An aeroplane has a mass of 1780 Ib and a total moment of 168 100 in-Ib aft of the datum. Fuel with a mass of 510 lb and an effective arm of 9.5 ft aft of datum is then loaded. Calculate the CG position with the fuel added.
Moment is the turning force created by the mass acting over a distance or arm and is calculated by multiplying the arm by the mass or weight:
- Moment = Arm x Mass or Weight.
Moments aft of the datum are by convention positive and moments forward of the datum are negative.
The Centre of Gravity (CG) can be found by adding all the moments and then dividing the total moment by the total mass or weight:
- CG =Total Moment / Total Weight.
The fuel arm of 9.5 ft = (9x12) + 6 = 114 in.
| Mass (lbs) | Arm (in) | Moments (in-lb) | |
| Aircraft | 1780 | - | 168 100 |
| Fuel | 510 | 114 | 58 140 |
| Total | 2290 | 98.79 | 226 240 |
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