Leaded AVGAS discussion.

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Scott3

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#285917 25-May-2021 00:09

Technofreak:

Scott3:

Avgas uses the MON unit. 100LL has a minimum of 99.6 MON. Comparison 91 RON road fuel is about 85 MON. (yes the LL stands for Low Leaded - Avgas is still leaded despot wheat we know about the harm of TEL).

Avgas is still leaded because to date no one has been able to produce a viable alternative without using TEL that meets the specs required of Avgas. Yes, motor spirit has been used very successfully in some aircraft engines, however it is not suitable for all uses. One of the problems with motor spirit is vaporisation.

While the problems with lead are acknowledged what hasn't been widely acknowledged is the problems that come with the the additives added to petrol to replace the TEL. Basically replacing one baddie with another.

The over all effects of the continued use of Avgas are miniscule as Avgas forms such a small part of the total petrol usage. The safety benefits of 100 LL Avgas certainly outweigh any benefits of using unleaded alternatives.

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#2712708 25-May-2021 00:10

Scott3:

You have absolutely hit the crux of the issue with your first sentence. It is not possible to get rid of the TEL, and maintain the same properties at a price point that is competitive with 100LL.

But the exact same 100LL properties aren't actually required for general aviation. As an example the entire range of the popular aircraft engine supplier rotax are approved to run E10, MOGAS and avgas...

The reality is that ongoing use TEL with it's well known impact on human health is not a viable solution. As such I think we need to give say 10 years notice to the General Avaitaion community, and then ban it outright.

Also the world is down to a single (legal) TEL supplier, so even ignoring the health impacts we should be looking to move away from this for security of supply reasons.

The General aviation community will need to pick from the raft of alternatives.

https://en.wikipedia.org/wiki/Avgas#New_unleaded_fuel_grades

Personally I think a fairly high octane, ethanol free MOGAS is the likely outcome. (Either 98Ron, or 100Ron like NPD sells in the sough island).

Some modern planes with rotax brand or similar engines will already be approved for this.

Some engines will require approval

Some will require modification (hardened valves, compression reducing pistons etc), then approval, and will take a hit on peak power.

Some engines will not be viable to modify (or will result in a power loss such that the aircraft no longer preforms as desired), these will need to be re-powered or retired. It is possible that high performance General aviation will become the domain of turbine powered aircraft rather than piston.

I disagree that there are inherent safety benefits that come from 100LL. It's just that basically all pistion avaition engines are approved for that fuel that is preventing change. I bet people made similar arguments 40 years ago with regards to automotive fuel.

I get that general aviation will lag behind motoring and marine fuels, but seriously we started the phase out of leaded road fuel in 1986, and banned it in 1996. It is now 2021, and General Aviation is persisting with this same fuel.

NZ's fuel tax policy actively encourages the aviation community to persist with AVGAS, rather than switch to MOGAS. - The latter attracts road user tax, no refunds are available for non commercial boating.

[for the benefit of those unfamiliar with this issue, only piston planes (generally smaller stuff, i.e. the four seater Cessna Skyhawk) burn AVGAS, which is basically high octane leaded petrol. Bigger stuff (i.e. the entire Air NZ fleet) is typically either jet or turboprop and burn Jet A1, which is basically Kerosene, closer to diesel than petrol.]

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#2712709 25-May-2021 00:10

PolicyGuy:

Scott3:
You have absolutely hit the crux of the issue with your first sentence. It is not possible to get rid of the TEL, and maintain the same properties at a price point that is competitive with 100LL.
[snip]
Personally I think a fairly high octane, ethanol free MOGAS is the likely outcome. (Either 98Ron, or 100Ron like NPD sells in the sough island).
Some modern planes with rotax brand or similar engines will already be approved for this.
Some engines will require approval
Some will require modification (hardened valves, compression reducing pistons etc), then approval, and will take a hit on peak power.
Some engines will not be viable to modify (or will result in a power loss such that the aircraft no longer preforms as desired), these will need to be re-powered or retired. It is possible that high performance General aviation will become the domain of turbine powered aircraft rather than piston.

