The uphill battle of unleaded avgas leaves both the main players in the industry and the regulators themselves looking bad—but in a banal kinda way.
I enjoy AVWeb on YT for AV news (really, I just enjoy the humor/personality of Paul Bertorelli lol), here are a few insightful videos that summarize the story:
Didn't they just legalize unleaded avgas very recently? After a multi-decade regulatory review process?
Seems odd that they were so hesitant to legalize it and now that they did, it becomes the only option!
Mostly because the use of lead in fuels is something to avoid at all costs. I know a lot of GA people were VERY happy to hear that they approved G100UL. Leaded fuels aren't just toxic, but they also cause issues with airplanes such as lead fouling.
>> Didn't they just legalize unleaded avgas very recently?
More specifically, I believe they certified that a particular fuel as suitable for use in ALL engines that previously relied on leaded fuel. Until that happened there was a somewhat legit concern about banning leaded fuel. What people are afraid of now is a monopoly on the new fuel leading to higher prices. But there's already a near monopoly on leaded avgas.
It would be really cool if someone developed a new aircraft engine suitable for replacing all the old models and able to run on a wide range of fuels (this may actually exist). But even then its a slog to get that engine certified for all the planes you'd want to use it on.
> What people are afraid of now is a monopoly on the new fuel leading to higher prices
If you can afford private aviation, the price of the fuel is not going to be a big concern. It's already $7-10/gallon and that is a pretty small component in the all-in hourly costs of operating an aircraft.
> It would be really cool if someone developed a new aircraft engine suitable for replacing all the old models and able to run on a wide range of fuels
As a recent article here talked about, nobody is making new aircraft for general aviation. Or at least, nobody is making anything innovative for it.
But there exist plenty of engines that are good enough for planes and can run on a wide range of fuels. They are just not getting into GA planes.
The problem is that they won't approve engines for general aviation that use unleaded gas. All the engines used in general aviation are basically 60 year old designs. General aviation is not a major concern for the FAA. It's an afterthought. And so they don't devote any time to approving new, modern engines and make it as difficult as possible.
Many, or even most, of the engines are indeed old designs. But e.g. Rotax offers certified version of some of its 900 series engines, which are a relatively new design, some with fuel injection, FADEC, etc.
The FAA legalized unleaded avgas recently, yes. The EPA (the agency this article is about) was waiting for a legal alternative before banning leaded avgas. Since the EPA can't authorize a fuel for use in aviation (that's the FAA's jurisdiction) they had no choice but to wait on the FAA approval. Since the EPA can now ban the leaded fuel.
Availability of the new unleaded fuel is extremely limited. It is also very expensive. I also believe there may be a fee involved per airplane to use it (one time for an STC). The fee I heard is nominal $250.
I have never flown to an airport with it yet. i have probably landed in over a dozen different airports in the last few months with a leaded gas engined plane.
The problem is, "legalizing" it is like 0.1% of the work. The hard part is all the testing/certification you have to do for every single aircraft and engine design.
> The FAA signed on September 1 supplemental type certificates that allow General Aviation Modifications Inc.’s 100-octane unleaded fuel (G100UL) to be used in every general aviation spark-ignition engine and every airframe powered by those engines.
All piston engines and aircraft are certified for G100UL.
It’s actually very easy if you are the government; you just say from 5 years from now, using lead fuel is banned. And then someone else has to do the work.
Dick move to ban am additive that we've known for over a century has terrible toxic affects on people and the environment from a machine that would release it into the air? Maybe there isn't an alternative, but maybe it doesn't matter?
Glad to hear, it should have been phased out a long time ago. Assuming there aren't any issues with the only very recently legalized unleaded avgas I don't think there are any downsides.
TEL is incredibly bad stuff*, but it's rarely used in commercial flight operations as they predominantly use jet aircraft. Leaded avgas is completely unnecessary as non-TEL fuel formulations have been created and certified. The problem is they're not available anywhere, while leaded avgas is everywhere in GA. Municipalities should do like they did for leaded automotive gasoline: supersede commercial interests with public health regulatory ones and ban it. (The EPA only banned leaded automotive gasoline nationwide in 1996 after allowing 25 years for the phaseout.)
* In the same category of human harm as nerve agents, dioxin, and methylmercury.
