Waypoints: Toward an unleaded fuel

Shell Aviation’s December announcement that it is entering an unleaded avgas for FAA testing was perhaps the biggest general aviation news of 2013 (see “Briefing: Shell Offers Hope,” page 34). Shell joins Swift and GAMI in working to move a candidate fuel through a maze of tests to assure that whatever unleaded fuel or fuels we end up using do not harm our existing engines and aircraft—or the environment—and that there is a full understanding of any changes that must be made in the fleet to accommodate any shortcomings in a new fuel.

The FAA has said that it wants to introduce a new unleaded fuel by the end of 2018. In June 2013 it established a process to accept candidate fuels for testing. AOPA and other aviation associations were a part of the aviation rulemaking committee that developed the guidelines that outline how a fuel is considered.

The number one goal of the fuel is to eliminate lead. The 100-octane low-lead (100LL) avgas we use today is one of the last remaining fuels on the planet that uses lead. As a result, while the amount of lead emitted into the atmosphere from avgas is small, it is an ever increasing percentage of the lead entering the air—making general aviation an ever bigger target for the Environmental Protection Agency and environmental groups.

But the biggest reason to remove lead from our fuel is not environmental. It is economic. Only one company in the world continues to produce the lead component necessary for avgas. Others have dropped out because of the small market for the product and because of the potential environmental liability. Removing lead from avgas will allow it to be manufactured and shipped more conveniently without fear of contaminating other fuels.

GAMI and Swift have been talking about their unleaded fuel development projects for several years. They needed the publicity to build credibility and awareness, and in some cases to generate investment and garner technical expertise. Shell has been working on its own solution for nearly a decade, but without any public comment. As a giant global producer of 100LL, gasoline, and exotic racing fuels for decades, it needed no such investment nor outside expertise to experiment with various components until it found a formula that at least appears to meet most of the requirements for an aviation fuel, including the important 100 octane number.

Aircraft powered by engines with high-compression cylinders demand 100 octane—those are the same airplanes that burn the majority of the 100LL today; estimated to make up 20 percent of the fleet, they burn 80 percent of the fuel because they tend to be working and transportation airplanes. The lead additive in 100LL is there mostly to boost the base fuel’s octane rating to 100. The trick in developing a new fuel is to find a new octane booster that doesn’t contain lead and doesn’t change other fuel properties to the point that they aren’t compatible with the needs of aviation.

While Shell’s announcement was a surprise to many, it was clearly not a snap decision by the company. Some of the commenters on our initial online story about the announcement wondered whether it was merely a PR stunt by Shell. They also wondered whether Shell had really considered all of the parameters one must consider for an aviation fuel—its ability to make 100 octane; ability to prevent vapor lock at high altitudes; ability to provide the power needed when cold at extreme altitudes; compatibility with components in existing fuel systems; power-to-weight ratio; and ability to be produced at a reasonable cost, among many others.

As a longtime leader in the avgas market, Shell has taken all of that into consideration. Michael Sargeant, Shell’s avgas commercial aviation manager, said he expects the fuel will weigh about the same as 100LL and will cost about the same. It can be seamlessly mixed with 100LL during a transition. The company plans to proceed with FAA testing and to also seek a fleet-wide approval from the FAA—meaning that it could be approved for use in any airframe and engine combination where 100LL is used. The alternative is a lengthy and costly process of testing every possible engine and airframe combination.

Asked why the company waited until now to make its announcement, Sargeant said, “We wanted to be comfortable because we know the challenge of getting fleetwide accreditation is significant. We wanted to be comfortable that we had a formula that could go the distance. And we do now.”

Let’s hope his confidence is well placed and that regardless of who makes it, we end up with a fuel that is as close to a drop-in replacement as the one that Shell seems to believe it has developed.

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