• Moment is the turning force created by the mass over a distance or lever arm: Moment = Mass x Arm

Remember that, by convention, the items aft of the datum have a positive arm, and consequently a positive moment, and those which are forward of the datum have a negative arm and moment.

Thus, since the nose landing gear jack point is forward of the datum (main landing gears jack points), both its arm and moment will be negative.

Generally, the Centre of Gravity (CG) can be found by adding all the moments and then dividing by the total mass: CG = Total Moment / Total Mass.

The Total mass of the aircraft is: 4 350 kg + (2 x 15 005 kg) = 34 360 kg

and its Total Moment: [4 350 kg x (-12.2 m)] + [(2 x 15 005 kg) x 0] = - 53 070 kg.m.

Therefore, the CG position of the BEM will be: - 53 070 kg.m / 34 360 kg = -1.54 m.

The minus (-) symbol implies that the CG position is 1.54 m forward of the main landing gears.