What is the result of an aft shift of the centre of gravity on static longitudinal stability?

An aft shift of the center of gravity (CG) in an aircraft has a significant impact on static longitudinal stability. When the CG moves further aft, the moment arm between the CG and the center of lift becomes shorter. This reduced distance leads to decreased restoring forces when the aircraft experiences pitch disturbances.

In practical terms, when an aircraft's CG is located towards the rear, the aircraft tends to become less stable. This is because the aircraft's natural tendency to return to its original attitude after a disturbance is diminished. Therefore, there is a reduced stability effect as the aircraft may enter into a state where it requires a greater control deflection to counteract the disturbances, which in turn could lead to greater control sensitivity.

The consequence of this condition is that the control authority required to maintain level flight or recover from a pitch change will be affected. As such, with reduced stability, pilots may need to engage in more pronounced control inputs to maintain stability, which is represented as a reduction in the amount of control deflection required under more stable conditions.

Thus, the result of an aft shift of the center of gravity leads to an overall reduction in stability and the control effort required to manage the aircraft's attitude may not decrease proportionally, aligning with the choice selected.