The Push to Ban 100LL Aviation Fuel: What it Means for Aerial Mapping

Author: Mike Dauer, Account Manager, AeroTech Mapping

Efforts to ban 100 octane Low Lead (100LL) aviation fuel, commonly used in piston-engine aircraft, are gaining momentum across the U.S. This leaded fuel, which powers a significant portion of the general aviation fleet in the U.S., has become the target of regulators and environmental advocates. Several states and local governments have already implemented bans on the sale of leaded aviation fuel, including Santa Clara County, California which banned 100LL sales at local airports such as Ried-Hillview in 2022. On a larger scale, Washington State is considering legislation (H.B. 1554) to phase out 100LL by 2030​. These efforts have prompted significant pushback from aviation industry stakeholders, including the Aircraft Owners and Pilots Association (AOPA), which argues that banning 100LL without an accessible replacement could ground an estimated 167,000 aircraft with piston-engine aircraft that rely on 100LL for safe operation (including those most commonly used for aerial mapping).  In this article, we’ll discuss why this is happening, what the current proposals are, issues with the proposals, and potential solutions.

Why the bans?

The movement to phase out 100LL is driven by growing concerns about the public health impact of lead exposure near airports that commonly service piston-engine aircraft. Lead is a neurotoxin that has well-documented detrimental effects (particularly on children), such as neurological damage, cognitive impairment, lower IQ, and cardiovascular issues in adults. According to a Santa Clara County study conducted at Reid-Hillview Airport, communities around airports experience higher levels of lead exposure. This study revealed that blood lead levels in children near the airport were higher than those in Flint, Michigan, during its water contamination crisis.  The Centers for Disease Control and Prevention (CDC) and other health organizations emphasize that there is no safe level of lead exposure.  Piston-engine aircraft are the largest source of airborne lead emissions in the U.S., contributing about 70% of lead pollution across the country. Eliminating lead from automotive gasoline in the 1970s drastically reduced national lead levels, but aviation fuel remains a major source of this harmful pollutant.

Current alternatives

In response to these health concerns, the Federal Aviation Administration (FAA) and fuel manufacturers are exploring and promoting alternatives to 100LL.  The most notable being UL94 (produced by Swift Fuels), an unleaded avgas designed for lower-compression piston engines that do not require higher-octane.  UL94 is currently available at many airports and eliminates lead emissions entirely, making it a far safer choice for these types of aircraft.  In states like California, where bans have already been implemented, UL94 is being adopted to meet regulatory requirements. Swift Fuels, the producer of UL94, has been expanding its distribution network across the U.S., with more airports starting to offer it as an alternative.  The FAA, along with various stakeholders, has also launched the EAGLE (Eliminate Aviation Gasoline Lead Emissions) initiative, which aims to eliminate leaded aviation fuels by 2030 by promoting the use of unleaded alternatives while ensuring they meet the performance needs of the aviation industry.

Issues with UL94

Despite the environmental and health benefits of UL94, it isn’t without limitations.  It may be an option for lower-compression engines that don’t require higher octane, it has been found to cause engine knocking in higher-compression engines that require a higher octane to operate safely and effectively.  There are no known modifications that can be made to these types of engines that would allow them to run safely and effectively on UL94. In addition to engine knocking, it has also been shown to cause exhaust valve recession. This is due to the lack of lead, which can cause excessive wear on valves and lead to engine wear, efficiency loss, and (in extreme cases) engine failure. The issue recently prompted the University of North Dakota (regarded as one of the top aviation schools in the U.S.) to halt its use of UL 94, citing concerns over engine malfunctions and durability.

These limitations present a major hurdle in the widespread adoption of UL94, especially for industries that rely on high-performance aircraft for operations such as aerial mapping. A drop in replacement would be required to keep these aircraft operational while eliminating leaded fuel use.

Enter G100UL

One promising alternative is G100UL, a fuel developed by General Aviation Modifications, Inc. (GAMI). Unlike UL94, G100UL has been designed as a drop-in replacement for 100LL, meaning it can be used in all piston-engine aircraft without requiring engine modifications. It offers the same high-octane rating as 100LL, allowing high-performance aircraft to maintain optimal operation without the risk of knocking or exhaust valve recession​. The FAA has already approved G100UL for use in all spark-ignition piston aircraft, positioning it as a long-term solution.

Issues with G100UL

For an alternative to become a real solution, it needs to be widely available, which is not the case for G100UL.  The National Air Transport Association (NATA) deems that it is not “commercially available” due to it not having an ASTM International (formerly known as the American Society for Testing and Materials) product specification “Because the FAA does not indemnify any entity in the supply chain for damages caused by fuel-related issues, fuel distributors and FBOs will similarly lack assurances that the unleaded fuel they are selling will not expose them to liability.”

Even if G100UL had the product specification and was commercially available, a bit more than 1,000,000 gallons of G100UL is currently available for sale (as of May 2024).  This would leave 6-7 gallons for each of the 167,000 aircraft currently running on 100LL.

Additionally, some aircraft manufacturers, such as Cirrus, have expressed concerns that using G100UL might void warranties on certain engine types.

Conclusion

The push to ban 100LL is inevitable, driven by undeniable health concerns surrounding lead emissions. However, transitioning to alternatives like UL94 and G100UL presents challenges for aircraft used by aerial mapping firms. High-performance piston-engine aircraft, which compose most of the aerial mapping fleet in the US, face risks of engine failure from using UL94 due to engine knocking and valve recession. While G100UL shows promise as a true drop-in replacement, its limited availability, and potential warranty concerns make the transition a longer-than-ideal process. Rushing to implement and enforce 100LL bans will likely lead to increased insurance premiums and safety risks due to concerns over engine malfunctions. Additionally, higher mobilization costs from rising insurance rates (combined with increased maintenance and fuel expenses) could prolong project delivery times as aircraft face longer maintenance periods and potential fuel shortages.

The aviation industry must balance environmental concerns with operational safety and engine compatibility as it moves toward a future without leaded aviation fuel. Until alternatives are more widely available and proven safe for all piston-engine aircraft, the transition away from 100LL will be gradual but ultimately necessary for the health of both people and the planet.

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