When the CG is moved aft, what is the general effect on stability?

• A. The aircraft becomes more stable.
• B. The aircraft becomes less stable.
• C. The aircraft stays the same.
• D. It varies based on other factors.

Answer: (B)

When the center of gravity (CG) is moved aft in an aircraft, the general effect is a reduction in stability. This occurs because the aerodynamic center of the wing and the center of gravity are crucial in determining the stability of the aircraft. When the CG is located further back, the distance between the CG and the aerodynamic center increases.

In this scenario, if the aircraft experiences a disturbance, the moment generated by that disturbance acts to further increase the angle of attack, which can lead to a loss of control or even an increased risk of stalling. Aircraft with an aft CG may also exhibit increased sensitivity to control inputs, making them feel less stable during flight.

As a result, the aircraft becomes more prone to oscillations and requires more precise pilot inputs to maintain control, emphasizing a significant reduction in overall stability.

In contrast, moving the CG forward usually enhances stability by providing a greater restoring moment when the aircraft is disturbed from its flight path, making it predictable and easier to handle. The statement regarding varying effects based on other factors does apply in some contexts, but generally, moving the CG aft consistently leads to decreased stability.