Posted for "Matt Hapgood" <hapgoodm94@alum.darden.edu>:

 Marv.  I didn't leave it off my list.  "Usable" fuel was number 2) on my
 list:
 
 "Knowing how much fuel you have in flight requires knowing TWO things: 1)
 Burn rate, and 2) Starting usable fuel amount (and knowing how much fuel a
 specific flight will require adds in many more variables)."
 
 I just didn't feel like repeating the word usable everywhere.  And I am very
 aware of what killed Tony D.  It is a sad reminder that assumptions about
 remaining [usable] fuel can be deadly.  If Tony had measured his fuel flow
 to +/- .001%, it wouldn't have mattered.
 
 Matt
 
 
[Thanks for the clarification, Matt.  I think I should clarify my statement about that accident further as well... Tony was, in fact, aware of a venting issue on that airplane as it had been discussed and factored in prior to his takeoff from Oklahoma.   What he didn't know was that the problem was going to actually remove usable fuel from the tank during the climb to altitude, thus resulting in a lesser amount of actual usable fuel than had been planned for. Either way, the end result was tragically the same.  <Marv>     ]