The “Experimental Clean Combustor Program” is a contract effort with primary objectives including the generation and demonstration of technology for development of advanced commercial CTOL aircraft engines with lower exhaust emissions than current aircraft, and the demonstration of this technology in full scale engines in 1976. The program is being conducted in three phases. These consist of screening of low pollutant combustors, refinement of the best combustors and engine demonstration of the best combustors. The combustor screening phase was initiated in December 1972 and is currently in progress. Contracts were awarded to Pratt & Whitney Aircraft and the General Electric Company to evolve combustors for the JT-9D and the CF6-50 engines respectively. Pollution goals are emission index values of 20 and 4 for carbon monoxide and unburned hydrocarbons respectively at engine idle conditions, and an oxides of nitrogen emission index level of 10 at engine takeoff conditions. Pollution reduction approaches which are being investigated include multiple burning zone combustors, investigations of improved fuel distribution and preparation and the staging of combustor airflow.