Rules of the Road · Maneuvering & Warning Signals
Three short blasts on a whistle, under Rule 34, signals which of the following?
- AI am altering course to starboard
- BI am altering course to port
- CI am operating astern propulsion✓ Correct
- DI am in doubt — danger
Explanation
Rule 34(a)(iii) states three short blasts mean 'I am operating astern propulsion.' This does not necessarily mean the vessel is moving astern — it means engines are in astern (backing). It applies only when vessels are in sight of each other.
Authority: 72 COLREGS Rule 34(a)(iii)
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