What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

100LL Future and Engine Purchase Concerns

Huh, that's interesting thanks for the link!

Here is a much deeper look at the history and some of the early research and aviation user data.
1PA70pN6zPM


A bit long but a lot of good information.
 
Last edited:
If an in tank pump fails, you can't access the fuel in that tank. The current pump life is excellent and vapor lock hasn't been an issue if proper location and plumbing practices are followed.

We strongly recommend that people use what's been proven over a half million flight hours with regards to the EFI fuel system if you don't want surprises or to be on a test program to validate a new design.

You could use a venturi-style cross-draw setup in the event of a pump failure in one wing. This setup has been standard practice in automotive applications that have the fuel tank straddle the driveshaft hump for some 20 years now.

It would make plumbing slightly more difficult and it would be a lot harder to change a pump in the event of a failure but no more difficult than a bad fuel sending unit.

And yeah I get the "don't rock the boat" comment. I was just curious if anyone had tried dual in-tank pumps in an aircraft before.
 
And yeah I get the "don't rock the boat" comment. I was just curious if anyone had tried dual in-tank pumps in an aircraft before.

Why? It's not needed. Dual parallel pumps and a simple duplex valve accomplish the same thing with less complexity and cost, and preserve the redundancy of dual pumps.
 
You could use a venturi-style cross-draw setup in the event of a pump failure in one wing. This setup has been standard practice in automotive applications that have the fuel tank straddle the driveshaft hump for some 20 years now.

It would make plumbing slightly more difficult and it would be a lot harder to change a pump in the event of a failure but no more difficult than a bad fuel sending unit.

And yeah I get the "don't rock the boat" comment. I was just curious if anyone had tried dual in-tank pumps in an aircraft before.

I'm not understanding what you're describing here. If you have one pump in each tank and the pump fails, you can't get at the rest of the fuel in that tank.

In aviation, once we have demonstrated the reliability of a layout or system, we repeat that without deviation to get the same results over and over.

If you want to put pumps in the tanks, you could. I've just outlined the main reason it's not done. We have a proven, very reliable layout now with few drawbacks. I'm not sure why it would be a good idea to change that. What would be the advantage over the existing layout?
 
I'm not understanding what you're describing here. If you have one pump in each tank and the pump fails, you can't get at the rest of the fuel in that tank.

In aviation, once we have demonstrated the reliability of a layout or system, we repeat that without deviation to get the same results over and over.

If you want to put pumps in the tanks, you could. I've just outlined the main reason it's not done. We have a proven, very reliable layout now with few drawbacks. I'm not sure why it would be a good idea to change that. What would be the advantage over the existing layout?

You use the velocity of the fuel to create suction to basically create four pumps out of two. In an EFI setup you would put it on the return line since you don't want any air in the event of the other side running out of fuel. When both pumps are running they're cross feeding at the "same" rate (you would probably size the restrictor to be slightly larger on one side so you don't feed fuel out the vent when running on both). If one were to die the other would pick up the slack and cross feed the dead side into the active side.

And I understand the current setup is quite reliable. I am not at all questioning that. However in-tank pumps live a happier/cooler/quieter life and you don't have to worry about vapor pressure at all and the packaging is a bit simpler since most of the bulk lives in the tank. It's more of a question of "has it been done" and "why not if not?".

Here is a random image I found that describes the setup. Just imagine each side of the saddle is a wing:

Jet_Pump-Return_System.png
 
Same as motive flow? Motive flow is used in fuel tanks of most biz jets I'm familiar with.
Here's a basic description I found.

https://aviation.stackexchange.com/questions/34301/what-is-motive-flow-and-why-is-it-used-in-some-aircraft-hydraulic-systems

Yes. You'd use the motive flow to move fuel from the dead tank to the active tank in the event of a pump failure. In a dual-pump situation both pumps would be moving fuel equally and would cancel each other out (or you would have pressure valves that prevent the cross-flow in equilibrium).
 
Yes. You'd use the motive flow to move fuel from the dead tank to the active tank in the event of a pump failure. In a dual-pump situation both pumps would be moving fuel equally and would cancel each other out (or you would have pressure valves that prevent the cross-flow in equilibrium).

I'm familiar with the widespread use of jet pumps in jet aircraft. With the present system, we usually run on one pump at a time and there are less components and plumbing so less weight and complexity.

This being experimental aviation, nothing is stopping you from implementing your ideas on your aircraft if you see some advantages there.