When 100LL becomes unavailable - which IMHO will be a short time after the USA Environmental Protection Agency 'screws its courage to the sticking place' and bans al leaded petrol - it will mean the end of the road runway for a large percentage of the GA fleet.
Every replacement non-leaded-fuel engine will require an STC (Supplementary Type Certificate) to be certified for every different sub-type of airframe to which it might be applied, and that's a process that costs hundreds of thousands of dollars, and might apply to a fleet of dozens to a few hundreds of individual aircraft. The US FAA has been running a programme to produce an unleaded 100LL replacement fuel for over a decade, and it has produced a few candidates none of which has so far been successful.

Since the GA fleet is almost exclusively elderly, either in years of use or a relatively recent plane mechanically identical to its 1960s predecessor, a large proportion will just have to stop flying. What percentage of those would be replaced by modern-design aircraft is the big question

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#2712710 25-May-2021 00:10

Technofreak:

Scott3:

.....It is not possible to get rid of the TEL, and maintain the same properties at a price point that is competitive with 100LL.....

....But the exact same 100LL properties aren't actually required for general aviation. As an example the entire range of the popular aircraft engine supplier rotax are approved to run E10, MOGAS and avgas...

.......It is possible that high performance General aviation will become the domain of turbine powered aircraft rather than piston.......

Nothing in the information I have read has mentioned the price point as being the problem and I have read a few articles on this issue. It's being able to meet the required standard that is the problem. For example the ethanol blended fuels meet the octane and other requirements but the ethanol blended fuel damages the seals in the fuel system so they cannot be approved.

I'd like to know how you can be so sure that 100LL properties aren't actually required for general aviation. I beg to differ. There are properties of 100LL required for general aviation. General aviation isn't just Light Sport Aircraft (LSA) powered by Rotax engines. GA is also pressurised piston Singles and Twins operating at altitudes where vaporisation is a problem. Usually these aircraft are also turbo charged which also usually requires higher octane fuel. These aircraft are running engines of less than 350 hp.

It's not just a matter of the engines being able to run mogas it's a matter of the fuel being fit for purpose in the environment it is being used. Many GA aircraft running Lycomings and Continentals have been run very successfully on mogas here in New Zealand, just not at high altitude nor turbocharged engines. In fact if I recall correctly they were limited to a lower operating ceiling while burning mogas.

Turbine engines will never take over all GA high performance operations.

A turbine isn't all that efficient compared to a piston engine below about 400 to 500 hp.
At low altitudes they burn way too much fuel.
Their operating costs are too high for some applications.

Despite the challenges, the do nothing approach is not acceptable given how nasty TEL is.

It took around a decade to phase out leaded fuel for road applications, I imagine a similar time-frame might be appropriate for avgas. Wait much longer than that, and General Aviation may need to skip over unleaded gas completely, and jump straight to Biofuel / Hydrogen / electric...

I have no specific knowledge of general aviation, but as a mechanical engineer have confidence that appropriate solutions will be found with a pressing need.

Apparently some airports in Europe are allreday running UL91 (basically Leadless LL100) with 55% fleet compadiablity.

You give the example of Ethanol fuels not being able to be approved because of seal issues. Seems like something that could be overcome with a upgraded seal system.

Regarding vaporization, In the event that an unleaded avaitaion fuel with appropriate vapor pressure properties can't be found, A pressurized fuel system could be an engineered solution to alleviate these issues.

Regarding octane, engines can be made to run with lower octane by reducing compression via say a piston swap (at the cost of peak power) - which could be made up for with a re power to a bigger displacement... Alternatively in the automotive would, gasoline direct injection technology allow higher compression ratio's to be run on readily available octanes.

Regarding pressurized piston planes, this seems to be a fairly small niche. A quick search turns up that the Piper M350 is the only one in current production. Lycomming engine in this one - that brand is in favor of ditching the lead, but wants a UL100 solution.

With regards to turbines, I don't suggest they will take over all aspects of GA, but if the next piston aviation fuel requires planes be slower and lower, it may make the jump to a turbine more attractive. Of course there is not getting around that they are really expensive to buy and run.

