Nothing wrong with the Airbus equation. What do you see as the difficulty and we can discuss it to remove the concern ?
I don't want to say Airbus equation is wrong, but i don't understand it.
I don't understand why, the same equation is able to compute %Mac correctly for one aircraft and isn't able to compute this %mac for an other.
The best way would be to meet pilot.
To explain the reason about my research, I created software which is able to compute the aircraft loading , like gaetan software.
I found Harm about Hold (in airbus doc) and to determine Index about Cabin I use trim sheet about aircraft, the first results is very good, My Index ZFW,TOW,and LDW are equal with values which are compute by gaetan (airfrance software), The only equation I don't have is equation %Mac,
So i search on Web, generic equation or not,which is able to compute %Mac for any aircraft, when I am able to compute Index value of ZFW,TOW,and LDW
thank you much for your understanding and for your help