Organic chemist here. Hydrocarbon combustion is a free radical chain reaction. Free radicals are molecules that have an unpaired electron. Oxygen is a di-radical that abstracts a hydrogen atom from a hydrocarbon to start the chain reaction producing a hydrocarbon radical. Molecules that have high octane numbers produce more stable, lower energy and less reactive radicals during the combustion process. A carbon atom with other carbon atoms attached to it will produce a more stable radical compared to one with more hydrogens attached. This is why a molecule like isooctane is so good and n-hexane is bad. Benzene rings also help stabilize radicals which is why toluene and xylene are good octane boosters. More stable radicals slow the combustion down without decreasing the energy output. The chemistry is similar to that of food preservatives like BHT which retard oxidation of food by breaking the free radical chain reaction with a stable radical which cannot continue the radical chain reaction.
GTL, Gas-To-Liquid natural gas to gasoline patent by TAMU professor had 100 octane with no impurities, eliminated "flare" of low yield wells impractical NG
Is it the”-OH” group of alcohols that make them octane boosters? Or is it the latent heat of vaporization which cools the air-fuel mixture? I suspect it is both.
@@tonycook1624 why is it that I've never heard of liquid oxygen mixed with kerosene as an explosive? There's panclestite that uses nitrogen tetroxide, I've heard about using charcoal and lox, but never kerosene and lox. Do they not mix?
Situation: There are 14 competing fuel types. 14? Ridiculous! We need to develop one universal fuel that covers everyone's use cases. Situation: There are 15 competing fuel types.
Three fuels for the Airlines under the international sky. Seven for the Airforces in their hangars of stone. Nine for General Aviators doomed to crash ! One for the Dark Lord on his dark throne. In the land of Texas where the rockets fly. One Fuel to rule them all, One Fuel fo drive them, One Fuel to bring them all to Mars and in the red sand Bind them In the land of Texas where the rockets fly.
You know there’s a guy with a Piper Cub without an electrical system who flies 10 hours a year and spends the rest of the time petitioning FAA against mandating ADS-B and unleaded fuel.
I will never understand the ADS-B thing. "I don't want the gubment knowing where I go" Man the government doesn't care what you do with your Cub buddy. Unless you're flying questionable or illegal. Imagine turning down significantly increased situational awareness cause you have main character syndrome.
@@jarrettleto I almost met that guy at 700 feet on final approach. me, after doing all the radio calls and patterns for an uncontrolled airport, him in his black-painted Zenith with no radio, calls , or situational awareness. Talked about him once we got on the ground with the locals - "Oh yeah, that's just Billy-Bob, he does that all the time" Starts his plane at the T hangars, rolls straight to the runway without a runup, blasts off no matter the wind direction.
@@TylerCMilligan american history calls you a liar, your government had many uses in their time for information regardless of you doing something shady Also something going illegal and making it A-OK in hindsight has been used at times too Bottom line, dont make up a astrawman if you cant even defeat it cleanly 🤣
Yes, but they were even before 100 LL. Probable solution is more like the rotax that run on anything autogas, or the diesels that run on JP-4 STC'd into planes at their next engine rebuild. The STC process would need to be improved. Currently Rotax is a little shy of HP, for mid sized and larger engines, partly offset in some models by turbo normalizing, and has an extra maintenance expense with a need for gearbox inspections/overhaul. Diesels are heavier, usually turbonormalized, with the extra weight partly offset by lower weight of fuel.
@@michaelmcmullen354 The current 100LL contains much less lead than these engines were designed for, and is about the minimum that can be gotten away with.
Yep. Might as well ask why they use magneto ignition and carburetors. A typical 4 cylinder Lycoming is going to give you what, 150-160 HP out of a 320cu engine, costs about $50,000 new and is largely unchanged for the past 70 years. I get it, change is difficult and certifying a new engine is expensive, but cars went to fuel injection and electronic ignition because it is more efficient, more powerful and MORE reliable than carburetors and magnetos. I know a lot of pilots and personally know three that have had catastrophic engine failures (fortunately with safe dead-stick landings). These are not more reliable "tried and true" designs. They are dangerous and obsolete, riding the coat-tails of certification that was done 75 years ago.
@@DragNetJoe You seem to be forgetting that while fuel injection and electronic ignition have been available in cars for a long time, it is only recently where they exceeded the overall reliability of the technologies they replaced. And when those vintage engines fail, it is almost always a maintenance issue and not a design issue.
@@rockets4kids Sure, if you use the worst possible fuel injected engines as an example. Mercedes have used injection since 1970. The whole 'reliability' angle with old airplane engines is a myth. Remember that the maintenance in airplane engines is rigorous for a reason. It's just money sink for plane owners.
Fun fact, 100LL contains more lead than leaded automotive gas ever did. Aside, there is the “Research” method for measuring octane rating and the “Motor” method. One advances spark timing and the other increases compression. North American gas stations use the average of the two, hence the (R+M)/2 note on the pumps. Other countries may calculate it differently and so have different labels for a similar product. Another fun fact: when NASCAR switched to unleaded there was an easily detectable increase in school test scores around the tracks.
@@Broken_robot1986 Seemed to fulfil all "fun" criteria for me in the fact department. Statistically significant rise in test scores with no likely alternative explanation? If one is controlling and calibrating for distance from a NASCAR track, it is an excellent proxy for actual causation. Researchers do this all the time for other environmental contaminant factors.
Funny story: one of my chemistry lab mates in grad school ran his $1000 car out of gas. His solution was to swipe a gallon safety can of n-heptane from the lab and fuel up with that. Even when I explained to him that n-heptane was by definition zero octane he still didn't get why his car wouldn't run.
In the 1870's the fraction of crude oil called "gasoline" was a useless byproduct and the standard oil company just dumped it into the river by their refinery. So much gasoline was dumped into the river that sparks from passing steam boats would set the river on fire.
Glad to see you bringing attention to this issue. I've been as vocal as I can be about tetraethyl lead since I got my A&P license at the age of 19. As pilots and mechanics, we are hurting ourselves the most with 100LL. We need to get the lead out. Mogas STCs have been around for decades. G100UL is proven now. It's time for us to be good stewards to our neighbors and ourselves.
I'm all for getting rid of tetraethyl lead, but G100UL has been shown to be far from the "drop in replacement" that GAMI said it would be. It seems to enhance fuel bladder deterioration causing fuel leaks and causes rubber o-rings to swell and deform. The STC method GAMI chose for certification is far from ideal for an aviation fuel.
@@Fang70Leaks on 30 year old fuel bladders are common regardless of what fuel you put in them. The main difference is that the leaks stain more with the GAMI fuel. Any GA A&P with more than a few months of experience can tell you, patching and replacing fuel bladders is not a rarity.
@@samsonsoturian6013Because everything that needs to be said technically has been said. This is not a technical problem. It's a problem of political will. I'm pleading with you, as someone who is directly affected by this when I have to go back to work on Thursday, help me find the political will to fix this. Help me give a better world to our neighbors. Help me leave a better world for our children. Help me make a better world for myself. I love aviation, and I love that when I open the door to work, there's an airplane right there. Do I deserve to be poisoned for that? Modern mogas is perfectly fine for ~70% of aircraft out there, and for the few high performance twins that need 100LL, they can have their timing reduced and suffer a performance hit to run fine on mogas, or they can use G100UL. There are so many viable technical solutions. It's just a problem of political will.
I talked to an FAA guy who worked on the EAGLE team at OSH a couple years back. He 100% agreed that the real reason why we don't yet have a general 100LL replacement is the goldilocks attitude of the FAA: they can make a fuel that works for 99% of the fleet, or a fuel that can't be mixed with 100LL and/or needs a different mixture, but not one that is 100% compatible. I personally believe that 99% should be just fine.
@@sncy5303 it's not the FAA it's the GAMI/SWIFT groups making alternative fuels and licensing their formulas for unreasonable money. That's why no one can come to an agreement. meanwhile Philips 66 100 LL is cheap and simple to cook.
@@christiannorf1680 The real "big boy" regulations are EU territory anyway. German bureaucracy is more like banning "dirty" wood burning stoves, excluding models that got installed pre 1995 and post 2010, also excluded are stoves where the tenants are over 70 or are living there for more than two year.
@@cyan_oxy6734 Heh, yeah. Declaring exceptions from exceptions, which come into play unless the exception from the other exception is met. And don't you even think about making anything in between digital. Regarding the EU regulations, I don't know. Maybe I just missed it, but they seem pretty straight forward. Like "All mobile entertainment devices shall have a USB-C port for charging, period."
The problem isn’t it just working for 99% of the fleet. It’s also them refusing to let the 1% affected to change their planes to use the new fuel. Because that engine from the 60s is obviously much safer than a new engine design in that plane. However, jump through a few hoops and pay a few fees and you’ll get a waiver somewhere along the way.
Clair Patterson discovered high levels of lead in the environment back in the 40s when they were messing up his geological dating methods. He went on to create one of the first clean rooms and his campaign against lead poisoning lead to a quicker phaseout of leadded fuels for cars. His story is a very interesting read. I remember the tail end of leaded fuel from my childhood when there were still leaded and unleaded gas pumps at gas stations. But I wasn't aware of the effects until a few years ago.
@@buck6365 And you can bet thar alot of their findings were overblown, a classic example of that was the EPA's ridiculous claim of second hand smoke causing cancer, their math was so skewed and their figures so ridiculous that the Supreme Court actually made them withdraw their claims and remove their numbers from their official records and literature (they conveniently moved a decimal point over a few numbers), of course that was AFTER the medical industry and lawyers already got their billions in settlements based on those statistics.
Part of the story is the extraordinary lengths the companies went to shut him up. Law suits, burglaries, physical intimidation, blackmail attempts, marketing campaigns to discredit him as a crank - the lot
Hey Scott, Good video. I'm an engine re-builder. Your later theory about differing octane is what our industry currently accepts as the reason why unleaded fuels cause valve-seat recession. Detonation doesn't always cause engine knock, but can still be putting excessive force on the piston. It also causes a combination of carbon fouling and temperature corrosion on the other components of the chamber. Basically, the temperature climbs high enough to soften the metals, and carbon sediment on the seats is being hammered by the valves, causing pitting and errosion. Any time our clients inform us that an engine will be switching to unleaded fuel we have a mandatory procedure that includes replacing the valve seats with hardened inserts. We also often recommend stainless-steel valves for similar improvements in longevity. I also believe our engine builder usually recommends adjusting the cooling system at the thermostat to open at a lower temperature to keep up with increased temperature load.
I'm more likely being ridiculous here but I just thought is there any chance that nanodiamonds could be created by the exhaust valves slamming into the carbon sediments on the valve seats combined with high temperatures thus causing accelerated recession of the seats😅?
Thomas Midgley who played a major role in developing leaded gasoline was also involved in developing CFCs. Even though lead was known to be toxic he insisted it wasn't.
Fun fact, the chemical used to replace CFCs degrades into a PFAS type compound, and is now the largest source of PFAS pollition in the environment, which is bioaccumulating everywhere.
As a new A&P mechanic, Leaded fuels is the primary reason why I chose to stay out of GA and focus on turbine aircraft operating under part 135. Fantastic video, Scott. Thanks for the in-depth chemistry analysis.
@@aeromatt GA has stepped up their rates recently because they can't find anybody who wants to work on a 50 year old clapped out Cessna with AutoZone parts on it.
Lots of farmers in Australia own light planes in order to conveniently and quickly visit large towns and cities. Many of them run their planes on 98 octane retail gasoline meant for cars, as it is available everywhere, and farmers buy it in 80 litre drums for their cars and farm equipment. Toluene is the additive used to obtain 98 octane rating. It is illegal to use car gasoline in aircraft, but aircraft engines run on it just fine. In theory, aero engines run on car gasoline could have high valve seat wear, but farmer-owned planes don't clock up anywhere near enough hours for it to matter. Cessna stopped making 152's and 172's in 1985 but considerable numbers are still registered and flying. The main differences between car gasoline and avgas is the use of tetraethyl lead instead of toluene to achieve the required octane rating, the absence of various proprietary additives to reduce wear that is used in car gasoline, and manufacture of avgas to higher quality standards to ensure purity, absence of ash, etc.
The exhaust valve wear is definitely a thing in cars, especially forced induction, but even then an old Mitsubishi for example will reach 250,000km before valves need a look
@@spannaspinna I was talking about the Cessna 172 popular with farmers. Most would have the Continental engine. I doubt a typical farmer would bother with supplemental type certificates. They are a pretty go-ahead-and-do-it mob who dislike what they see as government red tape and taxes. Last I heard, using car gasoline was just not permitted - an STC is not applicable.
I've lived on my estate in semi rural North Cheshire UK since 1975 and before lead was banned the roof of every house was clean as a whistle. Since the ban every north facing roof on the estate is caked in moss and its an annual chore to get the scaffolding platform out and scrub it off by hand! Now we know what impact the lead was having in the flora, what was it doing to our lungs as kids?
4:04 Scott, the shock wave breaks through the boundary layer of gas on items like the piston, cylinder bore and head. This then exposes them to the full temperature of the combustion process. Aluminium heads and piston crowns would typically melt at normal combustion temperatures, but are protected by those boundary layers of gasses. Pinging/knocking is the sound of the these violent combustion events and the damage can be very quick if not attended to immediately.
I somehow thought knocking was a premature ignition that was disrupting the smooth run of the engine, not the combustion turning into a detonation. Now I'm wondering where I got that from, because the explanations of why it's bad and why high octane helps with that pretty much line up 🤔 Is there a specific term for premature ignition?
@@christiannorf1680 Knocking _is_ premature ignition, wherein the fuel detonates during the compression stroke before the piston reaches top dead center and the spark is initiated. Premature ignition by other means is simple called "bad cam timing".
That's right. My professor in mechanical engineering told a story where he destroyed a motorcycle engine within two combustion events where knock occured, when he was tuning the engine that he developed at Rotax. (It's the Rotax engine for the Aprilia RSV Mille, for those that care). So at full tilt, 10.000 rpm, that's four revolutions, so 0.02 seconds. It takes 0.02 seconds to destroy an engine with knock.
I recall hearing that changing a simple hose from rubber that'll last a year or two to silicone that'll last a decade+ resulted in planes being flagged as "experimental" ditto for tires using modern better materials. Aviation seems intent on not advancing.
Yeup. Gotta get an STC or a field Modification 337 form done. And it’s worse, you’re not experimental, you’re non compliant with the Type Certificate. Meaning not airworthy at all because the part isn’t the specifically called out certified part. IF you can get your Certificate switched to experimental you could do it. But the FAA is LOATHE to allow planes to go Experimental because it takes the power of their regulation away since they can’t force Type Certificate compliance on Experimental. They think it will become a lawless hellscape. Unless you build the plane yourself, then it’s fine as an amateur built experimental. I guess because if you can cut drill and rivet you’re somehow magically more competent?
It’s by design. Same reason Nuclear power is so expensive. The government loves to assert power even when it’s nonsense and always gets stricter in regulation.
Thanks for a great video on this subject! I have the G100UL STC for my plane, and I was at Reid-Hillview on the day that sales began to buy a tank of the fuel. It works great. There are a lot of vested interests doing their level best to sabotage and undermine G100UL, and to spread disinformation about it. The paint thing is just one example: George has shown pictures of painted aircraft parts literally soaking in buckets of G100UL. It doesn't hurt the paint, assuming that the paint is not already about to fall off in the first place. The FAA should have found a way to do a blanket approval of this fuel and be done with it.
@@jimhayes2786That’s a whole other issue in GA of absolute shit repaint jobs that cost a fortune, usually done by the barely qualified in shops without proper or any disposal permits. When the only people left in General Aviation are the sociopathically selfish rich, it’s enshitification at every turn.
Wow. Who'd have thought a 30 min video on petrol would be interesting enough to keep my attention the entire time. Well done, Scott! Happy New Year to everyone!
Very interesting, Scott, walking in the path of legendary Paul Bertorelli! Over here in Germany we have MoGas quite readily available; at least at those airfields I am allowed to use in my flight school. Further, all of our C172s have that MoGas STC done. Please keep the aviation content coming and Happy New Year to you!
Paul Bertorelli has retired from AvWeb, but one of the big pushes he did in the last part of his journalistic career was covering unleaded GA fuel and why it wasn't happening. Might want to watch some of his videos on that.