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#2712711 25-May-2021 00:27

Commenting with very little of my own knowledge:

I'm not sure if its true but when speaking to a pilot about AVGAS pricing he mentioned that the entire nationwide New Zealand consumption of AVGAS is less than a single moderatly busy petrol station.

I can understand the point if the market is cornered and that is pushing up prices but is the fight really worth it otherwise with such miniscule usage?

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#2712762 25-May-2021 09:49

Scott3:

Despite the challenges, the do nothing approach is not acceptable given how nasty TEL is.

It took around a decade to phase out leaded fuel for road applications, I imagine a similar time-frame might be appropriate for avgas. Wait much longer than that, and General Aviation may need to skip over unleaded gas completely, and jump straight to Biofuel / Hydrogen / electric...

I think that aviation will transition through unleaded to battery electric. Given advances expected in battery technology, I think it's likely that in 5-10 years electric will be the preferred powerplant for training aircraft. And I'd hazard a guess that most LL100 is used for training, with turbines being preferred for most commercial aviation (e.g. topdressing, carrying passengers). In the meantime, the transition to unleaded 95 Mogas is well underway.

Others have already mentioned Rotax 912 engines. I didn't see anyone say, but Rotax says the *preferred* fuel for a 912 is 95 Mogas. Avgas is an expensive alternative, not least because it involves an oil change within 25 hours. And the 912 is by far the most common engine in microlight/LSA aircraft, which are replacing the old Cessna 150s and Tomahawks for training.

The main difficulty with Mogas is shelf life, which is something like 2 weeks to a month. Avgas has a much longer shelf life. So it's possible to have large Avgas fuel tanks at airfields, and not have to refill them too often, which makes for good economics. Mogas would likely mean more often and smaller refills so that the fuel does get used within the available time. To overcome this issue, I've suggested that our airfield have a Mogas fuel pump (e.g. Allied) shared with road users. But there are issues around airfield access, so would need a fence down the middle of the station. And there's an Allied station only a few km away.

Another smaller issue is that Avgas is designed to work across a much wider range of conditions than on the surface, potentially down to -30C and perhaps 15,000ft altitude (60% of the surface air pressure). Worst case, Mogas in NZ cars has to cope with about -20C and 3000ft altitude. What's more, to help with this Mogas composition varies from summer to winter. But an aircraft may be flying at 15,000ft or more, where temperatures are 30C lower than at sea level. So in summer the fuel in the aircraft may be at "winter" temperatures and much lower pressure too.

Diesel engines are also available (although not common) for light aircraft, running on Jet A1, which can include a biofuel component.

So the move away from LL100 is already well underway. There's research into unleaded Avgas, but I don't expect that to be a big player. Aviation is very conservative and change-resistant, and there will always be outlier engines that require LL100. And no doubt unleaded Avgas will be even more expensive than LL100, which will just increase the move to Rotaxes, and to electric.

Technofreak

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#2712828 25-May-2021 12:26

Scott3:

Despite the challenges, the do nothing approach is not acceptable given how nasty TEL is.

It took around a decade to phase out leaded fuel for road applications, I imagine a similar time-frame might be appropriate for avgas. Wait much longer than that, and General Aviation may need to skip over unleaded gas completely, and jump straight to Biofuel / Hydrogen / electric...

I have no specific knowledge of general aviation, but as a mechanical engineer have confidence that appropriate solutions will be found with a pressing need.

Apparently some airports in Europe are allreday running UL91 (basically Leadless LL100) with 55% fleet compadiablity.

You give the example of Ethanol fuels not being able to be approved because of seal issues. Seems like something that could be overcome with a upgraded seal system.

Regarding vaporization, In the event that an unleaded avaitaion fuel with appropriate vapor pressure properties can't be found, A pressurized fuel system could be an engineered solution to alleviate these issues.

Regarding octane, engines can be made to run with lower octane by reducing compression via say a piston swap (at the cost of peak power) - which could be made up for with a re power to a bigger displacement... Alternatively in the automotive would, gasoline direct injection technology allow higher compression ratio's to be run on readily available octanes.

