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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 a

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!

Kapura 3y ago
The only odd part is that it took so long. Leaded gasoline has been known to be toxic for many, many decades.
crazygringo 3y ago
Or it makes perfect sense. Once it's legal, what reason is there to keep the poisonous one around? It's not odd, it's exactly what you'd expect. The only odd thing is that it took this long.
- TinyRick 3y ago
  > Once it's legal, what reason is there to keep the poisonous one around? Many (older) aircraft engines need leaded fuel.
  - kevan 3y ago
    I remember news saying the FAA added supplemental type certs allowing G100UL for basically every engine in 2022. What gaps are there?
    - sokoloff 3y ago
      Distribution. https://www.g100ul.com/faq.html#availability https://www.g100ul.com/faq.html#availability
  - mlyle 3y ago
    As far as we know, G100UL works in anything.
    - labcomputer 3y ago
      Yes, but it's not currently legal to use in anything. You still have to apply for and buy an STC for your specific airframe's serial number and engine's serial number. Then you have to add some paperwork to the logbook and POH and add placards to the fuel fillers and cockpit. In theory you should be able to automatically get it for anything which was approved from the factory to use 100LL, but the STC application form (here: https://stc.g100ul.com/aircraft/ https://stc.g100ul.com/aircraft/) does not allow you to select most mid-century large radials (which were usually originally certified on 130) or the airplanes they were installed on. To be clear, this is a great thing, but you can't legally just fill G100UL in any random airplane.
      - briandear 3y ago
        Exactly. Remove the STC requirement. If the fuel is unreliable that it won’t work in every 100LL aircraft, then it shouldn’t be forced upon us. If it is completely safe, then an STC should be unnecessary.
        mlyle 3y ago
        What about something in-between? The fuel is reliable in almost every design, but there's some design out there that -relies- upon lead depositing to engine surfaces to be reliable (as opposed to the octane effect). I don't think it needs to work in every conceivable 100LL aircraft: just almost all. Every is a high bar.
        lazide 3y ago
        Which is why it is taking so long. Because if an engine grenades on takeoff, it's almost guaranteed to kill someone. If that was because of the fuel switch, that's a real problem.
        tass 3y ago
        You can’t realistically support both leaded and unleaded avgas, and this is why adoption is so low. Airports don’t always have the space for a second avgas tank (if this is the in between option), and if they did don’t necessarily want to spend money on setting up that infrastructure. So the current catch-all is to provide leaded which is cheaper and guaranteed to work in everything. I think it’s great we are getting this forced through - it will make the approval process streamlined (like loda was) and removes a major reason people used to push airport shutdowns.
  - tastyfreeze 3y ago
    Can't upvote this enough. This is going to kill small operators that might not be able to comply. Why not just let the leaded fuel users die from attrition naturally?
    - aaomidi 3y ago
      Because lead is not safe? Like small planes are spewing lead over everywhere they’re flying. I’m glad this is happening. I don’t really care about small operators vs the health of everyone else, and especially kids in the case of lead.
    - munk-a 3y ago
      Considering we're talking about leaded fuel that is some terrible wording.
      - aaomidi 3y ago
        I know right? Operating a plane is a privilege, not a right.
        lazide 3y ago
        So, apparently, is operating a motor vehicle. Except large swathes of the economy will collapse without them. Oh, we aren't talking about tire dust? Never mind.
        eesmith 3y ago
