The CG of a loaded airplane can be moved into its allowable range by shifting passengers or cargo or by adding temporary ballast.

If a repair or alteration causes the aircraft CG to fall outside of its limit, permanent ballast can be installed. Usually permanent ballast is made of blocks of lead painted red and marked “Permanent Ballast—Do Not Remove.” It should be attached to the structure so that it does not interfere with any control action and attached rigidly enough that it cannot be dislodged by any flight maneuvers or rough landing.

Two things must first be known to determine the amount of ballast needed to bring the CG within limits: the amount the CG is out of limits, and the distance between the location of the ballast and the limit that is affected.

If an airplane with an empty weight of 1,876 pounds has been altered so its EWCG is +32.2, and CG range for weights up to 2,250 pounds is +33.0 to +46.0, permanent ballast must be installed to move the EWCG from +32.2 to +33.0. There is a bulkhead at fuselage station 228 strong enough to support the ballast.

To determine the amount of ballast needed, use the formula in Figure 7-13.

Ballast needed = (1,876 × 0.8) / (228 – 33)

= 1500.8 / 195

= 7.7 pounds

A block of lead weighing 7.7 pounds, attached to the bulkhead at fuselage station 228, moves the EWCG back to its proper forward limit of +33. This block should be painted red and marked “Permanent Ballast—Do Not Remove.”