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'Two fuels' in a baron

How AOPA is working on avgas solution

The AOPA fuel demo Beechcraft Baron is nearing 100 flight hours using unleaded fuel in one of its engines, and so far the performance is indistinguishable from the traditional avgas  being used in the other engine.
Photography by David Tullis.
GAMI G100UL unleaded aviation fuel is tested in a multiengine Beechcraft Baron C-55 in and around Ada, Oklahoma, on October 30, 2023. Photo by David Tulis.

The 1966 Baron C55 has been operating out of Ada, Oklahoma, where General Aviation Modifications Inc. (GAMI) has been supplying unleaded G100UL for the Baron’s left engine and avgas in the right.

A half-dozen pilots have flown the airplane using this “two fuels” arrangement, and all have found the G100UL’s performance virtually identical to avgas.

“You really can’t tell the difference in the air,” said John Whitehead, a retired FedEx pilot with extensive instructional and flight test experience in a variety of Beech airplanes, including Bonanzas and Barons. “If you didn’t know the engines were using different kinds of fuel, you couldn’t tell by the way they perform.”

On the ground, there are obvious differences. G100UL has an orange tint (instead of blue avgas), and it smells a bit like turpentine or cleaning solvent. G100UL also is slightly heavier than avgas but the weight difference is small enough that it’s unnoticeable to pilots.

The AOPA Fuel Demo Baron is scheduled to undergo a series of borescope inspections, compression tests, and oil analysis when it reaches 100 flight hours. Engine and airframe experts will scrutinize the results looking for unusual wear within the engines as well as fuel lines, bladders, and other components. The AOPA fuel demo Baron is equipped with a digital engine monitor that records a wide variety of data, and a team at Savvy Analysis will use their analytical tools to compare the Baron’s Continental IO-520s. The Baron will return to AOPA headquarters in Maryland early in 2024 once G100UL is available there.

AOPA President and CEO Mark Baker intends to take GA leaders for flights in the Washington, D.C., region to give them first-hand experience flying with unleaded aviation fuel. G100UL is currently the only unleaded 100-octane fuel the FAA has approved for use in the full spectrum of piston aircraft engines. When other unleaded fuels become available, the Baron will be used to try them, too.

“The shift to unleaded aviation fuel is happening, and it’s critical that the change is made safely,” Baker said. “The AOPA fuel demo Baron gives us real-world experience with unleaded aviation fuels in the kinds of engines our members own and operate.”

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Dave Hirschman

Dave Hirschman

AOPA Pilot Editor at Large
AOPA Pilot Editor at Large Dave Hirschman joined AOPA in 2008. He has an airline transport pilot certificate and instrument and multiengine flight instructor certificates. Dave flies vintage, historical, and Experimental airplanes and specializes in tailwheel and aerobatic instruction.

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