What is used as a reference point from which all horizontal distances are measured in weight and balance calculations?

• A. The wing centerline
• B. The datum
• C. The center of gravity
• D. The nose

Answer: (B)

In weight and balance, all horizontal distances are measured from a fixed reference point called the datum. The datum is an imaginary point or plane chosen to simplify calculations, and every item’s arm is the distance from this datum to where the weight acts. The moment for each item equals its weight multiplied by that arm. The center of gravity is the balance point of the entire aircraft, found by dividing the total moment by the total weight, so it depends on those arms relative to the datum. The nose or wing centerline aren’t universal reference points for measuring arms in these calculations, so the standard reference used is the datum.