Air Speed

 

The different colored arcs and lines represent various important airspeeds:

White Arc (V_SO to V_FE): This is the flap operating range, where it is safe to use the aircraft's flaps. The lower limit of the white arc (V_SO) is the stalling speed or minimum steady flight speed in the landing configuration. The upper limit (V_FE) is the maximum speed with the flaps extended.

Green Arc (V_S1 to V_NO): This is the normal operating range of the aircraft. The lower limit of the green arc (V_S1) is the stalling speed or minimum steady flight speed obtained in a specified configuration. The upper limit (V_NO) is the maximum structural cruising speed, beyond which you may encounter turbulence that could lead to structural damage.

Yellow Arc (V_NO to V_NE): This range is for operations in smooth air, and caution should be exercised. Flying in this range should be avoided unless the air is smooth, and speed should not exceed the boundary indicated by the red radial line (V_NE).

Red Line (V_NE): This indicates the never-exceed speed, which is the maximum speed the aircraft should not exceed under any circumstances. Exceeding this speed is likely to cause structural damage or failure.

These indicators help the pilot operate the aircraft within safe speed parameters to avoid stalls, structural damage, or loss of control.