6 ms·

TEL (tetraethyl lead) had and has other advantages over ethanol beyond patentability - Unlike TEL, ethanol is hydrophilic, which makes gasoline blended with i

by Aloha 5y ago

TEL (tetraethyl lead) had and has other advantages over ethanol beyond patentability - Unlike TEL, ethanol is hydrophilic, which makes gasoline blended with it more apt to be contaminated with water, and other water containing contaminants, this is particularly relevant for aviation uses and also reducing incidences of vapor lock. TEL is also (more) rubber and seal friendly, other than the (very) high risk of lead toxicity, TEL blended gasoline is easier to work with and process than Ethanol blended gasoline. TEL also acts as a natural lubricant of its own, the lead acting as lubricant, particularly on valve and other top end engine components. This isn't really a defense of TEL - particularly not in road gas, while it was understood that exposure to large quantities of lead was toxic, toxicity of low dose exposure to environmental lead wasn't really fully understood until the 50's/60's, we also didn't really understood how long environmental lead lingered around until the 60's. Modern technologies have overcome much of the issues from ethanol in road gas, but there are reasons TEL is still used in AvGas. TEL in AvGas was vital in reaching higher octane, and Ethanol is contraindicated in AvGas (at the last I looked into the topic) because of its hydrophilic nature - our ability (the allies) to produce high octane AvGas is one of the factors that won WW2, and use of TEL was a deciding factor in that.

