What type of measurement is used to designate the arm in weight and balance computation?

• A. Distance
• B. Weight
• C. Time
• D. Force

Answer: (A)

The arm is a distance measurement. In weight and balance, the arm designates how far the weight is from the reference datum along the aircraft’s longitudinal axis. This distance is used to compute the moment by multiplying the weight (a force) by the arm (distance). The moment helps determine the aircraft’s center of gravity when summed across all loads. For example, a 1,500 lb item located 20 inches from the datum produces a moment of 30,000 inch-pounds. The key point is that the arm measures how far the weight is from the reference point, not how much the weight is, how long it takes, or how hard the force is.