Improper rigging of the elevator trim tab system primarily affects the balance of the airplane about which axis?

The elevator trim tab system is primarily responsible for adjusting and maintaining the pitch attitude of an aircraft, which is crucial for stable flight. When the rigging of the elevator trim tab is improper, it primarily affects the lateral axis, meaning the axis that runs from wingtip to wingtip through the center of gravity. This axis is crucial for controlling the aircraft's pitch and stability in flight.

An imbalance about the lateral axis can create issues such as unwanted nose-up or nose-down attitudes that could lead to difficulty in controlling the aircraft. Proper adjustment of the trim tab helps ensure that the aircraft maintains a level flight attitude without excessive control input from the pilot. Since the elevator trim tab is effectively used to balance the forces acting on the elevator, improper rigging would disrupt this balance, leading to serious handling issues associated with the lateral axis of the airplane.