General aviation faces a new legal challenge with one US state government threatening to ban the sale of Avgas and no drop-in replacement available for piston-powered aircraft for at least several years.

The move to ban Avgas by California's Center for Environmental Health is being universally opposed by the general aviation industry.

Lycoming senior vice-president Michael Craft, who also chairs the FAA-sponsored unleaded Avgas transition committee, said federal jurisdiction rules are likely to trump California's attempt to rid its airspace of the most significant source of leaded fuel.

However, Craft said the state's legal challenge is "distracting" the industry and federal officials from continuing efforts to make the transition to unleaded Avgas as smooth as possible.

Lycoming and general aviation manufacturers support the transition to an unleaded alternative to standard 100LL Avgas, but the industry is not ready to make that transition for at least a few years.

The issue has been developing for the past two decades as the piston-powered general aviation sector has become the world's largest source of lead emissions.

Leaded Avgas accounts for 45% of lead emissions in the USA, according to a 2002 study by the Environmental Protection Agency.

Airframe manufacturers have already taken note. When Flight Design launched the new four-seat C4 piston-single earlier this year, the company required engine suppliers to include a transition path to unleaded Avgas.

So far, the options for engine-makers are limited. The first drop-in replacement for leaded Avgas is not likely to become widely available for several years.

One option on display in the AirVenture exhibit halls is 100SF Avgas, being developed by US-based Swift Fuel. The 102-octane fuel replaces lead with an acetone liquid derived from biomass or petroleum. Swift has been testing the fuel on a Beech 50 since April, but final certification remains two to three years away.

The company has launched a pilot production facility in Lafayette, Indiana and is currently studying how to scale-up production to meet demand after certification is completed.

Source: Flight International

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