What effect does ethanol have on airplanes?

“”What is the effect of having mixed 10% ethanol with avgas and/or ethanol-free mogas on two or three occasions?”” asks reader Ken Rice. “”The place where I bought ethanol-free mogas lied to us about the change to 10% ethanol. I only found out about it when I asked the tanker driver.””


“”What is the effect of having mixed 10% ethanol with avgas and/or ethanol-free mogas on two or three occasions?”” asks reader Ken Rice. “”The place where I bought ethanol-free mogas lied to us about the change to 10% ethanol. I only found out about it when I asked the tanker driver.””

If ever there was a question that I shouldn’t answer, this is it.

On the other hand, if ever there was a question that should be answered, this is it.

Most people would just tell him this is why it is important to test every batch. If you worked for a large company with a legal department, the only answer would be to replace every rubber component in the aircraft ? or, better yet, ground the airplane and sell it for scrap. Neither answer is of any value to someone in the real world, so what would a common-sense answer be?

The main concern with using ethanol fuel in an aircraft is that the fuel will clean up a dirty fuel system and chemically attack the rubber components in the fuel system. As our reader has not had any problems so far, I will assume that his fuel system was clean enough so that no problem has occurred.

Nevertheless, he should check throughout his fuel system and look for foreign matter in places like the float bowl. If everything is normal, then look at the float. If you have a composite float, you may want to replace it. If a metal float is available, try one. Also, while I do not believe there are any composite needle and seat assemblies in use, that could be a problem, too.

Then there is the concern about fuel lines and components such as fuel bladders. The older the aircraft, the greater the concern about the rubber components. I recently received an email from a gentleman who claimed that all current aircraft fuel cells are manufactured to be ethanol compatible. I have not been able to confirm that, since there is an implied liability if an aircraft company did confirm it positively. If Ken has an older aircraft with the original fuel bladder, he should have it inspected.

Don’t forget the fuel lines. If they are old, original equipment fuel lines, they should be inspected carefully or replaced. Ethanol fuels tend to attack some rubber compounds and make them brittle or, worse, cause small pieces to flake off. These small pieces could plug up a small passage in the fuel system and cause a real problem. That’s why continued inspection for leaks or small pieces of foreign matter is recommended.

This is a very real problem with no clear answer. The older the aircraft, the bigger the problem. In fact, there are some late model experimental aircraft that have been built to run on pure ethanol.

I can tell people like Ken that I am 99% confident that if he inspects his fuel system carefully and continues to fly, he should not have a problem, but there are hundreds and even thousands of people who may have this problem ? so you do the math.

Ben Visser is an aviation fuels and lubricants expert who spent 33 years with Shell Oil. He has been a private pilot since 1985. You can contact him at Visser@GeneralAviationNews.com.

Comments

  1. you may want to check http://www.buyrealgas.com to find a no ethanol station near you.

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