Definition
Vs is the stalling speed or the minimum steady flight speed at which the airplane is controllable. It represents the slowest speed at which the wing can still produce enough lift to support the aircraft in steady flight before the airflow over the wing separates and the wing stalls. Vs is a general reference value; specific configurations have their own designators (Vso for landing configuration, Vs1 for a specified clean configuration).
Plain English
The slowest speed at which the airplane can still fly under control. Go any slower and the wing stops producing enough lift, and the airplane stalls.
Context Anchor
Seen on airspeed markings, performance charts, and angle-of-attack indicator illustrations when showing how close the airplane is to stall.
Derivation
The 'V' comes from the French 'vitesse,' meaning speed. The lowercase 's' stands for 'stall.' This 'V-speed' naming convention is used throughout aviation for standardized reference speeds.
Why Pilots Care
Knowing Vs helps pilots avoid stalls by maintaining safe margins above this speed.
Intuition Check
Do not treat Vs as one fixed speed for every situation. It changes with the airplane’s weight, flap setting, and how hard the airplane is turning or pulling.
Example Sentence 1
The instructor reminded the student that Vs increases in a steep turn because the wing must produce more lift to support the load.
Example Sentence 2
The angle of attack indicator showed the approach to Vs as the wing approached the critical angle.