Fuel options

Salty said:
Fuel is not IP nor an aviation mod.

They can (and I’m sure will) make money licensing the formula (now that is IP) to fuel producers. An stc for this is moronic.
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What part of the fact that this fuel was approved through the STC process, therefore an STC is required don't you understand?

There are three ways to get the fuel approved. Meet the ASTM standard for aviation fuel. Change the ASTM standard to cover the new fuel. Get it approved through use via STC.
 
mandm said:
So fuel injected aircraft are not capable of MOGAS (which is basically same fuel at the gas station for cars?), but potentially a newer fuel UL94 which seems to be popping up more and more? So lead is not required? But it can or cannot be used in the system?
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There used to be a 91/96 fuel in between 80/87 and 100/130 (changed to 100LL). So those engines, some of which were injected could be run on 94UL.

FYI, 94UL is 100LL with no lead.

Since 91/96 has been gone since the 60s, most POH/documents don't even list it.

Turbocharged engines, AFAIK, all require 100/130 or 100LL.
 
mondtster said:
That is not absolutely true. There are a few injected engines which are approved on the auto fuel STCs. The injection system design is part of the contributing factor as to why it may or may not have gotten approved.

Lead was added to the fuel to prevent knock. There are some other benefits that manufacturers enjoyed from the use of leaded fuel but most of the engines you will find in service today will run fine on unleaded as long as the octane requirements are met. The new aviation fuels will either need to meet current fuel requirements or if they can’t, an STC for their use will be required. Just like the aforementioned oil that required an STC to use since it didn’t meet (and I think it still wouldn’t) SAE J1899.

FWIW, Lycoming has approved many of their engines to run on some of the currently available unleaded fuels. Continental may have done the same but I don’t know that for sure. Even with the engine manufacturers approval it still isn’t acceptable to run the various fuels in your aircraft without some sort of airframe approval.
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I thought tetra ethyl lead was added as an octane booster. I best understood Swifts UL 94 as 100LL without the lead. Some engines don't need the added octane of lead. High compression engines do.

My engine will run fat dumb and happy on ethanol free 91 octane Mogas. But for whatever reason, it's been found that my airframe requires an added boost pump. So 2 STCs are needed. One for the engine and one for the airframe. And I believe GAMI has said this will be true for them
 
Pinecone said:
What part of the fact that this fuel was approved through the STC process, therefore an STC is required don't you understand?

There are three ways to get the fuel approved. Meet the ASTM standard for aviation fuel. Change the ASTM standard to cover the new fuel. Get it approved through use via STC.
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What part of “that’s stupid” don’t you understand. Just because it’s so, doesn’t mean it’s not stupid.
 
mandm said:
So fuel injected aircraft are not capable of MOGAS (which is basically same fuel at the gas station for cars?), but potentially a newer fuel UL94 which seems to be popping up more and more? So lead is not required? But it can or cannot be used in the system?
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Capable and eligible are different things in this instance. It's all in what octane your airplane/engine was certificated for. Mogas is pump gas... without ethanol. Pump gas is premium is 91 octane. UL 94's higher octane means more are eligible to run on it.

With UL 94 being 100ll without lead you don't have the problem GAMI rant into with octane degradation when mixing. You'd end up with something in between 94 and 100.

Swift is from Indiana, so we see UL94 more by us. But it's still a fraction of overall market and it's oftentimes more expensive than 100LL. East Troy is our closest one that carries it I believe and it's currently 6.50 and 100LL is 5.50 a gallon.

I actually didn't know an stc was also required to run the swift fuel
 
Racerx said:
I thought tetra ethyl lead was added as an octane booster.
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I never said it wasn't. Reread what I wrote. ;)

Racerx said:
My engine will run fat dumb and happy on ethanol free 91 octane Mogas. But for whatever reason, it's been found that my airframe requires an added boost pump. So 2 STCs are needed. One for the engine and one for the airframe. And I believe GAMI has said this will be true for them
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That is not why two STCs are required. You are altering two articles, the engine and the airframe. Even aircraft that can run auto fuel with just a paperwork shuffle have two components to the approval.

Racerx said:
Capable and eligible are different things in this instance. It's all in what octane your airplane/engine was certificated for.
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There is more to it than that. As I wrote up the thread a bit, there were some injected engines that were approved for auto fuel. The ones that were approved all have a fuel injection system that incorporates a fuel vapor return line going back to the fuel tank. It is my understanding that vapor lock issues stymied the use of auto fuel in the common Bendix systems that did not have a return line.
 
