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Old 13th May 2010, 16:00
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Pugachev Cobra
 
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Weight and Balance "constant" question

Hello there.

So, the way I learned Weight and Balance problems, was that for a given station weight, there was a given moment. And in the POH there are the graphs for making it easier to find it. And in other manuals there are the tables for, i.e. given fuel weight has a given moment.

However I can't work this out: I have some W&B spreadsheets for some light aircraft, and in the fuel field (for example, could also be baggage or pilot and passengers) there is a constant the author used which I think represents the formula for the loading weight / loading moment line graph.

Here is the graph in question:


In this case, a C152, the sheet multiplies the fuel weight (in pounds) with 0.04217.

If I just did the basic multiplication of weight times the arm of the fuel tank station, I wouldn't find the same answer, since it seems that with added weight the arm will gradually increase (or am I wrong?)

What I want to know is where did this "constant" of 0.04217 (in this case) come from?

I know that for different aircraft, and different stations (say fuel, pax, crew, etc.) it would be different constants, but I just can't find it in any manual I come across.

I may be missing something here, assuming something wrong.

Anyone could help me on this?

Thanks

Last edited by Pugachev Cobra; 13th May 2010 at 16:25.
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