When can visual separation not be applied?

Visual separation is a technique used by air traffic controllers to maintain safe distances between aircraft when the pilots can see each other. This method is based on the assumption that pilots can visually identify and maintain separation from other aircraft.

When determining the proper context for applying visual separation, it is crucial to recognize the limitations and guidelines associated with altitude. Specifically, visual separation cannot be effectively used when aircraft are operating at flight levels exceeding FL180, as pilots may no longer be able to see each other due to the increased altitude and potential over-the-horizon limitations. At these higher altitudes, the effectiveness of visual references diminishes significantly, making other separation methods, such as lateral or vertical separation, necessary for maintaining safety.

Other situations, such as poor weather conditions or nighttime operations, do have specific challenges that might affect visual separation, but they do not outright prohibit its application. In some cases, visual separation may still be employed during night or in weather conditions if the required conditions for visual flight rules (VFR) are met. Therefore, understanding that visual separation is not applicable at higher altitudes offers crucial insight into specific operational limitations in air traffic control.