What is the aerodynamic term for the moment that measures tendency to rotate about the center of gravity?

• A. Moment
• B. Stability
• C. Drag
• D. Lift

Answer: (A)

Rotational tendency about the center of gravity is described by the aerodynamic moment. When aerodynamic forces like lift and drag act at a distance from the CG, they create a turning effect around that point, which we call the moment. This moment tells you whether the aircraft would nose up or nose down if it were free to rotate about the CG. In pitch, this is often referred to as the pitching moment about the CG.

Stability, by contrast, is about how the aircraft responds over time after a disturbance—whether it returns to equilibrium or not—rather than the immediate tendency to rotate. Lift and drag are forces themselves; they contribute to the moment, but they are not the measure of rotational tendency about the CG. Thus, the term that directly names the tendency to rotate about the center of gravity is the moment.