In a Service Letter issued May 18, Cessna issued a strong warning against the use of ethanol in fuels powering its aircraft. Titled “Ethanol-based fuel not approved for use in Cessna airplanes,” this Service Letter documents Cessna’s exhaustive testing of AGE-85, an 85% ethanol blend that has been championed in recent years by South Dakota State University and others.
Cessna lists a number of serious consequences when using fuels containing ethanol:
- To match detonation characteristics at high power settings, the utilization of ethanol-based fuels requires fuel flow volume increases of nearly 40% as compared to 100LL fuel. This means that the current published airplane performance information is not accurate when using ethanol-based fuels.
- Ethanol-based fuels are not compatible with some fuel system components, causing extreme corrosion of ferrous components, the formation of salt deposits, jelly-like deposits on fuel strainer screens, and internal separation of portions of rubber fuel tanks.
- The use of ethanol-based fuels can negatively affect electric fuel pumps by increasing internal wear and causing undesirable spark generation.
- AGE-85 is not compatible with some fuel quantity gauging systems and may cause erroneous fuel
- AGE-85 is capable of dissolving large amounts of water at conditions down to minus 77ºF,
impeding the detection and removal of water from the fuel system.
- AGE-85 may block fuel filter, affecting fuel flow.
- AGE-85 experiences heavy evaporation losses.
Cessna’s document also issues this warning: These tests and evaluations also suggest that operational safety may be compromised by the use of ethanol-based fuels.
From discussions your bloggers have had with an official involved in these tests, Cessna’s recommends against the use of any levels of ethanol in fuels used in its aircraft, not only AGE-85. Its conclusions are in stark contrast to claims made by AGE-85 proponents, for instance at the American Coalition for Ethanol or at e85Tips.
The GAfuels Blog is written by three private pilots concerned about the future availability of fuels for piston-engine aircraft. They are:
- Dean Billing (Sisters, Ore.) – an expert on autogas and ethanol
- Kent Misegades (Cary, N.C.) – an aerospace engineer and aviation journalist
- Todd Petersen (Minden, Neb.) – former aerial applicator and owner of more than 150 Mogas STCs for aircraft
For a list of airports that have ethanol-free fuel and those no longer pumping it, compiled by the authors, follow this link.