Seems a simple enough formula, what you need is the "arm" (distance from
center of gravity). I presume that information is unavailable in your
tables? It may take some legwork to build your own calculator, but the
starting point could be he
http://www.airweb.faa.gov/Regulatory...e?OpenFrameSet
Which is a page from which you can locate the Type Certificate Data Sheets
(TCDS) for virtually every aircraft made. The links on that page take you to
alphebetized lists for manufacturers which in turn allow you to choose
aircraft made by them. Other options for 'searching' are provided also.

You then could make a list of arm lengths for various points in the aircraft
and simply fill in the weight for a point to obtain its moment.

Hope this helps some.

"Doug" wrote:

Hi everyone,

I have two lists of data - one showing fuel weights at 67 lb increments from
0 up to 3645 lbs (sometimes at different increments for special weights) and
the other showing a corresponding moment (weight times the distance of that
weight from the center of gravity). These come from an aircraft weight and
balance manual. As you can tell, for a specific fuel weight not listed in
this manual, one has to interpolate between two listed values in order to
estimate a moment value for that unlisted weight.

I'm trying to come up with a very precise formula using excel that will
accurately estimate the moment for a specific fuel weight, but the arm
(distance from the cg) varies for each fuel weight in a non-linear manner.
Using a trendline from a chart, the closest R^2 value I can come up with is
0.999811266 (which still yields up to a 5% error).

Is there any excel tool or trick that can help revise this formula and make
it more precise? Thanks for any help.