Use Of 100R Avgas Is Restricted, Swift Says

Swift Fuels has made available its new 100-octane unleaded avgas on a “restricted use” basis at some flight schools as it awaits conferral of an industry-accepted fuel specification—something a competing avgas lacks, Swift emphasizes.

In a Nov. 11 website posting, Swift clarified that its 100R unleaded avgas has been approved by the FAA for use in Cessna 172R/S models by supplemental type certificate (STC) but awaits a production specification from standards organization ASTM International. The company says a draft specification is undergoing review through ASTM’s ballot process, which it expects will be completed in the next several months.

“By operating on a restricted use basis without an ASTM specification, the 100R fuel is not yet commercially available for broad distribution or use,” the company said. “Swift Fuels has been clear and consistent in our belief that a ‘commercially available’ fuel must combine FAA certification approvals along with an ASTM International specification so that the marketplace can access it openly across the global aviation fuel supply chain.”

Swift’s posting coincided with an announcement by San Carlos Flight Center in northern California that it had started fueling its Cessna 172 training aircraft with 100R.

After being approached by several flight schools, Swift said it made an exception to allow for restricted use of 100R at selected airfields where 100 Low Lead (100LL) is available “to offset a localized challenge,” to highlight the importance of an ASTM specification, and to reassure the industry that its 100-octane unleaded fuel will be commercially available soon. The company says 100R can be commingled with 100LL, the most common grade of avgas, which is needed for safe operation of aircraft with high-horsepower, high-compression piston engines.

The announcement by San Carlos Flight Center in early November followed news that Reid-Hillview Airport (RHV) in nearby San Jose, California, had started pumping General Aviation Modification Inc.’s (GAMI) G100UL avgas, becoming the first U.S. airport to offer the competing 100-octane unleaded fuel. County-owned RHV stopped selling 100LL in 2022 in contravention of FAA grant assurances after a study revealed elevated blood-lead levels in children living nearby.

GAMI Offers Incentives

In advance of the fuel’s availability on Oct. 30, GAMI offered the owners of aircraft based at RHV and nearby San Martin Airport (E16), both owned by Santa Clara County, a full refund of the cost of engine and airframe STCs required to use G100UL through Nov. 1. GAMI also made available the services of an FAA-certified mechanic Nov. 2 to sign off on the required FAA Form 337 (major repair and alteration) at no cost.

Aircraft owners at RHV and E16 who had already acquired STCs were provided a credit voucher for the purchase of 50 gal. of G100UL.

The GAMI fuel received STC authorization from the FAA in September 2022 for use in all spark-ignition piston engines and airplanes. But its acceptance by aircraft and engine manufacturers has lagged due to the fuel’s lack of an ASTM product specification and questions over its compatibility with materials in the fuel distribution network.

Cirrus Aircraft issued a service advisory (SA24-14) in June saying it was engaged in comprehensive testing and evaluation of G100UL but did not approve of its use in Cirrus SR Series airplanes at the time. The company further advised that engine manufacturers Continental and Lycoming had not approved G100UL and may not provide warranty coverage of engines known to have burned the GAMI product.

Swift said several airports in California had brought to its attention that they were approached by the producer of G100UL and that the producer “was exerting extreme pressure on the California airports leadership” to begin buying the fuel.

“Recently one airport was compelled to offer G100UL unleaded avgas at highly discounted pricing for the fuel and STCs to make it appear attractive to buyers despite market concerns recently reported about paint staining/stripping, bladder leaks, elastomer warnings, Cirrus advisory SA24-14, and Lycoming warnings,” Swift said.

“These publicized concerns stem from the fact that G100UL contains a large quantity of xylene plus an aggressive solvent (3-4% m-toluidine) known to potentially alter the performance of certain fuel system parts —particularly elastomeric-type parts,” Swift added. “For unknown reasons, the producers of G100UL have been unwilling to submit their fuel to ASTM International for industry-wide vetting.”

Asked for its response to the Swift posting, GAMI said that no airport was compelled by GAMI or its producer Vitol Aviation to begin offering G100UL. It said two airport authorities—Santa Clara County and the city of Watsonville, California, which operates Watsonville Municipal Airport—have entered into contracts to purchase the new fuel.

None of the 125 pilots who came to RHV on Nov. 2 to obtain STCs “expressed any reluctance to purchase and use G100UL avgas in their aircraft for any reason,” GAMI said. It alleged that Swift’s 100R draft specification, meanwhile, had received multiple “negative” reviews as part of the ASTM balloting process.

“GAMI’s G100UL avgas has been fully ‘vetted’ by leaders in the petroleum and chemical industry and their favorable findings are consistent with those of the FAA, which has (without any restrictions) approved G100UL avgas for use in all spark ignition piston engines and the associated airplanes,” the company said.