In preparing weight and balance, the 'arm' value is essential for calculating what?

• A. Loaded weight.
• B. Aircraft speed.
• C. Moment about the datum.
• D. Altitude.

Answer: (C)

In weight and balance, the arm lets you convert a weight into a moment by multiplying the weight by its distance from the reference datum. This moment about the datum is what you sum for all items to get the total moment, and that total moment together with the total weight determines the aircraft’s center of gravity.

So the arm is essential because it directly produces the moment about the datum. The other quantities—loaded weight is just the total weight, and aircraft speed or altitude aren’t calculated from weight distribution in the balance process.