I don't hate general aviation at all. But I do hate the segment of the AOPA who are basically an offshoot of the NRA, the 100LL-from-our-cold-dead-hands faction. It sounds like you are an aviator so you must be familiar with the people I am talking about.

It's true that if you average the consumption of avgas over the service of the planet you get a pretty small number, but that's no consolation to the family at the end of the airfield who actually gets all of that stuff deposited in their back yard.

I think you're probably a troll, but I'll bite anyway:

I've been active in general aviation for years, and I've never met one these pro-lead strawmen you write about. Since you seem to have all the answers, can you put forward a rational solution to the problem (that isn't "Just throw away all the airplanes")?

How was it handled with cars? At some point, leaded gasoline became unavailable for cars. And yet, cars from before are still around, apparently limited by maintenance and accidents rather than fuel. How was that handled?

New cars were mandated to use unleaded fuel. As demand for leaded fuel dropped off, it became uneconomical for fuel retailers to keep a separate tank and pump for leaded fuel. There may have been (probably was) a hard cut-off date for sale of leaded motor vehicle fuel as well.

The older cars that were originally designed for leaded fuel were either retrofitted with hardened valve seats that didn't require the lubrication of lead, were simply run on unleaded to their deaths, or in some cases (Mercedes-Benz comes to mind, though there may have been others) never needed lead to begin with.

There was one more solution employed in various places: aftermarket additives. These could be actual leaded additives, or more likely some substitute which would somewhat reduce wear on valve seats. These additives were not commonly used in cars in the US, but were/are commonly used in other countries where leaded gas disappeared faster than old cars, as well as in the US itself in farm and garden tractors, whose engines often last multiple decades.

Perhaps we could do the same for small planes, but clearly it would take a lot of research and testing to make sure it's safe. If someone is willing to pay for that testing, it's probably doable.

If the engines can be retrofitted to work on unleaded gas, that seems like the obvious way forward for the general aviation fleet, then.

I'm sure it won't be cheap. And this isn't just an abstract cost to me; although it won't hit me nearly as hard as some, I do belong to a flying club which owns two airplanes that would need the work. On the other hand, owning an airplane is painfully expensive anyway. Perhaps I'm off base, but it sounds like the unleaded retrofit wouldn't be too painfully expensive when, say, combined with a 2000-hour overhaul.

I'm sure there will be a number of aircraft owners who couldn't afford it and would have to sell their plane at a discount once the fuel cut over. I'd feel bad for them. On the other hand, they (we) are running pretty dirty machines that emit some nasty pollution, and it shouldn't be a big surprise that they (we) can't get away with that forever.

On one hand, the small size of the GA fleet means that this is a tiny problem compared to leaded gas use in cars. On the other hand, the general reduction in pollution in the US means that it's substantial relative to what's left. Leaded fuel used by GA accounts for almost half of all lead emissions in the country now, and that seems worth fixing.

As a GA pilot, I cringe everytime I gas up and spill a little on myself or on the ground. That lead can't get out fast enough!

But it is also incorrect to draw a parallel to cars, because there was enough volume for cars to transition gently to unleaded gas; you could get both for a while. There is not enough volume of 100LL for FBOs to have two tanks, so, the switchover will have to be all at once. That's why the "drop-in replacement fuel" search is going on... Don't know if it will come to fruition, but if it does, sure makes the problem a lot easier.

Today, though, it's frustrating to have an airplane that I know could run fine on ethanol-free, lead-free 92 octane motor gas, but am required by law (unless I buy an STC) and by practicality (what airports sell) to use leaded fuel.

The transition period would be painful. Seems like the way to go would be to mandate the end of 100LL, but make it perhaps five years in advance, or more. Could mandate that unleaded conversions be done for continued airworthiness sometime in advance of that date if that would help things along.

I guess I'm assuming that an engine that's been converted for unleaded will still work on 100LL. Obviously that's the case for yours, but I suppose it may not be the case for all. If so, that would complicate things severely.

The problem is that many engines can't be retrofitted to work on (premium autogas) unleaded gasoline.

Most normally aspirated engines will work fine (in some cases, better) on a high grade unleaded auto gas.

Most turbo-charged engines lack sufficient detonation margin when run with that "premium" auto fuel, and need some form of octane boost to provide adequate detonation margins for a high-temp, max performance takeoff run. Several groups, including Swift, GAMI, and Shell, are working on drop-in zero-lead replacements for 100LL. All are flying the fuel in experimental applications as I understand it. None appear "close" to certification.

The real problem is that the bulk of gallons burned are burned by airplanes that are turbo-charged. So, even if 75% of the engines can be readily converted (in many cases, a paperwork-only STC), those 75% of airplanes likely represent fewer than 25% of the gallons burned.

I've been to GAMI in Ada, OK and seen them run their no-lead fuel in a lab setup. It's impressive and looks like it would work. They still face a steep and long uphill battle with the FAA, as do Swift, Shell and the others...

45 years isn't long enough?