When I started to write this post on unleaded avgas, I sat down to read about the upcoming evaluation program for four candidate fuels. The more I read the more questions it raised.
For instance, why does Swift Fuels have two candidates?
But the biggest question concerned the percentage of the piston aviation fleet that the new candidate fuels will satisfy. A few questions arise, like which engines are the most critical, under what conditions will they knock, which airframe, propeller, operating conditions are most critical, and on and on.