[f-AA] Auto-gas STC

[John Rodkey]

Not very common anymore, since the addition of ethanol to most gas.

Auto gas pitfalls:
 - stability - because of the additives, auto gas goes 'bad' after a while:
avgas doesn't.  If you fly regularly, this shouldn't be a problem.
 - safety - If you don't have a grounded delivery system, you're playing
with fire, literally!
 - vapor point - at altitude ( 10K ?) the autogas, being more volatile, may
result in vapor lock.  This is a perhaps disputable point - and probably
moot for our Aeroncas at 1000 AGL, where many of us fly.
 - effect on 'old' rubber hoses, carb parts. Alcohol is the big danger, but
MTBE which was used for a while in CA before it was discovered to be more
harmful than ethanol, has the same effect.  This is less problematic if you
have recently replaced gas lines and have a steel needle in your carb.
- MMO - using autogas makes you more likely to use MMO, which we all know is
bad (just kidding).

There's a simple test to find out the percentage of alcohol in your gas: put
a known amount of water in a tube with about 10 times as much gas.  Shake.
Let it settle.  If the apparent amount of water increases, you've got
alcohol.
Given a bit of precision, you could determine the exact percentage of
alcohol,
but I believe the STC for ethanol from Peterson specifies no alcohol, so
even though the percentage may be low (I think they have to label gas if it
has more than 3 or 4 percent),  you'll still be violating the STC.  And, of
course, then you
become a test pilot.  Best done out over the Mojave desert, where there are
lots of places to put the plane down safely.

John

John

On 12/1/06, Dwayne.Lafave at k12.sd.us <Dwayne.Lafave at k12.sd.us> wrote:
>
> How common is the use of auto gas in a 7AC?
> Any pitfalls one needs to be aware or if using auto gas?
> I know not to use ethanol, but have heard some concerns about lesser
> amounts of alcohol being added to gas without having to be labeled.
> Would there b potential problems with that?
>
>
> Dwayne J. LaFave
>
> 605-854-3151 (H)
> 605-860-1650 (C)
>
> _______________________________________________
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> Aeronca at westmont.edu
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>



-- 
John (poobah) Rodkey - N9361E 11AC at Goleta
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