HarryMann,
a) Heavy a/c has more induced drag
b) The drag bucket only applies to wing profile drag, so isn't the whole aircraft Cdo component (watering bucket effect down)
c) Are you sure where the lighter a/c is on the bucket at ToD? Looks to me (without the chore of checking) it may well be right in the middle of bucket!
a) Right, but it (B767 example) also has a 4000 lbf of extra gravity component working as thrust in the opposite direction which also plays a part in this.
b) The fuselage is offcourse also designed to have lowest drag at optimum
cruise lvl (2,5 deg AoA or so). Thats why it isn't symetrical top/bottom.
So changes in AoA away from optimum will give higher fuse drag as well.
c) Right, see attached derived from the B767 diagram.
The difference in RoD don't happen before the low FL300's.
