Which lights are mandatory for a vessel recovering a helicopter at night?

When a vessel is recovering a helicopter at night, it is required to display three all-round lights in a specific order, along with sidelights and a sternlight. This lighting configuration is crucial for ensuring visibility and safety during helicopter recovery operations.

The use of three all-round lights—specifically, one white light at the center, and two other colored lights (usually red or green) at certain heights—provides a clear indication of the vessel's maneuvering capabilities and activities to other vessels in the vicinity. The specific order of the lights is important as it conveys the status and operations of the vessel effectively, signaling that it is engaged in helicopter recovery activities, which may involve unusual movements or specific hazards.

The requirement for sidelights (red and green) and a sternlight ensures that the vessel is properly lit in all directions, making it easily identifiable to approaching craft. This comprehensive lighting aids in preventing collisions and promoting safe navigation at night during such specialized operations.

In contrast, the other options do not meet the regulatory standards set forth for vessels engaged in these activities, as they either provide inadequate coverage or do not communicate the specific operational scenario effectively.