What is indicated by the lower limit of the green arc (Vs1) in aviation?

The lower limit of the green arc, designated as Vs1, represents the minimum steady flight speed in a specified configuration, particularly in a clean configuration (landing gear and flaps up). This speed is critical because it signifies the lowest velocity at which an aircraft can maintain controlled flight without stalling under the defined conditions. Maintaining airspeed above this limit ensures a safe margin above stall speed, thereby allowing for effective control of the aircraft during various phases of flight, especially during approaches and landings.

Understanding Vs1 is essential for pilots since flying below this speed compromises airworthiness and safety. The other options pertain to different aspects of aircraft performance and limitations, such as maximum structural cruising speed, caution ranges, and never-exceed speeds, but they do not relate to steady flight conditions as defined by Vs1.