One thing you didn't mention about regular car gas is ethanol likes to bond and adsorb water. This leads to long term storage issues and operational issues with aircraft engines. One of the best things about 100LL is it is super stable. You can have it sit in a carburetor for well over a year with zero issues. Try doing that with anything that has ethanol in it.
Here in Minnesota it’s pretty easy to get 91 Octane non-ethanol gas. This is actually the best fuel for many small engines such as chainsaws, lawn mowers, marine outboards, etc. I do feel like it was less common in California, but it’s great if you can find a convenient located source of non-ethanol gasoline.
It’s less common in CA because the Ethanol also acts as an oxidizing detergent and reduces some emission byproducts. Not a big deal in Minnesota, but bigger deal with 5x the population per square mile.
I know your guyses octane numbers are lower but here in Germany you can aswell get 102 octane lead free, ethanol free gas. I like to use it when I have to store my vehicle for a few months.
@ yes you're buying what in the US would be 93-95 octane. We have it here for boats and race cars. Most Regular gas stations don't sell it because without the ethanol subsidy it's like $2 a Liter more.
Yeah it’s common in many northern climates. I think under some federal regulation it’s actually a carve-out for snowmobiles! But I agree, very useful for small engines like lawnmowers and such.
As I understand it, Ethanol-free gas would actually be cheaper than modern 10-15% E-gas if government subsidies for Corn Ethanol (the predominant source of fuel Ethanols, afaik) were to vanish. Corn Ethanol, considering only commercial factors and absent subsidy, runs about 9 dollars a gallon last I checked. Adding in Ethanol to gasoline, therefore, feels like a well-meaning government program based on some misunderstandings and false premises. If we really wanted a renewable combustion fuel, Ethanol is one of the worst candidates.
Ethanol is an excellent additive to raise AKI. Except Brazil and some countries in Europe, Ethanol will remain an additive or base for racing fuels. HVO is better candidate and retro compatible with every diesel engine and zero sulfur and phosphate component promoting a cleaner burn
there could be fuels hypothetically produced in ways that relate to the current biological production of ethanol, but there's no indication that the current production of ethanol is getting us any closer to that. Currently, the production of ethanol does nothing to advance technology in a meaningful way and only serves to hinder progress and create incentive to lobby against the funding of potentially disruptive research on sustainable combustion fuel.
31:31 So, aviators who don’t want to poison the environment are a “niche market”? This is bigger than aviation fuel; this is a problem with how the economy is structured.
Then you will hear guys complaining about retrofitting their vintage plane not being "able to afford it." Won't someone think of the vintage aircraft owners! The level of entitlement is self parody. Some people have never been told "no" and it shows.
Dad flew Private Pilot from 1960 to 2000 and had multitudes of Cessnas. The last 1/2 of those years, was on 92 octane, right from the gas station, loaded in a 55 gallon drum. He had a buddy rig up a 12 volt pump to fill his wing tanks. The kicker was, it was done out of sight in the hangar. He never had any problems on super unlead from the gas station. He had a timber falling company that recieved a big fuel discount thru Chevron. If we traveled cross country, then things were different. He would always take the 110 leaded, if they had it.
@@daszieher Ethanol is such a menace, it ruins everything. I wish they'd remove it and just embrace e85 for us folks running boost who actually need it, or just anyone who prefers it with flex fuel vehicles.
@@bobbygetsbanned6049 I agree. Better to sell E85 to those, who want it and regular gasoline to the rest. I guess one could adapt taxes to make E85 more attractive, but there is no real need - apart from regulations - to actually mix ethanol into regular gasoline.
Stuff like this is why I am planning on the "experimental" self built category. Technology has advanced so far but aircraft are still relying on ancient tech, like magnetos with points, carburetors with manual mixture control, and of course leaded fuel. For the cost of one O-540 I can put together a pair of detuned Ecoboost 3.5 V6s with gearboxes, and have better high altitude performance, fuel consumption, and just as good if not better reliability. Im all for regulations keeping GA safe, but when the only people who can afford to get into it are retirees, how safe is it really?
There are quite a few small companies doing literally just that, converting car engines to comply with aircraft regulations and reducing weight as much as they can by custom manufacturing parts out of aluminum that would normally be steel. It's quite interesting! VW engines seem quite popular, as do Honda's 1.5L to a lesser extent.
Remember that aviation engines are rated at full power for the entirety of their service life. Auto engines, not so much so. They also have fuel systems that are designed to operate at far broader barometric pressure ranges. Add to that, duel ignition systems, simpler cooling systems and they don't require the complexity of a gearbox. Yes, it can be done, and it has been done. But there's a reason that they fall into experimental rather than GA and there's a reason that the airspace that you are permitted to fly in is restricted.
@@davidbrayshaw3529 Reading your comment, EGRs, variables valve timing, variable geometry turbos, catalytic converters, particulate filters etc came to my mind. I fully agree with you btw. In my car I have a beautiful 3l inline 6 engine with all the bells and whistles to deliver peak performance, fuel efficiency and low emissions. It has similar performance specifications as 13l truck/semi diesel engines but it won’t last a million miles… I remember, back when I was a student in the 80s, that someone explained to me that in GA, ancient engine technology was used. There hasn’t been much progress since then I guess. 🙄 Tx for your comment and happy new year!
@@Conservator. What many people forget with regards to aircraft engines is that they are effectively a stationary engine, not dissimilar to the one on your lawnmower, your generator or in your tractor or yacht. They are designed to run for long periods of time at near full rated power at constant engine speeds. That means that every aspect of the engine can be tuned just for that. The valve timing, stroke, rod length, ignition timing, intake lengths, exhaust, compression ratio etc. are specifically engineered to meet those requirements. And they do it well. So well that for an engine to be certified, it must be capable of producing very close to full rated power for its entire service life (+ - 2,000 hours) This is in stark contrast to a car, which has all kinds of gadgetry built into it so it will run "well enough" at varying loads and speeds. And everything is a compromise. You can't build an engine to be as efficient as a fixed speed engine in that use case. While there are new alternatives to the tried and tested low speed Lycoming's and Continentals, there is also a reason why they have become a mainstay of aviation. They're good. They're reliable and their thermal efficiency is still acceptable, even today.
@@davidbrayshaw3529 Thanks again for emphasising that aspect too. Would you know why relatively simple improvements like electronic ignition hasn’t been implemented?
You mentioned ETBE as an additive. It recalls to mind that MTBE was approved as an addictive, in California if memory serves. Underground gasoline storage tanks are prone to leaking, and MTBE from leaky tanks was contaminating groundwater. It was eventually banned.
yea, instead of making them fix all those leaking tanks, they removed the bad smelling MTBE because no one can sense the VOCs from all that leaked out gasoline :)
And anywhere someone spilled gasoline would contaminate groundwater... So think of all the fuel spills at filling stations, people spilling fuel while refueling lawnmowers and equipment, leaks in fuel tanks, ruptured tanks from collisions... There were many sources where MTBE got into groundwater, not just fuel stations.
@@volvo09 I don't have data but it seems unlikely leaked gasoline could contaminate ground water. It's very light and volatile, so it won't sink into the water table and will quickly evaporate before any reasonable amount could make it into lakes or streams from runoff. Oil on the other hand is a real concern.
@bobbygetsbanned6049 it's not the gasoline, it's the MTBE that was in it, it is one of those chemicals that never goes away, so wherever gas was spilled, the MTBE additive would stay. Granted it's in tiny quantities when a small spill happens, but nonetheless it's still there.
This is a perfect example of how dysfunctional the US aerospace industry is. Brazil has been using ethanol in the very same Lycoming engines for decades, and it only requires a simple modification. Not just that, but multiple companies offer mogas conversions that allow using pump gas, but it slightly reduces power by a nearly imperceptible amount. Some of the mogas kits have larger displacement and actually make MORE power. And both of these solutions have been operating for decades without problems. There have been literally THOUSANDS of these conversions completed without problems, yet they have been excluded from regulatory discussions. With aerospace leadership this agnorant, it’s no surprise that so many airliners are having catastrophic failures that were preventable.
@@daveb4446 Ethanol breaks down most aircraft fuel systems and even if they were compatible, ethanol still wicks up substantial amounts of water into fuel tanks. I've had to replace every single hose on an aircraft because ethanol had turned them into mush. It also has to be consumed within the year it is refined unless you are ok with a btu reduction. Accidents are reported consistently in the US and many of them are related to failed fuel systems and fuel problems related to ethanol. I'm not against other people using it, if they are willing to deal with the risks and higher maintenance. Edit* Also, I would never, ever put ethanol fuels in my lawn mower, dirt bike, or snowblower for good reason. In a car it's fine if it doesn't sit long.
The economics of piston engines and small airports in the US is very different yo Brazil. There is so much more such aviation in the US. Then again, in the US everyone has so much more wealth that this should've been solved 50 years ago.
OP raises an important point about solving problems that a majority of American businesses and politicians don’t care about: the *WILLINGNESS* to find solutions. Business is so focused on extracting the last drop from business that they remain adhered to ancient technology instead of developing newer ones to transition into the future… Cellular technology is a great example: 5G is being sold as the “NEXT BIG THING” when in reality it is just a baby step forward, using the modification of older technology to make it appear that things are happening. When I asked a relative who used to be a very senior executive in the telecoms industry what 5G was about, he said it’s “just smoke and mirrors so that the companies can extract more profit and avoid having to invest capital”…..
Ethanol is terrible idea for cars and for anything else. It attracts water and corrodes fuel lines. I shouldn't be forced to pay taxes to farmers to grow or produce something I don't want AND it's 20% worse than normal gasoline for the environment.
"Wheeler Dealers" would replace the valve seats whenever they converted a leaded-gas engine to unleaded. I thought that would solve the whole problem for aviation engines but Scott's detailed explanation shows that everything is always vastly more complex than at first glance.
UL91 is simply AVGAS (100LL) without the lead. It is available at the pump at a fair number of airfields in Europe but as you say - lots of airfields can only afford to stock one piston fuel.
This by far the best explanation of this that I've heard, even from GAMI. I already bought the STC for my 78 year old Piper, despite the fact that I may never see the stuff, let alone buy any. Because if there's one thing I know about the FAA, they move like racing glaciers.
As someone that is involved with race cars it's wild to me that they continue to use the old engines excuse. We've had race gas for decades that will run fine in old engines that were built for leaded gasoline. The octane is perfectly achievable without the lead, the bigger issue for old engines is that some parts like the valve seats and seals are somewhat reliant on that lead for lubrication. That issue can of course be fixed by changing those out for a design that does not require lead for lubrication. Ethanol is also great for raising the octane, although it does attack some parts as you mentioned, again easy to fix by changing those parts out. E85 has largely supplanted race gas in many circles because of its high octane and latent heat of vaporization. Planes wouldn't want to use that because you burn about 30% more of it, but my point remains... Options are available and have been for ages, the FAA is just dragging their feet (and making things intentionally difficult, as you mentioned with the narrow requirements). Edit: I am not surprised to hear that VP racing is the sole remaining competitor because as I said... Race cars have long since solved this issue. Also, before someone says it, I do understand many of the other complications Scott has gone over, and did prior to watching this video, but I maintain they're making this process unnecessarily difficult regardless. For instance, that STC should frankly not be required. The mechanic is doing no work, the fuel is proven to work, end of story.
Did you watch the video? You are making a poor attempt at repeating all the talking points that Scott made. Race car engines haven't solved anything. They moved from one octane booster (lead) to another. They passed the buck. That's all. For reasons explained in the video, that's cost-prohibitive to do for aircraft engines. Not to mention, race car engines have lifetimes measured in minutes, and reliability is not a primary concern. Power is first. On the other hand, aviation engines make a high percentage of their max rated HP, CONSTANTLY FOR HOURS ON END. Reliability 1st, power 2nd. We're talking thousands and thousands of hours before overhaul. They have to make that power smoothly and consistently. And have a smooth idle, and be smooth at all RPM ranges in between. Billy-bob will have to pull the cams off his rat rod after every run down the track because it's falling apart. It's a hope and a prayer if it can make 90% max power for a few minutes. It could never make 80% power for hours on end like an aviation engine can. It idles like crap. There's no way to make it run smoother, but it doesn't matter if it rattles itself to pieces, as long is it makes it one more run down the track. Take it from someone with decades of experience in aviation. Bubba in the race pits down at the county drag strip doesn't know jack about what it takes to make these changes in aviation. There is more regulation (if you knew anything about how the FAA works, you'd understand why STCs are required), less economy of scale, barriers to entry for competitors, the list goes on. Re-watch the video.
@@Bronco-wr9iiyour mental picture of racing engines is not quite right. For auto racing, you have the right idea, but take a look at offshore racing boats. Those engines live at full throttle for hours at a time, and aircraft only use full power on takeoff, go around, wind shear and terrain escape. Honestly an airplane engine has is easy compared to offshore racing boats.
@Bronco-wr9ii why is it so difficult for an io 360 to run at 2300 rpm for a couple hours without the absolute worst type of fuel known to man, whereas a car engine will happily sit at 3000 rpm on the highway burning UL 87 for hours, no issues? Maybe it's time that we move on from our 1950's engines that make 180 hp out of 5.9 liters of displacement and start using something that can run on not leaded fuel without dying. And don't come at with "uh uh they sit at full power the whole day" continental managed to make engines for diamonds that run just fine at full power, that are literally upgraded mercedes car engines. It can absolutely be done.
@Bronco-wr9ii I did watch the full video, and you're asinine to assume that race car development is behind piston aviation when you're still using tech we abandoned in the eighties. You clearly have no understanding of where modern race car tech is, whereas I do actually have understanding of where modern piston aviation tech is at, but ok. Nobody is running the lumpy mechanical cams that need adjustment anymore, it's all hydraulic lifters, engines last for years, make well over a thousand horsepower, are street driven, and can pass emissions tests. And that's just bubba at the drag strip, which is not even what I was talking about, but you brought him up. You're exactly the person I was addressing at the end of my comment.
I work in Lubricant analysis, and the first time I looked at a small planes ICP results I saw the lead result at 10000 ppm, sent it to get a retest and was confused at the result until my trainer told me that their gas is still leaded
@@jamesphillips2285 I'm sure that they would have performed soil tests. I was referring to larger airports in my post as opposed to smaller municipal airports. The dangers are well known.
This is so excellent, in fact, that I think Scott needs a secondary aviation focused channel. I want absolutely more of this deep dive GA content. (Just fueled up with 100LL the other week for a cylinder break-in despite having an unleaded STC, simply because the greybeards say lead is needed for break-in. Even if a proper high octane fully unleaded avgas were to magically appear tomorrow, it will take decades for 'tribal knowledge' to learn, adapt, and embrace)
Boy, this takes me back to the ChemEng class I took in engineering school in the 70s. The FAA really needs to push for a single standardized lead-free avgas that FBOs can afford to stock (and takes minimal or no STCs).
@samsonsoturian6013 It is about if it costs more to do nothing than to give a tax deduction to companies that produce lead free avgas. That is for people who have more data than you or me to figure out, but it seems reasonable that it may be cheaper in the long run.
The solution is to sue airports, refueling services, and individual pilots, for public nusiance, if they continue to use leaded aviation fuel when unleaded is widely available.
Once again, Scott has taught me something today. I always assumed that the octane rating was correlated with the ratio of octane, heptane, and hexane that constitutes the fuel. I first subscribed to you when you were 'just' a KSP player, and I loved it (and kind of miss it). I stayed subscribed because of my interest in spaceflight - and as an added bonus, I often learn something from the videos. Happy 2025 to you Scott!
Got a friend that worked on spray planes "crop dusters" and it seemed like if a piston aircraft came in, it had a higher probability of being converted to a turboprop engine than it did being serviced and sent back out. But in that line of work, the turboprop is a no brainer.
what i find so ludicrous is i can't buy proper lead solder from mouser anymore, despite lead in solder being utterly benign, but planes can still spray us with TEL.
Ultimately I think valve recession will be the biggest issue here. I do not believe the people that claim valve recession has anything to do with how the engine is operated. I've seen it far too many times in far too many engines. I spent years working in an automotive machine and speed shop building engines of all sort and tuning race engines. Really the only solution is to force the owners of these planes to do the same thing we did with our older automotive engines, install hard valve seats. I find it ridiculous that this hasn't been required. All this is because they refuse to evolve with the rest of us and both install hard seats and adapt modern engine controls. These aren't hard things to do, any engine can be converted. EDIT: BTW it's really only an issue with iron heads, how many plane engines have iron heads, it can't be very many.