        Then let's talk about it. Unlike lead, we've only recently had the technology to measure and quantify tire wear pollution. For example, we didn't realize until 2020 that 6PPD - already toxic to many aquatic organisms - can oxidize become 6PPD-quinone, which is acutely toxic to coho salmon and some other fish species. This solved a 20 year old mystery of so many coho salmon died after a rain storm. That's why the California Environmental Protection Agency has passed a rule requiring tire makers to declare an alternative by 2024. https://dtsc.ca.gov/scp/motor_vehicle_tires_containing_6ppd/ https://dtsc.ca.gov/scp/motor_vehicle_tires_containing_6ppd/ That's in addition to the particulate pollution from tire wear. ("Research from Emissions Analytics shows that particulate mass emissions from tire wear is thousands of times greater than those from tailpipes, which have been vastly reduced in recent years by high-efficiency exhaust filters." - https://edition.cnn.com/2022/08/16/world/tyre-collective-microplastic-rubber-waste-climate-hnk-spc-intl/index.html https://edition.cnn.com/2022/08/16/world/tyre-collective-mic... ). We of course need to regulate them better because electric cars are heavier, so tire particulate pollution is expected to increase over the next few years. There's also brake pad pollution, like the EPA's Copper-Free Brake Initiative to remove copper, "mercury, lead, cadmium, asbestiform fibers, and chromium-six salts in motor vehicle brake pads." https://www.epa.gov/npdes/copper-free-brake-initiative https://www.epa.gov/npdes/copper-free-brake-initiative . That's a voluntary program, but California and Washington have mandatory requirements. I trust that you support these efforts to reduce car pollution, and are not simply using the lack of discussion about them in this thread in order to score internet points for implied hypocrisy? Both tires and brakes have the advantage that they are replaced every few years/decade, so regulations can target manufacturers. An aircraft engine can have decades of life, so any costs of switching away from leaded fuel are felt directly by the owner.
  - dontlaugh 3y ago
    Any petrol engine can run on 100 RON fuel. There are several options that involve no lead, generally substituting with ethanol.
    - labcomputer 3y ago
      Sure, and any petrol engine can run on 78 RON fuel to. It's just that if you try to run it at full power you'll blow it up. Wee bit of a problem on takeoff. Same thing with running certain large piston airplane engines on 100. They blow up. > There are several options that involve no lead, generally substituting with ethanol Ethanol is corrosive to aluminum. Thankfully airplane designers have never used aluminum in airplanes...
    - mchid 3y ago
      We can't use ethanol because of phase separation amongst other reasons but this is true considering we've been using stuff like toluene probably even longer than tel.
  - kube-system 3y ago
    They don't "need" lead any more than pre-70s cars "need" lead. They were designed to run on leaded fuel, but there are lead replacement additives which are able to fulfill the same technical requirements. TEL is just cheap, effective, and well understood for legacy applications. It isn't the only option to boost octane, by far.
    - roflchoppa 3y ago
      The only issue I had on my 240z was the valve seats were some super soft brass like material, those needed to be swapped as they were beat to up and did not seal. The 75+ heads, all have steel seats. I’ve actually never experienced the, “California gas sucks” issue that car people from the mid-west talk about, have never had an issue with it. ¯\_(ツ)_/¯
      - mcronce 3y ago
        Maybe my understanding is incomplete, but AFAIK the "California gas sucks" thing is just because the highest grade you can find at most pumps there is 91, while we get 93 in a lot of other states Not that it matters when everything made for "premium" is tuned for 91 from the factory anyway, not 93
        arcticbull 3y ago
