What is the primary factor that affects induced drag?

Induced drag is primarily influenced by the angle of attack due to its direct relationship with lift production. As the angle of attack increases, the lift generated by the wings increases, but this also leads to a rise in induced drag. This type of drag arises from the creation of lift and is a byproduct of the wing generating vortices at the tips, which occurs as the angle of attack rises. Consequently, higher angles of attack ultimately lead to increased induced drag until a certain point, after which stall may occur.

While velocity, wing surface area, and altitude also have roles in aerodynamics, they do not directly determine the relationship between lift and its associated induced drag as the angle of attack does. For instance, increasing the velocity of the aircraft generally reduces the angle of attack needed for a certain amount of lift, which could decrease induced drag. Meanwhile, increasing wing surface area would increase lift but, under certain conditions, could also result in a higher induced drag. Altitude influences air density, which indirectly impacts both lift and drag, but it is the angle of attack that has the most immediate and compelling effect on induced drag.