What is the purpose of a stall warning or stick shaker, and what does it indicate?

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The main idea here is that stall warning systems and stick shakers are protection tools that alert you to a dangerous flight condition—an airfoil approaching its critical angle of attack. When the wing reaches this high angle, the airflow can separate and lift begins to drop. The sensors monitor angle of attack and trigger a warning before a full stall develops. The stick shaker adds a tactile cue, shaking the control column to demand your attention and prompt immediate action.

What this indicates is that at the current airspeed, weight, configuration, and load factor, the wing is near or at the point where lift will start to decrease rapidly unless you respond. The proper response is typically to reduce angle of attack and/or increase airspeed to restore smooth, attached flow over the wing. This warning is not about engine failure, gear, or fuel status; those are indicated by separate systems.