Definition
The stalling speed, or minimum steady flight speed, at which the airplane is controllable in the landing configuration — typically with full flaps extended, landing gear down, and power at idle. VS0 marks the lower end of the white arc on the airspeed indicator.
Plain English
The slowest speed at which the airplane can still fly in a controlled way when it is set up to land — flaps fully out, gear down, and power at idle. Below this speed, the wing stops producing enough lift and the airplane stalls.
Context Anchor
Seen in aircraft speed markings, performance data, and discussions of landing stalls and landing configuration.
Derivation
The 'V' comes from the French 'vitesse,' meaning speed. Aviation uses 'V-speeds' as standard shorthand for specific speeds that matter for flight performance and limitations. The 'S' stands for stall, and the '0' (zero) indicates the landing configuration — flaps fully extended, as opposed to a clean configuration.
Why Pilots Care
Pilots use this speed to set safe approach speeds and confirm the airplane can land without stalling.
Intuition Check
Do not read VS0 as “speed equals zero.” It is a named V-speed symbol for stall speed in the landing setup.
Example Sentence 1
The bottom of the white arc on the airspeed indicator marks VS0 — the stall speed with flaps and gear extended.
Example Sentence 2
On final approach the airplane was flown at 1.3 times VS0 to maintain a safe margin above stall.