Listen for the manoeuvre
Sound identification. Foundation level, about 2 min. COLREGs Rule 34(a).
The situation
Two power-driven vessels are in sight of one another. The other vessel sounds a manoeuvring signal. Play the sound, then identify its meaning under the International Rules.
What does the sounded signal mean?
- “I am altering course to starboard”: One short blast.
- “I am altering course to port”: Two short blasts would indicate this.
- “I am operating astern propulsion”: Three short blasts would indicate this.
Lookout: Listen to the number and length of the blasts. This is an International manoeuvring signal, not an Inland passing proposal.
The sound answer
“I am altering course to starboard”
Under International Rule 34(a), one short blast signals “I am altering my course to starboard.” It announces an action; keep observing the vessel’s movement.
Why the other options fall short
“I am altering course to port”
A port course alteration is indicated by two short blasts under International Rule 34(a). The authored signal here contains one short blast.
“I am operating astern propulsion”
Operating astern propulsion is indicated by three short blasts under International Rule 34(a). It is not the same as being stopped or moving astern.
Rule 34(a) · Manoeuvring signals
When vessels are in sight of one another, a power-driven vessel underway indicates a starboard course alteration with one short blast, a port alteration with two, and astern propulsion with three.