In the process of weighing an airplane toward obtaining the CG, the arms from the weighing points always extend

• A. perpendicular to the center line
• B. parallel to the center line of the airplane
• C. at a 45-degree angle to the center line
• D. toward the nose

Answer: (B)

In weighing for the center of gravity, the moments that determine CG come from fore‑aft (longitudinal) distances along the airplane’s centerline. Keeping the weighing arms parallel to that centerline ensures each weight’s lever arm is the true fore‑aft distance from the datum, which is exactly what you need to calculate CG accurately. If the arms were not aligned with the centerline—say they were perpendicular—you’d be mixing in lateral distances and wouldn’t get the correct longitudinal moment needed for CG. The arms simply need to run along the fuselage direction; they can point forward or backward, but they must stay parallel to the centerline.