In flight dynamics a spin is a special category of stall resulting in autorotation about the aircraft's longitudinal axis and a shallow, rotating, downward path approximately centred on a vertical axis. Spins can be entered intentionally or unintentionally, from any flight attitude if the aircraft has sufficient yaw while at the stall point.
In a normal spin, the wing on the inside of the turn stalls while the outside wing remains flying. It is possible for both wings to stall, but the angle of attack of each wing, and consequently its lift and drag, are different.
Spin — an aggravated stall and autorotation
The missile-shaped objects on the wingtips of the DH 108 are containers for anti-spin parachutes.
In fluid dynamics, a stall is a reduction in the lift coefficient generated by a foil as angle of attack increases. This occurs when the critical angle of attack of the foil is exceeded. The critical angle of attack is typically about 15°, but it may vary significantly depending on the fluid, foil, and Reynolds number.
Airflow separating from an airfoil at a high angle of attack, as occurs at a stall.
A Schweizer SGS 1-36 being used for deep-stall research by NASA over the Mojave Desert in 1983.