Unleaded Avgas

[Mr Grinch]

I wonder how all of these fuels react to Pro Seal...

[BrianDC]

Originally Posted by TXFlyGuy

Thank you for helping to clarify the intent. Yes, the multiple stages, and time required.
How many hours do you have to put on an engine with the new fuel before you certify it safe?

Who ultimately makes that decision...FAA? The manufacturers? Oil companies?

For certified engines, FAA will make the final ruling / certification on what alternate fuel or fuels will replace 100LL. At least at is my understanding.
For the experimental or alternate engines, we as the builder determine what fuel we want to use. If you use a continental or Lycomming then you can follow what the certified world is doing.
If you have a Subaru engine or car engine, you do what you see fit.

Timeline. They say the group will have a recommendation in 2018. Another year for comments? Maybe 2020 for it to be available at airfields?

[Kyle Boatright]

Originally Posted by tspear

No, the industry has not signed off on it.
By number, most engines could run on 91UL. The problem is that the engines which cannot run on 91UL with out detonation and other issues are the most prolific consumers of avgas. Depends on who surveys you use, but the numbers I have seen are between 60-80% of the avgas consumed in the USA is by planes which cannot run on 91UL or any related variety.

<snip>

Tim

I'd love to see the current breakdown of that statistic. I seem to remember AOPA throwing around the 70% of 100ll usage is by working airplanes that require it stat from 15+ years ago. I'd guess that statistic is way off today. Very, very few "working" aircraft today use highly stressed piston engines. Many of those aircraft wore out or were simply retired over that timeframe and during last decade's financial crisis.

It isn't that I'm against leaded fuel, but I am in favor of using good data to support my argument for it.

[Bugsy]

My engine loves swift fuel. I wish we could get it at more airports

[scrollF4]

Bugsy,
Which Swift octane/formula are you burning?

[roadrunner20]

The last time I checked, they offer Swift fuel in Sebring Florida, KSEF, at the same price as 100LL.
No incentive for me to try it.

[az_gila]

Originally Posted by tspear

No, the industry has not signed off on it.
By number, most engines could run on 91UL. The problem is that the engines which cannot run on 91UL with out detonation and other issues are the most prolific consumers of avgas. Depends on who surveys you use, but the numbers I have seen are between 60-80% of the avgas consumed in the USA is by planes which cannot run on 91UL or any related variety.
Basically this is the turbo charged engines and engines with a compression ratio around 8.5 tend to have issues.

As for status, I stopped paying attention. GAMI is still pushing forward with the STC for the G100 solution, I think two others dropped out of the PAFI solution (not sure why). Part of the reason I hope for a diesel/JetA solution.

Tim

Is that 8.5 compression ratio a misquote?

It is the common O-360 compression ratio.

[airguy]

Either a misquote or a repeat of misinformation, I'm guessing. I'm running 8.7:1 compression on my IO360 running standard premium 91E10 autofuel with no issues, about 140 hours so far in the last calendar year. My engine loves it.

[simpkinsona]

Originally Posted by Mr Grinch

I wonder how all of these fuels react to Pro Seal...

I wondered that as well. I did some research on it because I use auto fuel with ethanol and was concerned. It turns out that the common Pro Seal used on RVs is very resistant to the common chemicals in fuels and also alcohol. I'm keeping my fingers crossed, but so far so good over the last 10 years. Don't know if Swift fuel will be different, but I would suspect it will have no adverse effects.

-Andy

[Ed_Wischmeyer]

Hate to say it, but the handwriting has been on the wall for quite some time about the future of avgas. And just keeping avgas available at all has involved a lot of work behind the scenes by a lot of people.

Those who have chosen to modify their engines for extra high compression may have to make changes if they want to burn commercially available fuel.

I don't have definitive numbers, but extra compression ratio doesn't get you all that much more power, and since speed goes as the cube root of power... 9% more power is 3% more speed.

Sorry, but widespread demand for avgas for high compression engines just ain't there.

Ed