Determination of Minimum Fuel Octane Number Piston Aircraft Engines

The determination of the minimum fuel octane required for an aircraft engine, utilizes detonation equipment and test techniques developed prior to World War II. These procedures were designed to provide a 12% margin of safety on traditional leaded aviation fuels which met the lean and rich ratings as listed in the applicable ASTM specification. Now, due to a possible phase out of leaded fuels, it appears necessary for aircraft engine manufacturers and STC applicants to re-evaluate these techniques and procedures to determine if they are applicable for unleaded fuels. And to re-evaluate existing engines to determine the minimum acceptable requirements for a new unleaded aviation gasoline. This paper reviews these techniques and looks at possible requirements for an unleaded aviation gasoline.