What determines whether the moment value is preceded by a plus or minus sign in aircraft weight and balance calculations?

• A. The direction of gravity.
• B. The engine power setting during weighing.
• C. The result of a weight being added or removed and its location relative to the datum.
• D. The color of the aircraft.

Answer: (C)

In weight and balance, the sign in front of a moment comes from how the weight’s location relates to the datum and whether you’re adding or removing that weight. Moment equals weight times arm, and the arm is defined with a direction from the datum. Typically, weights located forward of the datum contribute a different sign than those located aft. When you add weight, you’re adding that signed moment; when you remove weight, you’re effectively subtracting it. So the plus or minus in front of a moment value is determined by both where the weight sits relative to the datum and whether the calculation is including that weight (adding) or excluding it (removing). The other options don’t influence the sign.