What does COLREGS have to say about vessels using dynamic positioning systems (DPS) to hold station? Especially one not engaged in some other work
(most DPS vessels I have encountered are engaged in other work
that probably qualifies them as "restricted in ability to maneuver").
This question arises out of sharing an anchorage for the past 24 hours with a 116m superyacht that is not anchored, but rather is holding station in the bay with DPS. The COLREGS definitions (AFAIK) don't include a definition for "at anchor" but do define "underway" as "not at anchor
of this particular vessel has determined, since he has no anchor
down, that he is underway. His AIS
indicates his status as "underway" with a speed of zero. His lights are two masthead lights (one foreward, one aft and higher), sidelights, and a stern light - also indicating that his status is underway (by contrast, his 21m "tender" is anchored nearby and displays an all-around white light, pretty sure the DPS captain
is very clear on his decisions). But, he is staying in one place. In a crowded harbor.
As a crossing vessel should I expect him to give way if I am the stand on vessel? Doesn't seem reasonable to me, but how does that flow with the rules? And I'd guess that regardless of COLREGS definitions the give-way vessel at zero speed with only the DPS operational is indeed "restricted". If I'm crossing them at 8 or 10 knots with risk of collision
I doubt she is capable of getting out of the way in time to avert the collision
. Should the captain instead be showing his status as restricted? Or does he not meet a definition? How do I, as the stand on vessel, recognize DPS (that is holding station)? With AIS
I can see the zero speed, but without it it is much harder to confirm zero movement based on bearings (yes, it can be done, but from the deck
of a small moving vessel it can take some time).
This is also interesting with regard to anchored boats, the DPS vessel has not moved since we arrived. At all. Every anchored boat
here averages a 360 about once an hour (lots of current
eddies). So, the DPS vessel actually mucks up the anchorage a bit by not swinging like everyone else. In fact, with the DPS holding position they are closer to "aground" than "anchored." A 45m sailing vessel came in after Mr. DPS and anchored nearby (the only part of the bay deep enough for those vessels). Later they moved as in swinging they were too close to DPS. This would be common etiquette for anchored vessels, the later anchored boat
moves if their selection of spot causes a problem. But if the later boat is anchored and the other boat is "underway" does this apply? Or should the "underway" vessel be the one that moves?
Lastly, what about whistle signals? Given that her heading hasn't changed a degree since we came in I'm pretty sure her captain could say he is not altering course to port or starboard. But what about "operating astern propulsion"? I'd guess that there have been numerous times that has happened with the DPS holding position. And just as "underway" doesn't include anything about "making way", "operating astern propulsion" doesn't say anything about going backwards, just that the vessel has engaged astern propulsion
. Maybe the vessel is not "maneuvering as authorized or required" by COLREGS and so is not compelled to whistle?
Just curious how the COLREGS scholars interpret the rules with regard to a DPS vessel holding station? Maybe we have to fall back on Rule
2 until DPS is addressed directly?