What is meant by moment in the computation of weight and balance?

• A. A force that tends to cause rotation. It is the product of the weight of an object in pounds and the distance of the object from the datum in inches.
• B. A force equal to the object's weight.
• C. The distance from the datum.
• D. The sum of all forces.

Answer: (A)

Moment is the rotational effect a force has when it acts at a distance from a reference point. In weight and balance, every item has a weight (a downward force) and an arm (the distance from the datum to where the item sits). The moment is the product of those two: weight in pounds times the arm in inches, giving moment in pound-inches. This is the quantity you use to see how much each item tends to rotate the aircraft about the datum, and to determine the overall center of gravity. To find the aircraft’s CG, you multiply each item's weight by its arm to get its moment, add up all those moments for a total moment, then divide by the total weight. The distance alone doesn’t tell you how the aircraft will rotate, and the sum of forces would just be total weight, not how that weight is distributed.