11 ms·

> 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.
        mlyle 3y ago
        > 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. Lots of airports are owned or regulated by local governments which might want to move that single tank to just unleaded. E.g. Santa Clara County banned 100LL at local airports. Forklift upgrades suck, too. You're best off getting some of the way along and then forklift. Arguably we're reaching that point.
    - sokoloff 3y ago
      What's the FAA incentive to change the type certification (and STC) rules here? There's a perfectly workable STC path, that's not even that expensive [almost rounds to $0 in the scope of private aircraft ownership expenses). The TC says you must run 100LL. The STC says you can freely mix G100UL in any ratio. The legal/certification problem is solved.
  - mchid 3y ago
    Approved as a full drop in replacement, legal on all planes. You're conflating G100UL with UL94.
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.

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.
      - mlyle 3y ago
        > 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. Lots of airports are owned or regulated by local governments which might want to move that single tank to just unleaded. E.g. Santa Clara County banned 100LL at local airports. Forklift upgrades suck, too. You're best off getting some of the way along and then forklift. Arguably we're reaching that point.
  - sokoloff 3y ago
    What's the FAA incentive to change the type certification (and STC) rules here? There's a perfectly workable STC path, that's not even that expensive [almost rounds to $0 in the scope of private aircraft ownership expenses). The TC says you must run 100LL. The STC says you can freely mix G100UL in any ratio. The legal/certification problem is solved.
- mchid 3y ago
  Approved as a full drop in replacement, legal on all planes. You're conflating G100UL with UL94.

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.