I just don't see any advantages with this layout.
 
Do not stress.

The PAFI process was fatally flawed right from the beginning. Recently proven.

There is a certification project almost complete and has taken time due funding and apathy of the market to get behind it, but is literally "months" or "weeks" from a major milestone.

G100UL is the likely fuel you will have when the time comes. So relax. Build on.

Most recent AOPA article on 100LL replacement. EAA had a similar article.

Thanks Gary. Interesting info. Sounds like discussion @ 5 min mark on
AOPA video https://www.aopa.org/news-and-media/all-news/2018/august/30/unleaded-avgas-testing-to-resume-this-fall?utm_source=epilot&utm_medium=email&utm_content=adv&utm_campaign=180830epilot could be related to what RV10inOz brought up in his post.
 
Last edited:
Will be interesting to see how this all shakes out. Shell has the size/ funding and existing network to make this happen more quickly IMO than the other players but hopefully Swift and GAMI will also be in here as alternative competition.
 
Interesting this debate is still going on. Fifteen years ago when I was making the decision on the engine and fuel system for my 7A everyone was worried then that 100LL was on it's way out. If there is a large enough market, someone will continue to produce it, or a reasonable substitute.

Roberta
 
Shell developed a really cool new paint stripper. SWIFT won't start in Winter or if you brew it synthetically the components cost north of $12/gal before you get started. And it didn't work (not when my data source was current).

Neither is fungible with the existing avgas. At some point you need to have a changeover period and a long and lengthy one at that.

One fuel does tick all the boxes and does better in some areas than current 100LL., and it was never part of the fatal flawed PAFI project. Make of that what you will. And just because one company is huge and has large cash sources does not mean that they can or will solve the problem. They haven't.
 
Shell developed a really cool new paint stripper. SWIFT won't start in Winter or if you brew it synthetically the components cost north of $12/gal before you get started. And it didn't work (not when my data source was current).

Neither is fungible with the existing avgas. At some point you need to have a changeover period and a long and lengthy one at that.

One fuel does tick all the boxes and does better in some areas than current 100LL., and it was never part of the fatal flawed PAFI project. Make of that what you will. And just because one company is huge and has large cash sources does not mean that they can or will solve the problem. They haven't.

It will be a tough haul for any company without the size and financial/ refining/ distribution resources to do this no matter how good their formulation might be. That's a hard reality unless they sell the rights to someone like Shell- if Shell would buy.

It's one thing to come up with a recipe that ticks all the boxes, quite another to get this in world wide or at least country wide distribution.

There is at least one other US player developing UL avgas outside of PAFI, who few people know about. I was just talking to someone in that company last week and they have a very good formulation it sounds like.
 
Ahhh memories. There once was a time when this website didn?t exist. RV builders communicated via an email list where we either received one email containing all of the emails for the day or hundreds of emails spaced apart by seconds. It was great. Back when that list was an infant was the first time I heard someone say with certainty that Low Lead was going away shortly and we were all doomed.

I am still waiting....but I did finally stop holding my breath. So, until Hades freezes over and the seas of Low Lead dry up....I?ll keep destroying the environment with buckets of lead, bragging about my carbon footprint and whacking every baby seal I see on the head with a hammer.
 
Yes, but the difference now is that there is a growing number of mostly non-aviation folks who want all the lead out of all gasoline due to environmental concerns, and have sued to accomplish that goal.

Yes... there are rumblings in the UK about Innospec on the River Mersey -

innospec.jpg


Which is the only supplier of TEL - tetra ethyl lead, the lead bit of 100LL - in the free world.

https://www.petro-online.com/news/m...aking-news/where-is-leaded-petrol-legal/43931

Every time I go to Liverpool I look across the river to see that the plant is still there :) It was still there a year ago.
 
Last edited:
Lead free

Lead free racing fuel has been around for a while at Sunoco. Granted it?s high cost, but if I recall, it was something like 110 octane. If the stuff would work in AC, then I wonder what the cost would be if the supply chain was a larger?
 
130 Octane

Does anybody have the accurate records for the make up of 130 Octane gasoline that was used in the 1940's when Mustangs, Spits and other merlin powered AC used it?
 
100LL Update

Latest update (Sep 7, 2018) on the Piston Aviation Fuels Initiative (PAFI) from the FAA website.

