The approximately 611 engines included in an approved model list issued October 28, plus the more limited number of approvals GAMI announced in July, account for about 70 percent of the GA aircraft fleet’s powerplants, said AOPA consultant and aviation fuels expert Paul Millner.
Airframes approved for pairing with the engines will be identified separately on a list expected soon from the FAA.
“This is a very bullish sign that the FAA is continuing to honor their commitment to move unleaded avgas forward as fast as possible,” Millner said.
He added that the accelerated commitment reflects new urgency arising from the FAA’s awareness that some local governments are taking action to ban leaded avgas from being used at airports in their jurisdictions. Those actions are further pressuring efforts proceeding on multiple fronts to develop unleaded fuel and reduce the lead content of some fuels.
Although the approved engines comprise a large percentage of the GA fleet—used mostly in aircraft that burn lower octane fuels—the remaining 30 percent of engines require 100-octane fuel and account for 80 percent of total avgas utilization, he said.
Those engines should make up the bulk of the “fleetwide expansion” of approvals to use unleaded fuel that George Braly, GAMI’s chief engineer, told an AOPA webinar audience in September that he was expecting from the FAA early in 2022. At that time Braly’s upbeat presentation described the FAA’s attention to the issue using terms similar to those tapped by Millner—noting that the approval process was by agency standards, “progress at the speed of light.”
As each new announcement in the stepped-up projects to remove lead surfaces, the elephant-in-the-room question of how to make the fuels available remains. GAMI and fuels distributor Avfuel have outlined their work on a distribution strategy for GAMI’s G100UL avgas, and Millner added that the companies are “accelerating its introduction in areas where 100LL is being taken away.”
On another of the major fronts to develop an alternative avgas, AOPA, the Experimental Aircraft Association, and the General Aviation Manufacturers Association are working with the FAA and other industry groups in the Piston Aviation Fuel Initiative (PAFI) to develop a safe and viable high-octane unleaded avgas that would replace 100LL and maintain the utility of the existing fleet.
The PAFI process is available to all fuel developers as a means for technical support from key stakeholders and to help enable a cost-effective approach that would meet the needs of the entire GA aircraft fleet through an FAA fleetwide authorization.