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Comment by mlyle | Hacker News Reader

> b) At some point you have to just put your foot down. Ban the sale leaded gas using planes after 1/1/2022. Grandfather in the old planes.

A measure like this may be reasonable.

But C/D totals the entire piston aircraft fleet-- $50B+ of capital equip, plus the whole infrastructure and industry around it-- for only a very moderate change in lead exposure. Best estimates I've seen is that this would lower the total population burden from lead by well under 5%.

Much more sane, IMO, to put in a progressively escalating tax on leaded aviation fuels that over time becomes steep. Then airplanes can gradually transition as overhauls become due, etc, as the pressure from operating costs mounts. Presumably those burning the most fuel would transition first, and an industry capable of retrofitting a few percent of the aircraft per year would spring up.

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airplanes can gradually transition

Except they can't, since there is no approved alternative.

The other problem is that even planes that can run unleaded gas often don't, because it's not available at the airport. Avgas is a tiny market and because of costs most FBOs can't or won't set up another fuel delivery infrastructure to run two fuels over some short transition period.

Because of this, an additional requirement on a replacement is also that it be safely mixable with 100LL in any ratio, because during the transition period this will happen as people fly from airports where it exists to airports where it doesn't.

This problem is being solved (https://www.faa.gov/about/initiatives/avgas/).

> Except they can't, since there is no approved alternative.

There's an increasing number of diesel engines for GA aircraft, and supplemental type certificates to retrofit them into the same. If 100LL got more expensive, you'd see more people opting for the diesels when an engine reaches the end of its life.

e.g. http://www.continentaldiesel.com/typo3/fileadmin/_centurion/...

Yes, it'd be really cool to end up with a lower-lead fuel that's safely combined with 100LL. That's been "imminent" for the last 25 years.

The poster above advocates for a "rip off the band-aid" approach. GA advocates for a gradual, painless transition that, in practice, will never happen. Surely there's some middle ground?

Continental diesels still have "TBR" (time between replacements) instead of "TBO" (time between overhauls). That's a huge problem preventing their uptake.

https://www.aviationconsumer.com/aircraftreviews/aircraftste...

Data seems to imply that the diesel engine lifecycle cost is slightly better now than conventional engines, so electing for a diesel replacement instead of a conventional engine overhaul can make sense... but it's a razor thin difference.

If you made leaded fuels more expensive-- more airfields are going to want to move to UL94, and more people at overhaul time are going to go the diesel path, and the problem will gradually get better.

Well, plus the fact that a new aviation engine runs $30-60k, which is about what an old, small, airplane is worth. It just doesn't make economic sense to replace those engines, you're effectively just trashing those planes.

A post further down says that the first unleaded replacement for 100LL was actually just approved.

Swift UL94 has been to market for 3 years with very low uptake.

Fair enough, but that's not a replacement for 100LL since not all engines can use it. It's gotta be a pretty large FBO to have enough market to pay for setting up a distribution for UL94 in addition to 100 octane gas. Like, there are engines that were certificated to run on 80/87 avgas but no one sells that any more either. Today's avgas market just isn't large enough to make it worth offering two fuels.

About 2/3rds of GA has an STC available to burn it.

There's not going to be one single tidy drop-in solution for the entire market. That's why we should tax leaded fuels, and everyone can pick the appropriate solution for them. Some will pick diesel conversions. Some airfields will go 94UL and people will purchase STCs. Presumably some other people will take other paths. And those with the hardest time transitioning can instead pay the tax and burn leaded fuel, still.

Because as far as I know the engines must have their type acceptance updates to reflect it's allowed use.

3 years is also basically a second at the speeds GA changes at.

Yes, technically speaking.

Swift charges $100 for a STC, and has coverage of two thirds of the GA fleet.

Really, all that needs to happen is an airport needs to decide that lead free is important to them and they'll pay the premium for Swift's fuel.

The slow uptake has more to do with it just not being all that available.

Yup-- why should an airfield bother with going to 94UL when it's more of a hassle (some planes can't take it, all planes need an STC).

But if you taxed the crap out of lead-containing fuels, I suspect more would be interested...

> Best estimates I've seen is that this would lower the total population burden from lead by well under 5%.

That sounds pretty great actually, for such a simple solution.

It's not absolutely a sure thing that there's any significant burden from aviation. Blood tests come up with a tiny, barely detectable difference near airports (well under 5% for those nearest the airport, and confounded: airports are correlated with low SES and therefore lead paint, etc, is also more prevalent). The most pessimistic estimates from first principles come up with 2-3% of the total population lead burden (more than an order of magnitude above what the blood tests imply, and the blood tests likely overstate the problem).

If you threw a few billion more at leaded paint remediation, I think you'd make much more of a difference. I think the aviation lead problem should get fixed, but because it's such a small part of the overall problem it makes sense to take a graduated approach instead of giving GA businesses the death penalty. Tax leaded aviation fuels, and use the proceeds to pay for leaded paint remediation.

If the tax was substantial I'd support this.

Graduated approach ignores the decades that have ALREADY been provided as an exception to the lead fuel rules that apply everywhere else - it's already been graduated.

> If the tax was substantial I'd support this.

Start at 10% with a commitment to ratchet it up by 4% per year or something. That's enough to start an immediate reduction without destroying the industry.

If you're making choices about engine overhaul now for an overhaul that will last you 7-8 years of light use, fuel costing 40% more at the end of that overhaul will definitely get your attention.

> it's already been graduated.

Doing nothing for decades when it was impossible; and then doing nothing for a decade or two when transition became possible; and then pushing the industry off the cliff is not graduated.

It's a small problem? I read recently that GA accounted for >50% of environmental lead exposure.

Perhaps that's wrong, but I distinctly remember the statistic and it stuck with me.

Source please. All the studies I've read have barely detected higher levels of lead near airports, and are confounded. All the estimates from first principles estimate that it's a very small proportion of population lead exposure, too.

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