Getting to the finish line

Avgas transition requires transparency, data, and one fuel

Pilots, aircraft owners, airports, fuel developers, and regulators all share the same objective: eliminate lead from aviation gasoline without compromising safety, reliability, and affordability.

While fuel developers have made significant progress, there remains much more testing and evaluation to be done to meet the FAA and industry goal, as well as the EPA endangerment finding, calling for phasing out leaded avgas by 2030.

The FAA is the sole entity responsible for approving fuels for use in airframes and aircraft engines. The agency has two recognized pathways for bringing unleaded fuels to market. The first is the supplemental type certificate (STC) process, which allows an applicant to demonstrate to the FAA that its fuel can be safely used in approved aircraft and engines. The second is the Piston Aviation Fuels Initiative (PAFI), involving the FAA and technical experts, to evaluate candidate fuels through a common testing and approval process. Each pathway has advantages, but both exist for one reason—to ensure that safety decisions are based on sound engineering and rigorous data.

The industry also benefits from multiple fuel developers pursuing solutions. Companies including General Aviation Modifications Inc. (GAMI), LyondellBasell/VP Racing Fuels, and Swift Fuels have invested substantial resources in developing unleaded alternatives.

Competition encourages innovation, and every developer must receive a fair, transparent, and technically consistent evaluation. Any decision or approval must be based on data and not anecdotal information, perceptions, personalities, or politics. Transparency is therefore not simply desirable, it is essential. Testing information and a comparative analysis must be readily available and understandable not only to fuel engineers but to producers, suppliers, distributors, and users. Knowing precisely where we are, a real-time side-by-side dashboard comes to mind, of the testing and status of candidate fuels is needed. This transparency will help squelch the blog echo chambers and the keyboard warriors who often do not have the data to make factual comments. EAGLE—a joint government-industry initiative that AOPA is a member of—has started this process, but more can be done. And if you would like to read the FAA’s transition plan, you can find it on the EAGLE website at flyeagle.org.

Aircraft owners, airport operators, mechanics, manufacturers, and pilots deserve to understand how decisions are made. These technical findings should be shared whenever possible. Aviation has always been a data-driven industry. Whether certifying an aircraft, approving an engine, or developing a maintenance procedure, engineering data—not opinions—has been the foundation of every major safety decision. The transition to unleaded avgas should be no different.

The FAA is conducting additional fuel performance engine testing to determine what if any limitations the candidate fuels reveal. Further materials compatibility testing will evaluate seals, fuel bladders, hoses, gaskets, coatings, and other fuel system components that may react differently to new fuel chemistries.

Another technical issue deserving a spotlight is fuel comingling. We cannot have a scenario where an aircraft takes on one FAA approved fuel and then lands at an airport that does not have the same fuel available. If multiple unleaded fuels cannot safely mix with one another—or if they produce uncertain performance characteristics when blended—the operational consequences could be significant. Compatibility among fuels is therefore vital to operational safety. Currently, the FAA’s transition plan calls on the market to decide which fuel(s) end up being widely distributed. Given the safety implications, it may instead make sense for the FAA, the agency that approves fuels for aircraft, to make the decision on what unleaded fuel is ultimately used by the whole fleet.

Another issue that is receiving attention is the potential for engine modifications, especially high compression engines. Other than the STC approved GAMI fuel, do the other candidate fuels have a high enough motor octane number to perform equivalent to 100LL without modification? One of GA’s greatest strengths is its extraordinarily diverse fleet, with many aircraft remaining in service for 50 years or more. Requiring engine modifications, hardware changes, or costly retrofits for thousands of aircraft would dramatically increase costs while slowing adoption. The ideal unleaded replacement fuel would hopefully require little or no modification across the existing spark-ignition piston fleet, identify and resolve any materials compatibility issues, resulting in the greater likelihood of a successful transition.

Through the STC pathway, the FAA has approved GAMI’s G100UL unleaded fuel for all spark-ignition engines and in all fixed-wing airframes. Swift recently expanded its 100R STC to additional engines and airframes and has now entered the FAA’s Piston Aviation Fuels Initiative (PAFI), while VP Racing/LyondellBasell’s UL100E is making progress through PAFI and test results for their fuel are also available on the EAGLE website.

Progress by all three developers reflects the commitment to a fleet-wide solution. All three fuel developers presented their respective updates at AirVenture this year and AOPA reported on each of them.

The ASTM International industry consensus standards process will also continue to play a critical role. All three fuels are going through the ASTM process.

The FAA and industry must confront a practical reality. The GA fuel market is simply too small to support multiple high-octane aviation gasolines, especially if they cannot comingle. It is interesting to note; the amount of avgas burned in one year is equivalent to the amount of automotive fuel used in less than half a day. And most airports, particularly smaller community airports that make up the backbone of the national airport system, lack the infrastructure and financial resources to store and dispense several premium aviation fuels.

From both a safety and economic standpoint, a single approved and accepted unleaded fuel specification that can be produced, widely distributed, stored, and that reliably serves the entire spark-ignition piston engine fleet could be the final outcome. An option could be developing criteria based on data and transparency. This would lead to simplifying operations, eliminating concerns about cross-fueling, reduce infrastructure costs, and provide the confidence that a fuel will be widely available.

At the end of the day, transitioning to an unleaded fuel for every engine and airframe in the GA fleet by 2030 is a laudable goal. It will take fuel developers, the FAA, and the entire GA community to remain committed to full transparency, objective science, data, and building the confidence in a fuel that pilots and aircraft owners need and deserve.

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