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Posted on Sun, May. 31, 2009

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Planemakers challenged to find unleaded fuel option

BY MOLLY MCMILLIN

The Wichita Eagle

The elimination of lead from automotive fuel has long been hailed as a top environmental achievement.

But finding a replacement for the leaded aviation fuel that powers tens of thousands of piston engine aircraft flying in the United States today has proven to be much more difficult.

Eventually, the Environmental Protection Agency will phase out its use.

And economic factors could affect its cost and continued availability.

Identifying the right fuel and putting in a plan to transition to it is vital, said Walter Desrosier, vice president of engineering and maintenance at the General Aviation Manufacturers Association, an industry trade group.

It's necessary to "ensure the viability and health of the general aviation industry," he said.

The industry cut the amount of lead additive in aviation fuel in half during the 1980s -- resulting in the 100 octane "low lead" aviation gasoline in use today -- in response to health concerns about lead. That's the minimum octane necessary to ensure safe flight of the existing fleet of general aviation aircraft, GAMA said.

But finding an acceptable fuel without lead is taking time.

"We did not find a fuel that we can simply replace 100 low lead and it would have the same level of performance and the same level of operation for the entire fleet of general aviation aircraft," Desrosier said.

A replacement must ensure the aircraft would operate safely, be environmentally friendly, economically feasible and have the ability to be widely distributed to airports and fixed-base operators, the trade group said.

"We've never had to go backwards and approve an existing engine and an existing airplane to a new fuel," Desrosier said.

Only one supplier left

The world has moved away from lead additives in fuels, and demand has plummeted.

With less demand, there's only one main supplier of the lead additive used in avgas in the world.

That brings with it the risk of rising costs or interruption of supply, Desrosier said.

The supplier, Innospec in the United Kingdom, has assured the industry it will continue to produce the additive and make it available.

Still, there's risk, Desrosier said.

"If something happens in the transportation... suddenly there's a stop in supply and 100 low lead avgas may not be available," he said.

That would have a detrimental economic impact to the U.S.

Piston-powered aircraft engines, high-performance engines in particular, have been built for use of high-octane leaded fuel.

The lead boosts the fuel's octane rating, and that helps prevent destructive detonation that can occur with the high-performance engines.

"If you don't have 100 octane fuel -- leaded or unleaded -- those aircraft will be grounded without significant investment," said Michael Kraft, vice president of research and development and engineering at Lycoming, an engine manufacturer.

It's a big issue for Wichita planemakers.

"We're trying to find an alternative that will work with the planes that are out there in the fleet," said Stan O'Brien, Hawker Beechcraft's project engineer for piston engine aircraft. "It makes it a difficult challenge."

Performance levels on aircraft must be tested.

"Can you imagine if you just bought a new Bonanza last year and we say, 'Oh, by the way, here's your (new, lower) performance levels,' " said Hawker Beechcraft vice president of product development and engineering Ed Petkus. "You wouldn't have happy customers."

Unleaded options

Two unleaded fuels are being evaluated for their potential.

One is a petroleum-based fuel similar to avgas, but without the lead.

Most of the planes flying would be able to use it and have the ability to make a transition to it relatively easily, Desrosier said.

But because the octane is lower, high-performance aircraft would need physical modifications, Desrosier said.

Only 30 percent of the fleet using avgas are high-performance planes, but they consume 70 percent of the fuel.

They're the planes most likely to be used in commercial businesses. They would feel the biggest impact.

"We need to understand the affect to the fleet and what modifications would be available at what cost," Desrosier said.

A second fuel undergoing testing is a synthetic bio-based fuel produced by Swift Enterprises in Indiana. It's high-octane and unleaded.

So far, it's performed well and seems promising.

Hawker Beechcraft's Bonanza G36 was the first to fly on Swift's fuel, the company said.

The Swift fuel must still be tested and validated to ensure its compatibility with an aircraft's structures -- the aluminum, hoses, seals, fuel bladders and fuel systems, Desrosier said.

And its distribution and the ability to produce it must be determined at the cost, quantity and quality needed.

The fuel is heavier, or more dense, than avgas. But it also has a higher energy content, Desrosier said.

Lycoming is not endorsing a particular company but sees promise in a synthesized high-octane fuel, Kraft said.

Engine makers are testing unleaded fuel.

Lycoming, for example, is making sure any new engine is capable of running on lower-octane unleaded fuel, Kraft said.

Last year, it introduced an engine that can use whatever the fuel of the future will be.

"You have to be very much in tune with the fuel to correctly design the engine," Kraft said. "That's really driving all of our (research and development)."

Reach Molly McMillin at 316-269-6708 or [email protected].