FAA approves unleaded fuel for piston fleet | Hacker News Reader

FAA approves unleaded fuel for piston fleet

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Congratulations to GAMI. They are a really interesting and innovative small company. Their calibrated fuel injectors are a great upgrade for many planes letting you save 5-15% of fuel. They make an innovative turbo system for the Cessna Cardinal that is quite a challenge. But taking on the task of creating an unleaded avgas and shepherding it through an arduous approval process for literally decades.. Good for them.

(GAMI is still independently owned, right? Sometimes it feels like the last American GA company that wasn't bought by a Chinese aviation company.)

Impressive work by GAMI who are working on it since decades. AVWeb made 2 videos on the subject of leaded avgas and on how hard it is to get it approved. In addition, the FAA launched several failed attempts with the industry at large.

  * https://www.youtube.com/watch?v=9F-WngVMJBQ The Long, Twisted And Slightly Ridiculous Story of Avgas Part 1
  * https://www.youtube.com/watch?v=Mvse4Xhzwuk The Long, Twisted And Slightly Ridiculous Story of Avgas Part 2

When reading the announcement, it looks like some municipalities in California started banning the sale of leaded avgas and I suspect that helped to push the FAA to finally move in approving G1000UL. Not surprisingly, they will start providing it to the California market before the other states. In the announcement on avweb.com (https://www.avweb.com/ownership/fuel-news/gami-unleaded-avga...), they also credit Mark Baker from the AOAP to encourage the FAA to complete the project.

I recall watching a YouTube video a little while back that went into the modern history of light aircraft engines, and how there have been several failed attempts at redesigning existing technology over the past 20 (40?) years.

Is it genuinely workable? Or is there some weird edge case that makes it completely impractical from a maintenance or reliability perspective?

There were several failures from converted ex-automotive engines. Some of those were related to vibration; others to the much higher percentage of power that an airplane engine runs for hours on end.

My engine might last for only 2000 flight hours between overhauls. In those 2000 flight hours, it's likely to burn ~30K gallons of fuel. Taking that as a proxy for the total energy generated, 30K gallons of fuel will take a typical car almost a million miles. How many cars reach 1 million miles without major engine work?

There were also a bunch of (IMO misguided) attempts to fit liquid cooled engines into aircraft. What do you have absolutely no shortage of in flight? Fast moving, cool air. What do you have no tolerance for in flight? Loss of coolant.

It's not impossible to improve upon them, but aircraft engines have gotten to a local maximum of sorts where they're pretty darn good at what they do and the maintenance needs and failure modes are pretty well understood.

Ooooohhh, the air-cooled vs. water-cooled argument is a great one. The mechanical simplicity of air-cooled engines is a very strong point in their favor, but it's arguably the only one. Water-cooled engines can be run leaner (i.e. more efficiently) because they don't need to run rich to keep cool, don't have uneven cooling issues, aren't susceptible to thermal shock when going to idle during a cruise descent, have better power-to-weight ratios, and don't have as big of a problem dealing with the dilemma of having the slowest/warmest airflow when the most engine power is needed (during takeoff and go-around conditions)--all for the relatively modest risk of a pump, radiator, or hose failure. In an alternate reality where we had seen the same amount of R&D go into general aviation piston engines as automotive ones, I wouldn't be surprised if nearly all light aircraft used hybrid-electric liquid-cooled engines with reduction gearboxes.

Unless you build a rocket or submarine, all engines are air cooled. Using an intermediate transfer medium with high heat capacity seems like a design tradeoff, it helps you achieve higher power density in the combustion chamber at the expense of total mass of the propulsion system and some extra complexity.

Given the specifics of aircraft operation, large amounts of available coolant air, extra mass of cooling gear with available materials etc., I wouldn't be surprised if the result of that optimization problem is always against liquid cooling; at least for ICE engines where you can only achieve limited efficiency gains with higher temperatures and power densities.

> [...] at least for ICE engines where you can only achieve limited efficiency gains with higher temperatures and power densities.

More generally: all heat engines need high temperatures for efficiency. By Carnot's Theorem the best energy conversion efficiency you can hope for is (T_hot - T_cold) / T_hot

Where T_hot is the temperature of your combustion, and T_cold is the lowest temperature you can cool it too, ie ambient temperature at best.

Sure, in principle, but in practice you are limited by the actual fuel you need to burn, and it seems the existing designs get close enough to those limits and do not stand to gain significantly from higher energy densities. Fuel efficiency and range is a primary target for optimization for decades, I doubt there are vast reserves of untapped efficiency just waiting for a hotter engine.

Engine temperature effect on efficiency is about heat loss, which isn't accounted for in the Carnot cycle (it assumes perfectly reversible cycle, and heat conduction across a temperature difference is not reversible: it's heat bleeding from one point to another and averaging out, kind of like mixing two substances).

If the metal walls of your combustion chamber are cold, there will be more heat transferred and more entropy generated. Looking more physically, heat lost after combustion reduces the temperature and therefore pressure of the gas on the power stroke, reducing power output for a given heat input (i.e. less efficient).

Yes. Carnot's Theorem gives merely an upper bound on the efficiency you can achieve.

In practice, you can easily do much worse. Eg via heatloss as you say.

However, you can never do better.

Most (perhaps all) marine engines are water cooled, not just submarines.

I don't know. If you look at the swan song of big aviation piston engines just before turbines took over (immediate post-WWII era), it was all air-cooled radials. If the WWII experience would have proved liquid cooled engines to be superior, I guess all those Convairs, Constellations, DC-6's etc. would be using Griffons, Sabres or such.

That's survivor bias and sheer production numbers of us bombers, only the us models mainly used air cooled radial engines (bombers and carrier fighters), neither the german nor the UK ones did (mostly, exceptions always exist).

> That's survivor bias and sheer production numbers of us bombers

To an extent yes, but the US certainly produced liquid cooled aircraft engines as well, like the Allison's and Packard Merlins powering many famous WWII aircraft. If they would have considered liquid cooled engines obviously superior, I'm sure they would have preferred those in post-WWII piston aircraft.

> neither the german nor the UK ones did (mostly, exceptions always exist).

The UK produced nearly 60000 Bristol Hercules radials, practically all used in multi engined aircraft (Beaufighter, Wellington, Stirling, Halifax being the major ones AFAIK). Sure, a much lower production numbers than the famous Merlin at 150000 engines, but far from insignificant.

Similarly, Germany produced over 60000 BMW 801 radials, mostly used in the FW190A fighters but some were also used in some Ju88 variants. In comparison the DB 600 engines powering mostly Bf 109 was about 60000 as well, and about 70000 Jumo 21X series used mostly in bombers.

So very broadly speaking, of total aircraft engine production, both UK and Germany produced about 1/3 radials and 2/3 liquid cooled.

Indeed the liquid cooled Rolls Royce Griffon engined Avro Shackleton was in service until 1991 with the Royal Air Force

https://en.m.wikipedia.org/wiki/Avro_Shackleton

I worry about people who use a word like 'superior' without any dimensions.

I can think of plenty of reasons the simpler design with one less failure mode might dominate production during the war, without being the obviously better choice given peacetime applications and seventy years of technical advances.

I worry when there is a hidden assumption that people were dummies for the choices they made. That tends to be more true for policy than engineering.

Distilled impression.

Water cooled inline engines. Small frontal area means lower drag. Water cooled provides a forgiving flexible operating envelope. What you want in a fighter. Downside, more complicated. Upside better performance means kill enemy better.

Air cooled radials. The drag penalty is less as the engine size increases. More reliable as long as you stay inside the design envelop. Scales up better than inline water cooled engines. Better suited for multi-engined bombers with a well defined mission profile.

At the end of the war though it was obvious that turbojets were the future for fighters. Which is why water cooled engines went away. Radials though are more efficient at lower speeds than early turbojets which is why they persisted.

> I worry about people who use a word like 'superior' without any dimensions.

Well, let me clarify that as "superior in whatever dimensions the designers of those post-WWII piston engined planes considered important". Hope that helps.

> I can think of plenty of reasons the simpler design with one less failure mode might dominate production during the war, without being the obviously better choice given peacetime applications and seventy years of technical advances.

To be clear, I was writing about the immediate post-WWII environment before jets made piston engines obsolete except for the lowest end of the market. Aviation piston engine development pretty much stopped then.

Sure, a "modern" aviation piston engine for the GA market will quite likely be a water cooled design, if for no other reason that there is so little R&D money available for piston aviation engine development that most likely it's going to be based on a car engine.

A) the highest performance aircraft were all liquid cooled

B) combat aircraft have to deal with bullet holes

> A) the highest performance aircraft were all liquid cooled

Well, how do you define high performance? Judging by speed at least, Tempest Mk II, Sea Fury, Bearcat, and P-47M are among the fastest piston engined planes ever made.

> B) combat aircraft have to deal with bullet holes

Sure. But an engine that lacks a critical subsystem by design (say, a liquid cooling system with pumps, pipes, radiators etc.), all else being equal, is less failure prone than an engine that has it. Whether that failure happens due to shells or mechanical failure.

Classic scalability issue, those engines were HUGE compared to general aviation so all the rules about shock cooling and surface area to volume ratios don't apply unchanged to engines a thirtieth the size.

