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Unleaded Avgas

T

TXFlyGuy

Well Known Member
So...where do we stand on having a reliable source of high octane (93 rating or more), available for us GA types out flying our high performance RV's?

I just read that we are now in Phase II of testing. How many phases will there be? 3, 4, more?

What is the holdup, and what parameters are being looked at? Can engines that are currently burning 100LL not be safely run on lead and alcohol free 93 octane?

Here is the answer. So why is it not available right now? The industry has signed off on this, and the UL105 fuel as well.

https://swiftfuels.com/fuel/unleaded-ul94-avgas/
 
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TXFlyGuy said:
So...where do we stand on having a reliable source of high octane (93 rating or more), available for us GA types out flying our high performance RV's?

I just read that we are now in Phase II of testing. How many phases will there be? 3, 4, more?

What is the holdup, and what parameters are being looked at? Can engines that are currently burning 100LL not be safely run on lead and alcohol free 93 octane?

Here is the answer. So why is it not available right now? The industry has signed off on this, and the UL105 fuel as well.

https://swiftfuels.com/fuel/unleaded-ul94-avgas/
Click to expand...

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
 
Well, how about UL102? It appears that most of the OEM types have signed off on the UL94, with the UL102 in the works. But...the FAA is involved. And this is adding years to the approval.

Like when pilots were burning auto fuel in their Lycomings, because the engine ran better as it was designed for 80 Octane. Many did this well before the EAA got an STC for the use of auto gas.

https://swiftfuels.com/fuel/unleaded-ul102-avgas/

Only Unleaded 100+ Octane Avgas Approved by ASTM International (D7719)

UL102 is the first and only unleaded high-octane avgas to have an ASTM Production Specification approved for avgas - ASTM D7719, Standard Specification for High Aromatic Content Unleaded Hydrocarbon Aviation Gasoline. This approval was earned through cross-industry evaluation by a 100+ member ASTM subcommittee, including representatives from industry advocacy groups, regulatory agencies, engine/airframe OEM's, fuel producers, testing laboratories, and more.
 
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TXFlyGuy said:
Well, how about UL102? It appears that most of the OEM types have signed off on the UL94, with the UL102 in the works. But...the FAA is involved. And this is adding years to the approval.

Like when pilots were burning auto fuel in their Lycomings, because the engine ran better as it was designed for 80 Octane. Many did this well before the EAA got an STC for the use of auto gas.

https://swiftfuels.com/fuel/unleaded-ul102-avgas/

Only Unleaded 100+ Octane Avgas Approved by ASTM International (D7719)

UL102 is the first and only unleaded high-octane avgas to have an ASTM Production Specification approved for avgas - ASTM D7719, Standard Specification for High Aromatic Content Unleaded Hydrocarbon Aviation Gasoline. This approval was earned through cross-industry evaluation by a 100+ member ASTM subcommittee, including representatives from industry advocacy groups, regulatory agencies, engine/airframe OEM's, fuel producers, testing laboratories, and more.
Click to expand...

All Swift did was take the formula and pay the fee to Apply to ATSM to create a standard based on their specific formula. The FAA standard formula is ASTM D910-17.
Swift can either match ASTM D910-17; or pursue some avenue with the FAA to get D7719 approved as an alternate. Currently there are two routes, via an AML STC or the PAFI program.

As for the old Lycoming/Continental running on 80 octane gas; they tend to be lower compression engines; and if they had enough planes flying would likely have been included in the auto STC since it was formulated in a manor similar to an AML (this is per reading the history of the Peterson STC on the net).

So it comes back to volume, you are either concerned only about the majority of planes, or the majority of the avgas consumers. If you care about the major consumers of avgas, then all the other planes are automatically taken care of.

