Keeping the blogosphere posted on the goings on of the world of submarines since late 2004... and mocking and belittling general foolishness wherever it may be found. Idaho's first and foremost submarine blog. (If you don't like something on this blog, please E-mail me; don't call me at home.)

Wednesday, September 28, 2005

Philly Investigation Continues

An article in The Day discusses the continuing investigation into how the collision between USS Philadelphia and M/V Yaso Aysen happened, and who was at "fault". (I hypothesized about this in great detail last week):

"Who's to blame — more importantly, who will pay for the damage to the freighter — could come down to a matter of a few degrees.
"If the M/V Yaso Aysen was within a conical area 135 degrees wide behind the submarine, it was overtaking the Philadelphia, and was at fault.
"But if investigators find the Aysen was forward of that area, under maritime law they were crossing, and the Philadelphia would be held responsible. Under maritime law when two vessels are crossing paths, the ship to the left, or port, must yield to the ship on the right, or starboard.
"The issue is complicated by the fact the Philadelphia maneuvered to avoid the collision, so the angle at which they hit was not the angle of the approach, Navy sources said."

It seems it shouldn't be too hard to reconstruct. They'll have the Philly's deck log, and should have the bearings from the periscope observations, which should allow them to figure out the merchant's course fairly accurately -- after all, they have a really good idea what the CPA was (zero). If they got blade rate at all from sonar, or have good radar data, they will have the merchant's speed, and that will be the last piece of the TMA puzzle in figuring out what Yaso Aysen's course was.

Staying at PD...

Update 2303 28 Sep: Longer-lasting version of the article is here, 2nd article down.


Blogger PigBoatSailor said...

Hey, didn't we mention all of those points. You hit all of them in your original post, and there was even more depth in the comments. You should write for The Day ;-)

9/28/2005 9:45 AM

Blogger MT1(SS) said...

He probably does and just doesn't want anyone to know ;-)

9/28/2005 10:57 PM

Blogger geezernuke said...

The "being entangled for more than an hour" aspect adds a new component to the puzzle. It would seem that this means the relative velocity must have been pretty low. Could it be that the M/V Yaso Aysen was attempting to take her way off with a back bell prior to the collision, which complicates steering to say the least. Couple that with a previous commentor suggestion that "Philly" might have reacted with a right rudder order and I can visualize the "O SH##".
Did any of the previous data indicate whether M/V Yaso Aysen was single or twin screwed? Single I'd bet which is the basis for my thought about steering complications (having driven a single screw AS).

9/29/2005 7:24 AM

Blogger PigBoatSailor said...


They were likely entangled for that long because they are not supposed to pull apart until they are certain that doing so will not expose a hull breach and potentially sink one or the other vessel. Howver, by the time they actually hit, I would agree the overall relative velocity was probably rather low - the damage looks nothing like what the OKC suffered (although she took the brunt of her collision in her sail, not her hull).

9/29/2005 8:08 AM


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