Regarding pressurized piston planes, this seems to be a fairly small niche. A quick search turns up that the Piper M350 is the only one in current production. Lycomming engine in this one - that brand is in favor of ditching the lead, but wants a UL100 solution.

With regards to turbines, I don't suggest they will take over all aspects of GA, but if the next piston aviation fuel requires planes be slower and lower, it may make the jump to a turbine more attractive. Of course there is not getting around that they are really expensive to buy and run.

I respect your knowledge and ability as a mechanical engineer but your reply indicates to me that you don't fully understand aviation.

Rather than do nothing aviation has been looking for lead free options for the past 50 years and with some very really focussed efforts over the past 10 years or so. To quote one commentator "Going to the Moon was easy in comparison...... aviation went from being nowhere when lead was phased out of automotive gas in the 1980s and how we have essentially remained right there—nowhere. But not for lack of trying." That trying has included industry heavy weights like BP and Shell.

TEL is nasty but in the big scheme of things the amount of TEL that aviation uses pales into insignificance compared to other nasties that pollute the atmosphere, plus the risk that what ever replaces TEL might be just as bad but we haven't yet had enough time to see the effects of it. There is a case to be made that TEL zealots are using a steam roller to crack a nut.

Whatever is accepted as a replacement for 100LL it has to be a drop in replacement. Something that can be distributed via the existing infrastructure and used by existing equipment.

All of your solutions to make a potential 100LL replacement fuel work add some or all of the following issues, cost, complexity, weight.

Cost it could be argued is a part of doing business.

Complexity affects reliability and safety. Weight affects design limits, payload and performance.

Europe is a very poor example to use with respect to GA. GA is very small (all most non existent in some places) in comparison to other parts of the world. Perhaps 55% of their fleet is UL91 compatible but it also means 45% (nearly half) isn't. As well GA as being small in Europe I think the make up of the types of engines in their fleet is skewed toward the types of engines more suited to the likes of UL 91.
Changing seals sounds like an easy task but on most aircraft, providing there are suitable seals available, changing the seals would be time consuming thus costly.
Pressurising the fuel system adds complexity and weight. Retro fitting such a system to many aircraft would be impractical to nigh on impossible.
Lowering compression ratios and making up power with a bigger engine adds weight, assuming there is a bigger engine available. Increased weight affects the payload. It also affects design limitations with respect to engine mounts and the like and impacts the centre of gravity limitations. When designing an aircraft from scratch most of this can be mitigated, but retrofitting can be another ball game altogether.
Piston aircraft use full power every time they take off and generally cruise at around 75% of maximum power. Reducing the amount of power available for take off affects the take off and initial climb performance figures. All of the data published in the pilots manuals would need to be revised and republished.
Direct injection adds complexity. One of the key features of most aviation piston engines is their simplicity and reliability. They don't need external power to run fancy electronics. Other than feeding in fuel they are a self contained unit. Many critics of the traditional aircraft engine ala, Lycoming or Continental, over look the fact that these "old" engines have a high power to weight ratio and a good BSFC even compared to many modern motor car engines. They are very hard to improve upon. Many people have tried to modify a "modern" automotive engine for aviation use. Pretty well all of them have failed. I am unaware of any that have been able to match the power, reliability, and weight of a traditional aviation engine.
The Piper Malibu 350 may be the only pressurised single in current production (I haven't bother to check) but there are plenty of makes and models of pressurised piston aircraft in use. Yes, pressurisation is a relatively small part of GA but still important. As you're probably aware pressurisation is used in order to operate at high altitudes to take advantage of the better true airspeed that can be obtained with increasing altitude, thus better specific fuel consumption, getting above the weather for a smoother ride, and in many parts of the world (not so much New Zealand) getting above the terrain. Many unpressurised aircraft also fly at these altitudes with the occupants sucking on supplemental O2. In reality turbo charging is the only practical way to get the power these aircraft need.

