State’s airports face unknowns in unleaded avgas transition

A fuel tank truck resupplying an airport with 94UL fuel
Refilling UL94 tank at South St. Paul Airport

The aviation industry and the FAA have established a goal of removing lead from aviation gasoline, or avgas, no later than 2030. While that’s more than five years out, Minnesota’s airports may feel the clock ticking. 

The most common type of avgas used and sold at general aviation (GA) airports is 100-octane low lead (100LL). Currently several companies are developing and testing 100-octane unleaded fuel alternatives, but only one has received approval (G100UL), and supply is limited. A 94-octane unleaded (UL94) fuel has been available since 2015 from manufacturer Swift Fuels. Currently two GA airports in Minnesota—Fleming Field–South St. Paul Municipal Airport and Stanton Airfield in Goodhue County—sell UL94 and 100LL. 

Many questions about the transition airports will need to make—from phasing out low-lead fuel sales and offering only unleaded avgas—remain: Will airports need additional fuel tanks? Can fuels be mixed? How will new fuels be supplied? And—perhaps most important—will funding be available to support the transition? 

Airport manager Andrew Wall of Fleming Field–South St. Paul Municipal Airport has been weighing these and other questions for some time. The airport has offered UL94 since 2018 alongside 100LL.

So far, the 100LL outsells the UL94 by a large margin, Wall says—something he attributes mostly to the price difference: UL94 is currently about $1.50 more per gallon. “Pilots want to find the least expensive way to operate,” he says. “I think [UL94] is a good product, it’s just not as widely used, and not as proven as the 100LL.”

To use UL94 in an aircraft engine, a pilot needs to obtain a supplemental type certificate (STC) from the fuel manufacturer. About two-thirds of the US GA piston fleet can use this fuel, while the remaining third consists of high-compression engines requiring a 100-octane fuel, according to industry sources. 

Like many products, the price of unleaded avgas is affected by the cost of producing and transporting it. The volume that the airport buys and the volume that is produced overall is much less than 100LL, Wall says. 

“We have to get buy-in from the refineries. But what I’m hearing is it’s still going to be a dollar or more per gallon [than LL]...I don’t think [unleaded] is going to take off until it’s the only option available, even if there’s an environmental benefit to doing so.” 

Wall also notes that there are different regulations—and added costs—when working with a product containing lead. “With lead you have to dedicate certain equipment to that only,” he says. That has implications not just for fuel storage on the airport but also for transport to the airport. 

Working closely with consultant SEH, South St. Paul is planning to upgrade and replace its fuel system and tanks over the next few years. The airport currently has three tanks: a 10,000-gallon tank for 100LL, a 6,000-gallon tank for UL94, and a 10,000-gallon tank for Jet A fuel. Wall says the project will require anticipating what types of fuel will be available and in use in the future and planning for the needed volumes of fuel, including delivery and storage. “Another thing to figure out is if we have 100LL in our new tank, what kind of cleaning requirements are we going to have to go through with our equipment?”

Funding will be another challenge. Historically the FAA hasn’t funded fuel system replacement but has funded moving one, Wall says.

Lindsay Reidt, senior engineer in airport planning and design with SEH, agrees. She expects South St. Paul’s project to cost over $1 million and to rely on state and local funding sources only.

SEH is working with the airport and agencies to coordinate funding opportunities and programming into the airport’s CIP. Once funding is available, SEH will help with grant applications and work on design and administering construction. Design will likely start in late 2024 or early 2025, with construction taking place in 2026. 

Another challenge will be managing the transition to UL availability and the interim during the switch—“meaning both storage of the fuel (the number of tanks available, split tank options) and pilot/user expectations and acceptance of the change,” Reidt says. 

From her observations, Minnesota GA airports are just starting to prepare for the transition. “It seems to be a slow progression and it hasn’t been flawless. There is a contradiction of information, which can make proceeding and acceptance challenging,” she says. She advises airports to take advantage of near-term projects to plan for the switch (such as split tanks for future diversification), and to plan now because of the life expectancy of fuel systems. “With a typical 30-year useful life, these projects don’t happen often, so it’s important to plan ahead,” she says. 

Wall encourages airports to tap into their relationships—with their FAA program manager, their MnDOT rep, and others in the industry. 

“Talk with other airports and find out what they’re doing,” he says, noting that both Stanton, Minnesota, and New Richmond, Wisconsin, have experience with unleaded fuel. 

“And talk with your fuel suppliers and see what they know. They might have different information than you do, when it comes to where refineries are at [with the transition],” Wall says. Before they brought UL94 to their airport, Wall says they hosted a Swift Fuel representative to learn more. Wall also asked the airport’s users if they would try UL94. 

“Sign up for updates from the FAA. Keep your finger on the pulse of what’s going on...Talk to other managers and pilots,” Wall advises. Currently, much of the local airport industry’s focus is on PFAS cleanup, “but I think UL will come to the surface soon,” he says. “The ball is already rolling...It’s going to happen eventually, but there are still a lot of unknowns.”

­­—Amy Friebe is the Briefings editor.


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