In weight and balance, what is an arm?

• A. Weight
• B. Load factor
• C. Distance from the datum
• D. Moment

Answer: (C)

An arm is the distance from the aircraft’s datum to where a weight acts along the aircraft’s length. It’s the lever arm used to calculate the moment by multiplying by the weight. The moments of all items, divided by the total weight, determine the center of gravity. So the arm is about location relative to the datum, not the weight itself, not the load factor, and not the moment.