Tim
 
To OP,

You didn't specify the a/c or engine. You might well not need 100 octane. And it's been a while since I've been back and forth with homebuilt testing, but IIRC, There's phase 1 (testing), and phase 2, normal ops *for an experimental*. I'm guessing that the FAA won't call it normal operation because experimentals do have (minor) restrictions on where they can be operated, unlike cert. a/c.
 
rv7charlie said:
To OP,

You didn't specify the a/c or engine. You might well not need 100 octane. And it's been a while since I've been back and forth with homebuilt testing, but IIRC, There's phase 1 (testing), and phase 2, normal ops *for an experimental*. I'm guessing that the FAA won't call it normal operation because experimentals do have (minor) restrictions on where they can be operated, unlike cert. a/c.
Click to expand...

The post is general in nature, but let's say for argument it is geared to those RV's with non conventional engines, such as Chevy or (fill in the blank) V8's. Engines that would normally run on 92/93 Octane unleaded auto gas.

It seems like this has been ongoing for years, and we are curious as to when a final result, i.e., fuel will be available for the mass market.

And, at what cost?

I see nothing but good coming from a UL fuel. Cleaner engines, for starters.
 
rv7charlie said:
To OP,

You didn't specify the a/c or engine. You might well not need 100 octane. And it's been a while since I've been back and forth with homebuilt testing, but IIRC, There's phase 1 (testing), and phase 2, normal ops *for an experimental*. I'm guessing that the FAA won't call it normal operation because experimentals do have (minor) restrictions on where they can be operated, unlike cert. a/c.
Click to expand...

I believe the OP was referring to the stages the FAA is going through on the Piston Aviation Fuel Initiative (PAFI). Not the testing of his specific RV build.
Phase 1 of the PAFI was lab testing and trying to narrow the field to a just a handful of formulas.
Phase 2 is testing in actual engines / aircraft.

Looks like they "should" have final approval and recommendations by the end of the year?
 
BrianDC said:
I believe the OP was referring to the stages the FAA is going through on the Piston Aviation Fuel Initiative (PAFI). Not the testing of his specific RV build.
Phase 1 of the PAFI was lab testing and trying to narrow the field to a just a handful of formulas.
Phase 2 is testing in actual engines / aircraft.

Looks like they "should" have final approval and recommendations by the end of the year?
Click to expand...

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?
 
TXFlyGuy said:
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?
Click to expand...

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?
 
tspear said:
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
Click to expand...

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.
 
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.
 
tspear said:
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
Click to expand...

Is that 8.5 compression ratio a misquote?

It is the common O-360 compression ratio.
 
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.
 
Pro seal

Mr Grinch said:
I wonder how all of these fuels react to Pro Seal...
Click to expand...

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
 
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
 
roadrunner20 said:
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.
Click to expand...

The incentive for me is the reduced valve guide wear and plug fouling. As a bonus, Swift fuel has a higher energy density than 100LL.

Don
 
Here is where I got the numbers:

AOPA webinar presentation on PAFI when established. A fair number of people asked about running autogas and 91UL. AOPA replaied that 80% of avgas is consumed by planes less then twenty years old. The planes by far run turbo or 8.5 or higher compression on engines that are maxed for HP. (Think of a new SR22 or Mooney, the engine is making 300+HP on a case originally designed for 260HP). The detonation margins are just not there to lower the octane.

FAA FAST day, PAFI was one of the topics. FAA claimed over 60% of the fuel was used by planes less then ten years old. Cirrus rep there backed the claim up; based on service records planes less then ten years averaged over 150 hours a year, from ten to twenty years Cirrus was seeing a decline down 50 hours a year. FAA also stated 8.5 or higher in summer months you have detonation problems for higher output engines. I believe the test case is rather brutal, something like 115 degrees at sea level. Basically think Death Valley or Houston in August. Again, this was always in reference to more modern planes.

I have not kept up with PAFI, or the 100LL debate, so I have no idea if there is newer/better data available; this all dates back to 2013 or so when I was paying close attention. It did not seem like they were making much if any progress so I stopped paying attention.

Tim
 
Can't speak to Swift fuel, but with over a decade of experience, mogas certainly makes a huge difference in plug fouling, an the oil stays cleaner, too. Don't know if it actually reduces valve guide wear, but I'm at least hopeful that it will reduce valve sticking.
 
