"Usable" means usable in EVERY flight attitude. The "unusable" fuel can
be used in SOME flight attitudes, obviously some of that unusable fuel
could be used in the specific flight attitude in which you were at the time.


True, but so what?

Did you notice I was putting 20.8 gallons in what is supposed to be a 20
gallon tank? My point is that POH are not completely accurate in regards
to fuel managment, and that you don't know how inaccurate they are for
YOUR particular plane until you run a tank dry.

So there are different values of "dry". When you run a tank "dry" that
doesn't mean there's no gas in it. The problem isn't that the POH isn't
accurate (and I make no statements about its accuracy), but rather, that
"empty" isn't a yes or no thing.

The fuel has to be able to flow until you reach the "unusable fuel".
After that, the fuel =might= flow in certain attitudes (and almost
certainly will, to some extent, in some of them). So, if you are trying
to measure "usable fuel" this way, you've run the tank =more=than= dry
when the engine quits, but you don't know how much more than dry you've
run it, because that depends on the flight attitude when you did that.

And if you're trying to measure =total= fuel, running a tank dry doesn't
mean it has no fuel in it.

Jose
--
Quantum Mechanics is like this: God =does= play dice with the universe,
except there's no God, and there's no dice. And maybe there's no universe.
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