Moving Forward on Unleaded Fuels

August 30, 2018 — Marking progress toward finding a safe, effective, high-octane unleaded fuel for the general aviation fleet was among the highlights this week as EAA participated in the Piston Aviation Fuel Initiative (PAFI) steering group meeting in Frederick, Maryland. The collaborative FAA/industry effort includes a broad spectrum of aircraft and engine manufacturers, fuel companies, and aviation groups.

The PAFI test program was initially scheduled to be completed by the end of 2018. After rigorous engine and flight testing on the best of the fuels developed by the petroleum industry, that deadline was extended so fuel developers could potentially mitigate the challenges that emerged under the consensus test protocols.

The two candidate fuels that passed initial PAFI screening of the original 18, one each from Shell and Swift Fuels, have been under evaluation in PAFI Phase I and Phase II testing over the past several years. Each of those two fuels displayed challenges or adverse findings uncovered during  the test program. Shell has since worked to optimize its fuel within the bounds of its original specification in a way that, based on preliminary data, is believed to mitigate those  issues and concerns. PAFI plans to resume engine testing on the optimized Shell fuel this fall, with flight testing likely to resume once the engine testing proceeds successfully.

Swift, meanwhile, announced that it was abandoning work on its original fuel and would withdraw from further participation to concentrate on an entirely different fuel, which would not be eligible for continued testing under the original PAFI competitive process.

“Developing a comprehensive transition to an unleaded fuel for general aviation is extremely complicated and has proven to be a significant technological challenge, which is why a broad cross-industry coalition such as PAFI is essential to result in a viable fuel being broadly accepted and adopted for the GA fleet,” said Doug Macnair, EAA’s vice president of government affairs, who has been representing EAA in the PAFI process. “We’ve learned a tremendous amount already. It is not only the fuel’s chemical composition that must be successful — it is how that fuel works in various GA engines and airframes, how it works in a wide range of conditions including the most strenuous applications, and how it can be produced and distributed in a cost-effective manner that is part of this process. There is a misperception that this is an FAA program to develop unleaded fuels, when in fact the FAA is, at our request, assisting the aviation industry and petroleum industry to collaboratively determine the best means of evaluating candidate fuels and providing necessary resources to help conduct the actual testing.”

The PAFI program does have some urgency for timely completion, as the Environmental Protection Agency has been contemplating an “endangerment finding” on the lead in 100LL, which pushes the federal government toward eventual regulatory action to phase out leaded avgas. The FAA has strongly maintained that any future EPA regulatory actions must be coordinated so as not to disrupt general aviation safety and commerce. There is currently no specific deadline for an EPA endangerment finding but the long-term availability of lead is always a concern as leaded gasoline and other products are phased out worldwide.

“The imperative is to effect an orderly transition to an unleaded fuel on our collective terms and to ensure that fuels are developed that have been fully vetted and tested to the satisfaction of the aviation and petroleum industries,” Macnair said. “Worst-case scenarios that could occur, without PAFI or a similar orderly evaluation and transition, might involve individual states creating their own regulations or prohibitions on leaded fuels or fuels endeavoring to enter the marketplace that have not undergone the necessary testing by airframe and engine manufacturers and aviation fuel experts.”

The FAA and aviation industry are interested in investigating all alternatives, including evaluating high-octane unleaded fuels that have been developed in the years since the PAFI program was initiated. The FAA welcomes fuel producers currently developing high-octane unleaded fuels to bring their data to the FAA for evaluation and consideration of possible initial screening at the FAA's William J. Hughes Technical Center. Fuel producers offering alternatives determined to have potential viability as an unleaded replacement for 100LL will be invited to participate in a Cooperative Research and Development Agreement with the FAA, which will be conducted on a non-interference basis with the existing PAFI test program.

Some fuel developers have been working outside the PAFI program, aiming toward using the STC method for approving their fuels. Macnair noted that EAA is very familiar with the STC route, having led the way for auto-fuel STCs in aircraft more than 35 years ago for certain types of aircraft and engines. He added that the STC method is a slow, arduous one, as any fuel must be individually approved on an engine and airframe make and model basis or with compelling evidence of substantial similarity. While this path is difficult, EAA and the FAA support all fuel development efforts both in and out of the PAFI test program. There is, however, a broad consensus in the aviation and petroleum industries that fuel testing should follow standardized PAFI protocols to ensure transparency, compatibility, commercial viability, and safe operation.

“An important element of the PAFI process is that it uniquely blazes a path toward an authorization for the GA fleet, or a broadly significant part of that fleet, instead of working on one aircraft model or range at a time,” Macnair said. “The PAFI testing and evaluation program is a transparent, industry developed, and standardized method to determine the viability of what we all want: A safe, widely available unleaded fuel for the broadest possible spectrum of the GA fleet. We are pleased that Shell continues to invest heavily in the development and maturation of its fuel and look forward to welcoming other fuel developers as they bring their concepts forward for evaluation.”