Definition
A mechanical spring installed in the elevator control system that exerts a constant tension pulling the elevator down (and therefore pulling the control yoke forward). It supplies an artificial nose-down force to help maintain longitudinal stability when the airplane is loaded with an aft center of gravity, where the horizontal tail alone may not produce enough aerodynamic download to keep the nose from rising.
Plain English
A spring inside the controls that constantly tugs the elevator down a little. This adds a built-in nose-down pull, so the airplane doesn't tend to pitch up on its own when the load is sitting toward the back.
Context Anchor
Seen in flight control system discussions, especially elevator design, pitch stability, and aft center of gravity conditions.
Why Pilots Care
It restores positive elevator control and prevents unwanted nose-up pitch when the center of gravity is too far aft.
Grounding Statement
Picture a spring gently pulling the elevator control system toward a nose-lowering direction, so the airplane has added help keeping the nose from staying too high.
Intuition Check
Do not read down spring as a spring located underneath something. Here, down means the spring biases the elevator control system toward a nose-down effect.
Example Sentence 1
Because the airplane was loaded near its aft CG limit, the elevator down spring provided the extra nose-down force needed to keep pitch stable in cruise.
Example Sentence 2
During preflight, the mechanic verified that the down spring tension remained within limits.