In what scenario is visual separation typically not recommended?

Visual separation is typically not recommended in conditions where visibility is compromised, which aligns with the scenario involving adverse weather conditions. In adverse weather, such as heavy rain, fog, or storms, pilots may have difficulty seeing other aircraft or ground features clearly. This lack of visibility can lead to a greater risk of collision, as aircraft may not be able to visually maintain separation from one another. Therefore, relying on visual separation becomes unsafe in these scenarios, necessitating alternative means of separation, such as radar or procedural separation by air traffic control.

In contrast, other scenarios, while potentially hazardous, do involve conditions where visual separation may still be feasible or applicable with proper situational awareness and operational procedures. For instance, aircraft on glide paths may still maintain visual contact depending on the environment, and controllers might be able to implement visual separation if they have sufficient information and confidence about the aircraft's altitude and positioning. Similarly, simultaneous departures can be managed with visual separation when visibility allows for pilots to see and avoid other departing aircraft.