FAA is beginning evaluations of proposals to replace leaded aviation gasoline, in a move that marks the next step toward transitioning to a new unleaded fuel by 2018.

FAA a year ago asked fuel producers to submit proposals by July 1 for possible options to transition to an unleaded fuel. The agency said it received 10 replacement fuel proposals from producers Afton Chemical Company, Avgas LLC, Shell, Swift Fuels and a consortium of BP, TOTAL and Hjelmco.

The proposals will be evaluated through the industry-government Piston Aviation Fuels Initiative (PAFI). FAA will assess the viability of the fuels and then select suppliers to participate in phase-one testing at the agency’s William J. Hughes Technical Center in Atlantic City, New Jersey.

Under that phase, suppliers will submit 100 gal. of their candidate fuels for initial testing. Following initial testing, FAA plans to narrow the candidates to one or two fuels that would take part in phase-two testing on engines and aircraft. Providers of those fuels would be asked to submit 10,000 gal. for testing.

Transportation Secretary Anthony Foxx stressed that the department is committed to the transition from leaded fuel. "This work will benefit the environment and provide a safe and available fuel for our general aviation community," Foxx says.

Congress set aside $6 million for PAFI in fiscal 2014 to support the fuel testing. PAFI participants are hoping to foster development of an unleaded fuel "with the least impact on the existing piston-engine aircraft fleet," FAA says.

Industry groups note that the evaluations not only must look at impact on aircraft, but also on production and distribution infrastructure and the environment. Also to be evaluated is costs of aircraft operation.

"Aviation organizations, the petroleum industry and the FAA are working collaboratively to ensure the aviation community will have access to unleaded fuel that meets performance and safety standards, is affordable and can be used by the existing fleet with minimal disruption," says Aircraft Owners and Pilots Association President Mark Baker.

Experimental Aircraft Association Chairman Jack Pelton calls that collaboration "key to finding and transitioning to the most viable unleaded fuel for the greatest possible range of general aviation fleet that currently relies on 100 low-lead avgas."

FAA estimates that 167,000 general aviation aircraft in the U.S. rely on 100 ll avgas. Avgas, the sole remaining transportation fuel in the U.S. that contains lead, has become a target of environmental groups that have filed petitions with EPA and lawsuits to speed up the transition to unleaded fuels.