The first general purpose non-TEL alternative was only certified last year. Before that, each variant had to be certified per-type, and then would need to be stocked everywhere. Which never was going to happen, and didn't.
Now they're going to ban leaded avgas, which should force the for adoption, since there IS now an approved general purpose alternative.
It’ll probably take another 10-20 years to outright ban it. Though the EPA might make it illegal to manufacture any engines that use leaded gas far sooner than that.
Now that there is an unleaded alternative, older planes will slowly replace their engines at the next engine rebuild. There is a grave pilot shortage already and the FAA loathes to make GA even more inaccessible than it already is so it’ll be a slow process.
>Will I have to modify my engine or aircraft to use G100UL avgas?
>Other than placards, no modifications are required. A small placard is attached to the engine and "stick-on" placards are applied to refueling ports. In addition, there is a short POH supplement added to the AFMS.
The engine change is shit pushed by the leaded-gas manufacturing lobby.
> There is a grave pilot shortage already and the FAA loathes to make GA even more inaccessible than it already is
Lol, inaccessible? Y'all don't even need airstrips to take on and off, for Part 103 ultralights technically not even a license. Meanwhile, here in Germany, first pay up thousands of euros for the ultralight cert, and you have to use dedicated airstrips instead of your farm's field. Oh and if you want to get beyond ultralight, do everything from scratch for the PPL, no credit/transfers.
There's also distribution problems. Jet fuel aside, most airports only have one tank for servicing avgas. Once they switch over to non-leaded, now they have a customer base that may not be able to buy from them. Those revenues go to fund the airport operation.
There's going to have to be a concerted effort to fix type certificates and fuel distribution all at the same time. A slow effort is going to be more problematic.
> older planes will slowly replace their engines at the next engine rebuild
An alternative exists, but the FAA needs to certify it for each aircraft type. The majority of aircraft types are not certified for this. No A&P is going to do this because the plane won't be legal to fly in most cases.
And at the risk of editorializing, I've never seen the FAA do anything with the goal to making GA more accessible, at least not intentionally.
Cruise just needs to move to flying airplanes. With all the anti-GA and anti-airport astroturfers there will be no one to fly them for their vacations.
People just can't see the end result of their ideologies.
Why are diesels so uncommon among piston aircraft, it's almost always avgas? Is it just "because that's how it's always been" or are there actual engineering reasons diesel are inferior? Cursory searching suggests it's mostly this inertia.
It'd be especially useful if they could run on regular jet fuel, then turboprops/jets and pistons could use the same fuel infra.
Diesel engines operate at higher pressures and must be considerably heavier to achieve the same performance & efficiency. Not a huge issue for ships, trains, or cars. Huge issue for flying stuff.
As the sibling comments have pointed out, power-to-weight is the main reason, but it doesn't make diesel engines completely unfeasible for light aircraft.
Diamond Aircraft have had success selling planes with diesel engines recently, and even started a subsidiary company to manufacture them: https://en.wikipedia.org/wiki/Austro_Engine
As others mentioned, diesels tend to have worse performance/weight due to heavier construction.
In the early days of aviation (like 1930's or such) there was some effort to introduce diesels for long-range aircraft, the idea being that the heavier powerplant would be offset by the lower required fuel load due to better fuel economy. But they weren't successful.
More recently there has been something of a renewed interest in aviation diesel engines, the motivation being they can run on Jet A-1 in addition to diesel fuel. Jet A-1 is what jet (and turboprop) aircraft use, and is available at basically every airport worldwide, is much cheaper than avgas, and no risk of being phased out like the leaded avgas being discussed in this article.
So I know absolutely nothing about chemistry, so can someone explain to me why lead was added to gasoline in the first place? Disregarding its toxicity, what benefit does lead buy you?
> It is a fuel additive, first being mixed with gasoline beginning in the 1920s as a patented octane rating booster that allowed engine compression to be raised substantially. This in turn increased vehicle performance and fuel economy.
If you want a fascinating story telling video with a lot of sciency stuff for the relative layman, here's an excellent one by Veritasium on how it happened.
"The Man Who Accidentally Killed The Most People In History"
https://en.m.wikipedia.org/wiki/Thomas_Midgley_Jr. He was a fascinating man, relatively non-famous. Probably singlehandedly contributed to more environmental damage than you can imagine. Died in a strange way too.
