Definition
An audible cockpit warning device that sounds when the airplane's angle of attack approaches the critical (stalling) angle, alerting the pilot that a stall is imminent if the angle of attack continues to increase. It is typically activated by a sensor on the wing's leading edge, such as a vane or pressure-port lift detector, and gives a continuous tone or buzz several knots before the actual stall occurs.
Plain English
A horn in the cockpit that sounds a warning just before the wing stops producing enough lift to keep flying. It tells the pilot to lower the nose or add power before the airplane actually stalls.
Context Anchor
Heard in the cockpit during slow flight, stall practice, landing, and some multi-engine training demonstrations when the airplane is close to a stall.
Derivation
“Stall” originally means to stop or become stuck. In aviation, it does not mean the engine has stopped; it means the wing is no longer making lift normally. “Horn” means a sound-making warning device, so a stall warning horn is the sound device that warns about an approaching wing stall.
Why Pilots Care
Gives immediate notice to lower the nose and reduce angle of attack before loss of lift and control occurs.
Intuition Check
Do not assume “stall” means the engine quit. Here, “stall” means the wing is getting too close to losing smooth airflow and normal lift.
Example Sentence 1
As the airspeed bled off during the approach to landing, the stall warning horn began to chirp, prompting the pilot to add a small amount of power and lower the nose slightly.
Example Sentence 2
During slow flight the instructor asked the student to note how the stall warning horn activates well before a full stall develops.