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The path to an unleaded high octane grade Avgas

17 August 2010

The presentation "The Path To An Unleaded UL Avgas" was given at the recent 2010 EAA AirVenture event in Oshkosh, Wisconsin by Mr Cesar Gonzalez. 

Mr Gonzalez with decades of experience from Cessna is considered the most recognized expert in the world in this field.


Hjelmco Oil is glad to share this presentation with the authorization of the Experimental Aircraft Association.

The PDF-file can be downloaded from the upper right hand corner.


In the 1990's and early 2000's Cessna performed extensive ground and flight testing of alternative fuels. To support these activities Cessna developed a patented FAA approved Engine Detonation Indication System, developed a Baseline 100LL Test Avgas and established ground/flight test procedures that overcome dynamometer fuel test limitations.


Cessna investigations yielded successful 100LL/ETBE blends that significantly reduced the TEL (lead) requirements to levels unattainable by traditional Avgas hydrocarbon blends. Further development of totally unleaded ETBE blended fuels could satisfy the most demanding engines flying today with modest or no modifications.


The ULL (Ultra Low Lead) approach simply blends two fully substantiated aviation fuel components and preserves, for the time being, the continued production of leaded 100LL Avgas as a component, while introducing an ASTM (D7618) aviation approved ETBE component with characteristics  explored by Cessna during 1997 to 2002. The attached presentation defines further test activities, procedures and equipment for the approval of the ETBE blended fuels.


Phase 1 of the ETBE blended ULL Avgas program begins the transition from the TEL additive produced by a single remaining supplier in the world, to the  ETBE component (the oxygenate of choice) currently produced in massive and growing quantities by 17 countries, including the United States.


Phase 2 completes the transition from the TEL (Lead) additive to the ASTM approved ETBE component, and as pointed out on page 15 of the Forum presentation, other independent unleaded products should be included in these fuel evaluation efforts. Incidentally, the growing popularity of ETBE as an automotive fuel component provides evidence that economics is not an issue on aviation applications.


However, success and confidence in the development of 100LL Avgas replacements demand a serious review of a) fuel evaluation/validation procedures and equipment cited on pages 20, 21 and 22, and b) institutional issues covered on pages 23 and 24 of the attached Forum presentation.


Distribution authorized by the Experimental Aircraft Association.

Cesar Gonzalez - Aviation Consultant




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