Forget ASTM or the STC process: Maybe it’s time to look at a specification for unleaded avgas in a whole new way.
EPA
Blame it on the lawyers
When there is a problem with the transition to unleaded avgas, maybe those affected will sue the EPA or the FAA. But more realistically they will sue everyone from the airplane manufacturers to the fuel distributor, letting the courts sort it out to determine the winners and losers.
Drop-in unleaded replacement for 100LL expected to be approved in late 2025
A fleet wide approval for an unleaded fuel for general aviation is expected in the third quarter of 2025.
STC vs ASTM: What’s best for unleaded fuels?
There is some confusion as to how the ASTM process compares to Supplemental Type Certificate (STC) approval for the unleaded fuels that will replace 100LL. Some people even think that they are basically the same. In reality they are very different and most of that difference goes back to our old friend liability.