‘Transparency’ Urged In Unleaded Avgas Development

refueling avgas 100LL to Piper M350
A piston-engine aircraft received 100LL fuel during the recent EBACE conference.
Credit: Mark Wagner/Aviation Images

Piston engine and aircraft manufacturers have not been able to test candidate unleaded fuels in sufficient quantities to understand their properties, executives said June 5 during an update briefing on the FAA and industry Eliminate Aviation Gas Lead Emissions (EAGLE) initiative.

“We’re all excited about this, and we’re optimistic it’s going to work, but we have tested nothing to date,” said Textron Aviation President and CEO Ron Draper. “We have been trying to acquire the fuel and the ability to test the fuel and have been unable to do so. We can’t endorse or speak good or bad about [a fuel] until we test it and fly the heck out of it.”

There are currently four high-octane unleaded fuels being developed on separate pathways to work across the wide variety of piston aircraft and engines in the U.S., Lirio Lui, executive director of the FAA’s Aircraft Certification Service, told the online audience. Two fuels are progressing through the Piston Aviation Fuels Initiative (PAFI), an industry-government testing program that dates to 2014, and two through the FAA supplemental type certification (STC) process, which is proprietary between the agency and fuel developers.

The partnerships of Afton Chemical-Phillips 66 and Lyondellbasell-VP Racing are advancing candidate fuels through the PAFI program. Testing procedures and results are shared with participating companies, Lui said. Upon successful completion of the testing, the FAA will issue a fleetwide authorization, allowing use of the fuel by aircraft owners.

“Both teams have completed extensive testing,” Lui said. “They have fine-tuned their fuel formulations based on some feedback and they are in the final initial phase of testing, with the Lyondellbasell fuel at the [FAA] Tech Center. Testing for the Afton-Phillips 66 fuel will begin shortly at one of our engine manufacturing facilities.”

The FAA plans to authorize the use of low-octane UL91 unleaded fuel later this year through the fleet authorization process. The release of UL91, which should work across 68% of the piston-engine aircraft fleet, “will facilitate broader-use experience with the transition” to a higher-octane unleaded fuel, Lui said.

Last September, the agency issued broad STC approval of General Aviation Modifications Inc.’s (GAMI) G100UL high-octane unleaded fuel, which GAMI contends will work across most piston-engine aircraft. The FAA expects to authorize a second unleaded fuel going through the STC route—Swift Fuels’ 100R—later this year, Lui said.

The word “transparency” was used several times during the briefing. Representatives of the engine and aircraft manufacturers that participated, including Lycoming Engines, Piper Aircraft and CubCrafters, said they need for more information about the properties of the candidate unleaded fuels being advanced. 

“A wholesale fuel change is not a typical, incremental product improvement,” said Piper Aircraft President John Calcagno. “It’s an outside requirement not within our normal span of control through type certificates.”

Rob Hackman, Experimental Aircraft Association vice president for government affairs, said more information has been disseminated to engine and aircraft original equipment manufacturers (OEM) through the PAFI program.

“The two [developers] that are in the PAFI program have supplied significant amounts of fuel to be tested in that program,” Hackman said. “A lot of that testing was either done by the FAA at the Tech Center or by the OEMs through in-kind agreements. Those OEMs that are participating in the program have had insight into those fuels.”

Hackman added: “The challenge of not being able to see or have visibility into the fuels comes a little bit more from the STC side, where the STC program, by its nature, is proprietary between the FAA and the applicant. Both the components in the fuel are proprietary but also the certification program that’s used to be granted the STC. 

“That’s what we’re hearing the community all the way out through the amateur-built [aircraft] community saying, is we need more visibility into those fuels to have a better understanding as to how they’re going to be able to work.”
 

Bill Carey

Based in Washington, D.C., Bill covers business aviation and advanced air mobility for Aviation Week Network. A former newspaper reporter, he has also covered the airline industry, military aviation, commercial space and unmanned aircraft systems. He is the author of 'Enter The Drones, The FAA and UAVs in America,' published in 2016.

Comments

2 Comments
Ah use this untested fuel in your piston aircraft! Be happy we took out the lead! Really?
Leaded fuel might not kill you but hard ground contact utilizing an unavailable for full testing fuel just might.
Ah use this untested fuel in your piston aircraft! Be happy we took out the lead! Really?
Leaded fuel might not kill you but hard ground contact utilizing an unavailable for full testing fuel just might.