What is the orientation of the arms when weighing an airplane to obtain the CG?

To determine the center of gravity (CG) of an airplane, the arms used during the weighing process must be oriented parallel to the centerline of the aircraft. This orientation is crucial because it ensures that the measurements taken reflect the true distribution of weight along the length of the aircraft. When the arms are parallel to the centerline, it allows for a precise calculation of the moments used to find the CG, which is essential for safe aircraft operation and stability.

In some instances, if the arms were not parallel to the centerline, the weight distribution could yield inaccurate results, potentially leading to miscalculations in the CG. Maintaining this parallel orientation helps in accurately applying the weight and distance measurements needed to compute moments about the reference datum, ensuring that the airplane is balanced properly for flight.