Which axis is primarily affected if an aircraft is out of balance due to rear CG loading?

When an aircraft is out of balance due to rear center of gravity (CG) loading, the primary axis affected is the lateral axis. The lateral axis runs from wingtip to wingtip and is crucial for understanding how an aircraft maneuvers in terms of pitch.

When the CG is shifted rearward, it alters the balance and stability of the aircraft, making it more susceptible to pitch changes. This can result in a nose-up attitude, increased stall speed, and difficulty in controlling the aircraft, particularly during takeoff and landing phases. The aircraft may become more sensitive to elevator control inputs, which could lead to an increased likelihood of uncommanded nose-up or nose-down movements.

The other axes—longitudinal (front to back) and vertical (up and down)—are indeed influenced by the overall weight and balance of the aircraft but are not as significantly affected by a rearward shift in CG as the lateral axis. Understanding the impact of CG on the lateral axis is essential for safe flight operations and proper aircraft handling.