What effect does moving the Center of Gravity (CoG) aft have on an aircraft's stability?

When the Center of Gravity (CoG) is moved aft (towards the tail), it decreases the stability of the aircraft. This is primarily because the aircraft's tail, which provides stability and control, becomes less effective in counteracting pitching moments. The tail's effectiveness is derived from its ability to generate downforce, which is essential in maintaining controlled flight.

When the CoG is moved aft, it tends to increase the risk of the aircraft entering a nose-up attitude. This is because with a more aft CoG, the moment arm from the aerodynamic center to the CoG increases, making it easier for any perturbation (like turbulence) to cause the nose to pitch up. The result is that the aircraft requires more precise control inputs to maintain level flight and can become more difficult to handle.

This shift can lead to a condition known as "pitch sensitivity," where small control inputs result in larger than expected changes in pitch attitude. In extreme cases, if the CoG is too far aft, the aircraft may even become uncontrollable in pitch, further emphasizing the critical nature of maintaining proper balance and stability through appropriate CoG positioning.