I'm not sure. Surface vs. volume is certainly and interesting thing that explains many scaling phenomena, but in this case, those huge radials had huge fins as well (correspondingly huger than fins on smaller engines in order to cool the much higher mass) to cool them under normal operations. So those same fins would equally rapidly cool the engine when descending quickly at idle power. So shock cooling is certainly an issue with big radials as well. Now I don't know the exact scaling relation, but I'd guess it's more similar to a smaller engine than a straightforward surface/volume scaling would imply.

Or to put it another way, the surface area of the cooling fins is not proportional to the surface area of the cylinders without any fins, but to the power output of the engine.

I think people are trying to balance in a false dychotomy here

You could have liquid cooling, but it could be different from a car liquid cooling. For example, maybe you don't need pumps and could rely on a sturdy passive convection system. (Also include some fail-safe aspects)

The concept doesn't need to be married to modern automobile design, agreed.

Much like the transition motorcycle engine manufacturers made, moving away from air cooling in the late 70's. The first innovation being under piston oil jet cooling and then moving progressively to water cooling.

Oil cooling offers little additional risk or complication over air cooled designs, but there are limitations on liner/piston temperatures and additional vapors which increase maintenance that don't exist with water cooling.

It really comes down to whether it seems reasonable to trade on some risk for economy, but ultimately recip engine flight isn't efficient anyway

I’d agree with most of this but frankly when was the last time your car engine stopped on the highway? Or was hard to start because it was hot, or cold, or just because? These problems are solved in cars. The old Cessna 172 models I’ve flown all continue to have these issues, even a friends SR22 from the mid 2000s was a nightmare.

Plane engines are well understood, but they are old and clumsy designs that could be drastically improved upon.

I can't remember the last time I commuted and didn't see a car broken down on the side of the road.

But thousands of cars pass that way each day, and one breaks down. The (admittedly anecdotal) issue rate described for planes sounded much higher.

The anecdotes above I read as difficulty getting an airplane engine started, which is definitely true compared to a modern car engine. Even using proper technique, mine can be frustrating to get and stay started after a fuel stop. (It’s a vapor lock issue that arises from heat-soaking while stopped for fueling, not something that makes for a safety-of-flight issue.)

It's more to do with the relative consequences. A car engine goes out and you cal AAA, an airplane engine goes out and you have a serious problem.

Not necessarily engine problems.

That is freaking wild to me.

Hmmm. Something to do with lack of state warrant of fitness in US?

Aircraft engines are running on full load for almost all the time, with added load during take off. Car engines are not, a modern car engine would blow up running under the same load patterns then aircraft engines.

And sincr ICE engines are dying bread when it comes to aircraft, why bother if the current ones work perfectly fine for what they are supposed to do?

> And since ICE engines are dying bread when it comes to aircraft, [...]

Are they actually? I'd expect air-travel (and rockets) to remain the last holdouts for combustion engines for quite a while to come.

Cars will definitely move to being electric.

Big ships, maybe too?

Wouldn't surprise me if aviation engines would move to turbines (see TurbAero and Turbotech for turboprops designed for the GA end of the market), and electric for short range. Leaving little if any space for piston engines. Though of course existing planes aren't going away for a long time.

Modern aircraft use turbines, either as turboprops or jet engines. Those burn kerosene.

And yet many light aircraft are powered by very simply-adapted car engines.

And those are following totally different certification requirements.

The most frequent problems I’ve had with cars in the last 20 years have been engine cooling systems and battery charging.

When was the last time an issue with the car engine caused you to fall out of the sky?

> My engine might last for only 2000 flight hours between overhauls. In those 2000 flight hours, it's likely to burn ~30K gallons of fuel. Taking that as a proxy for the total energy generated, 30K gallons of fuel will take a typical car almost a million miles. How many cars reach 1 million miles without major engine work?

I guess you could still take car engines, but overhaul them more often? Might still come out cheaper in the end?

If you wanted to use an auto engine it would probably be a truck engine. Most car engines aren’t designed to be run at lets say 5,000rpms for an hour or so at a time. It’s the same reason inboard/outboard engines in boats use big and small block GM designed truck engines (Merc and Volvo).

A truck engine is a great comparison point, because you can look at modern trucks for a perfect example of this.

A Ford F-250 through F-450 pickup truck with the 6.7L "Power Stroke" diesel is rated for 475 HP and 1050 lb-ft of torque.

The same engine in the same basic truck, but in commercial chassis-cab form, is rated for 330 HP and 825 lb-ft of torque.

Step up to the medium duty F-650/750 chassis with a much larger cooling system and that engine is now rated for 270 HP and 700 lb-ft of torque, with optional software upgrades available for 300/725 or 330/750 configurations.

The same applies to their gas motor, the pickup trucks get the 7.3L "Godzilla" engine with 430 HP and 475 lb-ft where the chassis-cabs and medium duty trucks get a 335 HP/468 lb-ft tune.

The harder and more consistently the truck is expected to be worked the less power the engine is rated for.

This isn't just a Ford thing either, GM and Ram also derate their commercial chassis compared to the pickups and the multiple power level thing on the medium duty diesels is common industry practice. Often the highest horsepower packages on larger diesels will be restricted to RV and/or emergency response applications where short bursts of power are more important than the ability to run hard for hours on end.

As a point of reference to airplane engines, my first airplane made 230 HP @2700 RPM from 470 cubic inches (7.7 liters). My current airplane makes 325 HP @2700 RPM from 550 ci (9 liters).

Yes. I was being a bit lax when I said 'car engine'. I basically meant any land transport engine with a large production run.

(Though looking at ship engines might also be interesting. I assume they are heavier and bulkier than car or truck engines, but they probably can also run at high load for a long time? I don't know anything about them..)

You wouldn’t want to run them wide open throttle for a long time but usually they give you a cruise RPM suggestion for optimal gas/speed. People make 20-30 miles runs offshore in smaller boats running them close to wide open for hours at a time.

Yes I think they are heavier than their truck counterparts. Most are raw water cooled so they have intakes/risers and shoot water out the exhaust.

The diesel ship engines are beasts, can take a beating, and run for 10x as many hours as a gas engine. It looks like they are too heavy for aircraft but there are some Diesel engine manufacturers listed on Wikipedia.

>How many cars reach 1 million miles without major engine work?

I can think of about a dozen engine platforms off the top of my head that would reliably get there or damn close if they got the same kind of maintenance/inspection schedule that a GA aircraft gets.

> How many cars reach 1 million miles without major engine work?

Every old Mercedes taxi.

Every Skoda Octavia taxi.

Problem is it is a niche too small to support the customization needed. There are plenty of engines that are better in one aspect and we know that all needed aspects can be combined into one, but the engineering cost to do that is so high that you couldn't charge a reasonable price for the engine and still break even on R&D.

Maybe this guy's video:

https://www.youtube.com/watch?v=_k1TQGK3mZI

I took their in-person class in Ada, OK back in the day. Highly recommended the training material. https://www.advancedpilot.com/

They have a great test bed for validating their science.

When I read your comment too quickly, I saw Ada training. [1] Of course, you meant what you wrote, Ada, OK! [2]

[1] https://en.wikipedia.org/wiki/Ada_(programming_language)

[2] https://adaok.com/

I took that same course (in Fall 2013 I think); it was excellent.

Sadly, both John and Walter have passed away, leaving only George as the last amigo standing.

I live by lake union in Seattle, and I love watching the seaplanes taking off and landing. It's high time that there's a lead-free option. Seattle doesn't need that kind of lead in its air.

As someone who flies GA aircraft out of Boeing field (KBFI) I also welcome this change. I don't want more leaded fuel on my hands. The lead can be absorbed by skin.

Have you seen this Veritasium video about the man who came up with adding tetraethyllead to gasonline and it's negative impact on humanity?

https://www.youtube.com/watch?v=IV3dnLzthDA

Given how dangerous lead is in even the tiniest quantities it is really surprising that there has not been more pressure to change that.

Don't have time for the video, but if that was Thomas Midgley, he was quite the one-man environmental catastrophe.

https://en.wikipedia.org/wiki/Thomas_Midgley_Jr.

It is indeed. The video (which I just happened upon yesterday) does a great job of describing his impact on humanity and it was interesting to learn that prop planes were still allowed to use leaded gasoline--I had no idea. Ironic he died by strangulating himself in one of his own inventions.

Every time I hang out in Georgetown and a plane flies overhead I have this same thought.

(ish)

I used to live near there too. I was today years old when I learned those planes still use leaded fuel. Oof. Glad that's getting rectified.... finally.

The piston engines still use "low lead" fuel. The turboprops run on jet fuel.

Some piston engines use jet fuel too (Diamond planes in particular). Some use automotive gas.

Piston engines that run on jet fuel are diesels. Nothing wrong with that and diesels are very efficient. But diesel GA engines have a long history of problems. Diamond is rare in seeming to have overcome those problems.

I spoke with a coordinator at Kenmore Air about a private charter a few months back. Over 90% of their flights are on their higher capacity DHC-3 de Havilland Otters so that they can fill seats more efficiently. The Beaver runs on leaded gas, but the Otters do not.

The otters are all turbine now, which runs essentially pure kerosene.

