When the aircraft is properly prepared for weighing, roll it onto the scales, and level it. The weights are measured at three weighing points: the two main wheel points and the nosewheel point. The empty weight and empty weight CG (EWCG) are determined by using the following steps with the results recorded in the weight and balance record for use in all future weight and balance computations.
- Determine the moment index of each of the main-wheel points by multiplying the net weight (scale reading minus tare weight), in pounds, at these points by the distance from the datum, in inches. Divide these numbers by the appropriate reduction factor.
- Determine the moment index of the nosewheel weighing point by multiplying its net weight, in pounds, by its distance from the datum, in inches. Divide this by the reduction factor.
- Determine the total weight by adding the net weight of the three weighing points and the total moment index by adding the moment indexes of each point.
- Divide the total moment index by the total weight and multiply the result by the reduction factor. This gives the CG in inches from the datum.
- Determine the distance of the CG behind the leading edge of the mean aerodynamic chord (LEMAC) by subtracting the distance between the datum and LEMAC from the distance between the datum and the CG. [Figure 1]
- Determine the EWCG in percentage of MAC (percent MAC) by using the formula in Figure 2.
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| Figure 1. Determining the distance of CG |
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| Figure 2. Determining the EWCG in percent MAC |