You got to remember If someone owns a plane they have money they're not necessarily multi-millionaires but they got money The government doesn't want to f*** with people with money cuz bag realistically they probably know a bunch of people with the government anyway. So why force people with money to do something when you can just make everyone else do s*** You know the peasants. We got all these rules for cars they're basically destroying the diesel engine now The EPA another 50% reduction in soot another 85% reduction in Knox I mean you can almost breathe the exhaust at this point and we're going that much more. But then we'll let these planes crop dust us with lead why It's just where the money is
Fun fact, most of those modern engine controls as you say, are to unreliable to be used in the aviation environment. Safety of flying is the key word here. Just because you think it's OK, doesn't make it ok. If for instance you find yourself flying over the Rocky Mountains in a single engine piston plane and that system starts acting up. You are going to change your mind pretty dang quick! Which is another reason that they use dual magnetos and NOT electronic ignition.
Valve recession has two parts to it. 1. How much "sandpaper" is in your combustion. You don't want any carbon particles from rich fuel, and no salts that might form from aditives like Scot explained. 2. How hot does the inside of the engine get, and how far do the mechanical properties of the materials drop under heat. That's why we have special materials and hardening processes for valves/inlets, pistons, piston rings, and the honing of the cylinder itself. You can adjust both with your timings and injection to an extend. The timing problem with the new fuel: it burns slower. Which is great to extract more power out of every stroke, but it means the components see heat for longer until they get cooled by fresh air again. What you might know from racecars is running super rich mixtures to boost rpm. You just send more fuel, ideally into the compression cycle, to cool stuff down. The cooling is necessary as the mechanical properties of a material go down as you increase temperature. To make the specific case with the airplanes work, you need to reduce the amount of mixture in the cylinder, ignite early and start exhaust early. Which means a view % less max hp, which doesn't really matter, and an even worse idle. Which is a problem as those engines already run quite poorly compared to modern car engines.
Thank you for taking the time to make a video about this! I remember asking you about "dirty" fuel in the USA during your early-morning livestream. Great that you decided to make a video about it!
I am a retired circus performer and have knowledge of side show acts, including fire eating. The volcano, which involves blowing a ball of fire a great distance, uses a special secret flamable mixture with almost as many variations as performers. All I really know about that is that my brother inhaled while holding it in his mouth and instantly got pneumonia, twice. Then he switched to something safer, bear training. The fluid used for the rest of handling, putting out a torch in your mouth, lighting your tongue, and then a torch from your tongue and more can use any flamable liquid. Sometimes kerosene but usually ordinary gasoline. Sometimes siphoned from your own car. Before unleaded gasoline, fire eaters tended to turn blue and die young. Lead is nasty stuff.
That is a use for leaded gas I never thought of - but makes sense. Also how complacent we were with having leaded ga for 75 years in cars does seem foolish on reflection especially as we knew how toxic it is.
@mycosys I did say that it is dangerous. Gasoline works fine for torches, be very careful and safely extinguish them. Firebreathing is a misnomer. Do not breath the fumes of any flamable liquid and absolutely don't swallow any. DO NOT TRY THIS AT HOME. Do not try to learn on your own.
@@mrrolandlawrence That is NOT a use for leaded gasoline. Always use an unleaded flamable liquid. The adverse affects ( insanity, stupidity, death) make the business advantage of turning blue not worth it.
This video really got my attention, as I just came across this topic yesterday after checking out a RUclips channel "Engineering Explained". Two years ago that channel put out a video "America Was Wrong About Leaded Gas - For 100 Years!". It made me think of all the occasions when I was at a local airport with small planes that likely used that fuel with lead in it. Plus, I was born and grew up in part of the decades of peak lead in children's bloodstreams, 1951 to 1980.
Early in my years of flying, I worked for an FBO where we stocked 80 octane leaded (red in color), 100 octane leaded (green in color), 100 octane low lead (blue in color) and 130 octane leaded (Purple in color). Auto and motorcycle racers came from miles around to buy small quantities of our 130 octane "racing fuel". The FBO owner, imposed much higher prices on fuel pumped to containers that were "non airworthy". We made a killing on race weekends! And to answer the underlying question that everyone reading is asking themselves about now, this was in the early and mid 1980's.
As an engineer and private pilot I found this to be a good analysis. 100LL has bugged me for a log time. To your point at the end, I wish there was a simple affordable solution for e.g. a 182 or SR22 with a small JetA turboprop. Other benefits would include better reliability, less complexity, less weight, reduced shock cooling concerns etc.
We're never going to see a turbine with specific fuel consumption close enough to a piston to be affordable for the same crowd. Rotax needs to sell a six cylinder with the footprint and output of an IO-360. Ironically, Rotax has done more than anybody else to get the lead out.
@@mikael1325 the C206 has recently received an STC for the CD300. So I guess, wherever possible, this will slowly make inroads. I remember that the firewall-fwd package costs around 300k. So a cheap, clapped out old Stationair with a cooked engine can be turned into a modern day, jet fuel burning air-SUV for about half a million. That should compete with the market of existing used aircraft.
As the proud owner of a Rotax powered airplane who likes long, cross country trips, this video sums up my frustration with the aviation fuel industry very well.
Fun fact about refinering, now there is SO MUCH demand for the lighter distallates, 'catalytic cracking' is used to break down the heavier long-chain components into shorter chains to convert much of the heavy 'bunker' grade oils to lighter gas/ diesel.
Knock is when the fuel pre-ignites, prior to the spark ignition. The compression stroke ignites the fuel. Higher octane = lower ability to be ignited. Sometimes engines develop knock when there is a build up of carbon, or a metal fragment in the piston. High performance engines have higher compression ratios, so the compression stroke heats the fuel hotter than in a lower compression engine. Hence, they need fuels that are less easily ignited. Hence, higher octane rating. I will also add, higher octane fuels do have a lower flame front speed, so the ignition can be advanced further (igniting the fuel with additional time prior to Top Dead Center). However, engine ECUs can detect knock and un-advance the ignition, if the knock is due to a lower flame-front speed. The same can't be said for pre-detination as described above.
This. Scott messed it up a bit. If the compression is high enough and in right conditions (mix ratio, temperature etc) fuel ignites on its own. That's why diesel engines don't need spark plugs.
Both wrong. Knock or pinging is uncontroled ignition after the spark has ignited the mixture as the flame front first expands it compresses the remaining yet to be burnt mixture further, causing patches to compression ignite before the flame front can spread to all the mixture in a smooth even way. As the multiple flame front convergence as they hit the piston they multiply the force and act like a hammer smashing down on that point of the piston. Causing higher cylinder pressure for a shorter time at the wrong degrees of crank rotation. Pinging can and does Cause Pitting on the crown of the piston Over heat rings and cause butting and pinching Cause premature big end small end and main bearing wear. And if the motor is highly strung ie boosted nitrous ect it can cause the head to lift and blow the head gasket. Pre ignition is then the fuel ignites before the plug does. This is much worse. Normally caused from somthing acting like a glow plug in the cylinder or contamination of the fuel with oil or lean airfuel mixtures. Can do everything knocking does but normally itll melt a big hole in the piston first. Lspi is also a thing thats less damaging but can also damage motors over time even when not running at higher outputs or higher rpm
@@nathanway20690 I was for my whole career explained that knocking is a consequence of pre-ignition. Wikipedia explains knocking in the same way as you do, but they don't state this to happen AFTER spark ignition! I still guess most cases of knocking have to do with pre-ignition???
Yes, octane is the resistance to compression ignition, so this is why diesel fuel is very low octane, about 25 octane. It's usually rated with a cetane rating, which is opposite of octane, the lower the cetane, the higher the octane, and vice versa
It's mostly a legacy issue. Lead also plays a role in lubricating certain components like valves and valve seats. Deciding on a replacement fuel and then committing to a period of retro fit would likely resolve the issue once and for all. It will likely take years to transition over completely as there will be component replacements that are quite involved for a lot of planes. Some work will be easy enough to include as part of an annual. Other work will be quite involved like rebuilding an engine to replace components like valves and valve seats. All that is to say that the good reason to keep it around is because it's been around and part of the engineering of aircraft.
@@saccaed Lead acting as a “lubricant” for valve components is an old wives tale that refuses to die. It’s complete bullshit. It completely ignores the fact that lead is never in its native metallic state when used in fuels but instead combines with the scavenger Ethylene Dibromide to form an abrasive salt (PbBr). When we can finally get rid of the Lead in fuel, we will have fewer deposits and can switch to longer oil change intervals.
Thanks for the deep dive on this. I made a comment on while ago on one of your videos questioning why lead was still used - got quite a lot of negative feedback about that! As I live under a popular flight route for tourists I would really appreciate not being showered with Pb!
Few industries move slower than aviation, a blessing and a curse since it plays a big factor in the amazing safety record of aircraft. You can also buy what is effectively a classic aircraft brand new from the factory, something enthusiasts in other industries/hobbies (mostly cars) can get envious of. I mean, imagine being able to buy a 2024 Chevy Chevelle that was nearly identical to the 1970 Chevelle you wanted as a kid. The shift away from unleaded fuel is only going to really happen if a new unleaded fuel is standardized on as the one fuel, like 100LL is. If there's too many competing standards, nobody will want it and it'll harm GA pretty bad. As good as MoGas is for newer engines, the longevity of GA planes with many pilots owning aircraft older than they are means that the ideal solution is a drop-in 100LL alternative
Eh, don't conflate commercial aviation with general aviation. General aviation is not very safe--a bit worse than motorcycling iirc--and probably can never be much safer than present because the fatal accidents are mainly user error. I wouldn't give the FAA credit or discredit for general aviation safety, and it is a nuisance that things move so slowly there and in everything they touch. Their mandate is broader than the area where they are helpful.
The ideal is a drop-in replacement, but the lack of a drop-in replacement is no excuse for not banning leaded gasoline decades ago. Yeah, plane engines would need some replacement parts for compatibility. Yeah, that would cost money. That's no excuse for why the aviation industry is allowed to get away with giving everyone lead poisoning.
On honoring warranties, there is an option: FAA says: "you *will* warrant that your engine will operate with this fuel after date D, (today + 2 years) and NLT D-365.2422 days, you will determine what, if any, changes need to be made to your engines to accomplish an acceptable level of compatability. Because 100LL will be banned for use in general aviation NLT than date D. Now make it happen."
When I was younger, I used to participate in antique tractor pulls. 1937 John Deere B it was modified by boring out the block for larger pistons. Increasing the stroke of the crank and increasing the compression. It ran like hot garbage on any fuel except 100LL avfuel, but the plugs would foul up something awful after the switch. I never knew why until today. Thank you immensely for answering questions I never thought about but really wanted to know.
Plenty of aircraft engines have reduction gearing to allow the engine to rotate faster than the prop. It's less common on air cooled light aircraft engines but pretty much all large radial piston engines have a reduction gearing. As far as I understand it, the main advantage of running aero engines at lower RPM is primarily maintenance/safety related. Basically run the engine nowhere near it's stress limits.
You see gear reduction on larger prop engines because the tips of the propeller have to remain subsonic. The larger the propeller, the faster the tip speed for any given RPM. They use constant speed propellers and then vary the pitch to control the thrust.
I have to ask if it would be easier for the 40% of engines to be forced to find their own solutions over say 10 years (to allow for big inspection cycles that require substantial disassembly of the aircraft anyway). Surely many could be relatively easily retrofitted with valve seat damage resistant cylinder heads or planes where it's just the fuel system that is unsuitable can have new fuel lines run, new fuel pumps added etc. The last small number of planes where removing lead is simply infeasible, they can go back to mixing in their own lead additive, just as you said they could in the past.
Replacing jugs is a relatively simple process so it shouldn’t really be a problem especially since Continental finally switched over to hardened valve seats in 2019 (only a few decades after Lycoming did)
Compression ratio doesnt directly increase efficiency in a piston engine, rather it is expansion ratio. Power is generated on the expansion/combustion stroke, a higher ratio allows the piston to absorb more energy. A perfectly efficient engine would expand such that the exhaust gas was at ambient temperature. Compression ratio and expansion ratio happen to be the same thing in an otto cycle piston engine, but its the expansion which matters for power.
I used to do tech support for an Oil Company and I used to get calls from the guys that worked with the knock engine for testing. I always enjoyed those calls.
Multiple studies have confirmed that living next to an airport causes health issues. Along with the already known issues with lead the studies found that ultra fine particulates (UFP) are one of the main concerns. They cause respiratory issues and COPD. Vehicles that burn diesel and produce higher levels of UFP are now required to have particulate filters, however aircraft are still not required to use them.
Most airports have been there for 70 years or more. Yet people move next door and complain. You'd think people would research or at least think a small bit before spending money they will have to finance 15+ years.
I wish I’d known that Avgas has lead in it before I used it as a cleaner for two months huffing the fumes daily as an Aircraft mechanic. I’m surprised I survived through that, especially as my boss liked to smoke in the workshop often right after we finished spraying the fuel around cleaning parts. I also recently learned they still use carbon tetrachloride as an engine extinguisher, even though it causes cancer, destroys the ozone layer and is really toxic to the liver.
Everyone ignores the huge role AOPA played in this. For 30+ years AOPA lobbied against any and all unleaded fuel. Only recently did they relent. They claimed to be representing pilots; pilots did not want unleaded fuel.
Thomas Midgley, the creator of tetraethyl lead in petrol, used to demonstrate the ‘safety’ of his invention by pouring the pure liquid over his hands. Coincidentally, Midgley was signed off work on serval occasions to recover from lead poisoning. There were several fatal poisonings of workers at Standard Oil of New Jersey’s manufacturing plant in is first few years of operation. Leaded petrol even became known as ‘looney gas’ - yet somehow Standard Oil of New Jersey (now Exxon) got away with it for decades.
Mr. Midgley led a cursed life. He invented not only TEL for leaded gasoline, but Freon and other CFCs which wrecked the ozone layer. In later life he contracted polio and was left severely disabled. He devised an elaborate system of ropes and pulleys to lift himself out of his home bed, a system in which he became entangled and strangled to death, possibly by intent.
I remember having additives when the leaded gas started disappearing to add to your vehicle to compensate but after a while most people didn't bother as it was believed that there was enough lead residue in the gas tank to make up for the lack of lead in the fuel.
Fun Fact: the guy who put tetra ethyl lead in gasoline went on, after retiring for a bit to cure himself of lead poisoning, went on to work in refrigeration. Guess what amazing innovation he implemented there? That's right, he developed freon, the very gas that almost destroyed Earth's ozone layer, for use in refrigerators. It's frightening to consider what he might have gone on to do to Earth's atmosphere if he hadn't contracted polio. 😳😳😳
Thomas Midgely Junior. He gets all the blame in popular culture, which isn't really fair: He was only one of many engineers on the project. But he can still fairly be given a large share of the game, because he was an utter heartless bastard once he took a management position who knowingly acted to cover up the danger of his invention. Even when the deaths from lead poisoning at production plants started mounting up, Thomas Midgely Junior refused to improve safety measures as this would mean acknowledging the toxicity of the product. No reason to blame him for the ozone issue. Yes, he developed CFC refrigerants - but he had no way of knowing the impact they would have on the upper atmosphere even in small quantities, and the CFCs were introduced as replacements for earlier refrigerants that were either explosive, toxic or both.
If not him, it would have been someone else. Frederic Swarts was the pioneer of CFC's, there is more than just the r133a/freon which Thomas Midgely Jr was attributed to developing. But hate on a dead dude if it helps you sleep better at night... or want nightmares thinking what else he could develop if alive today 😂
(he wasn't a relative) To be fair, food poisoning from warm stored food, and domestic poisoning from Ammonia refrigeration were two significant problems, solved for the time being by Freons. The denialist responses in the oil/fossil industry have grown stronger though, and that's entirely culpable.
100LL (MON) in normal US vehicle(car) fuel standard (AKI = (RON + MON) / 2) is around 107-108 (AKI)octane US pump gas. US, Canada, Mexico and Central America uses it. Rest of the world uses RON octane. 100LL in RON is 115-120 octane.
MON and RON don't translate as directly (factor, linear fashion) as most like to believe. Tests have shown that pre-ignition and detonation occur at slightly different conditions. The variable compression Waukesha engine is also run at different rpm for MON and RON tests and these (600 and 900 respectively, iirc) aren't representative of what actually happens in a real life engine. At least not if I am to believe my colleagues in the national fuel standards committee. 😉
My guess is that because aviation had largely shifted to jet engines by the 60's, and a handful of small airplanes flying here and there by hobbyists weren't realistically going to move the needle much, so it flew under the radar of regulators. That said, it's ultimately good that leaded fuel is being phased out.
