Which of the following statements about the effect of rearward center of gravity on stability is true?

• A. Produces no change in stability.
• B. Increases stability about the vertical axis.
• C. Reduces stability about the vertical axis.
• D. Has no effect on stall speed.

Answer: (C)

The question is testing directional stability, or stability about the vertical axis. A rearward center of gravity reduces this stability. When the CG moves toward the tail, the distance between the CG and the tail’s restoring moment arm decreases, so the tail’s ability to produce a yawing (restoring) moment in response to sideslip is reduced. That means yaw disturbances are less damped and can grow, making the aircraft less stable directionally. So rearward CG indeed reduces stability about the vertical axis.

The other statements don’t fit: moving the CG aft does not increase directional stability, and saying there’s no change in stability is incorrect. The note about stall speed isn’t the focus here, since the question targets directional stability rather than stall characteristics.