Ethanol's Effect

[andre nunes]

A lot of talking about Brazil's experience, so I decided to post my coments. First, let me introduce myself: My name is Andre, from Brazil and I'm building an RV9A that's almost ready to fly (just waiting the FFW Kit). My previous aircraft was a Tecnam ECHO P-92, powered by a Rotax 912S, that was sold to my hangar partner, so I still fly it. We always used auto gas on our rotax. Auto gas in Brazil has 89 OCT and 25% of ethanol and the little engine never complained. In fact, we can't notice the difference between auto gas and 100LL. The engine has now 700 hr and we always do the regular inspections and never noted anything wrong. So far so good. In our last annual, we found a few problems that are related to ethanol: a fuel valve leak - maybe the rubber seal - and a tank leak trought a rivet. Our aircraft is 10 yrs old. A lot of people use auto gas in Brazil, becouse only a few places has 100LL and using auto gas save us 45%. I wish I could use it in my new Superior IO-320, but I'll not take the risk.

[rv6ejguy]

Originally Posted by JDRhodes

That's less than 300 gallons in the hopper.
We build 'um lot's bigger in the USA!
http://www.airtractor.com/at-802a
And it'll run on Jet A, diesel, and probably french fry oil.

I'm guessing most other 300hp class AG planes haul about the same load, obviously not gonna compete with PT6 power.

[N941WR]

Originally Posted by andre nunes

A lot of talking about Brazil's experience, so I decided to post my coments...

Andre,

Welcome and thanks for posting your experience.

Best of luck with your -9A!

[pierre smith]

Originally Posted by rv6ejguy

I'm guessing most other 300hp class AG planes haul about the same load, obviously not gonna compete with PT6 power.

....like seeds and fertilizer are the main reason for the big hoppers. They're fluffy with a lot lower density than liquids. The Cessna Agtrucks with Conti IO-520's/300 HP, had 280 gallon hoppers but on a hot day, they'd have a tough time getting off with 200 gallons. You could fill them up with either rye or fertilizer and they'd be much lighter than 200 gals of water/chem mix.

Regards,

[N1593Y]

Originally Posted by rv6ejguy

My goodness, I hope you don't treat your RV like this. If you reach phase separation, you simply sump the tanks just like with gasoline- which you should be doing anyway.

You clearly do not understand phase separation. If your E10 fuel were to phase separate practically all of the ethanol and water, 10% of your fuel supply would separate and sink to the bottom of your tank as a highly corrosive blob. Phase separation is not incremental. If this were to happen you would have to know it immediately and completely pump your tank out because of the corrosive properties and because E10 is usually manufactured with a suboctane blending stock. The gasoline left after phase separation probably will not have the proper AKI rating for your engine. Regular unleaded, 87 AKI gasoline, is usually made with 84 AKI blending stock, it is here in Oregon. Premium unleaded 92 AKI E10 can be made with 89 AKI blending stock.

[rv6ejguy]

Originally Posted by N1593Y

You clearly do not understand phase separation. If your E10 fuel were to phase separate practically all of the ethanol and water, 10% of your fuel supply would separate and sink to the bottom of your tank as a highly corrosive blob. Phase separation is not incremental. If this were to happen you would have to know it immediately and completely pump your tank out because of the corrosive properties and because E10 is usually manufactured with a suboctane blending stock. The gasoline left after phase separation probably will not have the proper AKI rating for your engine. Regular unleaded, 87 AKI gasoline, is usually made with 84 AKI blending stock, it is here in Oregon. Premium unleaded 92 AKI E10 can be made with 89 AKI blending stock.