100LL has at least twice as much lead as leaded car gas did, and since it is up in the air, is and was distributed far more than the cars, into lots of areas. Anywhere with lots of rich old people who want to fly their small planes around was carpeted in heavy lead for decades after cars stopped doing it. In many places I bet the poison effect from small planes is far worse than the poison effect from the cars from back before the car conversion. Essentially you'd have dozens of planes crossing in a day in some area where there was only a dozen or two cars a day passing by, so the lead from the planes was and is probably twice or more times as bad as the lead from the cars. It is not a small problem by most measures, and definitely not in some areas which have a lot of these small 100LL planes. "Low lead" is compared to another even worse fuel that had even higher lead! It's not really low lead.
There are studies on the effects of the impact of leaded gasoline used in general aviation, and yes it does move the needle. The short version is that the use of leaded gasoline in planes "only" causes measurable impacts within a few miles of airports, dependent on dominant wind directions of course. In terms of demographics, leaded aviation fuel mostly harms poor people, so that might explain why it's taking so long for governments to do something about it.
@@TheBestestKitty No, you are not aware of the scale. There are approximately 14,400 private-use (closed to the public) and 5,000 public-use (open to the public) airports in the US. In the big cities you see lots of jets, but most of the country is not city. These little aircraft are making hundreds of close passes over our farms as they plant organic rice as well as other rice and crops, and of course spray fertilizers and pesticides, herbicides, and fungicides. All the while their tailpipes are pumping out lead which falls out of the air onto the crops. Over 90% of the propeller aircraft are using leaded fuel.
I sold my airplane 10 years ago when I moved out of SQL (and California). Like yourself Scott, I still dream of a small, reliable, and cost effective gas turbine engine for small GA airplanes....
@@keitha.9788 Battery power probably won't ever be practical for large aircraft, but could certainly be practical for someone that just wants to cruise around for a couple of hours in a two seater.
You are a genius to figure all this out. I switched from recips to turbine powered aircraft 33 years ago when I thought the impending 100ll fuel elimination would make my old Baron problematic. Now I fly a homebuilt and use the high octane car fuel made available in Oregon years ago to solve all the small motor problems caused by ethanol in our wet climate environment. Would you know anything about the formulation of the Oregon ethanol free gasoline? Thank you for this great video!
I had the same thought as a kid, that octane rating must be percentage of octane (C8H18) in the fuel. And then I read there was 145 octane fuel and got confused... Good that the lead is on the way to being solved, I thought the ultimate solution would be to switch to diesel in GA (like Diamond) with engines that can use Jet A. Then there would only need to be one fuel at airports. Happy New Year when that time reaches you!
Mr. Manley, I genuinely want to thank you for this topic and it's in-depth coverage. I had completly forgotten that I had worked up a secret fuel additivae blend for motor racing some time ago. I no longer engauge in that sport. However, it seems that the chemistry of it might be of use to the aviation industry. It is lead-free and allowed much lower octane fuels, with their higher energy density, to be used in high-compression racing engines. We were seeing an equivelance to 115 MON/RON from ethanol free pump gas. We were allowd to run it because it was considered a "top end lubricant" ;oD I'll reach out to some of the companies you mentioned and offer the details cheap (not joking.)
one of the major things Scott didn’t mention is that aviation fuel has very tight tolerances for vapour pressure. Aviation engines run hot and the fuel becomes hot enroute to the injection system. A vapour bubble trapped in the fuel system is catastrophic and can result in engine power loss or shutdown. Not funny at takeoff. So many of the lighter aromatics that are used to make race car fuels high octane are far too volatile to use in aircraft fuel systems and start to boil in the fuel lines. This is one of the major stumbling blocks to creating high octane fuel for aircraft that match all the physical properties of 100LL.
Modern car petrol certainly boils at a lower temperature and causes issues with 'classic cars' with water heated manifolds. There's a good video by one guy showing the petrol literally boiling inside the carburettor bowl !
Fundamentally, this was a problem of governance, not tech. It has been more than 40 years since automobile engines have had to adapt to a lead-free world. If the piston GA community had a deadline, they would have figured it out. Hell, there are people making new engines that need 100LL and that's because there is no reason not to. The reality is that engineers are great at solving problems like this when -- but will only do so when their bosses require it.
@@pasad335 I'm a GA pilot myself and there are many ways in which GA is greatly regulated. It is certainly very expensive to learn to fly, to certify an airplane, etc. I don't love regulation. But regulation exists to solve problems that markets won't. In this case, we have a market that solved it's power-to-weight ratio problems by dumping lead into the atmosphere -- a classic "externality". I generally agree that we need regulation to close this loophole. As for people flying newish engines that require 100LL and who might have to prematurely get new engines, I have very little sympathy.
@@policyprogrammerespecially since many lower-power engines, which power the bread-and-butter aircraft of "lower-income" fliers could actually be operated with the unleaded base aviation fuel (basically 100LL without the lead). As was said elsewhere, the main problem is that while the majority of the aircraft don't actually need 100LL, the majority of avgas volume sold is consumed by commercial high-performance aircraft relying on all that the fuel can deliver.
The FAA really doubled down on a losing strategy, continuing their short sited investment into the fuel industry. A far better plan would have been to work with the engine companies to modernize engines and fast tracking their certifications. There is a ton of drama again with GAMI and Swift as both of their UL alternatives have shown signs of increased valve seat erosion. We already have better fuels, what we need are better engines.
Blame lycoming they do everything they can to avoid spending $ to develop newer engines but have no problem charging you 35k+ for an overhaul. These ga engine manufacturers are crooks!
@@skyking6989 The engine situation has really accelerated the death of GA more than anything in the past decade. Take a look at the used aircraft market right now, owners would rather sell their aircraft than deal with trying to get an overhaul.
Add it to the list of embarrassing admissions we'd have to make to an alien race. Unbelievable how little motivation there seems to be to stop making everyone dumber.
My favorite fuel is REC 90 fuel. We use it alot here in Florida. Sold mainly at marinas for marine vessels. My vintage 1960's johnson outboard purrs like a kitten on the stuff.
My Dad's 182M had a waiver to run on 87 octane leaded car gas. When they took the lead out he had to stop. Then he had to put a additive in the 100ll to replace the needed tetraethyllead.
I always wondered about this - I also thought long octane was the standard! It didn't make sense when ethanol was supposed to be useful for preventing knocking. But now that you explained it, isooctane looks like a tertbutyl group which is a preservative!
One difference with an aircraft engine and a car engine is also that an aircraft engine is designed to give the listed power more or less continuously while the car engine is designed for delivering the listed power for a limited time.
Yeah, I'm not about to try running my car at full power for 2,000 hours. I'm reckoning that it would be showing a fall off in power in under 20 hours, doing that.
Scott, dive into autogyros, their design and control differences from both helicopters and planes? Are they the safest heavier-than-air powered flight?
For the opposite example, the US military and most of NATO use JP-8 (or civilian Jet A1, if it's already on hand nearby) for trucks, tanks, jets, helicopters, kerosene heaters/stoves, and everything else that might need liquid fuel, because only having to carry around one type of fuel vastly simplifies logistics. As a random tangent, back in the early days when piston-engined tankers were refueling jets and they had to balance the tanker's need for avgas vs. how much jet fuel to carry as cargo, they must have sometimes run out of one before the other. Now the tankers can sip from their cargo or give some of "their" fuel to somebody else and make more efficient use of their time.
"I wish I had the kind of money that would let me fly a turbine aircraft instead!" Don't we all, Scott. Don't we all... Anyway, this was a very well researched video and a good summary of the story so far. I'd like to point out that the issue with G100UL and nitrile isn't new. GAMI has known about it and been recommending that owners replace nitrile components since they released their fuel. O-rings and seals only need to be replaced the next time maintenance is done. There is no need to replace anything before using G100UL.
It is very complicated, but what you have said is wrong I`m afraid. Knocking is when combustion begins at the wrong LOCATION in the chamber, pre-ignition is when it is initiated at the wrong TIME. The two behaviours although different, frequently are intertwined, and one can start the other off. You can see the error in your statement by looking at an in cylinder pressure curve when detonation is happening, the "sawtooth" pattern generated by the detonation carries on well after the spark has gone off.
I came to make this exact comment. A actually laughed out loud when I heard "mysterious condition called knock" No mystery in it. Can be caused by poor head/block casting leaving hot spots in the combustion chamber, or simply too much compression. Even spark plugs overheating, leaving an extremely hot ground strap glowing in the combustion chamber....I'm done here
Writing this at the start of the video: the aircraft at my flightschool all where converted to diesel/jet-A I really don't get why cirrus and others still sell and develop LL aircraft. Sure the fuel is 10% heavier but I also need less then half. My favorite PA 28 went 110kts IAS at 4.3 galons per hour!! The C172 burned even less. Not setting a time limit for the lead exemption for the US GA sector, and the rest of the world following it, was a huge b Mistake!
Great video! I'm an aircraft mechanic from Canada and had high hopes for G100UL, it's a shame they are having issues with compatibility. Trying to get lead out of General Aviation is such a tough problem, hopefully we get rid of it soon.
Here's the thing: There's no chance whatsoever that leaded gas would be permitted today if it never had been used in the past. There is no excuse for having allowed it for this long.
This is true for cars as a whole, too. The idea of sending 1500 kg of metal and a tank full of highly flammable fuel through cities at high speeds would be totally bonkers by today's standards, let alone letting every half-witted 18 year old and half-blind 80 year old do it. Compare it to the rules we have for flying drones near people (at least here in Europe)...
Our past defines us whether we like it or not. We are nothing without the past. We cannot change what has gone before and we must live in the environment today that was created by yesterday. All we can do is move forward in a positive direction from wherever we find ourselves in the present, to hopefully create a better past for the next generation.
I have been flying for 30 years, and 100LL replacement has been "almost here" the whole time. The only way we can make this work is to implement a full ban on 100LL. Unfortunately, doing so will increase (at least temporarily) the cost of fuel, and I already pay over $6 per gallon on average. But, if the ban is implemented, the switch will happen, and quickly.
The FAA doesn’t want to be responsible for single engine planes going down with engine failures. It’s not the same as banning automotive leaded fuel, cars could pull over of the LRP trashed their valve seats or made them knock, planes don’t have that luxury.
Wait, you’re complaining about 1.54€ per liter?! Try 1.8€ (7.5$ per gallon) for auto gas… avgas 100LL is usually between 2.30-2.60€ per liter here ($9.5 to $10.7 per gallon)
12:50 Cars started switching to unleaded in 1975, when catalytic converters were introduced. Older cars were still able to use leaded fuel until it was phased out in the early 80's.
Is there any comment on this topic from the Warbirds “community” ? How would this fuel perform in a tweaked Merlin or Allison? And then there are the higher power radials. R2800s etc. I don’t own one and have only flown behind IO-540s and smaller. Just asking.
![Seungmin "그렇게, 천천히, 우리(As we are)" | [Stray Kids : SKZ-PLAYER]](http://i.ytimg.com/vi/kAzmhLHePqU/mqdefault.jpg)
Organic chemist here. Hydrocarbon combustion is a free radical chain reaction. Free radicals are molecules that have an unpaired electron. Oxygen is a di-radical that abstracts a hydrogen atom from a hydrocarbon to start the chain reaction producing a hydrocarbon radical. Molecules that have high octane numbers produce more stable, lower energy and less reactive radicals during the combustion process. A carbon atom with other carbon atoms attached to it will produce a more stable radical compared to one with more hydrogens attached. This is why a molecule like isooctane is so good and n-hexane is bad. Benzene rings also help stabilize radicals which is why toluene and xylene are good octane boosters. More stable radicals slow the combustion down without decreasing the energy output.
The chemistry is similar to that of food preservatives like BHT which retard oxidation of food by breaking the free radical chain reaction with a stable radical which cannot continue the radical chain reaction.
@@StevenKeipert Nice.
Organic chemist here. I approve of this explanation.
GTL, Gas-To-Liquid natural gas to gasoline patent by TAMU professor had 100 octane with no impurities, eliminated "flare" of low yield wells impractical NG
Is it the”-OH” group of alcohols that make them octane boosters? Or is it the latent heat of vaporization which cools the air-fuel mixture? I suspect it is both.
@@tonycook1624 why is it that I've never heard of liquid oxygen mixed with kerosene as an explosive? There's panclestite that uses nitrogen tetroxide, I've heard about using charcoal and lox, but never kerosene and lox. Do they not mix?
Situation: There are 14 competing fuel types.
14? Ridiculous! We need to develop one universal fuel that covers everyone's use cases.
Situation: There are 15 competing fuel types.
Exactly, we need one fuel to rule them all.
@@lightningdemolition1964There are now 16 types 👍😄
XKCD eh..
@@lightningdemolition1964 Situation: There are 16 competing fuel types.
Three fuels for the Airlines under the international sky.
Seven for the Airforces in their hangars of stone.
Nine for General Aviators doomed to crash !
One for the Dark Lord on his dark throne.
In the land of Texas where the rockets fly.
One Fuel to rule them all, One Fuel fo drive them,
One Fuel to bring them all to Mars and in the red sand Bind them
In the land of Texas where the rockets fly.
You know there’s a guy with a Piper Cub without an electrical system who flies 10 hours a year and spends the rest of the time petitioning FAA against mandating ADS-B and unleaded fuel.
I will never understand the ADS-B thing. "I don't want the gubment knowing where I go"
Man the government doesn't care what you do with your Cub buddy. Unless you're flying questionable or illegal.
Imagine turning down significantly increased situational awareness cause you have main character syndrome.
Hey I know that guy! No ads B, no radio and always cuts me off while making non-typical pattern entries!
@@jarrettleto every airfield has one 😥
@@jarrettleto I almost met that guy at 700 feet on final approach. me, after doing all the radio calls and patterns for an uncontrolled airport, him in his black-painted Zenith with no radio, calls , or situational awareness.
Talked about him once we got on the ground with the locals - "Oh yeah, that's just Billy-Bob, he does that all the time" Starts his plane at the T hangars, rolls straight to the runway without a runup, blasts off no matter the wind direction.
@@TylerCMilligan american history calls you a liar, your government had many uses in their time for information regardless of you doing something shady
Also something going illegal and making it A-OK in hindsight has been used at times too
Bottom line, dont make up a astrawman if you cant even defeat it cleanly 🤣
TL;DR: Most of the piston engines in small planes are based on 75 year old designs which were engineered based on leaded gasoline.
Yes, but they were even before 100 LL. Probable solution is more like the rotax that run on anything autogas, or the diesels that run on JP-4 STC'd into planes at their next engine rebuild. The STC process would need to be improved. Currently Rotax is a little shy of HP, for mid sized and larger engines, partly offset in some models by turbo normalizing, and has an extra maintenance expense with a need for gearbox inspections/overhaul. Diesels are heavier, usually turbonormalized, with the extra weight partly offset by lower weight of fuel.
@@michaelmcmullen354 The current 100LL contains much less lead than these engines were designed for, and is about the minimum that can be gotten away with.
Yep. Might as well ask why they use magneto ignition and carburetors. A typical 4 cylinder Lycoming is going to give you what, 150-160 HP out of a 320cu engine, costs about $50,000 new and is largely unchanged for the past 70 years. I get it, change is difficult and certifying a new engine is expensive, but cars went to fuel injection and electronic ignition because it is more efficient, more powerful and MORE reliable than carburetors and magnetos. I know a lot of pilots and personally know three that have had catastrophic engine failures (fortunately with safe dead-stick landings). These are not more reliable "tried and true" designs. They are dangerous and obsolete, riding the coat-tails of certification that was done 75 years ago.
@@DragNetJoe You seem to be forgetting that while fuel injection and electronic ignition have been available in cars for a long time, it is only recently where they exceeded the overall reliability of the technologies they replaced. And when those vintage engines fail, it is almost always a maintenance issue and not a design issue.
@@rockets4kids Sure, if you use the worst possible fuel injected engines as an example. Mercedes have used injection since 1970. The whole 'reliability' angle with old airplane engines is a myth. Remember that the maintenance in airplane engines is rigorous for a reason. It's just money sink for plane owners.
Fun fact, 100LL contains more lead than leaded automotive gas ever did.
