What is the purpose of the main spar in an aircraft wing?

The main spar in an aircraft wing serves a critical role in ensuring the structural integrity and support of the wing. It is the primary load-bearing component and is designed to distribute the forces experienced during flight, such as lift and aerodynamic loads. By transferring these loads from the wing's surface to the aircraft's fuselage, the main spar helps to maintain the overall shape of the wing, preventing deformation and ensuring that the wing can effectively generate lift. Without a strong and properly designed spar, the wing would be unable to withstand the stresses of flight, which could lead to structural failure. This function is essential for the safety and performance of the aircraft, making it a pivotal component in wing design.

The other options, while they address important aspects of wing performance and functionality, do not capture the primary purpose of the main spar. For example, while flexibility can be beneficial, it is not the spar's main function. Similarly, drag reduction and roll control relate to other design elements and control surfaces of the aircraft rather than the spar itself.