The FAA's approach and engagement on unleaded avgas

January 25, 2011

How do two powerful federal regulators, the EPA and FAA, approach the transition of the general aviation piston fleet to unleaded avgas? To put it simply, the EPA is responsible for what comes out of the exhaust stack; the FAA is responsible for what goes into the fuel tank. And like two engines on a twin, they have to be in sync or the aircraft is headed for trouble. The good news: The EPA and FAA are in sync.

Most of the early action in the process has been with the EPA—responding to a petition from the environmental group, Friends of the Earth, to review the environmental effects of leaded avgas. However, in 2011 and beyond, the FAA will take on a more visible role in a process to ensure the safety, performance, and practicality of an unleaded replacement for 100LL. According to the FAA, here is how the two agencies work in tandem:

The Clean Air Act requires that EPA consult with FAA when issuing proposed emission standards for aircraft, and EPA is prohibited from issuing those regulations if that consultation reveals an adverse impact on safety or noise. On the other hand, FAA may prescribe standards for aviation fuel, but only if EPA determines that aircraft emissions from the fuel endanger public health.

The FAA has invested resources to support research for unleaded alternate fuels at the William J. Hughes Technical Center in Atlantic City, N.J. The FAA's Engine and Propeller Directorate is also closely involved and in regular direct communication with the GA Avgas Coalition, individual aircraft and engine manufacturers, the petroleum industry, and new fuel producers. According to the FAA, “Aviation fuel is certified by FAA as an operating limitation of both the aircraft and the engine. If a new fuel can be developed that falls within the existing aviation fuel operating limitations of the legacy fleet of aircraft, then FAA approval is easy. … The operating limitations must be defined in a manner that ensures that the fuel is controlled to the extent necessary for safe operation. An alternative fuel specification is acceptable as long as it provides the necessary level of control of the fuel composition and properties.” This defines the long-term process.

In the near term, and as an interim step, the FAA, at the request of the GA Avgas Coalition, is now evaluating very-low-lead fuel that could be incorporated into the existing avgas production and supply chain without the need for engine modifications or re-certification. This is seen as a short-term initiative to address the EPA's new National Ambient Air Quality Standards and not as a long-term solution.

But the long-term process to assess potential unleaded fuel solutions will go forward and will be accomplished with an industry consensus-based fuel specification, such as those written by ASTM International. ASTM International, originally known as the American Society for Testing and Materials, is an organization that develops standards and specifications for many industrial and engineering products, including aviation fuels. Within the ASTM process, the FAA has noted the particular progress of two leading unleaded fuel developers, General Aviation Modifications Inc. (GAMI) and Swift Enterprises. The FAA outlined the two companies’ progress in a backgrounder:

  • GAMI has requested an ASTM specification approval for its unleaded fuel and requested a supplemental type certificate (STC) approval for use of its G100UL fuel on Teledyne Continental Motors IO-550-N engines that are modified with a turbonormalizer. “While the STC approval will be limited to the IO-550-N engine installed in the Cirrus SR22 airplane, it is expected that the ASTM specification will have broader applicability,” the FAA explained. GAMI plans to work with the FAA to develop a detailed compliance plan for the G100UL fuel.
  • Swift Enterprises has also been developing an unleaded high octane aviation gasoline designed to meet or exceed the operational parameters of conventional, leaded aviation gasoline. “Through industry consensus and direction, Swift has developed a test specification for their fuel, called UL102, and has generated the necessary research and development data over these last five years to support that specification. Swift is currently in the final stages of balloting the test specification and supporting data to the ASTM International membership for final approval and issuance,” the FAA said.

In addition, the FAA is focusing significant resources on developing an alternative to this consensus-based ASTM process that would support FAA approval of an aviation fuel operating limitation using a compliance method that provides an equivalent level of safety to the ASTM process. Such a compliance concept would be predicated on compositional control of the fuel and would require a rigorous evaluation of the fuel performance, the FAA said.

AOPA ePilot special reports on avgas will continue to track and report on progress made by the FAA, the EPA, ASTM, and companies involved in developing a new unleaded avgas solution for the entire GA fleet.