FWIW: "...PAFI flight testing and some engine testing was halted, resulting in a delay in testing completion ? from December 2018 to mid-2020."

https://www.faa.gov/about/initiatives/avgas/

I'll continue to check the website daily for further updates :) .
 
Does anybody have the accurate records for the make up of 130 Octane gasoline that was used in the 1940's when Mustangs, Spits and other merlin powered AC used it?

Isn't it *still* used by the air racers?
 
Does anybody have the accurate records for the make up of 130 Octane gasoline that was used in the 1940's when Mustangs, Spits and other merlin powered AC used it?

Here is the spec for the 150 octane stuff -

http://www.wwiiaircraftperformance.org/150grade/150-grade-spec.pdf

And lots of history on the introduction of 150 to replace/supplenet 130 octane fuel in WWII

Lots of links in the footnotes -

http://www.wwiiaircraftperformance.org/150grade/150-grade-fuel.html
 
Just a slip of the keyboard.......... when G100UL gets out there (soon) it will perform like the old purple gas and I have seen the test reports from Dixie Labs.

Lots of good things..........but geez it takes time........
 
Sorry, I apologize ahead of time for this post, but I only get on this soapbox once a year.
For those interested, here's an update (June 20, 2019) on the PAFI program from the FAAs website. https://www.faa.gov/about/initiatives/avgas/
I attended the PAFI forum at OSH this year hosted by reps from EAA, AOPA, and FAA. Unfortunately, no announcement of any breakthrough was discussed. According to the panel members, tetraethyllead (TEL) was the "magic bullet" in the 1920s and it remains so today. They stated there is no simple fix and were actively inviting new participants with ideas to join the program. A question was asked by someone in the audience as to why eliminating AVGAS was such a big deal since, "in the big picture", it produces such a small amount of lead emissions. The panel agreed that is is a very small amount of lead however, "it's a done deal". Suits filed from environmental groups beginning in 2006 are still on the books, and while no action has been taken since around 2012, the fact remains. The panel mentioned several times "we are committed to removing lead from AVGAS". They are probably required to make that statement not knowing who is in the audience.
All that said, AVGAS probably not going away anytime soon, I understand that. However, I do find it interesting that engine manufacturers continue to build, and more importantly we continue to BUY, engines that require a fuel the FAA, EPA, and other agencies continue to state they are committed to eliminate. I wonder if a better path for the last several years may have been spending time and money (I think $35 million was the amount congress gave the PAFI program), in researching and developing engine solutions rather than a replacement fuel. During that time, airplanes would have continued to burn 100LL, and as TBO's and service life of these engines were reached it may have been possible to replace with an updated engine that doesn't require AVGAS. My vote would be for a JET A because of world-wide availability, ease of refinement and distribution, and only one pump required at the airport. Don't get me wrong here. I don't want AVGAS to go away anytime soon, I sure enjoy flying my buddies RV10 when I get the chance. However, I want a long term solution so future generations can have the opportunity to enjoy flying small airplanes like we have. I'm just not convinced a replacement fuel is the answer.
 
Several big companies continue to work on a 100LL replacement both within and outside PAFI. It takes a long time to gather test data which will satisfy the FAA. Some have not submitted anything to the FAA yet while the formulations undergo independent testing.

It will have to have similar density and other characteristics to be approved. Not so easy as it seems.

No way new engines will replace what's in the fleet now, any time soon. Not practical on so many levels, both technical and economic.
 
Last edited:
I don't believe we have to worry about LL fuel not being avail for quite a long time yet! The issue might be cost in the future, availability is the least of our worries. So fly fly fly:D
 
Fuel

Maybe some of our colonial brothers from accross
the pond would chime in here. A few years ago in
Great Britain they allowed you to burn ?auto fuel ?
in several types of aircraft. One of the restrictions
was not flying above ?4000 ft. Run down to your
neighbor hood gas station fuel up and take off in
the summer months then climb up to cool off and
you would be surprised how many people encounter
ruff running engine problems that are probably the
onset of vapor lock problems.
 
Maybe some of our colonial brothers from accross
the pond would chime in here. A few years ago in
Great Britain they allowed you to burn ?auto fuel ?
in several types of aircraft. One of the restrictions
was not flying above ?4000 ft. Run down to your
neighbor hood gas station fuel up and take off in
the summer months then climb up to cool off and
you would be surprised how many people encounter
ruff running engine problems that are probably the
onset of vapor lock problems.