Aside, there is the “Research” method for measuring octane rating and the “Motor” method. One advances spark timing and the other increases compression. North American gas stations use the average of the two, hence the (R+M)/2 note on the pumps. Other countries may calculate it differently and so have different labels for a similar product.
Another fun fact: when NASCAR switched to unleaded there was an easily detectable increase in school test scores around the tracks.
That's not another fun fact!
When I first learned this in college I always thought of it as 100 Lead-Lead lol! Gotta really emphasize how much lead there is.
@@Broken_robot1986 Seemed to fulfil all "fun" criteria for me in the fact department. Statistically significant rise in test scores with no likely alternative explanation? If one is controlling and calibrating for distance from a NASCAR track, it is an excellent proxy for actual causation. Researchers do this all the time for other environmental contaminant factors.
No wonder I can't concentrate, all this lead in the air.
That is one of those statements which people always repeat which is patently false.
Funny story: one of my chemistry lab mates in grad school ran his $1000 car out of gas. His solution was to swipe a gallon safety can of n-heptane from the lab and fuel up with that. Even when I explained to him that n-heptane was by definition zero octane he still didn't get why his car wouldn't run.
In the 1870's the fraction of crude oil called "gasoline" was a useless byproduct and the standard oil company just dumped it into the river by their refinery. So much gasoline was dumped into the river that sparks from passing steam boats would set the river on fire.
Days like these I’m grateful for the EPA.
@@---capybara--- I don't look forward to the coming days when the EPA may end up on the choping block.
@@WarrenGarabrandt And to think that a Republican - Richard Nixon - created the Environmental Protection Agency
The Cuyahoga in Cleveland caught fire and burned repeatedly throughout the 19th and 20th centuries due to flammable runoff from industry.
*Standard Oil Company (Incorporated)
Glad to see you bringing attention to this issue. I've been as vocal as I can be about tetraethyl lead since I got my A&P license at the age of 19. As pilots and mechanics, we are hurting ourselves the most with 100LL. We need to get the lead out. Mogas STCs have been around for decades. G100UL is proven now. It's time for us to be good stewards to our neighbors and ourselves.
I'm all for getting rid of tetraethyl lead, but G100UL has been shown to be far from the "drop in replacement" that GAMI said it would be. It seems to enhance fuel bladder deterioration causing fuel leaks and causes rubber o-rings to swell and deform. The STC method GAMI chose for certification is far from ideal for an aviation fuel.
How can you talk so much but say so little?
@@Fang70Leaks on 30 year old fuel bladders are common regardless of what fuel you put in them. The main difference is that the leaks stain more with the GAMI fuel. Any GA A&P with more than a few months of experience can tell you, patching and replacing fuel bladders is not a rarity.
@@samsonsoturian6013Because everything that needs to be said technically has been said. This is not a technical problem. It's a problem of political will. I'm pleading with you, as someone who is directly affected by this when I have to go back to work on Thursday, help me find the political will to fix this. Help me give a better world to our neighbors. Help me leave a better world for our children. Help me make a better world for myself. I love aviation, and I love that when I open the door to work, there's an airplane right there. Do I deserve to be poisoned for that?
Modern mogas is perfectly fine for ~70% of aircraft out there, and for the few high performance twins that need 100LL, they can have their timing reduced and suffer a performance hit to run fine on mogas, or they can use G100UL. There are so many viable technical solutions. It's just a problem of political will.
@acefighterpilot liar. If you watched the video you'd know the regs are ahead of what is possible
I talked to an FAA guy who worked on the EAGLE team at OSH a couple years back. He 100% agreed that the real reason why we don't yet have a general 100LL replacement is the goldilocks attitude of the FAA: they can make a fuel that works for 99% of the fleet, or a fuel that can't be mixed with 100LL and/or needs a different mixture, but not one that is 100% compatible. I personally believe that 99% should be just fine.
@@sncy5303 it's not the FAA it's the GAMI/SWIFT groups making alternative fuels and licensing their formulas for unreasonable money. That's why no one can come to an agreement. meanwhile Philips 66 100 LL is cheap and simple to cook.
Maybe they got a bit too inspired by german bureaucracy
@@christiannorf1680 The real "big boy" regulations are EU territory anyway.
German bureaucracy is more like banning "dirty" wood burning stoves, excluding models that got installed pre 1995 and post 2010, also excluded are stoves where the tenants are over 70 or are living there for more than two year.
@@cyan_oxy6734 Heh, yeah. Declaring exceptions from exceptions, which come into play unless the exception from the other exception is met. And don't you even think about making anything in between digital.
Regarding the EU regulations, I don't know. Maybe I just missed it, but they seem pretty straight forward. Like "All mobile entertainment devices shall have a USB-C port for charging, period."
The problem isn’t it just working for 99% of the fleet. It’s also them refusing to let the 1% affected to change their planes to use the new fuel. Because that engine from the 60s is obviously much safer than a new engine design in that plane. However, jump through a few hoops and pay a few fees and you’ll get a waiver somewhere along the way.
Clair Patterson discovered high levels of lead in the environment back in the 40s when they were messing up his geological dating methods. He went on to create one of the first clean rooms and his campaign against lead poisoning lead to a quicker phaseout of leadded fuels for cars. His story is a very interesting read. I remember the tail end of leaded fuel from my childhood when there were still leaded and unleaded gas pumps at gas stations. But I wasn't aware of the effects until a few years ago.
@@buck6365
And you can bet thar alot of their findings were overblown, a classic example of that was the EPA's ridiculous claim of second hand smoke causing cancer, their math was so skewed and their figures so ridiculous that the Supreme Court actually made them withdraw their claims and remove their numbers from their official records and literature (they conveniently moved a decimal point over a few numbers), of course that was AFTER the medical industry and lawyers already got their billions in settlements based on those statistics.
a hero who fought million dollar company
Radiolab has a great episode on this story.
Wow, whatta you know, RUclips has been deleting my comments again, shocking, positively shocking.
Part of the story is the extraordinary lengths the companies went to shut him up. Law suits, burglaries, physical intimidation, blackmail attempts, marketing campaigns to discredit him as a crank - the lot
Phenomenal. Please continue doing deep dives into GA topics, and hope to see you at OSH someday.
the BlueXST's Have it... You RoCk HBX.
Hey Scott, Good video. I'm an engine re-builder. Your later theory about differing octane is what our industry currently accepts as the reason why unleaded fuels cause valve-seat recession. Detonation doesn't always cause engine knock, but can still be putting excessive force on the piston. It also causes a combination of carbon fouling and temperature corrosion on the other components of the chamber. Basically, the temperature climbs high enough to soften the metals, and carbon sediment on the seats is being hammered by the valves, causing pitting and errosion.
Any time our clients inform us that an engine will be switching to unleaded fuel we have a mandatory procedure that includes replacing the valve seats with hardened inserts. We also often recommend stainless-steel valves for similar improvements in longevity. I also believe our engine builder usually recommends adjusting the cooling system at the thermostat to open at a lower temperature to keep up with increased temperature load.
I'm more likely being ridiculous here but I just thought is there any chance that nanodiamonds could be created by the exhaust valves slamming into the carbon sediments on the valve seats combined with high temperatures thus causing accelerated recession of the seats😅?
Thomas Midgley who played a major role in developing leaded gasoline was also involved in developing CFCs. Even though lead was known to be toxic he insisted it wasn't.
He also invented a contraption to turn him in bed, which malfunctioned and killed him.
Fun fact, the chemical used to replace CFCs degrades into a PFAS type compound, and is now the largest source of PFAS pollition in the environment, which is bioaccumulating everywhere.
@@trailingupwards We humans cannot catch a break in this pandora box getting solved by a pandora box chain, can we?
@@youkofoxy Not unless we venture back in the realms of sustainability.
@@Subvertebrate i suppose the bed contraption was the best thing for the environemnt humanity ever invented.
As a new A&P mechanic, Leaded fuels is the primary reason why I chose to stay out of GA and focus on turbine aircraft operating under part 135. Fantastic video, Scott. Thanks for the in-depth chemistry analysis.
As a fellow A&P, good choice. Good luck, cruise far.
are you sure money wasn't the primary reason?
@@aeromatt GA has stepped up their rates recently because they can't find anybody who wants to work on a 50 year old clapped out Cessna with AutoZone parts on it.
Buccys has ethanol free.
That makes no sense. I think you're full of shit.
Lots of farmers in Australia own light planes in order to conveniently and quickly visit large towns and cities. Many of them run their planes on 98 octane retail gasoline meant for cars, as it is available everywhere, and farmers buy it in 80 litre drums for their cars and farm equipment. Toluene is the additive used to obtain 98 octane rating.
It is illegal to use car gasoline in aircraft, but aircraft engines run on it just fine.
In theory, aero engines run on car gasoline could have high valve seat wear, but farmer-owned planes don't clock up anywhere near enough hours for it to matter. Cessna stopped making 152's and 172's in 1985 but considerable numbers are still registered and flying.
The main differences between car gasoline and avgas is the use of tetraethyl lead instead of toluene to achieve the required octane rating, the absence of various proprietary additives to reduce wear that is used in car gasoline, and manufacture of avgas to higher quality standards to ensure purity, absence of ash, etc.
The exhaust valve wear is definitely a thing in cars, especially forced induction, but even then an old Mitsubishi for example will reach 250,000km before valves need a look
Rotax engines run fine on 98 mogas , but you can’t run lycomings or continentals on car gasoline unless they’ve had stc mods
@@spannaspinna I was talking about the Cessna 172 popular with farmers. Most would have the Continental engine. I doubt a typical farmer would bother with supplemental type certificates. They are a pretty go-ahead-and-do-it mob who dislike what they see as government red tape and taxes. Last I heard, using car gasoline was just not permitted - an STC is not applicable.
I've lived on my estate in semi rural North Cheshire UK since 1975 and before lead was banned the roof of every house was clean as a whistle. Since the ban every north facing roof on the estate is caked in moss and its an annual chore to get the scaffolding platform out and scrub it off by hand! Now we know what impact the lead was having in the flora, what was it doing to our lungs as kids?
Clearly keeping the moss out of our lungs.
4:04 Scott, the shock wave breaks through the boundary layer of gas on items like the piston, cylinder bore and head.
This then exposes them to the full temperature of the combustion process.
Aluminium heads and piston crowns would typically melt at normal combustion temperatures, but are protected by those boundary layers of gasses.
Pinging/knocking is the sound of the these violent combustion events and the damage can be very quick if not attended to immediately.
Knocking is the sound of money leaving your wallet.
Never knew about the boundary layer disruption effect. Definitely clears up a lot of my own confusion about the topic.
I somehow thought knocking was a premature ignition that was disrupting the smooth run of the engine, not the combustion turning into a detonation. Now I'm wondering where I got that from, because the explanations of why it's bad and why high octane helps with that pretty much line up 🤔
Is there a specific term for premature ignition?
@@christiannorf1680 Knocking _is_ premature ignition, wherein the fuel detonates during the compression stroke before the piston reaches top dead center and the spark is initiated. Premature ignition by other means is simple called "bad cam timing".
That's right. My professor in mechanical engineering told a story where he destroyed a motorcycle engine within two combustion events where knock occured, when he was tuning the engine that he developed at Rotax. (It's the Rotax engine for the Aprilia RSV Mille, for those that care). So at full tilt, 10.000 rpm, that's four revolutions, so 0.02 seconds. It takes 0.02 seconds to destroy an engine with knock.
I recall hearing that changing a simple hose from rubber that'll last a year or two to silicone that'll last a decade+ resulted in planes being flagged as "experimental" ditto for tires using modern better materials. Aviation seems intent on not advancing.
Yeup. Gotta get an STC or a field Modification 337 form done.
And it’s worse, you’re not experimental, you’re non compliant with the Type Certificate. Meaning not airworthy at all because the part isn’t the specifically called out certified part.
IF you can get your Certificate switched to experimental you could do it. But the FAA is LOATHE to allow planes to go Experimental because it takes the power of their regulation away since they can’t force Type Certificate compliance on Experimental. They think it will become a lawless hellscape.
Unless you build the plane yourself, then it’s fine as an amateur built experimental. I guess because if you can cut drill and rivet you’re somehow magically more competent?
It’s by design. Same reason Nuclear power is so expensive. The government loves to assert power even when it’s nonsense and always gets stricter in regulation.
120 years of tradition, unimpeded by progress!
It's *certified* aviation that refuses advancement! All new good planes are experimental for at least 20 years :D
@ Unless the industry has enough money to buy deregulation, then it goes in a completely other bad direction.
Thanks for a great video on this subject! I have the G100UL STC for my plane, and I was at Reid-Hillview on the day that sales began to buy a tank of the fuel. It works great. There are a lot of vested interests doing their level best to sabotage and undermine G100UL, and to spread disinformation about it. The paint thing is just one example: George has shown pictures of painted aircraft parts literally soaking in buckets of G100UL. It doesn't hurt the paint, assuming that the paint is not already about to fall off in the first place. The FAA should have found a way to do a blanket approval of this fuel and be done with it.
Yep, every pic of paint damage "from G100UL" I have seen obviously wasn't primed properly. Areas beyond the affected section flaking off and bubbling.
"I'm going to poison your kids so the paint on my plane doesn't peel" does not seem so good a reason when you say it like that
I think the FAA is going to wait and see how things go with voluntary use.
@@jimhayes2786That’s a whole other issue in GA of absolute shit repaint jobs that cost a fortune, usually done by the barely qualified in shops without proper or any disposal permits.
When the only people left in General Aviation are the sociopathically selfish rich, it’s enshitification at every turn.
Wow. Who'd have thought a 30 min video on petrol would be interesting enough to keep my attention the entire time. Well done, Scott!
Happy New Year to everyone!
I never set out for this to be so long, but I kept finding cool things to talk aboit
@@scottmanleyHighly recommend the avweb series from Paul Bertorelli about how we found ourselves in this predicament.
By thought exactly!
@@scottmanley
it worked,
commentary is 🚀 the 🌙
Very interesting, Scott, walking in the path of legendary Paul Bertorelli! Over here in Germany we have MoGas quite readily available; at least at those airfields I am allowed to use in my flight school. Further, all of our C172s have that MoGas STC done. Please keep the aviation content coming and Happy New Year to you!
Paul Bertorelli has retired from AvWeb, but one of the big pushes he did in the last part of his journalistic career was covering unleaded GA fuel and why it wasn't happening. Might want to watch some of his videos on that.
Aw man he retired?
@@jaypaint4855I love his content ❤
@@jaypaint4855 And AvWeb is going down hill fast. It used to be pretty entertaining to read their articles, especially Paul's..
I saw his videos and interviews when the fuel had been approved. Always enjoyed Paul's dry humor and he was the reason I watched AvWeb.
Paul’s video are simply must watch for anyone interrupting in aviation.
His engineering and economics explanation of what is viable in GA are awesome.
One thing you didn't mention about regular car gas is ethanol likes to bond and adsorb water. This leads to long term storage issues and operational issues with aircraft engines. One of the best things about 100LL is it is super stable. You can have it sit in a carburetor for well over a year with zero issues. Try doing that with anything that has ethanol in it.
The Australian government ran a scare campaign on ethanol being used in fuel… then made it legal when they could tax it
It sure does. There is fuel stabilizer though for it.
Modern gas wrecks havoc with the carbs in automobiles, too.
A little water is no problem as long as you don't have a catalytic converter.
@@rockets4kids How many carbs are there these days? Any vehicle with one would be considered a vintage car now.
OMG, this is an insanely complicated chemistry problem, of which, I had not an inkling of an idea, even existed. Thanks, Scott for this explanation.
Here in Minnesota it’s pretty easy to get 91 Octane non-ethanol gas. This is actually the best fuel for many small engines such as chainsaws, lawn mowers, marine outboards, etc. I do feel like it was less common in California, but it’s great if you can find a convenient located source of non-ethanol gasoline.
It’s less common in CA because the Ethanol also acts as an oxidizing detergent and reduces some emission byproducts.
Not a big deal in Minnesota, but bigger deal with 5x the population per square mile.
I know your guyses octane numbers are lower but here in Germany you can aswell get 102 octane lead free, ethanol free gas. I like to use it when I have to store my vehicle for a few months.
@ yes you're buying what in the US would be 93-95 octane. We have it here for boats and race cars. Most Regular gas stations don't sell it because without the ethanol subsidy it's like $2 a Liter more.
