Devils Advocate: They need to evaluate very carefully the switch. If an engine was designed to run on 100LL then there's a switch to G100UL then care must be taken to ensure it won't mess up the engine. We're not talking about a land based engine (like a car) where if the engine stops you just coast over to the side of the road and call a tow truck. You're talking about an emergency landing which means possible damage to people and property other than the pilot and plane. Many of the general aviation planes out there were built in the 60's and 70's so the FAA needs to be sure it won't cause problems.
> To scrub the playhead forward, last summer at Oshkosh, to great fanfare, the STC approving G100UL was announced. It applied to a limited number of engines and GAMI was tasked with additional testing and data work to expand the engine list. This it did. The Wichita Aircraft Certification Office duly sent a letter to FAA HQ reporting that GAMI met all the test requirements—best-run program they had ever seen, or words to that effect—and was entitled to an STC-AML with every single spark ignition engine in the FAA database approved to use G100UL.
> The document rests on the desk of the executive director of the Aircraft Certification Service otherwise known as AIR-1. It’s awaiting the signature of AIR-1, who is Earl Lawrence. No date certain has been given, but in yet another last-minute delay, the FAA is now subjecting the STC to a Technical Advisory Board, a bureaucratic fence line that sprang out of the 737 MAX fiasco. The legislation that enabled TABs specifically applies to transport aircraft weighing 150,000 pounds or more, Braly says, and it hasn’t been explained how it can be applied to light aircraft.
>At a press conference, Lawrence said he thought PAFI had been “a great success.” I simply cannot agree. I don’t know how anyone in the industry could think this. PAFI was supposed to yield an unleaded drop-in replacement for 100LL. It did not. It was an abject failure and now, even though the FAA has an STC in hand awaiting approval for a fuel that has been proven, ad nauseum, to work in all engines, it wants more money for more testing. While the PAFI program—that was Piston Aviation Fuels Initiative—supposedly produced data, accessing it is all but impossible.
