The Sunset of 100LL Fuel

With the ongoing clash between Santa Clara County and Reid-Hillview airport dominating public discussion leaded fuels (100 Low-Lead, or 100LL), it can be difficult to sort out the issues that underlie the transition from leaded to unleaded avgas. In our conversations with airports and pilots, we’ve had the chance to hear about the different challenges in transitioning to safer, cleaner fuel. In many ways Reid-Hillview has been a case study for the transition from leaded to unleaded fuels—and the challenges and benefits that may ensue.

What’s Happening at Reid-Hillview?

In short, Santa Clara County officials banned the sale of 100LL fuel at both Reid-Hillview (RHV) and San Martin (E16) airport. Deliberations over this step first surfaced in 2018, and the county finalized the decision In August 2021, setting a deadline of December 31, 2021 for the full-stop of leaded avgas sales.

In the wake of this ban, groups like the Avgas Coalition, AOPA, and tenants at Reid-Hillview have alleged that the decision by the county is one of a string of violations of FAA Grant Assurances, and is a matter of both safety and discrimination. The FAA has opened an investigation that includes the ban among other violations as a reason for its review.

A History of Tension

Since the late 1990s, Santa Clara County and airport staff have been at odds. In 1959, the county was encouraged by the City of San Jose to purchase and operate the airport. Santa Clara then purchased Reid-Hillview in 1961. Over the years, the County continued to expand the airport, purchase lang, and receive Federal grants to operate and develop the airport.

From the 60s through 1990, the City of San Jose and Santa Clara County focused on developing the airport, adding a runway, hangars, parking, and other updates. In 1990, however, the City of San Jose repealed their previous resolutions, Resolution 16115 (1959) and Resolution 38741 (1970). Over the next six years, investigation into the environmental impact of RHV would take the focus, with the airport examining in a 1996 report, potential outcomes of closing the airport, relocating it, or continuing to operate it. The airport remained open by a 3-2 vote, and the next decade saw continued expansion by the airport, including initiatives to improve quality of life for residences surrounding the airport, such as noise insulation, noise monitoring, and additional fencing.

In the 2010s, however, tension again began to grow as the Board of Supervisors determined how to respond to the EPA’s 2008 revision to national ambient air quality standards (NAAQS). The community continued to voice frustrations with the airport: including pollution, noise, traffic, lead exposure, and a housing shortage that had many eyeing the airport’s acreage.

In 2018, airport staff presented their Business Plan to the Board of Supervisors. The board reviewed the plan and adopted motions to discontinue Airport Improvement Program grants and rely on the General Fund for improvements and maintenance. The Supervisors chose to discontinue these grants because they were unsure whether the airport would continue to operate past 2031, the current expiration date of RHV’s Grant Assurances.

The motion also instructed airport staff and the Board to work with the City of San Jose on possible alternative uses for the airport land after 2031, explore relocating many operations at RHV to E16, begin process of analyzing the impact of airborne lead, and work with local tenants on the feasibility of allowing only unleaded aviation fuel at RHV and E16.

Supervisors passed the motions 3-2, based on a number of concerns. Supervisor Ken Yeager cited the lead toxicity to residents, while County Executive Jeff Smith voiced worries about the airport’s financial viability, given that the airport was $6 million in debt, and would need another $6 million in loans to make much-needed capital improvements.

This meeting, marked by three hours of public speakers and a presentation from airport staff, would be the tipping point in the fraught relationship between the airport, the county, and the community.

In 2020, Santa Clara County affirmed its decision not to accept new grants. The Board of Supervisors announced in a 4-1 vote plans to prepare for a possible closure of RHV. RHV’s fate was still in the realm of “potential” closure, but to supporters of the airport, the message was clear: Reid-Hillview would not remain open past 2031.

How Has the Aviation Community Reacted?

The waters of community reaction are muddied by several details.

First: the FAA investigation is investigating numerous complaints beyond the ban, particularly the County Airports Administration’s refusal to offer long-term leases, a refusal to renew certain leases, and security concerns such as: weed abatement, refusal to deal with the risk of goose-related bird strikes, poor upkeep of airfield signage, and unauthorized airfield access by drivers.