My understanding (and I'm no authority in this subject) is that adding lead to gasoline allows achieving better octane ratings (ie lower chance of self-ignition). This reduces engine knock, which makes the engine live longer, also allows pushing more fuel into a cylinder per ignition cycle more confidently.
These things are possible without lead as well, it just costs more money to do so.
It's about increasing the compression ratio without self-ignition. High compression ratios mean higher power for the same weight, and airplanes are all about minimizing weight. You also get higher efficiency. Again, lower fuel weight = good.
You can dump as much fuel in the cylinder as you want (in fact, most airplane operating handbooks call for a very rich mixture on takeoff because of the cooling effect).
Half the story is the lead acts as a octane booster, but raising the octane without lead chemicals is trivial. MTBE works, so does just selling pure toluene. The issue is that in addition to raising the octane, some metal lead deposits around the valves which maybe makes them seal better and switching away from lead could cause engine failures unrelated to octane.
It allows the fuel to withstand higher pressures without detonating in an uncontrolled manner. This is important in aircraft engines, which run at a significant fraction of their maximum power output for most of their working lives.
People have been looking for alternatives for a long time, but it's difficult because leaded aviation gasoline is not a very large market, and there are substantial regulatory obstacles.
So higher octane means it needs higher temp/ pressure to burn? I've completely misunderstood octane my whole life.. i always thought it meant "high octane make engine brrrrrr fast"
Waiting for the Tesla of the aviation as that lead vs. unleaded feel like something ancient.
Lets look at numbers as of today:
Cesna 172 - 75kw engine, on 50kw power makes 1000km as 200km/hr. Engine plus fuel weight 350kg. The engine costs $26K.
Today's lithium batteries like ones used by Tesla is 280wh/kg. At retail similar batteries cost $400/kwh.
So, we can have 75kw electric engine and 100kwh battery at the same weight as ICE engine plus fuel on Cesna 172 and at a retail cost of $50K and have 2 hr flight of 400km. That isn't a worse starting point than what Tesla had 15 years ago against ICE cars.
Readit News
I enjoy AVWeb on YT for AV news (really, I just enjoy the humor/personality of Paul Bertorelli lol), here are a few insightful videos that summarize the story:
The Long, Twisted And Slightly Ridiculous Story of Avgas Part 1 (14:22) https://www.youtube.com/watch?v=9F-WngVMJBQ
Part 2 (15:15) https://www.youtube.com/watch?v=Mvse4Xhzwuk
and
G100UL Approved Now What? (When the FAA approved the first unleaded 100-octane avgas a year ago) https://www.youtube.com/watch?v=ibIkuyBL9i8
It's not odd, it's exactly what you'd expect. The only odd thing is that it took this long.
Many (older) aircraft engines need leaded fuel.
AVWeb did a couple videos on the subject here:
https://youtu.be/9F-WngVMJBQ?si=Qb_IYu4QwZlOTDCv
https://youtu.be/ovJBJjZTjsk?si=f2OwwZMmuEUTx6wL
More specifically, I believe they certified that a particular fuel as suitable for use in ALL engines that previously relied on leaded fuel. Until that happened there was a somewhat legit concern about banning leaded fuel. What people are afraid of now is a monopoly on the new fuel leading to higher prices. But there's already a near monopoly on leaded avgas.
It would be really cool if someone developed a new aircraft engine suitable for replacing all the old models and able to run on a wide range of fuels (this may actually exist). But even then its a slog to get that engine certified for all the planes you'd want to use it on.
If you can afford private aviation, the price of the fuel is not going to be a big concern. It's already $7-10/gallon and that is a pretty small component in the all-in hourly costs of operating an aircraft.
As a recent article here talked about, nobody is making new aircraft for general aviation. Or at least, nobody is making anything innovative for it.
But there exist plenty of engines that are good enough for planes and can run on a wide range of fuels. They are just not getting into GA planes.
Except that they did approve a lead-free fuel for use in all those engines last year. Banning leaded fuel is the obvious next step.
I have never flown to an airport with it yet. i have probably landed in over a dozen different airports in the last few months with a leaded gas engined plane.
What is $250 in aviation terms? It's nothing.
