The three primary axes intersect at the center of gravity at what angle to each other?

• A. 90 degrees
• B. 45 degrees
• C. 180 degrees
• D. 120 degrees

Answer: (A)

The three primary axes are defined to be mutually perpendicular, all crossing at the center of gravity. In aviation, the longitudinal axis runs nose to tail, the lateral axis runs wingtip to wingtip, and the vertical axis runs top to bottom. Because each axis is at right angles to the others, the angle between any pair at their intersection is 90 degrees. That’s why 90 degrees is the correct description here.

The other angles don’t fit because 45 degrees would imply axes aren’t perpendicular, 180 degrees would place two axes along the same line in opposite directions, and 120 degrees would violate the perpendicular relationship among the three axes.