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.
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)_/¯
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
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.
They are, however, manuals and documentation for US market vehicles will be specified in AKI (aka '(R+M)/2') regardless of who manufactured them. Some manuals also specify both AKI and RON, and that can be a source of confusion.
I'm in Europe and here it would be "98 recommended, 95 allowed with possible degradation in performance", as it's the case for my 2006 car. More modern small volume turbocharged engines should be even more sensitive to octane number due to higher compression ratios than common American engines of twice the volume for the same horsepower. The engine ECU will reduce boost pressure and fuel charge based on feedback from the knock sensor.
California 'gas sucks' for a couple reasons which are easy to miss if you're in California.
1) Few refineries make it, so it's MUCH more expensive. But if you're living in California, it is easy to miss because EVERYTHING is much more expensive.
2) Mileage is generally poorer, due to the mandatory ethanol mixes. But some places also usually mix in ethanol, and the difference is usually in the 10-15% range. So unless you have a good A/B comparison going, it's also easy for it to blend in with all the stop and go driving, and terrible road conditions.
3) Mandatory Ethanol means generally very poor storage characteristics. Which considering how much driving happens in California (and how dry the climate is in the populated areas), most people won't notice.
So does it suck? Comparatively, definitely! Is it likely to be noticed unless you're very aware and have experience with other options? Nope.
I understand that additionally in some vehicles (not necessarily aircraft) predating ethanol dilution the evap systems may begin to malfunction at high elevation and temperature due to the lower initial boiling point of ethanol.
In the case of my vehicle it results in low/rough idle and positive fuel tank pressure which otherwise do not occur either at lower elevation or with ethanol-free fuel at elevation.
Once you've replaced those valve seats with hardened ones, you don't have to worry about adding lead substitute in every fill up. You do still have to worry about getting the right oil additives though, as the old flat tappet engines need more zinc than modern oil blends have in them. Ethanol in the gas is also a concern, but any conscientious classic car owner has hopefully replaced all the rubber and plastic bits in the fuel system to ethanol safe ones.
I think (don't really know) alloy steel valves and hardened seat were pioneered by the aircraft industry and appeared in cars by the 1950's. So really lead wasn't needed to extend the life of valves after that. Also my experience with some shitty 1960's cars was the valve guides would wear out before the seats. Compression is fine but engine burns oil and fouls the plugs. You could see it with older cars when going downhill, they'd be blowing oil smoke.
No idea about 240z specifically, but at least things designed for sustained high performance (like aero engines) tend to use valve seats made from some wear and temperature resistant alloy like stellite or brightray.
Legally, they need to run a fuel which is approved on the type certificate data sheet for their engine (and the engine-airframe combination).
The recently developed G100UL unleaded fuel requires a change to the type certificate of the airplane (by serial number) and engine(s) (by serial number) to be legal.
Until that supplemental type certificate existed, these airplanes did legally need leaded fuel.
No, G100UL is a full drop in replacement that meets the standards off AVGAS which is what is required by the certificate. Fully legal on all engines with no change to the certificate.
It does not meet the composition standard of 100LL, which is why you need to buy an STC (Supplemental Type Certificate) from GAMI to use it legally in an aircraft. (It is a drop in replacement from a performance point of view, but does not meet the original type certificate fuel standard.)
I would imagine that the gelling problems ethanol can sometimes cause in automobiles is magnified when used for aircraft due to the thermal dynamics present in aviation (the temperature drop while in-flight) that aren’t a factor for most automobiles. That’s just my intuition, I’m sure there are better informed people here who know better.
Yup, also, there are specific chemistries used in some composite wet-wing designs that can be damaged by ethanol. It's the final reason I became less interested in the DarkAero 1 while following its development.
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.
>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
Except none of that can be used until someone goes through the millions of dollars to do all the design work, safety testing, and mountains of FAA paperwork. Oh, and take on the liability of a mistake killing a bunch of people.
In the mean time, rebuilds have to meet the existing design. Which has specific standards.
It's not like Cessnas themselves can't be wildly improved on in general!
As an old Boeing engineer friend of mine used to say 'when the weight of the paperwork exceeds the gross weight of the plane, it will fly.'.
1) Regulations (vehicle fuel comes from sources/supply chains generally not willing to do the paperwork)
2) Lack of solid quality control relative to aviation fuels (see #1)
3) Power to weight ratio matters a LOT in aviation, and aviation engines run at typically far higher elevations for at least part of their flight time. So aircraft engines generally push things harder, have higher compression, and can be damaged more easily with 'junk' or contaminants.
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.
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...
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.
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/) 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.
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.
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.
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.
> 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.
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.
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.
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.
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?
Because pollution is an externality cost that the market does not take into account. The only way to solve it is with regulation. These regulations are justified on the basis that it is wrong to poison others, or pollute their right to shared public resources.