The rotary engine tech in a DHC beaver is barely changed from WW2 era rotary piston engines... Assuming we're not talking about the more modern turbine beavers and otters.

The turbine ones already run on Jet-A

And I think that Kenmore Air is the main operator out of Lake Union, and they're mostly or all turbine.

Given that the DHC-2 Beaver was introduced in 1948, that’s not too surprising.

Rotary or radial?

Radial.

My brain was clearly not working right when I wrote that, though the mental image of a Mazda RX-7 engine strapped to the front of a beaver is certainly amusing.

In the early days of aviation there were actually rotary engines that were like radials, but where the entire engine rotated: https://en.wikipedia.org/wiki/Rotary_engine

Wonder if anybody ever tried that. Somebody must have, decided the gallons per hour was ridiculously high, and abandoned the idea.

There have been many attempts with the 13B. One I saw it all worked, except the exhaust system. Builder went through everything, built 3 or 4 of them. The last was made out of titanium welded by guys who worked for a defense contractor.

Failed in flight like the rest of them. He ended up with a lycoming.

In a similar way, there are kit planes which use EJ and EA series Subaru engines. These tend to be a bit more fuel efficient than Mazda rotaries though.

They're used in drones

https://www.aieuk.com/wankel-rotary-uav-engines/

I live near the south end of Lake Washington near Renton Airport and always cringe when those small piston engined planes take off over the lake and homes. I would be afraid of growing a garden in the homes around the airport. I see people fishing in the lake next to signs warning about the risk of eating too much fish from the lake. It is high time we got rid of this last remnant of leaded gas.

I haven’t looked but wonder if there is a measurement available and how bad it is comparatively.

Lived there for a while as well. Didn’t think about that…

Wow, I can't believe they got it done. After watching all the Paul Bertorelli videos on it I assumed it would be stuck in bureaucracy from here to eternity. Incredible work by the whole team, very exciting.

Agreed, but sadly it's still a niche fuel. Although I have to admit that for a (hopefully) brief time, we've seen airplane gas and corner-gas-station gas the same price in California!

I think that unless a large number of GA airplanes can run on true automotive gas (which means gasohol now) in the near future, GA is doomed. This is something the industry should have been tackling with abandon for the last 20 years. But they failed to take lead seriously for the last 50, so can we expect better?

Maybe. I think there is one Rotax engine that can run on gosohol (10% ethanol). We need much more of that, and widespread adoption of fuel injection and electronic ignition ASAP.

Oh, and we need more people to stand up for their local airports. Corrupt local politicians, developers, and fake-NIMBY land speculators are all arrayed to destroy our nation's aviation infrastructure for personal profit. Even airlines are in on it. Innovations like this unleaded fuel and electrification will cease if there's no place to deploy them.

So, I think GA is great in principle, and I use some products from it (mostly digital elevation data from airborne lidar, which is amazing). But it seems to have a very large component of taxpayers footing the bill for rich guys' toys/playgrounds (particularly for the infrastructure, not for planes themselves); this opinion has been influenced by talking with people I consider honest who have worked in municipal/county government, but I don't have any numbers. Can the many GA enthusiasts here give provide some insight into the public benefit from GA? Please note that I am sort of asking to be convinced and am not being antagonistic.

For one, there's no country in the world where the GA scene is like it is in the US. There's airports everywhere and flying is mostly accessible. As such, like US universities attract the world's students, the US GA airports attract a _ton_ of foreign pilot students.

That's just one angle. Another angle: the US is a lame duck in term of mass transit infrastructure like trains. So development and advancements in those fields occurs elsewhere, like in Europe and Asia. But in the case of aviation infrastructure, US is miles ahead. And as a result, a lot more aerospace stuff happens in the US than anywhere else. It's not as directly useful to the general public as inter-city trains, but it does have a lot of positive side effects for the economy and industries.

Perhaps one day, flying will simplify and become commonplace for the average person, like cars that were, as an industry, born in the US. And then on that day, it'll seem pretty smart to have nurtured general aviation and allowed aerospace to germinate.

GA looks like a rich people's hobby, and it sort of is. But it's not "10M$ in the bank" rich. The middle (as a treat) and upper class can afford to fly GA. In most other countries, that's just too out of reach for most people, it's not realistically in the cards unless you want to have a career in that field.

> But it seems to have a very large component of taxpayers footing the bill for rich guys' toys/playgrounds

Eh, most are not that rich. There's a wide range of plane prices. From Honda Civic money, to millions of dollars.

GA encompasses a whole bunch of activities. You do have the rich doctors flying in twins, yes. You also have Angel Flights, Pilots N Paws providing volunteer assistance for people and animals. You have flight training (we are going through a pilot shortage). Aero(photography/grammetry). Sightseeing flights (tourism industry). Transportation of people and cargo to remote areas. Etc.

In some cases the revenue generated doesn't pay for the infrastructure. That's why so many airports have closed in the last couple of decades.

There are also people just flying for fun. Usually in very cheap and economical planes burning single digit gallons per hour. Their gallon/mile figure can be pretty good even compared to cars (let alone SUVs).

Lot of the aerophotography stuff is switching to UAVs these days though, it's easier to obtain pilots and the capability of modern UAV platforms is just amazing.

AFAIK no privately available UAV system can match the range and flexibility for GA aircraft. For example photographing things that are dozens of miles from any road or airport. If I’m wrong I’d be interested to learn more.

A DJI Matrice 300 can fly for an hour, at a distance of up to 15km [1]. Agreed, it's not going to be useful in the extreme outback, but enough to cover a lot of use cases in areas near civilization.

[1] https://www.dji.com/uk/matrice-300/specs

Generally there are different classes of aerophoto ops and most UAVs so far seem about opening up markets that were previously closed due to high prices

In addition to air ambulance/medevac, aerial firefighting, overnight package intake and delivery, and medical lab test samples are all things that I think have fairly broad benefit if not widespread support and rely heavily on airports other than the 100 largest in the US.

In times of natural disaster, GA airplanes are often delivering support and supplies using these non-primary airports. This often happens before the larger agencies can spin up and post-hurricane can often reach areas before the roads are fully open.

In rural areas, like Alaska, they’re even more utilitarian.

Most of the commercial pilots now got a lot of their 1500 required hours in some of the activities around these small airfields.

And of course, there’s all the use of private aviation in support of businesses (logistics to prevent line shutdowns or move urgently needed repair crews to a factory).

It’s not just rich folks buzzing around to kill time or flying around in their private jets. (Neither is that zero of it.)

People from the lower 48 can't seem to conceive how important GA is to Alaska. If you grounded all GA planes in Alaska, thousands of people would start dying of starvation within a couple of weeks. There are simply no roads to most of rural Alaska.

At that point the question does arise: is it long-term sustainable to keep such communities artificially alive, or would it make more sense to pay off their residents to move somewhere where they can be supplied with resources way more efficiently?

GA in Alaska requires less public infrastructure than elsewhere because there are more planes that can land on and take off from water, snow, and unpaved surfaces.

Also Alaska can easily afford basic infrastructure, heck they pay an annual stipend to permanent residents.

> Also Alaska can easily afford basic infrastructure, heck they pay an annual stipend to permanent residents.

The question is not if they can afford it because they obviously can, the question is if this is long-term sustainable - not just from a CO2 emissions point, but you also need pilots, the planes or boats themselves, and all of that to supply cities that don't even manage to get 100 residents [per 1, at least 23 fall below that limit]?!

Maybe just accept for once that there are areas so remote it isn't worth the effort to supply them. We should return these areas to nature.

[1] https://en.wikipedia.org/wiki/List_of_cities_in_Alaska

Many of these communities have been there for hundreds of years. It was their homeland long before the United States existed. Do we force them off their land because it's more convenient for us? Do we force them to revert to a primitive lifestyle with no access to modern conveniences like medical care, a good education, food in lean times, electricity, or communication?

Or do we let them continue to have the best of both worlds at the cost of an airplane once a month? I vote for option 3.

What's "artificial" about using planes to transport food instead of trucks?

The people making these claims typically don't know anyone in GA or anything about their local airport. The taxpayers footing the bill for GA are GA USERS. GA pays way higher fuel taxes than the AIRLINES do.

A large proportion (the majority?) of the people in GA are not rich. They simply choose to spend their money on flying, instead of on leasing a new giant SUV every three years. My flight instructor had to SAVE UP to buy a crummy portable GPS... and 15 years later he still doesn't own a plane.

And that's not counting the entire industry's worth of people whose living depends on servicing aviation. Mechanics, painters, upholsterers, you name it. And this is a mostly DOMESTIC industry. It's despicable that GA doesn't enjoy more support from everyone, from legislators on down to Joe Plumber.

"You're posting too fast. Please slow down. Thanks."

Oh yeah, Hacker News? Then WHY IS THE REPLY BUTTON ENABLED? Why do you allow people to waste their time typing out a question or comment and THEN say, OH NO YOU CAN'T POST? Then you jerks "shadow ban" people who point out your offensive behavior.

When I worked retail a long time ago, one of the assistant managers flew every weekend.

He wasn’t rich. Now he’s making a good living flying for Southwest iirc.

There are places in America that are a hundred or more miles away from the nearest hospital. These small airports are vital to rural healthcare.

Sure, all those people could move to more populated places, but then you'd have nothing to eat.

