How far should aircraft be separated from the edge of airspace where radar separation is NOT being applied when they are less than 40 miles from the radar antenna?

When determining the separation required for aircraft operating near the edge of airspace where radar separation is not being applied, the correct distance is three miles. This separation is crucial to ensure safety and prevent any potential conflicts between aircraft that may be navigating in close proximity to the boundaries of radar coverage.

The reasoning behind the three-mile separation distance is based on both safety standards and the reduced accuracy of radar data as aircraft approach the edge of the coverage area. Effective separation minimizes the risk of incursions or misidentification of aircraft positions within airspace that lacks the benefit of radar monitoring.

In scenarios where radar separation is applied, the requirements can differ, but when radar is not in use, maintaining this specific three-mile buffer is essential for safe operations. Ensuring adequate separation helps in managing air traffic flow and allows for safe transitions into and out of radar-controlled airspace, keeping both pilots and air traffic controllers informed about aircraft positions.