94UL

Scroll

We have swift 94UL at a couple airfields in Wisconsin. It is 75 cents cheaper than 100LL and the engine runs great on it. I usually just just fill Up
Mixing with whatever 100ll is in the tank but have run complete tank fills.
 
Well, dare I say, the "incentive" is to not push more lead into the atmosphere. I know it's not much in the big scheme of things and it's not something that keeps me awake at night but if an alternative is available I, for one, will use it.

Europe, of course, is ahead on this with UL91 and 91/96UL becoming more widely available. As far as I know, though, there is nothing on the horizon to replace 100LL. Africa, sadly, is still behind so only 100LL is available. MOGAS is a bit "iffy" given the high temperatures and, in any case, has just started to have ethanol added.

Given the VANS types, nothing more than 180hp is really necessary (or 260hp for the -10). If you do want more, the Aerosport IO375 gives 195hp with 7.8:1 pistons. That just leaves the -14 which, I suspect, would run quite happily with an IO375 up the front.

I realise that there are still legacy airframes that need consideration but I suspect many of those could convert to 8.5:1 pistons without a huge performance penalty (as has been alluded to above).
 
Bugsy said:
Scroll

We have swift 94UL at a couple airfields in Wisconsin. It is 75 cents cheaper than 100LL and the engine runs great on it. I usually just just fill Up
Mixing with whatever 100ll is in the tank but have run complete tank fills.
Click to expand...

I wish I could get 94UL! This fuel is simply 100LL without the lead, so all the costs of special blending, segregated transport and storage are eliminated. My IO-360 and IO-540 are certified by Lycoming to run on it.

I've written to both the EAA and AOPA to promote this fuel. I get back the same noise on most fuel is burned by those needing 100LL so they only endorse a drop in replacement. What they don't discuss is how much this 100UL novelty fuel will cost.

I offered to them that if they promote some FBOs to carry the 94UL fuel, the market will decide. All those people wanting ~$10/gal 100UL might become a quickly evaporating pool as most will look again at engines that burn 94UL.

Carl
 
Carl's post raises an interesting point. The fact that turbo'd and other high performance (typically business use) aircraft consume 60-80% of the avgas, means that they are timing out their engines a lot quicker, too. If they were given the option to use fuel that was even 5% cheaper, how long would it take for the vast majority to convert to lower octane engines at overhaul?
 
Carl Froehlich said:
I wish I could get 94UL! This fuel is simply 100LL without the lead, so all the costs of special blending, segregated transport and storage are eliminated.

Carl
Click to expand...

Transport is not going to change. The quantity of fuel is so small it is not worth the losses of pipelining. This is right from our refinery rep at Flint Hills Refinery here in Minnesota, a leading producer of 100LL. Furthermore, just eliminating the lead content is not enough. If that was the case it would've happened years ago. Another anti-knock additive has to take its place.
 
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rv7charlie said:
Carl's post raises an interesting point. The fact that turbo'd and other high performance (typically business use) aircraft consume 60-80% of the avgas, means that they are timing out their engines a lot quicker, too. If they were given the option to use fuel that was even 5% cheaper, how long would it take for the vast majority to convert to lower octane engines at overhaul?
Click to expand...

A long time. To get to a lower octane fuel you need one of three things.
1. EFII
2. Lower compression
3. Reduced performance

Try explaining and passing the first option to the FAA.
Or the second and third to the airplane owner.

Tim
 
Extended Oil Change

Lycoming Service Letter 270 says that oil change interval can be doubled with unleaded fuel.

Switch to unleaded fuel and oil change is 100 hour instead of 50 with spin on filter or 50 hours instead of 25 hours with screen. We will still be required to change spin on filter every 50 and screen every 25. Many of us using unleaded fuel would end up changing oil every 4 months per Lycoming time interval instead of time in service.

I am one that wonders how many years it will take to get all the 100LL out of the tanks and only the unleaded replacement available.
 
Wide band 02

I've got a couple of wide band o2 sensors waiting to be installed when the unleaded thing comes along.
 
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