By Glenn Pew, Contributing Editor, Video Editor
Lycoming has applied for approval to run multiple families of Lycoming engines on the unleaded avgas, UL 91. The company has submitted for ASTM D7547 approval, a relatively new standard, specifically for 233-, 235-, 320- and 360-series engines. According to Lycoming spokesman Scott Miller, the approval process is likely to take weeks -- not months -- and certain 540-series engines could follow. The fuel is an avgas, not a mogas, and conforms to aviation standards. But even if your engine is approved to run on UL 91, and you happen to have the it available, that alone doesn't necessarily mean you'll be able to use it in your airplane here in the U.S.
Miller told AVweb, Wednesday, "If your engine is approved on this fuel then your airframe is automatically approved ... in the EU. In the U.S., if the engine is approved, you may still need approval for the airframe." The first U.S. approvals should greet engines that were originally approved on 80/87 avgas. Those engines usually are approved for 80/87 or higher octane fuel. Some engine models may have received type certificates after 80/87 stopped being available, but should be able to run it also. Those engines will need to be "validated," Miller said, citing the "weeks -- not months" timeline. Asked if the move was stimulated by two recent lawsuits involving leaded avgas, Miller said, "This is independent of the lawsuits by CEH and Friends of the Earth." That said, UL 91 will likely see highest demand in regions where 100LL is not available, often due to concerns (if not laws) regarding lead additives.