Rule 31: seaplanes and WIG craft.

What does COLREGs Rule 31 say?

If a seaplane or a WIG craft cannot carry the Part C lights and shapes with the colours, arcs and other characteristics, or in the positions, those rules set, she still shows lights and shapes, as near to them as she can: 'as closely similar in characteristics and position as is possible'.

It is a fallback, not a separate set of lights. The starting point is whatever the rest of Part C requires of her; Rule 31 applies only where meeting it exactly is impracticable. And despite the title, it covers WIG craft as well as seaplanes.

When does a seaplane have to show them?

As for any vessel, under Rule 20: the rules on lights apply from sunset to sunrise, and lights carried are also shown from sunrise to sunset in restricted visibility; the rules on shapes apply by day. Rule 31 changes what she shows, not when.

What is a seaplane, and is it a vessel?

Rule 3(e): 'seaplane' includes any aircraft designed to manoeuvre on the water. Rule 3(a) includes seaplanes and WIG craft in the word 'vessel', so where the rules speak of vessels, they include them.

A WIG (Wing-in-Ground) craft, Rule 3(m), is a 'multimodal craft' whose main operational mode is flight just above the surface, held up by surface effect.

What lights does a seaplane show on the water?

Rule 31 does not list any: it points back to the rest of Part C. As we read it, a seaplane taxiing on the water is propelled by machinery, which makes her a power-driven vessel under Rule 3(b), so the Rule 23 lights — masthead light, sidelights and sternlight — are the ones she aims to show, as closely as her shape allows. At anchor, the starting point is the Rule 30 anchor light or lights, again as closely as she can.

What extra light does a WIG craft show?

Rule 23(c): a WIG craft, only when taking off, landing and in flight near the surface, shows a high intensity all-round flashing red light in addition to the Rule 23(a) lights of a power-driven vessel. Rule 31 covers her where those lights cannot be carried with the prescribed characteristics or in the prescribed positions.

Why would the normal lights be impracticable?

In practice, an aircraft is not built around the positioning rules of Annex I. Wings, floats and a fuselage with no mast can make the prescribed heights, spacings and arcs of visibility impossible to achieve. Rule 31 accepts that and asks for the nearest equivalent — not for nothing.

Who keeps out of whose way — a seaplane or a vessel?

Rule 31 is about lights; conduct is in Rule 18. Under Rule 18(e), a seaplane on the water must, in general, stay well clear of other vessels and not get in their way. Once risk of collision exists, though, the Part B rules apply to her like anyone else.

Rule 18(f) treats a WIG craft by phase. While taking off, landing or flying near the surface, she must stay well clear of every other vessel and not get in the way of their navigation. Once she is operating on the water surface, the Part B rules apply to her as they would to a power-driven vessel.

How might Rule 31 come up in an MCA oral?

It may come up as a follow-up to Rule 18 or Rule 23. Examples of the kind of question to be ready for:

“What does Rule 31 require if a seaplane cannot carry the normal lights?”

“A seaplane is taxiing on the water and risk of collision develops with you. Which rules apply to her?”

“What extra light does a WIG craft show, and when?”

“On the water surface, how is a WIG craft treated under the steering rules?”

Where do candidates go wrong on Rule 31?

The common slips: thinking Rule 31 gives seaplanes lights of their own; forgetting that it covers WIG craft too; treating it as an exemption, when it asks for lights and shapes as close as possible rather than none; and mixing up Rule 31, which is about lights, with Rule 18(e) and (f), which are about conduct.