How do you express the CG in inches for most baseline problems?

• A. In pounds per inch
• B. As an inch value from the fixed datum (e.g., 75.0 in, 77.6 in).
• C. In feet from the tail
• D. As a percentage of wing chord

Answer: (B)

The location of the center of gravity is defined as a distance along the aircraft’s longitudinal axis from a fixed reference point called the datum. In most baseline weight-and-balance problems, that distance is expressed in inches from the fixed datum. You treat every item’s weight with an arm in inches, multiply to get a moment in pound-inches, sum all moments, and then divide the total moment by the total weight to get the CG in inches from the datum. This keeps the calculations consistent and gives a precise position you can compare to the allowable CG range.

For example, if the total weight is 2,000 lb and the total moment is 150,000 in-lb, the CG is 150,000 / 2,000 = 75 inches from the datum.

Other expressions don’t fit baseline practice: pounds per inch would imply a density-like value rather than a distance; feet from the tail would only be appropriate if the problem used that reference, which isn’t the standard fixed datum approach; and a percentage of wing chord describes a position along the wing relative to chord length, not the fixed-datum distance used in these problems.