Availability of fuel is a concern, sure. But a fire has to be lit on people's ass, otherwise they will not move.
> The FAA signed on September 1 supplemental type certificates that allow General Aviation Modifications Inc.’s 100-octane unleaded fuel (G100UL) to be used in every general aviation spark-ignition engine and every airframe powered by those engines.
All piston engines and aircraft are certified for G100UL.
There is now a legal alternative. Working as intended.
Edit, looks like there is an alternative https://news.ycombinator.com/item?id=38040091
* In the same category of human harm as nerve agents, dioxin, and methylmercury.
https://www.aopa.org/news-and-media/all-news/2021/july/27/ga...
https://www.epa.gov/archive/epa/aboutepa/epa-takes-final-ste...
Now they're going to ban leaded avgas, which should force the for adoption, since there IS now an approved general purpose alternative.
Now that there is an unleaded alternative, older planes will slowly replace their engines at the next engine rebuild. There is a grave pilot shortage already and the FAA loathes to make GA even more inaccessible than it already is so it’ll be a slow process.
It is fully compatible with existing engines https://www.g100ul.com/
>Will I have to modify my engine or aircraft to use G100UL avgas?
>Other than placards, no modifications are required. A small placard is attached to the engine and "stick-on" placards are applied to refueling ports. In addition, there is a short POH supplement added to the AFMS.
The engine change is shit pushed by the leaded-gas manufacturing lobby.
Lol, inaccessible? Y'all don't even need airstrips to take on and off, for Part 103 ultralights technically not even a license. Meanwhile, here in Germany, first pay up thousands of euros for the ultralight cert, and you have to use dedicated airstrips instead of your farm's field. Oh and if you want to get beyond ultralight, do everything from scratch for the PPL, no credit/transfers.
There's going to have to be a concerted effort to fix type certificates and fuel distribution all at the same time. A slow effort is going to be more problematic.
An alternative exists, but the FAA needs to certify it for each aircraft type. The majority of aircraft types are not certified for this. No A&P is going to do this because the plane won't be legal to fly in most cases.
And at the risk of editorializing, I've never seen the FAA do anything with the goal to making GA more accessible, at least not intentionally.
People just can't see the end result of their ideologies.
It'd be especially useful if they could run on regular jet fuel, then turboprops/jets and pistons could use the same fuel infra.
Diamond Aircraft have had success selling planes with diesel engines recently, and even started a subsidiary company to manufacture them: https://en.wikipedia.org/wiki/Austro_Engine
In the early days of aviation (like 1930's or such) there was some effort to introduce diesels for long-range aircraft, the idea being that the heavier powerplant would be offset by the lower required fuel load due to better fuel economy. But they weren't successful.
More recently there has been something of a renewed interest in aviation diesel engines, the motivation being they can run on Jet A-1 in addition to diesel fuel. Jet A-1 is what jet (and turboprop) aircraft use, and is available at basically every airport worldwide, is much cheaper than avgas, and no risk of being phased out like the leaded avgas being discussed in this article.
> It is a fuel additive, first being mixed with gasoline beginning in the 1920s as a patented octane rating booster that allowed engine compression to be raised substantially. This in turn increased vehicle performance and fuel economy.
"The Man Who Accidentally Killed The Most People In History"
https://www.youtube.com/watch?v=IV3dnLzthDA
These things are possible without lead as well, it just costs more money to do so.
You can dump as much fuel in the cylinder as you want (in fact, most airplane operating handbooks call for a very rich mixture on takeoff because of the cooling effect).
People have been looking for alternatives for a long time, but it's difficult because leaded aviation gasoline is not a very large market, and there are substantial regulatory obstacles.
(In comparison, it was well-known at the time that ethanol can also increase octane, and it wasn't protected by patents.)
Lets look at numbers as of today:
Cesna 172 - 75kw engine, on 50kw power makes 1000km as 200km/hr. Engine plus fuel weight 350kg. The engine costs $26K.
Today's lithium batteries like ones used by Tesla is 280wh/kg. At retail similar batteries cost $400/kwh.
So, we can have 75kw electric engine and 100kwh battery at the same weight as ICE engine plus fuel on Cesna 172 and at a retail cost of $50K and have 2 hr flight of 400km. That isn't a worse starting point than what Tesla had 15 years ago against ICE cars.