It's not to say some of your ideas won't happen. It's going to take time. For example. Electronic ignition for piston aircraft engines has been slow in arriving. The magneto systems that have been used are reliable and they are self contained. Because aircraft engines run at basically one speed they get very little benefit, if any, from the fancy advance curves used on automotive engines. The benefits of modern ignition systems are very small but they are now starting to be fitted as OEM equipment.

The same could happen for the likes of direct injection. The very small market that the development costs can be recovered from will mean it will be a slow process. Just remember retro fitting direct injection engines to the largest part of the GA market (that is the existing aircraft) won't be easy or in some cases ever an option if the system cannot be part and parcel of the engine and not require airframe modifications.

One thing to remember is general aviation in the US is larger than the rest of the world combined therefore general aviation on a world wide basis is driven by the US general aviation market. If a 100 LL can be made to work for the US then we will see it. If it cannot be made to work in the US we won't see it.

To sum up.

General Aviation has been grappling with the TEL issue for a long time.
There are some complex issues that still need to be addressed.
For it to work the replacement needs to be "drop in"

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PolicyGuy

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#2712834 25-May-2021 12:45

So what happens when the "TEL zealots" - i.e. the US EPA - Just Say No?
I don't think it will happen before 2025, but I'm pretty sure that it will happen before 2030

Will the world just park up 40% (sheer guess) of the GA fleet?

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#2712860 25-May-2021 14:10

The EPA could have easily acted by now. Either they are being pragmatic about the aviation TEL issue or there is political pressure being brought to bear.

My reference to TEL zealots was more in relation to environmental lobbiests than the EPA.

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empacher48

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#2712863 25-May-2021 14:17

PolicyGuy:

So what happens when the "TEL zealots" - i.e. the US EPA - Just Say No?
I don't think it will happen before 2025, but I'm pretty sure that it will happen before 2030

Will the world just park up 40% (sheer guess) of the GA fleet?

Nope, they won’t just park it up. But the time frame will be pushed out.

Having worked in flight test for a very minor STC for a large GA twin turboprop, a process that took 7 years and $450,000 to go from “this is a great idea” to approval. A change to engine type/fuel system/fuel type would start at 7 years and then go up from there.

One if the largest number of aircraft produced was the Cessna 172, with some 20,000+ still flying today, an engine change and new fuel system, if approved, would cost an owner around $40,000. If you want to buy a brand new one from the factory you’re looking at USD$375,000. Most GA aircraft owners won’t pay that for a brand new plane, so a change of engine is required. If you want it change from piston to turbine, I’ve seen a Soloy Conversion for a Cessna 207 at USD$1.8Million, turbine engines are very, very expensive for GA.

As for electric and batteries, until the range of an electric airplane is the same as a gas powered airplane (5 hours would be reasonable) and the weight of the motor and batteries are equal to or less than the gas powered, then forget about it. Payload in small aircraft is the most important factor.

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#2712896 25-May-2021 16:01

I agree generally speaking with @Technofreak & @empacher48.

The whole STC system is what makes the industry so conservative. It costs an absolute fortune (and many years) to make a change, so changes don't get made. The microlight and homebuilt sectors are *much* more innovative than GA, which is why Rotax-powered microlight/LSA aircraft are wiping out the Lycoming-powered C150s. If we look at, for example, the idea of E10 fuel... lets assume that a Lycoming will run on it just fine. So we need to replace seals (and maybe entire fuel tanks, which in turn might be a structural part of the aircraft). But all of those seals have to be tested and approved, because, unlike cars, if the fuel all leaks out it's going to be very expensive and very dangerous.

Five hour range is more the exception than the norm in GA... 3-4 hours would be more typical.

But, for training, (and a lot of GA flying is training), a flight of under an hour is typical. So a fast-charging system might be acceptable for that. Start off with a 3-hour battery, fly for 45 minutes, charge for 15 minutes. Even with current technology, you could probably get through a day like that, with a couple of gaps in the schedule. Or a quick-change battery pack.

