Friday Puzzler – Radar, Navigation and Rules of the Road

The nav display showing AIS overlay on the radar and chartplotter.
The nav display showing AIS overlay on the radar and chartplotter.

Ed Note – A very special thanks to everyone who commented on the Facebook posts at the JWorld Annapolis Facebook page during my recent delivery from Annapolis to Amelia Island, Florida.  Randy Gray and Bill McGraw inspired the following post and puzzler, ripped from my notes from the trip.  Everyone who posts a comment will be eligible for a free J World t-shirt.  The drawing for the shirt will be Monday morning at 1100.  Leaving a comment is easy.  Just click comment at the bottom of the post and write away!

It was almost 0000 and the start of my fifth day out of Annapolis.  The rhythm of sea life had set in and my body was getting used to the four hours on four hours off tempo that my delivery mate and I had set.  I was aboard a 50′ catamaran that had sailed thousands of open ocean and Caribbean miles.  We were headed to Amelia Island, Florida where the boat would hang for the winter, possibly making a jaunt or two over to the Bahamas and back.

Due in part to our December departure we had seen very little traffic.  As I stepped onto the bridge deck to take my watch, the radar had two targets within four miles, both with intercepting course vectors and Bill was obviously hand steering – a rarity on this trip.

We were 30 miles east of the entrance to the river system that leads to Savannah, GA and as I zoomed out the screen the AIS showed that there were nearly a dozen fast moving freighters within 20 miles.  A busy night at the helm and radar scope.

Shortly after Bill slipped off watch a freighter leaving via the Savannah Traffic Separation Scheme showed up on a crossing situation.  It was an old friend.  The freighter had passed us in the Chesapeake nearly five days before – the Atlantic Impala – confirmed by radar and AIS was still more than 16 miles out, but her course and speed had our Closest Point of Approach (CPA) within a mile of one another.

While the night was clear and the sea state relatively calm, I could not see the Atlantic Impala.  But with radar I did start a record of the time, range, bearing and occasionally the CPA.  Our courses were at nearly right angles to one another and neither of us seemed interested in slowing down or altering course – I was sure he wasn’t.

Here is what I wrote in my notebook during the crossing:

Time Range Bearing CPA/Note
0050 11.82 289 1.16/ Atlantic Impala
0052 11.1 289
0053 10.8 289 1.26
0054 10.6 289 1.0
0056 9.9 290 38 mins to TCPA/attempted radio contact ch. 16/13
0058 9.4 290 Visual contact
0105 7.4 292 1.1
0106 7.1 293 .94
0108 6.6 293
0109 6.3 293 Radio Contact attempted Ch. 16/13
0115 4.9 297
0117 4.2 299
0118 3.9 300 .961/ 14 mins to TCPA
0119 3.6 301
0120 3.3 302 .991
0122 2.9 304 1.0
0123 2.8 305 Port Light Vis.
0124 2.4 309
0125 2.2 311 Both P & S Light Vis.

 

So… what do you think?  In an effort to save space I haven’t shared the entire situation (e.g. proximity of other vessels, shoals, etc.) Based upon the information available:

  1. According to the COLREGS who was the stand on vessel and who was the give way vessel?  Why?
  2. What was I required to do according to the COLREGS?  In the event that I was unsure or thought a collision was imminent, what was I required to do.  What was the Atlantic Impala required to do in this situation?
  3. What sound signals would I have offered the Atlantic Impala if we had been within range of one another?
  4. What sound signals would the Atlantic Impala have made if she didn’t understand my intentions or didn’t think, based on her information, that I was crossing?
  5. Did I do the right thing by holding my course based on the radar information available to me?
  6. What were some of my available options and when would you have exercised the option?

