Mogas in Aviation

Thanks for the pic and info on the RVP.  The standard summer blend RVP in the USA is 9 psi - which equals your 62 kPa.  During winter the RVP values increase significantly - up to 15 psi (103 kPa) in extremely cold climates.  In Oregon, winter blend Mogas has 13 psi (90 kPa) RVP.  Avgas (in the USA) has an RVP of 5.5 to 7.0 psi (38 to 48 kPa) throughout the year - which is much less susceptible to vaporizing and causing vapor lock.

You mentioned that you skipped portions of the video because it wasn't relevant to your situation, but if you haven't seen the chapter on "The Danger Zone", you might find it interesting.

Hello Jeff,

Your home RVP test chamber is great!  Do you mind if I share it with others? There is a good chance that I will be presenting my "Mogas in Aviation" topic at Airventure this July and I could include a slide about your device.  If you are okay doing that, let me know how to give credit to you (name, contact, other info)?  I'll build one!

Thanks,

Ron

Hey Ron,

No problem with sharing it as you see fit, and no need to credit me in your presentation.  If you want to discuss it further you can contact me at Jeffb@BlakesleeElectric.com .  

I have found this test method to be quite accurate.  I get results of 7 psi with Avgas, 8-9 psi with California summer blend, and 12-13 psi with California winter blend. I like knowing what’s in my tank.   

It is possible we have summer/winter petrol blends in Australia however a quick search revealed little confirmation/information on this.

The southern reaches of our Great Dividing Range ( hills compared with so many other ranges) may have winter/summer petrol as temperatures go quite low (by Aussie standards). I doubt the rest of the country has much call for it.

I'm a science guy so,,,,,

The only issue I have with this is that rarely does the auto fuel have the ethanol that is posted on the pump. The ethanol is blended in at the tank farm where trucks load up and bring it to the gas station for the customer. Fuel with ethanol is not pumped through the pipelines from the factory. So if a trucker puts 2K gallons in their truck then he looks at a chart that tells him how much ethanol to put in. 

So I have two guys at my field that test every batch of fuel they use in their 912ULS for the last 15 years. In Arizona they say we have 10% all the time.  When actually tested it is always 6% - 7 % and only a few times it was 8%. Those in the US that use 15% winter blends are in the same boat. Other places in the US say UP TO 10% or 15%.  So your numbers can be off unless you test the batch you claim has too much vaporization.

Plus here in Arizona we see daytime temps of 100F - 110F. Why aren't all our planes using 91 oct. with ethanol falling out of the sky and or at higher altitudes? You haven't addressed other factors. Things like air flow through a cowl, were the fuel hoses in the engine that failed in protective fire sleeve, did they have a re-circulation line and where did it return the fuel to, ect...

In the last 20 years and with thousands of hours why haven't I had these issues up to 12K altitude? Why hasn't the hundreds of owners I personally know not had any issues? It isn't luck it's a combination of other factors that all play a part.

You must rule in or out other factors because it's not a one size fits all scenario. What was different that one guy had a failure when thousands around the world in hot climates don't?

Just had a guy from Colorado (in the US)  fly down to me at 12K - 12.5K with a Flight Design CT without any issues.

Don't get me wrong this is worth considering, but do it with full and COMPLETE scientific facts to apply to your situation.

It's not just about the fuel.