        California actually has different gas that produces fewer emissions - it's part of the reason gas is more expensive here. It's called CARBOB grade, c.f. RBOB/CBOB.
        dicknuckle 3y ago
        Today I learned, thanks!
        mcronce 3y ago
        TIL, thanks for the info
        3y ago
  - lfuller 3y ago
    G100UL, the current unleaded alternative to 100LL, has been tested to act as a drop-in replacement for any and all aircraft engines that run on 100LL. If you can run, 100LL, you can run G100UL. The main issue is with mogas (standard car gas) - many aviation engines can't run it.
    - jacquesm 3y ago
      Is that due to the Ethanol fraction or some other factor?
      - i386 3y ago
        From memory octane levels have a huge bearing on engine performance and that affects take off distance. Aviation has had a much higher octane rating than your typical car gas.
      - ctennis1 3y ago
        A myriad of things: Octane, ethanol, and also additives used in the winter vs the summer.
      - labcomputer 3y ago
        That's part of it. Ethanol is incompatible with materials commonly found in airplane fuel systems. Another aspect is that many piston airplane engines need high octane because they have relatively high compression ratios: WWII era engines need 130 octane to develop full horsepower (they can be operated at reduced manifold pressure on currently available 100 low-lead gas), and even many post-war civilian engines require 100 octane. Still another aspect is that the FAA is relatively conservative and doesn't want to approve something that might lead to, for example, vapor lock or fuel freezing issues.
        mrguyorama 3y ago
        >airplane engines need high octane because they have relatively high compression ratios: WWII era engines need 130 octane to develop full horsepower I mean, high octane and compression relative to other 1960s engines. The common engines in nearly any single prop cessna have about a 9:1 compression ratio, which was massive back when it was built, but laughably bad compared to anything manufactured after the advent of Fuel injection and better piston geometry. Modern cars regularly have over 12-1 compression ratios on 87 octane. 1960s era carbs and top ends were just abysmal and did a terrible job of mixing the fuel and air charge and controlling the flame front, because we just didn't have the kinds of computer controls and fluid dynamic simulations we have now, to dynamically prevent knock. Rotax engines are modern and can reach identical performance figures or better, with the same weight or lighter, simply by using modern techniques like fuel injection or a small turbocharger. They do this while running on 91 octane
  - heelix 3y ago
    The beauty of G100UL is you just need an STC - just paperwork - to be legal with GA aircraft. All gasoline powered aircraft and engines in the FAA’s type certificate database are covered by the STC for G100UL... which is amazing. I'll be doing it, as soon as our home base carries it for my 56 o200.
  - mchid 3y ago
    They literally don't when G100UL exist, which is approved as a full drop in replacement safe for all engines.
foxyv 3y ago
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. AVWeb did a couple videos on the subject here: https://youtu.be/9F-WngVMJBQ?si=Qb_IYu4QwZlOTDCv https://youtu.be/9F-WngVMJBQ?si=Qb_IYu4QwZlOTDCv https://youtu.be/ovJBJjZTjsk?si=f2OwwZMmuEUTx6wL https://youtu.be/ovJBJjZTjsk?si=f2OwwZMmuEUTx6wL
codexb 3y ago
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.
- phkahler 3y ago
  >> The problem is that they won't approve engines for general aviation that use unleaded gas. 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.
- jabl 3y ago
  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.
phkahler 3y ago
>> 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.
- marcosdumay 3y ago
  > 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.
  - SoftTalker 3y ago
    There is some interesting stuff happening in battery-electric aircraft as trainiers. You can only fly them about 45 minutes and within a local radius of the airport but they are good for people learning the stick-and-rudder basics of flying.
