What causes a spin in an aircraft?

A spin occurs when an aircraft enters a condition of uncontrolled rotation about its vertical axis, and this phenomenon is primarily caused by an asymmetrical stall, where one wing is stalled more than the other. When the aircraft is in a stall, the wing that loses lift first (or experiences a greater degree of stall) starts to drop, causing the aircraft to roll. As the wing descends, the other wing can continue to generate some lift, thereby exacerbating the roll and increasing the yaw toward the stalled wing due to differential drag.

This yawing motion contributes to the spin, as the aircraft rotates around its center of gravity. The stalled wing’s loss of lift and increase in drag lead to a spiraling descent, which defines a spin. Understanding this dynamic is crucial for pilots because recovering from a spin requires specific actions to restore control, including the application of rudder and aileron inputs to counteract the adverse yaw and roll.

While other options may seem plausible, they do not correctly describe the mechanics involved in spin initiation. For example, equally stalled wings would lead to a straight drop rather than a spin, solely stalling the tail does not generate the necessary yaw, and a malfunction of elevator control may affect pitch but does not directly cause