R0b0t1 5y ago
Those problems were solved for cars, they can be solved for planes. We shouldn't use it. Bioaccumulation of heavy metals was understood very early. Everything has a cost, spraying lead everywhere should be higher than what we are willing to pay. I am guessing it's still allowed because people who fly planes can afford to lobby. I was astounded to find TEL was still allowed in aviation fuels. Rates of cancers etc are higher near military bases due to fuel handling incidents.
- bombcar 5y ago
  Military planes just kerosene/JP-8 which contains no lead as far as I know.
  - R0b0t1 5y ago
    The fuel itself is toxic to the environment and animals. The fuels can have really harsh things in them like benzene, iirc.
    - nitrogen 5y ago
      Not too different from ordinary gasoline.
      - dzhiurgis 5y ago
        Which is complete bonkers. We fill our cars every week and when you stand there thinking "damn I love this smell" yet when there's 1ppm of benzene in sun cream people scream "caaaancer"...
  - letitbeirie 5y ago
    Kerosene/JP-8 is great in a jet but it's not going to get you very far in a piston prop.
    - formerly_proven 5y ago
      There is no particular reason why you can't put a diesel engine in a plane and indeed there are a number of diesel engines certified for just that.
      - xyzzyz 5y ago
        There are few technical reasons, to be sure, but there are plenty of economic and business reasons. The most popular engines in general aviation are Continental/Lycoming ones, and these are based on what, 50+ years old basic designs? Automotive industry have developed significantly better piston engines in last few decades, in terms of power to weight ratio, fuel efficiency, MTBF and service interval. However, the nature of the field, its relative niche quality, and regulatory framework make it difficult to adapt and adopt them in general aviation. There has been recent attempt to do it, with diesel engines from German automotive industry, but they are facing a lot of very real problems, for example, lack of maintenance infrastructure.
- consumer451 5y ago
  It’s finally over. > After more than three decades of research and development, general aviation finally has an approved unleaded 100-octane fuel. https://www.avweb.com/aviation-news/gami-awarded-long-awaited-stc-for-unleaded-100-octane-avgas/ https://www.avweb.com/aviation-news/gami-awarded-long-awaite...
  - bleachedsleet 5y ago
    It will be over, but it’s not over yet. Your link says that it will both take a while for it to come to market and also be more expensive to produce…an expense that will likely be balked at by the airlines until forced to use it at which point it will be the customers that pay.
    - Aloha 5y ago
      Airlines (outside of bush planes) are not using AvGas in any substantive quantity, and have not been since the early 60's. The amount of AvGas used a year is dwarfed (several times over) by the amount of Jet Fuel (Jet A does not have TEL in it). AvGas (which uses TEL) is used by general aviation exclusively.
      - LargoLasskhyfv 5y ago
        That doesn't make jet fuel any better. Just search for 'Toxicologic assessment' or 'profile of jet fuel' and focus on the 'A1', which is the one used for commercial aviation. Then there is the elephant in the room nobody wants to talk about, the military which is using the 'JP-X' variants all over the world, some of them even for their cars and trucks, because, hey, it's just better Diesel, why would we stock different fuels if we don't have to? What a logistic nightmare!1!!
        eutectic 5y ago
        Organic compounds burn up, lead just accumulates.
- Aloha 5y ago
  The amount of TEL used in AvGas is infinitesimally small, its only used in Aviation Gasoline, which is only used in older piston engined craft, the military flies none of these as far as I know.
- jrockway 5y ago
  > Rates of cancers etc are higher near military bases due to fuel handling incidents. Avgas is only used in piston engines, and the military mostly flies turbines, which use ordinary jet fuel (which does not contain lead). They have some, but I think if you told the military "jets and turboprops only" it wouldn't be a big problem. (Not sure how they would train new pilots, however.) If you're looking for disease/damage from lead in avgas, you want to find a little airport in the middle of nowhere that has a really good restaurant on the field ;) https://www.faa.gov/about/initiatives/avgas https://www.faa.gov/about/initiatives/avgas > I am guessing it's still allowed because people who fly planes can afford to lobby. People that fly piston engines do not have any money to lobby. To me it feels very similar to why software engineers pay so much tax -- we get paid just enough to be dinged by things like the AMT, but not enough to afford lobbyists.
  - dredmorbius 5y ago
    I find the T-53A, a trainer version of the Cirrus SR20, which is piston-engine propeller aircraft: https://en.wikipedia.org/wiki/List_of_active_United_States_military_aircraft https://en.wikipedia.org/wiki/List_of_active_United_States_m... https://en.wikipedia.org/wiki/Cirrus_SR20 https://en.wikipedia.org/wiki/Cirrus_SR20 There might be some piston-based helicopters (too many to check), or drones. Otherwise, yes, bangers are out.
