"BT" wrote in :

Bertie... perhaps I miss spoke..
correct.. not 85% MAC... but 85% towards the AFT CG limit..

Ah, 85% of the range, you mean?

OK.

In airliners we actually go for the aft limit, if possible. There's a
double benefit from this. One, the drag from the stab is lowered and the
effective weight of the aricraft is also lowered. But perhaps more
importantly, the lower wing load resulting from the aft CG allows a wider
buffet margin and therfore a higher allowable cruising level.
One of the reasons that manufaturers want FBW systems is to permit flying
with what would be an extreme aft CG for a standard airplane. This allows
almost silly cruising levels at very, very low buffet margins to be had.
The reason of course is the higher you go, the more fuel and $$$$ you save.



Bertie