In a balance computation of an aircraft from which an item located aft of the datum was removed, use....

• A. (-)weight X (+)arm (-)moment.
• B. (+ )weight X (+)arm (+)moment
• C. (-)weight X (-)arm (+)moment
• D. (+ )weight X (-)arm (-)moment

Answer: (A)

When you remove an item, you change the weight and the moment about the datum with the sign convention in weight and balance. An item located aft of the datum has a positive arm. Removing that item decreases the total weight, so the change in weight is negative. The corresponding change in moment is the product of the weight change and the arm: negative times positive equals negative. So the proper way to account for this removal is negative weight change times positive arm, giving a negative change in moment. This means the total moment decreases and the CG shifts forward. If the item were forward of the datum or if you were adding weight aft, the signs would differ accordingly.