Regulation does not solve externality problems. It makes them worse. For example, the government's increasing regulatory requirements for ethanol in fuel (of which this is an example) cause food to be more expensive and have caused food shortages (because corn is grown to make ethanol instead of for food). Yes, air pollution is a concern, but people who are starving for lack of food don't live long enough for air pollution to be a health concern for them. And nobody asked them whether they were OK with the government making that tradeoff.
The vast majority of regulations don't work. At least not if your definition of "work" is to actually solve market externalities. But they're great for job security for regulators and politicians.
> The market can never solve market externalities, by definition.
This is not correct. Markets can solve externalities, through market transactions that shift ownership so that the externalities are internalized. The main thing preventing this is government regulation that raises transaction costs so that the necessary adjustments cannot be made. This has been known at least since Ronald Coase published his famous theorem.
In other words, government regulators prevent markets from solving externalities, and then complain that markets can't solve externalities so government regulators have to step in.
It's true that there are cases where there are no market transactions that can internalize an externality. But in those cases, regulation can't solve them either; there are no solutions for such cases. Welcome to the real world.
An industry that fails to regulate itself is regulated by the government. We've had more than a decade to transition and literally zero progress. Everyone knew this day was coming since congress mandated the transition back in 2009. Crying about it doesn't solve anything — it's well past time to rip off the bandaid.
Anyone commercial already has to go in for 100hr inspections all the damn time. The STC is unlikely to cost much relative to that, nor to add much additional hassle.
Anyone private can deal with it, they own their own plane and knew it wasn’t going to be a cheap hobby going in.
G100UL will cost a bit more than 100LL but it seems likely this will change a bit as it becomes more widely used.
I guess it puts people operating midcentury radials that haven’t yet been certified for G100UL in a weird spot.
>Will I have to modify my engine or aircraft to use G100UL avgas?
>Other than placards, no modifications are required. A small placard is attached to the engine and "stick-on" placards are applied to refueling ports. In addition, there is a short POH supplement added to the AFMS.
Beautiful. The main sticking point was the (possible) need to re-certify existing planes. This is peanuts in comparison; probably why it took so long for such a fuel to get developed and approved.
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 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-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 . 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.
They’ve also been known as a class as a problem (along with catalytic converter particles) for well over 30 years.
There have been multiple studies linking proximity to freeways with asthma and decreased life span, serious health issues like COPD, and even significant increases in sudden unexplained deaths.
45 million Americans live within the high risk zones (300 feet or meters, I forget), countless new daycares, old folks homes, and residential high rises get built there every day, and almost every American is exposed significantly due to being in vehicles on average of an hour a day with insufficient filtering.
The issue here isn’t that aircraft engines last ‘decades’.
It’s that aircraft owners are only legally allowed to use fuels approved by the FAA for their aircraft, and per the various authorizations for their aircraft. Which vary. The engines may get rebuilt, but without a very expensive type change and approval (often from the manufacturer) they’re the same design as the original. Which has the same limitations.
So until there is a viable authorized replacement (per the FAA), literally they can’t use it except in emergencies. Which only just became available. And they can’t change engines either. And they can’t just YOLO it legally.
Because fuel is a major cause of crashes that kill people already (usually contamination, or wrong fuel causing engine failures/flameouts).
And despite the FAA knowing of the risks of lead (or more precisely, knowing the various factors), they only recently did authorize a replacement.
So it’s as if that study on those plastics happened 30 years ago, and we’re just now getting around to it. Which essentially is what has happened with cars and the various pollution.
So raking anyone over the coals when a far larger, more damaging, and widespread crisis has always been going on for even longer and gets ignored? Yeah I’m pointing out the hypocrisy.
It’s always about resources in proportion to risk, and arguably the FAA has dumped far more resources and mitigated a far less damaging risk (in many concrete ways) far faster with this leaded fuel issue than one near and dear all of us.
> There have been multiple studies linking proximity to freeways with asthma
Which also drives the call to reduce car use, wherein someone is also likely to point out that driving is not a right but a privilege.
> So it’s as if that study on those plastics happened 30 years ago, and we’re just now getting around to it. Which essentially is what has happened with cars and the various pollution.
Yes. And lead wasn't banned for interior paint until decades after some other countries. The US regulatory system is strongly weighted in favor of business over health and environment.
> raking anyone over the coals
As if! This is finding. The EPA must then "propose and promulgate emission standards", which the FAA must then turn into regulations.
It sets no deadlines, it makes no policy changes other than for the EPA and FAA.
I suspect it will take years before the first regulations appear, and with years to allow a changeover.
In the last 60 years the government and the FAA have killed civil aviation for anyone that isn't obscenely rich. This environmental bullshit is just one more way to keep the plebs out of the air.
Good. It's nothing but a rich boy hobby anyhow. And anyone who can afford, or even has a pilots license these days is getting paid well over 6 figures, usually as entry pay. The days of underpaid, entry level pilots are a thing of the past. This isn't the 1990s. Grow up.
Many (older) aircraft engines need leaded fuel.