Soryu & Ship Collide Feb 8-9, 2021 - Best see Jive's Video

Visible accidents are very rare in the Japanese Submarine Service. There has been a veritable avalanche of information and comments about the February 8/9, 2021 collision between:

-  the 3,000 ton Japanese Soryu submarine, specifically first-of-class "Soryu" (SS-501)

-  with the 51,000 ton bulk carrier ship Ocean Artemis. 

1.  Perhaps the most useful written report, so far, is The Drive's “Veteran Submariners Explain What Might Have Caused Japanese Submarine Collision” of February 9, 2021. The report poses various combinations of:

- submarine hit from behind by the ship or hit side-on by the ship [Pete comment: either way a very slow to change course ship generally has the right of way. This is because the sub ascends into danger - like a pedestrian stepping into traffic.]
- the sub being below periscope depth, at periscope depth or surfaced
- in a position of poor coverage by the sub's sonars or inadequately monitored/interpreted sonars and/or the periscope
- the sub was in relatively shallow/continental shelf waters which can confuse sonar returns.

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2.  Anonymous has identified sankei.com's article "Mistake in manoeuvring due to lack of crew training in inspection or accident of JMSDF submarine "Soryu"" of February 10, 2021. In that article an anonymous Japanese government official (once translated) suggests:

- the sub may have made a mistake in manoeuvring due to insufficient training of the crew 
- the sub was involved in working-up training after a prolonged period of "inspections" [and Pete would guess maintenance/overhaul] prior to returning to full operations
- the Japanese Navy will be confirming this training status and "whether the prescribed ship manoeuvring methods were thoroughly implemented".
- the sub is in the port of Kochi [which seems to be first available port for safety rather than a regular Japanese Naval Base?] 
- a ship accident investigator of the Japan Transport Safety Board began an official investigation, at Kobi, on January 10.

[Pete's further translation of the translation] "According to the Ministry of Defense, the sub seems to have hit Ocean Artemis when the sub ascended towards the surface. The sub's sonar team and/or equipment could not recognize Ocean Artemis. As the sub ascended it raised its periscope to look around. Inadequate training of crew members prior to returning to duty may have led to sonar's lack of surveillance of surrounding vessels and incorrect ascent procedures, government officials said."
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JIVE'S VIDEO

3. Jive Turkey's Sub Brief video, uploaded Feb 10, 2021, here and below is very informative:

1:20 - the sub ascended in a very busy shipping lane area. [perhaps not a good working-up training area?]

1:50 - had to surface in that area before getting into overly shallow water [as shallows bad for sonar use and dangerous to stay submerged as you may hit seafloor] 

3:20 - [Pete thinks the sub possibly ascended too quickly and/or too late (got into shallows too late/quickly) for sonar teams' assessments to keep up]

6:35 - did sub do a sufficient number of well timed baffle clears (turn arounds for the sonar team)?

6:45 - a shallow thermal (colder or warmer) water layer obscured the sonar signals given by oncoming Ocean Artemis [Pete reckons: an experienced sonar crew and officers should have anticipated this - if they knew the sea conditions in the area at a professional standard. But were there freak thermal conditions that day?] 

7:55 - But at the time of day in southern Japan Winter time [shallow eg. 10m] Jive says thermal layer differences/effects are minimal. Thermal layer is at more likely 65m at that time in Winter. But official investigations should show if there were unusual thermal layer conditions that day.

9:00 - If assuming hit from side ["side-swiped"] by ship. Sub, at periscope depth, couldn't dive fast enough [could an adequately trained crew have dived faster than the crew that was still at "working-up" re-training stage?]

9:45 - discussion of damage on sail, sail-planes, crew injury, how much repair and how long would it take, unusually shallow thermal layer? unusual currents/speeds.

11:50 - Jive thinks main factors were:

=  the sub took too long to get to periscope depth to get out of the way [again a training standard issue]

 and

=  there could have been a very strong [and shallow] thermal layer but Jive doesn't think so.

12:10 - So Jive concludes "Sonar was at fault."

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Pete's Predictions

1. Soryu's Captain (maybe a Commander or Lieutenant Commander) will be effectively sacked. The Japanese Navy may call it "moved to other duties" but he knows his career in the submarine service and Navy more broadly are at an end. No way would a defense "Captain was off shift, asleep" would be acceptable.

2. Responsibility often goes up the chain to the "Captain's" boss, ie. the Submarine Squadron Commander may be asked to retire. 

3. If an Officer-of-the-Watch was in the Command Center his future submarine career would be in doubt.

4. Of the usual team of 2 or 3 sonar operators on shift the more senior (Petty Officer) may be shifted to other (non-submarine) duties.