Second: A significant amount of tenant backlash has been due to interference by the county, which they feel has not demonstrated sufficient understanding of airport operations. A major argument against the ban is the swift timeline. Giving less than six months for the airport to transition from one fuel to another feels like an overnight change to the FBOs, businesses, and other tenants. Already frustrated with their county, the 100LL ban was primed to be a breaking point between the airport and the Santa Clara County Airports Administration.

Lastly: the GA community has a number of places where informal discussions take place. In online spaces, some pilots have voiced suspicions that the county instituted the ban as an indirect method of shutting down the airport, so that the land could be sold for non-aeronautical development. Airport users wonder whether the quick timeline of the ban sets the airport up to fail. This rumor cannot be confirmed, but it presents the ban as not a good-faith effort to improve public health, but a self-serving attempt to force an early closure to free up land for sale. With the county already having plans to close the airport in 2031, the idea of early closure only aggravates an already sensitive topic.

All of this has whipped up frustration and tension surrounding the ban, as well as a fear of chain reaction closures at other GA airports.

How has the Santa Clara Community Reacted?

Time and again, airports see conflict with their surrounding communities. Between noise complaints, pollution, and safety hazards, tensions can rise unexpectedly, with devastating results. When it comes to the health and safety of local children, it’s hard to deny that the people of Santa Clara deserve answers and initiative by the airport to reduce this risk.

Studies have found that children who live in neighborhoods near Reid-Hillview experience increases in lead levels that even surpass that of children in Flint, MI, which has become notorious for its dangerous lead levels. Of 17,000 blood samples, collected from 2011 to 2020, those who lived within half a mile of RHV had elevated blood-lead levels.

Reid-Hillview also exceeds the EPA NAAQS for airborne lead emissions. There are numerous recreational areas within the critical danger zone, including a Boy’s and Girl’s club, a pre-school, and a city park. The community wants to find a way to reduce the dangers to the children of Santa Clara County, and the ban, while contentious, is one way of doing so.

However, this isn’t the first clash between residents of Santa Clara County and the airport. East Side residents have advocated for the airport’s closure since 2018, with San Jose council women Magdalena Carrasco, Maya Esparza, and Sylvia Arena leading the conversation on lead exposure. When the airport was first purchased from original owners Bob and Cecil Reid in 1961, residents of San Jose were firmly against the airport’s expansion, but the local government chose to move ahead with plans for a single-run-way airstrip. Since then, the airport has increased to 200 acres added a terminal, more hangars, and a second runway. All of this serves to create resentment in the community, as they feel the airport has received more consideration than those who live in the surrounding neighborhoods. Many residents of East Side have noted that they would be glad to see the airport closed, and the land used to serve the community. Most tenants at the airport do not reside near RHV, which only further emphasizes the disconnect between East Side residents and airport tenants.

But other residents feel that the county is not thinking the problem through. Reid-Hillview is obligated by federal grants to remain open until 2031. Instead of banning 100LL and closing the airport nine years later for failing to follow through, some feel that the county would do better to actively bring in unleaded fuel for pilots and push for its use. Transitioning over a year or two to unleaded fuel and keeping the airport open might be a smarter use of policy, especially considering that rezoning the land might require replacing hundreds of acres of topsoil, should the lead contamination have spread into the ground.

Many residents don’t have a strong opinion on how the county should go about reducing lead exposure, but they have voiced support for the airport. Locals have enjoyed visiting the airport during community events, and others worry about the impact on fire management if the airport is shuttered.

The Argument for Leaded Gas

Efforts to eliminate leaded automobile gas in the 1970s resulted in the successful introduction of engines manufactured for unleaded fuel. However, piston-driven aircraft have yet to transition to high-octane, unleaded fuels and comprise the largest producer of airborne lead in the United States.

Today, many arguments to prolong the use of 100LL surrounds the importance of piston-engine aircraft for purposes like search and rescue, fire prevention, and situations in which the pilots will have to contend with unsteady conditions.

At Reid-Hillview, opponents of the ban argue that eliminating a place for piston engine aircraft to refuel could ground a significant portion of this fleet. Additionally, misfuelling can cause detonation or engine malfunctions, putting pilots of piston-engine aircraft at risk.

More frustrating, is that drop-in fuel replacements can be difficult to find. Since GAMI received limited STC approval in 2021, the number of airports offering unleaded fuel has increased, but worries about being unable to find fuel drive the desire for a longer transition period.

