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).
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.
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?".
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.
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.
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.
If Mazda spends $25M in NRE on a new engine program and sells that design for 8 model years, the amortized NRE is around $10 per car or about 3 basis points of the product.
If Lycoming or Continental spend $25M on a new engine program and sell them for 15 years in all 172s, it’s around $22K per airplane or around 550 basis points. When investments in engine development are over 180x more expensive on a percent of sales basis and over 2000x as expensive on a per-unit basis, it’s unsurprising that few companies are stepping up to do that development.
I don’t mind at all if you want to lobby for it; I think there are improvements that could be made, but I think you’ll find the economics daunting and the current engine tech to be pretty well matched to the application.
Regulation is exactly the reason why there are few technology improvements. Improving the engines is pretty trivial. Heck, Diamond adapted car engines for their aircraft.
_Certifying_ them is hilariously expensive for the manufacturers and users.
One can certainly fix that, but that's how it is. Main reason why the planes that consume automotive gas the most are in the 'experimental' category.
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.
