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A twin-engine aeroplane has an actual mass of 6 063 kg. Its CG is located at 2.7 m aft of the datum. How much mass must be transferred from a cargo compartment 1.2 m aft of the datum to compartment 4.1 m aft of the datum to establish a CG 2.8 aft of the datum?
• A
10 kg.
• B
148 kg.
• C
209 kg.
• D
510 kg.
The question wants you to calculate the load which has to be moved from cargo compartment 1.2 aft of datum to compartment 4.1 m aft of datum, so that the CG will move to 2.8 m aft of the datum:
• Initial CG: 2.7 m
• Final CG: 2.8
• Change in CG: 0.1 m
• Total distance moved: 4.1 m – 1.2 m = 2.9 m
Formula:
Total Mass moved / Total Mass = Change in CG / Total Distance Moved

Total Mass moved = (Change in CG / Total distance moved) x Total Mass
Total Mass moved = (0.1 m / 2.9 m) x 6 063 kg
Total Mass moved = 209 kg
Alternatively:
1. Calculate the current total moment:
Moment = Total Mass x arm
Moment = 6063 kg x 2.7 m = 16 370.1 kgm

2. Calculate the final moment (after the mass has been moved):
Moment = 6063 kg x 2.8 m = 16976.4 kgm

3. Determine the additional moment required (difference between final and initial moment):
16976.4 kgm - 16 370.1 kgm = 606.3 kgm

4. Total distance moved:
4.1 m – 1.2 m = 2.9 m

5. Calculate the required mass to increase the total moment by 606.3 kgm:
606.3 kgm : 2.9 m = 209 kg

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