Originally Posted by Linktrained
I assume that the ballast carried in a glider will normally shift the C. of G. aft, causing the tailplane to provide lift, hence lowering the total weight carried by the wings, the actual "wing loading".
I'm not sure I can totally agree with that analysis. If the ballast tank is in the tailplane (as in the A330 for example) the weight of the ballast is carried by the tailplane. Yes, the C. of G. moves aft, but the lift provided by the wing does not change when adding ballast in the tailplane. Since the tailplane normally provides negative lift, the benefit of moving the C. of G. aft (e.g. by transfer of fuel from the wing tanks to the tailplane in the A330) lies in the reduction of that negative lift. If the ballast is between the wing and the tailplane, then part of its weight will be carried by the wing and the remainder by the tailplane.