Source: The company I work for is slightly involved with air ambulances.

> Agreed, but sadly it's still a niche fuel. ... I think that unless a large number of GA airplanes can run on true automotive gas (which means gasohol now) in the near future, GA is doomed.

There are several problems with gasohol outside the core engine, from compatibility with fuel systems (bladders etc.), to phase separation, to vapor lock, to hygroscopicity. I'm sure that can be designed around, but it's not a drop-in replacement in planes designed for avgas.

If you want an abundant and affordable fuel, in the aviation world that's Jet A(-1). There's some limited success with Jet A burning diesel engines for the GA market (Thielert (or whatever they're called today) and Austro mainly).

Personally I think it would be cool if turbines suitable for GA would be developed. Currently turbines cost an arm and a leg, but I think partially that is an effect of development focused on power/weight and fuel efficiency, cost be damned. That might suit commercial and military use, but not GA. And yes, turbines don't scale down very well either. Still, a turbine that would have an upfront cost competitive with current GA engines would be very attractive, even if it would come at a cost in fuel efficiency. That would be, I think, more than compensated by the power/weight and safety advantages, as well as fuel availability and affordability. I think there are a couple of companies working in this space (TurbAero and Turbotech that I'm aware of, maybe others as well), we'll see if any of them ever come to fruition.

A big problem with turbines is overhauls and how they are calculated.

For piston engines, overhaul time is calculated from amount of hours operated. For turbine engines it is calculated from amount of hours and amount of start-stop cycles, whichever is reached first. And in GA, you have short flights and many cycles, which results in overhauls being much more common and expensive.

Yep, I wouldn't expect the transition to have occurred overnight. But after several decades of experience in automotive applications, I'd think the GA fleet could have been adapted by now if the industry had taken it seriously.

I also realize that the regulatory regime has stifled progress. It seems a bit better now, but it may be too late.

“George Braly, chief engineer at GAMI, said the fuel can be made with components “that are found inside the fence of any refinery.””

Now, that quote comes from the principal at GAMI and in a GAMI newsletter, but over the last decade and a half of following this, I’ve found him to be pretty damned straightforward.

https://gami.com/g100ul/AvGas0211.pdf

Lowering the financial barrier to entry would help. Idk how, but part of the industry's problem is that people who want to learn to fly can't afford to.

Fuel costs are a huge part of it.

I don’t want more incompetent people flying planes, so I’m content to keep it expensive enough to keep out people that aren’t going to take it deadly serious - because it is. Expense doesn’t guarantee that, of course, but it limits the collateral damage.

I've been flying for almost 25 years. I haven't seen much correlation between income/wealth and how seriously pilots take aviation.

I've seen rich people take it extremely seriously and with great attention to detail and safety, just the same as I've seen people who struggle to get the money together to go flying do the same.

I've also seen a lot of rich, successful, type-A people just not have the mindset of "Oh shit, this could easily kill me" because they've been successful at some other aspect of life.

You fly jets long enough, something like this happens.

There might be a correlation in the other direction. Successful and wealthy people have a propensity to buying more expensive and flashier planes, which generally equates to faster, which is something an inexperienced pilot should always try to avoid.

Wait until you hear how much eScooters cost

> Oh, and we need more people to stand up for their local airports. Corrupt local politicians, developers, and fake-NIMBY land speculators are all arrayed to destroy our nation's aviation infrastructure for personal profit.

I'm skeptical the public will stand up for GA. At least from my perspective, progressives and much of the left would prefer the industry fade away entirely. It's been in decline for decades and with the new trend of public carbon shaming I don't think you'll get many who come out in support of it beyond rural conservatives.

Not all of us are unknowing of how interconnected GA capability is to many other areas of economy, even if we live in countries with less such impact.

Now, landlords looking for more land (especially well communicated) for apartments are very happy to push for everything that removes airports so long as they can reuse the land afterwards...

Airports consume an awful lot of land directly, cause severe pollution issues for even more land (by noise, mostly) and severely limit land use in the flight paths due to safety concerns.

Building out actually capable high speed and regional rail infrastructure is the way forward.

GA doesn't handle mass transport that can switch to railways, so it's a bit moot point.

So GA infrastructure and railway infrastructure is effectively orthogonal and you need both (passenger/cargo airports also greatly benefit from having rail links!)

If you get high-speed rail to be competitive with flying a 175 knot piston airplane, piston GA travel will fall off a lot. I love flying, but I’d switch.

French TGV routinely has service speeds of 320 km/h [1] which is about the same as your plane, same for the Japanese Shinkansen [2]. Technically, speeds exceeding 500 km/h on close-to-stock rail are possible, the French have done that as well [3].

[1] https://de.wikipedia.org/wiki/TGV#Allgemein

[2] https://en.wikipedia.org/wiki/T%C5%8Dhoku_Shinkansen

[3] https://www.hsrail.org/worlds-fastest-trains

I’ve ridden the TGV and Shinkansen. They don’t go to my kids’ grandparents’ house, but when they do (or hell, even something like the German ICE does), I’ll use them. I’m not anti-train; I am anti-impractical-train.

Today, Amtrak takes 22.5-27 hours to go 642 miles Boston to Columbus, OH. I can drive there in around half the time (likely less once you add the time to/from train stations) or fly there in 1/4 the time.

That’s a perfect distance for actual high-speed rail.

To the other grandparents, Amtrak can get me 657 miles in 18.5 hours to a place about 100 miles from their house. That leaves once per day at 9:30 PM and still leaves me 2 hours drive from their house (which is in a tourist area near the ocean, not some unpopulated area). Another perfect distance for HSR where I can drive there in less than half the time or fly there in around 1/4 the time Amtrak takes today.

I share your skepticism, but will still work to oppose what contributes to it.

And turbochargers. Cars benefit from turbos and they don't go from lean to rich to lean every day. Planes do that several times on every trip, and can benefit from turbos much more.

The logical conclusion of that argument is to scale up the turbo, rip out the big chunking reciprocating mass of metal and just inject fuel directly in a can ahead of the turbo. ;)

(Oh, and since your gas generator no longer has a prop shaft sticking out of it, you need to mount the shaft on the turbo instead. Possibly on a separate turbine wheel.)

Hey, I seem to recall somebody tried that :-)

The distinction of course is about reliability and cost. If a turbo quits, your piston engine can probably still limp along. But if your turbine quits, the houses are gonna get bigger...

I imagine the idea is now that it is approved for every piston engine then the EPA can ban 100LL and airports everywhere can switch to 100UL instead.

Ethanol free gas is widely available (In Michigan stations call it Rec fuel).

Are you concerned about cost, availability, some other factor?

I disagree. I haven't seen alcohol-free gas in decades, in Los Angeles, Chicago, or anywhere else that I can remember.

Availability is limited in many places. California, Massachusetts and New Jersey have very few stations.

This is great! Expect the EPA and the FAA to finally ban 100LL, which will be a great boon for everyone. Note, you will require an STC, but not poising yourself with lead will probably net out the costs in the long run.

* I am a pilot of piston engines, and I really don't like 100LL being the only option

ul94 has been around for a year or so (I've had the stc since last december), but yeah for high compression engines, it was 100LL or nothing. I'm hoping the stc is comparably priced, $100 or so.

this is really awesome.

edit to add: for the non av geeks, an stc is a supplemental type certificate. it's basically an faa stamp that says, "this aircraft has been changed from when it was initially certified, but it's an approved change"

https://en.wikipedia.org/wiki/Supplemental_type_certificate

George Braly in the video interview indicated it would be similarly priced to the Petersen STC, which used to be $1/rated HP and now appears to be $2/rated HP.

In short: it’s no barrier whatsoever to adoption.

so a little more expensive than the swift stc but yeah still totally worth it.

Nice. I hope this ushers approvals across the planet. I am just starting the journey to private license in Canada and I kinda hate how inefficient, but also how primitive and unhealthy the engines and fuel are :-/

The engines are actually fairly efficient. Unlike an automobile engine, they really only operate in a very narrow range and are usually run at a substantial fraction of full power (60% or more).

Automobile engines are very challenging because the power demands are highly variable and they can’t be optimized for any specific load.

Amusingly enough the Piper Cherokee I flew got better ground gas mileage than the '66 Fury I had at the time.

Wow, that’s a hilarious stat. How is that even… possible?

The '66 Fury weighs in at 3500 pounds and got about 10-12 miles per gallon based on my pump-to-pump odometer tests.

The Piper Cherokee PA-28-140 weighs a petite 2150 pounds (max loaded weight) and burns 10 gallons an hour and would do about 115 KIAS, which translated to roughly 130 miles per hour ground speed, which is 13 miles per gallon.

It would do even better if you flew for efficiency, but since rental was by hours of engine time wet (I didn't pay for fuel and would be reimbursed for fuel purchased), there was really no reason to not throttle that baby up to full rental power.

> there was really no reason to not throttle that baby up to full rental power.

The reason is to reduce pollution, but that's obviously no concern at all for most GA pilots and passengers.

> Wow, that’s a hilarious stat. How is that even… possible?

There's nothing magical about flight. Take-off takes a bunch of energy. Maintaining that energy, not so much. Planes are pretty aerodynamic, imagine that :) Some are much lighter than cars since every pound counts. To the point that people often opt to not have AC (if it's even an option) to save a few pounds.

