What does Vs stand for in aviation terms?

• A. Stall Speed
• B. Velocity stability
• C. Vertical speed
• D. Viscosity

Answer: (A)

Vs stands for stall speed. It is the minimum steady airspeed at which an aircraft can maintain level flight with a given configuration. If airspeed drops to Vs, the wing reaches its critical angle of attack and loses lift, causing the airplane to stall and descend unless the speed is increased or the angle of attack reduced. The exact Vs value depends on weight, configuration (such as flaps and gear), and air density with altitude, and different Vs values can be specified for different configurations. It’s usually expressed as indicated airspeed (KIAS) because airspeed indicators measure dynamic pressure. This concept is different from vertical speed, which is the rate of climb or descent, and from viscosity, a fluid property; and velocity stability isn’t a standard term for this context.