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I was never clear on why leaded avgas wasn't banned long ago. I know I've run across information on the internet about aircraft engines that can run on unleaded

I was never clear on why leaded avgas wasn't banned long ago. I know I've run across information on the internet about aircraft engines that can run on unleaded.

NikolaeVarius 6y ago
They're working on it. Can't ban it since many airplanes still require it.
- amluto 6y ago
  I’m not entirely sure I buy this argument. Ban it effective on a fixed date in a few years and introduce a favorable regulatory regime to help with replacements. If some planes won’t be able to fly, so be it. Alternatively, introduce a Pigouvian tax: charge an obscene and increasing amount to burn leaded fuel. This is kind of like the regulations that permit grossly polluting old collectible cars to operate. Sure, they have history, but that’s not a sufficient excuse to allow them to operate unmodified near other people.
  - dpe82 6y ago
    Most piston engine aircraft in the country require, by regulation, 100LL. Oil companies and the FAA have been working for years to develop a replacement and came very close a couple years ago, but since the FAA strongly favors safety and reliability over almost any other consideration it takes a very long time to collect enough data to have confidence a potential replacement is truly equivalent. We have ~80 years of safety data for 100LL. Generally speaking, airports are reluctant to spend money on a second set of tanks, pumps, etc. required during a transition period; though some have - particularly in the midwest where there are a lot of less regulated homebuilt aircraft that can burn alternative fuels. A lot of pilots would love to burn something else. 100LL is relatively nasty and builds up in engines, shortening their life. It's even actively discouraged to burn 100LL in some more modern small aircraft engines like the Rotax 912 and pilots like myself who run that engine look for non-leaded fuel whenever practical because it's healthier for the engine. But well maintained aircraft last just about forever and the legacy fleet is absolutely enormous.
    - perl4ever 6y ago
      "...it takes a very long time to collect enough data to have confidence a potential replacement is truly equivalent. We have ~80 years of safety data for 100LL" It sounds odd to put it this way, because leaded gasoline started being phased out over 40 years ago. In an alternate universe, we would now have 40 years of safety data for unleaded and for leaded.
      - labcomputer 6y ago
        > we would now have 40 years of safety data for unleaded and for leaded. When lead was banned in auto gas, it was replaced by MTBE, which itself was banned in most states by 2007. The alternative to MTBE is Ethanol, which is currently used in auto gas. But Ethanol is incompatible with aircraft because it is corrosive to aluminum (and tends to cause more serious vapor-lock problems in fuel lines). In other words, there's no widely-used blend of fuel that could even potentially have 40 years of safety data. Pilots are already used to paying a lot for fuel (more than auto gas), so there's money at stake if someone can come up with an unleaded alternative. It's just that someone has to invent that safe alternative first. On top of that, fuel is a particularly sensitive issue to the FAA because fuel and engine malfunctions are currently the 3rd and 4th leading causes of aircraft accidents (and this is after the FAA has spent decades on safety programs to reduce fuel-related accidents).
        userbinator 6y ago
        But Ethanol is incompatible with aircraft because it is corrosive to aluminum (and tends to cause more serious vapor-lock problems in fuel lines). Incidentally, this is also an issue with small engines in things like garden equipment --- the ethanol tends to degrade plastics over time too.
        perl4ever 6y ago
        I was generally aware of MTBE, but I didn't know it was universal since the 70s nor necessary for all grades of fuel. What about iso-octane? Also, I happen to have a car from the 80s and in looking for information about the consequences of using fuel with ethanol, some say it can be a problem while other people say at that point in time it was designed to handle it. So I'm not clear on what diversity there was in the types of fuel available over time.
