Definition
The aerodynamic and control inputs that cause an aircraft to enter or remain in a spin: a stalled wing combined with yaw. Typical pro-spin forces include continued aft elevator (which keeps the wing stalled) and rudder deflection in the direction of the spin (which sustains the yaw and the asymmetric lift between the two wings).
Plain English
Anything the airplane is doing — or the pilot is holding — that keeps it stalled and yawing, which is what makes a spin start and continue.
Context Anchor
Seen in spin awareness and spin recovery discussions, especially when explaining why the wrong control inputs can delay recovery.
Derivation
"Pro-" comes from Latin meaning "in favor of" or "supporting." Pro-spin forces are the inputs and aerodynamic effects that support, or work in favor of, the spin — the opposite of anti-spin forces, which are used to recover.
Why Pilots Care
Recognizing these forces lets the pilot apply the correct recovery inputs to stop the spin promptly and avoid altitude loss.
Grounding Statement
In a spin, some forces are helping the rotation continue, and recovery is about removing or overcoming those forces.
Intuition Check
Do not read “pro-spin” as meaning “professional spin” or “good spin.” Here, “pro” means “supporting” the spin, so pro-spin forces are the forces that help the spin continue.
Example Sentence 1
Holding full aft elevator and right rudder are the classic pro-spin forces during a developed upright spin.
Example Sentence 2
At high power settings, engine torque becomes a significant pro-spin force in single-engine aircraft.