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nolatom

Front page--tanker SANCHI collision, fire, sinking, AIS issue?

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After this awful collision, I had wondered why no one had posted the vessel tracklines into collision, since AIS transmits that info to other traffic, as well as to commercial vessel tracking services (e.g. Marine Traffic).

Finally, an article from WSJ pointing out this was an area of spotty or missing AIS coverage.  One maritime observer thinks the absence of transponder data could (if transponders turned off rather than coverage problems) indicate something fishy was up with (both?) ships:

http://maritimebulletin.net/2018/01/14/sanchi-tragedy-wsj-searching-for-something-hot-and-fishy/

I doubt it, these were two ships evidently still underway on open-sea voyages north (Sanchi approaching S. Korea from Iran) and west (Crystal heading toward China with grain from  US west coast).  Which (along with Sanchi listing heavily starboard and Crystal's damage on her port bow) indicates a crossing situation, with Crystal on the right.  Lack of AIS (if true) would mean no vessel name on your E-chart or radar overlay.   Okay, that puts them back into the technology of the 1990s, meaning radar (with automatic target plotting, if you use it) and visual lookout.  

What went wrong?   We will only hear from one side, since Sanchi, and most regrettably  her crew, are both gone.  Crystal's Voyage Data Recorder will probably fill in the details, as it would record the radar screen.

Are there areas we know of in our sailing lives where AIS is unavailable or unreceivable?  This sounds strange.

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Ais tracking  is a terrestrial, coastal system  system .  

Satellite ais tracking is rather new and has some areas that are not well covered bythe satellites footprint 

perhaps this area is not well covered 

IMG_7854.PNG

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I think you're clear on the concept - but don't confuse satellites picking up AIS signals (useful for those at the home office) with ship's AIS that talk to each other.

In our circumnavigation we only passed 2 big ships underway, that had AIS turned off. I think big ships realize it is a very valuable tool for collision avoidance.

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Ais is radio..ship to ship collision avoidance 

ais tracking is  ship traffic monitoring by martime authorities

not to long ago when you sailed out of radio range you dropped off the edge of Ais  tracking earth.

i dont know the capabilities of satellite ais tracking..it is not real time..

 

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If we are to believe the Iranian Students' News Agency (!), both VDR boxes have been recovered, and are being analysed by, uh, not sure who, but would certainly include the flag states and probably nearby port/coastal states, plus ships' owners and underwriters.

https://www.reuters.com/article/us-china-shipping-accident/black-box-for-sunken-tanker-sanchi-opened-iranian-media-idUSKBN1FD0SX

While the article says it "could take months", the VDR from CRYSTAL should be easily played on a computer with the proper software.  Same with the box from SANCHI, though it could possibly be damaged by fire and water.  Crystal's box alone would tell most of the story, since it would have Crystal's radar recorded, showing the contact and movement of both ships, as well as VHF transmissions to or from both vessels, engine and helm orders, heading and rate of turn on Crystal.. 

8pm on what seems to have been a clear night.  Sanchi seems to have been holed on starboard side, just aft of midships, reportedly 35-meter triangle shape.  And Crystal has strong impact damage to her port bow above the waterline, and likely same angle on her bulbous bow much deeper down, with both ships being loaded at the time.   

Was it a crossing, with Sanchi being give-way?  Or reciprocal headings, and Sanchi went to port while Crystal turned starboard, in a deadly "gull-wing" pattern?  How'd it come to that, didn't they see each other earlier?  Forget AIS for the sake of argument, just radar plus a guard-ring alarm set, would seem to give plenty of warning.  As would an ARPA plot done by either vessel, to get an instant CPA/TCPA on a detected target.  

These are academic questions for the present.  Eventually we will have the information which is being kept seemingly quiet until someone discloses it.

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It is also possible to have  a language problem,  then perform the wrong  crossing maneuver 

vhf log or a witness can clarify 

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1 hour ago, TonyFromSheepsheadBay said:

Wouldn't be the first time a ship carrying Iranian crude was in stealth mode. Just sayin. 

Are you suggesting it was going to N Korea?

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