Yeah it’s common in many northern climates. I think under some federal regulation it’s actually a carve-out for snowmobiles! But I agree, very useful for small engines like lawnmowers and such.
As I understand it, Ethanol-free gas would actually be cheaper than modern 10-15% E-gas if government subsidies for Corn Ethanol (the predominant source of fuel Ethanols, afaik) were to vanish. Corn Ethanol, considering only commercial factors and absent subsidy, runs about 9 dollars a gallon last I checked. Adding in Ethanol to gasoline, therefore, feels like a well-meaning government program based on some misunderstandings and false premises.
If we really wanted a renewable combustion fuel, Ethanol is one of the worst candidates.
Ethanol is an excellent additive to raise AKI. Except Brazil and some countries in Europe, Ethanol will remain an additive or base for racing fuels. HVO is better candidate and retro compatible with every diesel engine and zero sulfur and phosphate component promoting a cleaner burn
Corn ethanol, because Iowa...
there could be fuels hypothetically produced in ways that relate to the current biological production of ethanol, but there's no indication that the current production of ethanol is getting us any closer to that. Currently, the production of ethanol does nothing to advance technology in a meaningful way and only serves to hinder progress and create incentive to lobby against the funding of potentially disruptive research on sustainable combustion fuel.
I've heard it described that the US is the Saudi Arabia of corn.
Did you accounted for the Petrol industry subsidies?
31:31 So, aviators who don’t want to poison the environment are a “niche market”? This is bigger than aviation fuel; this is a problem with how the economy is structured.
Then you will hear guys complaining about retrofitting their vintage plane not being "able to afford it." Won't someone think of the vintage aircraft owners! The level of entitlement is self parody. Some people have never been told "no" and it shows.
Dad flew Private Pilot from 1960 to 2000 and had multitudes of Cessnas. The last 1/2 of those years, was on 92 octane, right from the gas station, loaded in a 55 gallon drum. He had a buddy rig up a 12 volt pump to fill his wing tanks. The kicker was, it was done out of sight in the hangar. He never had any problems on super unlead from the gas station. He had a timber falling company that recieved a big fuel discount thru Chevron.
If we traveled cross country, then things were different. He would always take the 110 leaded, if they had it.
Back in the day there was no ethanol in the fuel to spoil that plan.
@@daszieher Ethanol free gas is still widely available. It's all I put in my cars unless I'm road tripping.
Key word ,car! Ethanol is not good for anything except the companies producing it.
@@daszieher Ethanol is such a menace, it ruins everything. I wish they'd remove it and just embrace e85 for us folks running boost who actually need it, or just anyone who prefers it with flex fuel vehicles.
@@bobbygetsbanned6049 I agree. Better to sell E85 to those, who want it and regular gasoline to the rest. I guess one could adapt taxes to make E85 more attractive, but there is no real need - apart from regulations - to actually mix ethanol into regular gasoline.
Stuff like this is why I am planning on the "experimental" self built category. Technology has advanced so far but aircraft are still relying on ancient tech, like magnetos with points, carburetors with manual mixture control, and of course leaded fuel. For the cost of one O-540 I can put together a pair of detuned Ecoboost 3.5 V6s with gearboxes, and have better high altitude performance, fuel consumption, and just as good if not better reliability.
Im all for regulations keeping GA safe, but when the only people who can afford to get into it are retirees, how safe is it really?
There are quite a few small companies doing literally just that, converting car engines to comply with aircraft regulations and reducing weight as much as they can by custom manufacturing parts out of aluminum that would normally be steel. It's quite interesting! VW engines seem quite popular, as do Honda's 1.5L to a lesser extent.
Remember that aviation engines are rated at full power for the entirety of their service life. Auto engines, not so much so. They also have fuel systems that are designed to operate at far broader barometric pressure ranges. Add to that, duel ignition systems, simpler cooling systems and they don't require the complexity of a gearbox.
Yes, it can be done, and it has been done. But there's a reason that they fall into experimental rather than GA and there's a reason that the airspace that you are permitted to fly in is restricted.
@@davidbrayshaw3529
Reading your comment, EGRs, variables valve timing, variable geometry turbos, catalytic converters, particulate filters etc came to my mind.
I fully agree with you btw.
In my car I have a beautiful 3l inline 6 engine with all the bells and whistles to deliver peak performance, fuel efficiency and low emissions. It has similar performance specifications as 13l truck/semi diesel engines but it won’t last a million miles…
I remember, back when I was a student in the 80s, that someone explained to me that in GA, ancient engine technology was used. There hasn’t been much progress since then I guess. 🙄
Tx for your comment and happy new year!
@@Conservator. What many people forget with regards to aircraft engines is that they are effectively a stationary engine, not dissimilar to the one on your lawnmower,
your generator or in your tractor or yacht. They are designed to run for long periods of time at near full rated power at constant engine speeds. That means that every aspect of the engine can be tuned just for that. The valve timing, stroke, rod length, ignition timing, intake lengths, exhaust, compression ratio etc. are specifically engineered to meet those requirements. And they do it well. So well that for an engine to be certified, it must be capable of producing very close to full rated power for its entire service life (+ - 2,000 hours)
This is in stark contrast to a car, which has all kinds of gadgetry built into it so it will run "well enough" at varying loads and speeds. And everything is a compromise. You can't build an engine to be as efficient as a fixed speed engine in that use case.
While there are new alternatives to the tried and tested low speed Lycoming's and Continentals, there is also a reason why they have become a mainstay of aviation. They're good. They're reliable and their thermal efficiency is still acceptable, even today.
@@davidbrayshaw3529
Thanks again for emphasising that aspect too.
Would you know why relatively simple improvements like electronic ignition hasn’t been implemented?
As someone who works in the experimental side of the general aviation industry, I can tell you the answer in three words. Inertia and lawyers.
You mentioned ETBE as an additive. It recalls to mind that MTBE was approved as an addictive, in California if memory serves. Underground gasoline storage tanks are prone to leaking, and MTBE from leaky tanks was contaminating groundwater. It was eventually banned.
This happened in Maine too.
yea, instead of making them fix all those leaking tanks, they removed the bad smelling MTBE because no one can sense the VOCs from all that leaked out gasoline :)
And anywhere someone spilled gasoline would contaminate groundwater... So think of all the fuel spills at filling stations, people spilling fuel while refueling lawnmowers and equipment, leaks in fuel tanks, ruptured tanks from collisions... There were many sources where MTBE got into groundwater, not just fuel stations.
@@volvo09 I don't have data but it seems unlikely leaked gasoline could contaminate ground water. It's very light and volatile, so it won't sink into the water table and will quickly evaporate before any reasonable amount could make it into lakes or streams from runoff. Oil on the other hand is a real concern.
@bobbygetsbanned6049 it's not the gasoline, it's the MTBE that was in it, it is one of those chemicals that never goes away, so wherever gas was spilled, the MTBE additive would stay.
Granted it's in tiny quantities when a small spill happens, but nonetheless it's still there.
This is a perfect example of how dysfunctional the US aerospace industry is. Brazil has been using ethanol in the very same Lycoming engines for decades, and it only requires a simple modification. Not just that, but multiple companies offer mogas conversions that allow using pump gas, but it slightly reduces power by a nearly imperceptible amount. Some of the mogas kits have larger displacement and actually make MORE power. And both of these solutions have been operating for decades without problems. There have been literally THOUSANDS of these conversions completed without problems, yet they have been excluded from regulatory discussions. With aerospace leadership this agnorant, it’s no surprise that so many airliners are having catastrophic failures that were preventable.
Exactly!
@@daveb4446 Ethanol breaks down most aircraft fuel systems and even if they were compatible, ethanol still wicks up substantial amounts of water into fuel tanks. I've had to replace every single hose on an aircraft because ethanol had turned them into mush. It also has to be consumed within the year it is refined unless you are ok with a btu reduction. Accidents are reported consistently in the US and many of them are related to failed fuel systems and fuel problems related to ethanol. I'm not against other people using it, if they are willing to deal with the risks and higher maintenance. Edit* Also, I would never, ever put ethanol fuels in my lawn mower, dirt bike, or snowblower for good reason. In a car it's fine if it doesn't sit long.
The economics of piston engines and small airports in the US is very different yo Brazil. There is so much more such aviation in the US. Then again, in the US everyone has so much more wealth that this should've been solved 50 years ago.
OP raises an important point about solving problems that a majority of American businesses and politicians don’t care about: the *WILLINGNESS* to find solutions. Business is so focused on extracting the last drop from business that they remain adhered to ancient technology instead of developing newer ones to transition into the future…
Cellular technology is a great example: 5G is being sold as the “NEXT BIG THING” when in reality it is just a baby step forward, using the modification of older technology to make it appear that things are happening. When I asked a relative who used to be a very senior executive in the telecoms industry what 5G was about, he said it’s “just smoke and mirrors so that the companies can extract more profit and avoid having to invest capital”…..
Ethanol is terrible idea for cars and for anything else. It attracts water and corrodes fuel lines. I shouldn't be forced to pay taxes to farmers to grow or produce something I don't want AND it's 20% worse than normal gasoline for the environment.
Mother Jones had a great article about the sharp decline in violent crimes in the US occurring after the ban on leaded gas. Great read.
Leaded avgas is basically the Internet Explorer of fuels ... At some point, we, collectively, have to drop support for obsolete tech.
Grandpa's going to be confused.
Teach grandpa to use chrome or firefox
@@Menaceblue3 It's difficult to teach new tricks to old dogs!
Except IE doesn't drop toxic dust everywhere.
My guess is that none of these comments come from people who own aircraft. It’s so super easy to spend other people’s money.
"Wheeler Dealers" would replace the valve seats whenever they converted a leaded-gas engine to unleaded. I thought that would solve the whole problem for aviation engines but Scott's detailed explanation shows that everything is always vastly more complex than at first glance.
UL91 is simply AVGAS (100LL) without the lead.
It is available at the pump at a fair number of airfields in Europe but as you say - lots of airfields can only afford to stock one piston fuel.
This by far the best explanation of this that I've heard, even from GAMI. I already bought the STC for my 78 year old Piper, despite the fact that I may never see the stuff, let alone buy any. Because if there's one thing I know about the FAA, they move like racing glaciers.
As someone that is involved with race cars it's wild to me that they continue to use the old engines excuse. We've had race gas for decades that will run fine in old engines that were built for leaded gasoline.
The octane is perfectly achievable without the lead, the bigger issue for old engines is that some parts like the valve seats and seals are somewhat reliant on that lead for lubrication. That issue can of course be fixed by changing those out for a design that does not require lead for lubrication.
Ethanol is also great for raising the octane, although it does attack some parts as you mentioned, again easy to fix by changing those parts out. E85 has largely supplanted race gas in many circles because of its high octane and latent heat of vaporization. Planes wouldn't want to use that because you burn about 30% more of it, but my point remains... Options are available and have been for ages, the FAA is just dragging their feet (and making things intentionally difficult, as you mentioned with the narrow requirements).
Edit: I am not surprised to hear that VP racing is the sole remaining competitor because as I said... Race cars have long since solved this issue.
Also, before someone says it, I do understand many of the other complications Scott has gone over, and did prior to watching this video, but I maintain they're making this process unnecessarily difficult regardless. For instance, that STC should frankly not be required. The mechanic is doing no work, the fuel is proven to work, end of story.
Did you watch the video? You are making a poor attempt at repeating all the talking points that Scott made. Race car engines haven't solved anything. They moved from one octane booster (lead) to another. They passed the buck. That's all.
For reasons explained in the video, that's cost-prohibitive to do for aircraft engines. Not to mention, race car engines have lifetimes measured in minutes, and reliability is not a primary concern. Power is first.
On the other hand, aviation engines make a high percentage of their max rated HP, CONSTANTLY FOR HOURS ON END. Reliability 1st, power 2nd. We're talking thousands and thousands of hours before overhaul. They have to make that power smoothly and consistently. And have a smooth idle, and be smooth at all RPM ranges in between.
Billy-bob will have to pull the cams off his rat rod after every run down the track because it's falling apart. It's a hope and a prayer if it can make 90% max power for a few minutes. It could never make 80% power for hours on end like an aviation engine can.
It idles like crap. There's no way to make it run smoother, but it doesn't matter if it rattles itself to pieces, as long is it makes it one more run down the track.
Take it from someone with decades of experience in aviation. Bubba in the race pits down at the county drag strip doesn't know jack about what it takes to make these changes in aviation. There is more regulation (if you knew anything about how the FAA works, you'd understand why STCs are required), less economy of scale, barriers to entry for competitors, the list goes on. Re-watch the video.
@@Bronco-wr9iiyour mental picture of racing engines is not quite right. For auto racing, you have the right idea, but take a look at offshore racing boats. Those engines live at full throttle for hours at a time, and aircraft only use full power on takeoff, go around, wind shear and terrain escape. Honestly an airplane engine has is easy compared to offshore racing boats.
@@jdrisselare offshore power boat engines expected to make the 1,000 or 2,000-hour mark?
How tolerant is a power boat racer to engine failure?
@Bronco-wr9ii why is it so difficult for an io 360 to run at 2300 rpm for a couple hours without the absolute worst type of fuel known to man, whereas a car engine will happily sit at 3000 rpm on the highway burning UL 87 for hours, no issues?
Maybe it's time that we move on from our 1950's engines that make 180 hp out of 5.9 liters of displacement and start using something that can run on not leaded fuel without dying.
And don't come at with "uh uh they sit at full power the whole day" continental managed to make engines for diamonds that run just fine at full power, that are literally upgraded mercedes car engines. It can absolutely be done.
@Bronco-wr9ii I did watch the full video, and you're asinine to assume that race car development is behind piston aviation when you're still using tech we abandoned in the eighties. You clearly have no understanding of where modern race car tech is, whereas I do actually have understanding of where modern piston aviation tech is at, but ok. Nobody is running the lumpy mechanical cams that need adjustment anymore, it's all hydraulic lifters, engines last for years, make well over a thousand horsepower, are street driven, and can pass emissions tests. And that's just bubba at the drag strip, which is not even what I was talking about, but you brought him up. You're exactly the person I was addressing at the end of my comment.
Finally, someone explains lead in fuel and octane ratings as it makes sense concisely and comprehensibly. Thank you for the wealth of knowledge!
I work in Lubricant analysis, and the first time I looked at a small planes ICP results I saw the lead result at 10000 ppm, sent it to get a retest and was confused at the result until my trainer told me that their gas is still leaded
And they used to pour the oil onto unsealed runways back in the day. Top Tip: Don't build a house on an old airport.
Did you also find hydrochloric and hydrobromic acids in the sump oil?
@@davidbrayshaw3529 Hmm: they are turning the old municipal airport where I live into a housing development.
@@jamesphillips2285 I'm sure that they would have performed soil tests.
I was referring to larger airports in my post
as opposed to smaller municipal airports.
The dangers are well known.
Scott, this is probably the best treatise on this issue I've read/seen, EVER. Well done!
This is so excellent, in fact, that I think Scott needs a secondary aviation focused channel. I want absolutely more of this deep dive GA content. (Just fueled up with 100LL the other week for a cylinder break-in despite having an unleaded STC, simply because the greybeards say lead is needed for break-in. Even if a proper high octane fully unleaded avgas were to magically appear tomorrow, it will take decades for 'tribal knowledge' to learn, adapt, and embrace)
Well done communication on the issue. One of the best yet. Thank you Scott Manley. Always welcome at 0Q9, hangar g2.
Boy, this takes me back to the ChemEng class I took in engineering school in the 70s. The FAA really needs to push for a single standardized lead-free avgas that FBOs can afford to stock (and takes minimal or no STCs).
U old
For sure. Even if it takes a subsidy, it's got to be worth it.
@krissp8712 no one is giving you free stuff
@samsonsoturian6013 It is about if it costs more to do nothing than to give a tax deduction to companies that produce lead free avgas. That is for people who have more data than you or me to figure out, but it seems reasonable that it may be cheaper in the long run.
The solution is to sue airports, refueling services, and individual pilots, for public nusiance, if they continue to use leaded aviation fuel when unleaded is widely available.
Once again, Scott has taught me something today. I always assumed that the octane rating was correlated with the ratio of octane, heptane, and hexane that constitutes the fuel.
I first subscribed to you when you were 'just' a KSP player, and I loved it (and kind of miss it). I stayed subscribed because of my interest in spaceflight - and as an added bonus, I often learn something from the videos.
Happy 2025 to you Scott!
