Question 44
ONC03BOTH INTERNATIONAL & INLAND Two power-driven vessels are crossing as shown in illustration D042RR below. Vessel "A" sounds three short blasts on the whistle. What is the meaning of this signal?

AI Explanation
The Correct Answer is D
**Explanation for Option D (Correct Answer):**
According to both the International Regulations for Preventing Collisions at Sea (COLREGS, Rule 34) and the Inland Rules, a power-driven vessel using her whistle to indicate maneuvers must follow specific signals. The signal consisting of **three short blasts** (short blast defined as about one second duration) signifies that the vessel is **operating astern propulsion** (backing engines). This means Vessel "A" is either slowing down by reversing its engine or actively moving backward.
**Explanation of Incorrect Options:**
* **A) Vessel "A" intends to hold course and speed:** This action does not require a whistle signal in a crossing situation under the general maneuvering rules, but if a signal were given to indicate intention, a single prolonged blast (or no signal, depending on context) might be relevant, not three short blasts. Furthermore, three short blasts indicate a change in propulsion/speed.
* **B) Vessel "A" is sounding a signal of doubt:** A signal of doubt, or the danger signal, consists of **at least five short blasts** given rapidly. Three short blasts have a specific maneuvering meaning.
* **C) Vessel "A" proposes to cross ahead of the other vessel:** A vessel proposing to cross ahead in an internationally regulated narrow channel or fairway (or generally indicating a starboard-to-starboard passing in Inland Waters) would use **two prolonged blasts followed by one short blast** (or standard passing signals of one or two short blasts depending on the situation/rules). Three short blasts specifically indicate reversing engines.