CG location can be expressed as which two forms?

• A. Inches from the reference datum, or percent MAC
• B. Inches from the tail, or percent wing area
• C. Inches from the nose, or percent wing area
• D. Inches from the wing root, or percent wing span

Answer: (A)

CG location is described using two standard references: inches from a fixed reference datum and a percent of the mean aerodynamic chord (MAC). The datum is a fixed point chosen during design to provide a consistent zero for all weight and balance calculations, so measuring the weight distribution from that point gives a precise longitudinal position. Expressing CG as a percent of MAC normalizes the location relative to the wing’s geometry, making it easier to compare different configurations or different aircraft sizes while focusing on stability and controllability along the aerodynamic center line.

Other options describe distance from nose, tail, or wing root, or use percentages of wing area or wing span, which do not represent the longitudinal mass distribution used for balance and stability assessments. For example, if the MAC is 80 inches long and the CG is 40 inches aft of the datum, that CG is at 50% MAC (40/80). This illustrates how the two forms convey the same location in different, standardized ways.