It isn't just compression ratio. It is also combustion chamber shape and size. Also RPM. Higher RPM = less detonation prone. Smaller combustion chamber = less detonation prone.

But the simple answer is you probably need something a lot like 100LL if you're running anything much above 8.5:1.

Youre either about to have an angry mob or they will just ignore this thread entirely.

This must be part of the big coordinated smear campaign (Maybe that shouldnt be green)

Edit: Sorry for the smarta55 comments. A few real questions that are sure to come up:

How much testing has been completed with different types of rubber seals/bladders/etc?

What effects on common aircraft paints have been observed?

Be careful with that 80% figure. About 80% of the airplanes in the fleet don't need 100LL. But the other 20% requires and uses 80% of the 100LL that's sold.

We don't know yet. That's what is being evaluated by the research arm of PAFI and OEMs. This will also vary with the engine design.

Be careful with that 80% figure. About 80% of the airplanes in the fleet don't need 100LL. But the other 20% requires and uses 80% of the 100LL that's sold.

Youre either about to have an angry mob or they will just ignore this thread entirely.

This must be part of the big coordinated smear campaign (Maybe that shouldnt be green)

Edit: Sorry for the smarta55 comments. A few real questions that are sure to come up:

How much testing has been completed with different types of rubber seals/bladders/etc?

What effects on common aircraft paints have been observed?

It is interesting to see the detailed metrics page at the link you supplied, and particularly the drill-down into the materials testing regimens. However, I'm not seeing anything that shows the results of the tests fully or even partially completed. Can we assume those tests have been completed successfully with no significant negative results?

Also, it would be helpful to know what the timetable is for completing the substantial number of tests still to be performed. Any way of providing at least a ballpark for various testing completions?

And, of course, the biggie: how close to December 31, 2030 will the full rollout of the fuel expected to be?

Yes, Stan. Completion means the test was completed with no significant issues. The timetable is a bit fluid, but I am told testing should be completed by September of next year. Fleet approval expected in 2027. Roll out to the entire fleet will depend on how the FAA chooses to manage the transition and how receptive the marketplace is.

Also, if you don't mind me asking, the IO-540-K1A5 for which testing has been 100% completed has a compression ratio of 8.70:1 which is on the higher end of Lycoming engine compression ratios (those that were even higher at 8.9:1 appear to only come in 4 cylinder varieties: https://www.lycoming.com/sites/default/ ... ngines.pdf). Were there any observable issues with that engine using UL100E?

EDIT: I realize you probably answered this already with your response above. However, this is of particular interest to me because my Lycoming engine has a 8.5:1 compression ratio, which may or may not mean anything in the big picture because mine is turbonormalized and carbureted

Yes, Stan. Completion means the test was completed with no significant issues. The timetable is a bit fluid, but I am told testing should be completed by September of next year. Fleet approval expected in 2027. Roll out to the entire fleet will depend on how the FAA chooses to manage the transition and how receptive the marketplace is.

Thanks for participating. Most Bonanzas and Barons run 8.5-1 NA Continentals. Do you have any info on how your fuel will work with these engines yet?

Yes, Stan. Completion means the test was completed with no significant issues. The timetable is a bit fluid, but I am told testing should be completed by September of next year. Fleet approval expected in 2027. Roll out to the entire fleet will depend on how the FAA chooses to manage the transition and how receptive the marketplace is.

Welcome, Daniel! Nice to see you here...

Did you make it to Brussels ASTM? Any interesting bits?

I had planned to attend, but family issues arose.

Paul

Just a few more seats left and we’ll all be here. ….Matt?

Hi Matt,

What engines/airframes do you expect your fuel to be approved for without modifications?

Can't list them yet, but I am told about 80% of the fleet with no mods or changes in operating envelope.

Which ones with modifications?

Another 10-15 % with minor modifications like timing adjustments and minor changes to operating envelope. The rest with major mods up to and including changes in CR.

Which ones do you not expect approval for?

None.

Are there any weight or performance differences from 100LL?

No weight difference. It has the same density as typical FBO 100LL. Performance-wise, it has lower detonation margin than 100LL. Our fuel is completely miscible with 100LL and has synergistic octane response. The FAA and OEMs routinely test the fuels mixtures to ensure compatibility with each other and performance in the test engines.

We have not evaluated compatibility with G100UL or Swift 100R nor do we plan to. We think it is unlikely either STC'd fuel will find widespread acceptance, especially without an ASTM standard. We also will take steps to ensure that the fuels are not intermixed in the field for liability reasons.

Dan