Scott3

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#3067356 23-Apr-2023 13:44

Now two years later, Little has happened in NZ, but there are some movements overseas

Things that have happened:

NZ has got it's first electric (full size, manned, nonexperimental...) plane in November 2001. Still the only example here. Pisistrel Alpha Electro. Aircraft is clearly targeted at the training market. 90mins flight (allowing for 1 hr training flights with a 30min reserve). Less than a 1hr recharge time before it is good to go again.
Santa Clara County, California has banned the sale of sale of 100LL at it's county-sponsored airfeilds, meaning the fuel is no longer available at Reid-Hillview Airport in San Jose and San Martin Airport in San Martin. Ban does not impact an nearby airport in the county which is not county sponsored (KSJC)
https://www.flyingmag.com/100ll-ban-takes-effect-in-santa-clara-county/
https://www.globalair.com/articles/california-county-that-banned-100ll-to-be-first-in-faa-lead-free-transition?id=5552
In the USA, the Eliminate Aviation Gasoline Lead Emissions (EAGLE) initiative has been launched, proposing leaded aviation fuel be eliminated by 2030. Long list of powerful backers, including the Aircraft Owners and Pilots Association (AOPA)
https://generalaviationnews.com/2022/02/24/initiative-to-eliminate-lead-from-aviation-fuel-by-2030-takes-off/
https://www.faa.gov/unleaded
Washington State has a bill proposing to phase out 100LL from 2024, ending in a statewide ban in 2030. It is opposed by General Aviation advocates. Groups like the AOPA's opposition seems more to do with the details of the phase out, as opposed to the 2030 ban, which they are committed to.
https://www.aopa.org/news-and-media/all-news/2023/march/16/aopa-fights-back-on-washington-state-bill-banning-100ll-sales
USA EPA has proposed to declare aviation lead as a public health danger
https://www.reuters.com/business/aerospace-defense/us-epa-proposes-declare-aviation-lead-emissions-public-health-danger-2022-10-07/
FAA has authorized fleet wide use of an unleaded fuel for engines that require 100 ocatane:
https://www.flyingmag.com/g100ul-avgas-replacement-set-to-soon-hit-pumps/
Europe is moving to ban TEL. Expected to be some kind of exception for 100LL (perhaps importing it to Europe premade), but could well make 100LL less available and more expensive.
https://flyer.co.uk/europe-moves-to-ban-lead-in-avgas/
https://eur-lex.europa.eu/eli/reg/2022/586/oj

It is true that I know little about aviation, but I don't feel any industry should be given a free pass to continue to emit in perpetuity such a nasty chemical as TEL, because the alternatives are hard / expensive.

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Technofreak

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#3067363 23-Apr-2023 14:00

Scott3:

Now two years later, Little has happened in NZ, but there are some movements overseas

Things that have happened:

NZ has got it's first electric (full size, manned, nonexperimental...) plane in November 2001. Still the only example here. Pisistrel Alpha Electro. Aircraft is clearly targeted at the training market. 90mins flight (allowing for 1 hr training flights with a 30min reserve). Less than a 1hr recharge time before it is good to go again.
Santa Clara County, California has banned the sale of sale of 100LL at it's county-sponsored airfeilds, meaning the fuel is no longer available at Reid-Hillview Airport in San Jose and San Martin Airport in San Martin. Ban does not impact an nearby airport in the county which is not county sponsored (KSJC)
https://www.flyingmag.com/100ll-ban-takes-effect-in-santa-clara-county/
https://www.globalair.com/articles/california-county-that-banned-100ll-to-be-first-in-faa-lead-free-transition?id=5552
In the USA, the Eliminate Aviation Gasoline Lead Emissions (EAGLE) initiative has been launched, proposing leaded aviation fuel be eliminated by 2030. Long list of powerful backers, including the Aircraft Owners and Pilots Association (AOPA)
https://generalaviationnews.com/2022/02/24/initiative-to-eliminate-lead-from-aviation-fuel-by-2030-takes-off/
https://www.faa.gov/unleaded
Washington State has a bill proposing to phase out 100LL from 2024, ending in a statewide ban in 2030. It is opposed by General Aviation advocates. Groups like the AOPA's opposition seems more to do with the details of the phase out, as opposed to the 2030 ban, which they are committed to.
https://www.aopa.org/news-and-media/all-news/2023/march/16/aopa-fights-back-on-washington-state-bill-banning-100ll-sales
USA EPA has proposed to declare aviation lead as a public health danger
https://www.reuters.com/business/aerospace-defense/us-epa-proposes-declare-aviation-lead-emissions-public-health-danger-2022-10-07/
FAA has authorized fleet wide use of an unleaded fuel for engines that require 100 ocatane:
https://www.flyingmag.com/g100ul-avgas-replacement-set-to-soon-hit-pumps/
Europe is moving to ban TEL. Expected to be some kind of exception for 100LL (perhaps importing it to Europe premade), but could well make 100LL less available and more expensive.
https://flyer.co.uk/europe-moves-to-ban-lead-in-avgas/
https://eur-lex.europa.eu/eli/reg/2022/586/oj

