What about something in-between? The fuel is reliable in almost every design, but there's some design out there that -relies- upon lead depositing to engine surfaces to be reliable (as opposed to the octane effect).

I don't think it needs to work in every conceivable 100LL aircraft: just almost all. Every is a high bar.

Which is why it is taking so long. Because if an engine grenades on takeoff, it's almost guaranteed to kill someone. If that was because of the fuel switch, that's a real problem.

You can’t realistically support both leaded and unleaded avgas, and this is why adoption is so low.

Airports don’t always have the space for a second avgas tank (if this is the in between option), and if they did don’t necessarily want to spend money on setting up that infrastructure. So the current catch-all is to provide leaded which is cheaper and guaranteed to work in everything.

I think it’s great we are getting this forced through - it will make the approval process streamlined (like loda was) and removes a major reason people used to push airport shutdowns.

> Airports don’t always have the space for a second avgas tank (if this is the in between option), and if they did don’t necessarily want to spend money on setting up that infrastructure.

Lots of airports are owned or regulated by local governments which might want to move that single tank to just unleaded. E.g. Santa Clara County banned 100LL at local airports.

Forklift upgrades suck, too. You get some of the way along and then forklift. Arguably we're reaching that point.

What's the FAA incentive to change the type certification (and STC) rules here? There's a perfectly workable STC path, that's not even that expensive [almost rounds to $0 in the scope of private aircraft ownership expenses).

The TC says you must run 100LL. The STC says you can freely mix G100UL in any ratio. The legal/certification problem is solved.