    - MrDrMcCoy 3y ago
      Gliders are even better for learning flight basics, do a better job of teaching you to anticipate and work with turbulence, and have a variable time limit.
      - lazide 3y ago
        Glider hours aren't going to count towards any useful type certification though? Unless you think someone is going to be qualified on a Twin Otter because of 1000 glider hours?
SomeHacker44 3y ago
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.
- outworlder 3y ago
  > 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. 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.
- scarby2 3y ago
  the requirement for the STC on a per-aircraft basis is now gone AFAIK. That was the effect of the FAA's "legalization" last year.
  - sokoloff 3y ago
    You still have to purchase the STC for your airplane serial number and engine(s) serial number. What the FAA did was approve that all-model STC as being valid/legal to sell and "install" (which is just placards).
TylerE 3y ago
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.
- tinus_hn 3y ago
  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.
- FireBeyond 3y ago
  Except... certification is done: https://www.aopa.org/news-and-media/all-news/2022/september/01/closer-to-an-unleaded-future https://www.aopa.org/news-and-media/all-news/2022/september/... > 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.
lazide 3y ago
It's a pretty dick move to ban something a large portion of the aviation community needs when there is literally no legal alternative no? There is now a legal alternative. Working as intended.
- TSiege 3y ago
  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? Edit, looks like there is an alternative https://news.ycombinator.com/item?id=38040091 https://news.ycombinator.com/item?id=38040091
  - lazide 3y ago
    The amount of lead taken up from leaded avgas in the community is so close to zero (compared to other sources) that it hasn't outweighed the damage done by essentially banning general aviation. Which is what banning leaded avgas would do without an alternative. It's already nearly choked to death by regulation, but that was a step too far. But they also clearly have been working to mitigate it, and now that they have an alternate are banning leaded avgas and launching it. So what is your rant about exactly?
    - dicknuckle 3y ago
      You're going to need to provide a source for "the amount of lead taken up from leaded avgas in the community is close to zero" otherwise it's FUD.
      - lazide 3y ago
        https://www.mayoclinic.org/diseases-conditions/lead-poisoning/symptoms-causes/syc-20354717# https://www.mayoclinic.org/diseases-conditions/lead-poisonin... Do you even see it in the list? This NIH study shows it as ‘small, but significant’ - accounting for anywhere from 2.1-4.4% of the lead found in children’s blood near piston airports. https://ehp.niehs.nih.gov/doi/10.1289/ehp.1003231 https://ehp.niehs.nih.gov/doi/10.1289/ehp.1003231 Less than 5% of the amount of lead total in their blood from that source, literally for the highest risk segment you can find. Even if completely eliminated, the other 95% isn’t going anywhere. Even if you don’t average it out across the population, it’s hard to argue that isn’t so close to zero that nearly any significant benefit anywhere else would make it not a rush. Most airborne lead pollution now is industrial anyway, and that is clearly the calculus there. As is the #1 and #2 sources of lead ingestion for children, old paint and old pipes. I’m glad they’re getting rid of it, but I’m not going to complain they didn’t drop everything to rush it. Especially since if they did, they’d almost certainly kill more people in the resulting plane crashes.
mulmen 3y ago
The FAA recently approved unleaded avgas. The EPA never had a problem with unleaded gas.
SAI_Peregrinus 3y ago
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.