Got a friend that worked on spray planes "crop dusters" and it seemed like if a piston aircraft came in, it had a higher probability of being converted to a turboprop engine than it did being serviced and sent back out. But in that line of work, the turboprop is a no brainer.
what i find so ludicrous is i can't buy proper lead solder from mouser anymore, despite lead in solder being utterly benign, but planes can still spray us with TEL.
CPC still sells the purple 60/40 stuff, I use it myself.
Ultimately I think valve recession will be the biggest issue here. I do not believe the people that claim valve recession has anything to do with how the engine is operated. I've seen it far too many times in far too many engines. I spent years working in an automotive machine and speed shop building engines of all sort and tuning race engines.
Really the only solution is to force the owners of these planes to do the same thing we did with our older automotive engines, install hard valve seats. I find it ridiculous that this hasn't been required. All this is because they refuse to evolve with the rest of us and both install hard seats and adapt modern engine controls. These aren't hard things to do, any engine can be converted.
EDIT: BTW it's really only an issue with iron heads, how many plane engines have iron heads, it can't be very many.
Same thing with VW engine in my day........
You got to remember If someone owns a plane they have money they're not necessarily multi-millionaires but they got money The government doesn't want to f*** with people with money cuz bag realistically they probably know a bunch of people with the government anyway.
So why force people with money to do something when you can just make everyone else do s*** You know the peasants.
We got all these rules for cars they're basically destroying the diesel engine now The EPA another 50% reduction in soot another 85% reduction in Knox I mean you can almost breathe the exhaust at this point and we're going that much more.
But then we'll let these planes crop dust us with lead why It's just where the money is
Fun fact, most of those modern engine controls as you say, are to unreliable to be used in the aviation environment. Safety of flying is the key word here. Just because you think it's OK, doesn't make it ok.
If for instance you find yourself flying over the Rocky Mountains in a single engine piston plane and that system starts acting up. You are going to change your mind pretty dang quick!
Which is another reason that they use dual magnetos and NOT electronic ignition.
Valve recession has two parts to it.
1. How much "sandpaper" is in your combustion.
You don't want any carbon particles from rich fuel, and no salts that might form from aditives like Scot explained.
2. How hot does the inside of the engine get, and how far do the mechanical properties of the materials drop under heat.
That's why we have special materials and hardening processes for valves/inlets, pistons, piston rings, and the honing of the cylinder itself.
You can adjust both with your timings and injection to an extend. The timing problem with the new fuel: it burns slower. Which is great to extract more power out of every stroke, but it means the components see heat for longer until they get cooled by fresh air again. What you might know from racecars is running super rich mixtures to boost rpm. You just send more fuel, ideally into the compression cycle, to cool stuff down. The cooling is necessary as the mechanical properties of a material go down as you increase temperature.
To make the specific case with the airplanes work, you need to reduce the amount of mixture in the cylinder, ignite early and start exhaust early. Which means a view % less max hp, which doesn't really matter, and an even worse idle. Which is a problem as those engines already run quite poorly compared to modern car engines.
Yes this is the only correct answer to leaded fuels. Hardened seats and e85 would be my choice if it wasn’t for the needed 30% more fuel
Thank you for taking the time to make a video about this!
I remember asking you about "dirty" fuel in the USA during your early-morning livestream.
Great that you decided to make a video about it!
I am a retired circus performer and have knowledge of side show acts, including fire eating. The volcano, which involves blowing a ball of fire a great distance, uses a special secret flamable mixture with almost as many variations as performers. All I really know about that is that my brother inhaled while holding it in his mouth and instantly got pneumonia, twice. Then he switched to something safer, bear training.
The fluid used for the rest of handling, putting out a torch in your mouth, lighting your tongue, and then a torch from your tongue and more can use any flamable liquid. Sometimes kerosene but usually ordinary gasoline. Sometimes siphoned from your own car. Before unleaded gasoline, fire eaters tended to turn blue and die young. Lead is nasty stuff.
Please dont breathe/dance fire with gasoline - i have known a lot of dancers/breathers (inc myself) but never one stupid enough to breath gasoline.
That is a use for leaded gas I never thought of - but makes sense. Also how complacent we were with having leaded ga for 75 years in cars does seem foolish on reflection especially as we knew how toxic it is.
@mycosys I did say that it is dangerous. Gasoline works fine for torches, be very careful and safely extinguish them. Firebreathing is a misnomer. Do not breath the fumes of any flamable liquid and absolutely don't swallow any.
DO NOT TRY THIS AT HOME.
Do not try to learn on your own.
@@MarkHorton-n3t just no. Firewater and kerosene are readily available. have a brain
@@mrrolandlawrence That is NOT a use for leaded gasoline. Always use an unleaded flamable liquid. The adverse affects ( insanity, stupidity, death) make the business advantage of turning blue not worth it.
This video really got my attention, as I just came across this topic yesterday after checking out a RUclips channel "Engineering Explained". Two years ago that channel put out a video "America Was Wrong About Leaded Gas - For 100 Years!". It made me think of all the occasions when I was at a local airport with small planes that likely used that fuel with lead in it. Plus, I was born and grew up in part of the decades of peak lead in children's bloodstreams, 1951 to 1980.
Early in my years of flying, I worked for an FBO where we stocked 80 octane leaded (red in color), 100 octane leaded (green in color), 100 octane low lead (blue in color) and 130 octane leaded (Purple in color). Auto and motorcycle racers came from miles around to buy small quantities of our 130 octane "racing fuel". The FBO owner, imposed much higher prices on fuel pumped to containers that were "non airworthy". We made a killing on race weekends! And to answer the underlying question that everyone reading is asking themselves about now, this was in the early and mid 1980's.
As an engineer and private pilot I found this to be a good analysis. 100LL has bugged me for a log time. To your point at the end, I wish there was a simple affordable solution for e.g. a 182 or SR22 with a small JetA turboprop. Other benefits would include better reliability, less complexity, less weight, reduced shock cooling concerns etc.
We're never going to see a turbine with specific fuel consumption close enough to a piston to be affordable for the same crowd.
Rotax needs to sell a six cylinder with the footprint and output of an IO-360. Ironically, Rotax has done more than anybody else to get the lead out.
You are talking about Continental's CD-300. That is a suitable JetA replacement for many high performance six cylinder aero engines.
Dude, AV 100UL is widely available.
@@daszieheryeah, on a diamond aircraft DA50~ but there isn’t STC for bonanza~
I do know New archer do have CD170 option.
@@mikael1325 the C206 has recently received an STC for the CD300. So I guess, wherever possible, this will slowly make inroads.
I remember that the firewall-fwd package costs around 300k. So a cheap, clapped out old Stationair with a cooked engine can be turned into a modern day, jet fuel burning air-SUV for about half a million.
That should compete with the market of existing used aircraft.
As the proud owner of a Rotax powered airplane who likes long, cross country trips, this video sums up my frustration with the aviation fuel industry very well.
Same here, my 912ULS only burns 100LL on cross country’s.
@@richardfranklin2252 Using 100LL decreases the time for the gearbox inspection because of the build up between gears.
Exactly. Lockwood Aero inspected my gearbox @ 1200 hrs. Running 100LL very few times meant the reduction gears were in excellent condition.
Fun fact about refinering, now there is SO MUCH demand for the lighter distallates, 'catalytic cracking' is used to break down the heavier long-chain components into shorter chains to convert much of the heavy 'bunker' grade oils to lighter gas/ diesel.
Knock is when the fuel pre-ignites, prior to the spark ignition. The compression stroke ignites the fuel. Higher octane = lower ability to be ignited. Sometimes engines develop knock when there is a build up of carbon, or a metal fragment in the piston.
High performance engines have higher compression ratios, so the compression stroke heats the fuel hotter than in a lower compression engine. Hence, they need fuels that are less easily ignited. Hence, higher octane rating.
I will also add, higher octane fuels do have a lower flame front speed, so the ignition can be advanced further (igniting the fuel with additional time prior to Top Dead Center). However, engine ECUs can detect knock and un-advance the ignition, if the knock is due to a lower flame-front speed. The same can't be said for pre-detination as described above.
Is this the same as "dieseling"? Is this Scott not knowing what he was talking about again?
This. Scott messed it up a bit. If the compression is high enough and in right conditions (mix ratio, temperature etc) fuel ignites on its own. That's why diesel engines don't need spark plugs.
Both wrong.
Knock or pinging is uncontroled ignition after the spark has ignited the mixture as the flame front first expands it compresses the remaining yet to be burnt mixture further, causing patches to compression ignite before the flame front can spread to all the mixture in a smooth even way.
As the multiple flame front convergence as they hit the piston they multiply the force and act like a hammer smashing down on that point of the piston. Causing higher cylinder pressure for a shorter time at the wrong degrees of crank rotation.
Pinging can and does
Cause
Pitting on the crown of the piston
Over heat rings and cause butting and pinching
Cause premature big end small end and main bearing wear. And if the motor is highly strung ie boosted nitrous ect it can cause the head to lift and blow the head gasket.
Pre ignition is then the fuel ignites before the plug does.
This is much worse.
Normally caused from somthing acting like a glow plug in the cylinder or contamination of the fuel with oil or lean airfuel mixtures.
Can do everything knocking does but normally itll melt a big hole in the piston first.
Lspi is also a thing thats less damaging but can also damage motors over time even when not running at higher outputs or higher rpm
@@nathanway20690 I was for my whole career explained that knocking is a consequence of pre-ignition. Wikipedia explains knocking in the same way as you do, but they don't state this to happen AFTER spark ignition! I still guess most cases of knocking have to do with pre-ignition???
Yes, octane is the resistance to compression ignition, so this is why diesel fuel is very low octane, about 25 octane. It's usually rated with a cetane rating, which is opposite of octane, the lower the cetane, the higher the octane, and vice versa
I never realized the additional problems that lead causes mechanically in airplane engines, there's not even a good reason to keep it around anymore!
It's mostly a legacy issue. Lead also plays a role in lubricating certain components like valves and valve seats. Deciding on a replacement fuel and then committing to a period of retro fit would likely resolve the issue once and for all. It will likely take years to transition over completely as there will be component replacements that are quite involved for a lot of planes. Some work will be easy enough to include as part of an annual. Other work will be quite involved like rebuilding an engine to replace components like valves and valve seats. All that is to say that the good reason to keep it around is because it's been around and part of the engineering of aircraft.
@@saccaed
Lead acting as a “lubricant” for valve components is an old wives tale that refuses to die. It’s complete bullshit.
It completely ignores the fact that lead is never in its native metallic state when used in fuels but instead combines with the scavenger Ethylene Dibromide to form an abrasive salt (PbBr).
When we can finally get rid of the Lead in fuel, we will have fewer deposits and can switch to longer oil change intervals.
Thanks for the deep dive on this. I made a comment on while ago on one of your videos questioning why lead was still used - got quite a lot of negative feedback about that! As I live under a popular flight route for tourists I would really appreciate not being showered with Pb!
Few industries move slower than aviation, a blessing and a curse since it plays a big factor in the amazing safety record of aircraft. You can also buy what is effectively a classic aircraft brand new from the factory, something enthusiasts in other industries/hobbies (mostly cars) can get envious of. I mean, imagine being able to buy a 2024 Chevy Chevelle that was nearly identical to the 1970 Chevelle you wanted as a kid.
The shift away from unleaded fuel is only going to really happen if a new unleaded fuel is standardized on as the one fuel, like 100LL is. If there's too many competing standards, nobody will want it and it'll harm GA pretty bad. As good as MoGas is for newer engines, the longevity of GA planes with many pilots owning aircraft older than they are means that the ideal solution is a drop-in 100LL alternative
Sounds utopian. Otherwise it would have already happened, even with all the corruption.
Eh, don't conflate commercial aviation with general aviation. General aviation is not very safe--a bit worse than motorcycling iirc--and probably can never be much safer than present because the fatal accidents are mainly user error. I wouldn't give the FAA credit or discredit for general aviation safety, and it is a nuisance that things move so slowly there and in everything they touch. Their mandate is broader than the area where they are helpful.
The ideal is a drop-in replacement, but the lack of a drop-in replacement is no excuse for not banning leaded gasoline decades ago. Yeah, plane engines would need some replacement parts for compatibility. Yeah, that would cost money. That's no excuse for why the aviation industry is allowed to get away with giving everyone lead poisoning.
On honoring warranties, there is an option: FAA says: "you *will* warrant that your engine will operate with this fuel after date D, (today + 2 years) and NLT D-365.2422 days, you will determine what, if any, changes need to be made to your engines to accomplish an acceptable level of compatability. Because 100LL will be banned for use in general aviation NLT than date D. Now make it happen."
When I was younger, I used to participate in antique tractor pulls. 1937 John Deere B it was modified by boring out the block for larger pistons. Increasing the stroke of the crank and increasing the compression. It ran like hot garbage on any fuel except 100LL avfuel, but the plugs would foul up something awful after the switch. I never knew why until today. Thank you immensely for answering questions I never thought about but really wanted to know.
Plenty of aircraft engines have reduction gearing to allow the engine to rotate faster than the prop. It's less common on air cooled light aircraft engines but pretty much all large radial piston engines have a reduction gearing. As far as I understand it, the main advantage of running aero engines at lower RPM is primarily maintenance/safety related. Basically run the engine nowhere near it's stress limits.
You see gear reduction on larger prop engines because the tips of the propeller have to remain subsonic. The larger the propeller, the faster the tip speed for any given RPM. They use constant speed propellers and then vary the pitch to control the thrust.
@@wally7856 Add to that that you see gear reduction on high speed engines such as modern Rotax's. The sound when they stop is brutal to my ears.
Happy new year to. Any fellow Europeans those who watch Scott Manley videos when they release at 02:39
European here, watching at 04:21
Good morning from a low lead pilot Germany. At 04:53 :- )
I have to ask if it would be easier for the 40% of engines to be forced to find their own solutions over say 10 years (to allow for big inspection cycles that require substantial disassembly of the aircraft anyway).
Surely many could be relatively easily retrofitted with valve seat damage resistant cylinder heads or planes where it's just the fuel system that is unsuitable can have new fuel lines run, new fuel pumps added etc.
The last small number of planes where removing lead is simply infeasible, they can go back to mixing in their own lead additive, just as you said they could in the past.
Replacing jugs is a relatively simple process so it shouldn’t really be a problem especially since Continental finally switched over to hardened valve seats in 2019 (only a few decades after Lycoming did)
Compression ratio doesnt directly increase efficiency in a piston engine, rather it is expansion ratio. Power is generated on the expansion/combustion stroke, a higher ratio allows the piston to absorb more energy. A perfectly efficient engine would expand such that the exhaust gas was at ambient temperature.
Compression ratio and expansion ratio happen to be the same thing in an otto cycle piston engine, but its the expansion which matters for power.
I used to do tech support for an Oil Company and I used to get calls from the guys that worked with the knock engine for testing. I always enjoyed those calls.
Multiple studies have confirmed that living next to an airport causes health issues. Along with the already known issues with lead the studies found that ultra fine particulates (UFP) are one of the main concerns. They cause respiratory issues and COPD. Vehicles that burn diesel and produce higher levels of UFP are now required to have particulate filters, however aircraft are still not required to use them.
Most airports have been there for 70 years or more. Yet people move next door and complain. You'd think people would research or at least think a small bit before spending money they will have to finance 15+ years.
You couldn't use a particulate filter on jet aircraft.
I wish I’d known that Avgas has lead in it before I used it as a cleaner for two months huffing the fumes daily as an Aircraft mechanic. I’m surprised I survived through that, especially as my boss liked to smoke in the workshop often right after we finished spraying the fuel around cleaning parts. I also recently learned they still use carbon tetrachloride as an engine extinguisher, even though it causes cancer, destroys the ozone layer and is really toxic to the liver.
That's because the amount of lead you need to eat is alot
Well you survived it because lead isn't necessarily immediately dangerous but rather it's not good for your brain, especially brain development.
Your brain was already developed into mush. No worries about lead for you.
Just don't dip your balls in it, and you're probably fine with 110LL...
@@NoPegs dam it guess im in trouble
Most complete explanation of the history & the engineering/chemistry challenges involved. Thanks, Scott. Fly lead-free (and safe)!
I knew that Avgas still contained lead but I had no idea the situation was so complicated.
Happy New Year
Everyone ignores the huge role AOPA played in this. For 30+ years AOPA lobbied against any and all unleaded fuel. Only recently did they relent. They claimed to be representing pilots; pilots did not want unleaded fuel.