Arguments for Unleaded

Many owners of piston aircraft, including Jason Jeffery, owner of a flight school in Long Beach, are open to transitioning to unleaded avgas as soon as it can be made available. On his, and other pilots’ minds is price and the possibility of having to replace their engines.

Commercially viable unleaded avgas is far from a pipe dream at this point. Two contenders, General Aviation Modifications Inc. (GAMI) and Swift Fuels, offer unleaded fuel at a high enough octane to support many aircraft. As GAMI and Swift continue to develop and test their fuels, confidence in the transition is bound to increase.

Swift Fuels has received supplemental type certificates (STCs) for its UL94 unleaded fuel product covering 33 Lycoming engines (up to the AEIC-540-D) and 24 Continental engines (up to the TSIO-550-K). While these STCs do not cover all piston aircraft, only those with an engine/airframe rating of min 94 octane or lower, UL94 can safely commingle with 100LL in the tanks of those aircraft. Additionally, Swift is working on a 100-octane unleaded fuel, and estimates that, once it is approved by the FAA, it will be drop-in ready for roughly 85% of the piston fleet. Swift 100R is currently undergoing FAA Certification testing and ASTM fuel specifications. As a bonus, UL94 is cheaper than 100LL at most airports that offer it.

General Aviation Modifications Inc. (GAMI) has also developed a drop-in, high-octane, 100LL fuel replacement, G100UL. The FAA has approved over 611 engines to use G100UL, and GAMI anticipates that G100UL will be approved by the FAA by the second quarter of this year. George Braly, GAMI’s chief engineer, also reports that G100UL is fit for big-block engines and has requested FAA approval for “every spark-ignition engine and every airframe powered by those engines.” This approval would include many additional makes and models of popular engines fleetwide.

Equally important, however, are safety concerns for pilots themselves. Residents of areas surrounding airports are at risk of lead poisoning, and pilots, who are handling the fuel directly, working on-site, and spending time in their aircraft, are also at a significant risk. The Colorado State Patrol owns and operates just five piston aircraft, but several workers and a child who spent time in the repair shop all had elevated levels of lead, according to results from an OSHA inspection. Pilots deserve to be able to fly without risking their health, particularly those pilots who are tasked with the life-saving humanitarian flights that are often reliant on piston engines.

What’s next?

On March 17th, 2022, a broad array of stakeholders under the Eliminate Aviation Gasoline Lead Emissions (EAGLE) banner met in Washington, D.C., to chart the path to eliminate lead base fuels by 2030. EAGLE comprises a comprehensive public-private partnership to expand and accelerate government and industry actions and investments to establish the policies and activities to permit new and existing GA aircraft to operate lead-free without compromising safety or economic health.

Competitive pricing of unleaded fuels and reduced aircraft maintenance are a bonus to aircraft owners, but the transition must be mindful of the fact that over 200,000 aircraft require the use of high-octane fuels that contain lead. The EAGLE initiative requires assurances that 100LL avgas remains available and in place until an unleaded solution is developed and deployed at airports nationwide. With access and approval for G100UL, UL94, and SR100 on the rise, a transition to unleaded fuel is becoming increasingly viable and must be on the radar for airport managers and their local government partners.

As airports and FBOs make decisions about how and when to transition from leaded to unleaded, it is clear that increasing access to safer, cleaner fuel brings a multitude of benefits to pilots, the fuel industry, and communities surrounding airports. The Reid-Hillview vs. Santa Clara County conflict has obscured the conversation about the long-term trajectory of fueling. It seems to pit the community victims of lead poisoning against pilots and aircraft owners, when the reality is that all would benefit from widespread availability and compatibility of unleaded fuel.

Nationwide distribution and availability would ensure that pilots could have more confidence that the high-octane, unleaded fuel required is available wherever the destination. The health benefits for communities surrounding GA airports and the pilots who work with the toxic fuel cannot be overstated. Minimizing lead exposure is a vital public health goal, and transitioning the piston fleet would be a significant victory.


Next steps for airport operators, FBOs, and pilots should be to keep watch fuel testing and the FAA. As research evolves and the number of piston-driven aircraft that can accept unleaded fuels continues to grow, the distribution networks will expand, and demand for unleaded fuels will increase. Over the next decade, the FAA, industry leaders, and community members can all be a part of transitioning to safer, cleaner avgas, eventually making lead-based aviation fuel—and the associated health risks—a thing of the past.