Kapura 3y ago

The only odd part is that it took so long. Leaded gasoline has been known to be toxic for many, many decades.

crazygringo 3y ago

Or it makes perfect sense. Once it's legal, what reason is there to keep the poisonous one around? It's not odd, it's exactly what you'd expect. The only odd thing is that it took this long.

TinyRick 3y ago
> Once it's legal, what reason is there to keep the poisonous one around? Many (older) aircraft engines need leaded fuel.
- kevan 3y ago
  I remember news saying the FAA added supplemental type certs allowing G100UL for basically every engine in 2022. What gaps are there?
  - sokoloff 3y ago
    Distribution. https://www.g100ul.com/faq.html#availability https://www.g100ul.com/faq.html#availability
- mlyle 3y ago
  As far as we know, G100UL works in anything.
  - labcomputer 3y ago
    Yes, but it's not currently legal to use in anything. You still have to apply for and buy an STC for your specific airframe's serial number and engine's serial number. Then you have to add some paperwork to the logbook and POH and add placards to the fuel fillers and cockpit. In theory you should be able to automatically get it for anything which was approved from the factory to use 100LL, but the STC application form (here: https://stc.g100ul.com/aircraft/ https://stc.g100ul.com/aircraft/) does not allow you to select most mid-century large radials (which were usually originally certified on 130) or the airplanes they were installed on. To be clear, this is a great thing, but you can't legally just fill G100UL in any random airplane.
    - briandear 3y ago
      Exactly. Remove the STC requirement. If the fuel is unreliable that it won’t work in every 100LL aircraft, then it shouldn’t be forced upon us. If it is completely safe, then an STC should be unnecessary.
      - mlyle 3y ago
        What about something in-between? The fuel is reliable in almost every design, but there's some design out there that -relies- upon lead depositing to engine surfaces to be reliable (as opposed to the octane effect). I don't think it needs to work in every conceivable 100LL aircraft: just almost all. Every is a high bar.
        lazide 3y ago
        Which is why it is taking so long. Because if an engine grenades on takeoff, it's almost guaranteed to kill someone. If that was because of the fuel switch, that's a real problem.
        tass 3y ago
        You can’t realistically support both leaded and unleaded avgas, and this is why adoption is so low. Airports don’t always have the space for a second avgas tank (if this is the in between option), and if they did don’t necessarily want to spend money on setting up that infrastructure. So the current catch-all is to provide leaded which is cheaper and guaranteed to work in everything. I think it’s great we are getting this forced through - it will make the approval process streamlined (like loda was) and removes a major reason people used to push airport shutdowns.
- tastyfreeze 3y ago
  Can't upvote this enough. This is going to kill small operators that might not be able to comply. Why not just let the leaded fuel users die from attrition naturally?
  - aaomidi 3y ago
    Because lead is not safe? Like small planes are spewing lead over everywhere they’re flying. I’m glad this is happening. I don’t really care about small operators vs the health of everyone else, and especially kids in the case of lead.
  - munk-a 3y ago
    Considering we're talking about leaded fuel that is some terrible wording.
    - aaomidi 3y ago
      I know right? Operating a plane is a privilege, not a right.
      - lazide 3y ago
        So, apparently, is operating a motor vehicle. Except large swathes of the economy will collapse without them. Oh, we aren't talking about tire dust? Never mind.
        eesmith 3y ago
        Then let's talk about it. Unlike lead, we've only recently had the technology to measure and quantify tire wear pollution. For example, we didn't realize until 2020 that 6PPD - already toxic to many aquatic organisms - can oxidize become 6PPD-quinone, which is acutely toxic to coho salmon and some other fish species. This solved a 20 year old mystery of so many coho salmon died after a rain storm. That's why the California Environmental Protection Agency has passed a rule requiring tire makers to declare an alternative by 2024. https://dtsc.ca.gov/scp/motor_vehicle_tires_containing_6ppd/ https://dtsc.ca.gov/scp/motor_vehicle_tires_containing_6ppd/ That's in addition to the particulate pollution from tire wear. ("Research from Emissions Analytics shows that particulate mass emissions from tire wear is thousands of times greater than those from tailpipes, which have been vastly reduced in recent years by high-efficiency exhaust filters." - https://edition.cnn.com/2022/08/16/world/tyre-collective-microplastic-rubber-waste-climate-hnk-spc-intl/index.html https://edition.cnn.com/2022/08/16/world/tyre-collective-mic... ). We of course need to regulate them better because electric cars are heavier, so tire particulate pollution is expected to increase over the next few years. There's also brake pad pollution, like the EPA's Copper-Free Brake Initiative to remove copper, "mercury, lead, cadmium, asbestiform fibers, and chromium-six salts in motor vehicle brake pads." https://www.epa.gov/npdes/copper-free-brake-initiative https://www.epa.gov/npdes/copper-free-brake-initiative . That's a voluntary program, but California and Washington have mandatory requirements. I trust that you support these efforts to reduce car pollution, and are not simply using the lack of discussion about them in this thread in order to score internet points for implied hypocrisy? Both tires and brakes have the advantage that they are replaced every few years/decade, so regulations can target manufacturers. An aircraft engine can have decades of life, so any costs of switching away from leaded fuel are felt directly by the owner.