It can certainly be done, but not as simply as some folks would think. I've been operating almost 600 hours now on 91 premium autofuel (with ethanol) at altitudes in the mid-teens quite regularly, and I've been to FL210 with it once just to see what would happen, all was good. But to be fair - I did make some mods to my fuel system to allow me to do that, it's a little more complicated than just "run down to the neighborhood gas station".
 
Greg, some of our friends in Oz have seen some serious valve seat problems operating on mogas in a fraction of the time you have. Apparently Swift put an additive in their UL fuels to mitigate this problem.

Any indication from leakdown and borescope tests that you are seeing these effects?

Very curious.
 
Greg, some of our friends in Oz have seen some serious valve seat problems operating on mogas in a fraction of the time you have. Apparently Swift put an additive in their UL fuels to mitigate this problem.

Any indication from leakdown and borescope tests that you are seeing these effects?

Very curious.

Nothing on leakdown or valves yet - but I'm down for annual and SDS install right now and haven't gotten to that part yet, I'll let you know if I see anything in the cylinders or valves. I suspect that they are getting into detonation and running elevated temps, and causing the problems that way - it's very easy to do with compression higher than 8.5:1 and without full engine monitoring you won't even know it's happening till the damage is done. Last time I looked inside the cylinder was at 420 hours, I'll let you know what I find this time.
 
Looks like the program is in high-speed neutral, just as expected.

I'm so glad you said that.

Edit: My other answer was funnier but included a political reference which, intended to be possible to take as supporting either side, obviously would be taken as a condemnation of both sides. /end edit

As I read it I thought I heard the pig explaining to the other animals that all 100LL replacements are certainly equal, but some are more equal than others.
 
The goal of the PAFI program is literally impossible - trying to please everyone. You're never going to get there. They need to make a fuel that is a drop-in replacement for ALL engines in ALL applications, and at a price that is equal or lower than current fuel, and all that in as short a time as possible.

It was doomed to failure before the politicians even picked up the scent.

I believe that 100LL will eventually go away - but it will not be possible, EVER, to do so easily or painlessly. That's just part of life.
 
Build on with faith

Shawn,

This is a more philosophical answer to your comment about having the 100LL dilemma taking the wind out of your sails. So, if you are looking for more technical response, skip to the next post.

Ten years ago I was just finishing my RV-8 tail kit while working for a major manufacturer of piston aircraft and business jets. I was in a meeting with the CEO of one of the largest distributors of avgas and jet fuel in the U.S., and left the meeting convinced that 100LL would either be gone, or cost $50 per gallon in the near future. It definitely took the wind out of my building sails, so I finished my empennage and boxed the pieces up for storage.

Fast forward 10 years to today, and 100LL is still available and at a reasonable cost. If I had kept building, I might be flying by now.

As I'm sure many people in their 50s do, I stopped to think about what is really important in life and what I want to accomplish with the fewer years I have ahead of me. Aviation has been a core element in my life since I was a child, but without an airplane of my own, I feel like I have not fully enjoyed or committed to my passion.

But what about 100LL in the future? I don't know, but I do know that in 20 years I definitely don't want to look back and regret giving up on my dream of building and flying my own airplane.

So, I just took delivery of the wing kit for my RV-8.

And, while I still choke on the thought of spending $30k on a new Lycoming, that purchase is still probably a decade off for me, and I will continue to build on faith. Faith that some type of powerplant and fuel will be available when I finish. It might be 100LL, it might be 94UL, it might be Jet-A. And I am watching the electric propulsion developments very closely.

We probably won't see the flux capacitor from Back to the Future in our lifetimes, but I do have faith that technology and market opportunity will come together to give us some way to keep flying these wonderful machines.

Build on!

Tom
 
Go diesel? Look no politics allowed but read my mind. :rolleyes: Get out and fly (and vote). :D

Adult folks living today will never see 100LL go away in their lifetime. Also lead additives will be available one way or the other.... Lead not only lubricates the valves at high temps, it adds octane needed for the engines we fly.

Before 100LL is banned if that ever happens is price. Authorities will make 100LL so expensive with taxes no one will be able to afford to buy it. Seriously the pollution of GA piston aircraft, small fleet and limited hours flown is peanuts. I know logic does not come into play with these authoritarian dreams the "Gov" comes up with.... for our own good....
 
