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Determining either fwd limit or normal flow chart

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(@user1396)
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Joined: 16 hours ago
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Topic starter  

Hi Guys
i am attempting Page 5.54 ex 5.12 q1 to Q5 once i get going i am okay i guess with Q1 and Q2 i notice after looking at the answers you are supposed to use the fwd limit equation which i know. i am just struggling to determine whether a question requires the fwd limit method to work out required c of g or we use regular rear c of g 2680mm i hope my question makes sense



   
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Bob Tait
(@bobtait)
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Joined: 16 years ago
Posts: 2538
 

You might find it useful to have the Echo centre of gravity envelope beside you when you work the question. The question will usually give you a present weight and moment. Even though you are not going to use the envelope to solve the question, it is often useful to at least roughly check given weight and moment on the envelope - you don't have to be precise, just check the current weight and moment - no need to even use a pencil, just use your finger tip to get an approximate point of the envelope.

When you have done that, check what the examiner is asking you to do. What compartment are you adding to or subtracting weight from? Which compartments are you shifting weight between? Decide whether that will move the centre of gravity forward or aft.

If you know roughly where you are now, and you can see whether the centre of gravity is going to move forward or aft it is much easier to see which limit you are going to encounter. If it's the aft limit, you can always use the flow chart. If it's the forward limit you can use the flow chart only if you are shifting weight. Otherwise use the two-point method.

If you haven't been given a weight, you will always be given a moment change required. In that case, use the formula 'change of moment ÷ difference in compartment arms."



   
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(@user1396)
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Joined: 16 hours ago
Posts: 2
Topic starter  

Dear Bob

Thank you so much for your response a true pro at your subject matter your words just made sense very grateful for the quick response



   
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