Comments

John
Reply

ASSUMING YOU DID NOT ALTER COURSE OR SPEED

1. According to the COLREGS who was the stand on vessel and who was the give way vessel? Why? IT’S NOT CLEAR FROM YOU NOTES IF YOU WERE SAILING OR MOTORING. IT’S NOT CLEAR FROM THE CHART PICTURE IF YOU ARE ACTUALLY CROSSING THE TRAFFIC SEPARATION SCHEME OR IF YOU ARE WELL BEYOND IT, ASSUMING YOU ARE CROSSING IT WERE YOU DOING SO AT A RIGHT ANGLE?…IF MOTORING AND IF ACTUALLY OUTSIDE THE TRAFFIC SEPARATION SCHEME OR CROSSING IT AT A RIGHT ANGLE, ATLANTIC IMPALA WAS THE STAND ON VESSEL. MOTOR DRIVEN VESSELS…THE VESSEL ON YOUR STARBOARD HAS THE RIGHT OF WAY.
2. What was I required to do according to the COLREGS? GIVEN WHAT OCCURRED, NOTHING In the event that I was unsure or thought a collision was imminent, what was I required to do. ALTER COURSE OR SPEED TO AVOID COLLISION What was the Atlantic Impala required to do in this situation? IF THEY THOUGHT A COLLISION WAS IMMINENT, THEN ALTER COURSE OR SPEED TO AVOID A COLLISION
3. What sound signals would I have offered the Atlantic Impala if we had been within range of one another? GIVEN WHAT OCCURRED…NONE. IF ALTERING COURSE TO STARBOARD 1 SHORT.
4. What sound signals would the Atlantic Impala have made if she didn’t understand my intentions or didn’t think, based on her information, that I was crossing? 5 SHORT
5. Did I do the right thing by holding my course based on the radar information available to me? PERHAPS YES, BUT IT APPEARS THAT EITHER YOUR CPA ESTIMATES WERE WRONG OR ATLANTIC IMPALA REDUCED SPEED TO AVOID CPA OF LESS THAN 2 MILES…IF ATLANTIC IMPALA REDUCED SPEED TO AVOID A CLOSE APPROACH THEN ‘NO’ YOU DID NOT TO THE RIGHT THING.
6. What were some of my available options and when would you have exercised the option? MADE A POSITIVE AND OBVIOUS ALTERATION OF COURSE TO STARBOARD TO PASS ASTERN OF ATLANTIC IMPALA, BEING SURE TO EXERCISE A SUFFICIENT COURSE CHANGE WITHIN AMPLE TIME SUCH THAT YOUR INTENTIONS WERE OBVIOUS TO THE ATLANTIC IMPALA.

Jeff Jordan
Reply

From personal experience the description you gave of the situation is the one that makes for fitful sleep. The one thing I would like to share with our local sailors is that this scenario happens more frequently right here on the Bay then it does offshore. Understanding what to do in these types of situations is imperative to understand, specifically at night. Avoid five blasts, never good news.

James R. Gray
Reply

1. According to the COLREGS who was the stand on vessel and who was the give way vessel? Why? Since this situation took place seaward of the “COLREGS Line” the International Rules apply. More information in needed to determine, in this situation, if the 50’ Catamaran (I’ll refer to as “KB’s Folly”) is the Stand On vessel. If KB’s Folly was under sail, she is the Stand On vessel based on Rule 18. If she was under power, she is the Give Way vessel based on Rule 15&18. This assumes that at no time did the Atlantic Impala give any indication that she was something other than a power driven vessel, either via a SECURITY call, or via their navigation light combination.
2. What was I required to do according to the COLREGS? See above, but if under sail, maintain course and speed. If under power, alter course to cross the Atlantic Impala astern. In the event that I was unsure or thought a collision was imminent, what was I required to do. Take way off (slow down) to a minimum control speed. This would either eliminate the crossing situation, or at least increase the time to assess the situation. What was the Atlantic Impala required to do in this situation? Either alter course to pass KB’s Folly astern, or maintain course and speed.
3. What sound signals would I have offered the Atlantic Impala if we had been within range of one another? Let’s assume that even if KB’s Folly was under sail, at some point she would engage her propulsion, to maximize her maneuvering options. In doing so, she would now want to alter course to starboard, to pass cross the Atlantic Impala’s stern. KB’s Folly would sound one short blast. Rule 34.
4. What sound signals would the Atlantic Impala have made if she didn’t understand my intentions or didn’t think, based on her information, that I was crossing? Five short and rapid blasts. Rule 34
5. Did I do the right thing by holding my course based on the radar information available to me? I would say yes. You were starting to see the bearing increasing between the Atlantic Impala and your vessel. The last range was about 1 NM, which for open water is close, but not dangerous. If you could have established radio communications, it would have probably made the situation safer for both vessels.
6. What were some of my available options and when would you have exercised the option? Continue to attempt to hail on the radio. The best option is to slow down. It buys time. In your case, crossing ahead, as soon as you commit to that, you could increase speed, and ensure that you are crossing perpendicular. But, the earlier you make a speed or course change, the smaller the change needs to be. This took place over a period of 35 minutes. A knot less speed, or 5 degree course change would have drastically altered the situation, if done 35 min in advance.

Jim
Reply

Best I can see from your data ——

I’d say AI is the stand-on vessel – either in or just exiting a Traffic Separation zone and approaching to your starboard. —– Also, size matters 🙂
j) A vessel of less than 20 meters in length or a sailing vessel shall not impede the safe passage of a power driven vessel following a traffic lane.
or When two power-driven vessels are crossing so as to involve risk of collision, the vessel which has the other on her own starboard side shall keep out of the way and shall, if the circumstances of the case admit, avoid crossing ahead of the other vessel. (You didn’t say if you were under sail or power)

but it appears you will safely pass him if you’re looking at his port & starboard lights and your bearing to AI is changing — and your range had begun to increase — no collision imminent.

If collision was imminent, you would be required to change course to avoid. In either case a long blast on the horn would be called for and/or raise the vessel by radio.

If changing course – make a significant change — I would alter sufficiently to go astern of AI if in doubt.

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