In my January column I wrote that not all 100 octane fuels are the same. Now it has been reported that the 100UL avgas program has been more or less put on hold. The reasons given were technical problems and the change in administrations in Washington.
This begs the questions: “Why did the program go on in the first place?” and “Why would big oil companies put so much money into a program that may not go anywhere?”
The history of 100UL starts in the 1990s when there were several lawsuits brought in several West Coast states. The EPA started to outlaw 100LL, but the FAA stopped that on safety reasons. The compromise was that the FAA would work on a safe way to “get the lead out.” This started a long process of committees working to develop a 100 motor octane unleaded avgas replacement for 100LL.
I attended several of these meetings before retiring and they were interesting. At one of the meeting in Oshkosh, I asked about exhaust valve recession problems with unleaded fuel and the problem of lead bonus, in which leaded fuels offer significantly higher anti-knock properties than unleaded fuels of the same octane.
On the first question both engine manufacturers jumped up and claimed that valve recession was of no concern because they had hardened seats and had not seen any problems with people using unleaded mogas.
On the second question the response was the belief that they were sure that all that was needed to satisfy the entire fleet was a 100 octane unleaded fuel.
The next day I questioned several aircraft engine rebuilders and technical representatives from the engine manufacturers. They all said they had seen numerous cases of valve recession when unleaded mogas was used.
But the program went on, first with numerous candidates. This was narrowed down to five, then three candidates for further evaluation. The final three were two fuels from Swift and one from Shell. Then Swift dropped out and the program stalled.
The question about why an oil company would invest millions in a product that was not approved goes to how big companies operate. I am sure that a manager saw the unleaded fuel debate and figured this has got to be a great opportunity. The logic here is that if 100LL is outlawed, then the company with a qualified 100 unleaded avgas would have a gold mine and the manager would get a big promotion.
The liability question, the valve problem, the possible knock problems, etc., would be of no concern if the company made money. Besides, at the time it sounded like the EPA would outlaw 100LL in the very near future.
But things change and now the future of 100UL is in question. So what will happen next?
I would guess that not much will change nationally in the next two years and maybe six years, depending on the 2020 election. There is a chance that some states will try to outlaw 100LL, but without an approved 100UL product that could be a problem.
However, many state government officials do not let facts and logic enter into their thinking and the legislative process because it slows business down way too much.
A Rotax 912 ULS engine has a 10.8:1 compression ratio, yet premium mogas is the factory recommended fuel. Flight schools regularly get 3500 hours out of these before needing a rebuild.
Irregardless of unleaded fuel use or not, any modification made to an aircraft engine that is not FAA-approved will invalidate the Standard Airworthiness Certificate issued for the aircraft. Even if the ignition timing is retarded, not meeting the Type Certificate Data Sheet stipulations, the term “airworthy ” cannot be applied to the aircraft.
High horse power engines can run successfully on low octane fuel, its all done with ignition timing..Take fore instance a big block Ford pickup engine putting out 315 horse power and burning 87 octane fuel producing all it’s horse power as the factory intended it to, and doing it in a very awesome manner. Its all done with correct timing that’s all. So take for instance installing solid state ignition on your airplane, you can burn any octane fuel within reason with no problem, that’s what solid state ignition does. For a about $3000.00 dollars or so you can have this ignition installed in your airplane, not only will it produce all it’s rated h.p. but will increase all of it’s parameters, that is rate of climb will increase, over all speed will increase also, better fuel burn. less spark plug fouling, on & on.. Solid state ignition will adapt to just about any good fuel regardless of octane and lead content..
Sorry, that is not a solution. Detonation may be reduced somewhat by retarding the spark, but at the cost of reduced horsepower. All the tweaking of timing, fuel injection and engine design cannot overcome the limits imposed by fuel octane ratings. Yes we will have variable timed electronic ignition with detonation sensors but it certainly not for $3000, thats a pipe dream.
I have to agree 100% with you John, when you start altering an engine designed, manufactured and researched to function in a certain manner you can get yourself into serious trouble. It’s very unlike tweaking a car engine and if something goes amiss you can pull over to the side of the road and call AAA.
I can’t make HDS or TLS out of all the ABVS being TOCED about in these RESPNS. LETTUCE talk ENGLS for our DSCUSNS. If someone is TRYN to MPRS me, IM not.
G&N Aircraft (Engine rebuilders) have been using Swift Fuels in their company aircraft for years and have found no problems using it, even in turbocharged Cessna 421’s. The testing is done, the data witnessed by FAA and research analysts, and yet they get beat down by the large oil companies who own politicians and FAA administration puppets. Distributors are timid to try anything different. Sad that Swift has dropped out. The country and General aviation has lost again.
This all seems so very ridiculous. The amount of leaded AvGas produced and consumed is way less than 1% of all gasoline production in the US, yet so much money and effort has, to date, been expended to find a replacement for such a small quantity of fuel. It is time for all to grow a pair and tell the “greenies” to go save a spotted owl!
I like your idea. But sometimes we need to look at the technical issues. And so I’m going to present them as I currently understand them.