Last edited:
I'm at a similar stage and timeline in my RV8 build as Tom (two posts up). There's been a lot of talk the last 10 years about small turbines. Several attempts, some more successful than others, and none have made it to market..yet! I've got my fingers cross that there will be a decent option available in 10 years for a small turbine engine for the RV series. I do fear the cost as turbines mean big dollars, and I don't have 100 grand to spend on an engine.

The 100LL problem affects a lot more than just us. The flight schools need something for their 152s, and other training aircraft. Lots of charter companies with big Cessna and Piper twins; Navajos, 421s and the like all burning 100LL and aren't going away.

I am confident that whatever replaces 100LL will not be much different in price and will remain readily available. The world-wide consumption of leaded gasoline is miniscule compared to what it was when lead was in car gas. There isn't the same environmental pressure and concern due to the much lower volume. I suspect the actual amount of lead in 100LL is already quite a bit lower than it was 20 or 30 years ago. Decreasing the quantity to the minimum allowable specification. This is just a suspicion, and have nothing to back this up.
 
I remember being in 4th grade and being told the world was running out of gas and that there would not be any cars when I grow up...
Don't worry about it, buy a 100LL engine and enjoy it for as long as you want...
 
91AKI with ethanol

I've been running 91AKI pump gas here in Wackinfornia...yup, straight from the local Quick Stop, meaning 10% ethanol.

I have a tank in my truck bed that I fill at the gas pump, and fill my airplane from my truck bed tank, which I've done about every two to three days since the summer of 2018, which is something like 370 hours so far.

My UL350iS (8.7:1) cylinders are clean, compressions are great and the engine runs like a champ. I've never had any issues with vapor locking, detonation or ethanol related issues.

Fuel disclosure: I have run 100LL on occasion, generally when I'm traveling XC and can't get MOGAS and use Decalin when doing so.
 
The goal of the PAFI program is literally impossible - trying to please everyone. You're never going to get there. They need to make a fuel that is a drop-in replacement for ALL engines in ALL applications, and at a price that is equal or lower than current fuel, and all that in as short a time as possible.

It was doomed to failure before the politicians even picked up the scent.

I believe that 100LL will eventually go away - but it will not be possible, EVER, to do so easily or painlessly. That's just part of life.

Actually, I suspect Swift Fuel filled the bill apart from potentially being a bit pricier (which they could change by lowering the ridonkulous AvGas taxes).

Even more interesting in the near future would be to hook large solar farms (daylight only) to the Navy process for creating fuel. As the price of non-dispatchable solar energy keeps going down, at some point it will become cheaper to use this process than anything pumped from the ground. Note that although their primary purpose was to create a jet fuel / diesel alternative, the same process can create "lighter fuels" as well. They might have to modify the process a bit to allow "suspending" it at night (to avoid having to buy more expensive power either stored or from other sources), but it seems feasible.
 
Shawn,

This is a more philosophical answer to your comment about having the 100LL dilemma taking the wind out of your sails. So, if you are looking for more technical response, skip to the next post.

Ten years ago I was just finishing my RV-8 tail kit while working for a major manufacturer of piston aircraft and business jets. I was in a meeting with the CEO of one of the largest distributors of avgas and jet fuel in the U.S., and left the meeting convinced that 100LL would either be gone, or cost $50 per gallon in the near future. It definitely took the wind out of my building sails, so I finished my empennage and boxed the pieces up for storage.

Fast forward 10 years to today, and 100LL is still available and at a reasonable cost. If I had kept building, I might be flying by now.

As I'm sure many people in their 50s do, I stopped to think about what is really important in life and what I want to accomplish with the fewer years I have ahead of me. Aviation has been a core element in my life since I was a child, but without an airplane of my own, I feel like I have not fully enjoyed or committed to my passion.

But what about 100LL in the future? I don't know, but I do know that in 20 years I definitely don't want to look back and regret giving up on my dream of building and flying my own airplane.

So, I just took delivery of the wing kit for my RV-8.

And, while I still choke on the thought of spending $30k on a new Lycoming, that purchase is still probably a decade off for me, and I will continue to build on faith. Faith that some type of powerplant and fuel will be available when I finish. It might be 100LL, it might be 94UL, it might be Jet-A. And I am watching the electric propulsion developments very closely.

We probably won't see the flux capacitor from Back to the Future in our lifetimes, but I do have faith that technology and market opportunity will come together to give us some way to keep flying these wonderful machines.

Build on!

Tom

Thanks Tom!
Out of all the replies to this thread, your "philosophical answer" makes the most sense to me.
 
Last edited:
Back
Top