They will cover a lot of ground in the same amount of time. That helps even more.

Not all planes are that economical, of course. But some are indeed hilarious. Check ultralights (or microlights as they are known in Europe).

A/C is amusing because it’s only needed on the ground - once you’re at cruise you can just open the window if it’s too hot - the outside air temp will almost always be pretty Low.

>There's nothing magical about flight. Take-off takes a bunch of energy. Maintaining that energy, not so much.

Yep, take-off and ascent burns a lot of fuel, much more for the time duration than cruising. It's too bad there isn't a way of recovering some of that energy when descending, similar to how electric cars recover energy when braking.

> It's too bad there isn't a way of recovering some of that energy when descending, similar to how electric cars recover energy when braking.

A descent is a pretty efficient conversion between potential energy (altitude) and kinetic energy (speed/horizontal distance) so you get it back. Your RPM difference between cruise and descent is a proxy for your recovered energy. An engine out glide/landing is the extreme demonstration of this.

>It's too bad there isn't a way of recovering some of that energy when descending

But that's exactly what happens already. Point the aircraft down and it will pick up speed.

But you don't tend to want to land at enormous speed.

All kinds of planes have by necessity far better drag coefficients than cars. A truck, SUV, even a minicar is like a brick wall moving at high speeds while a plane essentially slices through the air like a knife.

Additionally, planes tend to fly at constant and pretty high speed for most of their operation, while a car has a lot of acceleration and deceleration going on. Planes can also use wind thermals to change altitude (sail planes can only use that!) or can stay at the same altitude while a car driving below it is stuck with the geography (i.e. it has to follow and climb hills).

1960s cars were terribly inefficient is a big part of the story.

It's quite possible for a plane to net higher mileage than many cars today, especially light-sport planes that only burn 5 gallons per hour or so.

Yes, but this was while taxiing.

“Ground gas mileage” meant converting the KIAS to mph on the ground (while flying).

I never checked mpg while taxiing but the motor would be almost idle.

No, not while taxiing. Who the fuck are you to misrepresent what I said?

I said GALLONS PER HOUR. If you're taxiing for hours, you're doing it wrong.

I guess it depends. I understand some ultralights and new airplanes may be efficient. But it is my understanding that a Cessna 172 lycoming is basically 50-70 years old, depending on how you count, and horribly inefficient, and completely prevalent. Faa certification for new engines is such that innovation is stifled. I mean it took the industry what, 3-4 decades and counting, to phase out leaded fuel which we all agree is God awful :-0

That's my point, the Lycoming (while an old design) is not all that inefficient.

A Cessna 172 burns about 8 gallons per hour and travels at 125 knots, or about 140 mph. That's the equivalent of about 18 mpg.

There's been an enormous improvement in automobile engine efficiency in the past 30 years, and most of that has come from optimizing engines and transmissions to minimize their fuel consumption under light load, while still giving them enough peak power capacity to accelerate quickly, tow a heavy load up a hill when needed, etc.

In comparison, an aircraft engine spends very little time "idling" and sees very little change in load over the course of a flight. It just runs at a fixed speed and power setting for most of the time. There isn't that much to optimize or improve.

There's tons to optimize!

Timing is a big one; magento fired engines have fixed timing. The engines can't remove or add timing to get more power.

Fuel ratios are determined by the pilot with current Lycoming and Continentals. Why should the pilot need to worry about this? EFI has been around for 40 years now and would help decrease the cognitive load on the pilot. Like, how many engines have cooked valves because the pilot (or student) forgot to richen the mixture before descending?

Cooling is a huge one. There are a few liquid cooled aircraft engines and they just make everything easier. The engines are more reliable, and it also removes a carbon monoxide poisoning risk due to corrosion in the exhaust cuff.

Yeah, a Cessna can get better fuel economy than a car traveling at 140mph but it could be _so much better_ than what it is. And not just better fuel economy, but better all around experience for the pilots (lower cognitive load), and owners (lower cost of living, more reliable engines).

Many racecars and boats also run fixed timing. Variable timing is needed when the load is variable. If the load is constant, the timing can be fixed.

Modern engine monitors have given us more insight than ever into engine operation and I don’t find the engine management particularly taxing.

After initial takeoff, I’m likely to set the power (throttle, RPM, and fuel mixture) at 1000’ above the ground and not touch it again for 4 hours (when it’s time to transition to landing).

That's still not particularly efficient. There's still variable load: circuit work, obstacles to climb over, flying around (or into) airspace. Air density isn't fixed, your engine may be running richer or leaner than you need to be. Pilots aren't nearly as efficient as setting the mixture as a computer, nor are the currently used single injector (or carburetor) as efficient as multi-point, or direct, fuel injection.

GAMI got their start selling more balanced fuel injectors, but there's only so much you can do when you squirt gas into a tube and hope that it makes it equally to all cylinders.

There's a _lot_ on the table in terms of efficiency and it puzzles me why there has been almost zero progress on this front.

I’m not disputing that GA engines could be significantly improved and modernized in numerous ways. But none of the improvements you mention actually relate to efficiency at cruise power.

I feel like I've said this already but carbureted and mechanical FI in aircraft often do not have even fuel distribution; that is not all cylinders receive the same amount of fuel. If you have an injector on (in) each cylinder, you do. If you have O2 sensors on each sensor the ECU can adjust mixture on the fly and ensure that each cylinder is running optimally

The SDS EFI people claim up to a 20% fuel effiency gain by going to multipoint fuel injection on existing engines.

If you have consistent cooling (hey, guess what, those rear cylinders on an O-540 are running hotter than the fronts), you can run more timing and more compression.

More timing, more compression, less fuel = more efficiency. Basically everything I'm talking about is more cruise power efficiency!

The premise of GAMI injectors is that not all cylinders are supposed to receive the same amount of fuel, because they don’t all receive the same amount of air. The intent is to achieve the same air-fuel ratio, which means having different injector sizes for different cylinders.

I have GAMIs; they are one per cylinder, just like the factory injectors were, but provide closer matched air-fuel ratios. I also have per-cylinder EGT and CHT instruments and have measured less than 0.3gph spread (about 2%) between the leanest and richest cylinder. Modern cars are rarely measuring per-cylinder fuel, but rather measuring the average of half or all the cylinders and using that to adjust short and long term fuel trims.

Youve added a pretty sophisticated complication to that engine. What happens if the O2 sensor fails in flight?

Also, I dont know that you want to increase the compression on the hot cylinder. If anything Id run rich to make sure it doesnt knock

>better all around experience for the pilots (lower cognitive load)

Can you elaborate further on this? Is this lower cognitive load because the engine is more reliable?

Lower cognitive load because you as the pilot wouldn't need to manually set the fuel mixture

In the gallery here: https://cessnaowner.org/pilots-perspective-cessna-340/ The red controls are the mixture and have to be manually adjusted by the pilot, so you could potentially remove 1/3 of the controls from that area

Plus the associated gauges too (cylinder head temperature, exhaust gas temperature, fuel flow).

So what I'm hearing is... get a Diamond? :)

Aren't Cessna 172s and other small planes so efficient that the optimization strategy is to electrify them?

It's still early days with short flying time, but electric planes are a thing: https://en.wikipedia.org/wiki/Pipistrel_Velis_Electro

Flight training is seemingly the first market:

"The eDA40 will compete with Bye Aerospace’s new all-electric eFlyer 2 and eFlyer 4 aircraft, which have been securing significant preorders in the flight training market."

https://www.futureflight.aero/news-article/2021-10-13/diamon...

Sort of. One feature of fuels is that the planes gets lighter as you burn it. You can also choose not to fill it up in order to have more cargo (or passengers). Batteries don't offer the same flexibility, so they will have to be pretty power dense to provide the same utility.

I'm still rooting for electrification there too. I can't imagine an electric drive train to cost as much as a Lycoming/Continental engine overhaul.

This is especially important in small aircraft, as many have ZERO cargo capacity (just enough for the pilot - no passengers) at full fuel load.

No. Energy density for batteries is at least an order of magnitude off where it needs to be for manned flight.

The C172 (most common small airplane) has a Lycoming 4-cylinder engine of various sizes throughout the years. A representative engine, the O-320, is around 89% as efficient as traditional (non-hybrid, non-Atkinson) ICE automobile at turning gasoline into productive work.

I don’t view an 11% spread as “horribly inefficient” given the need for many redundant systems, air-cooling, high diameter pistons, and relatively low RPM.

0-https://michaelsoroka.com/2014/03/26/are-airplane-engines-in...

They lack a bunch of emissions control equipment like fuel injection, catalytic converters, and the like.

They are 60's or maybe 80's car engines that are still made since nobody in GA wants to pay for better ones.

> since nobody in GA wants to pay for better ones.

Since nobody wants to pay to certify better ones.

The engine in a Cessna 172 is going to run you $20-40k (20k rebuilt, 40k new afaict - check out [0]) - far more expensive than an automobile engine with 'equivalent' performance. The difference is that the Lycoming is certified by the FAA for use with your airframe. (And it'll work in whatever conditions you care to name, and with a car engine that's only a 'probably')

0: https://www.coronaengines.com/In-Stock

> They lack a bunch of emissions control equipment like fuel injection, catalytic converters, and the like.

