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Alcohol Fuels in Ultralights and Lightplanes

By Dan Grunloh, EAA 173888

Alcohol-blended fuels have been entering our national fuel system for decades, and their role is increasing. It’s happening for economic reasons, as a feature of overall energy policy, and for considerations of national security. We few ultralight and lightplane pilots cannot possibly change that trend. By now most pilots have heard of the problems that alcohol-blended gasoline can bring, but our newest enthusiasts may be unaware due to the success of its use in our automobiles. EAA has recently published some excellent articles on this subject. See “Ethanol and Rotax Engines” in the June 2006 issue of EAA Sport Pilot and Light-Sport Aircraft.

A more recent look at this issue was a two-part article in the May and June 2009 issues of Sport Pilot called “Fuels and Engines.”

These articles should be considered required reading for all ultralight and lightplane pilots. With all that has been so expertly written, why do we need another article on alcohol fuels? Ultralights and lightplanes have different hardware, different needs, and different options than much of the rest of aviation. A 5-gallon fuel tank presents wider logistical options than one that requires 40 gallons to top it off. We have access to excellent information about the problem, and experts are debating our course for the future. However, we need information for tomorrow morning. We need practical methods to deal with the problem because we will not stop flying. There is ample evidence the warnings are still not making it out to everyone in our community. We begin with one of several reports collected by the author from various sources within the last year:

“It was a cold winter morning with a dark blue sky. The Rotax 447 engine started on the first pull. During warm-up, the pilot noticed a faint trace of moisture condensing on the outside of the fuel line near the bottom of the tank. A closer look proved it was actually inside the clear plastic line. The swirling cloud gradually expanded, moving upward toward the carburetor. The whole fuel system was soon filled with the hazy fluid. After shutdown, water droplets were found in the fuel lines and carburetor float bowl. The lower half of the fuel tank contents appeared cloudy. Had a flight been attempted, it would surely have ended with an unplanned landing.”

It was a typical case of phase separation. Alcohol and moisture absorbed into fuel comes back out of solution. It returns to the aqueous or polar phase and appears as microscopic droplets that coalesce and form visible water droplets. How could this happen to an experienced operator with an aircraft that is always fueled with alcohol-free gasoline? The previous afternoon was warm, and in a hurry to join friends, the pilot topped off the tank with a 10 percent alcohol-blended auto fuel (E10) from a can that had been sitting around for a while. It was filtered with a water-removing funnel, and the engine ran perfectly for the afternoon fun. During the night, the temperature dropped 30 degrees, enough to induce phase separation.

The threat from absorbed water in alcohol-blended fuel can never go away or be cured with a simple device. Alcohol-blended fuels deteriorate with storage, and alcohol is a solvent that can damage some fiberglass fuel tanks and rubber components in fuel systems. Alcohol, and the water it attracts, contributes to the corrosion of metal surfaces. Most new equipment including engines, fuel tanks, fuel lines, and filters are resistant to the E10 alcohol blend, but you can’t always be certain. All older equipment is suspect. Alcohol fuel acts as a cleaning fluid and can loosen built-up residues or sediment that ultimately clogs filters or carburetor jets. The scenario described in this excerpt from an EAA Chapter 1447 newsletter article by Gary Waner has probably been repeated numerous times:

“What will alcohol-blended fuels do to my engine? Here is an example. Larry has been having problems with his engine since last fall. At times it ran like it did when it was new. Other times it wouldn’t run at all. Those of us who worked on the problem suspected an electronic one. After much testing, several of us who call ourselves mechanics urged Larry to put the electrical system back together. Les and I were with Larry as he returned the electrical parts to the engine. Before Larry started (incidentally, Larry is a good mechanic himself), he decided to check the carburetor bowls for contaminates. At this point, I think that he found the problem. His carburetor bowls held a jelly-like substance that would not go through jets and small orifices. In fact, it had gummed the carbs up so badly that he had to soak them in cleaning solution to get rid of the stuff. He cleaned the carbs thoroughly and then started the engine. It would seem that the problem was a fuel one from the beginning.”

Fortunately, there are fairly simple solutions to these problems, and they are available to almost everyone. The first option is to avoid using alcohol-blended fuels entirely. It’s simple to understand, but much harder to accomplish. It may be the only good option for older equipment or anyone who isn’t sure about his or her fuel system or engine. It’s also best for those who have the newer hardware approved for E10 auto fuel. Alcohol fuels present problems for everyone. Avoid the alcohol and those problems do not materialize. Driving to every filling station in your area to find alcohol-free fuel may be a completely useless exercise in many parts of the country. Pumps are not always marked correctly, and the attendant often doesn’t have accurate information. When there is any doubt, test the fuel for alcohol following these simple instructions.

Alcohol test
Alcohol Test

You can make your own test kit from an olive jar or buy a commercial version here or here.

The best place to start your search for alcohol-free fuel is your nearest EAA chapter. Save time and ask the folks who are likely the most able to help. If you have no local EAA chapter, start one. Alcohol-free fuel users are a small niche market composed of antique car and tractor enthusiasts, the boating industry, and aviation. So you can also ask at your local racetrack or marina.
A good source is alcohol-free aviation mogas for certificated aircraft engines operated under the auto-fuel STC. Nationwide, the percentage of airports with aviation mogas is very small, but local availability varies tremendously. Wisconsin has the largest number of airports serving mogas for airplanes. About 20 percent of nontowered airports in Wisconsin that pump fuel are listed as having mogas. In the surrounding Midwestern states, the rate drops to 10 percent to 15 percent. In many parts of the country you could drive for hundreds of miles and not find any aviation mogas for your ultralight. Mogas typically has an 87-octane rating, which is adequate for most piston-ported two-cycle and light auto engines. Check your owner’s manual. The Rotax 618 and 100-hp 912 series require a higher octane. Begin your search with this list of mogas airports.

