Well the problem is knowing what's in the tanks and what comes out.
In a GA context, there really are three scenarios:
a) fly your own a/c, ideally equipped with a good fuel-flow meter. This is the ideal situation, as you know your machine AND have the instrumentation to check what it is actually up to. Great, seems to be IO's circumstance.
b) fly one or two club a/c regularly, therefore get to know them well and develop empirical data. Some
may even have a flow meter.... mostly (with exceptions) my situation.
c) fly a wide variety of spamcans w/o flow meters. Now we're down to guesswork or book numbers with all the associated problems. This, alas, probably describes a good portion of GA flying
My personal approach is to err on the side of caution and I usually adopt an approach similar to Fouga's - also because I seem to be in a similar situation, as mm-flynn points out.
Leaves us with the question on how to plan a maximum-range flight. My - short - answer would be: don't with an unfamiliar a/c unless it is equipped with a good (and working) fuel flow meter. I've had to do this a number of times, and my approach is to do a couple of short(ish) hops and see what
really happens. Most of the time you can start a long journey by doing a few short legs first, figure out what's what and then go about the long-haul (well, in GA terms) planning.
Now seriously drifted from PA28 fuel management
