December 23, 2008
By AOPA ePublishing staff
When it comes to the future of aviation fuels, there’s one place to turn for definitive analysis—the FAA’s Alternative Aviation Fuel and Engine Test Facility, part of the WJH Technical Center, located in New Jersey.
Engineers at the facility are dedicated to working with industry to evaluate fuel options, including possible successors to 100LL avgas.
“I think our facility has been a leader in the area of research to help find a solution—a safe, environmentally friendly solution—to what we all know will eventually go away,” said Dave Atwood, an engineer at the facility who works with a team of seven people to test possible alternatives for leaded avgas.
Not only do they analyze potential fuels developed by universities and oil companies, they also provide guidance that can be used to help develop new fuels to test.
“We’ve been working very diligently with members of all the major research organizations,” said Atwood. “We have been key in providing data and support, not only to the standards bodies that make specifications for new fuels, but to the research organizations as well.”
When the lab first opened in 1990, there was a lot of debate about just what factors should be tested to determine if a fuel blend would be a good alternative fuel for the existing general aviation piston fleet. But eventually industry and science agreed that octane is the critical element, and lead is an octane booster.
“We decided let’s just focus on the octane because if you can’t get the octane right, it’s not going to work,” explained Atwood. “Detonation performance was the original key.”
After testing 77 different fuel blends, it became clear to everyone involved that it was unlikely any fuel could achieve an equivalent octane rating without including significant amounts of environmentally hazardous chemicals.
"However, the FAA Technical Center is also testing bio-derived alternative fuels," Atwood later explained. "Initial and recent testing of a Swift Enterprises 702 bio-derived fuel showed the fuel to provide better detonation performance than a locally purchased 100LL without the same hazardous chemical concerns. Further engine endurance testing on the Swift 702 fuel is planned for 2009."
The testing process can be an arduous one because engineers must consider much more than whether or not a given fuel will make the engine run.
Testing begins with laboratory analysis to see how closely any new fuel matches the specifications for 100LL. Then a team of seven testers evaluates factors that include power performance, mixture response, detonation margin of safety, volatility, and compatibility with other materials used in the fuel system such as hoses and seals. The team also must look at endurance factors, like whether the fuel causes unusual wear and tear on engine components or leaves buildup or deposits that could impair performance over time. Those tests require running real aircraft engines on test stands.
While the initial round of tests can be accomplished in just a few months, making a final determination that a fuel is an acceptable successor for 100LL will require extensive flight testing and take much longer.
While the FAA does not certify fuels, it does certify aircraft. So once a decision is made to implement a successor fuel, the FAA testing center would likely be involved in determining certification requirements for any needed modifications to the existing piston engine fleet.
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