An unmodified Pratt & Whitney R-2800 Double Wasp engine running on Swift Enterprises’ high-octane unleaded fuel 100SF showed no signs of knock in an informal round of testing, Purdue Research Park announced Oct. 25.
High-powered radial engines, designed to run on 115/145-octane fuel, present a significant challenge to any developer of an unleaded fuel. These engines already must run on reduced power settings on today’s lower-octane 100LL, and losing the knock protection provided by lead could further shrink their operating margins. The testing was part of an effort to prove that the fuel can meet the needs of engines that demand high-octane fuel, like the radial-engine aircraft that play an especially critical role in transporting people and supplies in Alaska—a question that Swift Vice President of Renewable Fuels Jon Ziulkowski said frequently arises during meetings with industry.
“Everybody says, ‘Yeah, but will it work in a radial engine?’” he said. Now, the company can say, "Yes," he added.
“It turns out it’s at least as good as 100LL."
A&P mechanics at Anderson Aeromotive Inc. conducted testing over three days in Grangeville, Idaho, operating at 115- to 145-octane takeoff power settings with no sign of engine knock, Purdue Research Park said. The R-2800 burned more than 100 gallons of 100SF, which produced a higher detonation threshold than 100LL, the business incubation complex added.
Norman Koerner, president of TriCap International Inc., organized the testing at Anderson Aeromotive, an outfit with significant radial engine experience, Purdue Research Park noted in a news release. Texas-based TriCap provides consulting and management services for aircraft modification, specializing in high-performance piston aircraft such as the Douglas A-26 and DC-3 and the Lockheed PV-2.
Swift’s fuel will undergo another, more extensive, formal round of radial engine testing in 2012, the release noted. Ziulkowski said Swift expects to conduct those tests in the demanding environment of Alaska, running the fuel on an aircraft there and measuring such performance parameters as detonation and resistance to detonation, compatibility with the engine, and cold-weather performance.
The testing also will explore the possibility of operating at higher power settings than on 100LL because of 100SF’s slightly higher octane, Ziulkowski said. “To an air carrier in Alaska, that makes all the difference,” he said.
Koerner said in the news release that the testing will help pave the way for legacy aircraft to continue to provide essential services.
"Additionally, 100SF will be able to power the heritage aircraft that are indispensable in preserving the history of World War II,” Koerner said. “I think it's the right thing to do, so let's 'keep 'em flying!'"