FAA Posts New Guidance For Fuel Approvals

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The FAA has published a new Advisory Circular providing guidance for the approval of new aeronautical fuels. Issuance of the document aims to "facilitate the aviation fuel approval process," according to the FAA, by "clarifying and describing" acceptable methods of compliance to existing FAA regulations. But unknown to most in the industry who aren't involved in fuel work, AC 20-24 sparked controversy last summer when proponents of a quick replacement for 100LL complained to FAA's upper management that the agency's Engine and Propeller Directorate was dragging its feet on allowing STCs for fuel approvals.

Specifically, General Aviation Modifications, Inc. had applied for an STC for its G100UL development fuel. Months after the application, the FAA still hasn't issued the STC, but we're told by GAMI that progress is being made. Interestingly, earlier this summer, the Engine and Propeller Directorate quietly issued a memo from the office's Mark Rumizen pointedly saying only ASTM approvals would be accepted by the FAA, not STCs, this despite a policy statement from FAA upper management that all paths to approvals would be acceptable. Just as quietly, the memo was withdrawn in late July.

The new AC 20-24 is actually a revision of a previous document, updated to meet the demands of certifying new fuels. "The recent increase in new and alternative aviation fuel development efforts necessitates clarification of the FAA approval policy to support these many projects for both avgas and jet fuel," according to the FAA's response to comments on its draft of the new AC. The FAA also notes that the AC actually doesn't address how to approve a fuel, but provides guidance on "how to approve engines and airplanes when operating on a specified fuel."

The AC doesn't create new rules, but explains to the aviation community -- especially those interested in developing new fuels -- how the FAA interprets the rules already on the books. The aim of the AC, the FAA said, is to "ensure any fuel that is approved will have been evaluated to the extent necessary to perform in a safe and consistent manner when introduced in service." The FAA said it has funded an extensive amount of research on unleaded avgas and "the FAA Technical Center is recognized as the industry leader for evaluation of candidate aviation gasolines." Also, the FAA has established the Unleaded Avgas Transition Aviation Rulemaking Committee (UAT ARC) to work with industry to develop a plan to address this issue. A report on that committee's activities was expected at AirVenture, but furloughs caused by Congressional budget fights cancelled it.