Two black balls
A vessel not under command. Advanced level, about 4 min. COLREGs Rules 18 & 27.
The situation
You are under power, heading north. On your port bow, Orion has lost her engine and is barely making way; she shows two black balls in a vertical line. Tern, a sailing vessel, is crossing from your starboard side towards Orion.
What do you do?
- Slow right down and let Tern cross ahead: Keep clear of both while Tern keeps clear of Orion.
- Hold on: Tern must deal with Orion: Keep your course and speed.
- Turn to port, between them: Open the distance from Tern.
Lookout: Two black balls in a vertical line mark a vessel not under command. Everybody else keeps out of her way, including sailing vessels.
Each vessel’s duty
Orion: None to give way: the others keep clear of her
A vessel not under command cannot keep out of anyone’s way, so Rule 18 puts every other vessel here under the duty to keep clear of her. She still keeps a lookout and signals.
Tern: Keep out of Orion’s way, stand on for you
Rule 18(b): a sailing vessel keeps out of the way of a vessel not under command. Towards you, a power-driven vessel, Tern is the stand-on vessel.
Your sound action
Slow right down and let Tern cross ahead
You keep out of the way of both. Tern turns to starboard to clear Orion, crossing your bow as she does; slowing right down lets her go and keeps you well away from the drifting Orion.
Why the other options fall short
Hold on: Tern must deal with Orion
Tern’s duty towards Orion does not lift yours towards Tern. You are the give-way vessel towards both a sailing vessel and a vessel not under command.
Turn to port, between them
Turning to port heads you towards Orion, who cannot get out of your way. Leave a vessel not under command a wide berth.
Rules 18 & 27 · Not under command
A vessel not under command shows two black balls by day (two all-round red lights by night). Power-driven and sailing vessels keep out of her way.