Ethanol effects on 912 ULS's Bing carb

by Alberto Aragones in 912 / 914 Technical Questions 12 years ago

The past weekend we had a visitor airplane in our airfield. This is what we found last sunday in its 912 ULS, after having to abort takeoff because rpm were not reaching more than 4400. After inspecting carburetors we found that the membranes were perforated, sticky and seemed to be getting disolved. We inmediately suspected about ethanol in the automotive fuel being used. Some days later the pilot phoned us to confirm that the problem was caused by ethanol.

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Re: Ethanol effects on 912 ULS's Bing carb

by Roger Lee » 12 years ago

Roger Lee

131 5.38k 5.44k

Hi Alberto,

How much ethanol do you have in your fuels? Here in the US it is usually up to 10%, but usually hangs around
6-8%. Down in parts of South America it can top 22% and has been like that for years. Bing's do quite well with ethanol generally speaking. Unless your ethanol is awful high in concentration ethanol usually doesn't bother the carb diaphragm like that.

I would want to know how many hours on these parts and how old they are? They should be replaced every 5 years as part of the Rotax rubber replacement. I would want to know if any fluids, other chemicals or preservatives have ever been added to the fuel? This isn't normal for the small amount of ethanol we see. Has any fluids been sprayed into the air cleaner for starting or carb cleaning?

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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Re: Ethanol effects on 912 ULS's Bing carb

by Alberto Aragones » 12 years ago

Alberto Aragones

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The automotive fuel used in this case was the european standar, which I believe allows a maximum of 15% of ethanol. They have heard of some other cases like this one in france and that the french aviation authority is investigating the issue, which might not be caused by the ethanol alone but by ethanol in combination with other additives present in the european automotive fuel.

I don't know too much about the aircraft and engine that experienced this problem in our airfield, as I told you it was a visitor aircraft that stayed in our airfield just for the weekend. Once we replaced the diaphragm the engine ran ok and he left to his home airfield.

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