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An aircraft with a two wheel nose gear and four main wheels rests on the ground with a single nose wheel load of 7250 N and a single main wheel load of 60 000 N. The distance between the nose wheels and the main wheels is 10 metres. How far is the Centre of Gravity in front of the main wheels?
  • A
    57 cm.
  • B
    93 cm.
  • C
    108 cm.
  • D
    176 cm.

Floor loads and aircraft weights are occasionally given in Newtons (N). A Newton is a unit of a force and 1 kg equates to 9.81 N, or roughly 10 N.

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.

Assuming that the datum is at the nose gear, the CG is: CG =Total Moment / Total Weight = [(2 x 7 250 N x 0 m) + (4 x 60 000 N x 10 m)] / 254 500 N = 2 400 000 N.m / 254 500 N = 9.43 m aft of the nose wheel.

Thus, the CG is: Distance between the nose wheels and the main wheels - CG position (distance from datum) = 10 m - 9.43 m = 0.57 m or 57 cm in front of the main wheels.

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