Yeah unfortunately the weight and size of those systems is prohibitive for most light aircraft. Plus catalytic converters and oxygen sensors for closed loop efi can’t be used with leaded fuel.

> They are 60's or maybe 80's car engines that are still made since nobody in GA wants to pay for better ones.

The Lycoming and continental engines in most of the fleet were certified in the early 50s. A few were in the early 60s. That means they were designed in the 40s and 50s!

that's what transmissions are for though.

variable valve timing also helps.

EDIT: This comment is about automobile engines.

But until very recently transmissions worked on steps and could never keep the engine at peak efficiency.

CVTs are fairly recent and people managed to stifle it by adding simulated gears.

Transmissions == variable pitch in aircraft.

Transmissions also lose a lot of energy.

>>Nice. I hope this ushers approvals across the planet.

TBH - this will just shift sales of that fuel type to the still "dirty" countries fuel supplies where banning it will not happen, sadly.

Oil companies are not our friends.

I was just thinking about this yesterday; the amount of human infrastructure built around the petro-chem industry:: Land use, pollution, corruption, just plain evil, etc...

Along with the fact they lobby and get subsidies and everything where the Earth provides their raw input for "free" and the rest of the world suffers.

/r/fuckcars, but seriously - Petro-chem, for all the great things industrial revolution has given us, is the most insidious industry on the planet. Look at fucking ARAMCO's cap/profits last year. Largest company on the planet. BigOil is a nightmare.

100LL is blended regionally to serve the piston engine demand.

I expect that blending will switch to G100UL and there’s nothing remaining to export to “‘dirty’ countries”. As a consequence, the one remaining source of TEL in the world will close down within a decade. This is all overwhelmingly good as compared to yesterday’s condition.

If that fuel type is banned in a country, wouldnt that also disallow planes to fly that country?

I guess leaded fuel can still be used flying between (and within) the "dirty" countries

precisely...

Look at the Philippines - a nation of >7,000 islands. They use Ferry, plane and boat... for all intra-national travel... and they pollute like mad (thanks Reagan Marcos ((I know a lot about the history of the CIA/Reagan/Marcos legacy...)) -- PH is a corrupt government. Or maybe I should just say Government...

If you have coin...

There's only one company legally producing TEL anymore plus few doing so illegally in China. If as GAMI claims all supplies to make G100UL are available in every refinery handling commercial fuels... That's going to be a possible investment goals for everyone across the world just to get rid of Innospec as supplier

Wait, airplanes don't already use unleaded fuel?

Nope. Not piston engines anyway. Airplane engines have to be much more reliable than car engines in a much harsher environment, and until today leaded fuel was the only solution that produced the requisite level of reliability.

That was also the argument for putting lead in fuel for cars in the first place.

The answer just seems "not enough political pressure to phase it out".

Thats true, but aircraft engines also run harder, must be lighter, and more reliable. It has been discussed elsewhere, and is a technically harder problem.

On top of that, general aviation makes up a much smaller part of the population motoring around every day, so probably less of a priority to gain political traction (until now).

That being said, I’m very happy to see an unleaded standard. It was my understanding that 100LL was not able to be transported via pipeline, which was part of the contribution to its higher cost.

Thanks. This was the question I was looking to answer, "if we did it in cars seemingly easily, why not planes!)

Was it easy, though? We already knew it was a bad idea to start with, and yet it took almost a century to phase it out.

It's always been trivially easy to replace lead in car gas if you don't care about cost. There are a thousand chemicals that will increase octane levels and prevent knocking, and some of them can be bought at your local hardware store.

But none of them were as cheap as tetraethyl lead in the early 20th century, so TEL won.

(This argument doesn't apply to avgas, where TEL did/does more than just prevent knocking.)

I know that, and if monetary cost is the only thing you're measuring it's a perfectly good explanation and it's totally worth it to knowingly poison people for that.

It was introduced into auto fuel in 1921 and phased out in autos in the US from 1976 to 1996 (with the phase out being heavily front-loaded).

I would count from the very introduction, because everyone knew from the start it was a bad idea but profits spoke louder.

When do you think TEL was introduced to auto fuel?

What do they run 2-strokes on in the US then?

Oil/gasoline mixture. No requirement that there needs to be lead in the gas, as far as I've ever heard.

Well, I know it's got oil mixed in. Presumably the leaded fuel requirement is only for four-strokes though, since two-strokes can't run on leaded?

It's kind of an orthogonal issue. Oil is needed in the fuel for two-strokers with crankcase ventilation for lubrication. Lead is needed to boost octane. But your old outboard engine is most likely a very simple low compression engine that doesn't need particularly high octane, so can run just fine on regular car gasoline (preferably without ethanol, but again a slightly different issue) mixed with the two-stroke lubricating oil.

I know how they work, I'm just wondering if 2-stroke aero engines get a pass from using leaded fuel since they run for about ten minutes before the lead fouls the plug.

Jets do (as well as turboprops), but piston-engine planes (aka almost all general aviation aircraft) currently burn leaded gasoline.

Jets and turboprops do not use "unleaded fuel", they use jet fuel (which is basically kerosene).

"Unleaded fuel" doesn't mean any fuel without lead, it specifically means gasoline (petrol) without lead. Hydrogen gas (or liquid) can be used as a fuel, but no one would call it "unleaded fuel".

Reminds me of the xkcd comic--

https://xkcd.com/641/

Yeah, that one is exactly like all the "gluten free!" stuff being marketed, which never had gluten in the first place.

Yeah, my reaction to this isn't "oh hey about time" but more "WHAT THE ACTUAL FUCK HOW IS THIS STILL A THING"

https://www.faa.gov/newsroom/leaded-aviation-fuel-and-enviro...

How will California cities justify closing general aviation airports now?

Sadly not just CA. Another favorite lie is "safety." Despite the fact that the road going past any given airport has suffered more fatalities in a few years than the airport has seen in its history, land-speculating trash love to trot out the "safety" excuse.

Take the current poster child for corrupt destruction of our airports: Santa Monica. Not one neighbor of that airport has been killed by an aircraft IN A CENTURY. But the street going past it kills a person per year.

And rich, white people who want to goose their property values come out not only to regurgitate discredited FUD, but to complain that the airport is used by rich, white people. Meanwhile they're just fine with a golf course operating next to it during a permanent drought and a "housing crisis."

BTW, Ann Heche crashed her car and burned down a house not far from Santa Monica... where are the calls to shut down that street?

noise.

"the airplanes landing at this airport that was here when I moved are very loud and should not be allowed to land here anymore."

They could also argue that the airplanes will cast a shadow on neighboring parks/houses.

This is a standard in my country but with farm smells and noises. People buy a house "in the country", then they complain about manure on fields, cows mooing and tractor noises.

Considering that FAA lowered a bunch of flight paths over the last ~5 years, kinda feels like a bait and switch. My parents' place was always pretty quiet since it's 20+ miles from the nearest major airport, but after FAA Nextgen was implemented it got fairly noisy from all the airliners passing over.

I'm curious, where did this happen?

KONT, here's a video of the NIMBY (NOMBY?) complaints: https://youtu.be/MenUDN35uCM

ok, nothing was lowered, but nextgen and the reliance on satellite based navigation is allowing the planes to take more direct routes. this necessarily takes them over areas where they didn't fly before.

i'm sympathetic to the homeowners, but the routes are more efficient and planes burn less fuel. and if the difference is really only a few miles as the guy said in the video, we're talking about ~15 seconds of inconvenience per plane (planes look like they're flying over the lakes ~300 kts), and from checking adsexchange/flightradar, we're not talking about a huge number of planes.

Easy: "We need that land for more strip malls, box stores, and overpriced condos."

Noise

Fun fact: many major US cities still have lead pipes[1]. It costs about $20,000 to replace a lead service line from the water main to your home if you live in an older home/building, and the cities are not exactly working hard to replace lead mains.

The cheapest way to lower your risk of lead exposure is to install an RO filter if you believe there are lead pipes (there are many different brands, but the one from APEC is popular and affordable). It has the added benefit of reducing exposure to other nasty things which have pretty much contaminated all the drinking water on earth like PFAS.

I have an unsubstantiated pet theory on correlation between lead poisoning and crime in poorer neighbourhoods due to landlords refusing to replace these (why bother if you don't have to drink the water? landlords have no incentive so long as they can extract rents).

In many cities you can get your water tested for free by the city, just do some searching. They've usually got an online form you can fill out and they'll send you a kit that you have to send back.

[1]: https://www.nrdc.org/resources/lead-pipes-are-widespread-and...

> The cheapest way to lower your risk of lead exposure is to install an RO filter

That’s much more expensive than the average NSF-listed filter. I believe most of them work by ion exchange, and they are a lot simpler and cheaper than RO.

Get RO if you have serious hardness issues or taste issues that are not mitigated by a good NSF-listed filter with a carbon stage.

https://www.nsf.org/news/concerned-about-lead-drinking-water...

> if you believe there are lead pipes

Just test your water. Even without lead pipes, lead solder on copper pipes can be a problem. Or lead in city pipes. Or anything made out of non-“lead free” brass or bronze. (Some of the latter has a shockingly high proportion of lead in the alloy.)

