In terms of stability, moving the CG aft tends to cause which outcome?

• A. Moving the CG aft reduces stability
• B. Moving the CG aft increases stability
• C. No change in stability
• D. Stability varies with airspeed

Answer: (A)

Longitudinal stability hinges on the center of gravity being ahead of the neutral point, so the aircraft has a restoring tendency after a pitch disturbance. When the CG moves aft, that restoring moment shrinks because the mass is closer to the pivot, and the tail must work harder to return to trim. As the CG gets nearer the neutral point, the static margin decreases, making the airplane less stable in pitch and more prone to continuing a disturbance rather than dampening it. The tail may become more effective for control at an aft CG, but it doesn’t offset the loss of stability. So the overall effect is reduced stability.