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AirVenture Today
It’s…complicated
D
espite the wide variety of innovative aircraft at EAA Oshkosh 2013, most share one thing: They consume fuel. Of the three basic fuels commonly used by general aviation—100LL aviation gasoline, Jet A and unleaded gasoline—only one of them contains tetraethyl lead (TEL), a toxic substance long ago removed from automotive gasoline. That fuel is, of course, 100LL, and its lead content is an ongoing health, environment, and economic issue, which means it eventually will be replaced.
PHOTO BY PHIL WESTON
By Joseph E. (Jeb) Burnside
But with what? There simply isn’t a current substitute for 100LL that works for the existing fleet of GA aircraft. A large number of certificated and experimental aircraft are operating just fine on unleaded automotive gasoline—for 30 years. For a significant portion of the fleet, however, mogas as it’s called simply doesn’t have sufficient anti-knock characteristics—among other issues— to allow safe, efficient operation. And given the sorry state of new piston-aircraft sales—at least compared to 10 or
so years ago—the existing fleet is the market for 100LL and its successor. Although industry and the FAA have known for some time that 100LL’s days are numbered, when and how the fuel is replaced, and with what, remain unanswered questions. Those questions also mean there’s significant uncertainty on the potential impact replacing 100LL could have on the future of general aviation. After some not-so-gentle prodding from health and environment groups, plus the U.S. Environmental Protection Agency, the FAA and industry are working together to find the answers. Most recently, acting on industry recommendations, the FAA initiated an unleaded avgas program and created a new office to manage all fuels-related testing and certification issues, among other challenges. But the basic problem remains: Coming up with a replacement for 100LL isn’t as simple as just removing TEL. Consider: If lead is removed from 100LL, something has to take its place. Many substances are available with high octane qualities, but there’s no free lunch: Altering one component of the 100LL “recipe”—
also known as ASTM D910—to eliminate lead easily can impact the fuel’s other characteristics, perhaps increasing its ability to absorb water, promote corrosion in fuel systems, or dissolve rubber fuel bladders. And from a consumer perspective, one of the most important characteristics a 100LL replacement should have is reasonable cost. Removing TEL and replacing it with some exotic substances could mean avgas’s already too-high cost could climb further. No one wants that. Another issue is certification. Many non-experimental aircraft are certificated to operate on 100LL. If 100LL isn’t available, what then? Put another way, what’s the legality of operating an aircraft certificated to use 100LL on an unleaded 100 octane fuel? At a minimum, it may require securing from the FAA an expensive and time-consuming STC for each and every make/model airframe and engine. The testing necessary to obtain an STC may result in new limitations or require component replacement, further increasing the cost. There needs to be an efficient and effective means for FAA fleetwide