What is the datum in weight and balance terms?

• A. The fixed reference point from which all horizontal distances (arms) are measured.
• B. The weight of the airplane.
• C. The center of gravity.
• D. A random point on the fuselage.

Answer: (C)

The datum is the fixed reference point used for weight and balance calculations. It’s not a physical part of the airplane and doesn’t move with loading. Distances from this point to where weights act are called arms, and each weight’s moment is found by multiplying the weight by its arm. The center of gravity is the actual balance point of the aircraft, determined by summing all moments and dividing by the total weight, with all measurements referenced to the fixed datum. In short, the datum provides a constant reference for all measurements, while the center of gravity is the resulting balance location.