the most severe conditions required for 100LL. Don’t forget that Swift’s 94UL fuel had problems with valve recession in the UND fleet of Cessna 172s that was supposedly approved for its use under all conditions. Has anyone seen an explanation from Swift about that issue? I haven’t. Some engine experts, including GAMI’s George Braly, felt that the fuel lacks the upper octane capacity for severe engine conditions.
Don’t break out the champaign and balloons just yet to celebrate Swift 100R. I’m not saying it won’t work, but coming up with a lead-free (and drop-in) replacement for 100LL is proving harder than the FAA thought. And ASTM “approval” is no magic bullet either.
Two out of three fuel suppliers have a proposed solution. One more is still working on their best option and we have 4+ years remaining before the deadline. Once all the suitors have put their best foot forward, the collective we can make a more informed choice about what formulation will hopefully serve us best.
As a side note, I’m not convinced that big petroleum is the puppet master that many claim. Regardless of which formulation we end up with, big petroleum will still be the supplier of the hydrocarbons that the fuel is made from. They would appear to be in a “can’t lose” position no matter which formulation is chosen. Their sales will not change. They invested nothing in the process. They have no risk if things go sideways. Seems their best play was simply to stay out of it.
The Lycoming IO-360-L2A engine used in the currently manufactured Cessna Skyhawk is approved for 91/96 octane fuel.
When the smaller airports only have one pump, and they make the switch to unleaded fuel? Where are the bigger aircraft going to get fuel, that require leaded gas, in the event of an emergency landing? I’m sure that issue has been well thought thru…
Yes sir, where are the patents so they can talk about what is in the fuel. Based on burned exhaust valves, 100 octane needs either iron or copper as a coolant as dust particles similar to lead to cool exhaust valves. And no one is talking about a non toxic heavy metal to cool exhaust valves. Without patents pending, this process is a waste of time because they will not tell the fuel consituents.
I spoke with Chris D’Acosta (CEO) at OSH for quite a while. The fuel retailers don’t need to “limit the use of the pump” to STC holders any more than they have to limit the use of the Jet-A pump by piston engine aircraft owners. The onus is on the operator, not the retailer. As far as EABs and other aircraft without type certificates, Swift will be offering a full research package for the same $100 price of the STC, which the owner can then use to determine the compatibility and efficacy of the fuel for their aircraft. That said, it’s experimental - if you want to run your airplane on putrified swamp water, it’s up to you. There’s nothing blocking you from using any fuel you want, other than common sense.
The explanation for the valve recession given to me by Chris D’Acosta (CEO) at OSH: when leaded fuel is burned, an extremely thin layer of lead oxide coats the valve seats. This lead oxide layer works as a lubricant, to allow the valve and the valve seat to “slide” together when the valve closes. The problem with 94UL is that without the lead content, this lubrication did not occur, and the valve seats started to wear and recess. Swift was able to duplicate and identify this as the issue.
When they developed 100R, they added a compound that performed the same function: leaving a thin lubricating layer on the valve seat. They have thousands of hours of testing with no valve seat wear detected. More importantly, they then added this compound to some 94UL and performed the testing again - and this time, unlike the previous 94UL test, the valve seat wear did not occur.
He also told me that they have tested 100R against all engines which would be expected to use 100LL including high compression engines, and that it provides adequate detonation margin for all use cases.
The theory that lead lubricates the valve seats has been hotly debated for decades as to whether that is a real thing or not. A properly fit valve does not “slide” into position on the valve seat. Perhaps as the valve guide wears, there may be some misalignment that leads to some sliding, but valves don’t slide in normal operation. Did Mr. D’Acosta happen to mention what magical material they are now using to promote valve “lubrication”? I have heard of some sodium and potassium compounds that were tried in that function, but the tests didn’t seem to produce any useful results.
Interesting that Swift has successfully tested 100R against all engines that are “expected” to need 100 octane. Did he happen to mention where this testing occurred and which engines were involved? Was this real world or test cell operations? Also, did he happen to mention what the upper octane rating is for 100R under severe conditions? One hundred low lead has an upper rating around 140, so it would be good to see it at least that high.
I’m not doubting Mr. D’Acosta’s explanations, but my frustration with all of this “process”, if you will, is that no one - not Swift, Shell, GAMI or even the FAA seems to be providing aircraft owners with the full facts about where we are in achieving a 100LL replacement. I appreciate the need for some secrecy due to proprietary formulas and materials, but we are the ones who will have to bear the expenses when things go wrong. Everyone is saying “trust us”, and yet the problems seem to keep on coming.
I do not appreciate the secrecy. We are not in a position to trust those we do not know and this whole STC process that the vendors want to adopt does not help. Unleaded fuel is not new to aviation. Avgas 80, had a maximum lead content limit. I am told that this was due to the fact that the vendors wanted to be able to use common distribution systems with 100/130 Avgas which had high lead, and the lead in 80 was washout lead from the plumbing. I have no way to validate this. When 80 went away I went with Mogas 80/87 and to date have run approximately 37000 gallons through my engine, on its second run after going about 1000 hours past TBO on the first run and is presently well past tbo and still strong. The engine manufacturers themselves by migrating from lower compression to higher compression engines in the 80s to accommodate 100LL are also involved in the process. But one thing is clear by their response then: If they can take an 80 octane C152 engine and turn it into a 100LL requiring engine, they can do the reverse. We’ve been running unleaded mogas for 70 years in high performance automotive engines without significant problems with minor engine manufacturing changes in the 1970s, why can’t we do the same with aircraft engines?
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