The next best source of alcohol-free fuel is available almost everywhere. It may come from a pump or a truck, but you can be confident it is alcohol-free, of good quality, and stores well. The federal government requires it.

Avgas 100LL
Alcohol-free fuel

Aviation 100LL is the last good option for those who cannot or will not use E10 blended auto fuel. Some have believed it is not safe for our converted snowmobile engines, but 100LL is now approved for use in most Rotax two-cycle engines. No doubt there are some two-cycle engines or applications that have experienced problems with avgas. Most users can expect a slight change in engine temperatures and perhaps a small change in power or range, and the spark plugs may require more frequent service. Your wallet will be lighter, but the cost is not prohibitive. A fuel burn of 3 gph will add about $3.50 per flying hour to the overall cost. Individual pilots have reported logging more than 1,000 hours on their Rotax two-cycle engine while using 100LL avgas. You can see Rotax-powered ultralights and lightplanes attending major fly-ins that flew in from hundreds (or thousands) of miles using 100LL for much of the trip. Rotax 912 operators using 100LL should follow these special instructions.

But, what if you can’t always get what you want? You have encountered head winds and have landed at a private airpark with no fuel. Perhaps the pumps are already closed at the public airport, but there is a filling station across the road. Many pilots have already decided to use the E10 ethanol blend because it’s all they can find. Life is too short to stay on the ground and worry about your fuel.

To avoid the inevitable, clever individuals have suggested removing the alcohol from blended fuels by using a “water wash.” They propose adding excess water to the mixture to extract the alcohol in the aqueous phase and then separate the fluids. It probably won’t work because it may not remove all the alcohol or water, and the excess water might remove chemical additives in the gasoline that are needed. Your engine becomes the experiment. Before making the jump to alcohol fuels, all pilots must first try to ascertain that their engine and fuel system can tolerate it. Contact your engine and airplane manufacturer. Replace old tanks, fuel lines, filters, or any rubber parts with new equipment. Rotax has recently approved the use of E10 alcohol-blended fuel in its most-popular two-cycle aviation engines.

Fortunately there are simple ways to greatly reduce the hazards of alcohol-blended fuel. DO NOT STORE THE FUEL. We hear it all the time, but how many take heed? Alcohol and gasoline interact fairly quickly to form compounds that smell like old varnish. The water always comes in after you buy the fuel. Buy it, fly it, and discard the remainder; following this advice will eliminate most problems. De-fueling the plane sounds radical, but it’s not rocket science and is extremely effective. Such practices are standard in the boating world where engines are idle for extended periods. It’s easy for the foot-launched powered paraglider (PPG) pilots. They can simply pick it up, turn it over, and pour out the fuel for use in the lawn mower. The rest of us will need a drain, siphon, or transfer pump. If you fly 1.5 hours per week, de-fueling the plane will reduce exposure to the harmful effects to 1 percent over the space of a week. Few things in aviation are that effective.

If you must store ethanol-blended fuel, keep your fuel cans full and vents closed, if possible. A closable vent on the aircraft tank is probably not a good idea. The rate of water absorption is proportional to the surface area exposed to the atmosphere. Almost full is not good enough; it must be right up to the top. The key is to keep several sizes of fuel cans handy for your fuel storage. Top them off and take the remainder home for other uses. Store your fuel in a cool dry place. A SPECIAL WARNING is appropriate for two-cycle engines using pre-mix instead of oil injection. Generally, pre-mixed fuels should not be stored for extended periods because chemicals in the oil could either react with the gasoline and produce precipitates or diminish desirable properties of the oil. Prolonged storage of pre-mixed alcohol-blended gasoline is really asking for trouble because the alcohol, and the water it brings, will add to the “witches brew” that can result. If you store such concoctions in a vented metal can long enough, it will eat a hole in the bottom of the can. Don’t store it in your plane too long.

Control the risk of alcohol fuels by adding a new item to your regular preflight. Inspect the fuel before every flight for clarity to ensure there is no cloudiness or haziness. A clarity check may reduce phase separation incidents because ultralights and lightplanes do not typically climb to altitudes that would result in an extreme temperature drop. Any cloudiness is a sure sign the fuel must be discarded. The terminology that occurs frequently in literature about alcohol fuels is “clear and bright.”

The conventional translucent ultralight fuel tank will not suffice. A gascolator with a quick drain or clear glass sump is rarely seen in ultralights. The conventional self-closing Curtis-type drain valve and sampling cup is standard in general aviation and would be perfect. Make sure the cup is clear, and inspect the fuel in good light. Many ultralights are sold without any type of fuel drain. A drain point in the form of a two-way fuel tank selector valve could be located at a low spot in the fuel lines, but if it must be safety-wired closed, it will not be used. Finally, the last defender of your plane and your safety could be the industry standard, clear, heavy duty urethane fuel line. Replace it often so it stays clear.

Fuel drain
Last chance

To simulate phase separation, fill a clear bottle with E10 blended gasoline. Next add a small amount of water and shake. That condition must be detectable in your fuel before every takeoff. After the haze settles out, place the test jar in a cold place. As it cools, the fuel will turn cloudy again right before your eyes. The engine may run on this mixture, but the water droplets that form will accumulate and cause problems.

It’s the pilot’s responsibility to make the final decision about fuel and its suitability for flight. Don’t let anyone else make the decision for you; however, you should comply with all applicable regulations. Whatever your decision, don’t let worries about fuel keep you on the ground. Every day passed is one less day in your flying life. Let’s go flying!

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