| A point near the centre of the aeroplane. It moves longitudinally as masses are added forward and aft of its location. |
| The point through which the sum of the mass values (of the aeroplane and its contents) is assumed to act vertically. |
| A variable point, that is dependent on the load distribution for its location, from which all balance arms are measured |
| A fixed point from which all balance arms are measured. It may be located anywhere on the aeroplane's longitudinal axis or on the extensions to that axis. |
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