What is meant by the datum that is used for weight and balance computations?

• A. A readily identified reference chosen by the aircraft manufacturer from which all longitudinal locations on the aircraft are referenced.
• B. A mathematical reference line defined by the maintenance manual.
• C. The aircraft's forward-most point.
• D. The center of gravity.

Answer: (D)

The datum is a fixed reference line or point chosen by the manufacturer from which all weight and balance measurements are made. Each item’s distance from this datum (its arm) is used to calculate moments (weight times arm). By summing all moments and dividing by the total weight, you determine the aircraft’s center of gravity. The center of gravity itself is the actual balance point of the aircraft, not the reference used for calculations. So the datum serves as the consistent reference for locating weights, not the CG.