I've been blending race fuels and brews for a long time using Xylene, Toluene, Methanol, Ethanol, Acetone and gasoline and think I have a pretty good idea of what stays mixed with what and in what proportions. Depending on base stock gasolines that we have up here in Canada and the proportion of aromatics therein, phase separation like you describe has never been a problem that I have observed. There is a big difference in the proportion of alcohol which will stay in solution based on brands of gasoline here and the aromatic content. If you were purposely to pour a lot of water into the fuel, you might get what you describe. It just does not happen in regular automotive usage in my experience and our climate here can have shifts in temperature exceeding 20C/ hr. in the winter, probably the worst case for condensation in fuel tanks.

[N1593Y]

Originally Posted by rv6ejguy

>... It just does not happen in regular automotive usage in my experience and our climate here can have shifts in temperature exceeding 20C/ hr. in the winter, probably the worst case for condensation in fuel tanks.

Apparently we are talking about two entirely different applications. I thought this was an airplane forum, not a car forum. I agree that this would be extremely rare in cars, especially modern cars with closed fuel systems. I was talking about airplanes with open vented fuel systems, especially airplanes that could be stored for long periods outside in wet climates, using commonly available E10 mogas, not high ratio racing blends, which I would agree would be very unlikely to phase separate.

[rv6ejguy]

If I had gas caps on my RV which leak water (which I do) I'd change them or tape them over when storing the plane outside. It would be madness to rely on sumping the tanks to get rid of water that I could have prevented from getting into them in the first place.

The convoluted vent system in my 6A would only permit minute amounts of humidity to enter the tanks over a very long period of time and would be a non-issue IMO.

I bring out the auto side of ethanol fuels because there is vastly more experience in using it with millions of flex fuel cars worldwide. It could certainly be applied to aviation. An interesting link: http://en.wikipedia.org/wiki/Flexible-fuel_vehicle

People keep bringing up this hypothetical water issue with alcohol fuels. I don't see this being any more serious than water in avgas on a carbed engine and maybe even less serious since normal low amounts simply remain in suspension.

[N1593Y]

Originally Posted by rv6ejguy

>...
I bring out the auto side of ethanol fuels because there is vastly more experience in using it with millions of flex fuel cars worldwide. It could certainly be applied to aviation.

In order to be applied to aviation it would require a fuel injected engine with a computer that could alter mixture and timing and have sensors in the gas line to determine the level of ethanol and an oxygen sensor in the exhaust to sample the result of burn to modulate the fuel injection. That is what is in a Flex-Fuel car. You are proposing to haul all of that extra complex electronic equipment around, which will require redundancy, so that you can use a fuel with much less energy content that gives you much less range and is corrosive to aluminum and at high ethanol blends requires special pumps at the airport? (And we can't even get mogas pumps and tanks at our airports.)

People keep bringing up this hypothetical water issue with alcohol fuels. I don't see this being any more serious than water in avgas on a carbed engine and maybe even less serious since normal low amounts simply remain in suspension.

People keep bringing it up because it is one of the known problems with ethanol blended fuel and it is one of a number of reasons that no STC allows ethanol blended fuel. Neither EAA nor Cessna nor Petersen could see a way to make an ethanol blended fuel STC economically feasible: http://www.aviationfuel.org/faqs/ethanol_blends.pdf please pay particular attention to Section 11 on page 10.

[RV7ator]

For those of you who haven't connected the dots about ethanol in airplanes, here's a link to the latest Idaho Aviation Association newsletter. Pages 2 and 3 have articles. It fairly succinctly sums up the issues, and why we need to have access to ethanol-free mogas.

http://www.flyidaho.org/newsletters/...f?menuID=48~48
Four important points aren't emphasized in this thread:
1. $.51/gallon of your tax money is feeding this contentious issue and skewing market forces.
2. Though some of us don't care because experimentals have no fuel restrictions, the vast GA fleet must have an STC to use mogas without ethanol.
3. Don't expect help from the FAA. They've done nothing to head off this ethanol nonsense that's obviating STCs; even less likely are they to push back against new powers being elected tonight who think GA is a state.
4. The modifications and hugely complex machinations needed to field something beside 100LL will take years to implement.

John Siebold