  - R0b0t1 5y ago
    Jet fuel is carcinogenic and causes other problems, I didn't say this was just about lead. https://pubmed.ncbi.nlm.nih.gov/973128/ https://pubmed.ncbi.nlm.nih.gov/973128/ as an example.
- tialaramex 5y ago
  Politically the rationale is likely that this constituency is small and so forcing them will have a relatively small benefit compared to the main policy goal; but they really care. If you fly a piston prop, you likely don't have $1M spare (you could use that to trade your piston plane for a small jet) for Washington lobbyists, but you do have a vote and you care about banning the only fuel you are authorised to use enough that you're going to use that vote and you're going to be loud about it. A previous article about Leaded Petrol caused me to read how the UK exempted some very old cars which could not be effectively modified. There's actually a waiver so that, in theory, every fuel station in the country can do paperwork to get a small amount of leaded gasoline (a tiny fraction of their total fuel sales) and sell it for this purpose. The politicians were thus able to tell their constituents we did not screw you, just ask your local supplier to set aside fuel for you. But economics does the rest, at first those retailers see sales of leaded fuel are very low. Those who love classics maybe decide to set aside the option for a year or two and see how it goes, everybody else stops selling leaded fuel. The wholesalers now see that sales of leaded fuel are tiny, so they don't bother making it, it becomes a special order, which then further increases the pressure not to bother stocking it. Today enthusiasts will just mail order the lead additive and pour it into their tank after a refill or they use a substitute additive which these days works well enough, the politicians didn't have to lift a finger.
Zigurd 5y ago
"Dry gas" which is used to correct moisture problems in cars' fuel systems is alcohol: Ethanol, methanol, etc. and it takes advantage of alcohol being hydrophilic. Ethanol has requirements for hoses and seals that might otherwise be degraded by alcohol. But this is not an ongoing issue in modern vehicles.
- HPsquared 5y ago
  The same property, increased ability to absorb water, both helps to remove excess of water and can cause a problem in the longer-term. It's like using a towel to dry your shower tray: in the short run it's helpful but if you leave it there all the time you'll end up with a permanently soggy towel keeping everything damp. EDIT: Some empirical evidence for the doubters- https://youtu.be/UvS_D4_lF5U https://youtu.be/UvS_D4_lF5U
nate_meurer 5y ago
> TEL also acts as a natural lubricant of its own, the lead acting as lubricant, particularly on valve and other top end engine components. This is a myth. TEL has no lubricative properties in engines. The reality is opposite; lead deposits are corrosive. From https://www.shell.com/business-customers/aviation/aeroshell/knowledge-centre/technical-talk/techart-18-30071600.html https://www.shell.com/business-customers/aviation/aeroshell/...: "The temperature for Lead deposits to form tend to be favourable around the spark plugs (as the whole mixture is quite cool before the flame starts to propagate) and on the exhaust valve stem (as the mixture cools after combustion). The problem is that the deposits are electrically conductive, which shorts out the spark plug - and corrosive, which can start to attack the metal of the valve stems."
- Aloha 5y ago
  TEL before combustion does have lubricative qualities, much in the way phosphorus does in oil or sulfur does in diesel fuel. After combustion, its like any heavy metal being burned, it turns into an oxide, which has a variety of characteristics.
  - nate_meurer 5y ago
    It's the supposed benefits of the post-combustion lead oxide deposits that defenders of leaded gas cite. I have never heard anyone cite the lubricity of TEL itself. The most popular theory is that the lead oxide fouling reduces the occurence or effects of micro-welds between valve and seat surfaces, which otherwise produce abrasive particles that contribute to valve seat recession. While this theory is plausible, it has not been shown to occur under normal operating conditions in automotive engines, nor in aviation engines as far as I know. The final report from the EPA's Valve Seat Recession Working Group found no evidence that leaded gas reduces engine wear under any but the most extreme operating conditions: https://archive.epa.gov/international/air/web/pdf/vsr-finaldraft.pdf https://archive.epa.gov/international/air/web/pdf/vsr-finald... "In real world conditions, virtually no evidence of excessive valve wear has been found in vehicle or engine operation in normal everyday use, and several studies that monitored vehicles in actual daily service in countries that eliminated lead found no excessive valve wear."