- dontlaugh 3y ago
  Any petrol engine can run on 100 RON fuel. There are several options that involve no lead, generally substituting with ethanol.
  - labcomputer 3y ago
    Sure, and any petrol engine can run on 78 RON fuel to. It's just that if you try to run it at full power you'll blow it up. Wee bit of a problem on takeoff. Same thing with running certain large piston airplane engines on 100. They blow up. > There are several options that involve no lead, generally substituting with ethanol Ethanol is corrosive to aluminum. Thankfully airplane designers have never used aluminum in airplanes...
  - mchid 3y ago
    We can't use ethanol because of phase separation amongst other reasons but this is true considering we've been using stuff like toluene probably even longer than tel.
- kube-system 3y ago
  They don't "need" lead any more than pre-70s cars "need" lead. They were designed to run on leaded fuel, but there are lead replacement additives which are able to fulfill the same technical requirements. TEL is just cheap, effective, and well understood for legacy applications. It isn't the only option to boost octane, by far.
  - roflchoppa 3y ago
    The only issue I had on my 240z was the valve seats were some super soft brass like material, those needed to be swapped as they were beat to up and did not seal. The 75+ heads, all have steel seats. I’ve actually never experienced the, “California gas sucks” issue that car people from the mid-west talk about, have never had an issue with it. ¯\_(ツ)_/¯
    - mcronce 3y ago
      Maybe my understanding is incomplete, but AFAIK the "California gas sucks" thing is just because the highest grade you can find at most pumps there is 91, while we get 93 in a lot of other states Not that it matters when everything made for "premium" is tuned for 91 from the factory anyway, not 93
      - arcticbull 3y ago
        California actually has different gas that produces fewer emissions - it's part of the reason gas is more expensive here. It's called CARBOB grade, c.f. RBOB/CBOB.
        dicknuckle 3y ago
        Today I learned, thanks!
        mcronce 3y ago
        TIL, thanks for the info
      - 3y ago
- lfuller 3y ago
  G100UL, the current unleaded alternative to 100LL, has been tested to act as a drop-in replacement for any and all aircraft engines that run on 100LL. If you can run, 100LL, you can run G100UL. The main issue is with mogas (standard car gas) - many aviation engines can't run it.
  - jacquesm 3y ago
    Is that due to the Ethanol fraction or some other factor?
    - i386 3y ago
      From memory octane levels have a huge bearing on engine performance and that affects take off distance. Aviation has had a much higher octane rating than your typical car gas.
    - ctennis1 3y ago
      A myriad of things: Octane, ethanol, and also additives used in the winter vs the summer.
    - labcomputer 3y ago
      That's part of it. Ethanol is incompatible with materials commonly found in airplane fuel systems. Another aspect is that many piston airplane engines need high octane because they have relatively high compression ratios: WWII era engines need 130 octane to develop full horsepower (they can be operated at reduced manifold pressure on currently available 100 low-lead gas), and even many post-war civilian engines require 100 octane. Still another aspect is that the FAA is relatively conservative and doesn't want to approve something that might lead to, for example, vapor lock or fuel freezing issues.
      - mrguyorama 3y ago
        >airplane engines need high octane because they have relatively high compression ratios: WWII era engines need 130 octane to develop full horsepower I mean, high octane and compression relative to other 1960s engines. The common engines in nearly any single prop cessna have about a 9:1 compression ratio, which was massive back when it was built, but laughably bad compared to anything manufactured after the advent of Fuel injection and better piston geometry. Modern cars regularly have over 12-1 compression ratios on 87 octane. 1960s era carbs and top ends were just abysmal and did a terrible job of mixing the fuel and air charge and controlling the flame front, because we just didn't have the kinds of computer controls and fluid dynamic simulations we have now, to dynamically prevent knock. Rotax engines are modern and can reach identical performance figures or better, with the same weight or lighter, simply by using modern techniques like fuel injection or a small turbocharger. They do this while running on 91 octane
- heelix 3y ago
  The beauty of G100UL is you just need an STC - just paperwork - to be legal with GA aircraft. All gasoline powered aircraft and engines in the FAA’s type certificate database are covered by the STC for G100UL... which is amazing. I'll be doing it, as soon as our home base carries it for my 56 o200.
- mchid 3y ago
  They literally don't when G100UL exist, which is approved as a full drop in replacement safe for all engines.

