Definition
VS1 is the stalling speed or minimum steady flight speed obtained in a specific configuration, typically with flaps retracted and the airplane in a clean (cruise) configuration. It represents the slowest speed at which the airplane can maintain controlled, level flight before the wing stalls in that configuration.
Plain English
The slowest speed the airplane can fly without stalling when it is in a specified clean configuration — usually meaning flaps and landing gear up.
Context Anchor
Seen in airplane handbooks, performance charts, and airspeed discussions when comparing safe operating speeds for a given airplane setup.
Derivation
The 'V' comes from the French vitesse, meaning 'speed.' The 'S' stands for 'stall.' The '1' indicates a specific configuration — distinguishing it from VS0, which refers to the stalling speed in the landing configuration.
Why Pilots Care
Knowing VS1 helps pilots select safe speeds for maneuvers and avoid stall during normal flight operations.
Intuition Check
VS1 is not a speed to aim for in normal flying. It is a boundary speed that tells you where the airplane is getting too slow for that configuration.
Example Sentence 1
The pilot noted that VS1 for the airplane was 52 knots, which matched the bottom of the green arc on the airspeed indicator.
Example Sentence 2
During preflight planning, the instructor noted that VS1 was 48 knots for the training airplane.