What primarily causes twisting or torsional loads on the wing?

The primary cause of twisting or torsional loads on the wing is shifts in the center of gravity and control surface deflection. When the center of gravity moves, particularly in a lateral direction, it can lead to uneven distribution of weight across the wings. This uneven load can generate torsional forces that affect the structural integrity of the wings.

Additionally, the deflection of control surfaces such as ailerons can create asymmetrical lift when the aircraft is maneuvering. This results in differing aerodynamic forces on either side of the wing, thus increasing the twisting loads. These load variations are critical to understand as they can influence flight dynamics and overall aircraft performance, which is essential during mass and balance considerations.

In contrast, factors such as differences in fuel weight mainly affect overall weight rather than causing twisting loads; changes in flight attitude relate primarily to lift and drag forces, and excessive passenger load contributes to increased weight without specifically inducing torsional stress. Understanding the dynamics of center of gravity and control surface effects enables pilots and engineers to anticipate and manage the forces acting on the aircraft structure more effectively.