The technique of approval by way of an STC is still problematic for a drop-in or blended product. For example, even if GAMI gives away the STC approval for free, how do they ensure that their fuel product isn’t sold to an airplane that doesn’t have the STC “installed”? I know George says he can print out the STC on the fuel receipt, but installation of an STC on an aircraft isn’t something a pilot can do. Even a garden variety A&P can’t do it. A major alteration needs to be accomplished by an IA with a form 337.
Or perhaps this is one of those cases where we decide that the presence of an STC doesn’t mean something is a major alteration? (Rosen sun visors anybody?) If it’s not a major alteration (if it is a minor alteration) then we’re back to only needing an A&P to sign it off.
If we’re saying it’s not an alteration at all, then do we care what airplanes are covered by the STC in the first place?
It’s a slippery slope.