  - parsimo2010 6y ago
    I’m an owner and pilot of one of the previously mentioned planes that run on leaded fuel. The current issue with your plan is that for a vast chunk of the GA fleet there is no certified alternative to leaded fuel. Some planes have supplemental type certificates (STC) available that allow them to burn unleaded fuel, but many do not (such as my Grumman Tiger). It’s not just the engine, it’s the fuel system in the plane that must be certified- this is not just a paperwork drill, there have been failed certification attempts because the fuel system couldn’t deliver enough fuel pressure at certain temperatures. The FAA is required to evaluate the impact of new regulations on the existing fleet. A change that would eliminate or place a prohibitively high tax on leaded fuel would likely be shown to eliminate half of the GA fleet. This will not be approved until the impact can be reduced. Developing and certifying new engines and fuel system components for all the different aircraft type certificates is totally infeasible; a new fuel substitute is pretty much the only option. The FAA has made huge regulation changes before but there has always been an alternative. The recent ADS-B mandate requires about $5k of new equipment before a plane is allowed to fly where Mode C transponders were previously sufficient. This is/was expensive for many private pilots, but was deemed to be acceptable for the safety benefits gained. Some owners have chosen not to add the ADS-B equipment and haven’t been allowed to fly in some parts of the country, but they can still fly most places. A fuel regulation that grounds half the fleet with no alternative regardless of the price is a completely other level of impact. The FAA and most pilots want an alternative to leaded fuel (at least for the assumed cost savings if not for the environment). Energy companies are working on unleaded substitutes but current options still require an STC to burn. You probably won’t see leaded fuel going away until there is a universally approved replacement that can just take the place of 100LL at every airport in the country. Edit: or barring a complete drop-in replacement, at least an option that can be shown to work in existing engines and fuel systems without requiring major R&D.
    - fiter 6y ago
      It doesn't seem like you're addressing the pollution/health effects to the population caused by burning leaded gas and the relative harm of that versus the benefit of keeping the existing fleet flying. Is that because the pollution is so small or that the pollution just is not relevant in your opinion?
jeffbee 6y ago
You can read these other replies, but the shorter explanation is that the AOPA is in all relevant respects the NRA but with aircraft instead of guns, and the owners have achieved cold-dead-hands status with their obsolete planes.
- PunksATawnyFill 6y ago
  Not accurate. The AOPA typically takes positions that protect public safety, such as opposing Trump’s attempted giveaway of our ATC to the airlines. However, the GA industry should be condemned for its failure to face the writing on the wall about leaded gas, which has been obvious since the ‘70s. On the other hand: Until recently, stifling certification requirements made it nearly impossible for these low-volume manufacturers to innovate. Nobody wants leaded gas. The other sham being perpetrated is advertising some plane engines as running on “automotive” gas. This is BS, because that means only PURE gasoline, not gasohol. I challenge you to find a gas station selling 100% gasoline. I haven’t seen that in decades. So the touted “mogas” is nearly as much of a niche fuel as 100LL.
  - pathseeker 6y ago
    https://www.pure-gas.org https://www.pure-gas.org
dehrmann 6y ago
Is high-octane unleaded or jet fuel the more likely replacement? (It might be called "jet fuel," but it's similar to diesel.)
- tjohns 6y ago
  High-octane unleaded. There's a couple options that are being tested right now.

