In the Winter 2011 issue of “The Flock”, Jabiru USA’s newsletter, owners of Jabiru airplanes were notified that previous approvals for autogas containing up to 10% ethanol have been rescinded:
Early in 2009, the fuel tank sealant for the J230-SP and J170-SP was changed to a formula that resisted up to 10% ethanol. Jabiru Aircraft PTY LTD of Australia issued Jabiru Service Letter JSL 007-3 to discuss fuel options in various engines and airframes. It stated that levels of ethanol of up to 10% were tested with no ill effects in airframe and engine, but that higher levels were not tested and should not be used.
Ethanol readily combines with water. As water enters the fuel system through condensation, this ethanol/water solution will settle to the bottom of a fuel tank. This causes pockets of ethanol that sit on the bottom of the wing tanks and header tank in concentrations much higher than 10%. As documented in JSL 007-3, ethanol concentrations higher than 10% have an unknown effect on the fuel tank sealant of Jabiru aircraft. In addition, as the ethanol precipitates out of the fuel solution, it takes away some of the octane rating of the fuel left behind. The remaining degraded fuel will ignite at a lower pressure than fresh 91 octane fuel, causing detonation damage in a high-compression engine such as the Jabiru.
Recently, a 2009 J230-SP that regularly burns auto fuel with 10% ethanol came in to Jabiru USA for repairs to damaged fuel tanks. It appears that a substance within the fuel has attacked the wing and header tank sealant and caused damage to the wings. Fuel testing lab personnel informed us that low levels of substances such as acetone, methanol and MEK may legally be present within any given automotive fuel sample. Acetone and MEK are both known to be destructive to the fuel tank sealant. In addition, many major fuel companies add their own proprietary additives, such as fuel injector cleaners, to the fuel. THESE ADDITIVES HAVE UNKNOWN EFFECTS ON THE FUEL TANK SEALANT, FIBERGLASS TANK AND WING STRUCTURES.
With all of this information in hand, Jabiru USA has no choice but to rescind its approval of fuels containing up to 10% ethanol. No amount of ethanol is to be used in any Jabiru aircraft. Use of ANY fuel other than 100LL is at the sole risk of the operator. Until the government mandates a pure, ethanol– and additive-free premium automotive or recreational fuel, we must recommend that only 100LL avgas be used in Jabiru aircraft. Operators who wish to continue using auto fuel without ethanol MUST make themselves aware of the risks involved with using auto fuel that may contain unknown substances. For more information, read JSA-N002, Fuel Grade Notification, available on our website, www.usjabiru.com/lsa-owner-info.html.
Just prior to posting this article, we learned from Nick Otterback of Arion Aircraft, a company closely associated with Jabiru, that they issued a similar warning to owners of their Lightning line of aircraft on pg. 10 of the December 2010 issue of their “Hangar Talk” newsletter.
Your bloggers commend Jabiru USA and Arion Aircraft for their proactive decisions to avoid any damage to its aircraft caused by ethanol’s presence in autogas. Note that this change in its recommendations does not apply to Jabiru engines in these aircraft, or aircraft from other manufacturers, but only to the companys’ airframes.
On the other side of the Atlantic, the renowned sailplane manufacturer Schempp-Hirth Flugzeugbau has just issued a similar warning concerning the use of ethanol-blends in the SOLO engines found in the company’s self-launching sailplanes.