Why does 100LL cost so much? The answer is, because of TEL.
Well how much does TEL cost? Not much.
So why the high prices? Because TEL contaminates the fuel system.
The makers of Avgas make x gallons an Avgas production run. Then after making that production run, have to remove the TEL contamination out of the system because it tends to kill catalytic converters.
So not only are we subject to the rise and fall of a barrel of oil, but we are subject to cleanup being added to the cost.
As a result, you can’t just order a tanker full of avgas and have it delivered from the local fuel distributor. It is a bit more complicated.
And what is interesting is, the numbers thrown around are, 20% of the piston based aircraft fleet uses 80% of the Avgas. And it is those engines that won’t work well without TEL.
In addition to all of that, there is only ONE manufacturer of TEL, and it’s in England.
https://www.innospecinc.com/our-markets/octane-additives/octane-additives
There is a mfr of TEL in China, but it looks like they only serve the domestic market.
So if Innospec stops mfg TEL, and is no more 100LL avgas.
EPA estimates that 100LL is responsible for 1/2 of airborne lead emissions in the USA. Would anyone care to argue that breathing lead is good for you? It’s going away and it needs to go away. Auto manufacturers dealt with “valve erosion” and other such issues sometime in the last century, but not by using engines, ignitions, and materials from 1955. Part of the problem is that FAA certification freezes a technology basically forever into the time period in which it was certified. Any now-standard automotive practice (ECUs, fuel injection, knock sensors – the list is long) would cost a fortune to certify and impossible to amortize over the few hundred new engines produced per year. Direct drive engines require making power at low rpm, which in turn demands large cylinders. Large cylinders cannot run with high compression without very high octane fuel. The old template is doomed to be replaced by something along the lines of Rotax. They seem to be making a lot of engines, profitably. There is no reason Lycoming or Continental could not have been doing this 20 years ago, other than the imagination or will to do so.
I seem to remember in the early 1950s you could buy 100octane unleaded gas at any Amoco station, at least in New York and Conn,. It ran cool and clean in the engines of the day, probably overkill as far as octane was concerned, and the occasional tank of leaded gas kept the valves happy. If this technology was available 70 years ago, how come we are having this discussion now? Suspect like everything else, the FAA gets involved and everything goes to hell in a bucket, nothing getting done but many bureaucrats punching their tickets and supposedly earning their pay.
Is there any consideration in looking at MTBE or BTEX ? A lot of the avgas fuel tanks are above ground with dual spill catch pans.
Mark, Ben,
I’d be interested in the process in removing the ethanol from auto gas since I have the STC for mogas but at E0. Can you reply with that ? There is no E0 auto gas available in CA.
There is no method to “remove” ethanol from auto gas that would result in anything that resembled a fuel meeting ASTM D-4814, which is required by your mogas STC.
Back when I was the co-author of the GAfuels blog here, we covered this problem: https://generalaviationnews.com/2011/10/30/washing-ethanol-out-of-mogas-part-ii/
Big oil didn’t push for this…the greenies did…under Obama you saw this nonsense. Not even Europe is working on this…they are going for diesel (Jet-A) for all aircraft. That’s what we should do here…convert the old gas engines to diesels.
So require a $30-$50k dollar investment in every single airplane in the GA fleet? Who’s paying for that? We’re going to force that because our political views don’t permit us to agree with “the greenies?” It’s a far, far better idea to give us a replacement for 100LL *and* push for diesel as the future.
Right—so who will invest $30k or higher for a diesel conversion in a Cessna 150, J3 Cub, Taylorcraft etc, that are worth less than or equal to the conversion?
I fly behind a Franklin 220 and with 10.5 to 1 compression, I would not want to use anything but 100LL. People who have tried to run MOGAS in the big Frank have had unpleasant results. As Ben observed, you can’t expect science or logic to sway the opinions of politicians determined to make policy based on emotions to stay in power.
Ben,
Still using filtered E0 mogas straight from the distributor to my free standing tank at home (as you told us years ago to do) and only thing I notice is slight rise in EGT. Otherwise I can get it way cheaper than avgas, my plane is STC’d for it and my now 2 year old rebuilt engine with latest greatest valves and seats seems fine with it. Unfortunately, Im forced to buy 100ll anytime I am away from home though my 7:1 compression ratio doesnt need the lead boost. I actually feel that we the public have been duped so long on this issue the only way it changes in my lifetime is the loan supplier of TEL goes out of business. Politics and the FAA are after too many other things at this point.
That’s you. But some of us will have to have our engines de-rated if we go to UL, unless that UL gas provides the same effects of TEL. And the engines I fly behind aren’t turbo-charged but they are HiPerf engines (> 230HP in my case).
Sorry, that is not a solution. Detonation may be reduced somewhat by retarding the spark, but at the cost of reduced horsepower. All the tweaking of timing, fuel injection and engine design cannot overcome the limits imposed by fuel octane ratings. Yes we will have variable timed electronic ignition with detonation sensors but it certainly not for $3000, thats a pipe dream.