The question states that the basic arm of 3.00 m is at 20% MAC.
MAC length is 2 m, so 20% of this is 0.4 m.
Subtracting 0.4 m from 3.0 m give a MAC Leading Edge of 2.6 m.
Item Mass Arm Moment (mass x Arm)
BEM 1200 kg 3 m 3600 kgm
Pilot + Pax 160 kg 2.5 m 400 kgm
Fuel 95 kg 3 m 285 kgm
Total 1455 kg 4285 kgm
C of G position = Moment / Mass = 4285 / 1455 = 2.945 m
Subtracting MAC Leading Edge position gives C of G at 2.945 – 2.6 = 0.345 m aft of MAC Leading Edge.
To convert to % MAC use 0.345 m / 2 m x 100% = 17.25% MAC
The final question states that g = 10 m/sec.
This means that 1 kg = 10 Newtons.
So you can now convert the kgm into Nm by multiplying by 10. But you do not need to do this to answer the question.
Mass of 450 is loaded at a station 8.0 behind centre of gravity and 6.8 behind the datum. (Assume g=10 m/sec squared). the moment for that mass used for loading manifest is?
3060kgm
30600kgm
Moment = mass x arm from datum
Moment = 450 kg x 6.8 m = 3060 kgm
Note that the fact that the load is 8 m behind the CG is not relevant to this question.
Last edited by keith williams; 4th March 2014 at 13:54.
Reason: Misread question