by Aloha 5y ago

R0b0t1 5y ago

Those problems were solved for cars, they can be solved for planes. We shouldn't use it. Bioaccumulation of heavy metals was understood very early. Everything has a cost, spraying lead everywhere should be higher than what we are willing to pay. I am guessing it's still allowed because people who fly planes can afford to lobby. I was astounded to find TEL was still allowed in aviation fuels. Rates of cancers etc are higher near military bases due to fuel handling incidents.

bombcar 5y ago
Military planes just kerosene/JP-8 which contains no lead as far as I know.
- R0b0t1 5y ago
  The fuel itself is toxic to the environment and animals. The fuels can have really harsh things in them like benzene, iirc.
  - nitrogen 5y ago
    Not too different from ordinary gasoline.
    - dzhiurgis 5y ago
      Which is complete bonkers. We fill our cars every week and when you stand there thinking "damn I love this smell" yet when there's 1ppm of benzene in sun cream people scream "caaaancer"...
- letitbeirie 5y ago
  Kerosene/JP-8 is great in a jet but it's not going to get you very far in a piston prop.
  - formerly_proven 5y ago
    There is no particular reason why you can't put a diesel engine in a plane and indeed there are a number of diesel engines certified for just that.
    - xyzzyz 5y ago
      There are few technical reasons, to be sure, but there are plenty of economic and business reasons. The most popular engines in general aviation are Continental/Lycoming ones, and these are based on what, 50+ years old basic designs? Automotive industry have developed significantly better piston engines in last few decades, in terms of power to weight ratio, fuel efficiency, MTBF and service interval. However, the nature of the field, its relative niche quality, and regulatory framework make it difficult to adapt and adopt them in general aviation. There has been recent attempt to do it, with diesel engines from German automotive industry, but they are facing a lot of very real problems, for example, lack of maintenance infrastructure.
consumer451 5y ago
It’s finally over. > After more than three decades of research and development, general aviation finally has an approved unleaded 100-octane fuel. https://www.avweb.com/aviation-news/gami-awarded-long-awaited-stc-for-unleaded-100-octane-avgas/ https://www.avweb.com/aviation-news/gami-awarded-long-awaite...
- bleachedsleet 5y ago
  It will be over, but it’s not over yet. Your link says that it will both take a while for it to come to market and also be more expensive to produce…an expense that will likely be balked at by the airlines until forced to use it at which point it will be the customers that pay.
  - Aloha 5y ago
    Airlines (outside of bush planes) are not using AvGas in any substantive quantity, and have not been since the early 60's. The amount of AvGas used a year is dwarfed (several times over) by the amount of Jet Fuel (Jet A does not have TEL in it). AvGas (which uses TEL) is used by general aviation exclusively.
    - LargoLasskhyfv 5y ago
      That doesn't make jet fuel any better. Just search for 'Toxicologic assessment' or 'profile of jet fuel' and focus on the 'A1', which is the one used for commercial aviation. Then there is the elephant in the room nobody wants to talk about, the military which is using the 'JP-X' variants all over the world, some of them even for their cars and trucks, because, hey, it's just better Diesel, why would we stock different fuels if we don't have to? What a logistic nightmare!1!!
      - eutectic 5y ago
        Organic compounds burn up, lead just accumulates.
Aloha 5y ago
The amount of TEL used in AvGas is infinitesimally small, its only used in Aviation Gasoline, which is only used in older piston engined craft, the military flies none of these as far as I know.
jrockway 5y ago
> Rates of cancers etc are higher near military bases due to fuel handling incidents. Avgas is only used in piston engines, and the military mostly flies turbines, which use ordinary jet fuel (which does not contain lead). They have some, but I think if you told the military "jets and turboprops only" it wouldn't be a big problem. (Not sure how they would train new pilots, however.) If you're looking for disease/damage from lead in avgas, you want to find a little airport in the middle of nowhere that has a really good restaurant on the field ;) https://www.faa.gov/about/initiatives/avgas https://www.faa.gov/about/initiatives/avgas > I am guessing it's still allowed because people who fly planes can afford to lobby. People that fly piston engines do not have any money to lobby. To me it feels very similar to why software engineers pay so much tax -- we get paid just enough to be dinged by things like the AMT, but not enough to afford lobbyists.
- dredmorbius 5y ago
  I find the T-53A, a trainer version of the Cirrus SR20, which is piston-engine propeller aircraft: https://en.wikipedia.org/wiki/List_of_active_United_States_military_aircraft https://en.wikipedia.org/wiki/List_of_active_United_States_m... https://en.wikipedia.org/wiki/Cirrus_SR20 https://en.wikipedia.org/wiki/Cirrus_SR20 There might be some piston-based helicopters (too many to check), or drones. Otherwise, yes, bangers are out.
- R0b0t1 5y ago
  Jet fuel is carcinogenic and causes other problems, I didn't say this was just about lead. https://pubmed.ncbi.nlm.nih.gov/973128/ https://pubmed.ncbi.nlm.nih.gov/973128/ as an example.
tialaramex 5y ago
Politically the rationale is likely that this constituency is small and so forcing them will have a relatively small benefit compared to the main policy goal; but they really care. If you fly a piston prop, you likely don't have $1M spare (you could use that to trade your piston plane for a small jet) for Washington lobbyists, but you do have a vote and you care about banning the only fuel you are authorised to use enough that you're going to use that vote and you're going to be loud about it. A previous article about Leaded Petrol caused me to read how the UK exempted some very old cars which could not be effectively modified. There's actually a waiver so that, in theory, every fuel station in the country can do paperwork to get a small amount of leaded gasoline (a tiny fraction of their total fuel sales) and sell it for this purpose. The politicians were thus able to tell their constituents we did not screw you, just ask your local supplier to set aside fuel for you. But economics does the rest, at first those retailers see sales of leaded fuel are very low. Those who love classics maybe decide to set aside the option for a year or two and see how it goes, everybody else stops selling leaded fuel. The wholesalers now see that sales of leaded fuel are tiny, so they don't bother making it, it becomes a special order, which then further increases the pressure not to bother stocking it. Today enthusiasts will just mail order the lead additive and pour it into their tank after a refill or they use a substitute additive which these days works well enough, the politicians didn't have to lift a finger.

