Question 1

Under Rule 21, what is the defined arc of visibility for a "sidelight" (red on port, green on starboard)?

Accepted Answer

An arc of the horizon of 112.5°, fixed so as to show the light from straight ahead to 22.5° behind the beam on its respective side The 112.5° arc for sidelights (from dead ahead to 22.5° aft of the beam on each side) is designed so that an observer can determine a vessel's approximate aspect/heading by which light(s) are visible — central to interpreting many close-quarters situations at night.

Question 2

Rule 5 (Look-out) requires every vessel at all times to maintain a proper look-out by sight and hearing, as well as by all available means appropriate in the prevailing circumstances and conditions — and this duty applies even when the vessel is at anchor in a busy anchorage.

Accepted Answer

True True. Rule 5 applies 'at all times' and to 'every vessel'. A vessel at anchor in a busy anchorage still needs an effective look-out to detect drifting vessels, dragging anchors, or approaching traffic that may pose a risk of collision or contact.

Question 3

Under Rule 6 (Safe Speed), a vessel fitted with a fully operational radar and ARPA never needs to reduce speed in restricted visibility, because the equipment guarantees early detection of other vessels.

Accepted Answer

False False. Rule 6 explicitly lists radar capability as one factor to consider, but also requires accounting for the state of visibility, traffic density, manoeuvrability, and the limitations of radar (range scale, sea/rain clutter, blind sectors). Even a vessel with excellent radar must proceed at a speed that allows proper and effective action to avoid collision and to be stopped within a distance appropriate to the prevailing circumstances.