What does a black "C" indicate on a circling approach chart?

A black "C" on a circling approach chart indicates expanded circling minimums. This notation provides pilots with information about the minimum altitudes and visibility requirements necessary when conducting a circling approach at an airport. Expanded circling minimums are typically employed in situations where the configuration of surrounding terrain or obstacles necessitates a higher minimum than standard circling minimums. These extended requirements ensure that pilots can safely maneuver during the approach phase, particularly in challenging environments where visibility may be limited or where terrain may pose an obstacle.

Understanding this notation is critical for pilots as it directly impacts their approach strategy and decision-making. By adhering to the expanded circling minimums, pilots enhance safety by accounting for additional vertical and horizontal margins, ensuring sufficient clearance from obstacles in the vicinity of the airport.