It is true that I know little about aviation, but I don't feel any industry should be given a free pass to continue to emit in perpetuity such a nasty chemical as TEL, because the alternatives are hard / expensive.

At the present time there is no alternative. Banning leaded avgas will wipe out operations that use piston engined aircraft. I would suggest that while the effects of TEL aren't good you have to take into consideration how small the aviation contribution to the pollution caused by TEL is and the benefits provided by that aviation activity.

Unfortunately there are some groups of people who will nevet accept compromise. Everything we do has an impact sometimes negative even though there is an overall benefit but because there is a negative impact some people will want it banned.

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SomeoneSomewhere

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#3067384 23-Apr-2023 15:24

If the FAA is certifying a new fuel as a drop-in replacement without need to certify every engine/airframe type individually, that sounds like a pretty good alternative. Granted, it's still a few years out to hit actual mass production.

Is there an overall net benefit? If there is, could that benefit be retained by restricting the use of TEL-containing fuels to only circumstances where both the activity (e.g. medevac, crop dusting, not sightseeing or holidays) and the use of 100LL (i.e. no other fuel available for aircraft, no other aircraft is suitable) was essential?

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#3067601 24-Apr-2023 12:18

Technofreak:

At the present time there is no alternative. Banning leaded avgas will wipe out operations that use piston engined aircraft.

Not all piston engines... Rotax recommends using 95 mogas (ordinary car petrol). They're very widespread in 2-seat aircraft. Whilst in the past they have only made 80 & 100hp engines, they've recently announced the 916is at 160hp which I expect will over time take a chunk of the 4-seat light aircraft market. Rotax's progression towards larger engines is clear, and will take out Lycoming and Continental eventually.

One difficulty with using Mogas is that it's not available at airfields, partly because there's more demand for 100LL (kindof chicken-and-egg), but also partly because it's less stable than 100LL so goes stale quicker, so fuel can't be left in the tank for as long, so requires lots of small replenishments.

frankv

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#3067617 24-Apr-2023 13:18

SomeoneSomewhere:

If the FAA is certifying a new fuel as a drop-in replacement without need to certify every engine/airframe type individually, that sounds like a pretty good alternative. Granted, it's still a few years out to hit actual mass production.

Is there an overall net benefit? If there is, could that benefit be retained by restricting the use of TEL-containing fuels to only circumstances where both the activity (e.g. medevac, crop dusting, not sightseeing or holidays) and the use of 100LL (i.e. no other fuel available for aircraft, no other aircraft is suitable) was essential?

FAA is pretty much the definition of slow, possibly only surpassed in slowness by the CAA.
If the FAA is going to approve a new fuel as a drop-in replacement for 100LL, then it (rather than individual engine manufacturers) is going to have to test every engine type individually. I don't see that as better or even speeding anything up. Also, there's the issue of fuel system components. For example, ethanol, contained in some fuels as an octane booster, can react with fibreglass (which some fuel tanks are made of) and other kinds of plastics that may be in valves or connectors. So you also have to test your new fuel against every valve and connector and filter and so on before you can declare it to be safe.
I don't know about excluding sightseeing... that's a huge part of some aircraft operators' incomes that you're going to cut out. Medevac, at least in NZ, is largely turbine-powered, so not using 100LL.

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