foxyv 3y ago

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. AVWeb did a couple videos on the subject here: https://youtu.be/9F-WngVMJBQ?si=Qb_IYu4QwZlOTDCv https://youtu.be/9F-WngVMJBQ?si=Qb_IYu4QwZlOTDCv https://youtu.be/ovJBJjZTjsk?si=f2OwwZMmuEUTx6wL https://youtu.be/ovJBJjZTjsk?si=f2OwwZMmuEUTx6wL

codexb 3y ago

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.

phkahler 3y ago
>> The problem is that they won't approve engines for general aviation that use unleaded gas. 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.
jabl 3y ago
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.

phkahler 3y ago

>> 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.

marcosdumay 3y ago
> 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.
- SoftTalker 3y ago
  There is some interesting stuff happening in battery-electric aircraft as trainiers. You can only fly them about 45 minutes and within a local radius of the airport but they are good for people learning the stick-and-rudder basics of flying.
  - MrDrMcCoy 3y ago
    Gliders are even better for learning flight basics, do a better job of teaching you to anticipate and work with turbulence, and have a variable time limit.
    - lazide 3y ago
      Glider hours aren't going to count towards any useful type certification though? Unless you think someone is going to be qualified on a Twin Otter because of 1000 glider hours?

SomeHacker44 3y ago

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.

outworlder 3y ago
> 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. 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.
scarby2 3y ago
the requirement for the STC on a per-aircraft basis is now gone AFAIK. That was the effect of the FAA's "legalization" last year.
- sokoloff 3y ago
  You still have to purchase the STC for your airplane serial number and engine(s) serial number. What the FAA did was approve that all-model STC as being valid/legal to sell and "install" (which is just placards).

TylerE 3y ago

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.

tinus_hn 3y ago
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.
FireBeyond 3y ago
Except... certification is done: https://www.aopa.org/news-and-media/all-news/2022/september/01/closer-to-an-unleaded-future https://www.aopa.org/news-and-media/all-news/2022/september/... > 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.

lazide 3y ago

It's a pretty dick move to ban something a large portion of the aviation community needs when there is literally no legal alternative no? There is now a legal alternative. Working as intended.

TSiege 3y ago
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? Edit, looks like there is an alternative https://news.ycombinator.com/item?id=38040091 https://news.ycombinator.com/item?id=38040091
- lazide 3y ago
  The amount of lead taken up from leaded avgas in the community is so close to zero (compared to other sources) that it hasn't outweighed the damage done by essentially banning general aviation. Which is what banning leaded avgas would do without an alternative. It's already nearly choked to death by regulation, but that was a step too far. But they also clearly have been working to mitigate it, and now that they have an alternate are banning leaded avgas and launching it. So what is your rant about exactly?
  - dicknuckle 3y ago
    You're going to need to provide a source for "the amount of lead taken up from leaded avgas in the community is close to zero" otherwise it's FUD.
    - lazide 3y ago
      https://www.mayoclinic.org/diseases-conditions/lead-poisoning/symptoms-causes/syc-20354717# https://www.mayoclinic.org/diseases-conditions/lead-poisonin... Do you even see it in the list? This NIH study shows it as ‘small, but significant’ - accounting for anywhere from 2.1-4.4% of the lead found in children’s blood near piston airports. https://ehp.niehs.nih.gov/doi/10.1289/ehp.1003231 https://ehp.niehs.nih.gov/doi/10.1289/ehp.1003231 Less than 5% of the amount of lead total in their blood from that source, literally for the highest risk segment you can find. Even if completely eliminated, the other 95% isn’t going anywhere. Even if you don’t average it out across the population, it’s hard to argue that isn’t so close to zero that nearly any significant benefit anywhere else would make it not a rush. Most airborne lead pollution now is industrial anyway, and that is clearly the calculus there. As is the #1 and #2 sources of lead ingestion for children, old paint and old pipes. I’m glad they’re getting rid of it, but I’m not going to complain they didn’t drop everything to rush it. Especially since if they did, they’d almost certainly kill more people in the resulting plane crashes.

mulmen 3y ago

The FAA recently approved unleaded avgas. The EPA never had a problem with unleaded gas.

SAI_Peregrinus 3y ago

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.