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Weight to shift or add formula

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Tag created the topic: Weight to shift or add formula

Hi, I'm confused with the weight to shift or add formula -Weight to shift or add = (ZFW x (change in CofG)) / Distance between arms-
(ref: Q°50 PPLA#2 )
I'm ok with the formula but I often get the wrong answer to this type of question.
For example (loading charlie) :
-BEW 689kg
-BEW index unit 19579
-Oil 7kg
-Row1 110kg
-Baggage 55kg
-Fuel 140L

What's the max weight in KG that may be carried in row 2 at takeoff?
A. 155kg
B. 90kg
C. 50kg
D.135kg
With the formula above I find 144kg. Correct answer is B. There is obviously something I do wrong, but what is it ???
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  • John.Heddles
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  • ATPL/consulting aero engineer
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John.Heddles replied the topic: Weight to shift or add formula

First, if you run a longhand calculation with your answer, what do you come up with ?

And if you run a longhand calculation with the question's suggested answer, what do you come up with ?

What do you conclude from that exercise ?

And what answer do you suggest is the appropriate answer from those given ?
Engineering specialist in aircraft performance and weight control.
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bobtait replied the topic: Weight to shift or add formula

I'm not sure what your working is. It seems that you have used the weight to shift formula when the question is asking for the weight to add to row 2. Also, remember that the aircraft must be in balance at ZFW as well as at take-off.

Bob
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