If a sailing vessel is also using propelling machinery, what lights must it exhibit?

A sailing vessel that is under power while also utilizing its sails is classified as a "sailing vessel using propelling machinery." To be compliant with the COLREGs, this vessel must exhibit specific lights to signal its status clearly to other vessels.

The requirement for exhibiting side, stern, and masthead lights ensures that the vessel is visible from all angles and provides the necessary information about its type and activity. The side lights, which are red for port and green for starboard, indicate the vessel’s direction and help other vessels determine the sailing vessel's orientation. The stern light, a white light located at the rear, shows that the vessel is moving and helps others understand its size and direction from behind. The masthead light, typically white and positioned higher up, indicates that the vessel is under power, further distinguishing it from purely sailing vessels.

This combination of lights serves a crucial role in navigation safety, ensuring that other vessels can easily identify the sailing vessel's capabilities and intentions, particularly during periods of low visibility. Thus, the requirement to display all specified lights signifies the vessel's hybrid nature, engaging both its sails and its machinery for propulsion.