I was never clear on why leaded avgas wasn't banned long ago. I know I've run across information on the internet about aircraft engines that can run on unleaded.

NikolaeVarius 6y ago

They're working on it. Can't ban it since many airplanes still require it.

amluto 6y ago
I’m not entirely sure I buy this argument. Ban it effective on a fixed date in a few years and introduce a favorable regulatory regime to help with replacements. If some planes won’t be able to fly, so be it. Alternatively, introduce a Pigouvian tax: charge an obscene and increasing amount to burn leaded fuel. This is kind of like the regulations that permit grossly polluting old collectible cars to operate. Sure, they have history, but that’s not a sufficient excuse to allow them to operate unmodified near other people.
- dpe82 6y ago
  Most piston engine aircraft in the country require, by regulation, 100LL. Oil companies and the FAA have been working for years to develop a replacement and came very close a couple years ago, but since the FAA strongly favors safety and reliability over almost any other consideration it takes a very long time to collect enough data to have confidence a potential replacement is truly equivalent. We have ~80 years of safety data for 100LL. Generally speaking, airports are reluctant to spend money on a second set of tanks, pumps, etc. required during a transition period; though some have - particularly in the midwest where there are a lot of less regulated homebuilt aircraft that can burn alternative fuels. A lot of pilots would love to burn something else. 100LL is relatively nasty and builds up in engines, shortening their life. It's even actively discouraged to burn 100LL in some more modern small aircraft engines like the Rotax 912 and pilots like myself who run that engine look for non-leaded fuel whenever practical because it's healthier for the engine. But well maintained aircraft last just about forever and the legacy fleet is absolutely enormous.
  - perl4ever 6y ago
    "...it takes a very long time to collect enough data to have confidence a potential replacement is truly equivalent. We have ~80 years of safety data for 100LL" It sounds odd to put it this way, because leaded gasoline started being phased out over 40 years ago. In an alternate universe, we would now have 40 years of safety data for unleaded and for leaded.
    - labcomputer 6y ago
      > we would now have 40 years of safety data for unleaded and for leaded. When lead was banned in auto gas, it was replaced by MTBE, which itself was banned in most states by 2007. The alternative to MTBE is Ethanol, which is currently used in auto gas. But Ethanol is incompatible with aircraft because it is corrosive to aluminum (and tends to cause more serious vapor-lock problems in fuel lines). In other words, there's no widely-used blend of fuel that could even potentially have 40 years of safety data. Pilots are already used to paying a lot for fuel (more than auto gas), so there's money at stake if someone can come up with an unleaded alternative. It's just that someone has to invent that safe alternative first. On top of that, fuel is a particularly sensitive issue to the FAA because fuel and engine malfunctions are currently the 3rd and 4th leading causes of aircraft accidents (and this is after the FAA has spent decades on safety programs to reduce fuel-related accidents).
      - userbinator 6y ago
        But Ethanol is incompatible with aircraft because it is corrosive to aluminum (and tends to cause more serious vapor-lock problems in fuel lines). Incidentally, this is also an issue with small engines in things like garden equipment --- the ethanol tends to degrade plastics over time too.
      - perl4ever 6y ago
        I was generally aware of MTBE, but I didn't know it was universal since the 70s nor necessary for all grades of fuel. What about iso-octane? Also, I happen to have a car from the 80s and in looking for information about the consequences of using fuel with ethanol, some say it can be a problem while other people say at that point in time it was designed to handle it. So I'm not clear on what diversity there was in the types of fuel available over time.
- parsimo2010 6y ago
  I’m an owner and pilot of one of the previously mentioned planes that run on leaded fuel. The current issue with your plan is that for a vast chunk of the GA fleet there is no certified alternative to leaded fuel. Some planes have supplemental type certificates (STC) available that allow them to burn unleaded fuel, but many do not (such as my Grumman Tiger). It’s not just the engine, it’s the fuel system in the plane that must be certified- this is not just a paperwork drill, there have been failed certification attempts because the fuel system couldn’t deliver enough fuel pressure at certain temperatures. The FAA is required to evaluate the impact of new regulations on the existing fleet. A change that would eliminate or place a prohibitively high tax on leaded fuel would likely be shown to eliminate half of the GA fleet. This will not be approved until the impact can be reduced. Developing and certifying new engines and fuel system components for all the different aircraft type certificates is totally infeasible; a new fuel substitute is pretty much the only option. The FAA has made huge regulation changes before but there has always been an alternative. The recent ADS-B mandate requires about $5k of new equipment before a plane is allowed to fly where Mode C transponders were previously sufficient. This is/was expensive for many private pilots, but was deemed to be acceptable for the safety benefits gained. Some owners have chosen not to add the ADS-B equipment and haven’t been allowed to fly in some parts of the country, but they can still fly most places. A fuel regulation that grounds half the fleet with no alternative regardless of the price is a completely other level of impact. The FAA and most pilots want an alternative to leaded fuel (at least for the assumed cost savings if not for the environment). Energy companies are working on unleaded substitutes but current options still require an STC to burn. You probably won’t see leaded fuel going away until there is a universally approved replacement that can just take the place of 100LL at every airport in the country. Edit: or barring a complete drop-in replacement, at least an option that can be shown to work in existing engines and fuel systems without requiring major R&D.
  - fiter 6y ago
    It doesn't seem like you're addressing the pollution/health effects to the population caused by burning leaded gas and the relative harm of that versus the benefit of keeping the existing fleet flying. Is that because the pollution is so small or that the pollution just is not relevant in your opinion?

jeffbee 6y ago

You can read these other replies, but the shorter explanation is that the AOPA is in all relevant respects the NRA but with aircraft instead of guns, and the owners have achieved cold-dead-hands status with their obsolete planes.

PunksATawnyFill 6y ago
Not accurate. The AOPA typically takes positions that protect public safety, such as opposing Trump’s attempted giveaway of our ATC to the airlines. However, the GA industry should be condemned for its failure to face the writing on the wall about leaded gas, which has been obvious since the ‘70s. On the other hand: Until recently, stifling certification requirements made it nearly impossible for these low-volume manufacturers to innovate. Nobody wants leaded gas. The other sham being perpetrated is advertising some plane engines as running on “automotive” gas. This is BS, because that means only PURE gasoline, not gasohol. I challenge you to find a gas station selling 100% gasoline. I haven’t seen that in decades. So the touted “mogas” is nearly as much of a niche fuel as 100LL.
- pathseeker 6y ago
  https://www.pure-gas.org https://www.pure-gas.org

dehrmann 6y ago

Is high-octane unleaded or jet fuel the more likely replacement? (It might be called "jet fuel," but it's similar to diesel.)

tjohns 6y ago
High-octane unleaded. There's a couple options that are being tested right now.