[Ref ACE The Technical Pilot Interview 43/348]

Runaway Stabilizer happens when the stabilizer does not stop at the required point. It indicates by unusual rotation of the stabilizer to its maximum upward or downward mechanical stops, thereby inducing a marked out-of-trim unstable condition.

Each aircraft type should has its own drill, but in general :

1. Autopilot (if engaged), disengage
2. Stab trim cutout switches to cut out

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