Index =W*(Sta - Ref.Sta)/C + K
Stock standard IU equation for a trimsheet as we have discussed before.
% MAC =( 100*C.(I-K) )/(MAC*W) + 100*(Ref.Sta - LEMAC)/(MAC)
This equation follows by some manipulation .... but it's a lot easier just to read the %MAC off the envelope overlay grid ie enter IU and W and read off %MAC. This %MAC equation is quite unnecessary and not even used for plotting the grid in the design phase of the trimsheet (although it certainly could be). As you will always work through a fuselage station for CG, it is a lot easier just to use the general basic equation -
%MAC = (CG - LEMAC)*100/MAC
What concerns me is that you are making something very simple into something a lot more complex ... but for no advantage to you.
as I thought it, each company for his each aircraft give LEMAC
I may be misunderstanding your intent here. The LEMAC is provided by the aircraft OEM (in the WBM, AFM, TCDS, etc). Not determined by the operator.
my english is poor and sometimes I don't understand all what you write
that's my fault .. not yours.