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A Lycoming IO320 aircraft engine was run on different base fuels containing various percentages of methyl tertiary-butyl ether (MTBE). Vapor lock, vapor to liquid ratio (VLR), and Reid vapor pressure (RVP) tests were performed on the fuel mixtures to obtain a method that will provide a measure of the volatility of aircraft fuels for the purpose of aircraft certification. For the vapor lock runs the test fuel was heated to temperatures of 32, 38, 44, and 49 degrees Celsius (90, 100, 110 and 120 degrees Fahrenheit). A vapor lock run was performed for each combination of fuel mixture and tank temperature at fuel flow rates of 10, 20, 30, 40, 50 and 60 liters per hour. The quickest time to vapor lock was found to be at a fuel temperature of 44 degrees Celsius (110 degrees Fahrenheit) at takeoff power.

This paper addresses on going research that is being conducted by the FAA Technical Center on an unleaded replacement for 100LL aviation gasoline. Topics include preliminary results from performance studies, a survey of commonly found materials in aircraft fuel systems, lab tests which evaluated the effectiveness of several octane enhancers, engine oil analyses, and preliminary results from water contamination and fuel aging studies. The paper also discusses long term plans including: detonation surveys, flight tests, and octane rating of typical aircraft engines.