VS1

VS1 is the minimum steady flight speed that can be achieved by an aircraft in a specified configuration. This speed is typically determined by conducting power-off stall speed tests at maximum takeoff weight in a clean configuration, which means that the aircraft’s gear is up (if retractable) and flaps are up. VS1 is important because it represents the speed below which the aircraft cannot maintain level flight and is therefore the lower limit of the green arc on the airspeed indicator. In other words, if an aircraft flies at or below its VS1, it is at risk of stalling and losing control. Hence, it is a critical value that pilots must be aware of and capable of avoiding during flight.