Operate Sequenced Flashing Lights (SFL) when the visibility is less than ______ mile(s).

• A. 1
• B. 2
• C. 3
• D. 4

Answer: (C)

Sequenced Flashing Lights are an enhancement to the approach lighting that helps pilots identify the runway environment when visibility is reduced. They are activated when visibility falls below three miles. The extra flashing sequence provides a clearer cue to runway alignment and distance, making it easier for pilots to stack up the correct approach path and continue the landing in marginal weather. If visibility is three miles or more, these lights aren’t required because the standard lighting already provides sufficient guidance. So, in conditions with less than three miles of visibility, turning on the SFL gives pilots a valuable additional reference as they approach.