Zigurd 5y ago

"Dry gas" which is used to correct moisture problems in cars' fuel systems is alcohol: Ethanol, methanol, etc. and it takes advantage of alcohol being hydrophilic. Ethanol has requirements for hoses and seals that might otherwise be degraded by alcohol. But this is not an ongoing issue in modern vehicles.

HPsquared 5y ago
The same property, increased ability to absorb water, both helps to remove excess of water and can cause a problem in the longer-term. It's like using a towel to dry your shower tray: in the short run it's helpful but if you leave it there all the time you'll end up with a permanently soggy towel keeping everything damp. EDIT: Some empirical evidence for the doubters- https://youtu.be/UvS_D4_lF5U https://youtu.be/UvS_D4_lF5U

nate_meurer 5y ago

> TEL also acts as a natural lubricant of its own, the lead acting as lubricant, particularly on valve and other top end engine components. This is a myth. TEL has no lubricative properties in engines. The reality is opposite; lead deposits are corrosive. From https://www.shell.com/business-customers/aviation/aeroshell/knowledge-centre/technical-talk/techart-18-30071600.html https://www.shell.com/business-customers/aviation/aeroshell/...: "The temperature for Lead deposits to form tend to be favourable around the spark plugs (as the whole mixture is quite cool before the flame starts to propagate) and on the exhaust valve stem (as the mixture cools after combustion). The problem is that the deposits are electrically conductive, which shorts out the spark plug - and corrosive, which can start to attack the metal of the valve stems."

Aloha 5y ago
TEL before combustion does have lubricative qualities, much in the way phosphorus does in oil or sulfur does in diesel fuel. After combustion, its like any heavy metal being burned, it turns into an oxide, which has a variety of characteristics.
- nate_meurer 5y ago
  It's the supposed benefits of the post-combustion lead oxide deposits that defenders of leaded gas cite. I have never heard anyone cite the lubricity of TEL itself. The most popular theory is that the lead oxide fouling reduces the occurence or effects of micro-welds between valve and seat surfaces, which otherwise produce abrasive particles that contribute to valve seat recession. While this theory is plausible, it has not been shown to occur under normal operating conditions in automotive engines, nor in aviation engines as far as I know. The final report from the EPA's Valve Seat Recession Working Group found no evidence that leaded gas reduces engine wear under any but the most extreme operating conditions: https://archive.epa.gov/international/air/web/pdf/vsr-finaldraft.pdf https://archive.epa.gov/international/air/web/pdf/vsr-finald... "In real world conditions, virtually no evidence of excessive valve wear has been found in vehicle or engine operation in normal everyday use, and several studies that monitored vehicles in actual daily service in countries that eliminated lead found no excessive valve wear."