What is a moment in weight and balance calculations?

• A. Moment = weight × arm; sum of moments divided by total weight gives the CG position
• B. Moment = weight × speed
• C. Moment = arm × speed
• D. Moment = weight × altitude

Answer: (A)

In weight and balance, the moment is the rotational effect of a weight about the reference point (datum). It’s calculated by multiplying the weight by its arm, where the arm is the distance from the datum along the aircraft’s longitudinal axis. So, moment equals weight times arm. To find the overall effect, you sum all individual moments and then divide by the total weight to get the center of gravity (CG) position. This gives you the point where the total weight can be considered to act.

That’s why this option is correct: it states moment is weight times arm, and that CG is found by dividing the sum of moments by the total weight. The other ideas—moment as weight times speed, arm times speed, or weight times altitude—don’t reflect how the rotational effect about the datum is determined; speed and altitude don’t define a moment in weight and balance calculations.