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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.

The FAA Technical Center has evaluated straight methanol and ethanol fuels using an aircraft fuel system and engine which were installed on a dynamometer. The results of this program identified the conditions which should be used for hot fuel certification. Stoichiometric air-to-fuel ratios were identified as the most likely to result in either detonation or pre-ignition, and some material compatibility and operational problems were noted. The addition of small amounts of denaturing agents did not adversely affect the vapor lock behavior of the fuels. Straight methyl-tertiary-butyl ether was also evaluated. This material's high octane rating, moderate volatility, and relatively high energy density make it an attractive candidate when compared against either ethanol or methanol.