Salty said:
What part of “that’s stupid” don’t you understand. Just because it’s so, doesn’t mean it’s not stupid.
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So yuo think GAMI took the wrong way? Because the fuel does not meet the ASTM standard, they would have had to change the standard.

Don't you think they figured that would have even been a harder hill to climb?

If you are SO smart, why don't you have an approved UL aviation fuel??????????
 
Pinecone said:
So yuo think GAMI took the wrong way? Because the fuel does not meet the ASTM standard, they would have had to change the standard.

Don't you think they figured that would have even been a harder hill to climb?

If you are SO smart, why don't you have an approved UL aviation fuel??????????
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Not my job man.
 
So you complain how they did it, but won't do it yourself, or even research the hoops to jump through. Nice.
 
Salty said:
What part of “that’s stupid” don’t you understand. Just because it’s so, doesn’t mean it’s not stupid.
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GAMI is god and the government is always right. :D
From voicing my opinion on this topic on BT and here this is what I have found to be the prevailing opinion.
 
Bell206 said:
Afriad so. The fuel and oil are part of the aircraft/engine certification process. G100L is a major alteration to that certification and requires the necessary documentation just like any other modification.

You do understand G100L was developed and approved by private individuals at their own substantial expense. So you don't think they should charge for G100L and recoup their investment plus ROI?

FYI: when the 1st Phillips multi-weight oil was released it did require an STC to use. ;)
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Compare the STC requirement for G100L to requiring an STC for changing from cloth to leather interior. Neither has any effect on the safe operation of the aircraft.
 
Clip4 said:
Neither has any effect on the safe operation of the aircraft.
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And? While safe operation is part of it, an STC is simply one method of a design approval regardless of modification. They also issue STCs for modifications that are minor alterations and even for items that have no applicable airworthiness standards.
 
Clip4 said:
Compare the STC requirement for G100L to requiring an STC for changing from cloth to leather interior. Neither has any effect on the safe operation of the aircraft.
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Maybe so, but the law stipulates that any departure from the Type Design is a modification. There are definitions for Minor Mods (little or no approval required) and Major Mods (STC required). The system is set up that way because people died when they changed stuff on the airplane.
 
Clip4 said:
Compare the STC requirement for G100L to requiring an STC for changing from cloth to leather interior. Neither has any effect on the safe operation of the aircraft.
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Discuss that with the FAA. Not GAMI.
 
Good summary of where we stand with G100UL:

https://www.axios.com/2022/11/15/small-airplanes-unleaded-fuel

I hope this turns out to be true:

"Pilots are being told to expect G100UL to start appearing for sale in the coming months, if all goes well with manufacturing and distribution."​

I find myself wondering if there is going to be a backlog of orders for the STC.
 
Thanks for bumping this, I missed it the first round. And of course, I just made the same argument elsewhere and it's already been well hashed. :oops:

(+1 to the STC situation is stupid, I don't care who's fault it is. Applying a sticker to a wing and placing yet another piece of paper in the ever-heavier logbook box is not a "major alteration" to my plane)
 
Talk to your congress critters about changing the laws to cause a change in the regulations.

GAMI had to work within the options available.
 
And the one issue against mogas....

I can run mogas in my experimental aircraft (O-235) and did so for some time. My problem was that leaking mogas leaves no trace. Leaking 100LL leaves a very clear indicator whereever it leaks.

After a while I decided that being made aware of fuel leaks was a higher priority than the benefits of mogas. If I had easy access to it I would probably run it occasionally, but i don't.
 
You could dye the mogas yourself.
 
And the problem stems from the lack of ability to create an unleaded fuel to meet the ASTM requirements of aircraft fuel. because in order to meet that requirement, it must contain lead.
That said, all my aircraft have a requirement for 80/87 octane. With the car gas STC I can run regular unleaded at 83 octane with no problem except the alcohol content which is verboten.
The reason for using lead as an antiknock compound is that at the time (19teens or 1920's?) it was cheap, and did the job. There are other additives out there to do the same job, but our 1930's technology aircraft are governed by a bureaucracy, which is why change is very expensive and slow, if at all.
 
bluerooster said:
And the problem stems from the lack of ability to create an unleaded fuel to meet the ASTM requirements of aircraft fuel. because in order to meet that requirement, it must contain lead.
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No, it doesn't. It does set a maximum amount of lead, but not a minimum. So 0 lead is OK.
 
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