"Al" wrote in message
...
So, I just run it richer? Or, in the case of a departure, where the
mixture is already full rich, you're saying there will be NO loss of
performance by using a mixture of autogas and alcohol?

No, what he's saying is that if full power with regular gas is 28" at 2650
RPM, then you aren't going to see 28" at 2650 RPM using alcohol or a blend
of alcohol.

In theory, you could calculate the actual percentage horsepower (it will be
less than 100%) based on what RPM you do actually get for a given throttle
setting, and then use a density altitude chart that matches the horsepower
you're actually getting (the chart will actually be slightly conservative,
because you will only have reduced power, rather than all of the negative
effects of high density altitude).

But it seems to me that if an airplane has been certified for use with
alcohol or a blend, it should have the necessary charts for that type of
fuel anyway. If it's not certified for that use, then operating the
aircraft that way wouldn't be advisable in any case, even if you could
determine what power you're getting from the fuel and translate that to a
correct chart to use.

It's good to know what to do in an emergency if you just HAVE to use the
wrong fuel, but just because you can determine the actual performance, that
doesn't mean there aren't other reasons to avoid the fuel.

In other words, this is an interesting academic exercise, but you and -581
had it right in your other posts. Staying on the ground is the correct
day-to-day answer.

Pete