At least you can prevent leeching from lead pipes. Can't really stop the lead from getting out of an engine.

Lead pipe risk is dramatically overstated. It’s the new asbestos, lots of noise and bullshit and little reality.

What happened in Flint, MI was criminal negligence - literally. That system was operated safely for decades and started poisoning people because of political conditions in the state and incompetence/dereliction.

I agree. It should be phased out, but there is no reason to do it until you have to work on those pipes and disturb them. They are safe while they are calcified and are sending water that is suitable for metal pipes in the first place. Flint was sending basically acid down their pipes because of intervening incompetent and corrupt state officials. It made stainless steel sinks start rusting for gods sake. Even if the system was pure iron pipe that shit would have opened up like swiss cheese into the dirt and ground. Im not even sure if plastic water pipe would have been totally immune to such shitty and prolonged pH levels.

Do you really trust the people running local governments to not mess things up? I certainly don't. I wouldn't trust them to look after my house plants.

The engineer in charge is usually competent and has the prospect of losing his PE at stake.

It's a shame that it took some districts fully banning leaded fuel to force this change through.

The wheels of American bureaucracy don't move without some serious outside forces!

I don't think the wheels of any bureaucracy turn quickly.

There are two fallacies in bureaucracy:

1) With enough organisation, we can please all parties 2) Process can solve all of our problems

My experience (and I suspect others) is an enormous budget of people paid to have meetings, not making much headway, if any, but not being held accountable for outcomes. Imagine a Department having paid a team of people for 30 years to make this happen!

> 2) Process can solve all of our problems

I'm gonna have to stop you right there, if only because process gets a bad rap from people who have never tried to implement systems in which more than a handful of parallel agents can safely work without stomping on or interfering with one another.

Process is critical to coordination. You cannot "thread-safe" without the right process primitives. While I'm using the computing term, I'm using them in a non-computing/abstract system way. Information doesn't magically communicate to the parties who need it. Process gives you the blueprint to quickly create an environment whereby people can do their thing, but information still propagates to those who need it.

If people follow it.

>FAA approves unleaded fuel for piston fleet

Yay! Primary flight training costs will come down 20-30%!

>While the cost of the fuel has not been determined, Braly said the small-batch production process that will initially earmark the arrival of G100UL at airports means that the fuel will cost slightly more than leaded avgas. “Small volume batches cost money,” he said. “Until we can get [production] revved up that we’re making millions of gallons at a time, there will be an incremental [additional] cost,” he said.

Oh.

Give it time.

Previous: https://news.ycombinator.com/item?id=30943466

Original headline seemed far less communicative (and was far too long to use in the submission), so I did the best I could to faithfully summarize.

For the record, the original headline/subheadline is:

  GA moves closer to unleaded future
  FAA approves GAMI unleaded avgas STCs covering piston fleet

So when are we seeing the sunset date of leaded fuel? The government should step in and set it to help the industry move along

It will stay around as long as it's free to poison the environment with lead.

Thank god, this is decades overdue. Seeing the white powder left on my fingers after I spilled some gas while sumping (to check for impurities, before every flight) always made me cringe. If the fuel is impure, standard procedure is to keep draining the impurities (water usually) out and just throw it on the ground.

Huh. I had no idea leaded fuel was still a thing in aviation.

For cars, the argument was, if you used unleaded fuel and (as it might because the engine was designed for leaded gasoline) this causes engine damage, your engine is broken, which is sad, but you can just repair it. The failures are annoying, but they're unlikely to get anybody killed. You can just walk from the broken-down vehicle to somewhere with food and shelter and call a rescue truck.

Even in countries like the UK which offered limited exemptions for "classic" cars, the fuel companies don't care, selling a few thousand litres per year of this weird special fuel makes no sense at their scale, so even with a regulation allowing this, it quickly died out. It was (maybe even still is?) legal to buy leaded gasoline ("petrol") in the UK for a really old car, but that's useless because nobody will sell it to you, it's just not profitable at the incredibly low volumes. Classic owners who run with leaded fuel these days buy their own additives and mix it at home, but also these cars are getting fragile, they probably belong in a museum anyway, not clocking up miles driving around, and in a museum display they don't need fuel.

However if an aircraft engine dies, even though pilots of single engine piston aircraft are trained to assume that will happen in any phase of flight (because it can) that's extremely dangerous, complete engine failure over mountainous terrain could mean that your best case scenario becomes trying to land your plane (well, now glider) in some untried clearing and if you survive then maybe needing to walk out because in some cases nobody is looking for you. So engine failures translate into fatalities at a significant rate.

Planes are very expensive, and so they have long lives, which means many aeroplanes built long before leaded fuel was prohibited are still flying.

On the other hand, notice this is about piston planes. So, you're mostly talking about smaller planes for personal use, and maybe some agricultural or business purposes but less often. For scheduled aviation, you're never going to be on a piston plane. To a layman it's less obvious because although they don't have piston engines lots of smaller or shorter range planes have propellers like an old-timey plane. But their propeller is driven by a jet engine, and that runs on JetA - kerosene fuel not leaded gasoline: https://en.wikipedia.org/wiki/Turboprop

What you said is overwhelmingly true, but there are some scheduled flights in piston twin C402s and the like (Cape Air being one of the larger operators of piston scheduled airline flights).

https://www.capeair.com/

Thanks! I was not aware that existed. It's surprising to me how affordable their ticket prices are, and how many places they're operating. I think I'd imagined anywhere you couldn't justify coming in and out once per day with a Twin Otter there'd be nothing scheduled at all.

I want to fly in to Rutland VT (RUT) again sometime just to have the experience again. I got to fly in a personal aircraft once or twice as a kid, but my couple Cape Air flight still stand out as awesome experiences. And crazy crazy crazy convenient for some of my travels.

It’s subsidized by the federal government… a really cool program.

Seems like every discussion about anything slightly environmental had some lead related low effort comments about "it's 202x, why is leaded avgas still a thing?".

I won't miss those.

I won't miss the lead either.

I'm sure the 'problem X only exists because America doesn't have walkable cities' crowd will take up the slack.

Jet fuel is unleaded. It’s also pretty close to diesel, and some aircraft manufacturers have diesel piston engines that can use JetA. The leaded culprit is AVGas aka 100LL which we use in piston general aviation aircraft.

It lets you run comparatively higher manifold pressures than an otherwise identical but unleaded fuel.

Only because the engines themselves haven't evolved to handle higher manifold pressures. Lots of advancements in internal combustion engines, like combustion chamber and piston shapes that help manage the flame front, direct injection, wideband O2 sensors, are entirely unknown in certificated aircraft and still on the periphery even in experimental aviation.

Like, Mazda is running 14:1 compression ratios in gasoline engines, but 7:1 is considered normal for a naturally aspirated Lycoming and it'll often dip into the 6's for turbocharged versions.

Mazda sold 332,756 vehicles in 2021.

Cessna has the best selling model of airplane of all time, the 172, which has sold around 45K units since its introduction in 1956.

Mazda sells that many cars in a typical 2 month period. It’s no surprise that there’s more non-recurring engineering investment in car engines than airplane engines.

I mean, okay? I get that. But it's not like the Cessna 172 is a $25k item either, it's now over $400k.

There have been tons of advances in general aviation, look at panel technology between now and 15 years ago. That's awesome! Let's do the same thing but for engines now. But it isn't going to happen as long as no one is pushing for it; we have the efficiency in automobiles we do now because regulators have been pushing for better fuel consumption and lower emissions for decades. It'd be great if there was similar pressure applied to aviation.

I'd love to have a 172 that had no mixture knob and no issues with hot starts. Man, wouldn't that be awesome? This is what we should be asking for, not apologizing for why we're stuck with mechanical FI, carb heat, and shock cooling worries.

And Cessna sold 166 of them last year, a figure that Mazda probably refers to as "Saturday morning".

So, because Cessna isn't moving many aircraft we shouldn't ask / hope / demand / lobby / regulate for technology improvements in aircraft engines?

It's not just engine evolution, but TEL was replaced by non-lead additives, not removed. And the fuel mix impacts values critical for aviation but mostly irrelevant to cars, like fuel vaporisation for given temperature/pressure (this is AFAIK major issue with ethanol added to fuel and source of limits on use of MOGAS in aircraft) as well as impact in performance which are pretty much impossible to notice for a car (except maybe if you have engine with sparkplugs designed for leaded fuel) but matter of life and death in airplane.

They were designed in the 60s and the FAA certification process makes designing a replacement cost prohibitive with current and future sales volumes.

More importantly most aviation engines were designed in the 50-70s and need the lead to keep the valves happy.

Another issue is that replacements for TEL that were fine for cars had issues with high altitudes (and high ambient temperatures)

It's about detonation; I don't think it's about the valves.

The 100 octane is about detonation; the lead is about lubricant for the valves.

Mmmm, not sure about that: https://generalaviationnews.com/2011/10/24/why-lead-reduces-...

It's about the valves.

Plenty of 100+ octane unleaded fuels out there.

Post-WWI aviation engines overwhelmingly have hardened valves (and valve seats) which work fine with unleaded fuel.

And the spark plugs unhappy?

