What is induced drag?

Induced drag is specifically associated with the generation of lift. When an aircraft generates lift, it does so by changing the flow of air around its wings. This action creates a pressure difference between the upper and lower surfaces of the wings, resulting in lift. However, this also leads to the formation of vortices at the wingtips, which produce a form of drag. As the angle of attack increases to enhance lift, the induced drag also increases. Therefore, it is closely tied to the aircraft's performance in producing lift—the more lift that is generated, the more induced drag is present.

The other options represent different types of drag or factors that don't directly relate to the concept of induced drag. For example, drag due to aircraft speed refers to parasite drag, which increases with speed. Air temperature can influence air density and subsequently impact performance, but it is not a direct cause of induced drag. Structural drag is related to the actual components of the aircraft itself, rather than the aerodynamic processes involved in lift production.