Parallel ILS approaches can allow simultaneous approaches under which separation condition?

• A. None of the above
• B. Final radar monitoring in use
• C. 4300 ft separation
• D. Final monitor controllers in use

Answer: (C)

The key idea is lateral separation between the final approach paths for parallel ILS approaches. When the runways are 4,300 feet apart or more, the two ILS final approaches can be conducted simultaneously as independent approaches. That distance keeps each aircraft in its own protected airspace and prevents interference between the two localizer signals, so both aircraft can descend on their respective courses without risking conflict.

If the runways are closer than that, additional ATC measures would be needed to maintain safe separation, such as enhanced radar monitoring or other controller procedures, rather than relying on the inherent separation of the 4,300-foot spacing.