If this prevents spark plug fowling as claimed it will be great and brings back a fond memory. During the Sydney Olympics in 2000 I flew a Piper Warrier over the Hawksbury River north of Sydney and the engine started missing - quite possibly due to this issue. A bit of a nervous prospect as there is basically nowhere to land there. At the time there was a huge air exclusion zone over the Olympic Park and there was excited talk of how quickly jets would be dispatched to shoot you down if you violated the airspace. Anyway, the moment we reported engine trouble we were given clearance to head straight back to Bankstown - pretty much right over the top of the games. Good times!

Only 30 years!

I trained in a Cessna 152 that was certificated to run on high-octane unleaded auto gas. No modifications, the EAA just demonstrated that it would run fine like that.

But my 172 had to use Aviation gasoline. Until now.

How do they replace the lubricating function of the triethyl lead?

I hope not by burning PFAS (lol)

You jest but a fluorinated hydrocarbon is probably particularly well suited for the task

I think they worked around the detonation problem by using massive concentrations of MTBE, methanol, and an organic manganese aromatic compound to keep corrosion at bay

No need for speculation when the patent is public: https://patents.google.com/patent/US8628594B1/en

The primary octane booster is Xylene and other similar aromatics, largely already in use in racing fuel. No MTBE.

MTBE...something else absolutely horrible for you when the leaking underground storage tank (LUST) contaminates the water table.

Eh... the Methylcyclopentadienyl Manganese Tricarbonyl (MMT) seems worse to me. Instead of burning lead they're now going to burn organic bound manganese and manganese causes some god awful diseases.

I'm not so sure they're trying to compensate for any lubricating features of lead.

See my other message for what's really going to be in this fuel. They are using hydrocarbon enhancements that have already been a smaller natural component of unleaded gasoline since forever.

MMT could only have ever been a consideration after toxic lead was well accepted, and then it was too late to become mainstream.

MTBE is Methyl tert-Butyl Ether, which is a form of ether that does not evaporate as fast as the traditional Diethyl Ether which people might be more familiar with as a medical product.

The diethyl ether is almost like a gas, not nearly as much as butane but it's getting there.

In the laboratory the diethyl ether commonly comes in a metal can to protect from overpressure if it gets too warm. The MTBE can be stored in an ordinary bottle like alcohol.

But whew do people remark about about the sharp ether odor when you open a bottle of MTBE.

When MTBE was in lots of gasolines, and the underground tanks had been leaking down into aquifers further underground, that smell in peoples' water turned out to be the canary in the coal mine which indicated that other more toxic gasoline components were bound to be there too.

MTBE was shamed then lost more popularity than the gasoline itself after that, in an exaggerated way with political implications leading to ethanol. I don't think everybody would want the general public to be able to smell leaking tanks in the future as well as they could when this issue first came up anyway.

However there have been some experimental medical treatments which involved directly injecting patients locally with truly strong concentrations of MTBE as a natural liquid. Unlike the diethyl ether as an anesthetic which was basically breathed in as a gas.

So this is a 100octane fuel? Can it be sold through regular retail chains?

Since avgas is such a small market I’m thinking that might raise its TAM as a “premium plus” sort of product.

What was the innovation? A new different chemical additive to take the place of lead? Does it require any hardware changes to work right? (spark plugs, etc)

The whole point is that it had to be a drop-in replacement.

What makes lead such a magic substance that makes it used in many places and hard to replace?

I know leaded solder wires have lower melting temp. What else?

Cheap, abundant, easy to acquire, easy to transport, inert, mostly harmless if left alone, maintains its properties in harsh conditions over extended periods of times, mixes well with some other chemicals.

Very harmful if ingested or absorbed, directly or indirectly.

> The FAA signed on September 1 supplemental type certificates that allow ....

As a non-native English reader, why is this not written as:

> The FAA signed supplemental type certificates on September 1 that allow ....

The current sentence feels disjointed and doesn't '_flow_' like natural sentences normally do in English.

Newspaper title text written stupidly for shorter headlines.

This is so that the following relative clause is closer to the noun phrase it modifies.

I sure hope they ban the leaded fuel soon

Does anyone have a link to the STC? FAA stc search didn't return anything new for GAMI.

I am shocked to read this. Why are they still using leaded fuel? There are so many well known research that links lead in fuel to unstable mental health and crime in population.

Because they needed to be completely sure that they had a replacement fuel that wouldn't start making planes fall out of the sky.

That's the excuse. Basically the real reason is that they only care about safety of the planes, not of the people handling the fuel (e.g. pilots, ground staff), or breathing the toxic fumes (everybody on or near an airport). So, they only care about safety when it is a very narrowly scoped notion of that concept.

Bureaucracies are weird like that. This is fundamentally not about people's safety but about covering their own safety (i.e. ass coverage). The problem is not something bad might happen but that they'd be held accountable for it.

Never mind that something bad has been known to happen for the last half century or so that they are not being held accountable for. People actually get sick and die because of leaded fuel but it's not their problem. And never mind that the bad thing that might happen is basically some ancient engines not running that well with unleaded fuel. That's why certification processes exist for engines. You can test this and decide to not certify certain engines for unleaded fuel. Ensuring people fly around with certified engines definitely is their problem. Any modern engine is basically certified for unleaded fuel already.

I mean, planes falling out of the sky is a fairly significant safety issue. "Safety of the plane" is misleading if there's people inside the planes lol.

Some piston engines are really high compression and it's hard to prevent knocking without leaded fuel.

And to be clear, "knocking" means engine detonation, which very quickly leads to catastrophic engine failure. Which is something that you don't want while in flight.

Until now, the only alternative was to fly a turbine-powered aircraft that can run on Jet-A. The problem with those is that turbines are far too expensive, and terribly inefficient at low altitude - both of which have kept them out of reach for most of general aviation.

Admittedly Turboprops can be somewhat more efficent at lower altitudes than turbojet and turbofan engines. But still not terribly efficient at say sightseeing or cropdusting altitudes, and they are still a lot more expensive than avgas engines (and that is not even accounting for the fact that the aircraft designed to use them are bigger and more expensive than many avgas based prop planes).

Is the full composition of this fuel public knowledge?

Or is there some secret ingredient that acts as a lead replacement?

Some PTFE precursors would be a really unfortunate choice for example...

It's not actually a secret.

The abundant, affordable low-octane base fuel stocks that refiners and blenders work to bring up to specs have always been a no-brainer - just add a few grams of lead to your tank, and wow you've got high-octane rated fuel. And lead is heavy so that's only like a small number of mL.

Very few oil wells naturally yield a very high octane gasoline fraction, so for adequate engine performance, some enhancement has always been necessary.

The "pipeline" ended up being built basically around gasoline and additive, where the additive amount directly and straightforwardly controls the octane.

Alcohols were always known to bring up the octane rating too but you need to add gallons of alcohols to your tank not just grams. However the energy density is lower with alcohol so you get fewer miles per gallon, not what you want in an aircraft.

Well this is more like blending two bulk fuels so that was one of the infrastructure adjustments that needed to be made as the lead additive approach was phased out.

Now major percentages of alcohol are blended with base stocks to achieve the target "clean-air" and octane-rating requirements, so this has been well in place for decades.

For the G100UL they do not use alcohol, instead they blend in many gallons of other flammable liquids like xylene, which is a hydrocarbon itself, just happens to increase the octane, and increases the energy density as well. Xylene is traditionally handled as a solvent and paint thinner, so they can get trailerloads (but not nearly as cheaply as alcohol is in automotive gasoline). Xylene has always been one of those dangerous flammable hydrocarbon cargoes, supplied as a petro-chemical by a lot of refineries, it's just one of the chemicals that is normally considered too expensive to burn.

So they're not replacing a few grams of lead with a few grams of something else, GAMI has replaced a few grams of lead with a few gallons of something else completely different from lead.

And that "something else" are actually hydrocarbons that have always existed naturally in all kinds of gasoline (only in far less significant percentage). GAMI is scientifically bringing up the percentage of this type of component while maintaining the drop-in characteristic.

What are the chances some airports have signed 20 year fuel supply contracts with some leaded fuel supplier?

I think for this to have much traction, some carrot and stick needs to be applied... A $1/gallon tax on leaded fuel that doubles every year ought to be a good incentive to start using lead free stuff.

I think you’ll see the fuel supplier unable to supply 100LL somewhere between 10 and 20 years as this rolls out.

The critical element is this is miscible fuel. It doesn’t need new tanks, new pumps, airplane mods, or any big-bang adoption. It takes refineries licensing the formulation and individual airplanes to spend around one fillup’s worth of fuel on a piece of paper.

That’s a 5-10 year process, not a 20. Once the volume drops off, the one plant making TEL will plan to shut down I think.

I’d expect to see an EPA Clean Air Act update to ban 100LL in the 10-20 year timeframe as well.

Finally

Didn't expect to see good news today! Talk about making my body fill with happy chemicals!

We live in an age where "less terrible" is sold as "great".

I'd hate to live in a world where no achievement is worthy of celebration unless it passes all your purity tests

You do

It'll keep working until it stops. You'd think that with Wikipedia and all the information at our fingertips people would be able to tell a sheep from a wolf, but instead they're more likely to believe the authoritative talk show host because that person makes the tribal signals they like the best.

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