On a REIL three-setting system, Setting 2 must be used during the day when the visibility is ______.

• A. Less Than 1 Mile
• B. 2 To 5 Miles Inclusive
• C. 1 Up To But Not Including 3 Miles
• D. Greater Than 5 Miles

Answer: (B)

The idea behind the three-setting REIL system is to adjust the intensity of the runway end identifier lights so they are conspicuous in different daylight visibility ranges. In daylight, you pick a mid-level setting when the visibility is in the 2 to 5 miles range, so the lights stand out enough to be identified from typical approach distances without being excessively bright in clearer conditions. That’s why 2 to 5 miles inclusive is the correct choice. If visibility were outside that window, a different setting would be used to suit the shorter or longer detection range, which is why the other options don’t fit this particular daylight scenario.