Guidance
Hello John,
I'm going to send you the entire chapter from which I posted the image on post #13. It may be of some help. As you rightly said earlier, there is little or no information on this method calculation, and maybe for a good reason. Modern systems certainly don't use it that often.
The Index equation for adjusted weight makes sense. But the %MAC one needs clarification.
Maybe somebody out there would have a weight and balance manual from a time when this was popular that would explain further. I have a USAir BAe-146 Pilot's handbook that uses this method but no explanation, only a sample. Also I flew a YS-11A from Mid-Pac airlines that used the same. Seemed to be popular in the US circa the 80's and early 90's.
We will crack it I'm sure.