Center of gravity (CG) is defined as the point at which the airplane would balance if suspended at that point. It is the mass center and may be expressed in which units?

• A. Inches from the reference datum, or percent MAC
• B. Feet from the tail
• C. Meters from the cockpit
• D. Percent wing area

Answer: (A)

The CG is the balance point along the airplane’s longitudinal axis, essentially the mass center, and its location is tied to a fixed reference point called the datum. In practice, the CG can be expressed as a distance in inches from that reference datum or as a percent of the mean aerodynamic chord (MAC) of the wing. Using inches from the datum gives a direct linear location along the aircraft’s body, while expressing it as a percent MAC normalizes the position to the wing’s geometry, making it easier to compare configurations or ship types. Other units like feet from the tail, meters from the cockpit, or percent of wing area don’t align with the standard weight-and-balance conventions, so they aren’t used for CG specification.