Thomas Midgley, the creator of tetraethyl lead in petrol, used to demonstrate the ‘safety’ of his invention by pouring the pure liquid over his hands. Coincidentally, Midgley was signed off work on serval occasions to recover from lead poisoning.
There were several fatal poisonings of workers at Standard Oil of New Jersey’s manufacturing plant in is first few years of operation. Leaded petrol even became known as ‘looney gas’ - yet somehow Standard Oil of New Jersey (now Exxon) got away with it for decades.
Exxon mentioned? "The CSB wants to know your location"
Mr. Midgley led a cursed life. He invented not only TEL for leaded gasoline, but Freon and other CFCs which wrecked the ozone layer. In later life he contracted polio and was left severely disabled. He devised an elaborate system of ropes and pulleys to lift himself out of his home bed, a system in which he became entangled and strangled to death, possibly by intent.
I remember having additives when the leaded gas started disappearing to add to your vehicle to compensate but after a while most people didn't bother as it was believed that there was enough lead residue in the gas tank to make up for the lack of lead in the fuel.
Fun Fact: the guy who put tetra ethyl lead in gasoline went on, after retiring for a bit to cure himself of lead poisoning, went on to work in refrigeration. Guess what amazing innovation he implemented there? That's right, he developed freon, the very gas that almost destroyed Earth's ozone layer, for use in refrigerators.
It's frightening to consider what he might have gone on to do to Earth's atmosphere if he hadn't contracted polio. 😳😳😳
Thomas Midgely Junior. He gets all the blame in popular culture, which isn't really fair: He was only one of many engineers on the project. But he can still fairly be given a large share of the game, because he was an utter heartless bastard once he took a management position who knowingly acted to cover up the danger of his invention. Even when the deaths from lead poisoning at production plants started mounting up, Thomas Midgely Junior refused to improve safety measures as this would mean acknowledging the toxicity of the product.
No reason to blame him for the ozone issue. Yes, he developed CFC refrigerants - but he had no way of knowing the impact they would have on the upper atmosphere even in small quantities, and the CFCs were introduced as replacements for earlier refrigerants that were either explosive, toxic or both.
If not him, it would have been someone else.
Frederic Swarts was the pioneer of CFC's, there is more than just the r133a/freon which Thomas Midgely Jr was attributed to developing.
But hate on a dead dude if it helps you sleep better at night... or want nightmares thinking what else he could develop if alive today 😂
(he wasn't a relative) To be fair, food poisoning from warm stored food, and domestic poisoning from Ammonia refrigeration were two significant problems, solved for the time being by Freons.
The denialist responses in the oil/fossil industry have grown stronger though, and that's entirely culpable.
100LL (MON) in normal US vehicle(car) fuel standard (AKI = (RON + MON) / 2) is around 107-108 (AKI)octane US pump gas. US, Canada, Mexico and Central America uses it. Rest of the world uses RON octane. 100LL in RON is 115-120 octane.
MON and RON don't translate as directly (factor, linear fashion) as most like to believe. Tests have shown that pre-ignition and detonation occur at slightly different conditions.
The variable compression Waukesha engine is also run at different rpm for MON and RON tests and these (600 and 900 respectively, iirc) aren't representative of what actually happens in a real life engine.
At least not if I am to believe my colleagues in the national fuel standards committee. 😉
Thanks for an awesome lecture on Aviation fuel , basically better than what I got during my aeronautical engineering degree :D
My guess is that because aviation had largely shifted to jet engines by the 60's, and a handful of small airplanes flying here and there by hobbyists weren't realistically going to move the needle much, so it flew under the radar of regulators.
That said, it's ultimately good that leaded fuel is being phased out.
100LL has at least twice as much lead as leaded car gas did, and since it is up in the air, is and was distributed far more than the cars, into lots of areas. Anywhere with lots of rich old people who want to fly their small planes around was carpeted in heavy lead for decades after cars stopped doing it. In many places I bet the poison effect from small planes is far worse than the poison effect from the cars from back before the car conversion. Essentially you'd have dozens of planes crossing in a day in some area where there was only a dozen or two cars a day passing by, so the lead from the planes was and is probably twice or more times as bad as the lead from the cars. It is not a small problem by most measures, and definitely not in some areas which have a lot of these small 100LL planes. "Low lead" is compared to another even worse fuel that had even higher lead! It's not really low lead.
We have a lot of small prop planes in the US. And a lt of little airports that support them. Much more than Europe, or anywhere.
There are studies on the effects of the impact of leaded gasoline used in general aviation, and yes it does move the needle. The short version is that the use of leaded gasoline in planes "only" causes measurable impacts within a few miles of airports, dependent on dominant wind directions of course. In terms of demographics, leaded aviation fuel mostly harms poor people, so that might explain why it's taking so long for governments to do something about it.
I’m seeing that reading comprehension is lacking here.
@@TheBestestKitty No, you are not aware of the scale. There are approximately 14,400 private-use (closed to the public) and 5,000 public-use (open to the public) airports in the US. In the big cities you see lots of jets, but most of the country is not city. These little aircraft are making hundreds of close passes over our farms as they plant organic rice as well as other rice and crops, and of course spray fertilizers and pesticides, herbicides, and fungicides. All the while their tailpipes are pumping out lead which falls out of the air onto the crops. Over 90% of the propeller aircraft are using leaded fuel.
I sold my airplane 10 years ago when I moved out of SQL (and California). Like yourself Scott, I still dream of a small, reliable, and cost effective gas turbine engine for small GA airplanes....
We will probably have affordable electric planes before we have affordable turbine engines.
@@rocketman221projects I doubt it. Have to solve the battery energy storage problem.
@@keitha.9788 Battery power probably won't ever be practical for large aircraft, but could certainly be practical for someone that just wants to cruise around for a couple of hours in a two seater.
You are a genius to figure all this out. I switched from recips to turbine powered aircraft 33 years ago when I thought the impending 100ll fuel elimination would make my old Baron problematic. Now I fly a homebuilt and use the high octane car fuel made available in Oregon years ago to solve all the small motor problems caused by ethanol in our wet climate environment. Would you know anything about the formulation of the Oregon ethanol free gasoline? Thank you for this great video!
I had the same thought as a kid, that octane rating must be percentage of octane (C8H18) in the fuel. And then I read there was 145 octane fuel and got confused...
Good that the lead is on the way to being solved, I thought the ultimate solution would be to switch to diesel in GA (like Diamond) with engines that can use Jet A. Then there would only need to be one fuel at airports.
Happy New Year when that time reaches you!
Mr. Manley, I genuinely want to thank you for this topic and it's in-depth coverage. I had completly forgotten that I had worked up a secret fuel additivae blend for motor racing some time ago. I no longer engauge in that sport. However, it seems that the chemistry of it might be of use to the aviation industry. It is lead-free and allowed much lower octane fuels, with their higher energy density, to be used in high-compression racing engines. We were seeing an equivelance to 115 MON/RON from ethanol free pump gas. We were allowd to run it because it was considered a "top end lubricant" ;oD I'll reach out to some of the companies you mentioned and offer the details cheap (not joking.)
Super cool
one of the major things Scott didn’t mention is that aviation fuel has very tight tolerances for vapour pressure. Aviation engines run hot and the fuel becomes hot enroute to the injection system. A vapour bubble trapped in the fuel system is catastrophic and can result in engine power loss or shutdown. Not funny at takeoff. So many of the lighter aromatics that are used to make race car fuels high octane are far too volatile to use in aircraft fuel systems and start to boil in the fuel lines. This is one of the major stumbling blocks to creating high octane fuel for aircraft that match all the physical properties of 100LL.
Modern car petrol certainly boils at a lower temperature and causes issues with 'classic cars' with water heated manifolds. There's a good video by one guy showing the petrol literally boiling inside the carburettor bowl !
Fundamentally, this was a problem of governance, not tech. It has been more than 40 years since automobile engines have had to adapt to a lead-free world. If the piston GA community had a deadline, they would have figured it out. Hell, there are people making new engines that need 100LL and that's because there is no reason not to. The reality is that engineers are great at solving problems like this when -- but will only do so when their bosses require it.
For sure, GA needs to be significantly more regulated, for both emissions and NOISE.
@@pasad335 I'm a GA pilot myself and there are many ways in which GA is greatly regulated. It is certainly very expensive to learn to fly, to certify an airplane, etc. I don't love regulation. But regulation exists to solve problems that markets won't. In this case, we have a market that solved it's power-to-weight ratio problems by dumping lead into the atmosphere -- a classic "externality". I generally agree that we need regulation to close this loophole.
As for people flying newish engines that require 100LL and who might have to prematurely get new engines, I have very little sympathy.
@@policyprogrammerespecially since many lower-power engines, which power the bread-and-butter aircraft of "lower-income" fliers could actually be operated with the unleaded base aviation fuel (basically 100LL without the lead).
As was said elsewhere, the main problem is that while the majority of the aircraft don't actually need 100LL, the majority of avgas volume sold is consumed by commercial high-performance aircraft relying on all that the fuel can deliver.
The FAA really doubled down on a losing strategy, continuing their short sited investment into the fuel industry. A far better plan would have been to work with the engine companies to modernize engines and fast tracking their certifications. There is a ton of drama again with GAMI and Swift as both of their UL alternatives have shown signs of increased valve seat erosion. We already have better fuels, what we need are better engines.
UND's valve seat drama was totally unfounded. Nobody else has reproduced this. Savvy Aviation has a great video on UND's flawed methodology.
Blame lycoming they do everything they can to avoid spending $ to develop newer engines but have no problem charging you 35k+ for an overhaul. These ga engine manufacturers are crooks!
@@jvtaylor3 how can you talk so much but say so little?
@@skyking6989 The engine situation has really accelerated the death of GA more than anything in the past decade. Take a look at the used aircraft market right now, owners would rather sell their aircraft than deal with trying to get an overhaul.
@@jvtaylor3 lycoming are crooks!
Add it to the list of embarrassing admissions we'd have to make to an alien race. Unbelievable how little motivation there seems to be to stop making everyone dumber.
Have you heard about a fool and their funds?
My favorite fuel is REC 90 fuel. We use it alot here in Florida. Sold mainly at marinas for marine vessels. My vintage 1960's johnson outboard purrs like a kitten on the stuff.
It seems REC-90 would be the perfect solution for most recreational flying with low-compression engines requiring only 80/87 avgas
My Dad's 182M had a waiver to run on 87 octane leaded car gas. When they took the lead out he had to stop. Then he had to put a additive in the 100ll to replace the needed tetraethyllead.
Thanks, Scott, for pulling back the curtain on the effort to remove lead from AVGAS!
I always wondered about this - I also thought long octane was the standard! It didn't make sense when ethanol was supposed to be useful for preventing knocking. But now that you explained it, isooctane looks like a tertbutyl group which is a preservative!
One difference with an aircraft engine and a car engine is also that an aircraft engine is designed to give the listed power more or less continuously while the car engine is designed for delivering the listed power for a limited time.
hence the problems emerging with hybrids...
Yeah, I'm not about to try running my car at full power for 2,000 hours. I'm reckoning that it would be showing a fall off in power in under 20 hours, doing that.
I thought Aircraft mechanics got some years. You are the first person I’ve come across that really explains this subject correctly. Thank you.
Scott, dive into autogyros, their design and control differences from both helicopters and planes? Are they the safest heavier-than-air powered flight?
You can run turbines on Diesel too. Generally only if it’s set up for it though, common on turboprop bush planes and turbine helicopters
For the opposite example, the US military and most of NATO use JP-8 (or civilian Jet A1, if it's already on hand nearby) for trucks, tanks, jets, helicopters, kerosene heaters/stoves, and everything else that might need liquid fuel, because only having to carry around one type of fuel vastly simplifies logistics.
As a random tangent, back in the early days when piston-engined tankers were refueling jets and they had to balance the tanker's need for avgas vs. how much jet fuel to carry as cargo, they must have sometimes run out of one before the other. Now the tankers can sip from their cargo or give some of "their" fuel to somebody else and make more efficient use of their time.
@@DeliveryMcGee who’d have thought running everything on the same fuel would simplify logistics!
jets can also run on avgas. that is how the jets on the Convair B36 bomber ran
@@davidgenie-ci5zl yeah I remember my dad saying that jets can run on basically anything that burns
"I wish I had the kind of money that would let me fly a turbine aircraft instead!"
Don't we all, Scott. Don't we all...
Anyway, this was a very well researched video and a good summary of the story so far. I'd like to point out that the issue with G100UL and nitrile isn't new. GAMI has known about it and been recommending that owners replace nitrile components since they released their fuel. O-rings and seals only need to be replaced the next time maintenance is done. There is no need to replace anything before using G100UL.
3:53 This is incorrect. Knocking is caused by the air fuel mixture detonating BEFORE the spark is initiated, not after.
I got quite confused, because I was also sure that that's what knocking was. But then again, I'm not that much into engines and stuff.
It is very complicated, but what you have said is wrong I`m afraid. Knocking is when combustion begins at the wrong LOCATION in the chamber, pre-ignition is when it is initiated at the wrong TIME. The two behaviours although different, frequently are intertwined, and one can start the other off.
You can see the error in your statement by looking at an in cylinder pressure curve when detonation is happening, the "sawtooth" pattern generated by the detonation carries on well after the spark has gone off.
I came to make this exact comment. A actually laughed out loud when I heard "mysterious condition called knock"
No mystery in it.
Can be caused by poor head/block casting leaving hot spots in the combustion chamber, or simply too much compression. Even spark plugs overheating, leaving an extremely hot ground strap glowing in the combustion chamber....I'm done here
Writing this at the start of the video: the aircraft at my flightschool all where converted to diesel/jet-A I really don't get why cirrus and others still sell and develop LL aircraft. Sure the fuel is 10% heavier but I also need less then half. My favorite PA 28 went 110kts IAS at 4.3 galons per hour!! The C172 burned even less. Not setting a time limit for the lead exemption for the US GA sector, and the rest of the world following it, was a huge b
Mistake!
Most of the world did not follow. 100LL has long been banned in many countries, including all the EU.
Great video! I'm an aircraft mechanic from Canada and had high hopes for G100UL, it's a shame they are having issues with compatibility. Trying to get lead out of General Aviation is such a tough problem, hopefully we get rid of it soon.
Here's the thing: There's no chance whatsoever that leaded gas would be permitted today if it never had been used in the past. There is no excuse for having allowed it for this long.
This is true for cars as a whole, too. The idea of sending 1500 kg of metal and a tank full of highly flammable fuel through cities at high speeds would be totally bonkers by today's standards, let alone letting every half-witted 18 year old and half-blind 80 year old do it.
Compare it to the rules we have for flying drones near people (at least here in Europe)...
@@TobiKellnerIt was bonkers 120 years ago too.
Our past defines us whether we like it or not. We are nothing without the past. We cannot change what has gone before and we must live in the environment today that was created by yesterday. All we can do is move forward in a positive direction from wherever we find ourselves in the present, to hopefully create a better past for the next generation.
I have been flying for 30 years, and 100LL replacement has been "almost here" the whole time. The only way we can make this work is to implement a full ban on 100LL. Unfortunately, doing so will increase (at least temporarily) the cost of fuel, and I already pay over $6 per gallon on average. But, if the ban is implemented, the switch will happen, and quickly.
Californian detected, opinion rejected.
It'd be close to 600 per gallon if all damage done by you and your leaded fuel calculated into the price.
@@wreckage-vs5jv where did you get that number?
The FAA doesn’t want to be responsible for single engine planes going down with engine failures. It’s not the same as banning automotive leaded fuel, cars could pull over of the LRP trashed their valve seats or made them knock, planes don’t have that luxury.
Wait, you’re complaining about 1.54€ per liter?! Try 1.8€ (7.5$ per gallon) for auto gas… avgas 100LL is usually between 2.30-2.60€ per liter here ($9.5 to $10.7 per gallon)
12:50 Cars started switching to unleaded in 1975, when catalytic converters were introduced. Older cars were still able to use leaded fuel until it was phased out in the early 80's.
Is there any comment on this topic from the Warbirds “community” ? How would this fuel perform in a tweaked Merlin or Allison? And then there are the higher power radials. R2800s etc. I don’t own one and have only flown behind IO-540s and smaller. Just asking.
I know the warbird engines are allowed under the STC for G100UL but don’t know anyone flying with it.