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Refer to figure.
A helicopter is loaded as shown in the table, calculate the ZFM lateral Centre of Gravity (CG) position given the lateral datum is the rotor mast.

  • A
    0.69 in Right
  • B
    0.84 in Right
  • C
    0.69 in Left
  • D
    0.49 in Left

Refer to figure.
To calculate the position of the Centre of Gravity (CG), the mass and the arm of the stations in the helicopter must be known. We can find out the total Centre of Gravity position by adding the total moments and the total masses on board, thereafter, using the formula.

  • Moment = Mass x Arm

The question is asking for the lateral CG at Zero Fuel Mass (ZFM) therefore, the fuel is not included in our calculation. The figure shows the calculations done to find all the individual moments thereafter, adding them together and dividing by the total mass.

  • Total moment = 2 797.25 + (-5 998.4) = -3 201.15
  • Total mass = 4 670 kg

Calculate the CG position by:

  • Total Arm = Total Moment / Total Mass
  • Total Arm = -3 201.15 / 4 670 kg = -0.69 in

Answer: 0.69 in Left of the datum.

NOTE:
The negative value of the arm shows that the CG is laterally to left of the datum and longitudinally forward of the datum. This is a standard way of calculating the CG in aviation.

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