CG Movement


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    Mark Mansfield

    Greetings to all


    I have a question and needs some help to answer it please:


    Aircraft AUW = 240 000Kg. An extra 10 000Kg of freight is added to hold , arm +24m.

    This moves the CG 2m aft.  

    The original arm of the CG was?



    Anthony Foxcroft

    Hi Mark,

    To answer this question we will use the formula:

    change of mass / new total mass = change of CG / distance from mass to old CG

    re-arranged we get:

    distance from mass to old CG = (new total mass x  change of CG) / change of mass

    = (250000 kg x +2 m) / 10000 kg

    = 50 m.

    By convention, arms aft of the datum are positive and arms forward of the datum are negative.

    The CG moved aft (or in the +ve direction) when the mass was added, so this tells us that the mass must have been added aft of the original CG, or put another way, the original CG is forward (or in the -ve direction) of the mass that was added.

    From the arm of where the mass was added (+24) we must move forward (-ve) 50 m, so the original CG must have been -26 m, or 26 meters forward of the datum.

    Mark Mansfield

    Thank you Anthony for the detailed explanation.



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