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Jabiru - Autogas Advisory

PostPosted: Tue Feb 22, 2011 1:59 pm
by justaircraft
Good morning,

The following statement (between the ========marks below) is attributed to Jabiru USA - regarding autogas & ethanol and provides some inkling of what goes on with autogas.

We have a lot of discussions about ethanol. This article hints that some of the problems may be less due to ethanol and possibly more due to inconsistent composition of autogas with ethanol where varying amounts of contaminants and varying amounts ethanol formulation can play into material incompatibilities that we are not normally thinking about. I recall testing various grades of fuel hose by cutting off short pieces and letting them sit for several months in a container of 95% ethanol - none of them swelled. (If I had dunked the hoses in MEK or acetone - ????)

If a person happens to get a load of ethanol formulated autogas which happens to carry a few of the mentioned contaminants - a person can consider the possibility that something other than the ethanol fraction may be responsible for some of the things we see happening that we don't like in aircraft.

For the record - I have been running non ethanol autogas and have never experienced a problem. I have a friend who uses E 10 in his rotax and never a problem.

The fact that some of us have had problems with auto gas and some have not may speak to the inconsistent composition of autogas (which can vary by location and refinery and pipeline) and the potential for varying composition and amounts of contaminants where the QC standards for auto gas are not at the same level as for aviation fuel.

The careful and frequent monitoring of our fuel systems which many of the list members swear by may very well be the best safeguard we have regarding fuel related safety issues.

There may be variables out there which are not normally on our radar screen. Just some food for thought.


Dave S

The referenced advisory rescinding auto gas approval applies only to S-LSA aircraft produced by Jabiru USA. We issued it because of growing evidence from our LSA fleet plus many reports from operators of amateur build aircraft of fuel system problems emanating from some of the additives or contaminants in auto gas. We've received many reports of a stringy mucus like substance precipitating out of the fuel solution that clog fuel filters and gum up carburetors. We've received reports of this happening in fiberglass tanks with sealants, plastic tanks without tank sealants, and even welded aluminum tanks with no sealants. This substance has been the suspected cause of at least one fatal crash. We've received no such reports from operators using Avgas 100LL. Searching through fuel test reports from gas stations across the country we find that a significant number of samples reported contaminants such as acetone, mek, toluene and other minor keytones plus the deliberately added components like ethanol, methanol, mtbe and tame. There is now good research that I could find on the effects of long term storage in fiberglass tanks. While our tanks are sealed with a product that is resistant to 10% ethanol there still seems to be a potential problem in every day use. I think that the effects of some of these additives and contaminants coming out of the solution (or suspension) with the fuel and settling to one area of a fuel tank in higher concentrations than expected is unknown and potentially quite damaging. While Jabiru Australia has had coupon samples of fiberglass coated with the sealant immersed in a gas - ethanol solution for nearly two years with no apparent damage to the sealant, there has not been a field study of E10 in a real tank exposed to moisture and condensation that may cause ethanol to combine with water and fall to the tank bottom in higher ethanol concentrations than expected. My advice to operators using auto fuel - either with or without ethaonol - is to keep a really close watch on their fuel systems. Carefully inspect fuel filters and carbs on a regular basis. =============================================