TwinPOS wrote:Experimentals are different, I am not aware of an STC that allows ethanol. The big issue being certifying, a whole new fuel for a relatively small number of airframes. Remember that the airframe and engine in certified models must both pass the test for the FAA to grant an STC. I would be careful experimenting with blended fuels at altitude or in warmer temps after being left on the ramp in the sun. This is very close to the worst case scenario testing that the FAA submits planes to.
This being said, when STC'd, I love using Mogas, and wish you the very best of luck with your project.
PS try boat guys, and classic car guys and calling jobbers in the area to see if clean gas is being sold locally, you might have a good close by resource.
You answered the question quite perfectly... The FAA needs a constant, repeatable and realiable source of fuel to conduct testing.. It seems every fuel distribution network has its own "special" blend. Hence the comment I made about the variability of Ethanol percentages I found at my local station... There is NO way a STC can be issued when the end user cannot be assured that the fuel he buys meets the STC spec..
In my opinion the airframe is the biggest drawback...... Motors are pretty tolerant of various blends of fuels. For instance,, the vapor lock issue keeps coming up, but all summer long, in the summer heat, passenger cars and light trucks drive to the top of Pikes Peak at over 13,000 msl hundreds of times a day and the rate of vapor lock happening is almost nil. YMMV.